A Three-Dimensional Satellite Retrieval Method for Atmospheric Temperature and Moisture Profiles

A three-dimensional variational method is proposed to simultaneously retrieve the 3-D atmospheric temperature and moisture profiles from satellite radiance measurements. To include both vertical structure and the horizontal patterns of the atmospheric temperature and moisture, an EOF technique is used to decompose the temperature and moisture field in a 3-D space. A number of numerical simulations are conducted and they demonstrate that the 3-D method is less sensitive to the observation errors compared to the 1-D method. When the observation error is more than 2.0 K, to get the best results, the truncation number for the EOF＇s expansion have to be restricted to 2 in the 1-D method, while it can be set as large as 40 in a 3-D method. This results in the truncation error being reduced and the retrieval accuracy being improved in the 3-D method. Compared to the 1-D method, the rms errors of the 3-D method are reduced by 48% and 36% for the temperature and moisture retrievals, respectively. Using the real satellite measured brightness temperatures at 0557 UTC 31 July 2002, the temperature and moisture profiles are retrieved over a region （20°-45°N, 100°- 125°E） and compared with 37 collocated radiosonde observations. The results show that the retrieval accuracy with a 3-D method is significantly higher than those with the 1-D method.

Application of wind profiler data to rainfall analyses in Tazhong Oilfield region,Xinjiang,China

To improve the level of meteorological service for the Oilfield region in the Taklimakan Desert, the Urumqi Institute of Desert Meteorology of the China Meteorological Administration （CMA） conducted a detection experiment by means of wind profiling radar （WPR） in Tazhong Oilfield region of Xinjiang, China in July 2010. By using the wind profiler data obtained during the rainfall process on 27 July, this paper analyzed the wind field fea- tures and some related scientific issues of this weather event. The results indicated that： （1） wind profiler data had high temporal resolution and vertical spatial resolution, and could be used to analyze detailed vertical structures of rainfall processes and the characteristics of meso-scale systems. Before and after the rain event on 27 July, the wind field showed multi-layer vertical structures, having an obvious meso-scale wind shear line and three airflows from different directions, speeding up the motion of updraft convergence in the lower atmosphere. Besides, the wind directions before and after the rainfall changed inversely with increasing height. Before the rain, the winds blew clockwise, but after the onset of the rain, the wind directions became counterclockwise mainly; （2） the temperature advection derived from wind profiler data can reproduce the characteristics of low-level thermodynamic evolution in the process of rainfall, which is capable to reflect the variation trend of hydrostatic stability in the atmosphere. In the early stage of the precipitation on 27 July, the lower atmosphere was mainly affected by warm advection which had accumulated unstable energy for the rainfall event and was beneficial for the occurrence of updraft motion and precipitation; （3） the ＂large-value zone＂ of the radar reflectivity factor Z was virtually consistent with the onset and end of the rainfall, the height for the formation of rain cloud particles, and precipitation intensity. The reflectivity factor Z during this event varied approximately in the range of 18-38 dBZ and the rain droplets formed mainly at the layer of 3,800-4,500 m.

Physics-based simultaneous retrieval of atmospheric temperature-humidity profiles and land surface temperature-emissivity by integrating Terra/Aqua MODIS measurements

Atmospheric temperature-humidity profiles and land or sea surface temperature are coupled actions in the earth system process. Based on the numerical perturbation form of the atmospheric radiative transfer equation, a physics-based algorithm is pre- sented to integrate four pairs of MODIS measurements from the Terra and Aqua satellites to retrieve simultaneously atmospheric temperature-humidity profile, land-surface temperature and emissivity. Three pairs of MODIS data at two field sites in China, Luancheng and Poyang Lake areas, have been chosen to test and validate the model. Two pairs of atmospheric tem- perature and humidity profiles, land surface temperature (LST), and land surface emissivity (LSE) have been retrieved simul- taneously for every pair of MODIS measurements respectively by the proposed physical algorithm for the study area. The synchronous field measurements at two field sites were conducted to validate the retrieval LST, the differences between the retrieved LST and the field measurements are in the range of -0.15 K and 1.11 K. The emissivity errors of MODIS bands 31 and 32, compared with the EOS MODIS LST/LSE data products (MOD11_L2/MYD11_L2 V5) by the physics-based day/night algorithm, are from 0.0018 to 0.44 and from 0.0058 to 1.24, respectively. Meanwhile, the retrieved atmospheric profiles fully agree with the standard atmospheric temperature-water vapor profiles and with the results from single MODIS data onboard Terra or Aqua satellite by the former two-step physical algorithm. Therefore, the proposed algorithm is robust enough to improve the retrieval accuracy of the atmospheric profiles and land surface parameters. And it will have four pairs of the retrieval results for one area each day by integrating these MODIS measurements from Terra and Aqua satellites.

