Passive microwave signatures of the melting layer in stratiform clouds

遥感信息 Pub Date : 1997-08-03 DOI:10.1109/IGARSS.1997.606421

Peter Bauer, J.P.V. Poiares Baptista, M. D. Iulis

引用次数: 0

Abstract

A study was carried out in order to estimate the effect of melting particles on brightness temperatures at microwave frequencies between 10.7 and 85.5 GHz. A meteorological model framework was set up to determine the melting stage of various frozen particles below the freezing layer. Different approaches for calculating the effective permittivity of mixed particles were compared. The resulting extinction coefficients, single scattering albedos, and asymmetry parameters indicate a maximum effect when a water matrix with air/ice inclusions is assumed. Extreme local differences of 20-25% between the optical parameters employing either a Marshall-Palmer or a Gamma-type dropsize distribution occur. When radiative transfer calculations are carried out, maximum deviations of >20 K at low frequencies are observed. Neglecting the melting effect may lead to severe overestimations of surface rainrates by up to 100% in stratiform conditions.

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层状云中熔融层的被动微波特征

在10.7 ~ 85.5 GHz微波频率范围内，研究了熔融粒子对亮温的影响。建立了一个气象模式框架，以确定冻结层以下各种冻结颗粒的融化阶段。比较了计算混合粒子有效介电常数的不同方法。所得消光系数、单次散射反照率和不对称参数表明，当假设含有空气/冰包裹体的水基质时，效果最大。采用马歇尔-帕尔默或伽玛型液滴大小分布的光学参数之间存在20-25%的极端局部差异。当进行辐射传输计算时，在低频处观测到的最大偏差> 20k。忽略融化效应可能导致在层状条件下对地表降雨率的严重高估，最高可达100%。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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遥感信息

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