Dependencies¶

If you choose to install the dependencies yourself, use the following command to check the required dependencies are present:

$ python setup.py checkdep

Writing¶

When creating files from a CIS command, CIS uses the NetCDF 4 classic format. Ungridded output files are always prefixed with cis-, and both ungridded and gridded output are always suffixed with .nc.

Reading¶

CIS has built-in support for NetCDF and HDF4 file formats. That said, most data requires some sort of pre-processing before being ready to be plotted or analysed (this could be scale factors or offsets needing to applied, or even just knowing what the dependencies between variables are). For that reason, the way CIS deals with reading in data files is via the concept of “data products”. Each product has its own very specific way of reading and interpreting the data in order for it to be ready to be plotted, analysed, etc.

So far, CIS can read the following ungridded data files:

Dataset	Product name	Type	File Signature
AERONET	Aeronet	Ground-stations	*.lev20
Aerosol CCI	Aerosol_CCI	Satellite	*ESACCI*AEROSOL*
CALIOP L1	Caliop_L1	Satellite	CAL_LID_L1-ValStage1-V3*.hdf
CALIOP L2	Caliop_L2	Satellite	CAL_LID_L2_05kmAPro-Prov-V3*.hdf
CloudSat	CloudSat	Satellite	*_CS_*GRANULE*.hdf
Flight campaigns	NCAR_NetCDF_RAF	Aircraft	RF*.nc
MODIS L2	MODIS_L2	Satellite	*MYD06_L2*.hdf, *MOD06_L2*.hdf, *MYD04_L2*.hdf, *MOD04_L2*.hdf, *MYDATML2.*.hdf, *MODATML2*.hdf
Cloud CCI	Cloud_CCI	Satellite	*ESACCI*CLOUD*
CSV datapoints	ASCII_Hyperpoints	N/A	*.txt
CIS ungridded	cis	CIS output	cis-*.nc
NCAR-RAF	NCAR_NetCDF_RAF	Aircraft	*.nc containing the attribute Conventions with the value NCAR-RAF/nimbus
GASSP	NCAR_NetCDF_RAF	Aircraft	*.nc containing the attribute GASSP_Version
GASSP	NCAR_NetCDF_RAF	Ship	*.nc containing the attribute GASSP_Version, with no altitude
GASSP	NCAR_NetCDF_RAF	Ground-station	*.nc containing the attribute GASSP_Version, with attributes Station_Lat, Station_Lon and Station_Altitude

It can also read the following gridded data types:

Dataset	Product name	Type	File Signature
MODIS L3 daily	MODIS_L3	Satellite	*MYD08_D3*.hdf, *MOD08_D3*.hdf, *MOD08_E3*.hdf
HadGEM pp data	HadGEM_PP	Gridded Model Data	*.pp
Net_CDF Gridded Data	NetCDF_Gridded	Gridded Model Data	*.nc (this is the default for NetCDF Files that do not match any other signature)

The file signature is used to automatically recognise which product definition to use. Note the product can overridden easily by being specified at the command line.

This is of course far from being an exhaustive list of what’s out there. To cope with this, a “plugin” architecture has been designed so that the user can readily use their own data product reading routines, without even having to change the code - see the plugin development page for more information. There are also mechanisms to allow you to overwrite default behaviour if the built-in products listed above do not achieve the desired results.

Datagroups¶

Most CIS commands operate on a ‘datagroup’, which is a unit of data containing one or more similar variables and one or more files from which those variables should be taken. A datagroup represents closely related data from a specific instrument or model and as such is associated with only one data product.

A datagroup is specified with the syntax:

<variable>...:<filename>[:product=<productname>] where:

• <variable> is a mandatory argument specifying the variable or variable names to use. This should be the name of the variable as described in the file, e.g. the NetCDF variable name or HDF SDS/VDATA variable name. Multiple variables may be specified by commas, and variables may be wildcarded using any wildcards compatible with the python module glob, so that *, ? and [] can all be used

Attention

When specifying multiple variables, it is essential that they be on the same grid (i.e. use the same coordinates).

• <filenames> is a mandatory argument used to specify the files to read the variable from. These can be specified as a comma seperated list of the following possibilities:

  1.   a single filename - this should be the full path to the file

  2.   a single directory - all files in this directory will be read

  3.   a wildcarded filename - A filename with any wildcards compatible with the python module glob, so that *, ? and [] can all be used. E.g., /path/to/my/test*file_[0-9].

Attention

When multiple files are specified (whether through use of commas, pointing at a directory, or wildcarding), then all those files must contain all of the specified variables, and the files should be ‘compatible’ - it should be possible to aggregate them together using a shared dimension - typically time (in a NetCDF file this is usually the unlimited dimension). So selecting multiple monthly files for a model run would be OK, but selecting files from two different datatypes would not be OK.

• <productname> is an optional argument used to specify the type of files being read. If omitted, the program will attempt to figure out which product to use based on the filename. See Reading to see a list of available products and their file signatures.

For example:

illum:20080620072500-ESACCI-L2_CLOUD-CLD_PRODUCTS-MODIS-AQUA-fv1.0.nc
Cloud_Fraction_*:MOD*,MODIS_dir/:product=MODIS_L2

Some file paths or variable names might contain colons (:), these need to be escaped so that CIS can tell the difference between it and the colons used to separate Datagroup elements. Simply use a backslash () to escape these characters. For example:

"TOTAL RAINFALL RATE\: LS+CONV KG/M2/S:C\:\My files\MODIS_dir:product=MODIS_L2"

Notice that we have used outer quotes to allow for the spaces in the variable and file names, and used the backslashes to escape the colons.

Reading hybrid height data with separate orography data¶

CIS supports the reading of gridded data containing hybrid height and pressure fields, with an orography field supplied in a separate file. The file containing the orography field (which should be properly referenced from a formula term in the data file) can just be appended to the list of files to be read in and CIS will attempt to create an appropriate altitude dimension.

Reading NetCDF4 Hierarchical Groups¶

CIS supports the reading of NetCDF4 hierarchical groups. These can be specified on the command line in the format <group>.<variable_name>, e.g. AVHRR.Ch4CentralWavenumber. Groups can be nested to any required depth like <group1>.<group2...>.<variable_name>.

CIS currently does not support writing out of NetCDF4 groups, so any groups read in will be output ‘flat’.

Example plots¶

LSF Batch Job Submission¶

CIS jobs may be submitted to an LSF type batch submission system (e.g. the JASMIN environment) by using the command cis.lsf instead of cis. In this case the job will be sent to the batch system and any output will be written to the log file.

Examples¶

Below are examples of subsetting using each of the supported products (together with a command to plot the output):

$ cis subset AO2CO2:RF04.20090114.192600_035100.PNI.nc time=[2009-01-14:19:26:00,2009-01-14:19:36:00] -o RF04-AO2CO2-out
$ cis plot AO2CO2:cis-RF04-AO2CO2-out.nc

$ cis subset IO_RVOD_ice_water_content:2007180125457_06221_CS_2B-CWC-RVOD_GRANULE_P_R04_E02.hdf t=[2007-06-29:13:00,2007-06-29:13:30] -o CloudSAT-out
$ cis plot IO_RVOD_ice_water_content:cis-CloudSAT-out.nc --xaxis=time --yaxis=altitude

$ cis subset Cloud_Top_Temperature:MYD06_L2.A2011100.1720.051.2011102130126.hdf x=[-50,-40],y=[0,10] -o MODIS_L2-out
$ cis plot Cloud_Top_Temperature:cis-MODIS_L2-out.nc

$ cis subset cwp:20080620072500-ESACCI-L2_CLOUD-CLD_PRODUCTS-MODIS-AQUA-fv1.0.nc x=[85,90],y=[-3,3] -o Cloud_CCI-out
$ cis plot atmosphere_mass_content_of_cloud_liquid_water:cis-Cloud_CCI-out.nc

$ cis subset AOD870:20080612093821-ESACCI-L2P_AEROSOL-ALL-AATSR_ENVISAT-ORAC_32855-fv02.02.nc x=[-5,20],y=[15,25] -o Aerosol_CCI-out
$ cis plot atmosphere_optical_thickness_due_to_aerosol:cis-Aerosol_CCI-out.nc

$ cis subset 440675Angstrom:920801_121229_Abracos_Hill.lev20 t=[2002] -o Aeronet-out
$ cis plot 440675Angstrom:cis-Aeronet-out.nc --xaxis=time --yaxis=440675Angstrom

$ cis subset solar_3:xglnwa.pm.k8dec-k9nov.vprof.tm.nc y=[0,90] -o Xglnwa_vprof-out
$ cis plot solar_3:Xglnwa_vprof-out.nc

$ cis subset solar_3:xglnwa.pm.k8dec-k9nov.col.tm.nc x=[0,180],y=[0,90] -o Xglnwa-out
$ cis plot solar_3:Xglnwa-out.nc

