O2(7) China Beidou radiosonde system .ppt - · BeiDou radiosonde system is a GNSS(Beidou and GPS) type radiosonde system, and is composed of radiosonde, surface signal receiver ,ground

中国气象局气象探测中心

CMA Meteorological Observation Centre

China BeiDou radiosonde system

Yang RongKangMeteorological Observation Cntre of CMA

[email protected]



BeiDou radiosonde system is a GNSS(Beidou and GPS) type radiosonde system, and is composed of radiosonde, surface signal receiver ,ground check instrument and etc..

23 Chinese Beidousatllite are working now,and positioning service cover the asia-pacific region



Radiosonde schematics

Pressure sensor has been put in measurement signal collection and conversion module



Sensor Type Country

Temperaturebead aluminized thermistor

China

HumidityPolymer film capacitive

Austria

Pressure Silicon resistance America

Satellite navigation module BeiDou and GPS China

After 8th WMO Intercomparison, New type Chinese GNSS radiosonde system has been developed



New temperature sensor installation structure to minimize the fluctuation of measurement

Sensor upgrade



humidity sensor change to E+E type

Sensor upgrade



Bedou and GPS navigation satellite provide jointly positioning calculation

Sensor upgrade



The change to CF13A

A sensor added to measure the pressure



Comparison test with RS92

• In this test, 20 flights have been done for radiosonde performance, in which 40 tested radiosondes were launched.

• Also 20 flights have been done for different positioning model evaluation, in which 60 tested radiosondes were launched.

• In total, 40 tested radiosondes were launched in raining day while 25 flights were launched with 10/10 cloud amount.



12th~18th,Dec,2013YangJiang station



Test method

Performance test(Comparability to RS92, and Reproducibility )

1 RS92 radiosonde and 2 tested radiosondes are launched using 1 balloon,

and wind finding will be calculated based on mixing model of BeiDou and

GPS.

Test for BeiDou and GPS positioning respectively

1 RS92 radiosonde and 3 tested radiosondes are launched using 1 balloon,

and wind finding will be calculated based on single BeiDou, single GPS,

and mixing model of BeiDou and GPS.



Quality control

• The single abnormal point has been deleted.

• Obvious abnormal data segment, which can be found by sensor breakdown or satellite signal lost, will be deleted, and related detailed information has been recorded.

• Water contamination data for temperature sensor has been deleted, and relevant information has been recorded.



Error synthesis principal

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212 22 ＝＝

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standard deviation of two comarison radiosonde is composed of their own standard deviation. If 2 tested objects have the same error, then:

• By the principal above, standard deviation can be separated to each type radiosonde.



1 Temperature



• The difference between 2 tested radiosonde with the same balloon is no more than 0.05K.

• After random error separation processing, in the whole the standard deviation is within 0.1K, in particular above 200hPa the standard deviation of tested radiosonde is even smaller than RS92.

Reproducibility analysis

Sd.of RS92 came from the other comparison test,which included 30 flights with 2 RS92 radiosondes.



• The bias between tested radiosonde and RS92 is -0.05～0.1K, and good consistent performance can be seen.

• Blow 500hPa, the standard deviation of tested radiosonde is similar to RS92, and at 500hPa～50hPa, becomes relatively bigger, in particular increases to 0.5hPa near 100hPa( tropopause).

Comparability to RS92



• In the meanwhile, based on daytime and night time temperature statistics result above 200hPa, the daytime bias is stably 0.3℃ higher while night time bias is stably 0.1℃ lower, and standard deviation of daytime and night time show similar characteristic to RS92. So temperature radiation error has been well controlled.



From some typical examples, about 10 samples, significant water contamination still can be found when tested radiosondes go through raining cloud, and temperature can drop at most 2K due to evaporation effect.



2 Humidity



• The difference between 2 tested radiosondes with the same balloon is within ±0.2%RH, no obvious bias occurs.

• After random error separation processing, the own standard deviation of tested radiosonde is with 1%RH, which is similar to RS92. Combined with bias analysis, we can say that the tested radiosonde has good reproducibility.




• The bias increases above 400hPa, it may means that performance declines when ambient temperature is blow -30℃, in particular above 200hPa, the humidity of tested radiosonde has obvious dry bias, it may means that performance significantly declines when ambient temperature is blow -50℃.




• A typical example, the humidity of tested radiosonde has wet bias at high humidity segment with increasing height, and humidity sensor can not response in time at and beyond tropopause



3 Pressure



• The bias between 2 tested radiosondes with the same balloon is within 0.1hPa, no obvious bias occurs.

• Both pressure sensor and retrieving pressure of tested radiosonde have shown very good reproducibility.





