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This dataset mainly includes the passive microwave brightness temperature obtained from the Scanning Multichannel Microwave Radiometer (SMMR) carried by the Nimbus-7 satellite, including 06H, 06V, 10H, 10V, 18H, 18V, 21H, 21V, 37H, 37V, a total of ten microwave channels with two transits (ascending & descending) brightness temperature per day from October 25, 1978 to August 20, 1987, where H represents horizontal polarization and V represents vertical polarization.

Nimbus-7, launched in October 1978, is a solar-synchronous polar-orbiting satellite. The microwave sensor SMMR is a dual-polarization microwave radiometer that measures the brightness temperature of five frequencies (6.6GHz, 10.69GHz, 18.0GHz, 21.0GHz, 37.0GHz) on the surface. It scans the surface at a fixed incident angle of about 50.3 °, with a width of 780 km, and passes through the equator at noon 12:00 (ascending orbit) and 24:00 (descending orbit). The time resolution of SMMR is daily, but due to the wide distance between swaths, the same surface will be revisited every 5-6 days.

1. File format and naming:

Each set of data is composed of remote sensing data files.

The name and naming rules of each group of data files in the SMMR_Grid_China directory are as follows:

SMMR-MLyyyydddA / D.subset.ccH / V (remote sensing data)

Among them: SMMR stands for SMMR sensor; ML stands for multi-channel low resolution; yyyy stands for year; ddd stands for Julian Day of the year (1-365 / 366); A / D stands for ascending (A) and derailing (D ); subset represents the brightness temperature data in China; cc represents the frequency (6.6GHz, 10.69GHz, 18.0GHz, 21.0GHz, 37.0GHz); H / V represents horizontal polarization (H) and vertical polarization (V).

2. Coordinate system and projection:

The projection method is an equal area secant cylindrical projection, and the double standard parallels are 30 degrees north and south. For more information about EASE-GRID, please refer to http://www.ncgia.ucsb.edu/globalgrids-book/ease_grid/.

If you need to convert the EASE-Grid projection to Geographic projection, please refer to the ease2geo.prj file, the content is as follows:

Input

projection cylindrical

units meters

parameters 6371228 6371228

1 / * Enter projection type (1, 2, or 3)

0 00 00 / * Longitude of central meridian

30 00 00 / * Latitude of standard parallel

Output

Projection GEOGRAPHIC

Spheroid KRASovsky

Units dd

parameters

end

3. Data format:

Stored as integer binary, each data occupies 2 bytes. The actual data stored in this dataset is the brightness temperature * 10. After reading the data, you need to divide by 10 to get the real brightness temperature.

Spatial resolution: 25km;

Time resolution: daily, from 1978 to 1987.

4. Spatial range:

Longitude: 60.1 ° -140.0 ° East longitude;

Latitude: 14.9 ° -55.0 ° north latitude.

5. Data reading

Remote sensing image data files for each set of data can be opened in ENVI and ERDAS software.