基于星载微波辐射低频双极化通道观测数据的微波辐射传输模型

微波辐射传输方程是海洋-大气微波遥感的理论基础,本文基于晴空条件下AMSR-E 10.7GHz水平与垂直极化亮温数据,将平静海面的亮温观测结果与4种海水相对电容率模型和2种大气水汽吸收模型的计算结果进行比较,确定了海水相对电容率模型与水汽吸收模型,基于上述模型和实测亮温数据反演了风致各项同性海面发射率,其与已有的经验模型结果基本一致,由此建立了星载微波辐射传输模型;利用建立的辐射传输模型计算亮温与AMSR-E观测亮温分别反演了海表面温度与海表面风速,验证了所建微波传输模型的有效性。本文的研究结果可为星载微波辐射计亮温定标、海洋地球物理参数提取奠定基础。     

HY-2微波辐射计降雨条件下海面风速反演算法研究

由于降雨改变了海洋-大气的辐射/散射特性,长期以来星载遥感器在降雨条件下进行海面风速信息提取存在困难。本文针对自主海洋动力环境卫星海洋2号（HY-2）搭载的扫描微波辐射计,分析了不同频段亮温对降雨和海面风速敏感性,自此基础上获得了一种对降雨不敏感的亮温通道组合,该亮温通道组合对海面风速的敏感性甚至高于原有亮温通道。本文利用该亮温通道组合建立了降雨条件下的风速反演算法,并将反演结果与WindSat全天候风速产品、HY-2微波辐射计原有风速产品以及浮标实测数据进行了比较。结果表明本文算法在降雨条件下的反演误差小于2m/s,明显优于原有HY-2微波辐射计风速产品,验证了本文发展的算法在降雨条件下的风速反演能力。     

基于南太平洋的AMSR2L1R亮温数据质量评估

本文基于环境场较为稳定的南太平洋目标海区,以海洋大气微波辐射传输模型(Radiative Transfer Model,RTM)模拟亮温作为参考值,对2015年1月1日—2017年12月31日的高级扫描微波辐射计(Advanced Microwave Scanning Radiometer 2,AMSR2) L1R亮温数据产品进行了质量评估。结果表明AMSR2 L1R所有通道亮温数据总偏差和标准偏差的变化范围分别为1.466～6.352 K、0.270～1.693 K,其中标准偏差在水平极化通道较大的同时随着频率的增大而增大。相比同类遥感器如全球降水测量微波成像仪(Global Precipitation Measurement Microwave Imager,GMI)等的质量分析结果,AMSR2亮温数据的标准偏差较小,这表明AMSR2亮温数据精度较高。对AMSR2 L1R亮温数据3年长时间序列的变化趋势分析表明所有通道亮温偏差均在±0.5 K范围内波动但是存在微弱的季节性变化,标准偏差随时间的变化较小,这表明AMSR2 L1R亮温数据质量较为稳定。     

基于一维综合孔径微波辐射计的大气海洋环境参数敏感性分析

相比于实孔径微波辐射计,一维综合孔径微波辐射计具有高空间分辨率和多入射角观测特点.本文提出采用观测频率为6.9,10.65,18.7,23.8和36.5 GHz,且入射角范围为0°～65°的一维综合孔径微波辐射计遥感大气海洋环境要素.基于构建的微波大气海洋辐射传输正演模型,分析了辐射计亮温对大气海洋环境要素的敏感性,为...     

用19.35 GHz星载微波辐射计(SSM/I)亮温反演海面风速

我们发展了一种用19．35GHz星载微波辐射计(SSM／I)亮温反演海面风速的模式，并利用同步的卫星亮温和海面浮标数据反演出海面风速，并且和浮标风速进行比较。为了说明反演算法的可用性，我们分别与目前国际上的通用反演算法的反演结果进行了比较。文章提供了一种新的、用单一波段亮温反演海面风速的方法。     

微波辐射计遥感海洋盐度的研究进展

介绍了微波辐射计遥感海洋盐度的原理,回顾了在海水微波辐射亮度温度模型,机载、星载微波辐射计遥感海洋盐度实验,以及星载微波辐射计研究计划方面的进展。指出了为提高海洋盐度测量精度和空间分辨率,在盐度遥感机理、微波辐射计、及盐度反演研究方面的发展趋势。     

