The International Radiosonde Intercomparison Result for China-made GPS Radiosonde

Based on total 29 groups observation data of the 8th WMO International Radionsonde System Intercomparison, using the same balloon releasing method and mainly choosing Vaisala radiosonde measurements as relative reference standard, the systematic evaluation for Changfeng China-made GPS radiosonde system and Huayun China-made GPS radiosonde system is carried out including typical examples analysis and statistics analysis. The initial evaluation results show that for temperature observation, the value of both domestic radiosonde is higher compared to Vaisala radiosonde. The relative systematic error of Changfeng radiosonde is within 0.4℃ and standard deviation is within 0.7℃, the Huayun radiosonde owns similar performance, but its error obviously increases. For humidity observation, the observation data of Changfeng radiosonde below 16 km basically show dry trend compared to Vaisala radiosonde, and below 12 km humid trend for Huayun radiosonde. Below 14 km the relative systematic errors for Changfeng radiosonde and Huayun radiosonde can be within 4% and 6%, respectively, and above 14 km the relative systematic errors obviously increase, reaching 12% and 20%, respectively, and the standard deviations for gradually show increasing trend from surface to tropopause and can reach 14% and 17%, respectively. For pressure observation the relative systematic errors and standard deviations for Changfeng radiosonde and Huayun radiosonde is smaller compared to Vaisala radiosonde, the relative systematic errors show the similar trend that negative values occur in low layer and positive values in upper layer, and the standard deviations show decreasing trend from surface to upper layer. The absolute value of minimal relative systematic error minus maximal relative systematic error is within 1 hPa and maximal standard deviation is 1.2 hPa for surface point, assuring the accurate geopotential height calculation and correct pressure retrieving algorithm. For wind observation the relative systematic errors and standard deviations for Changfeng radiosonde and Huayun radiosonde is smaller compared to Vaisala radiosonde, and the analysis results show excellent GPS positioning function and correct wind calculation algorithm. It can be concluded the domestic radiosonde has reached advanced level except for the humidity element. In future, more improvements should be made on temperature observation above 30 km and humidity observation under low temperature.