Mixing layer height retrievals by multichannel microwave radiometer observations
Mixing layer height retrievals by multichannel microwave radiometer observations
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DOI：
10.5194/amt-6-2941-2013
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发表时间：
2013-11
影响因子：
3.8
通讯作者：
D. Cimini;F. Angelis;J. Dupont;S. Pal;M. Haeffelin
中科院分区：
文献类型：
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作者：
D. Cimini;F. Angelis;J. Dupont;S. Pal;M. Haeffelin
抽象的。混合层高度（MLH）是边界层研究的关键参数，包括气象学，空气质量和气候。MLH估计是从现场无线电探空仪测量或激光雷达、风廓线雷达或声雷达等仪器的遥感观测推断的。从无线电探空仪廓线估计最大陆压的方法也用于微波辐射计（MWR）反演的大气温度和湿度廓线。本文提出了一种替代方法来估计MLH MWR数据的基础上，直接观测（亮度温度，Tb），而不是检索配置文件。据我们所知，MLH估计直接从Tb观测从未尝试过。该方法由一个多元线性回归训练的先验集合的同位MWR Tb观测（多频率和多角度）和MLH估计从一个国家的最先进的激光雷达系统。所提出的方法被应用到一个7个月的数据集收集在一个典型的中纬度地区。结果表明，该方法是能够遵循的昼夜周期和一天到一天的变化所建议的激光雷达测量，它也可以检测低MLH值低于全重叠限制（~200米）的激光雷达系统。MWR和参考激光雷达的MLH检索之间的比较的统计显示，平均差异在10米内，均方根在340米，相关系数大于0.77。MWR、激光雷达和无线电探空仪对白天MLH的月平均分析显示出一致的季节变化，6月在~1200-1400 m处达到峰值，10月下降到~600 m。相反，所有方法的夜间月平均MLH在300-500米范围内，没有任何显着的季节性变化。所提出的方法提供的结果是更一致的无线电探空仪估计比MLH估计从MWR检索配置文件。MLH月平均值在1个标准差内与在11：00和23：00 UTC无线电探空仪剖面上应用的批量理查森数方法一致。本文所述的方法连续运作，预计在整个昼夜周期的类似性能，除了在相当大的降水，展示了新的潜力，大气观测地面微波辐射测量。
Abstract. The mixing layer height (MLH) is a key parameter for boundary layer studies, including meteorology, air quality, and climate. MLH estimates are inferred from in situ radiosonde measurements or remote sensing observations from instruments like lidar, wind profiling radar, or sodar. Methods used to estimate MLH from radiosonde profiles are also used with atmospheric temperature and humidity profiles retrieved by microwave radiometers (MWR). This paper proposes an alternative approach to estimate MLH from MWR data, based on direct observations (brightness temperatures, Tb) instead of retrieved profiles. To our knowledge, MLH estimates directly from Tb observations have never been attempted before. The method consists of a multivariate linear regression trained with an a priori set of collocated MWR Tb observations (multifrequency and multi-angle) and MLH estimates from a state-of-the-art lidar system. The proposed method was applied to a 7-month data set collected at a typical midlatitude site. Results show that the method is able to follow both the diurnal cycle and the day-to-day variability as suggested by the lidar measurements, and also it can detect low MLH values that are below the full overlap limit (~200 m) of the lidar system used. Statistics of the comparison between MWR- and reference lidar-based MLH retrievals show mean difference within 10 m, root mean square within 340 m, and correlation coefficient higher than 0.77. Monthly mean analysis for daytime MLH from MWR, lidar, and radiosonde shows consistent seasonal variability, peaking at ~1200–1400 m in June and decreasing down to ~600 m in October. Conversely, nighttime monthly mean MLH from all methods are within 300–500 m without any significant seasonal variability. The proposed method provides results that are more consistent with radiosonde estimates than MLH estimates from MWR-retrieved profiles. MLH monthly mean values agree well within 1 standard deviation with the bulk Richardson number method applied at radiosonde profiles at 11:00 and 23:00 UTC. The method described herewith operates continuously and is expected to work with analogous performances for the entire diurnal cycle, except during considerable precipitation, demonstrating new potential for atmospheric observation by ground-based microwave radiometry.