ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Archive > Volume 42 Issue 7 > 2016,42(7):777-789. DOI:10.7519/j.issn.1000-0526.2016.07.001 Prev Next
Study of Moment Methods in Estimating Three Parameters of Gamma Raindrop Size Distribution
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Abstract:
Using the rain drop size distribution (DSD) data obtained from OTTParsivelⅡlaser optical disdrometer in 4-23 August 2014 in Xinzhou, Shanxi Province, the moments method for estimating Gamma DSD parameters is studied in this paper. The precipitation clouds are divided into three categories: stratiform, cumuliform and stratiform mixed with cumuliform. Comparing the observed and estimated DSD data in 1 min, 5 min average and moving 5 min average, root mean square error (RMSE) and error distribution of DSD are computed with the method of least square and moments. A new method of moments is put forward involving M0, M3 and M6 which respectively represent the moments of raindrop number concentration, liquid water content and radar reflectivity. The analysis shows that using moments to estimate rain DSD, the M036 (M0, M3 and M6) is the best among the moment methods because the averaged RMSE in 1 min, 5 min average and moving 5 min average is minimum and the error distribution is concentrated. The parameters of DSD estimated from threekind precipitation clouds decrease with the increase of rainfall intensity R. The fitting DSD parameters (N0, μ, λ) satisfy binomial distribution and their correlation coefficient is good.
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