$ cis subset Cloud_Top_Temperature_Mean_Mean:MOD08_E3.A2010009.005.2010026072315.hdf x=[0,179.9],y=[0,90] -o MODIS_L3-out
$ cis plot Cloud_Top_Temperature_Mean_Mean:cis-MODIS_L3-out.nc

The files used above can be found at:

/group_workspaces/jasmin/cis/jasmin_cis_repo_test_files/
  2007180125457_06221_CS_2B-CWC-RVOD_GRANULE_P_R04_E02.hdf
  20080612093821-ESACCI-L2P_AEROSOL-ALL-AATSR_ENVISAT-ORAC_32855-fv02.02.nc
  20080620072500-ESACCI-L2_CLOUD-CLD_PRODUCTS-MODIS-AQUA-fv1.0.nc
  MOD08_E3.A2010009.005.2010026072315.hdf
  MYD06_L2.A2011100.1720.051.2011102130126.hdf
  RF04.20090114.192600_035100.PNI.nc
  xglnwa.pm.k8dec-k9nov.col.tm.nc
  xglnwa.pm.k8dec-k9nov.vprof.tm.nc
/group_workspaces/jasmin/cis/data/aeoronet/AOT/LEV20/ALL_POINTS/
  920801_121229_Abracos_Hill.lev20

Conditional Aggregation¶

Sometimes you may want to perform an aggregation over all the points that meet a certain criteria - for example, aggregating satellite data only where the cloud cover fraction is below a certain threshold. This is possible by performing a CIS evaluation on your data first - see Using Evaluation for Conditional Aggregation

Aggregation Examples¶

Ungridded aggregation¶

Aircraft Track¶

Original data:

$ cis plot TT_A:RF04.20090114.192600_035100.PNI.nc --xmin -180 --xmax -120 --ymin 0 --ymax 90

Aggregating onto a coarse grid:

$ cis aggregate TT_A:RF04.20090114.192600_035100.PNI.nc x=[-180,-120,3],y=[0,90,3] -o NCAR_RAF-1
$ cis plot TT_A:NCAR_RAF-1.nc

Aggregating onto a fine grid:

$ cis aggregate TT_A:RF04.20090114.192600_035100.PNI.nc x=[180,240,0.3],y=[0,90,0.3] -o NCAR_RAF-2
$ cis plot TT_A:NCAR_RAF-2.nc

Aggregating with altitude and time:

$ cis aggregate TT_A:RF04.20090114.192600_035100.PNI.nc t=[2009-01-14T19:30,2009-01-15T03:45,30M],z=[0,15000,1000] -o NCAR_RAF-3
$ cis plot TT_A:NCAR_RAF-3.nc --xaxis time --yaxis altitude

Aggregating with altitude and pressure:

$ cis aggregate TT_A:RF04.20090114.192600_035100.PNI.nc p=[100,1100,20],z=[0,15000,500] -o NCAR_RAF-4
$ cis plot TT_A:NCAR_RAF-4.nc --xaxis altitude --yaxis air_pressure --logy

MODIS L3 Data¶

Original data:

$ cis plot Cloud_Top_Temperature_Mean_Mean:MOD08_E3.A2010009.005.2010026072315.hdf

Aggregating with a mean kernel:

$ cis aggregate Cloud_Top_Temperature_Mean_Mean:MOD08_E3.A2010009.005.2010026072315.hdf x=[-180,180,10],y=[-90,90,10] -o cloud-mean
$ cis plot Cloud_Top_Temperature_Mean_Mean:cloud-mean.nc

Aggregating with the standard deviation kernel:

$ cis aggregate Cloud_Top_Temperature_Mean_Mean:MOD08_E3.A2010009.005.2010026072315.hdf:kernel=stddev x=[-180,180,10],y=[-90,90,10] -o cloud-stddev
$ cis plot Cloud_Top_Temperature_Mean_Mean:cloud-stddev.nc &

Aggregating with the maximum kernel:

$ cis aggregate Cloud_Top_Temperature_Mean_Mean:MOD08_E3.A2010009.005.2010026072315.hdf:kernel=max x=[-180,180,10],y=[-90,90,10] -o cloud-max
$ cis plot Cloud_Top_Temperature_Mean_Mean:cloud-max.nc

Aggregating with the minimum kernel:

$ cis aggregate Cloud_Top_Temperature_Mean_Mean:MOD08_E3.A2010009.005.2010026072315.hdf:kernel=min x=[-180,180,10],y=[-90,90,10] -o cloud-min
$ cis plot Cloud_Top_Temperature_Mean_Mean:cloud-min.nc

Gridded aggregation¶

Aggregating 3D model data over time and longitude to produce an averaged measure of variation with latitude:

$ cis aggregate rsutcs:rsutcs_Amon_HadGEM2-A_sstClim_r1i1p1_185912-188911.nc:kernel=mean t,x -o agg-out.nc
$ cis plot rsutcs:agg-out.nc --xaxis latitude --yaxis rsutcs -o gridded_collapse.png

This file can be found in:

/group_workspaces/jasmin/cis/data/CMIP5

Available Collocators and Kernels¶

Collocation output files¶

All ungridded collocation output files are prefixed with cis- and both ungridded and gridded data files are suffixed with .nc (so there is no need to specify the extension in the output parameter). This is to ensure the cis data product is always used to read collocated ungridded data.

It is worth noting that in the process of collocation all of the data and sample points are represented as 1-d lists, so any structural information about the input files is lost. This is done to ensure consistency in the collocation output. This means, however, that input files which may have been plotable as, for example, a heatmap may not be after collocation. In this situation plotting the data as a scatter plot will yield the required results.

Each collocated output variable has a history attributed created (or appended to) which contains all of the parameters and file names which went into creating it. An example might be:

double mass_fraction_of_cloud_liquid_water_in_air(pixel_number) ;
    ...
    mass_fraction_of_cloud_liquid_water_in_air:history = "Collocated onto sampling from:   [\'/test/test_files/RF04.20090114.192600_035100.PNI.nc\'] using CIS version V0R4M4\n",
        "variable: mass_fraction_of_cloud_liquid_water_in_air\n",
        "with files: [\'/test/test_files/xenida.pah9440.nc\']\n",
        "using collocator: DifferenceCollocator\n",
        "collocator parameters: {}\n",
        "constraint method: None\n",
        "constraint parameters: None\n",
        "kernel: None\n",
        "kernel parameters: None" ;
    mass_fraction_of_cloud_liquid_water_in_air:shape = 30301 ;
double difference(pixel_number) ;
    ...

Writing your own plugins¶

The collocation framework was designed to make it easy to write your own plugins. Plugins can be written to create new kernels, new constraint methods and even whole collocation methods. See the analysis plugin development section for more details.

Ungridded to Ungridded Collocation Examples¶

Ungridded data with vertical component¶

First subset two Caliop data files:

$ cis subset Temperature:CAL_LID_L2_05kmAPro-Prov-V3-01.2009-12-31T23-36-08ZN.hdf x=[170,180],y=[60,80],z=[28000,29000],p=[13,15] -o 2009
$ cis subset Temperature:CAL_LID_L2_05kmAPro-Prov-V3-01.2010-01-01T00-22-28ZD.hdf x=[170,180],y=[60,80],z=[28000,29000],p=[12,13.62] -o 2010

Results of subset can be plotted with:

$ cis plot Temperature:cis-2009.nc --itemwidth 25 --xaxis time --yaxis air_pressure
$ cis plot Temperature:cis-2010.nc --itemwidth 25 --xaxis time --yaxis air_pressure

Then collocate data, and plot output:

$ cis col Temperature:cis-2010.nc cis-2009.nc:collocator=box[p_sep=1.1],kernel=nn_p
$ cis plot Temperature:cis-out.nc --itemwidth 25 --xaxis time --yaxis air_pressure

The output for the two subset data files, and the collocated data should look like:

File Locations¶

The files used above can be found at:

/group_workspaces/jasmin/cis/data/caliop/CAL-LID-L2-05km-APro

Ungridded data collocation using k-D tree indexing¶

These examples show the syntax for using the k-D tree optimisation of the separation constraint. The indexing is only by horizontal position.

Nearest-Neighbour Kernel¶

The first example is of Aerosol CCI data on to the points of a MODIS L3 file (which is an ungridded data file but with points lying on a grid).

Subset to a relevant region:

$ cis subset AOD550:20080612093821-ESACCI-L2P_AEROSOL-ALL-AATSR_ENVISAT-ORAC_32855-fv02.02.nc x=[-6,0],y=[20,30] -o AOD550n_3
$ cis subset Cloud_Top_Temperature_Mean_Mean:MOD08_E3.A2010009.005.2010026072315.hdf x=[-6,0],y=[20,30] -o MOD08n_3

The results of subsetting can be plotted with:

$ cis plot AOD550:cis-AOD550n_3.nc --itemwidth 10
$ cis plot Cloud_Top_Temperature_Mean_Mean:cis-MOD08n_3.nc --itemwidth 20

These should look like:

To collocate with the nearest-neighbour kernel use:

$ cis col Cloud_Top_Temperature_Mean_Mean:cis-MOD08n_3.nc cis-AOD550n_3.nc:collocator=box[h_sep=150],kernel=nn_h -o MOD08_on_AOD550_nn_kdt

This can be plotted with:

$ cis plot Cloud_Top_Temperature_Mean_Mean:cis-MOD08_on_AOD550_nn_kdt.nc --itemwidth 10

The sample points are more closely spaced than the data points, hence a patchwork effect is produced.

