TOSTI - Tool for Orbital Spatial and Temporal Interpolation

Arjo Segers

Contents

• Introduction
• Running
• TOSTI files
  • Input files
  • Output files
  • Tar files
  • Input preferences
  
  
• Rc files
• Installed TOSTI's
• Source package
• Meteo archives
  • ECMWF meteo
  • TM5 meteo
  
  
• Pressure levels

Introduction

TOSTI is a tool to provide ECMWF meteo data on the footprints of satellite orbits.

Running

A typical way to run TOSTI is the following:

1. Create a tosti hdf file with lon/lat/time specifications.
    
2. Create a rc file with settings for the run, for example the name of the previously created lon/lat/time file, and the name of the output file to be crated.
    
3. Run the tosti script with the rcfile as argument:

   > $HOME/bin/tosti your-tosti.rc

   Use the full pathname to call the script !
   See section installed TOSTI's for locations of installed tosti scripts.

TOSTI files

Input files

A TOSTI file is a HDF4 file that is used for input/output. Read/write routines are available:

• Fortran90
• IDL

For input, the file contains the following data sets:

• longitude (degree)
• latitude (degree)
• time (year,month,day,hour,minute,second)

NOTE: In older TOSTI versions the user was forced to supply a character key (80 chars); this is not necessary anymore.

A sample input file is available: data/scia-ol-ap04_points.hdf

Output files

TOSTI creates an output as a copy of the input, with a postfix added to the file name. Then, extra data sets are added for the requested meteo (defined in the rcfile).

Tar files

Input files can be collected into tar files; the output files are then collected too.

Input preferences

In order of most prefered, the following type of inputs could be used:

1. A single hdf file containing points for one complete day (multiple orbits).
2. Multiple hdf files each covering a part of a day (1 orbit ?); the files for a complete day are collected in a tar file.

Rc files

A 'rc file' (resource file) is a text file with settings for a run.

A sample rcfile is available in the source as rcfiles/tosti_rc . Copy this file and modify it for your personal purpose.

Installed TOSTI's

The TOSTI scripts and executable is installed at KNMI, since the meteo data is stored on the MOS tape archive. If you do no have access to the KNMI systems, send the input files and other info to a colleague who has access, AND is willing to help you ...

• Running TOSTI on the SUN:

  /usr/people/segers/pub/bin/tosti your-tosti.rc

• Running TOSTI on the Linux work stations:

  /net/bsgi59/usr/people/segers/pub/bin/tosti your-tosti.rc

Source package

Colleagues with a codex account with membership for the 'TM' group can checkout the TOSTI sources the cvs repository. If you do not know what what this means, sorry for you ...

cvs -d :ext:you@codex.knmi.nl:/cvs/TM checkout tosti

TOSTI should be linked with:

• HDF4 libraries (from /usr/local/free)
• The TMkit libraries. Pre-compiled libraries are available in:
  • /net/bsgi59/usr/people/segers/opt/ifort/         (Linux workstations, IFort compiler)
  • /usr/people/segers/segers/opt/SUNS8/         (SUN)
  You might need to change 'src/Makefile' for personal settings.
  TM users could checkout the TMkit sources from the codex.
  See also TMkit manual.

Meteo archives

Meteo is either extracted from the ECMWF archive or from the TM5 archive. Which archive is used is determined by 'tmm.sourcekey' in the rcfile.

ECMWF meteo

Use the following setting in the rcfile:

tmm.sourcekey : grib:od-fc-ml60-glb

To extract meteo from the ECMWF archive, it is necessary to include global attributes in the tosti input specifying the forecast start time and the horizontal resolution:

• ecfcstart=[2004,12,31,12,00,00]
  The ecmwf meteo used for TOSTI is extracted from the 10-days forecasts. These forecast are always started at 12:00, the first field in the archive is valid 3 hours later. Currently, fields are available at 3 hour resolution for the first 3 days, dus hours [15,18,21,..,69,72] . For orbits with pixels valid for 01-01-2005, the best choice for the forecast start is thus 31-12-2004 12:00 .
  Note that orbits may cross the date-boundary. To have all meteo extracted from a single forecast for the complete orbit, set, in the previous example, the forecast start to 31-12-2004 12:00 for all oribits with pixels valid in [31-12-2004 21:00,2-1-2005 3:00].
  Algorithm:
  1. determine the time interval covered by the pixels in an orbit;
  2. deceide in which day (from 0:00 to 24:00) this interval should be;
  3. the forecast start is previous day 12:00 .
  Note: TOSTI's author does not want to deceide on point 2, therefore the user should specify the forecast start ...
• eclonres=0.5, eclatres=0.5
  Fields are extracted as regular lat/lon fields on the requested resolution, and then interpolated to the requested points.

In IDL, use routine TOSTI_WriteSourceInfo from file_tosti.pro to write the the ECMWF attributes to the input file.

TM5 meteo

Use the following setting in the rcfile:

tmm.sourcekey : tmppS:od-fc-ml60-glb3x2

TOSTI extracts meteo not directly from ECMWF but from the TM model archive. The input for TM consists of ECMWF data gridded on 3x2 deg resolution. Available at KNMI are:

• operational data 2000-now
• era40 data 1995-2002

Pressure levels

The output meteo is defined on ECMWF's hybride sigma-pressure levels. The atmosphere up to 0.1 hPa is devided into 60 layers or 'full' levels ; the interfaces between the layers are called 'half' levels. Pressures can be computed from the surface pressure and the hybride coefficients provided as global attributes in the TOSTI output:

$$phalf = halflevel\_coef\_a +  halflevel\_coef\_b *  psurf$$ (1)

$$pfull = fulllevel\_coef\_a +  fulllevel\_coef\_b *  psurf$$ (2)

$$dp = fulllevel\_coef\_da +  fulllevel\_coef\_db *  psurf$$ (3)

NOTE: ECMWF defines the pressure levels from top-to-surface (increasing pressure), but TOSTI uses the reverse (surface-to-top, decreasing pressure) which is the definition used in the TM models.