Regional Profiles and Precipitation Retrievals and Analysis Using FY-3C MWHTS

The 89 and 150 GHz channels operated in window are sensitive to precipitation and humidity. The 183 GHz humidity-sensitive channels and 118 GHz temperature-sensitive channels of the Microwave Humidity and Temperature Sounder (MWHTS) on the Chinese Feng Yun 3C MWHTS (FY-3C MWHTS) polar-orbit meteorological satellite responds in part to precipitation. Combining 118 and 183 GHz channels, the paper develops a passive sub-millimeter atmospheric profile and precipitation retrievals algorithm for MWHTS onboard the FY-3C (Feng Yun-3C) satellite. The retrieval algorithm employs a number of back propagation neural network estimators trained and evaluated using the validated global reference physical model NCEP/WRF/ARTS and works for land and seawater with latitude between -40 to 40 degree. NCEP data per 6 hours were downloaded to run the Weather Research and Forecast model WRF, and to derive the typical precipitation data for the whole world. The Atmospheric Radiative Transfer Simulator ARTS is feasible for performing simulations of atmospheric radiative transfer. The results show that the profile retrievals using BP-NN algorithm has the best correlation with those from radiosonde, which is less than 18% and 1 K of root mean square error, respectively. For precipitation rate retrievals, a much better agreement is reached with rain gauge and ECMWF datasets, the RMS is between 0.80 to 30.24 mm/h for sea surface and 0.789 to 33.11 mm/h for land surface according to the classification by precipitation type. Also, the analysis of retrievals located in Tibetan plateau is provided as an example to justify the robustness and performance of retrieving model.

沈阳2次重污染天气过程的风廓线雷达观测结果对比分析

为进一步研究重污染天气的形成机理,利用风廓线雷达资料、常规气象观测资料和大气污染物监测资料,对2015年11月6—10日和2019年3月2—6日(分别简称“过程Ⅰ”和“过程Ⅱ”)沈阳2次重污染天气过程进行对比分析,重点总结风廓线雷达直接探测产品和反演产品的演变特征。结果表明:过程Ⅰ,污染重,污染物浓度增速快,能见度持续偏低,下沉速度大,动力条件更稳定,且雷达接收的气象回波信号强。低层始终维持高强度的暖平流,为污染物浓度达到异常峰值提供强力的暖湿条件。过程Ⅱ,污染相对较轻,冷、暖平流交替出现,使污染物浓度呈波动式上升,增速慢,能见度存在日变化,下沉速度小,且雷达接收的气象回波信号弱。2次重污染过程都受外来污染物输送影响,但输送路径不同。

FY-4 A/GIIRS反演夏冬季有云时大气温湿度廓线的精度评估

FY-4A/GIIRS(Geostationary Interferometric Infrared Sounder)首次实现了地球静止轨道红外高光谱探测,可以连续获得高垂直分辨率的大气温度和湿度廓线信息。当GIIRS视场内有云存在时,目前Level 2业务大气温湿度垂直廓线产品只提供观测视场内云顶以上高度的温度廓线,且不反演整个视场的湿度廓线。基于GIIRS辐射观测值用U-Net卷积神经网络算法实现了全天空大气温湿度廓线反演,包括晴空和全云覆盖视场,同时利用常规无线电探空观测资料对反演精度进行了检验。结果表明:U-Net算法有云视场的温湿度廓线反演能力与晴空相当,且夏季温度反演精度优于冬季,有利于灾害性天气多发季节的监测。在云系较活跃的夏季,随着视场内云量的增加温度廓线反演精度逐渐变高,表明该算法适用于有云时大气温度廓线反演,而湿度随着云量的增加反演均方根误差RMSE增大。视场内不同云光学厚度时温度反演误差相差不大,RMSE均在2.5 K左右,平均偏差ME在1 K以内,对流层高层薄云时反演误差相对而言较小。湿度反演随着云光学厚度的增大反演误差也增大,说明对于一定程度的薄云,GIIRS能够获得不错的反演精度。虽然U-Net算法物理意义不明确,但是能够快速实现全天空大气温湿度廓线反演,尤其在有云时能够获得更高的反演精度。

