ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Archive > Volume 49 Issue 5 > 2023,49(5):542-550. DOI:10.7519/j.issn.1000-0526.2022.121801 Prev Next
Retrieval Method of Precipitation Water Vapor and Cloud Liquid Water Path Based on 183 GHz Airborne Microwave Radiometer
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Abstract:
Based on the airborne microwave radiometer （G-band water vapor radiometer, named GVR）, a retrieval algorithm of precipitation water vapor and liquid water 〖JP2〗path based on BP neural network and Decker〖JP〗 model is established by using the Beijing sounding data as the training data, and the airborne microwave radiation transfer equation as the forward algorithm. Compared to the GVR own algorithm, the observation height is added as an input variable. A new cloud model considering the influence of temperature on the cloud water phase, and the historical sounding data completed to increase the integral height to 30 km are applied in the new algorithm. The precipitation water vapor errors calculated by two algorithms are verified by using numerical simulation test, external field observation test and observation error transfer analysis. The results show that the correlation coefficient between the retrieval and probe values of the new and GVR own algorithms are 0.9988 and 0.9929 respectively. The retrieval value of the GVR own algorithm is generally lower than the sounding calculation value. The absolute errors of precipitation water vapor calculated by the new and GVR own algorithms are 0.05-1.30 mm and 0.2-3.0 mm, relative errors are 1%-10% and 4%-65%, the minimum relative error calculated by the new algorithm is 1% below 6 km, about 75% of new algorithm results are below 5% while only less than 1% of GVR own results are below 5%. Take the data observed on 20 November 2016 as an example. The errors caused by the GVR instrument observation errors that are calculated by the new algorithm and the GVR own algorithm retrieval formula are 0.05 mm and 0.06 mm at 3000 m height respectively. After of retrieval formula, with the increase of the water vapor detection value (the aircraft altitude drops), the transfer error increase of the GVR own algorithm is significantly higher than that of the new algorithm. The flight case on 30 June 2021 is selected to verify the liquid water path retrieval error of the two algorithms. The results show that the liquid water path ranges of the new algorithm and the own algorithm are 0 mm and 0-0.006 mm during cloudless periods over the plane. Error analysis shows that the new algorithm is effective for improving the retrieval accuracy of local precipitation water vapor and liquid water path.
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