Collocating the full Aerosol CCI file on to the MODIS L3 with:

$ cis col AOD550:20080612093821-ESACCI-L2P_AEROSOL-ALL-AATSR_ENVISAT-ORAC_32855-fv02.02.nc MOD08_E3.A2010009.005.2010026072315.hdf:variable=Cloud_Top_Temperature_Mean_Mean,collocator=box[h_sep=150],kernel=nn_h -o AOD550_on_MOD08_kdt_nn_full

gives the following result

Mean Kernel¶

This example is similar to the first nearest-neighbour collocation above:

$ cis col Cloud_Top_Temperature_Mean_Mean:cis-MOD08n_3.nc cis-AOD550n_3.nc:collocator=box[h_sep=75],kernel=mean -o MOD08_on_AOD550_hsep_75km

Plotting this again gives a granular result:

$ cis plot Cloud_Top_Temperature_Mean_Mean:cis-MOD08_on_AOD550_hsep_75km.nc --itemwidth 10

This example collocates the Aerosol CCI data on to the MODIS L3 grid:

$ cis col AOD550:20080612093821-ESACCI-L2P_AEROSOL-ALL-AATSR_ENVISAT-ORAC_32855-fv02.02.nc MOD08_E3.A2010009.005.2010026072315.hdf:variable=Cloud_Top_Temperature_Mean_Mean,collocator=box[h_sep=50,fill_value=-999],kernel=mean -o AOD550_on_MOD08_kdt_hsep_50km_full

This can be plotted as follows, with the full image and zoomed into a representative section show below:

$ cis plot AOD550:cis-AOD550_on_MOD08_kdt_hsep_50km_full.nc --itemwidth 50

The reverse collocation can be performed with this command (taking about 7 minutes):

$ cis col Cloud_Top_Temperature_Mean_Mean:MOD08_E3.A2010009.005.2010026072315.hdf 20080612093821-ESACCI-L2P_AEROSOL-ALL-AATSR_ENVISAT-ORAC_32855-fv02.02.nc:variable=AOD550,collocator=box[h_sep=100,fill_value=-999],kernel=mean -o MOD08_on_AOD550_kdt_hsep_100km_var_full

Plotting it with this command gives the result below:

$ cis plot Cloud_Top_Temperature_Mean_Mean:cis-MOD08_on_AOD550_kdt_hsep_100km_var_full.nc

Omitting the variable option in the sample group gives collocated values over a full satellite track (taking about 30 minutes):

$ cis col Cloud_Top_Temperature_Mean_Mean:MOD08_E3.A2010009.005.2010026072315.hdf 20080612093821-ESACCI-L2P_AEROSOL-ALL-AATSR_ENVISAT-ORAC_32855-fv02.02.nc:collocator=box[h_sep=100,fill_value=-999],kernel=mean -o MOD08_on_AOD550_kdt_hsep_100km_full

Plotting it with this command gives the result below:

$ cis plot Cloud_Top_Temperature_Mean_Mean:cis-MOD08_on_AOD550_kdt_hsep_100km_full.nc

File Locations¶

The files used above can be found at:

/group_workspaces/jasmin/cis/jasmin_cis_repo_test_files/
  20080612093821-ESACCI-L2P_AEROSOL-ALL-AATSR_ENVISAT-ORAC_32855-fv02.02.nc
  MOD08_E3.A2010009.005.2010026072315.hdf

Examples of collocation of ungridded data on to gridded¶

Simple Example of Aerosol CCI Data on to a 4x4 Grid¶

This is a trivial example that collocates on to a 4x4 spatial grid at a single time:

$ cis subset tas:tas_day_HadGEM2-ES_rcp45_r1i1p1_20051201-20151130.nc x=[0,2],y=[24,26],t=[2008-06-12T1,2008-06-12] -o tas_day_HadGEM2-ES_rcp45_r1i1p1_20051201-20151130.nc -o tas_1

$ cis subset AOD550:20080612093821-ESACCI-L2P_AEROSOL-ALL-AATSR_ENVISAT-ORAC_32855-fv02.02.nc x=[0,2],y=[24,26] -o AOD550n_1

$ cis col AOD550:cis-AOD550n_1.nc tas_1.nc:collocator=bin[fill_value=-9999.0],kernel=mean -o AOD550_on_tas_1

$ cis plot AOD550:AOD550_on_tas_1.nc

Note that for ungridded gridded collocation, and the collocator must be one bin or box and a kernel such as “mean” must be used.

The plotted image looks like:

$ cis subset tas:tas_day_HadGEM2-ES_rcp45_r1i1p1_20051201-20151130.nc x=[-6,-.0001],y=[20,30],t=[2008-06-11T1,2008-06-13] -o tas_3day

$ cis subset AOD550:20080612093821-ESACCI-L2P_AEROSOL-ALL-AATSR_ENVISAT-ORAC_32855-fv02.02.nc x=[-6,0],y=[20,30] -o AOD550n_3

$ cis col AOD550:cis-AOD550n_3.nc tas_3day.nc:collocator=bin[fill_value=-9999.0],kernel=mean -o AOD550_on_tas_3day

$ ncdump AOD550_on_tas_3day.nc |less

Aerosol CCI with One Time Step¶

This is as above but subsetting the grid to one time step so that the output can be plotted directly:

$ cis subset tas:tas_day_HadGEM2-ES_rcp45_r1i1p1_20051201-20151130.nc t=[2008-06-12T1,2008-06-12] -o tas_2008-06-12

$ cis col AOD550:20080612093821-ESACCI-L2P_AEROSOL-ALL-AATSR_ENVISAT-ORAC_32855-fv02.02.nc tas_2008-06-12.nc:collocator=bin[fill_value=-9999.0],kernel=mean -o AOD550_on_tas_1day

$ cis plot AOD550:AOD550_on_tas_1day.nc
$ cis plot AOD550:20080612093821-ESACCI-L2P_AEROSOL-ALL-AATSR_ENVISAT-ORAC_32855-fv02.02.nc
$ cis plot tas:tas_2008-06-12.nc

These are the plots before and after collocation:

Example with NCAR RAF Data¶

This example uses the data in RF04.20090114.192600_035100.PNI.nc. However, this file does not have standard_name or units accepted as valid by Iris. These were modified using ncdump and ncgen, giving RF04_fixed_AO2CO2.nc:

$ cis subset tas:tas_day_HadGEM2-ES_rcp45_r1i1p1_20051201-20151130.nc t=[2009-01-14T1,2009-01-14] -o tas_2009-01-14

$ cis col AO2CO2:RF04_fixed_AO2CO2.nc tas_2009-01-14.nc:collocator=bin[fill_value=-9999.0],kernel=mean -o RF04_on_tas

$ cis plot AO2CO2:RF04_on_tas.nc:product=NetCDF_Gridded

These are the plots before and after collocation:

Cloud CCI with One Time Step¶

This is analogous to the Aerosol CCI example:

$ cis subset tas:tas_day_HadGEM2-ES_rcp45_r1i1p1_20051201-20151130.nc t=[2008-06-20T1,2008-06-20] -o tas_2008-06-20

$ cis col cwp:20080620072500-ESACCI-L2_CLOUD-CLD_PRODUCTS-MODIS-AQUA-fv1.0.nc tas_2008-06-20.nc:collocator=bin[fill_value=-9999.0],kernel=mean -o Cloud_CCI_on_tas

$ cis plot cwp:Cloud_CCI_on_tas.nc
$ cis plot cwp:20080620072500-ESACCI-L2_CLOUD-CLD_PRODUCTS-MODIS-AQUA-fv1.0.nc

These are the plots before and after collocation:

/group_workspaces/jasmin/cis/jasmin_cis_repo_test_files/
  20080612093821-ESACCI-L2P_AEROSOL-ALL-AATSR_ENVISAT-ORAC_32855-fv02.02.nc
  20080620072500-ESACCI-L2_CLOUD-CLD_PRODUCTS-MODIS-AQUA-fv1.0.nc
  RF04.20090114.192600_035100.PNI.nc
/group_workspaces/jasmin/cis/example_data/
  RF04_fixed_AO2CO2.nc
/group_workspaces/jasmin/cis/gridded-test-data/cmip5.output1.MOHC.HadGEM2-ES.rcp45.day.atmos.day.r1i1p1.v20111128/
  tas_day_HadGEM2-ES_rcp45_r1i1p1_20051201-20151130.nc

Examples of Gridded to Gridded Collocation¶

Example of Gridded Data onto a Finer Grid¶

First to show original data subset to a single time slice:

$ cis subset rsutcs:rsutcs_Amon_HadGEM2-A_sstClim_r1i1p1_185912-188911.nc t=[1859-12-12] -o sub1

Plot for subset data:

$ cis plot rsutcs:sub1.nc

Collocate onto a finer grid, which was created using nearest neighbour:

$ cis col rsutcs:rsutcs_Amon_HadGEM2-A_sstClim_r1i1p1_185912-188911.nc dummy_high_res_cube_-180_180.nc:collocator=nn -o 2
$ cis subset rsutcs:2.nc t=[1859-12-12] -o sub2
$ cis plot rsutcs:sub2.nc

Collocate onto a finer grid, which was created using linear interpolation:

$ cis col rsutcs:rsutcs_Amon_HadGEM2-A_sstClim_r1i1p1_185912-188911.nc dummy_high_res_cube_-180_180.nc:collocator=lin -o 3
$ cis subset rsutcs:3.nc t=[1859-12-12] -o sub3
$ cis plot rsutcs:sub3.nc

Before, after nearest neighbour and after linear interpolation:

4D Gridded Data with latitude, longitude, air_pressure and time to a New Grid¶

$ cis col temp:aerocom.INCA.A2.RAD-CTRL.monthly.temp.2006-fixed.nc dummy_low_res_cube_4D.nc:collocator=lin -o 4D-col

Note the file aerocom.INCA.A2.RAD-CTRL.monthly.temp.2006-fixed.nc has the standard name of presnivs changed to air_pressure, in order to be read correctly.

Slices at Different Pressures¶

$ cis subset temp:4D-col.nc t=[2006-01],z=[100000] -o sub9
$ cis plot temp:sub9.nc
$ cis subset temp:4D-col.nc t=[2006-01],z=[0] -o sub10
$ cis plot temp:sub10.nc

Pressure against time¶

$ cis subset temp:4D-col.nc x=[0],t=[2006-01] -o sub11
$ cis plot temp:sub11.nc --xaxis latitude --yaxis air_pressure
$ cis subset temp:aerocom.INCA.A2.RAD-CTRL.monthly.temp.2006-fixed.nc x=[0],t=[2006-01] -o sub12
$ cis plot temp:sub12.nc --xaxis latitude --yaxis air_pressure

/group_workspaces/jasmin/cis/sprint_reviews/SR4-IB/gridded_col2

Plot Options¶

There are a number of optional arguments, which should be entered as a comma separated list after the mandatory arguments, for example variable:filename:product=Cis,edgecolor=black. The options are:

color

colour of markers, e.g. for scatter plot points or contour lines, see Available Colours and Markers

cmap

colour map to use, e.g. for contour lines or heatmap, see Available Colours and Markers

cmin

the minimum value for the colourmap

cmax

the maximum value for the colourmap

edgecolor

colour of scatter marker edges (can be used to differentiate scatter markers with a colourmap from the background plot)

itemstyle

shape of scatter marker, see Available Colours and Markers

label

name of datagroup for the legend

product

the data product to use for the plot

Additional datagroup options for contour plots only:

contnlevels

the number of levels for the contour plot

contlevels

a list of levels for the contour plot, e.g. contlevels=[0,1,3,10]

contlabel

options are true or false, if true then contour labels are shown

contwidth

width of the contour lines

contfontsize

size for labels on contour plot

Note that label refers to the label the plot will have on the legend, for example if a multi-series line graph or scatter plot is plotted. To set the labels of the axes, use --xlabel and --ylabel. --cbarlabel can be used to set the label on the colour bar.

The axes can be specified with --xaxis and --yaxis. Gridded data supports any coordinate axes available in the file, while ungridded data supports the following coordinate options (if available in the data):

• latitude
• longitude
• time
• altitude
• air_pressure
• variable - the variable being plotted

If the product is not specified, the program will attempt to figure out which product should be used based on the filename. See What kind of data can CIS deal with? to see a list of available products and their file signatures, or run cis plot -h.

Saving to a File¶

By default a plot will be displayed on screen. To save it to an image file instead, use the --output option. Available output types are png, pdf, ps, eps and svg, which can be selected using the appropriate filename extension, for example --output plot.svg.

Plot Formatting¶

There are a number of plot formatting options available:

--xlabel

The label for the x axis

--ylabel

The label for the y axis

--cbarlabel

The label for the colorbar

--xtickangle

The angle for the ticks on the x axis

--ytickangle

The angle for the ticks on the y axis

--title

The title of the plot

--itemwidth

The width of an item. Unit are points in the case of a line, and points squared in the case of a scatter point

--fontsize

The size of the font in points

--cmap

The colour map to be used when plotting a 3D plot, see Available Colours and Markers

--height

The height of the plot, in inches

--width

The width of the plot, in inches

--xbinwidth

The width of the histogram bins on the x axis

--ybinwidth

The width of the histogram bins on the y axis

--cbarorient

The orientation of the colour bar, either horizontal or vertical

--nocolourbar

Hides the colour bar on a 3D plot

--grid

Shows grid lines

--plotwidth

width of the plot in inches

--plotheight

height of the plot in inches

--cbarscale

this can be used to change the size of the colourbar when plotting and defaults to 0.55 for vertical colorbars, 1.0 for horizontal.

--coastlinescolour

The colour of the coastlines on a map, see Available Colours and Markers

--nasabluemarble

Use the NASA Blue Marble for the background, instead of coastlines, when doing lat-lon plots

Setting Plot Ranges¶

The arguments --xmin, --xmax, --xstep, --ymin, --ymax, --ystep, --vmin, --vmax, --vstep can be used to specify the range of values to plot, where x and y correspond to the axes and v corresponds to the colours.

When the arguments refer to dates or times, they should be in the format YYYY-MM-DDThh:mm:ss, where the time is optional. A colon or a space is also a valid date and time separator (if using a space quotes are necessary).

The step arguments are used to specify the tick spacing on the axes and vstep is used to specify the tick spacing on the colorbar.

When the step arguments refer to an amount of time, they should be in the ISO 8061 format PnYnMnDTnHnMnS, where any particular time group is optional, case does not matter, and T can be substituted for either a colon or a space (if using a space quotes are necessary).

For example, to specify a tick spacing of one month and six seconds on the x axis, the following argument should be given: --xstep 1m6S

Note: If a value is negative, then an equals sign must be used, e.g. --xmin=-5.

To plot using a log scale:

--logx

The x axis will be plotted using a log scale of base 10

--logy

The y axis will be plotted using a log scale of base 10

--logv

The values (colours) will be plotted using a log scale of base 10

Overlaying Multiple Plots¶

Overlaying multiple line graphs or scatter plots is straightforward, simply use the plot command as before but specify multiple files and variables, e.g.:

$ cis plot $var1:$filename1:edgecolor=black $var2:$filename2:edgecolor=red

To plot two variables from the same file, simply use the above command with $filename1 in place of $filename2.

However, using --type overlay allows multiple files to be specified on the command line to be plotted each with its own type, which is specified as e.g. type=heatmap, along with the other datagroup options. Currently supported plot types are heatmap, contour, contourf and scatter. An additional datagroup option available is transparency, which allows the transparency for a layer to be set. transparency take a value between 0 and 1, where 0 is completely opaque and 1 fully transparent.

For example, to plot a heatmap and a contour plot the following options can be used:

cis plot var1:file1:type=heatmap var2:file2:type=contour,color=white --type overlay --plotwidth 20 --plotheight 15 --cbarscale 0.5 -o overlay.png

Note that the default plot dimensions are deduced from the first datagroup specified.

Many more examples are available in the overlay examples page.

Available Colours and Markers¶

CIS recognises any valid html colour, specified using its name e.g. red for options such as item colour (line/scatter colour) and the colour of the coast lines.

A list of available colour maps for 3D plots, such as heatmaps, scatter and contour plots, can be found here: colour maps.

For a list of available scatter point styles, see here: scatter point styles.

Evaluation Examples¶

Comparison of annual Aerosol Optical Thickness from models¶

In this example we compare annual Aerosol Optical Thickness from ECHAM and HadGEM model data. The data used in this example can be found at /group_workspaces/jasmin/cis/data.