多目标遗传算法反演对流层大气温湿廓线研究

针对地基微波辐射计反演对流层大气温湿廓线完全依赖于历史数据的问题,设计了一种新的反演算法和流程。在对历史探空数据的统计分析基础上,得到各层大气温湿参数经验范围。从经验库中随机构造一条大气温湿廓线作为初值,基于大气微波辐射传输模式MonoRTM模型,计算模拟亮温。比较计算值与实测亮温的接近程度,通过更新初值,不断迭代计算,逐步筛选出可行解,并通过设定大气温湿垂直递减率等约束条件,从可行解中约束出帕累托前沿。采用皮尔逊系数加权平均的方法,从帕累托前沿中得到全局满意解。研究结果表明,新建立的基于多目标遗传算法的不完全依赖于历史数据的对流层大气温湿廓线反演模型,有较好的自适应能力和鲁棒性,反演精度高。该模型可以满足微波辐射计在历史气象资料积累匮乏地区的使用需求。

Evaluation of Terra/MODIS atmospheric profiles product(MOD07)over the Iberian Peninsula:a comparison with radiosonde stations

Remote sensing techniques are a useful tool for continuous observation of the Earth at global scale.However,products derived from remote sensing data require a rigorous validation using in situ data.Moderate Resolution Imaging Spectroradiometer(MODIS)is not really a sounding instrument,but it does have 16 infrared bands(bands 20-36 covering the spectral range from 3μm to 14μm)that allow the retrieval of temperature and moisture profiles as well as total column integrated magnitudes.In this paper we show the results obtained in the evaluation of MOD07 daytime and nighttime products over the Iberian Peninsula during the decade from 2000 to 2010 using nine radiosonde stations.Although MODIS limitations in comparison with other sounding instruments,the validation provided satisfactory results,with bias(MOD07 minus radiosonde)<0.3 cm and a standard deviation of 0.5 cm for the total column water vapor,and bias around 1 K on average with standard deviations between 2 K and 3 K for air temperature at different pressure levels.On average,bias was positive and below 2 K with standard deviations around 5 K for the dew point temperature case.Large errors were found in this case for pressure levels higher than 50 hPa.

RETRIEVING ATMOSPHERIC TEMPERATURE FROM NOAA-15 ATOVS MEASUREMENTS

This paper describes briefly the sounding capabilities of TOVS/ATOVS onboard the NOAA polar-orbiting meteorological satellites,followed by a more detailed review of the retrieval schemes.The ICI physical retrieval scheme with some adaptations is implemented in our experiment.The analyses of the Chinese regional NWP model are utilized to create a rolling library of initial guess field.Retrieval results validated against both NWP analyses and radiosondes indicate good agreement between ICI retrievals and conventional observations.Preliminary result from the PC-ATOVS Windows display system of NSMC will also be shown.

FY-4A GIIRS高时间分辨率温湿度廓线反演及其在台风中的应用

针对2020年第9号台风“美莎克”期间FY-4A高光谱红外干涉式大气垂直探测仪GIIRS每15 min一次的目标区跟踪加密观测资料,用三维卷积神经网络算法反演的全天空大气温度、湿度廓线分析了台风处于生命史不同阶段时暖心结构和湿度场结构的演变特征。结果表明:卷积神经网络的深度机器学习算法可以用来反演全天空的三维大气温度和湿度垂直廓线,不光适用范围广(晴空和有云视场)、反演精度高,而且反演速度快。利用静止卫星平台高时间分辨率的特性,反演得到的温度、湿度廓线可以细致追踪台风处于发展、成熟和登陆等阶段时暖心结构和湿度场的时空演变特征。台风从发展阶段(热带风暴和强热带风暴)到成熟阶段至登陆消亡时,暖心首先出现在对流层中高层较薄的区域,随着台风强度的加强,深厚的暖心结构明显、强度增加,水平面积增大且垂直往下延伸。由于对流云中强上升气流的输送水汽正距平区逐渐上传至300 hPa,台风最强时密闭云区与四周下沉气流区比湿差高到8 K·kg^(-1)。暖心结构和高湿度中心随着台风登陆而逐渐消失。

Modification and validation of a new method to improve the accuracy of MODIS-derived dew point temperature over China's Mainland

