Difference between revisions of "GAMAP tips and tricks"

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== Date and time ==
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On this page we list information about GAMAP, the Global Atmospheric Model Analysis Package. 
  
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Hi Inna,
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== Overview ==
  
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One thing....CALDAT converts an astronomical Julian Day back to month/day/year.  Astronomical Julian Day starts on Jan 1, 4713BC.  It's used to compute intervals between widely-separated dates.
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GAMAP
  
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I think you may be referring to Julian day as the "day since the 1st of the year", as Julian day can also refer to that.
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* is a self-contained, consistent, and user-friendly software package for reading and visualizing output from chemical tracer models (CTM's)
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* consists of a suite of routines written in IDL (Interactive Data Language)
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* makes extensive use of IDL's powerful plotting features
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* can produce line plots, 2D plots, 2D animations, or 3D isocontour surface plots
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* can read 2D, 3D or 4D data blocks
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* can read output from the GEOS–Chem, GISS and FSU model families
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* can be easily customized to keep pace with ongoing model development
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* can be installed on any platform that supports IDL, thus ensuring a high degree of portability
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* can be coupled with the ION (IDL on the Net) interface to create interactive plots which can be served to a web page
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* can read data from ASCII, binary, netCDF (including COARDS conventions!), and HDF–EOS file formats
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* contains helper routines to read from / write to various file formats
  
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A quick way to compute the day of the year is w/ IDL's JULDAY function:
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The main GAMAP program contains a user-friendly, menu-driven interface; however, users may also call GAMAP subroutines independently of the main program. This makes it possible to embed GAMAP routines within existing IDL code.
  
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    Day_of_Year = Julday( Month, Day, Year ) - Julday( 1, 0, Year )
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== Table of Contents ==
  
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For example:
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=== GAMAP web pages ===
  
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    IDL> print, julday( 1, 10, 2008 ) - julday( 1, 0, 2008 )
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This page has now been split into several sub-pages:
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    % Compiled module: JULDAY.
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          10
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Julday( 1, 0, 2008 ) is essentially 12/31/2008. You use this so that you don't have to add one to the above difference. (i.e. julday( m, d, y ) - julday( 1, 1, y ) + 1 would be equivalent).
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* [http://acmg.seas.harvard.edu/gamap/ GAMAP main page]
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* [http://acmg.seas.harvard.edu/gamap/doc/index.html GAMAP Online User's Guide]
  
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This is essentially done for you in the GAMAP function ~/IDL/gamap2/day_of_year.pro.  You could replace the above code with:
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=== GAMAP tips and tricks ===
  
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    IDL> print, day_of_year( 1, 10, 2008 )
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* [[General GAMAP usage]]
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          10
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* [[File I/O with GAMAP]]
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* [[Color and graphics with GAMAP]]
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* [[Regridding with GAMAP]]
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* [[Date and time computations with GAMAP]]
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* [[Text manipulation with GAMAP ]]
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* [[Removing extraneous lines from map plots]]
  
