共查询到19条相似文献，搜索用时 484 毫秒
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利用一个微波辐射传输模式，晴天下的大气探测廓线，地面的部分观测资料以及卫星观测的亮温，计算了淮河流域能量和水循环实验(HUBEx)中，寿县地区的热带降雨观测卫星微波成像仪(TRMM／TMI)微波频率的地表比辐射率。通过比较所计算的微波地表比辐射率随地表状况的改变，发现地表微波比辐射率随地表状况的变化存在敏感性，并且其变化是合理的。本中，地表肤温设定等于地表空气温度，并且仅计算了寿县的地表比辐射率，在HUBEx区域上的地表比辐射率的计算需要更多的观测资料。 相似文献
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风云三号卫星微波辐射率资料的质量控制 总被引：2，自引：2，他引：0
利用双权重算法对观测增量（卫星观测亮度温度与用辐射传输模式模拟的背景场亮度温度之差）进行质量控制,模式背景场采用的是NCEP再分析资料,观测算子使用的是RTTOV（9．3v）（thefast radiative transfer for （A）TOVS model）。质量控制分两步进行：粗检验和离群值检验,目的是剔除受地表发射率或云影响的离群资料。结果表明：质量控制后观测增量标准差显著减小,偏差接近无偏正态分布,FY-3卫星微波温度探测器辐射率数据的质量得到很大的改善,为FY-3微波温度计观测亮温资料在数值预报资料同化系统中的应用奠定基础。 相似文献
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云中液态水分布对全球气候和局地天气变化有重要影响, 是判别人工影响天气作业潜力区的重要依据。利用TRMM卫星微波成像仪 (TMI) 85.5 GHz通道垂直极化亮温资料与NCEP再分析资料, 结合VDISORT模式采用逐步逼近方法反演了河南地区地表比辐射率; 再利用TRMM/TMI 85.5 GHz通道垂直极化亮温资料、TRMM/VIRS红外辐射资料及NCEP再分析资料, 结合VDISORT模式采用迭代的方法反演了河南地区云中液态水的垂直积分总含量。与红外卫星云图、TRMM卫星2A12产品及NCEP资料对比分析表明:该研究提出的反演陆地上空非降水云中液态水方法是可行的, 且对云中液态水垂直积分总含量水平分布的反演结果较对比产品结果更好。 相似文献
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地表比辐射率计算的不确定性,直接影响到卫星资料在数值预报中同化应用的效果。本文采用美国NOAA/NESDIS的Weng等[1,2]提出的复杂陆面比辐射率模式,同时用NOAA卫星AMSU-ACh1或Ch2反演的地表比辐射率来调整该模式所需的地表参数,从而在缺少详细地表参数的情况下,改进AMSU-A Ch3和Ch15的地表比辐射率计算精度。在积雪地表情况下,用NOAA卫星AMSU-A资料直接反演各通道的比辐射率,在GRAPES同化系统中的应用表明,结果有明显的改进。 相似文献
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应用先进微波探测器AMSU资料遥感反演春季陆地表层湿度 总被引：2，自引：0，他引：2
利用先进微波探测器(AMSU)正演快速微波辐射传输模型,完成了AMSU 窗区通道亮温与地表温湿特征的相关性分析,根据模拟计算结果改进了现有业务上反演地表微波辐射率的统计分析方法,得到适用于我国非冻土积雪覆盖地区地表微波辐射率反演的指数分析模型;进一步通过地表微波辐射传输模型迭代反演得到土壤体积含水量信息.2001年相互匹配的AMSU资料和地面农业气象观测站地表相对湿度观测结果的对比分析表明二者间具有一定的相关性.利用2002年3月和2003年3月的AMSU资料,反演了我国陆地区域地表湿度;连续两年春季地表湿度反演结果的对比分析表明,与2002年春季相比,2003年我国北方沙尘暴发生源区地表湿度反演值普遍偏高,潮湿的下垫面特征与沙尘暴发生频次的减少之间有一定的对应关系.试验结果表明,利用AMSU遥感资料可以获取大范围陆地表层湿度信息,进行区域尺度陆地表层湿度特征的动态分析,为我国沙尘暴监测分析提供陆地表层湿度基础信息. 相似文献
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利用微波地表发射率模型,模拟计算了沙漠地区石英、砂岩、花岗岩和石灰石不同粒子尺度、砂土含量和土壤含水量时的地表发射率频谱,并用先进微波扫描辐射计-地球观测系统AMSR-E资料对塔克拉玛干沙漠地区进行了地表发射率卫星反演和模型模拟计算的对比研究,分析了该地区不同地表类型和矿物成分的微波地表发射率特征.结果表明,微波地表发射率和地表类型密切相关,并且随着土壤含水量、土壤质地、矿物成分和土壤粒子尺度的不同存在显著变化,成为现有微波地表发射率模型用于沙漠地区模拟计算结果的误差主要来源.根据沙漠地区准确的土壤类型、土壤组分比例、粒径尺度和矿物颗粒等信息对近地表土壤进行了辐射传输过程的分层分析,为改进现有微波地表发射率计算模型提供理论依据. 相似文献
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机载微波大气温度探测仪可以机动灵活地获取大气温度廓线信息。针对一次机载微波大气温度探测仪的多高度飞行观测试验,基于逐线积分模式和大气参数廓线库,建立用于不同飞行高度的快速辐射传输模式,分析了仪器观测亮温的质量并对仪器观测进行了订正;建立了基于神经网络的微波大气温度廓线反演算式,分析了不同高度、不同通道选择对于大气温度廓线反演性能的影响。研究结果表明:（1）较低飞行高度计算得到的各地表敏感通道地表比辐射率之间具有较好的一致性;（2）采用订正算式订正后,不同飞行高度的模拟亮温与观测亮温具有较好的一致性;（3）机载微波大气温度反演最优通道组合依赖于平台飞行高度;（4）采用最优的通道组合,4 200 m、3 200 m和2 500 m高度层温度反演均方根误差范围分别为0.5~1.8 K、0.5~1.3 K和0.4~1.0 K。 相似文献
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Passive microwave signatures of landscapes in winter 总被引：4，自引：0，他引：4
