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

2. Distribution on Sites 2

3. 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

4. GTS1-2 & GTS1-2 advanced version4

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

6. 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

7. 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

8. 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

9. 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

10. Pressure
hPa
GTS1-2
GTS1
hPa 10

11. Pressure
GTS1-2 advanced version
GTS1-2 11

12. Temperature
GTS1-2
GTS1 12

13. Temperature
GTS1-2 advanced version 13

14. Humidity
GTS1-2
GTS1 14

15. 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

16. Wind Direction
Wind Speed 16

17. 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

18. 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

19. Thanks！ 19