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To do the reverse, you would have to use CALDAT but then add on the astronomical Julian day for the first of the year, for example:
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--[[User:Bmy|Bob Y.]] 09:48, 11 March 2011 (EST)
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    IDL> caldat, julday( 1, 0, 2008 )+10, y, m, d
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    IDL> print, y, m, d
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              1          10        2008
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There is another GAMAP function called ADD_DATE that essentially does this.  You can do the following:
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    ; Convert month/day/year to day of year
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    IDL> doy = day_of_year( 1, 10, 2008 )
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    IDL> print, doy
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          10
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    ; convert day of year back to month/day/year
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    IDL> print, add_date( 20080101, 10-1 )
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        20080110
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The only thing to remember is you have to subtract 1 from the day of year because the way ADD_DATE is written, it will add the # of days.  This may be a better solution for you.
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I used to be an astronomer so I am pretty familiar w/ all of these time definitions.  :-)
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Hope this helps,
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Bob Y.
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== Combining output from timeseries files ==
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'''''Ray Nassar (ray@io.as.harvard.edu) wrote:'''''
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:I just have a quick question, is there any GAMAP routine that can average all hourly data blocks in a timeseries file to make a single daily average bpch file? 
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:It appears like I could use the average option of ctm_sum.pro but I do not quite understand where the averaged data goes and afterwards would still have to write to bpch.
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'''''Philippe Le Sager (plesager@seas.harvard.edu) replied:'''''
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:Check the
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    /gamap2/timeseries/gc_combine_nd49.pro
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    /gamap2/timeseries/gc_combine_nd48.pro
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:routines, which combines daily bpch files (nd48 & nd49 output, but also met field input files) into 4D data blocks. It has many options. You can extract a subset of data according to time and/or location, or process the data (moving average, daily max, shift to local time). You can either save the data into a new bpch file or just get an array of data in output.
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:I wrote a tutorial that gives some pointers [http://www-as.harvard.edu/chemistry/trop/gamap/doc/timeseries_brief_tutorial.pdf here.]
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:-Philippe
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--[[User:Bmy|Bob Yantosca]] 09:43, 1 April 2008 (EDT)
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== Memory management and CTM_MAKE_DATAINFO ==
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When using CTM_MAKE_DATAINFO, you create few pointers and allocate memory to pointed data. Three scenarios to free that memory are possible.
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(1) By default, GAMAP keeps track of the pointers in a global structure, and you can clean up the memory by calling CTM_CLEANUP (with or without the keyword /NO_GC):
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    ctm_make_datainfo(data, ...)
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    CTM_WriteBpch, DataInfo, FileInfo, FileName=file
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    ctm_cleanup
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(2) If you use the keyword /NO_GLOBAL when calling CTM_MAKE_DATAINFO, the story is a little bit more subtle. Now, GAMAP has no idea of the created pointers. If you use CTM_CLEANUP without the keyword /NO_GC, everything is clean up because there is a call to heap_gc. But you are also loosing **all other** pointers and objects.
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    ctm_make_datainfo(data, ..., /No_global)
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    CTM_WriteBpch, DataInfo, FileInfo, FileName=file
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    ctm_cleanup
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Note if you do not call ctm_cleanup or call it with /No_GC, then the memory allocated by CTM_MAKE_DATAINFO is still allocated and the pointers that refers to it are alive... until you exit the routine (unless they are passed back). Once you are out of the routine, this memory remains allocated but is useless since unaccessible, in other words you have memory leak.
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(3) So, if you want to keep some objects and/or pointers alive in your code (i.e., you do not want to call heap_gc or ctm_cleanup,/no_gc), you need to free only the created pointers as follows:
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    ctm_make_datainfo(data, datainfo, fileinfo, ..., /No_global)
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    CTM_WriteBpch, DataInfo, FileInfo, FileName=file
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    ptr_free, DataInfo.data
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    ptr_free, fileinfo.gridinfo
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To free only the heap memory created by multiple calls to CTM_MAKE_DATAINFO, the procedure is:
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  for D=0L, NTracers-1L do begin
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      Success = CTM_Make_DataInfo( Data[*,*,D], DataInfo, FileInfo, ..., /No_Global )
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      ArrDataInfo = D eq 0l ? [ DataInfo ] : [ ArrDataInfo, DataInfo ]
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      if D ne Ntracers-1l then ptr_free, Fileinfo.gridinfo
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  endfor
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  CTM_WriteBpch, ArrDataInfo, FileInfo, FileName=OutFileName
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  for d=0, n_elements(ArrDataInfo)-1l do ptr_free, ArrDataInfo[d].data
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  ptr_free, fileinfo.gridinfo
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--[[User:Phs|Philippe Le Sager]] 10:28, 13 February 2008
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Revision as of 14:49, 11 March 2011

On this page we list information about GAMAP, the Global Atmospheric Model Analysis Package.

Overview

GAMAP

  • is a self-contained, consistent, and user-friendly software package for reading and visualizing output from chemical tracer models (CTM's)
  • consists of a suite of routines written in IDL (Interactive Data Language)
  • makes extensive use of IDL's powerful plotting features
  • can produce line plots, 2D plots, 2D animations, or 3D isocontour surface plots
  • can read 2D, 3D or 4D data blocks
  • can read output from the GEOS–Chem, GISS and FSU model families
  • can be easily customized to keep pace with ongoing model development
  • can be installed on any platform that supports IDL, thus ensuring a high degree of portability
  • can be coupled with the ION (IDL on the Net) interface to create interactive plots which can be served to a web page
  • can read data from ASCII, binary, netCDF (including COARDS conventions!), and HDF–EOS file formats
  • contains helper routines to read from / write to various file formats

The main GAMAP program contains a user-friendly, menu-driven interface; however, users may also call GAMAP subroutines independently of the main program. This makes it possible to embed GAMAP routines within existing IDL code.

Table of Contents

GAMAP web pages

This page has now been split into several sub-pages:

GAMAP tips and tricks

--Bob Y. 09:48, 11 March 2011 (EST)

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