C. Mätzler 《Meteorology and Atmospheric Physics》1994,54(1-4):241-260
Summary The successful application of passive microwave sensors requires signatures for the unambiguous inversion of the remote sensing data. Due to the large number of object types and large variability of physical properties, the inversion of data from land surfaces is a delicate and often ambiguous task. The present paper is a contribution to the assessment of multi-frequency passive microwave signatures of typical objects on land in winter. We discuss the behaviour of measured emissivities at vertical and horizontal polarization over the frequency range of 5 to 100 GHz (incidence angle of 50 degrees) of water and bare soil surfaces, grass and snowcovers under various conditions. These data and their variabilities lead us toward a classificaion algorithm for some, but not all object classes. Most snowcovers can easily be discriminated from other surfaces, difficulties occur for fresh powder snow if 94 GHz data are not available. The problem of wet snow has found a solution by using a certain combination of observables.In addition to snowcover types we find large differences between frozen and unfrozen bare soil. On the other hand the different situations of grasscovers show all very similar emissivities.For the estimation of physical parameters we propose algorithms for certain object classes. The estimation of surface temperature, especially for snow-free land, seems to be feasible, also the estimation of the snow liquid water content at the surface. For estimating soil moisture lower frequencies (e.g. 1.4 GHz) should be used.For the estimation of the Water Equivalent, WE, we cannot yet find a definitive solution. Certain correlations exist for dry winter snow between WE and observables at frequencies between 10 and 35 GHz. Especially the polarization difference at 10 GHz shows a monotonous increase with increasing WE. Algorithms using higher frequencies are more sensitive to WE, however, they are subject to ambiguities.With 7 Figures 相似文献
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Xu Hui Zhang Weiping Lang Xuxing Guo Xia Ge Wenzhong Dang Renqing Takao Takeda 《大气科学进展》2000,17(3):403-412
During the Meiyu period in June and July of 1998, intensified field observations have been carried out for the project “Huaihe
River Basin Energy and Water Cycle Experiment (HUBEX)”. For studying Meiyu front and its precipitation in Huaihe River basin,
the present paper has performed analysis on the middle and lower level wind fields in the troposphere by using the radar data
obtained from the two Doppler radars located at Fengtai district and Shouxian County.
