Dual-Polarization Radar Retrievals of Coastal Pacific Northwest Raindrop Size Distribution Parameters Using Random Forest Regression
Dual-Polarization Radar Retrievals of Coastal Pacific Northwest Raindrop Size Distribution Parameters Using Random Forest Regression
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DOI：
10.1175/jtech-d-19-0107.1
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发表时间：
2020-02
影响因子：
2.2
通讯作者：
Robert Conrick;Joseph P. Zagrodnik;C. Mass
中科院分区：
文献类型：
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作者：
Robert Conrick;Joseph P. Zagrodnik;C. Mass
对华盛顿州奥林匹斯半岛山区的水滴粒径分布（DSD）参数进行了雷达反演和评价。用于开发检索的观测数据是在2015/16年奥林匹克山实验（OLYMPEX）期间收集的，其中包括NASA s波段双偏振（NPOL）雷达和第二代粒径和速度（PARSIVEL2）测量仪在屏障的迎坡上收集。非线性和随机森林回归应用于PARSIVEL2数据，以开发中位数体积直径，液态水含量和降雨率的检索。与非线性回归相比，使用随机森林模型可以提高DSD检索精度（由检索相对于PARSIVEL2观测值的平均误差定义）。对分差仪观测资料和NPOL反演资料的评估表明，雷达反演资料可以准确地再现该地区观测到的DSDs，包括该地区常见的小而多雨滴的冬季状态，这对该地区很重要。利用二维视频disdrom （2DVD）和垂直指向的微雨雷达进一步评估了OLYMPEX期间的NPOL检索。结果表明，利用随机森林的雷达反演可以较好地捕获大气最低部分的DSD特征。
Radar retrievals of drop size distribution (DSD) parameters are developed and evaluated over the mountainous Olympic Peninsula of Washington State. The observations used to develop retrievals were collected during the 2015/16 Olympic Mountain Experiment (OLYMPEX) and included the NASA S-band dual-polarimetric (NPOL) radar and a collection of second-generation Particle Size and Velocity (PARSIVEL2) disdrometers over the windward slopes of the barrier. Nonlinear and random forest regressions are applied to the PARSIVEL2 data to develop retrievals for median volume diameter, liquid water content, and rain rate. Improvement in DSD retrieval accuracy, defined by the mean error of the retrieval relative to PARSIVEL2 observations, was achieved when using the random forest model when compared with nonlinear regression. Evaluation of disdrometer observations and the retrievals from NPOL indicate that the radar retrievals can accurately reproduce observed DSDs in this region, including the common wintertime regime of small but numerous raindrops that is important there. NPOL retrievals during the OLYMPEX period are further evaluated using two-dimensional video disdrometers (2DVD) and vertically pointing Micro Rain Radars. Results indicate that radar retrievals using random forests may be skillful in capturing DSD characteristics in the lowest portions of the atmosphere.