This icon converts GRIB data into format required by the VAPOR 3D visualisation system.
The macro language equivalent is vapor_prepare().
About FLEXTRA input data
FLEXTRA requires input fields on a regular latitude-longitude grid in GRIB format. The input data must contain four three-dimensional fields: the two horizontal wind components, vertical velocity and temperature. Two additional two-dimensional fields are needed as well: topography and surface pressure. 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 FLEXTRA 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 FLEXTRA 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 (FLEXTRA Prepare does it for you).
FLEXTRA requires all the input GRIB files to be in the same folder using the following file naming convention: ENyymmddhh. In addition to the GRIBs FLEXTRA needs several parameter files as well. Most of these files are automatically generated by Metview in the background, so users do not need to create them. The only exception is the file called AVAILABLE because it can be optionally provided by the user.
The VAPOR Prepare Editor
Vapor Input Mode
Specifies the data input mode. The possible values are: Icon and Path. The default value is Icon.
In Icon mode a set of GRIB icons has to be specified in Vapor Input Data. If the mode is set to Path the input data is read from a specified path on the filesystem (yet to be implemented).
Vapor Input Data
Specifies the input data as a set of GRIB icons. It is available when Vapor Input Mode is Icon.
Vapor 2d Params
Specifies the list of 2D parameters from the input data to be converted into VAPOR format. The parameters are identified by their short names. The default value is an empty string.
Vapor 3d Params
Specifies the list of 3D parameters from the input data to be converted into VAPOR format. The parameters are identified by their short names. The default value is an empty string.
Vapor Vertical Grid Type
Specifies the type of the 3D data to be used in VAPOR. The possible values are: Layered and Regular. The default value is Layered.
If the type is set to Layered VAPOR expects a parameter specifying the elevation of each 3D level in the input data. This is typically the case for pressure or model level (η levels) input data.
For the Regular type the
Vapor Elevation Param
Specifies the short name of the 3D parameter interpreted as the elevation of the 3D levels. Available when Vapor Vertical Grid Type is Layered.
This parameter has to be either the height or the geopotential (z) of the levels. If geopotential is specified it is converted into metres by Metview for Vapor. The default value is z.
Derive eleveation for model levels
Please note that neither the height nor the geopotential of model levels are archived in MARS. It means that for model level data either of these fields has to be computed for Layered mode. These computations can be done internally in VAPOR Prepare by simply specifying z for Vapor Elevation Param. The computations can only be done if the input data contains temperature (t) and specific humidity (q) on model levels and geopotential (z) and logarithm of surface pressure (lnsp) on the bottommost model level.
Vapor Bottom Coordinate
The name of the upper level GRIB parameter interpreted as the elevation of the upper levels. Available when Vapor Vertical Grid Type is Layered.
Vapor Top Coordinate
The name of the upper level GRIB parameter interpreted as the elevation of the upper levels. Available when Vapor Vertical Grid Type is Layered.
Vapor Area Selection
Specifies the area selection mode. The possible values are: Native and Interpolate. The default value is Native.
If it is set to Native the whole area of the input data is converted into VAPOR format. While if it is set to Interpolate the input data is interpolated to a specific grid and area.
Vapor Area
Specifies the area of the output grid in south/west/north/east format. The default value is -90/-180/90/180. Available when Vapor Area Selection is Interpolate.
Vapor Grid
Specifies the resolution of the output grid in dx/dy format, where dx is the grid increment in east-west direction, while dy is the grid increment in north-south direction (both in degrees units). The default value is: 1/1. Available when Vapor Area Selection is Interpolate.
Vapor Refinement Level
This option specifies the number of refinement levels in a VAPOR data approximation hierarchy. Starting with the native grid resolution, each successive level in the hierarchy is a factor of two smaller along each dimension. If level is 0 no hiearchy will be created (all data will be stored at their native resolution). If level is 1 a single approximation will be created, thus the hierarchy will have two levels: the native grid resolution, and the first approximation. And so on.
The default value is: 2.
Vapor Vdf Name
Specifies the name of the resulting VDF file (the .vdf suffix is automatically appended to the filename). The default value is an empty string.
Vapor Output Path
Specifies the output directory (it has to be an absolute path) where the VDF file and VDC directory hierarchy will be generated. If this directory does not exist Metview will create it. The default value is an empty string.
Vapor Reuse Input
If this parameter is set On FLEXTRA Prepare checks the existence of the data files to be generated and if they are already in place no new data is retrieved and processed. If it is Off all the fields are always processed and the existing data files are overwritten.