MODIS atmospheric profile products(MOD07_L2 and MYD07_L2)have been widely used for near-surface dew point temperature(T_(d))estimation.However,their accuracy over large scale has seldom been evaluated.In this study,we validated these two products comprehensively against 2153 stations over China's Mainland.MOD07_L2 was suggested by our study because it achieved higher accuracy in either of two frequently-used methods.To be specific,the root-meansquare error(RMSE)achieved by MOD07_L2 and MYD07_L2 was 5.82 and 7.42℃,respectively.On this basis,a recent ground-based correction method was modified to further improve their accuracy.Our focus is to investigate whether this ground-based approach is applicable to large-scale remote sensing applications.The results show that this new method showed great potential for T_(d) estimation independently from ground observations.Through the introduction of MODIS land surface products,the RMSE it achieved for MOD07_L2 and MYD07_L2 was 5.23 and 5.59℃,respectively.Further analysis shows that it was particularly useful in capturing the annual average T_(d) patterns.The R2,RMSE,and bias of annual average daily mean T_(d) estimates were 0.95,1.84℃,and 0.53℃,and those achieved for annual average instantaneous T_(d) estimates were 0.94,2.09℃,and 0.75℃,respectively.

热层大气密度动态修正模型研究

为构建具有密度误差原理级修正的热层大气模型动态修正软件系统,首先,根据温度垂直剖面计算方法,对拐点和外逸层2个边界温度计算函数按经纬度球谐系数展开,研究基于模型和实测密度估计修正系数的方法;从数值计算方面,将条件方程泰勒展开线性化迭代求解得到修正系数。然后,融合修正理论和数值方法,构建热层大气密度动态修正模型系统。之后,针对磁暴、磁静事件分类评估系统性能,结果显示修正后模型的预报准确性较MSIS00模型显著提升——预报相对误差磁暴期平均下降33.8个百分点,磁静期平均下降9.1个百分点。最后,分析边界温度修正量的序列,得到其主要变化规律。期望通过热层大气模型动态修正系统的研究与实践,为热层大气密度的高精度预测需求提供解决方案。

用于大气温度廓线测量的瑞利-拉曼激光雷达

大气温度廓线及其时间演变特征资料在地球科学领域具有重要的应用,为获取高时空分辨的大气温度的垂直分布,建立了瑞利-拉曼温度测量激光雷达。介绍了瑞利-拉曼激光雷达进行温度测量的主要原理和研制的瑞利-拉曼激光雷达的主要参数;数据处理方面,通过背景噪声剔除和小波算法降噪提高系统的信噪比;使用研制的激光雷达对大气温度廓线进行观测,将观测结果与大气模式数据和卫星观测结果进行对比,均显示较好的一致性,证明了激光雷达温度测量结果的准确性,其温度测量数据可以用于气象学研究。

FY-3A气象卫星红外分光计温度廓线模拟反演试验

为了考察风云三号(FY-3)气象卫星红外分光计的性能,以该仪器初样阶段的光谱通道特征和仪器响应函数为基础,进行大气温度垂直廓线模拟反演。选用红外分光计15μmCO2吸收带的不同通道组合进行模拟反演,结果表明:总体上红外分光计具有较好的大气温度反演能力,窗区通道8的加入可有效提高近地面层温度反演精度;利用迭代算法反演大气温度时,初估廓线对反演精度影响较大,初估廓线与真值愈接近,反演精度愈高;现有仪器通道灵敏度设计指标可满足大气温度反演基本要求,如仪器灵敏度降低,反演精度也随之降低,提高仪器灵敏度,有利于提高仪器的使用效果。

兰州市东部地区冬季低空风场和温度场分析

根据１９９６ 年１２ 月２０ 日至３０ 日在兰州市东部峡口附近地区进行的大气边界层探测试验得到的资料，分析了该地区的低空风、温场垂直分布特征及随时间的演变特征．分析表明：兰州市东部地区从地面到１５０ ｍ 高度的低层风场在受向市中心辐合的热岛环流和不同尺度地形的山谷风影响下，盛行偏东南风，２００ ｍ 高度以上的层结受高空西风的影响盛行偏西北风．白天（０７ 时至１９ 时） 的平均风速比夜晚（１９ 时至０７ 时） 小，而且风速的最小值出现在白天的１５０ ｍ 高度以下．逆温持续时间长、强度大、厚度大，混合层顶在中午１３ 时左右达到最大高度，约３００ ｍ ．另外，通过比较发现：下垫面条件、夜间人工热源、天气系统以及大气的稳定度状况等均对混合层的发展有一定影响．

