Passive microwave remote sensing of the historic February 2010 snowstorms in the Middle Atlantic region of the USA

The snowfall in the Baltimore/Washington metropolitan area during the winter of 2009/2010 was unprecedented and caused serious snow‐related disruptions. In February 2010, snowfall totals approached 2 m, and because maximum temperatures were consistently below normal, snow remained on the ground the entire month. One of the biggest contributing factors to the unusually severe winter weather in 2009/2010, throughout much of the middle latitudes, was the Arctic Oscillation. Unusually high pressure at high latitudes and low pressure at middle latitudes forced a persistent exchange of mass from north to south. In this investigation, a concerted effort was made to link remotely sensed falling snow observations to remotely sensed snow cover and snowpack observations in the Baltimore/Washington area. Specifically, the Advanced Microwave Scanning Radiometer onboard the Aqua satellite was used to assess snow water equivalent, and the Advanced Microwave Sounding Unit‐B and Microwave Humidity Sounder were employed to detect falling snow. Advanced Microwave Scanning Radiometer passive microwave signatures in this study are related to both snow on the ground and surface ice layers. In regard to falling snow, signatures indicative of snowfall can be observed in high frequency brightness temperatures of Advanced Microwave Sounding Unit‐B and Microwave Humidity Sounder. Indeed, retrievals show an increase in snow water equivalent after the detection of falling snow. Yet, this work also shows that falling snow intensity and/or the presence of liquid water clouds impacts the ability to reliably detect snow water equivalent. Moreover, changes in the condition of the snowpack, especially in the surface features, negatively affect retrieval performance. Copyright © 2011. This article is a U.S. Government work and is in the public domain in the USA.     

Space-time soil wetness variations monitoring by a multi-temporal microwave satellite records analysis

In the last few years, remote sensing observations have become a useful tool for providing hydrological information, including the quantification of the main physical characteristics of the catchment, such as topography and land use, and of its variables, like soil moisture or snow cover. Moreover, satellite data have also been largely used in the framework of hydro-meteorological risk mitigation.Recently, an innovative Soil Wetness Variation Index (SWVI) has been proposed, using data acquired by the microwave radiometer AMSU (Advanced Microwave Sounding Unit) which flies aboard NOAA (National Oceanic and Atmospheric Administration) satellites.SWVI is based on a general approach for multi-temporal satellite data analysis (RAT - Robust AVHRR Techniques). This approach exploits the analysis of long-term multi-temporal satellite records in order to obtain a former characterization of the measured signal, in term of expected value and natural variability, providing a further identification of signal anomalies by an automatic, unsupervised change-detection step. Such an approach has already demonstrated, in several studies carried out on extreme flooding events which occurred in Europe in the past few years, its capability in reducing spurious effects generated by natural/observational noise. In this paper, the proposed approach is applied to the analysis of the flooding event which occurred in Europe (primarily in NW Spain) in June 2000. Results obtained, in terms of reliability as well as efficiency in space-time monitoring of soil wetness variation, are presented. Future prospects, in terms of exportability of the methodology on the new dedicated satellite missions, like ESA-SMOS and NASA-HYDROS, are also discussed.     

2003年淮河流域暴雨期间OLR与Quick Scat场特征分析

介绍了在2003年6月21日～7月10日淮河暴雨期间卫星定量资料(OLR、AMSU、QUICKSCAT等)在监测暴雨与洪水中的应用情况.并得到了如下结果①雨带位于OLR低值区170～220W·m-2范围内,并随OLR低值区做南北向摆动;②OLR低值区与暴雨期间四支输送带有较好的对应关系;③使用QuickScat资料分析了越赤道气流、季风与水汽输送之间的关系;④使用国家卫星气象中心的AMSU资料分析了淮河流域发生的中尺度云团中降水最可能出现的位置.为提高暴雨预报的精度提供了新的概念.     

AMSU资料变分同化及在暴雨数值模拟中的应用研究

在中尺度数值模拟中,利用中国气象科学研究院数值天气预报创新基地开发的GRAPES三维变分同化系统,对AMSU-A/B微波遥感资料进行了同化试验,研究了这种资料在我国夏季暴雨数值预报中的作用。以2003年7月4日的一次暴雨过程为例,分析了同化结果及模拟结果,结果表明:(1)单独同化AMSU-A资料主要改进了初始温度场,而单独同化AMSU-B资料主要改进了初始湿度场;(2)无论是同化AMSU-A资料还是同化AMSU-B资料,对暴雨预报都有一定的改进作用,但是同化AMSU-B资料的改进作用更明显;(3)同时同化AMSU-A/B资料比只使用其中一种资料的模拟效果好,可以更好地改进模拟的暴雨落区及强度,使结果与实况更加接近。使用AMSU资料,对我国夏季暴雨数值预报有改进作用。     