From June 29 to July 3 in 1998, the continuous heavy precipitation occurred in Huaihe River basin around Meiyu front. The
precipitation process on July 2 occurred within the observation range of the two Doppler radar in Fengtai district and Shouxian
County. The maximum rainfall of the Meiyu front was over 100 mm in 24 h, so it can be regarded as a typical mesoscale heavy
precipitation process related to Meiyu front.
Based on the wind field retrieved from the dual Doppler radar, we find that there are meso-γ scale vertical circulations in
the vertical cross-section perpendicular to Meiyu front, the strong upward motion of which corresponds to the position of
the heavy rainfall area. Furthermore, other results obtained by this study are identical with the results by analyzing the
conventional synoptic data years ago. For example: in the vicinity of 3 km level height ahead of Meiyu front there exists
a southwest low-level jet; the rainstorm caused by Meiyu front mainly occurs at the left side of the southwest low-level jet;
and the Meiyu front causes the intensification of the low-level convergence in front of it.
This research was supported by Project HUBEX (Project Number: 49794030) which is funded by the National Natural Science Foundation
of China (NSFC). 相似文献
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用TRMM/TMI估算HUBEX试验区的云中液态水 总被引：4，自引：3，他引：4
文中应用热带降雨测量卫星微波成像仪的微波遥感资料反演云中液态水。由于微波成像仪85.5 GHz通道对云中液态水非常敏感,通过离散纵坐标矢量辐射传输模式,运用迭代的方法可以有效地反演出陆地上空非降水云中的液态水路径。在淮河流域能量与水分循环试验中,分别运用微波成像仪85.5 GHz垂直极化单通道和微波成像仪85.5 GHz极化亮温差两种方法来估算陆地上空的云中液态水路径,反演结果与地基微波辐射计的测量结果是较为一致的。当地表比辐射率或地表温度误差较大时,用极化亮温差法估算云中液态水路径相对较好,尤其是对于低云,因为该方法对地表温度不敏感。 相似文献
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The ability of the Tropical Rainfall Measuring Mission Microwave Imager(TRMM/TMI)forcloud liquid water(CLW)retrieval has been demonstrated in this study.Due to the greatsensitivity of the TMI 85.5 GHz channels to CLW,the liquid water path(LWP)ofnonprecipitating clouds over land can be successfully estimated using the VDISORT model basedon the iteration steps.Both the vertical-polarized 85. 5 GHz single-channel method and thepolarization-difference of 85.5 GHz method were applied to the LWP estimates over land regionsduring the Huaihe River Basin Energy and Water Cycle Experiment(HUBEX)in China.Theretrieval results show reasonable agreement with the ground-based microwave radiometermeasurements.When the surface emissivity or skin temperature is difficult to be made sure,thepolarization-difference method shows advantages of providing estimates of LWP especially for lowclouds because of its extremely insensitiveness to the surface skin temperature. 相似文献
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The model developed in Verseghy and Munro (1989) is extended to the calculation of the longwave radiation incident on building surfaces. When compared with field measurements, the average magnitude of error associated with model predictions is found to be 10 W m–2. The effects of six simplifying assumptions are investigated. The neglect of horizon obstructions is found to lead to errors of up to 60 W m–2; the assumption of wall temperatures equal to air temperatures results in errors of up to 35 W m–2. The neglect of absorption and emission by air between pairs of walls causes errors of the same magnitude as those associated with the predictions of the rigorous model itself. Of the three remaining simplifying assumptions tested (the assumption of isotrophic sky radiation, the use of published values of emissivities instead of measured values, and the blackbody surface assumption), none results om errors >5 W m–2. As in the shortware case, the errors are site-specific, but nevertheless indicate the care with which the use of simplifying assumptions must be approached. 相似文献