白洋淀湿地夏末大气边界层温湿廓线特征对比分析

2005年9月北京大学与中国科学院大气物理研究所联合在白洋淀湿地地区开展非均匀下垫面的大气边界层综合野外观测实验,利用新型高精度温湿度探空系统分别在陆地和水面两种下垫面进行连续观测。实验结果显示水陆两种下垫面的大气边界层结构具有明显特征不同时刻、不同高度出现多层逆湿、逆温现象及清晰的边界层顶位置。同时发现该地区的陆地下垫面上空湿度较水面大、温度较低;水面上空湿度较小,温度较高,且水面上空边界层厚度要大于陆地。作者从盛行风向、局地能量平衡、陆气相互作用等方面对实验结果进行分析,结果有助于研究和了解夏秋季节白洋淀湿地地区大气边界层特性和演变规律,为进一步认识白洋淀湿地的水循环及能量平衡提供了参考。观测结果也检验了北京大学自行研制的新型高精度温湿度探空系统的性能。

单通道物理法反演海表温度的参数敏感性分析及验证

定量分析了反演海表温度的单通道物理法对海水比辐射率、海面风速、海水盐度、大气透过率、大气上下行辐射等参数的敏感性,发现海水比辐射率、大气透过率对算法精度影响较大,是单通道物理法反演海表温度的主要误差来源.在不同的波段,单通道物理法对参数敏感性也有较大差别,中红外波段的敏感性要小于热红外波段.为了验证单通道物理法的可行性、精度及参数敏感性分析的结果,选择墨西哥湾海域2009年全年夜间MODIS实测数据进行实验.结果表明,中红外波段的单通道物理法反演海表温度的精度高于热红外波段,达到MODIS劈窗算法海表温度标准产品同等精度,这与参数敏感性分析的结果一致.由于中红外波段单通道物理法精度较高,一方面,可以满足常规的业务观测需求,为海表温度反演提供新的技术手段;另一方面,可用来标定劈窗算法系数,弥补海洋现场观测站位空间分布不足的问题.

利用超光谱红外卫星数据反演大气廓线研究

建立新的物理反演法能同时反演大气温度廓线、水汽廓线、表层温度和地表发射率,该反演算法应用到我国黄海地区AIRS红外卫星资料中,可反演得到较高垂直分辨率的大气温度廓线和水汽廓线,同时反演得到表层温度和地表发射率、根据水汽廓线计算大气可降水量。

用探空资料检验中尺度数值模式对强对流天气的诊断分析能力

提高对流天气临近预报准确率的关键问题之一是了解大气的垂直稳定度和垂直风切变。中尺度数值模式产品提供了高时空分辨率的大气稳定度和垂直风切变信息,需要首先检验其精度才能进一步考虑其在对流天气预报中的应用。利用北京加密探空资料检验北京市气象局3km分辨率的MM5模式结果,对强对流天气的背景参数包括温湿风垂直廓线、对流有效位能CAPE和垂直风切变进行模式分析和预报与探空对比检验。结果表明模式模拟的各种大气廓线中,风廓线和温度廓线都具有一定的参考价值,与实况有较好的一致性,但在廓线出现转折的地方,如逆温层和风向转折时,模式预报较差。露点(湿度)廓线的预报误差较大,不能反映出真实水汽场的分布。因此,模式预报的深层(地面至500hPa)垂直风切变与探空具有较好的一致性,而模式给出的对流有效位能CAPE由于露点预报结果不理想,其值与实际偏差较大。因此模式输出的对流有效位能CAPE必须经过适当订正才能用于诊断强对流天气发生的可能性。

1993年春季南极中山站上空大气臭氧的观测分析

利用球载电化学Ｏ３探空仪于１９９３年南半球春季在南极中山站测量了Ｏ３和温度垂直廓线，三次观测到Ｏ３柱总量＜２２０Ｄｕ的低值，Ｏ３浓度减少从９月开始，９月中旬～１０月中旬达到最大。典型Ｏ３垂直廓线表明，Ｏ３量损失最大区域在高度１３～２３ｋｍ之间，此高度与ＰＳＣｓ和火山气溶胶的存在高度有很好的对应关系。本文给出观测结果及初步分析。