• The bias between tested radiosonde and RS92 is systematically within 0.2hPa after the transition point from pressure sensor measurement to retrieving pressure, but basically no systematic error can be seen above 50hPa. Also the similar analysis result can be got for standard deviation, and maximal value is no more than 0.2hPa.

• The difference between tested radiosonde and RS92 may be caused by algorithm, so we can not effectively evaluate the result. In the whole, the tested radiosonde has good capability of pressure measurement.



4 Geopotential height



• Compare to RS92,The bias and standard deviation between 2 tested radiosondes with the same balloon are within 1gpm, and no obvious difference can be seen.




• Compared to RS92, both bias and standard deviation is slowly increasing with height from surface to 50hPa, and the difference significantly becomes bigger above 50hPa.




5 Wind



• The bias of wind direction and wind speed between 2 tested radiosondes with the same balloon are 0.2゜ and 0.05m/s, respectively.

• After random error separation processing, the standard deviation of tested radiosonde is better than RS92, maybe it is because new positioning modules have been applied to the tested radiosonde.




• The bias of wind direction and wind speed between tested radiosonde and RS92 are 1゜ and 0.1m/s, respectively.

• The standard deviation of wind direction tested radiosonde is very small blow 100hPa, then becomes bigger, and the standard deviation of wind direction tested radiosonde is almost same as RS92.



• Compared to RS92, except humidity, all other elements of tested radiosonde have close or better reproducibility.The humidity uncertainty of radiosonde is relatively large, and big gap still exists compared to RS92.

• Compared to RS92, the comparability of pressure and geopotential height of tested radiosonde show a obvious systematic difference, but its reproducibility is better than RS92, so maybe the difference of related algorithms between tested radiosonde and RS92 has played major role for the systematic difference, which should be evaluated further.

Total uncertainty and reproducibility



6 Different positioning models analysis



• The systematic errors of 3 different positioning models have almost same changing trend compared to RS92, which shows that there are the same systematic difference with RS92.

• Except that a significant big standard deviation value 70gpm has occurred for single BeiDou model at 70～50hPa, 3 satellite positioning models have shown a good consistency, and owned almost the same error changing trend.

the reasons of abnormal phenomena of BeiDoupositioning model at 70～50hPa are because: 1)currently less BeiDou navigation satellites have been deployed, so available satellites is only 5 or 6 in experiment, not very stable;2)low altitude of test site has got bad satellite distribution, which may restrict BeiDou navigation capability.



• Compared to RS92, the bias of wind direction and wind speed of 3 satellite positioning models are within 0.7° and 0.1m/s, respectively, there is no whole systematic difference.

• There are the same error characteristic for the 3 satellite positioning models, and excellent technical performance can be seen for all 3 different satellite pisionning models expect relative big error at 150~70hPa for single BeiDou model.

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• mixing model(GPS and BeiDou) is slightly better than single GPS model while single GPS model is slightly better than single BeiDou model.

• The wind finding performance of 3 different satellite positioning models is close. Compared to the other 2 satellite positioning models, the performance of geopotential height of BeiDou model is worse than that of wind of BeiDou model.

• Totally, any satellite positioning model can meet operational requirement.



Conclusion

• Regarding comparability of temperature, pressure and satellite positioning module, the new BeiDouradiosonde has similar performance to RS92. Moreover, BeiDou radiosonde radiosonde has better reproducibility compared to RS92.

• The new temperature sensor of BeiDou radiosonde still meets obvious water contamination issue, which needs further water prevention technology improvement as well as algorithm correction study. Meanwhile further improvement should be done for solar radiation correction.

• Further study should be done for significant systematic difference of pressure and geopotentialheight between BeiDou radiosonde and RS92.



Conclusion

• Low temperature still obviously affects the performance of humidity sensor of BeiDou radiosonde, so big gap exists between BeiDou radiosonde and RS92. But due to its good reproducibility, some algorithm can be applied to improve response capability of humidity sensor for better data.

• Through intercomparison of 3 different satellite positioning models(mixing GPS and BeiDou, single GPS, single BeiDou) for geopotential height, wind direction and wind speed, compared to RS92, we can get that there is almost the same performance for mixing model(GPS and BeiDou) and single GPS model, and single BeiDou model also can show close performance.

The correction model of humidity has been tested, but for the large time constant in the low temperature, the corrections are very sensitive to the noise,andneed to be validated.



Thanks for your attention

Documents

O2(7) China Beidou radiosonde system .ppt - · BeiDou radiosonde system is a GNSS(Beidou and GPS) type radiosonde system, and is composed of radiosonde, surface signal receiver ,ground