Observational operators for dual polarimetric radars in variational data assimilation systems (PolRad VAR v1.0)
Observational operators for dual polarimetric radars in variational data assimilation systems (PolRad VAR v1.0)
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DOI：
10.5194/gmd-11-2493-2018
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发表时间：
2018-06
影响因子：
5.1
通讯作者：
T. Kawabata;T. Schwitalla;A. Adachi;H. Bauer;V. Wulfmeyer;N. Nagumo;H. Yamauchi
中科院分区：
文献类型：
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作者：
T. Kawabata;T. Schwitalla;A. Adachi;H. Bauer;V. Wulfmeyer;N. Nagumo;H. Yamauchi
抽象的。我们在两个变分资料同化系统中实现了两个用于双极化雷达的观测算子：天气研究和预报模式变分资料同化系统WRF Var和日本气象厅非静力资料同化系统NHM-4DVAR。该算子由一个空间插值器、两种变量转换器以及它们的线性化和转置(伴随)算子组成。空间内插器考虑了雷达波束在垂直和水平方向上的展宽以及气候波束弯曲的影响。第一个变量转换器用模型预测变量模拟极化参数，并包括衰减效应，第二个变量转换器从观测到的极化参数(特定差分相位)得出雨水含量。我们为空间插值器和变量转换器开发了线性化算子和伴随算子，然后评估了线性化算子的线性度和伴随算子的精度是否足以在变分系统中实现。一个简单的同化实验结果表明，同化结果与观测值在反射率和特定差分相位方面符合得很好，但在差分反射率方面则不符合。
Abstract. We implemented two observational operators for dual polarimetric radars in two variational data assimilation systems: WRF Var, the Weather Research and Forecasting Model variational data assimilation system, and NHM-4DVAR, the nonhydrostatic variational data assimilation system for the Japan Meteorological Agency nonhydrostatic model. The operators consist of a space interpolator, two types of variable converters, and their linearized and transposed (adjoint) operators. The space interpolator takes account of the effects of radar-beam broadening in both the vertical and horizontal directions and climatological beam bending. The first variable converter emulates polarimetric parameters with model prognostic variables and includes attenuation effects, and the second one derives rainwater content from the observed polarimetric parameter (specific differential phase). We developed linearized and adjoint operators for the space interpolator and variable converters and then assessed whether the linearity of the linearized operators and the accuracy of the adjoint operators were good enough for implementation in variational systems. The results of a simple assimilation experiment showed good agreement between assimilation results and observations with respect to reflectivity and specific differential phase but not with respect to differential reflectivity.