Identifying multiple-scattering-affected profiles in CloudSat observations over the oceans
Identifying multiple-scattering-affected profiles in CloudSat observations over the oceans
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识别海洋上空 CloudSat 观测中受多重散射影响的剖面
DOI：
10.1029/2008jd009960
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发表时间：
2008
影响因子：
--
通讯作者：
C. Simmer
中科院分区：
文献类型：
--
作者：
Battaglia;J. Haynes;T. L'Ecuyer;C. Simmer
当卫星经过中强降水系统时，多次散射强烈影响CloudSat廓线雷达的反射率。因此，在解释任何涉及在下雨场景中使用CloudSat数据的应用程序的结果之前，必须确定可能受到多次散射污染的配置文件。在分析多次散射蒙特卡罗反射率模拟应用于云解析模型生成的微物理廓线的基础上，提出了一个相对简单的标准，用于标记可能受多次散射影响的廓线。路径积分衰减可以从CloudSat的2B-GEOPROF产品中估算出来，可用于识别四种多次散射机制：（1）单次散射近似适用于整个Z剖面;（2）单次散射近似不可靠，但二阶散射近似有效;（3）由于更高阶的多次散射效应，二阶散射近似是无效的，然而，这并不影响基于表面参考技术的路径积分衰减估计;以及（4）多次散射也影响表面回波，从而破坏路径积分衰减估计。然后将这些机制的操作路径集成衰减阈值应用于全球海洋上的CloudSat数据集，其中路径集成衰减估计比陆地上更准确。案例研究和全球统计的多次散射的发生：海洋像素，约80%（90%）的配置文件确定为下雨可以在单次散射（二阶散射）近似处理。对于表面参考技术对CloudSat剖面雷达系统的适用性，建议单向路径集成衰减的阈值约为20 dB。这大致对应于96.5%的雨天像素。由于不同的降水制度，结果是强烈的区域和季节依赖性。例如，在热带辐合带中，一部分不可忽略的降雨像素需要二阶散射（10-15%）或高阶散射（约10%）来精确模拟观测到的反射率廓线。
Multiple scattering strongly affects the CloudSat Profiling Radar reflectivity when the satellite is overpassing moderate and heavy precipitation systems. Therefore it is important to identify profiles that may be contaminated by multiple scattering prior to interpreting the results of any application that involves the use of CloudSat data in raining scenes. On the basis of analysis of multiple‐scattering Monte Carlo reflectivity simulations applied to cloud‐resolving model‐generated microphysical profiles encompassing a large variety of precipitating systems, a relatively straightforward criterion is proposed for flagging profiles potentially affected by multiple scattering. The path‐integrated attenuation, that can be estimated from CloudSat's 2B‐GEOPROF product, can be used to identify four multiple‐scattering regimes: (1) the single scattering approximation is applicable to the entireZ‐profile; (2) the single scattering approximation is unreliable but the second order of scattering approximation is valid; (3) the second order of scattering approximation is not valid owing to higher order of multiple‐scattering effects which, however, do not affect the surface reference technique‐based path‐integrated attenuation estimates; and (4) the multiple scattering is affecting the surface return as well, thus spoiling the path‐integrated attenuation estimates. Operational path‐integrated attenuation thresholds for each of these regimes are then applied to the CloudSat data set over the global oceans, where path‐integrated attenuation estimations are more accurate than over land. Case studies and global statistics of the occurrence of multiple scattering are presented: for ocean pixels, around 80% (90%) of the profiles identified as rainy can be treated in the single scattering (second order of scattering) approximation. A threshold value around 20 dB for the one‐way path‐integrated attenuation is suggested for the applicability of the surface reference technique to the CloudSat Profiling Radar system. This roughly corresponds to 96.5% of the rainy pixels. Owing to the different precipitation regimes, results are strongly regionally and seasonally dependent. For instance in the Inter‐Tropical Convergence Zone a not negligible fraction of the raining pixels requires either second‐order (10–15%) or higher‐order scattering (∼10%) to accurately model the observed reflectivity profile.
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影响因子：
3.1
作者：
R. Hogan;A. Battaglia
通讯作者：
R. Hogan;A. Battaglia
影响因子：
8.2
作者：
A. Battaglia;C. Simmer
通讯作者：
A. Battaglia;C. Simmer
DOI：
--
发表时间：
2007
期刊：
影响因子：
--
作者：
O. Pujol;J. Georgis;L. Feral;H. Sauvageot
通讯作者：
H. Sauvageot
影响因子：
4.9
作者：
H. Masunaga;T. L’Ecuyer;C. Kummerow
通讯作者：
H. Masunaga;T. L’Ecuyer;C. Kummerow
Cloudsat 配置中雷达多重散射效应的评估
DOI：
--
发表时间：
2006
期刊：
影响因子：
--
作者：
A. Battaglia;M. Ajewole;C. Simmer
通讯作者：
C. Simmer