Airborne Field Campaign Results of Ka-band Precipitation Measuring Radar in China

Spaceborne precipitation measuring radar can measure precipitation quantitatively, observe the vertical distribution and provide three dimensional precipitation structures. Spaceborne precipitation measuring radar is an important instrument on FY-3 meteorological satellite constellation. As a possible future member of the Global Precipitation Measurement (GPM), this satellite will carry dual-frequency precipitation radar operating at Ku and Ka bands to provide scientific data for dual-frequency retrieval algorithm. Its two prototype devices, Ku-band and Ka-band radars have already been developed under the support of National Defense Science and Industry Bureau. Field campaign of Ku/Ka-band airborne precipitation measuring radar is carried out by National Satellite Meteorological Center of China Meteorological Administration combining several groups from June to October in 2010 in Tianjin and Jiangsu, called BH-RM 2010 and JS-RM 2010, respectively. This is the first time that China carries out airborne precipitation measuring radar field campaign. The purposes of this field campaign are to validate the correctness of internal and external calibration scheme under airborne conditions, observe simultaneously with ground-based radar and microwave radiometer and compare satellite-airplane-ground observation data, validate the functionality and performance of precipitation measuring radar, and explore data processing and retrieval algorithms of precipitation measuring radar. Numerous data are obtained from various instruments in the field campaign, including airborne precipitation measuring radar, ground-based weather radar, ground-based multi-channel microwave radiometer, GPS radiosonde, 10 GHz and 37 GHz radiometer, portable wind measuring device, and temperature measuring device. Initial analysis is accomplished with observation data obtained from BH-RM 2010. Observation results of Ka-band precipitation measuring radar working in pulse compression mode and short pulse mode are presented, which show clearly the vertical and horizontal structure of rainfall. Due to the radar different scan modes, resolutions, frequencies, and dynamic range, it's difficult to compare airborne radar data and ground-based radar data accurately, and the unstable attitude of the airplane makes the comparison more difficult. Spatial matching of Ka-band airborne radar data and Tianjin S-band ground-based Doppler radar data is carried out and detailed procedures are introduced. Quantitative indexes are further computed to indicate the observation consistency statistically. In rain retrieval algorithms, attenuation correction is a critical step. Using GPS radiosonde data, ground-based multi-channel microwave radiometer data and microwave radiative transfer model, the integrated attenuation of Ka-band radar is computed and attenuation correction is accomplished. The result is reasonable, which lays a basis for future rain retrieval. Data obtained by various instruments in the field campaign will be analyzed thoroughly, propelling development and rain rate retrieval of our spaceborne precipitation measuring radar.