基于一维综合孔径微波辐射计的海面温度反演研究

Due to the low spatial resolution of sea surface temperature(T_S) retrieval by real aperture microwave radiometers,in this study, an iterative retrieval method that minimizes the differences between brightness temperature(T_B)measured and modeled was used to retrieve sea surface temperature with a one-dimensional synthetic aperture microwave radiometer, temporarily named 1 D-SAMR. Regarding the configuration of the radiometer, an angular resolution of 0.43° was reached by theoretical calculation. Experiments on sea surface temperature retrieval were carried out with ideal parameters; the results show that the main factors affecting the retrieval accuracy of sea surface temperature are the accuracy of radiometer calibration and the precision of auxiliary geophysical parameters. In the case of no auxiliary parameter errors, the greatest error in retrieved sea surface temperature is obtained at low T_S scene(i.e., 0.710 6 K for the incidence angle of 35° under the radiometer calibration accuracy of0.5 K). While errors on auxiliary parameters are assumed to follow a Gaussian distribution, the greatest error on retrieved sea surface temperature was 1.330 5 K at an incidence angle of 65° in poorly known sea surface wind speed(W)(the error on W of 1.0 m/s) over high W scene, for the radiometer calibration accuracy of 0.5 K.     

基于Argo浮标数据的星载微波辐射计Aquarius数据产品质量评估

Aquarius是专门用于海洋盐度监测的L波段辐射计,于2011年6月发射入轨,目前已进入业务化运行阶段。本文以太平洋为研究区域,利用Argo盐度现场数据对星载微波辐射计Aquarius的2012年2级数据产品质量进行了分析与讨论,结果表明:与Argo数据比较,Aquarius数据盐度存在0.1的负偏差,标准差约为0.7,升轨和降轨数据差异不明显;受亮温陆地污染和无线电射频干扰的影响,近岸海域反演误差较大;海面温度较高的低纬海域反演结果优于中纬度海域;受亮温敏感性及粗糙海面发射率模型的影响,Aquarius在低温水域以及高风速条件下盐度反演误差较大,标准差可达1以上。     

基于亚马逊热带雨林的微波辐射计定标基准分析

亚马逊热带雨林作为稳定地物目标,适合进行星载微波辐射计的外定标。但近些年亚马逊热带雨林受人为破坏严重,植被覆盖面积减少,植被覆盖率降低,适合进行外定标的区域较往年发生了变化。文中依据亚马逊热带雨林近些年的归一化植被指数(NDVI)的变化情况,发现纬度位于3°S^2°N,经度位于74°W^69°W范围内的区域植被覆盖率高,适合进行星载微波辐射计外定标。文中以AMSR2 L1R亮温数据为基准,对比分析了该区域在2015-2017年3 a的亮温变化趋势,并以此作为该区域的定标基准。分析发现,该区域在非厄尔尼诺事件期间的亮温变化趋势呈现出特定的季节变化规律:在每年的6-7月,亮温值达到最低;在11-12月,亮温值达到最高,7-11月波动上升,12-6月波动下降。在厄尔尼诺事件发生期间会出现亮温值异常现象。     

星载微波辐射计空间分辨率增强算法研究

由于天线尺寸和重量受到限制,星载微波辐射计的空间分辨率通常都比较低.同时在测量地理参数时往往要用到辐射计的多个频率通道测量值,这就需要把不同通道的空间分辨率统一成某个较高空间分辨率.因此,出于应用的目的,利用微波辐射计空间分辨率增强算法来得到较高分辨率的图像很有必要.简单介绍了增强星载微波辐射计图像空间分辨率的几种算法,详细叙述了Backus-Gilbert反演算法的原理.设计了带有一些地物特征的人工合成图像,并使用BG反演算法对一模拟辐射计的生成图像进行了增强处理.从处理前后的图像对比可知,无论辐射计测量是否含有噪声,BG反演算法都很好地提高了辐射计生成图像的空间分辨率.在考虑噪声时,通过分析增强处理后图像与人工合成图像之间的相关性,仔细挑选协调参数,对分辨率和噪声进行了较好的折中处理.     

