Appraising the Direct Impacts of Aerosol on Climate

ADIENT Data Collocator

• Introduction
• Download
• Using the IDL procedure
• Using the run-time application

The purpose of the ADIENT Data Collocator is to extra satellite data along the flight track of the FAAM aircraft for a specific mission. The code uses the location and time information from FAAM core data files to define a series of points around which data is extracted from the satellite data files. At present the code is only able to read MODIS L2 files, but it will eventually be able to handle:

• MODIS L2
• GlobAEROSOL daily aerosol product files (ATSR-2, AATSR, MERIS, SEVIRI)
• MISR

The code is available as both an IDL procedure, which can be incorporated into larger IDL programmes, and a stand-alone precompiled IDL run-time (RT) application with a graphical user interface. The RT version of the tool is suitable for use with the (free to download) IDL Virtual Machine, for those without access to a licensed version of IDL.

Use the following links to download the code:

• Download IDL source code
• Download precompiled GUI application

The command line call to run the IDL procedure form of the collocator has the form:
IDL> adient_data_collocator, faam_core, modisl2=modisl2, maxdist=maxdist, maxtime=maxtime, ftime=ftime, track=track, save=save, llimit=llimit, tlimit=tlimit, modisdir=modisdir
Each of the arguments is defined as follows:

• faam_core: The location of the FAAM Core Data file corresponding to the flight of interest.
• modisl2=modisl2: A named variable into which the processed MODIS L2 data will placed. This keyword is the main return variable of the procedure.
• maxdist=maxdist: Sets the maximum spatial separation between a point along the aircraft track and a satellite pixel for the two measurements to be considered collocated. Defaults to 10 km.
• maxtime=maxtime: Sets the maximum temporal separation between a point along the aircraft track and a satellite pixel for the two measurements to be considered collocated. Defaults to 60 mins.
• ftime=ftime: Sets the temporal spacing of samples along the flight path in minutes. Defaults to 30 mins.
• track=track: On return will contain the actual points sampled from the flight path (latitude, longitude, Julian day).
• save=save: If specified, the extracted data will saved in a NetCDF file. If save is set to 1 the file will have the name "FAAM_satellite_collocated_data_nnn.nc", where nnn is the flight number of the FAAM sortie in question, otherwise the value of save will be used as a file name.
• llimit=llimit: Limits the analysis to a specified latitude-longitude box. Should be an array of this format: [min_lat, min_lon, max_lat, max_lon].
• tlimit=tlimit: Limits the analysis to a specified time period. Should be a two element array: [min_sec, max_sec] in units of seconds since the start of the day (UT).
• modisdir=modisdir: Sets the directory in which to search for MODIS L2 data. If this keyword isn't set, the code looks for the environment variable "MODIS_DIR" and if this doesn't exist, the current working directory is used.

The run-time version of the code simply provides a standalone wrapper for the procedure described above. To run the programme you will need to have either a full version of IDL, or the IDL Virtual Machine installed. To then run the code, you can either run the IDL Virtual Machine (under Linux the command is: idl -vm=adient_data_collocator_rt.sav) or, under Windows/Mac, double click the "adient_data_collocator_rt.sav" file. On running the application you should be presented with a window that resembles this:

Of course, since this is a standalone tool, the only way to output the data is via the NetCDF output file (equivalent to setting the save keyword in the procedure version.