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Using synthetic geometrical clouds and radiative microwave model, we examine the possibility to correct the estimations of liquid water path (LWP) or rain rate with cloud cover measurement. This information may be gotten by co-localized measurements of microwave and infrared/visible measurements on new satellites (TRMM, ADEOS 2, …). In a first step, the effects of fractional cloud cover on microwave brightness temperatures (TB) are investigated in three typical cases of nonprecipitating and precipitating (stratiform and convective) clouds. The beam-filling error (BFE) on brightness temperatures may be analyzed with the known spatial variability using 1D or 3D radiative transfer model. Relationships between BFE and subpixel cloud fraction (CF) are discussed according to the cloud type. We tested several parameters that characterize the horizontal cloud inhomogeneity within a radiometer field of view. BFE was found very sensitive to cloud type and inhomogeneity and is maximum for raining cloud with open spatial structure. In order to account for the uncertainty introduced by the spatial distribution, dependence of BFE on textural-based parameters is also discussed using homogeneity, entropy and an indicator of CF horizontal gradient. 相似文献
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One-dimensional synthetic aperture microwave radiometers have higher spatial resolution and record measurements at multiple incidence angles. In this paper, we propose a multiple linear regression method to retrieve sea surface wind speed at an incidence angle between 0° ~65°. We assume that a one-dimensional synthetic aperture microwave radiometer operates at frequencies of 6.9, 10.65, 18.7, 23.8 and 36.5 GHz. Then, the microwave radiative transfer forward model is used to simulate the measured brightness temperatures. The sensitivity of the brightness temperatures at 0°~65° to the sea surface wind speed is calculated. Then, vertical polarization channels(VR), horizontal polarization channels(HR) and all channels(AR) are used to retrieve the sea surface wind speed via a multiple linear regression algorithm at 0° ~65°, and the relationship between the retrieval error and incidence angle is obtained. The results are as follows:(1) The sensitivity of the vertical polarization brightness temperature to the sea surface wind speed is smaller than that of the horizontal polarization.(2) The retrieval error increases with Gaussian noise. The retrieval error of VR first increases and then decreases with increasing incidence angle, the retrieval error of HR gradually decreases with increasing incidence angle, and the retrieval error of AR first decreases and then increases with increasing incidence angle.(3) The retrieval error of AR is the lowest and it is necessary to retrieve the sea surface wind speed at a larger incidence angle for AR. 相似文献
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Existing satellite microwave algorithms for retrieving Sea Surface Temperature(Sst)and wind(SSW)are applicable primarily for non-raining cloudy conditions.With the launch of the Earth Observing System (EOS)Aqua satellite in 2002,the Advanced Microwave Scanning Radiometer(AMSR-E)onboard provides some unique measurements at lower frequencies which are sensitive to ocean surface parameters under ad-verse weather conditions.In this study,a new algorithm is developed to derive SST and SSW for hurricane predictions such as hurricane vortex analysis from the AMSR-E measurements at 6.925 and 10.65 GHz.In the algorithm,the effects of precipitation emission and scattering on the measurements are properly taken into account.The algorithm performances are evaluated with buoy measurements and aircraft dropsonde data.It is found that the root mean square (RMS) errors for SST and SSW are about 1.8K and 1.9m s(-1),respectively,when the results are compared with the buoy data over open oceans under precipitating clouds (e.g.,its liquid water path is larger than 0.5 mm),while they are 1.1 K for SST and 2.0 ms(-1)for SSW,respectively,when the retrievals are validated against the dropsonde measurements over warm oceans.These results indicate that our newly developed algorithm catl provide some critical surface information for trop-ical cycle predictions.Currently,this newly developed algorithm has been implemented into the hybrid variational scheme for the hurricane vortex analysis to provide predictions of SST and SSW fields. 相似文献