China's SMMR data set mainly uses the microwave brightness temperature (TB) data obtained by scanning multichannel microwave radiometer (SMMR) carried by nimbus-7 satellite. It includes the brightness temperature of 06h, 06v, 10h, 10V, 18h, 18V, 21h, 21V, 37h and 37V channels from 1978 to 1987. H represents horizontal polarization and V represents vertical polarization.

The nimbus-7 solar synchronous polar orbit satellite, launched in October 1978, is a dual polarization microwave radiometer with five frequencies and ten channels for measuring surface radiation, which is equipped with a microwave sensor SMMR. It scans the earth's surface at a fixed angle of incidence of about 50.3 ° with a width of 780km and passes through the equator at 12:00 noon (ascending orbit) and 24:00 midnight (descending orbit). The time resolution of SMMR is daily, but the same surface is revisited every 5-6 days. The characteristic values are shown in the table below.

Some eigenvalues of SMMR

Channel frequency (GHz) spatial resolution (km) temperature resolution (k) antenna wave velocity width (DEG)

37V/H 37.00 30 1.5 0.8

21V/H 21.00 60 1.5 1.4

18V/H 18.00 60 1.2 1.6

10V/H 10.69 97.5 0.9 2.6

6V/H 6.60 156 0.9 4.2

1. File format and naming:

Each group of data consists of remote sensing data file,. JPG image file,. Met auxiliary information file,. Tim time information file and corresponding. Met auxiliary time information file.

The file names and naming rules of each group of data under SMMR grid China directory are as follows:

China-ease-n07-ml / haaaabbba / d.cch/v (remote sensing data) china-ease-n07-ml / haaaabbba / d.cch/v.jpg (image file)

China-ease-n07-ml / haaaabbba / d.cch/v.met (auxiliary information file)

China-ease-n07-ml / haaaabbba / d.tim (time information file) china-ease-n07-ml / haaaabbba / d.tim.met (time information auxiliary file).

2. Coordinate system and projection:

The projection mode is equal product cutting cylinder projection, and the double standard latitude is 30 degrees of North-South latitude. 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 mode to the geographic projection mode, please refer to the ease2geo.prj file, 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:

It is stored as an integer binary, and each data takes up 2 bytes. The actual stored data in this data set is light temperature * 10. After reading out the data, divide by 10 to get the real light temperature.

Spatial resolution: 25km, 12.5km (SSM / I 85ghz)

Time resolution: day by day, from 1978 to 2007.

4. Space range:

Longitude: 60 ° - 140 ° east longitude

Latitude: 15 ° - 55 ° north latitude.

5. Data reading

Each group of data includes remote sensing image data file,. JPG image file and. Met auxiliary information file. JPG file can be opened with windows picture and Fax Viewer,. Met auxiliary information file can be opened with Notepad, remote sensing image data file can be opened in ENVI and ERDAS software.