Evaluation for China L band radiosonde Dr. LI Wei CMA Meteorological Observation Centre

Distribution on Sites 2

Silicon piezoresistance Aneroid capsule capacitor Type Sensors GTS1 GTS1-2 advanced version Temperature Rod thermistor diameter 1 mm Diameter 1.2 mm Bead thermistor diameter 0.5 mm Pressure Silicon piezoresistance Aneroid capsule capacitor Aneroid capsule capacitor Humidity Carbon hygristor Thin-film capacitor 3

GTS1-2 & GTS1-2 advanced version 4

RS92 as reference radiosonde. Multiple radiosondes attached on one balloon. 5

Principle: Error separating method (1) If there are enough sample data, the data distribution will be normalization. (2) Two radiosondes with the same sensors between which the statistical systematic errors (SE) should be near zero. And the STD of each them should be approximately equal. 6

Analytical Methods of Dynamic Measurement Error 1)Taking RS92 as a standard and GTS1, GTS1-2 as tests, the STD of the tests is given by formula (1): (1) 2) As the principle, the separated STD of RS92 is given by formula (2): (2) So the individual STD of RS92, GTS1 and GTS1-2 can be achieved. 7

Comparative Trial Data description Comparative trials sites : Yangjiang, Xinlinhaote and Nanjing upper-air stations The number of releasing sounding balloons: 65 Available data sets: 59 Methods of trails: Nanjing Yangjiang GTS1-2 RS92 RS92 GTS1-2 GTS1 RS92 GTS1-2 advanced GTS1 RS92 Yangjiang, Xinlinhaote 8

Results of comparative Trial comparative results (RS92 is standard) P (hPa) T (℃) U (%RH) STD SE GTS1 ≥500hPa 0.76 -1.22 ≥100hPa 0.23 0.12 ≥-25℃ 5.53 -7.78 GTS1-2 0.59 -0.28 0.32 0.05 5.97 2.22 GTS1-2 advanced 0.13 -0.12 < 500hPa 0.65 -0.98 <100hPa 0.67 0.14 <-25℃ 8.47 2.78 0.48 -0.45 0.40 0.09 10.53 -4.55 0.31 -0.31 9

Pressure hPa GTS1-2 GTS1 hPa 10

Pressure GTS1-2 advanced version GTS1-2 11

Temperature GTS1-2 GTS1 12

Temperature GTS1-2 advanced version 13

Humidity GTS1-2 GTS1 14

GTS1 & GTS1-2 (using the same type of L-band radar) Wind Direction Wind Speed GTS1 & GTS1-2 (using the same type of L-band radar) 15

Wind Direction Wind Speed 16

5. Conclusion The temperature sensor of radiosonde used in China has been changed from the rod-shaped thermistor to bead thermistor gradually, the measurement accuracy has been improved significantly, and the radiation error has also been effectively corrected. At present, the GTS1-2 radiosonde has better performance than GTS1, but the humidity measurement still exist a certain gap compared with RS92. 17

Through software algorithm, bias for pressure measurement can be corrected largely. Current operational wind calculation method has relative large wind pulse affection, and some real results reflecting the wind speed and direction have also been smoothed. The moving average vector method can better eliminate the pulsation effect. If using the 1 minute moving average window to calculate the upper-air wind per second, it can be consistent with GPS wind measurement. 18

Thanks！ 19