中国地区被动微波SMMR亮度温度数据集（1978-1987）

本数据集主要包含Nimbus-7卫星携带的扫描式多通道微波辐射计（SMMR：Scanning Multichannel Microwave Radiometer）获得的被动微波亮度温度，包含1978年10月25日-1987年8月20日的06H、06V、10H、10V、18H、18V、21H、21V、37H、37V共十个微波通道的每天两次过境（升轨&降轨）亮度温度，其中H代表水平极化，V代表垂直极化。
1978年10月发射的Nimbus-7为太阳同步极轨卫星，搭载的微波传感器SMMR，是一台测量地表五个频率（6.6GHz，10.69GHz，18.0GHz，21.0GHz，37.0GHz）微波亮温的双极化微波辐射计。它以约50.3°固定入射角扫描地表，幅宽780km，并在正午12：00（升轨）与午夜24：00（降轨）通过赤道。SMMR时间分辨率为每日，但由于swath间距离较宽，大概每隔5-6天才会重访同一地表。
1、文件格式和命名：
每组数据均由遥感数据文件构成。
SMMR_Grid_China目录下的每组数据文件名及命名规则如下：
SMMR-MLyyyydddA/D.subset.ccH/V（遥感数据）
其中：SMMR代表SMMR传感器；ML代表多通道低分辨率；yyyy代表年份；ddd代表该年的儒略日（1-365/366）；A/D分别代表升轨（A）和降轨（D）；subset表示中国地区的亮温数据；cc代表频率（6.6GHz，10.69GHz，18.0GHz，21.0GHz，37.0GHz）；H/V分别代表水平极化（H）和垂直极化（V）。
2、坐标系及投影：
投影方式为等积割圆柱投影，双标准纬线为南北纬30度。有关EASE-GRID的相关详细信息，请参考http://www.ncgia.ucsb.edu/globalgrids-book/ease_grid/。
如果需要将EASE-Grid投影方式转换成Geographic投影方式，请参照ease2geo.prj文件，内容如下：
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、数据格式：
以整数形二进制存储，每个数据占2个字节。本数据集中实际存储的数据为亮温*10，读出数据后需除以10得到真实亮温。
空间分辨率：25km；
时间分辨率：逐日，从1978年至1987年。
4、空间范围：
经度：60.1°-140.0°东经；
纬度：14.9°-55.0°北纬。
5、数据读取
每一组数据的遥感影像数据文件可以在ENVI和ERDAS软件中打开。

This dataset primarily contains passive microwave brightness temperatures acquired by the Scanning Multichannel Microwave Radiometer (SMMR) onboard the Nimbus-7 satellite. The data includes brightness temperatures from two daily overpasses (ascending and descending orbits) across 10 microwave channels: 06H, 06V, 10H, 10V, 18H, 18V, 21H, 21V, 37H, and 37V, from October 25, 1978 to August 20, 1987, where H represents horizontal polarization and V represents vertical polarization.

Launched in October 1978, Nimbus-7 is a Sun-synchronous polar-orbiting satellite. Its onboard SMMR is a dual-polarization microwave radiometer that measures microwave brightness temperatures at five surface frequencies: 6.6 GHz, 10.69 GHz, 18.0 GHz, 21.0 GHz, and 37.0 GHz. It scans the surface at a fixed incidence angle of approximately 50.3°, with a swath width of 780 km, and crosses the equator at approximately 12:00 noon (ascending orbit) and 24:00 midnight (descending orbit). The temporal resolution of SMMR is daily, but due to the wide spacing between swaths, it revisits the same surface approximately every 5-6 days.

1. File Format and Naming:
Each dataset consists of remote sensing data files.
The naming convention for datasets under the SMMR_Grid_China directory is as follows:
SMMR-MLyyyydddA/D.subset.ccH/V (remote sensing data)
Where: SMMR represents the SMMR sensor; ML stands for multi-channel low-resolution; yyyy is the 4-digit year; ddd is the Julian day of the year (1-365/366); A/D represent ascending (A) and descending (D) orbits respectively; subset indicates brightness temperature data for the Chinese region; cc represents the frequency band (6.6 GHz, 10.69 GHz, 18.0 GHz, 21.0 GHz, 37.0 GHz); H/V represent horizontal polarization (H) and vertical polarization (V) respectively.

2. Coordinate System and Projection:
The projection uses the equal-area cylindrical secant projection, with two standard parallels at 30° north and south latitudes. For detailed 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 of which 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:
The data is stored as integer binary, with 2 bytes per data point. The actual stored data in this dataset is the brightness temperature multiplied by 10; divide the read value by 10 to obtain the true brightness temperature.
Spatial resolution: 25 km;
Temporal resolution: Daily, from 1978 to 1987.

4. Spatial Extent:
Longitude: 60.1°E – 140.0°E;
Latitude: 14.9°N – 55.0°N.

5. Data Reading
Each set of remote sensing image data files can be opened in ENVI and ERDAS software.

搜集汇总

背景与挑战

背景概述

该数据集包含1978年至1987年中国地区的被动微波SMMR亮度温度数据，来源于Nimbus-7卫星的SMMR传感器，提供十个微波通道的每天两次过境（升轨和降轨）数据，包括水平极化和垂直极化。数据具有日时间分辨率和10km-100km空间分辨率，适用于冰冻圈遥感和微波遥感应用。