Monitoring Measurements from the Jason-1 Microwave Radiometer and Independent Validation with GPS

The Jason-1 Microwave Radiometer (JMR) provides measurements of the wet troposphere content to correct the altimetric range measurement for the associated path delay. Various techniques are used to monitor the JMR wet troposphere path delays, with measurements of zenith troposphere content from terrestrial GPS sites used as an independent verification technique. Results indicate that an unexpected offset of approximately +4.1 ± 1.2 mm (drier) emerged in the JMR measurements of wet path delay between cycles 28-32 of the Jason-1 mission, and that the measurements may be drifting at a rate of approximately -0.5 mm/year. These anomalies are shown to be caused by a -0.7 K offset in 23.8 GHz brightness temperatures between cycles 28-32, and a 0.16 ± 0.04 and -0.45 ± 0.08 K/year drift in the 18.7 and 34.0 GHz brightness temperatures, respectively. Intercomparison of the 3-Hz JMR brightness temperature measurements show that they have been drifting with respect to each other, and that a dependence on yaw-steering regime is present in these measurements. An offset of 0.5 m/s between cycles 28-32 and a drift of approximately 0.5 m/s/year in the JMR wind speed measurements is also associated with these anomalies in the 1-Hz brightness temperatures. These errors in JMR wind speeds presently have a negligible impact on the retrieved JMR path delays.     

Monitoring Measurements from the Jason-1 Microwave Radiometer and Independent Validation with GPS

The Jason-1 Microwave Radiometer (JMR) provides measurements of the wet troposphere content to correct the altimetric range measurement for the associated path delay. Various techniques are used to monitor the JMR wet troposphere path delays, with measurements of zenith troposphere content from terrestrial GPS sites used as an independent verification technique. Results indicate that an unexpected offset of approximately +4.1 ± 1.2 mm (drier) emerged in the JMR measurements of wet path delay between cycles 28–32 of the Jason-1 mission, and that the measurements may be drifting at a rate of approximately ?0.5 mm/year. These anomalies are shown to be caused by a ?0.7 K offset in 23.8 GHz brightness temperatures between cycles 28–32, and a 0.16 ± 0.04 and ?0.45 ± 0.08 K/year drift in the 18.7 and 34.0 GHz brightness temperatures, respectively. Intercomparison of the 3-Hz JMR brightness temperature measurements show that they have been drifting with respect to each other, and that a dependence on yaw-steering regime is present in these measurements. An offset of 0.5 m/s between cycles 28–32 and a drift of approximately 0.5 m/s/year in the JMR wind speed measurements is also associated with these anomalies in the 1-Hz brightness temperatures. These errors in JMR wind speeds presently have a negligible impact on the retrieved JMR path delays.     

外定标中海面参数对发射率影响研究

星载微波辐射计外定标的关键问题是通过辐射传输方程计算天线入瞳处亮温。根据辐射传输方程,海面成份对亮温的影响包括海面的微波辐射和对下行大气辐射的反射,其中的关键参数分别为海面发射率ep和海表面反射率R。文中对平静海面Fresnel反射率模式和粗糙海面反射率模式进行了研究分析,在此基础上着重研究了海面温度TS、海面盐度SS、海面风速W、以及观测角度θ等物理参数对海面发射率ep的影响,进而分析了这些物理参数的测量误差对亮温的计算精度的影响。     

星载红外辐射计海上辐射校正方法研究

以FY-1D卫星的热红外通道为例,利用2003年黄东海海上试验站点及其周围海域对辐射校正原理进行了分析研究,包括对现场辐亮度的测量、星地光谱匹配、大气辐射传输计算、辐射校正系数获取等方面的研究。     

基于Jason-2校正辐射计的降雨率估计算法研究

采用Jason-2校正辐射计的亮温数据与GPM Ku波段测雨雷达的降雨率数据,开展基于Jason-2校正辐射计的降雨率估计算法研究。为避免波束填充效应,对Ku波段测雨雷达降雨率数据进行网格化处理,分别构建3×3,5×5及7×7网格的建模数据集和验证数据集,通过建模数据集建立了3种基于校正辐射计的降雨率估计算法研究,并通过验证数据集进行检验。结果表明:对GPM Ku波段测雨雷达的降雨数据进行3×3,5×5及7×7的网格化处理,可以在降雨率估计算法研究时有效避免波束填充效应,7×7网格化处理方法效果最优。对3种不同的算法比对,发现利用校正辐射计3个通道亮温信息的线性组合形式估计降雨率效果最优,相对偏差可达42.33%。     

Assessment of the Jason-1 and TOPEX/Poseidon Microwave Radiometer Performance Using GPS from Offshore Sites in the North Sea

The accuracy and drift of atmospheric path delay due to water vapor as derived from satellite microwave radiometers (MWR) is vital to altimetric measures of sea-level change. In this study a continuous time series of dual frequency GPS data from a number of offshore sites is used to examine the long term stability of the TOPEX/Poseidon radiometer and investigate initial performance of that of Jason-1. The location offshore eliminates the problems associated with land based/coastal locations where extrapolation of the GPS tropospheric correction to subsatellite points offshore are required to avoid background surface heat emissions contaminating the MWR delay measurement.     

