- pysteps.io.importers.import_mrms_grib(filename, extent=None, window_size=4, **kwargs)#
Importer for NSSL’s Multi-Radar/Multi-Sensor System ([MRMS](https://www.nssl.noaa.gov/projects/mrms/)) rainrate product (grib format).
The rainrate values are expressed in mm/h, and the dimensions of the data array are [latitude, longitude]. The first grid point (0,0) corresponds to the upper left corner of the domain, while (last i, last j) denote the lower right corner.
Due to the large size of the dataset (3500 x 7000), a float32 type is used by default to reduce the memory footprint. However, be aware that when this array is passed to a pystep function, it may be converted to double precision, doubling the memory footprint. To change the precision of the data, use the
Also, by default, the original data is downscaled by 4 (resulting in a ~4 km grid spacing). In case that the original grid spacing is needed, use
window_size=1. But be aware that a single composite in double precipitation will require 186 Mb of memory.
Finally, if desired, the precipitation data can be extracted over a sub region of the full domain using the extent keyword. By default, the entire domain is returned.
In the MRMS grib files, “-3” is used to represent “No Coverage” or “Missing data”. However, in this reader replace those values by the value specified in the fillna argument (NaN by default).
Note that “missing values” are not the same as “no precipitation” values. Missing values indicates regions with no valid measures. While zero precipitation indicates regions with valid measurements, but with no precipitation detected.
filename (str) – Name of the file to import.
extent (None or array-like) – Longitude and latitude range (in degrees) of the data to be retrieved. (min_lon, max_lon, min_lat, max_lat). By default (None), the entire domain is retrieved. The extent can be in any form that can be converted to a flat array of 4 elements array (e.g., lists or tuples).
window_size (array_like or int) – Array containing down-sampling integer factor along each axis. If an integer value is given, the same block shape is used for all the image dimensions. Default: window_size=4.
dtype (str) – Data-type to which the array is cast. Valid values: “float32”, “float64”, “single”, and “double”.
fillna (float or np.nan) – Value used to represent the missing data (“No Coverage”). By default, np.nan is used.
precipitation (2D array, float32) – Precipitation field in mm/h. The dimensions are [latitude, longitude]. The first grid point (0,0) corresponds to the upper left corner of the domain, while (last i, last j) denote the lower right corner.
quality (None) – Not implement.
metadata (dict) – Associated metadata (pixel sizes, map projections, etc.).