First we produce annual averages of our data by aggregating:

$ cis aggregate od550aer:ECHAM_fixed/2007_2D_3hr/od550aer.nc t -o echam-od550aer
$ cis aggregate od550aer:HadGEM_fixed/test_fix/od550aer.nc t -o hadgem-od550aer

$ cis plot od550aer:echam-od550aer.nc --xmin -180 --xmax 180 --cbarorient=horizontal --title="ECHAM AOT550" --vmin=0 --vmax=0.5
$ cis plot od550aer:hadgem-od550aer.nc --xmin -180 --xmax 180 --cbarorient=horizontal --title="HadGEM AOT550" --vmin=0 --vmax=0.5

We then linearly interpolate the HadGEM data onto the ECHAM grid:

$ cis col od550aer:hadgem-od550aer.nc echam-od550aer.nc:collocator=lin -o hadgem-od550aer-collocated

$ cis plot od550aer:hadgem-od550aer-collocated.nc --xmin -180 --xmax 180 --cbarorient=horizontal --title="HadGEM AOT550" --vmin=0 --vmax=0.5

Next we subtract the two fields using:

$ cis eval od550aer=a:echam-od550aer.nc od550=b:hadgem-od550aer-collocated.nc "a-b" 1 -o modeldifference

Finally we plot the evaluated output:

$ cis plot od550aer:modeldifference.nc --xmin -180 --xmax 180 --cbarorient=horizontal --title="ECHAM-HadGEM difference AOT550" --v min=-0.25 --vmax=0.2

Calculation of Angstrom exponent for AERONET data¶

AERONET data allows us to calculate Angstrom Exponent (AE) and then compare it against the AE already in the file. They should strongly correlate although it is not expected they will be identical due to averaging etc during production of AERONET datafiles.

The file agoufou.lev20 refers to /group_workspaces/jasmin/cis/data/aeronet/AOT/LEV20/ALL_POINTS/920801_121229_Agoufou.lev20

The AE is calculated using an eval statement:

$ cis eval AOT_440,AOT_870:agoufou.lev20 "(-1)* (numpy.log(AOT_870/AOT_440)/numpy.log(870./440.))" 1 -o alfa

Plotting it shows the expected correlation:

$ cis plot 440-870Angstrom:agoufou.lev20 calculated_variable:cis-alfa.nc --type comparativescatter --itemwidth=10 --xlabel="AERONET 440-870Angstrom" --ylabel="AERONET (-1)*(numpy.log(AOT_870/AOT_440)/numpy.log(870./440.))"

This correlation can be confirmed by using the CIS stats command:

$ cis stats 440-870Angstrom:agoufou.lev20 calculated_variable:cis-alfa.nc

==================================
RESULTS OF STATISTICAL COMPARISON:
==================================
Number of points: 63126
Mean value of dataset 1: 0.290989032142
Mean value of dataset 2: 0.295878214327
Standard deviation for dataset 1: 0.233995525021
Standard deviation for dataset 2: 0.235381075635
Mean of absolute difference: 0.00488918218519
Standard deviation of absolute difference: 0.00546343157047
Mean of relative difference: 0.0284040419499
Standard deviation of relative difference: 3.95137224542
Spearman's rank coefficient: 0.999750939223
Linear regression gradient: 1.00566622549
Linear regression intercept: 0.003240372714
Linear regression r-value: 0.999746457079
Linear regression standard error: 0.00530006646489

Using Evaluation for Conditional Aggregation¶

The eval command can be combined with other CIS commands to allow you to perform more complex tasks than would otherwise be possible.

For example, you might want to aggregate a satellite measurement of one variable only when the corresponding cloud cover fraction (stored in separate variable) is less than a certain value. The aggregate command doesn’t allow this kind of conditional aggregation on its own, but you can use an evaluation to achieve this in two stages.

In this example we use the MODIS file MOD04_L2.A2010001.2255.005.2010005215814.hdf in directory /group_workspaces/jasmin/cis/data/MODIS/MOD04_L2/. The optical depth and cloud cover variables can be seen in the following two plots:

$ cis plot Optical_Depth_Land_And_Ocean:MOD04_L2.A2010001.2255.005.2010005215814.hdf --xmin 132 --xmax 162 --ymin -70 --title "Aerosol optical depth" --cbarscale 0.5 --itemwidth 10 -o cloud_fraction.png
$ cis plot Cloud_Fraction_Ocean:MOD04_L2.A2010001.2255.005.2010005215814.hdf --xmin 132 --xmax 162 --ymin -70 --title "Cloud cover fraction" --cbarscale 0.5 --itemwidth 10 -o cloud_fraction.png

First we perform an evaluation using the numpy.masked_where method to produce an optical depth variable that is masked at all points where the cloud cover is more than 20%:

$ cis eval Cloud_Fraction_Ocean=cloud,Optical_Depth_Land_And_Ocean=od:MOD04_L2.A2010001.2255.005.2010005215814.hdf "numpy.ma.masked_where(cloud > 0.2, od)" 1 -o od:masked_optical_depth.nc
$ cis plot od:cis-masked_optical_depth.nc --xmin 132 --xmax 162 --ymin -70 --title Aerosol optical depth --cbarscale 0.5 --itemwidth 10 -o masked_optical_depth.png'

Then we perform an aggregation on this masked output file to give the end result - aerosol optical depth aggregated only using points where the cloud cover is less than 20%:

$ cis aggregate od:cis-masked_optical_depth.nc x=[132,162,0.5],y=[-70,-57,0.5] -o aggregated_masked_optical_depth
$ cis plot od:aggregated_masked_optical_depth.nc --xmin 132 --xmax 162 --ymin -70 --title "Aerosol optical depth (cloud fraction > 0.2)" --cbarscale 0.5 -o aggregated_aod.png

Statistics Example¶

In this example, we perform a statistical comparison of Aeronet aerosol optical thickness at two wavelengths. The data we are using is shown in the following CIS plot commands and can be found at /group_workspaces/jasmin/cis/data:

$ cis plot AOT_500:aeronet/AOT/LEV20/ALL_POINTS/920801_121229_Yonsei_University.lev20 --title "Aerosol optical thickness 550nm"
$ cis plot AOT_440:aeronet/AOT/LEV20/ALL_POINTS/920801_121229_Yonsei_University.lev20 --title "Aerosol optical thickness 440nm"

We then perform a statistical comparison of these variables using:

$ cis stats AOT_500,AOT_440:aeronet/AOT/LEV20/ALL_POINTS/920801_121229_Yonsei_University.lev20

Which gives the following output:

===================================================================
RESULTS OF STATISTICAL COMPARISON:
-------------------------------------------------------------------
Compared all points which have non-missing values in both variables
===================================================================
Number of points: 10727
Mean value of dataset 1: 0.427751965508
Mean value of dataset 2: 0.501316673814
Standard deviation for dataset 1: 0.307680514916
Standard deviation for dataset 2: 0.346274598431
Mean of absolute difference: 0.0735647083061
Standard deviation of absolute difference: 0.0455684788406
Mean of relative difference: 0.188097066086
Standard deviation of relative difference: 0.0528621773819
Spearman's rank coefficient: 0.998289763952
Linear regression gradient: 1.12233533743
Linear regression intercept: 0.0212355272705
Linear regression r-value: 0.997245296339
Linear regression standard error: 0.0256834603945

Contour over heatmap¶

cis plot od550aer:HadGEM_od550aer-subset.nc:type=heatmap rsutcs:HadGEM_rsutcs-subset.nc:type=contour,color=white,contlevels=[1,10,25,50,175] --type overlay --plotwidth 20 --plotheight 15 --cbarscale 0.5 -o overlay1.png

cis plot od550aer:HadGEM_od550aer-subset.nc:type=heatmap,cmap=binary rsutcs:HadGEM_rsutcs-subset.nc:type=contour,cmap=jet,contlevels=[1,10,25,50,175] --type overlay --xmin -180 --xmax 180 --plotwidth 20 --plotheight 15 --cbarscale 0.5 -o overlay2.png

Filled contour with transparency on NASA Blue Marble¶

cis plot od550aer:HadGEM_od550aer-subset.nc:cmap=Reds,type=contourf,transparency=0.5,cmin=0.15 --type overlay --xmin -180 --xmax 180 --plotwidth 20 --plotheight 15 --cbarscale 0.5 --nasabluemarble

Scatter plus Filled Contour¶

cis subset rsutcs:HadGEM_rsutcs-subset.nc x=[-180,-90],y=[0,90] -o HadGEM_rsutcs-subset2

cis plot GGALT:RF04.20090114.192600_035100.PNI.nc:type=scatter rsutcs:HadGEM_rsutcs-subset2.nc:type=contourf,contlevels=[0,10,20,30,40,50,100],transparency=0.7,contlabel=true,contfontsize=18 --type overlay --plotwidth 20 --plotheight 15 --xaxis longitude --yaxis latitude --xmin -180 --xmax -90 --ymin 0 --ymax 90 --itemwidth 20 -o overlay4.png

cis plot GGALT:RF04.20090114.192600_035100.PNI.nc:type=scatter rsutcs:HadGEM_rsutcs-subset2.nc:type=contourf,contlevels=[40,50,100],transparency=0.3,contlabel=true,contfontsize=18,cmap=Reds --type overlay --plotwidth 20 --plotheight 15 --xaxis longitude --yaxis latitude --xmin -180 --xmax -90 --ymin 0 --ymax 90 --itemwidth 20 --nasabluemarble -o overlay5.png

File Locations¶

The gridded data files can be found at:

/group_workspaces/jasmin/cis/AeroCom/A2/HadGEM3-A-GLOMAP.A2.CTRL/renamed

and the ungridded:

/group_workspaces/jasmin/cis/jasmin_cis_repo_test_files

Introduction¶

One of the key strengths of CIS is the ability for users to create their own plugins to read data which CIS doesn’t currently support. These plugins can then be shared with the community to allow other users access to that data. Although the plugins are written in Python this tutorial assumes no experience in Python. Some programming experience is however assumed.

