> What meteorological fields are needed for HYSPLIT to properly calculate trajectories?
I will be converting ECMWF grib files into ARL-packed format for use in calculating
backward trajectories in Europe using your Hysplit model. What fields do I need
to have for HYSPLIT to properly calculate my trajectories?
Preparing input data for Hysplit can be very challenging task. You need to understand the
structure of the data that you will be using to convert for input to the model. At a minimum
Hysplit requires U,V,W,T , (RH or Q optional), at various model sigma levels, or if the input date
are on pressure levels then the geopotential height at each level. At the surface either surface
pressure or terrain height are required, all other variables are optional (e.g. 10 meter winds, 2 m
temperature).
You should examine the sample ECMWF data converter program (ecm2arl.f) supplied with the PC
distribution in the \data2arl\ecmwf directory. It will require some modification to match the data
you obtain, but it does show various vertical level options and lists the grib variable
identification numbers for the various variables used by the model. Further when you run the
program you need to define the limits of a conformal map. ECMWF data are usually provided at
latitude-longitude points, the program interpolates these to a polar stereographic, lambert
conformal, or mercator projection. You need to specify the location, resolution, and domain limits
for this grid.
Additonal subroutines that you will need can be found in the \data2arl\source and \metdata\source
directories. You will also need the GRIBEX program and associated libraries from ECMWF to read
their grib files.