MARS
Specifies the output grid which can be either a Gaussian or a Latitude/Longitude grid.
grid=<value> |
---|
MARS requests specifying grid=av
will return the archived model grid. For Latitude/Longitude output, the format is in degrees, i.e. grid = 2.5/2.5, where the first number denotes the east-west resolution (longitude) and the second denotes the north-south resolution (latitude). The grid spacing needs to be an integer fraction of 90 degrees (latitude range from the Equator to the Pole), e.g. 0.225, 0.25, 0.28125, 0.3, 0.4, ...
Output on a Gaussian grid is specified by a letter denoting the type of Gaussian grid followed by an integer (the grid number) representing the number of lines between the Pole and Equator, e.g.
grid = F160
- full (or regular) Gaussian grid with 160 latitude lines between the pole and equatorgrid = N320
- ECMWF original reduced Gaussian grid with 320 latitude lines between the pole and equator, see Reduced Gaussian Grids for grid numbers used at ECMWFgrid = O640
- ECMWF octahedral (reduced) Gaussian grid with 640 latitude lines between the pole and equator
Not all grid names and grid number combinations are supported. Currently, the Gaussian grid names and numbers supported for MARS retrievals are:
Octahedral reduced Gaussian (O grids) | O1280 | O640 | O512 | O400 | O320 | O256 | O200 | O160 | O128 | O96 | O64 | O48 | O32 |
Original reduced Gaussian (N grids) | N640 | N512 | N400 | N320 | N256 | N200 | N160 | N128 | N96 | N64 | N48 | N32 | |
Regular (Full) Gaussian (F grids) | F1280 | F640 | F512 | F400 | F320 | F256 | F200 | F160 | F128 | F96 | F64 | F48 | F32 |
MARS requests specifying an unsupported grid will fail. For example, a retrieval request with grid=O123
will return an error. If the letter denoting the type of Gaussian grid is omitted, e.g. grid=320
, a full (or regular) Gaussian grid with 320 grid lines is returned.
Examples
|
Dissemination
Specifies the output grid which can be either a Gaussian or a Latitude/Longitude grid.
grid=<value> |
---|
Products on latitude-longitude grids are interpolated from the spectral or (quasi regular - reduced) Gaussian grid associated with the ECMWF forecast model. Interpolation is made to a 0.125 degree latitude-longitude grid and resulting products are generated by selecting required points. Regular Gaussian grids are also available. Where appropriate, the interpolation to a latitude-longitude grid uses a land/sea mask so that an interpolated land point is assigned a value calculated using only neighbouring land grid points, and an interpolated sea point is assigned a value using only neighbouring sea grid points. For precipitation fields, the interpolation assigns a zero value if the value at the nearest grid point is zero; also any value within one per cent of the global minimum for the field is taken to be equal to zero.
Products on polar stereographic grids are interpolated from the 0.125 degree latitude-longitude interpolated fields; thus they are subject to a double interpolation error.