Here we describe the process of creating and sharing a plugin. A CIS plugin is simply a python (.py) file with a set of methods (or functions) to describe how the plugin should behave.

There are a few methods that the plugin must contain, and some which are optional. A skeleton plugin would look like this:

class MyProd(AProduct):
    def get_file_signature(self):
    # Code goes here

    def create_coords(self, filenames):
        ...

    def create_data_object(self, filenames, variable):
        ...

Note that in python whitespace matters! When filling in the above methods the code for the method should be indented from the signature by four spaces like this:

Class MyProd(AProduct):

    def get_file_signature(self):
        # Code goes here
        foo = bar

Note also that the name of the plugin (MyProd) in this case should be changed to describe the data which it will read. (Don’t change the AProduct part though – this is important for telling CIS that this is a plugin for reading data.)

In order to turn the above skeleton into a working plugin we need to fill in each of the methods with the some code, which turns our data into something CIS will understand. Often it is easiest to start from an existing plugin that reads closely matching data. For example creating a plugin to read some other CCI data would probably be easiest to start from the Cloud or Aerosol CCI plugins. We have created three different tutorials to walk you through the creation of some of the existing plugins to try and illustrate the process. The Easy tutorial walks through the creation of a basic plugin, the Medium tutorial builds on that by creating a plugin which has a bit more detail, and finally the Advanced plugin talks through some of the main considerations when creating a large and complicated plugin.

A more general template plugin is included here in case no existing plugin matches your need. We have also created a short reference describing the purpose of each method the plugins implement here.

cis subset a_variable:filename.nc:product=MyProd ...

Tutorials¶

def get_file_signature(self):
    return [r'cis\\-.\*\\.nc']

def create_coords(self, filenames, usr_variable=None):
    from cis.data_io.netcdf import read_many_files_individually, get_metadata
    from cis.data_io.Coord import Coord, CoordList
    from cis.data_io.ungridded_data import UngriddedCoordinates

var_data = read_many_files_individually(filenames, ["longitude","latitude", "time"])

coords = CoordList()
coords.append(Coord(var_data[“longitude”,get_metadata(var_data[“longitude”][0]),axis=”x”))
coords.append(Coord(var_data[“latitude”,get_metadata(var_data[“latitude”][0]),axis=”y”))
coords.append(Coord(var_data[“time”,get_metadata(var_data[“time”][0]),axis=”t”))

return UngriddedCoordinates(coords)

def create_data_object(self, filenames, variable):
    from cis.data_io.ungridded_data import UngriddedData
    usr_var_data = read_many_files_individually(filenames,variable)[variable]

coords = self.create_coords(filename)

return UngriddedData(usr_var_data, get_metadata(usr_var_data[0]),coords)

import logging
from cis.data_io.products.AProduct import AProduct
from cis.data_io.netcdf import read_many_files_individually, get_metadata

class cis(AProduct):

     def get_file_signature(self):
         return [r'cis\-.*\.nc']

     def create_coords(self, filenames, usr_variable=None):
         from cis.data_io.Coord import Coord, CoordList
         from cis.data_io.ungridded_data import UngriddedCoordinates
         from cis.exceptions import InvalidVariableError

         variables = [("longitude", "x"), ("latitude", "y"), ("altitude", "z"), ("time", "t"), ("air_pressure", "p")]

         logging.info("Listing coordinates: " + str(variables))

         coords = CoordList()
         for variable in variables:
             try:
                 var_data = read_many_files_individually(filenames,variable[0])[variable[0]]
                 coords.append(Coord(var_data, get_metadata(var_data[0]),axis=variable[1]))
             except InvalidVariableError:
                 pass

         return UngriddedCoordinates(coords)

     def create_data_object(self, filenames, variable):
         from cis.data_io.ungridded_data import UngriddedData
         usr_var_data = read_many_files_individually(filenames,variable)[variable]
         coords = self.create_coords(filename)
         return UngriddedData(usr_var_data, get_metadata(usr_var_data[0]), coords)

def create_coords(self, filenames, variable=None):
    return UngriddedCoordinates(self._create_coord_list(filenames))

def _create_coord_list(self, filenames, data=None):
    from cis.data_io.ungridded_data import Metadata
    from cis.data_io.aeronet import load_multiple_aeronet

if data is None:
    data = load_multiple_aeronet(filenames)

coords = CoordList()
coords.append(Coord(data['longitude'], Metadata(name="Longitude",shape=(len(data),),units="degrees_east", range=(-180, 180))))
coords.append(Coord(data['latitude'], Metadata(name="Latitude",shape=(len(data),),units="degrees_north", range=(-90, 90))))
coords.append(Coord(data['altitude'], Metadata(name="Altitude",shape=(len(data),), units="meters")))
time_coord = Coord(data["datetime"], Metadata(name="DateTime",standard_name='time', shape=(len(data),),units="DateTime Object"), "X")

time_coord.convert_datetime_to_standard_time()
coords.append(time_coord)

return coords

def create_data_object(self, filenames, variable):
    from cis.data_io.aeronet import load_multiple_aeronet
    from cis.exceptions import InvalidVariableError

try:
    data_obj = load_multiple_aeronet(filenames, [variable])
except ValueError:
    raise InvalidVariableError(variable + " does not exist in " + str(filenames))

coords = self._create_coord_list(filenames, data_obj)

return UngriddedData(data_obj[variable], Metadata(name=variable, long_name=variable, shape=(len(data_obj),), missing_value=-999.0), coords)

class Aeronet(AProduct):

    def get_file_signature(self):
        return [r'.*\.lev20']

    def _create_coord_list(self, filenames, data=None):
        from cis.data_io.ungridded_data import Metadata
        from cis.data_io.aeronet import load_multiple_aeronet

        if data is None:
            data = load_multiple_aeronet(filenames)

        coords = CoordList()
        coords.append(Coord(data['longitude'], Metadata(name="Longitude", shape=(len(data),),
                                                        units="degrees_east", range=(-180, 180))))
        coords.append(Coord(data['latitude'], Metadata(name="Latitude", shape=(len(data),),
                                                       units="degrees_north", range=(-90, 90))))
        coords.append(Coord(data['altitude'], Metadata(name="Altitude", shape=(len(data),), units="meters")))
        time_coord = Coord(data["datetime"], Metadata(name="DateTime", standard_name='time', shape=(len(data),),
                                                      units="DateTime Object"), "X")
        time_coord.convert_datetime_to_standard_time()
        coords.append(time_coord)

        return coords

    def create_coords(self, filenames, variable=None):
        return UngriddedCoordinates(self._create_coord_list(filenames))

    def create_data_object(self, filenames, variable):
        from cis.data_io.aeronet import load_multiple_aeronet
        from cis.exceptions import InvalidVariableError

        try:
            data_obj = load_multiple_aeronet(filenames, [variable])
        except ValueError:
            raise InvalidVariableError(variable + " does not exist in " + str(filenames))

        coords = self._create_coord_list(filenames, data_obj)

        return UngriddedData(data_obj[variable],
                             Metadata(name=variable, long_name=variable, shape=(len(data_obj),), missing_value=-999.0),
                             coords)

def get_file_signature(self):
    product_names = ['MYD06_L2', 'MOD06_L2', 'MYD04_L2', 'MOD04_L2']
    regex_list = [r'.*' + product + '.*\.hdf' for product in product_names]
    return regex_list

def get_variable_names(self, filenames, data_type=None):
    import pyhdf.SD

    # Determine the valid shape for variables
    sd = pyhdf.SD.SD(filenames[0])
    datasets = sd.datasets()
    valid_shape = datasets['Latitude'][1]  # Assumes that latitude shape == longitude shape (it should)

    variables = set([])
    for filename in filenames:
        sd = pyhdf.SD.SD(filename)
        for var_name, var_info in sd.datasets().iteritems():
            if var_info[1] == valid_shape:
                variables.add(var_name)

    return variables

def __get_data_scale(self, filename, variable):
    from cis.exceptions import InvalidVariableError
    from pyhdf import SD

    try:
        meta = SD.SD(filename).datasets()[variable][0][0]
    except KeyError:
        raise InvalidVariableError("Variable "+variable+" not found")

    for scaling in self.modis_scaling:
        if scaling in meta:
            return scaling
    return None

def __field_interpolate(self,data,factor=5):
    '''
    Interpolates the given 2D field by the factor,
    edge pixels are defined by the ones in the centre,
    odd factors only!
    '''
    import numpy as np

    logging.debug("Performing interpolation...")

