FlexExtract

Description

FlexExtract.jl is a package interfacing the flex_extract program in Julia, allowing to retrieve and prepare the ECMWF input meteorological data for the FLEXPART Lagrangian atmospheric dispersion model.

Installation

The package is not registered, so you need to install it with:

using Pkg; Pkg.add(url="https://github.com/tcarion/FlexExtract.jl")

If you have no pre-existing Conda installation, you might get the following error:

[ Info: Precompiling FlexExtract [5ad5ba56-8ec2-41bb-8b56-2065914898b5]
ERROR: LoadError: InitError: PyError (PyImport_ImportModule

The Python package ecmwfapi could not be imported by pyimport. Usually this means
that you did not install ecmwfapi in the Python version being used by PyCall.

The simplest way to overcome this is to configure PyCall to use a Julia-specific Python distribution. To do that:

ENV["PYTHON"] = ""
using Pkg
Pkg.build("PyCall")

Then restart julia, and you should be to import FlexExtract without error.

Getting started

First, create a default FlexExtract directory in the current directory:

using FlexExtract
FlexExtract.create("testfe")

This will create a new directory called testfe with two subdirectories input and output, as well as a default control file (see the flex_extract documentation for more info about the control file). To check the values of the control file in Julia, type:

julia> fcontrol = FeControl(fedir)
OrderedCollections.OrderedDict{Symbol, Any} with 18 entries:
  :START_DATE => "20180809"
  :DTIME      => "1"
  :TYPE       => "AN FC FC FC FC FC FC FC FC FC FC FC AN FC FC FC FC FC FC FC FC FC FC FC"
  :TIME       => "00 00 00 00 00 00 00 00 00 00 00 00 12 12 12 12 12 12 12 12 12 12 12 12"
  :STEP       => "00 01 02 03 04 05 06 07 08 09 10 11 00 01 02 03 04 05 06 07 08 09 10 11"
  :CLASS      => "OD"
  :STREAM     => "OPER"
  :GRID       => "0.2  "
  :LEFT       => "-10."
  :LOWER      => "30."
  :UPPER      => "60."
  :RIGHT      => "30."
  :LEVEL      => "137"
  :RESOL      => "799"
  :ETA        => "1"
  :FORMAT     => "GRIB2"
  :PREFIX     => "ENH"
  :ECTRANS    => "1"

You can change any paraemeters with setindex!. You then need to write the modified values to the file with FlexExtract.save:

fcontrol[:GRID] = 0.5
FlexExtract.save(fcontrol)

After the parameters have been set, you can send the request to ECMWF servers via:

FlexExtract.submit(fedir)