SMAP卫星辐射计在中国近海及沿岸的RFI特征分析

射频干扰RFI(Radio-Frequency Interference)的校正和抑制一直是微波遥感研究领域的重要问题之一。本文基于SMAP卫星2015年5月1日至5日L波段辐射计亮温数据对中国近海及沿岸的射频干扰进行了特征分析。研究发现RFI分布不均匀,主要集中在城市群及其周边地区;通过对比辐射计天线接收的亮温数据与射频干扰校正和抑制后的数据,发现研究区域主要的射频干扰(95%)的平均值为1.4 K,整体射频干扰平均值为2.5 K,标准差为6.5;研究区域中不同波段和极化的数据受到射频干扰影响较为相似,受射频干扰影响最大的是升轨的垂直极化数据,受影响最小的是升轨的水平极化数据。     

由TSRB辐射计数据估算海面离水辐亮度的经验方法

为建立基于经验统计的TSRB辐射计数据估算离水辐亮度的方法,利用SeaBASS数据库中640多个现场测量的辐亮度和辐照度光谱剖面数据,建立向上辐亮度衰减系数K_(lu)的经验算法.此算法为幂指数形式,输入变量为水下0.65 m的向上辐亮度(490 nm)与海面上向下的辐照度(555 nm或665 nm)之比(即为TSRB直接测量的两个参数).当水体较清时,输入为蓝绿波段之比,当水混浊时,采用蓝红波段之比.获得了K_(lu)后,海面以上的辐亮度(离水辐亮度)由z=0.65 m处的辐亮度外推获得.初步的检验结果表明,该方法对一类和二类水域都有很好性能,且算法实现简单,运行速度快.     

Improved Algorithms for the Measurement of Total Precipitable Water and Cloud Liquid Water from SARAL Microwave Radiometer Observations

SARAL carried onboard a radar altimeter that provides very precise measurements of the sea surface height (SSH). Like other altimetric missions, SARAL carries a passive microwave radiometer (PMR) for wet tropospheric correction to SSH. In the present study, new algorithms are developed for the retrieval of cloud liquid water (CLW) and total precipitable water vapor (TPW) over the global oceans from PMR measurements of the brightness temperatures. A radiative transfer and genetic algorithm based retrieval scheme is proposed for the estimation of CLW and TPW from SARAL PMR. The comparisons of CLW from PMR with independent measurements from GPM-GMI and SSMIS within and outside ±40° latitudes show correlation (R) of 0.86 and 0.83, bias of 0.7 and ?3.61?mg/cm², and root mean square error (RMSE) of 8.42 and 8.07?mg/cm², respectively. Similarly, TPW from PMR with GPM-GMI and SSMIS show R of 0.99 and 0.98, bias of ?0.04 and ?0.03?g/cm² and RMSE of 0.17 and 0.17?g/cm², respectively. The retrieval accuracy of CLW and TPW from the new algorithms is compared with these parameters provided in the SARAL geophysical data records as finished products, which showed substantial improvement in the quality of the parameters from the new algorithm.     

Cross-Calibration and Long-Term Monitoring of the Microwave Radiometers of ERS,TOPEX, GFO,Jason, and Envisat

The radiometers on board the satellites ERS-1, TOPEX/Poseidon, ERS-2, GFO, Jason-1, and Envisat measure brightness temperatures at two or three different frequencies to determine the total columnal water vapor content and wet tropospheric path delay, a major correction to the altimeter range measurements. In order to asses the long-term stability of the path delay, the radiometers are calibrated against vicarious cold and hot references, against each other, and against several atmospheric models. Four of these radiometers exhibit significant drifts in at least one of the channels, resulting in yet unmodeled errors in path delay of up to 1 mm/year, thus limiting the accuracy at which global sea level rise can be inferred from the altimeter range measurements.