    output = np.zeros((factor*data.shape[0],factor*data.shape[1]))*np.nan
    output[int(factor/2)::factor,int(factor/2)::factor] = data
    for i in range(1,factor+1):
        output[(int(factor/2)+i):(-1*factor/2+1):factor,:] = i*((output[int(factor/2)+factor::factor,:]-output[int(factor/2):(-1*factor):factor,:])
                                                                /float(factor))+output[int(factor/2):(-1*factor):factor,:]
    for i in range(1,factor+1):
        output[:,(int(factor/2)+i):(-1*factor/2+1):factor] = i*((output[:,int(factor/2)+factor::factor]-output[:,int(factor/2):(-1*factor):factor])
                                                                /float(factor))+output[:,int(factor/2):(-1*factor):factor]
    return output

def _create_coord_list(self, filenames, variable=None):
    import datetime as dt

    variables = ['Latitude', 'Longitude', 'Scan_Start_Time']
    logging.info("Listing coordinates: " + str(variables))

sdata, vdata = hdf.read(filenames, variables)

apply_interpolation = False
if variable is not None:
    scale = self.__get_data_scale(filenames[0], variable)
    apply_interpolation = True if scale is "1km" else False

lat = sdata['Latitude']
sd_lat = hdf.read_data(lat, "SD")
lat_data = self.__field_interpolate(sd_lat) if apply_interpolation else sd_lat
lat_metadata = hdf.read_metadata(lat, "SD")
lat_coord = Coord(lat_data, lat_metadata,'Y')

lon = sdata['Longitude']
lon_data = self.__field_interpolate(hdf.read_data(lon,"SD")) if apply_interpolation else hdf.read_data(lon,"SD")
lon_metadata = hdf.read_metadata(lon,"SD")
lon_coord = Coord(lon_data, lon_metadata,'X')

time = sdata['Scan_Start_Time']
time_metadata = hdf.read_metadata(time,"SD")
# Ensure the standard name is set
time_metadata.standard_name = 'time'
time_coord = Coord(time,time_metadata,"T")
time_coord.convert_TAI_time_to_std_time(dt.datetime(1993,1,1,0,0,0))

return CoordList([lat_coord,lon_coord,time_coord])

def create_coords(self, filenames, variable=None):
    return UngriddedCoordinates(self._create_coord_list(filenames))

def create_data_object(self, filenames, variable):
    logging.debug("Creating data object for variable " + variable)

    # reading coordinates
    # the variable here is needed to work out whether to apply interpolation to the lat/lon data or not
    coords = self._create_coord_list(filenames, variable)

    # reading of variables
    sdata, vdata = hdf.read(filenames, variable)

    # retrieve data + its metadata
    var = sdata[variable]
    metadata = hdf.read_metadata(var, "SD")

    return UngriddedData(var, metadata, coords)

def get_file_format(self, filenames):
    """
    Get the file format
    :param filenames: the filenames of the file
    :return: file format
    """

    return "HDF4/ModisL2"

Data plugin reference¶

This section provides a reference describing the expected behaviour of each of the functions a plugin can implement. The following methods are mandatory:

AProduct.get_file_signature()

This method should return a list of regular expressions, which CIS uses to decide which data product to use for a given file. If more than one regular expression is provided in the list then the file can match any of the expressions. The first product with a signature that matches the filename will be used. The order in which the products are searched is determined by the priority property, highest value first; internal products generally have a priority of 10.

For example, this would match all files with a name containing the string ‘CODE’ and with the ‘nc’ extension.:

return [r'.*CODE*.nc']

Note

If the signature has matched the framework will call AProduct.get_file_type_error(), this gives the product a chance to open the file and check the contents.

Returns:	A list of regex to match the product’s file naming convention.
Return type:	list

AProduct.create_coords(filenames)

Reads the coordinates from one or more files. Note that this method may have to make certain assumptions about the file in order to return a single coordinate set. The user should be warned through the logger if this is the case.

Parameters:	filenames (list) – List of filenames to read coordinates from
Returns:	CommonData object

AProduct.create_data_object(filenames, variable)

Create and return an CommonData object for a given variable from one or more files.

Parameters:	filenames (list) – List of filenames of files to read variable (str) – Variable to read from the files
Returns:	An CommonData object representing the specified variable
Raises:	FileIOError – Unable to read a file InvalidVariableError – Variable not present in file

While these may be implemented optionally:

AProduct.get_variable_names(filenames, data_type=None)

Get a list of available variable names from the filenames list passed in. This general implementation can be overridden in specific products to include/exclude variables which may or may not be relevant. The data_type parameter can be used to specify extra information.

Parameters:	filenames (list) – List of string filenames of files to be read from data_type (str) – ‘SD’ or ‘VD’ to specify only return SD or VD variables from HDF files. This may take on other values in specific product implementations.
Returns:	A set of variable names as strings
Return type:	str

AProduct.get_file_type_error(filename)

Check a single file to see if it is of the correct type, and if not return a list of errors. If the return is None then there are no errors and this is the correct data product to use for this file.

This method gives a mechanism for a data product to identify itself as the correct product when a specific enough file signature cannot be provided. For example GASSP is a type of NetCDF file and so filenames end with .nc but so do other NetCDF files, so the data product opens the file and looks for the GASSP version attribute, and if it doesn’t find it returns an error.

Parameters:	filename (str) – The filename for the file
Returns:	List of errors, or None
Return type:	list or None

AProduct.get_file_format(filename)

Returns a file format hierarchy separated by slashes, of the form TopLevelFormat/SubFormat/SubFormat/Version. E.g. NetCDF/GASSP/1.0, ASCII/ASCIIHyperpoint or HDF4/CloudSat. This is mainly used within the ceda_di indexing tool. If not set it will default to the products name.

A filename of an example file can be provided to enable the determination of, for example, a dataset version number.

Parameters:	filename (str) – Filename of file to be inspected
Returns:	File format, of the form [parent/]format/specific instance/version, or the class name
Return type:	str
Raises:	FileFormatError if there is an error

Basic collocation design¶

The diagram below demonstrates the basic design of the collocation system, and the roles of each of the components. In the simple case of the default collocator (which returns only one value) the Collocator loops over each of the sample points, calls the relevant Constraint to reduce the number of data points, and then the Kernel which returns a single value, which the collocator stores.

Kernel¶

A kernel is used to convert the constrained points into values in the output. There are two sorts of kernel one which act on the final point location and a set of data points (these derive from Kernel) and the more specific kernels which act upon just an array of data (these derive from AbstractDataOnlyKernel, which in turn derives from Kernel). The data only kernels are less flexible but should execute faster. To create a new kernel inherit from Kernel and implement the abstract method Kernel.get_value(). To make a data only kernel inherit from AbstractDataOnlyKernel and implement AbstractDataOnlyKernel.get_value_for_data_only() and optionally overload AbstractDataOnlyKernel.get_value(). These methods are outlined below.

Kernel.get_value(point, data)

This method should return a single value (if Kernel.return_size is 1) or a list of n values (if Kernel.return_size is n) based on some calculation on the data given a single point.

The data is deliberately left unspecified in the interface as it may be any type of data, however it is expected that each implementation will only work with a specific type of data (gridded, ungridded etc.) Note that this method will be called for every sample point and so could become a bottleneck for calculations, it is advisable to make it as quick as is practical. If this method is unable to provide a value (for example if no data points were given) a ValueError should be thrown.

Parameters:	point – A single HyperPoint data – A set of data points to reduce to a single value
Returns:	For return_size=1 a single value (number) otherwise a list of return values, which represents some operation on the points provided
Raises ValueError:
	When the method is unable to return a value

AbstractDataOnlyKernel.get_value_for_data_only(values)

This method should return a single value (if Kernel.return_size is 1) or a list of n values (if Kernel.return_size is n) based on some calculation on the the values (a numpy array).

Note that this method will be called for every sample point in which data can be placed and so could become a bottleneck for calculations, it is advisable to make it as quick as is practical. If this method is unable to provide a value (for example if no data points were given) a ValueError should be thrown. This method will not be called if there are no values to be used for calculations.

Parameters:	values – A numpy array of values (can not be none or empty)
Returns:	A single data item if return_size is 1 or a list of items containing Kernel.return_size items
Raises ValueError:
	If there are any problems creating a value

Constraint¶

The constraint limits the data points for a given sample point. The user can also add a new constraint mechanism by subclassing Constraint and providing an implementation for Constraint.constrain_points(). If more control is needed over the iteration sequence then the Constraint.get_iterator() method can also be overloaded. Note however that this may not be respected by all collocators, who may still iterate over all sample data points. It is possible to write your own collocator (or extend an existing one) to ensure the correct iterator is used - see the next section. Both these methods, and their signatures, are outlined below.

Constraint.constrain_points(point, data)

This method should return a subset of the data given a single reference point. It is expected that the data returned should be of the same type as that given - but this isn’t mandatory. It is possible that this function will return zero points (no data), the collocation class is responsible for providing a fill_value.

