The Study On Sounding Humidity Measurement And Solar Radiation Error Correction System

At present,most of the measurement of meteorological elements is digital radiosonde,but its accuracy in humidity measurement has not been high.The reason is not only the humidity sensor's own error,but also the humidity measurement is easy to be interfered by other factors in the environment.The humidity measurement error caused by the less studied solar radiation is a factor that cannot be ignored.This topic will focus on the influence of solar radiation on the sounding humidity measurement.Firstly,the mechanism of the error of solar radiation on humidity measurement is studied.Secondly,the simulation of CFD software is used,and the error of humidity measurement caused by solar radiation is studied by using the experimental verification method.Finally,the radiosonde GTS1 is used as a model and the neural network algorithm is used.A large number of data samples of the simulation are processed to predict the solar radiation error of the humidity measurement,and the solar radiation error of the humidity measurement of the Nanjing sounding station is corrected.The specific research content is as follows.(1)Research was carried out around the GTS1 type radiosonde.The solar radiation heating amount is calculated by using the CFD(Computational Fluid Dynamics)software for the humidity resistance of the radiosonde(assuming no shield).The humidity measurement error is obtained by the temperature error.Under the different conditions of the humidity measurement system,it is found that the altitude,solar radiation intensity and solar elevation angle will affect the temperature rise,and they are all positively correlated.The maximum temperature rise is 4.87?.The relative error reached 32.99%.Then the GTS1 humidity measurement system(with shield)was used as a model to simulate that the shield can only reduce the temperature rise of the solar radiation on the sensor surface,but there is still temperature rise,especially in high altitude areas,the temperature is still considerable.The highest temperature reached 4.03?,the relative error of humidity measurement still reached 26.71%.(2)A sounding humidity measurement and correction system is designed independently.The hardware part is equipped with two temperature sensors to measure the temperature of the air and humidity sensor surface to obtain the actual solar radiation heating amount,and a humidity sensor to measure the relative humidity of the air.The software part uses the GoffGratch saturated water vapor pressure approximation formula to realize the correction algorithm of humidity error.The system can also perform remote control and data transmission with the LORA wireless communication and the host computer through network communication.(3)The experimental verification of the simulation results was carried out by means of the sounding humidity measurement correction system.By simulating the temperature rise of different solar radiations and different altitudes,the actual temperature rise of the surface of the humidity sensor measured under the same high altitude conditions is compared and analyzed.The experimental results agree well with the simulation results.The average surface temperature increase error is 0.095?.At the same time,the experimental results show that the solar radiation causes the dryness error of the humidity measurement,and the larger the temperature rise,the larger the solar radiation dry error of the humidity measurement,which is consistent with the theoretical analysis.(4)Through the PSO-BP neural network,the 2530 data samples of the computational fluid dynamics simulation are trained and segmented,and then the temperature rise of the surface of the humidity sensor can be predicted by using the air pressure,solar radiation intensity and solar elevation angle.The results are compared with the CFD simulation results.The absolute value of the prediction error is 0.76? and the root mean square error is 0.075?.Then the prediction algorithm is implanted into the sounding humidity measurement correction system to directly predict the surface temperature of the sensor and correct the relative humidity of the dry.From the correction results,the relative error of the humidity relative to the solar radiation can reach more than 40%.The sounding humidity correction algorithm provided in this study can improve the correction efficiency of solar radiation error in sounding humidity measurement.