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With this icon we can recreate the layers of the ecCharts web-based visualisation system in the Metview environment. The icon retrieves and the data making up an ecCharts layer for the selected date from the MARS archive then applies the required post-processing steps and visualises it the result using one of the pre-defined ecCharts styles.

Execute: retrives the data from the MARS archive

Output format

Please note that the output of the icon is not a single GRIB file but a list of the following items:

1. the GRIB fields retrieved from MARS
   
2. a plot title definition (see Text plotting icon)
   
3. a contouring definition (see Contouring icon) using the specified the pre-defined style associated with the layer
4. a legend (see Legend icon) definition
   

Saving GRIB data

To save a local copy of the retrieved GRIB data use the Save result action from the icon context menu.

Generating script code

The icon is equipped with the Generate Macro and Generate Python context menu actions. With these actions the actual retrieval, post-processing and visualisation steps can be saved into the specified script format (the generated script will be appear in the current folder). Here is an example of

# Metview Macro

#  **************************** LICENSE START ***********************************
# 
#  Copyright 2018 ECMWF. This software is distributed under the terms
#  of the Apache License version 2.0. In applying this license, ECMWF does not
#  waive the privileges and immunities granted to it by virtue of its status as
#  an Intergovernmental Organization or submit itself to any jurisdiction.
# 
#  ***************************** LICENSE END ************************************
# 

# Retrieve data from MARS

data = retrieve(
    class : 'od',
    levelist : 925,
    levtype : 'pl',
    param : '130.128',
    stream : 'oper',
    type : 'fc',
    date : '20181127',
    time : '0000',
    grid : [1,1],
    step : '24',
    expver : '1')

# Define title

title = mtext(
    text_line_1 : "925 hPa temperature   START: <grib_info key='base-date' format='%d.%m.%Y. %H' where='shortName=t' /> UTC  STEP:  <grib_info key='step' where='shortName=t' />h  VALID FOR =  <grib_info key='valid-date' format='%d.%m.%Y. %H' where='shortName=t' /> UTC",
    text_colour : "charcoal")

# Define contouring
cont = mcont(
    contour_automatic_setting : "style_name",
    contour_style_name :        "sh_all_fM52t48i4",
    legend :                   "on")

# Define legend
legend = mlegend(
    legend_text_colour : "charcoal")

# Generate plot
plot(data, title, cont, legend)

What layers are available?

A fair number of eccharts layers are available.

The output of the icon

Please The output of the icons is not a single fieldset (Metviews storage type for GRIB data) but a list of these 4 elements:

1. the GRIB data (fieldset) retrieved from MARS.
   
2. a title definition (MTEXT icon)
   
3. a contouring definition (MCONT icon) using one of the pre-defined styles associated with the layer
4. a contouring legend (MLEGEND) definition
   

generates the gridded input data and the AVAILABLE file needed to run the FLEXPART Lagrangian dispersion model. The input forecast or analysis fields are either automatically retrieved from ECMWF's MARS archive or read from the specified input file. For help on editing icons, please see Editing Icons.

The macro language equivalent is eccharts().

What data is available?

Input data fields

The following is for information only - FLEXPART Prepare handles these details internally.

FLEXPART requires input fields on a regular latitude-longitude grid in GRIB format. The input data must contain five three-dimensional fields: the two horizontal wind components, vertical velocity, temperature and specific humidity. Additional surface fields (e.g. fluxes) are also needed. The three-dimensional input data has to be available on ECMWF model (i.e. η) levels defined by a hybrid vertical coordinate system. An important restriction is that all the data fields used within a FLEXPART run must have the same domain size, resolution, number of levels, etc.

All the required fields, with one exception, can be retrieved from ECMWF's MARS archive. The only exception is vertical velocity because FLEXPART needs the following field for its computations:

\dot \eta \frac{\partial \eta}{\partial p} 

Since only

\dot \eta

is archived in MARS the full product needs to be computed during the data preparation process (FLEXPART Prepare does it for you).

Input filenames

FLEXPART requires all the input GRIB files to be in the same folder using the following file naming convention: ENyymmddhh. The same directory has to contain the AVAILABLE file as well (it is automatically generated by FLEXPART Prepare).