Parameters:	point (HyperPoint) – A single HyperPoint data – A set of data points to be reduced
Returns:	A reduced set of data points

Constraint.get_iterator(missing_data_for_missing_sample, coord_map, coords, data_points, shape, points, output_data)

Iterator to iterate through the points needed to be calculated. The default iterator, iterates through all the sample points calling Constraint.constrain_points() for each one.

Parameters:

missing_data_for_missing_sample – If true anywhere there is missing data on the sample then final point is missing; otherwise just use the sample coord_map – Coordinate map - list of tuples of indexes of hyperpoint coord, data coords and output coords coords – The coordinates to map the data onto data_points – The (non-masked) data points shape – Shape of the final data values points – The original points object, these are the points to collocate output_data – Output data set

Returns:

Iterator which iterates through (sample indices, hyper point and constrained points) to be placed in these points

To enable a constraint to use a AbstractDataOnlyKernel, the method get_iterator_for_data_only() should be implemented (again though, this may be ignored by a collocator). An example of this is the BinnedCubeCellOnlyConstraint.get_iterator_for_data_only() implementation.

Collocator¶

Another plugin which is available is the collocation method itself. A new one can be created by subclassing Collocator and providing an implementation for Collocator.collocate(). This method takes a number of sample points and applies the given constraint and kernel methods on the data for each of those points. It is responsible for returning the new data object to be written to the output file. As such, the user could create a collocation routine capable of handling multiple return values from the kernel, and hence creating multiple data objects, by creating a new collocation method.

The interface is detailed here:

Collocator.collocate(points, data, constraint, kernel)

The method is responsible for setting up and running the collocation. It should take a set of data and map that onto the given (sample) points using the constraint and kernel provided.

Parameters:	points – A set of sample points onto which we will collocate some other ‘data’ data – Some other data to be collocated onto the ‘points’ constraint – A Constraint instance which provides a Constraint.constrain_points() method, and optionally an Constraint.get_iterator() method kernel – A Kernel instance which provides a Kernel.get_value() method
Returns:	One or more CommonData (or subclasses of) objects whose coordinates lie on the points defined above.

Implementation¶

For all of these plugins any new variables, such as limits, constraint values or averaging parameters, are automatically set as attributes in the relevant object. For example, if the user wanted to write a new constraint method (AreaConstraint, say) which needed a variable called area, this can be accessed with self.area within the constraint object. This will be set to whatever the user specifies at the command line for that variable, e.g.:

$ ./cis.py col my_sample_file rain:"model_data_?.nc"::AreaConstraint,area=6000,fill_value=0.0:nn_gridded

Example implementations of new collocation plugins are demonstrated below for each of the plugin types:

class MyCollocator(Collocator):

    def collocate(self, points, data, constraint, kernel):
        values = []
        for point in points:
            con_points = constraint.constrain_points(point, data)
            try:
                values.append(kernel.get_value(point, con_points))
            except ValueError:
                values.append(constraint.fill_value)
        new_data = LazyData(values, data.metadata)
        new_data.missing_value = constraint.fill_value
        return new_data


class MyConstraint(Constraint):

    def constrain_points(self, ref_point, data):
        con_points = []
        for point in data:
            if point.value > self.val_check:
                con_points.append(point)
        return con_points


class MyKernel(Kernel):

    def get_value(self, point, data):
        nearest_point = point.furthest_point_from()
        for data_point in data:
            if point.compdist(nearest_point, data_point):
                nearest_point = data_point
        return nearest_point.val

Source files¶

The cis source code is hosted at https://github.com/cedadev/jasmin_cis.git, while the conda recipes and other files are hosted here: https://github.com/cistools.

Test suites¶

The unit tests suite can be ran using Nose readily. Just go the root of the repository (i.e. cis) and type nosetests cis/test/unit and this will run the full suite of tests.

A comprehensive set of integration tests are also provided. There is a folder full of test data at: /group_workspaces/jasmin/cis/cis_repo_test_files which has been compressed and is available as a tar inside that folder.

To add files to the folder simply copy them in then delete the old tar file and create a new one with:

tar --dereference -zcvf cis_repo_test_files.tar.gz .

Ignore warning about file changing - it is because the tar file is in the directory. Having the tar file in the directory, however, means the archive can be easily unpacked, without creating an intermediate folder. To make the integration tests run this needs to be copied to the local machine and decompressed. Then set the environment variable CIS_DATA_HOME to the location of the data sets, and run nosetests cis/test/integration.

There are also a number of plot tests available under the test/plot_tests directory in the test_plotting.py script. These integration tests use matplotlib to perform a byte-wise comparision of the output against reference plots, using a pre-defined tolerance. Any tests which fail can be evaluated using the idiff.py tool in the same directory. Running this will present a graphical interface showing the reference plot, the test output, and the difference between them. You can either choose to accept the difference which will move the test output to the reference directory, or reject it.

Dependencies¶

A graph representing the dependency tree can be found at doc/cis_dependency.dot (use XDot to read it)

Creating a Release¶

To carry out intermediate releases follow this procedure:

1. Check the version number and status is updated in the CIS source code (cis/__init__.py)
2. Tag the new version on Github with new version number and release notes.
3. Create a tarball - use python setup.py egg_info sdist in the cis root dir.
4. Install this onto the release virtual environment: this is at /group_workspaces/jasmin/cis/cis_dev_venv. So activate the venv, upload the tarball somewhere on the GWS and then do pip install <LOCATION_OF_TARBALL>.
5. Create an anaconda build on each platform (OS X, Linux and Windows) - see below.
6. Request Phil Kershaw upload the tarball to PyPi. (Optional)

For a release onto JASMIN, complete the steps above and then ask Alan Iwi to produce an RPM, deploy it on a test VM, confirm functionality then rollout across full JAP and LOTUS nodes.

$ conda build -c cistools -c scitools cis

$ binstar upload <package_location> -u cistools

$ binstar upload <package_location> -u cistools --channel beta

$ conda install -c https://conda.binstar.org/cistools/channel/beta -c cistools -c scitools cis

Documentation¶

The documentation and API reference are both generated using a mixture of markdown and autogenerated documentation using the Sphinx autodoc package. Build the documentation using:

python setup.py build_sphinx

This will output the documentation in html under the directory doc/_build/html.

Continuous Integration Server¶

JASMIN provide a Jenkins CI Server on which the CIS unit and integration tests are run whenever origin/master is updated. The integration tests take approximately 7 hours to run whilst the unit tests take about 5s. The Jenkins server is hosted on jasmin-sci1-dev at /var/lib/jenkins and is accessed at http://jasmin-sci1-dev.ceda.ac.uk:8080/

We also have a Travis cloud instance (https://travis-ci.org/cedadev/cis) which in principle allows us to build and test on both Linux and OS X. There are unit test builds currently working but because of a hard time limit on builds (120 minutes) the integration tests don’t currently run.

Main API¶

As a command line tool, CIS has not been designed with a python API in mind. There are however some utility functions that may provide a useful start for those who wish to use CIS as a python library. For example, the functions in the base cis module provide a straightforward way to load your data. They can be easily import using, for example: from cis import read_data. One of the advantages of using CIS as a Python library is that you are able to perform multiple operations in one go, that is without writing to disk in between. In certain cases this may provide a significant speed-up.

The read_data() function is a simple way to read a single gridded or ungridded data object (e.g. a NetCDF variable) from one or more files. CIS will determine the best way to interpret the datafile by comparing the file signature with the built-in data reading plugins and any user defined plugins. Specifying a particular product allows the user to override this automatic detection.

cis.read_data(filenames, variable, product=None)¶

Read a specific variable from a list of files Files can be either gridded or ungridded but not a mix of both. First tries to read data as gridded, if that fails, tries as ungridded.

Parameters:

filenames (string or list) – The filenames of the files to read. This can be either a single filename as a string, a comma separated list, or a list of string filenames. Filenames can include directories which will be expanded to include all files in that directory, or wildcards such as * or ?. variable (str) – The variable to read from the files product (str) – The name of the data reading plugin to use to read the data (e.g. Cloud_CCI).

Returns:

The specified data as either a GriddedData or UngriddedData object.

The read_data_list() function is very similar to read_data() except that it allows the user to specify more than one variable name. This function returns a list of data objects, either all of which will be gridded, or all ungridded, but not a mix. For ungridded data lists it is assumed that all objects share the same coordinates.

cis.read_data_list(filenames, variables, product=None, aliases=None)¶

Read multiple data objects from a list of files. Files can be either gridded or ungridded but not a mix of both.

Parameters:

filenames (string or list) – The filenames of the files to read. This can be either a single filename as a string, a comma separated list, or a list of string filenames. Filenames can include directories which will be expanded to include all files in that directory, or wildcards such as * or ?. variables (string or list) – One or more variables to read from the files product (str) – The name of the data reading plugin to use to read the data (e.g. Cloud_CCI). aliases (string or list) – List of aliases to put on each variable’s data object as an alternative means of identifying them.

Returns:

A list of the data read out (either a GriddedDataList or UngriddedDataList depending on the type of data contained in the files)

Unsupported API¶