A scheme for estimating tropical cyclone intensity using AMSU-A data

Brightness temperature anomalies measured by the Advanced Microwave Sounding Unit （AMSU） on the National Oceanic and Atmospheric Administration （NOAA） polar-orbiting series are suited to estimate tropical cyclone （TC） intensity by virtue of their ability to assess changes in tropospheric warm core struc-ture in the presence of clouds. Analysis of the measurements from different satellites shows that the variable horizontal resolution of the instrument has significant effects on the observed brightness temperature anoma-lies. With the aim to decrease these effects on TC intensity estimation more easily and effectively, a new simple correction algorithm, which is related to the product of the brightness temperature gradient near the TC center and the size of the field-of-view （FOV） observing the TC center, is proposed to modify the observed anomalies. Without other measurements, the comparison shows that the performance of the new algorithm is better than that of the traditional, physically-based algorithm. Furthermore, based on the correction algorithm, a new scheme, in which the brightness temperature anomalies at 31.4 GHz and 89 GHz accounting for precipitation effects are directly used as the predictors with those at 54.94 GHz and 55.5 GHz, is developed to estimate TC intensity in the western North Pacific basin. The collocated AMSU-A observations from NOAA-16 with the best track （BT） intensity data from the Japan Meteorological Agency （JMA） in 2002-2003 and in 2004 are used respectively to develop and validate regression coefficients. For the independent validation dataset, the scheme yields 8.4 hPa of the root mean square error and 6.6 hPa of the mean absolute error. For the 81 collocated cases in the western North Pacific basin and for the 24 collocated cases in the Atlantic basin, compared to the BT data, the standard deviations of the estimation differences of the results are 15% and 11% less than those of the CIMSS （Cooperative Institute for Meteorological Satellite Studies, Univ     

应用AMSU资料监测中国地区雪盖的初步研究

根据微波遥感积雪的原理, 提出了利用NOAA-16 AMSU的1通道 (23.8 GHz)、2通道 (31.4 GHz) 和15通道 (89.0 GHz) 等3个通道监测中国五大区域雪盖范围的初步判识方法。由该方法制作合成了2001年10月1日至2002年4月1日中国地区的周积雪覆盖监测图, 与来自全国气象台站的地面积雪观测记录以及美国人机交互式冰雪制图系统 (I nteractive Snow and Ice Mapping System, IMS) 的雪盖图、SSM/ I (Special Sensor Microwave Imager) 雪盖图的比较结果表明:AMSU监测结果不仅具有比较高的准确性, 而且其准确性和可靠性达到甚至优于其它两种积雪监测结果 (尤其是雪季中期)。     

COSMIC数据验证AMSU平流层低层观测的初步分析结果

基于Global Positioning System (GPS)掩星数据在平流层具有较高准确性、稳定性的优势,本文尝试用新一代GPS掩星观测——the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC)资料验证不同卫星平台上先进的微波探测仪（AMSU）的平流层观测结果.通过COSMIC大气温度廓线与AMSU辐射传输模式结合,得到模拟亮温,然后与AMSU平流层观测进行匹配比较.分析表明GPS掩星数据能够作为一个相对独立的参量检验NOAA15、16、18卫星平台内部的偏差.通过一年数据的比较验证,初步显示不同卫星平台的AMSU观测亮温在平流层低层都偏低,并且NOAA18平台的亮温偏低程度明显大于NOAA15、16.AMSU亮温偏差在极地冬季较为显著,尤其南极地区NOAA18的偏差幅度达到1.8 K.结合24小时内AMSU观测亮温偏差变化及其样本分布特征,可以看到明显的太阳辐射差异可能是导致AMSU观测亮温在极地偏差显著的主要原因.     

ATOVS资料在淮河暴雨预报中的同化应用研究

ATOVS资料的获取弥补了测站稀少地区常规观测资料的不足,尤其是有云条件下的温湿资料,这两种资料对于模式的降水预报极为重要。采用T213-SSI业务系统,对全球NOAA16、17的ATOVS资料进行同化试验,分析了ATOVS资料在极端暴雨天气预报中的应用效果。对2007年7月7—9日发生在淮河流域的一次暴雨过程进行数值模拟研究,设计3种同化方案,对比分析了不同方案的同化模拟结果。试验表明:长期同化AMSU资料,可以改善降水预报,尤其是降水强度的改善明显。通过连续同化,卫星资料能改进大尺度环境场、温湿场和动力场。剔除AMSU-A地面通道及低层700 hPa通道资料的同化效果要优于全部同化,对于暴雨中心的模拟位置、强度有较明显改进,中高层形势场的降水直接影响系统也更加接近实况,温湿场、风场的调整作用尤其明显。     

对于一次川渝暴雨的ATOVS资料同化数值模拟

利用我国全球中期数值预报业务模式T213L31及其三维变分同化系统SSI,对全球NO—AAl6、17的ATOVS资料进行了同化试验。对2007年7月16-18日发生在川渝地区的一次暴雨过程进行数值模拟研究,对比分析了仅同化常规资料与加入卫星资料后的同化结果及模拟结果。试验表明：T213L31模式加入同化AMSU资料后,可以改善降水预报,尤其是降水强度。通过连续滚动同化卫星资料,模式对于大尺度环境场改进明显,模拟效果更加接近实况。AMSU资料的使用可以改进温度场、湿度场以及风场,对于降水落区的预报有很好的指示意义。同化AMSU资料虽然一定程度上增加了降水区的湿度,但是该区域为一个稳定维持的低湿中心占据,是造成降水落区出现偏差的原因。     

AMSU资料揭示的不同强度热带气旋热力结构特征

运用美国NOAA-16极轨气象卫星高分辨率的AMSU探测资料和邻近时刻的NCEP数值预报资料，对2002年6月10日至9月10日发生在西北太平洋上的12个热带气旋生命史中的部分时次作了热力结构分析。发现AMSU资料不仅能够敏感地探测到不同强度热带气旋的多种地球物理参数，并且通过对这些参数的进一步处理，能够展示出它们各自重要的热力结构特征；由不同强度热带气旋对流层中上层暖异常区的高度、强度、范围和形状的差异以及其对流层上层温度负距平的高度、大小和分布不同，结合相应的湿度场结构特征，可以探寻其热力结构与气压变化之间的内在联系，通过这种热力结构的变化趋势可以进一步揭示出热带气旋未来的强度变化。