Anomaly Detection in MODIS Land Products via Time Series Analysis

With remote sensing information products becoming increasingly varied and arguably improved, scientific applications of such products rely on their quality assessment. In an operational context such as the NASA (National Aeronautics and Space Administration) information production based on the MODIS (Moderate Resolution Imaging Spectroradiometer) instrument on board Earth Observing System (EOS) Terra and Aqua satellites, efficient ways of detecting product anomaly, i.e., to discriminate between product artifacts and real changes in Earth processes being monitored, are extremely important to assist and inform the user communities about potential unreliability in the products. A technique for anomaly detection, known as MAD (the median of absolute deviate from the median), in MODIS land products via time series analysis is described, which can handle intra- and in-ter-annual variation in the data by using MAD statistics of the original data and their first-order difference. This method is shown to be robust and work across major land products, including NDVI, active fire, snow cover, and surface reflectance, and its applicabil-ity to multi-disciplinary products is anticipated.

利用星载激光雷达资料研究东亚地区云垂直分布的统计特征

已有研究表明:云的垂直结构(简称CVS)是一个在卫星资料反演和气候模式预测中很重要的云特征。本文通过利用美国2006年刚发射的卫星CALIPSO(Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Obser-vations)所负载的激光雷达Level2_05km的云数据,研究了东亚地区(18°N^53°N,74°E^144°E)云的垂直分布特征。结果表明:东亚地区多层云云量在夏季、秋季、冬季、春季分别为43.6%、29.6%、21.1%、33.3%,而多层云分布中双层云比例最大。云顶和云底高度除了随季节变化显著外,还有明显的区域特征。单层云、双层云以及三层云的云顶和云底高度的数据显示,三层云中最上层的云顶和云底最高,并始终高于两层云中最上层云的云顶和云底高度。平均云层厚度季节变化不明显,其值普遍在0.9~2km范围之间。而云层间距同样没有明显的季节和区域变化,其出现的概率随距离的增大而减小。其中,间距在0.35km的概率最大,占到将近50%。而间距在1.45km附近的概率大约为15%,高一点的可达到20%。

Application of an Error Statistics Estimation Method to the PSAS Forecast Error Covariance Model

In atmospheric data assimilation systems, the forecast error covariance model is an important component. However, the paralneters required by a forecast error covariance model are difficult to obtain due to the absence of the truth. This study applies an error statistics estimation method to the Pfiysical-space Statistical Analysis System （PSAS） height-wind forecast error covariance model. This method consists of two components： the first component computes the error statistics by using the National Meteorological Center （NMC） method, which is a lagged-forecast difference approach, within the framework of the PSAS height-wind forecast error covariance model; the second obtains a calibration formula to rescale the error standard deviations provided by the NMC method. The calibration is against the error statistics estimated by using a maximum-likelihood estimation （MLE） with rawindsonde height observed-minus-forecast residuals. A complete set of formulas for estimating the error statistics and for the calibration is applied to a one-month-long dataset generated by a general circulation model of the Global Model and Assimilation Office （GMAO）, NASA. There is a clear constant relationship between the error statistics estimates of the NMC-method and MLE. The final product provides a full set of 6-hour error statistics required by the PSAS height-wind forecast error covariance model over the globe. The features of these error statistics are examined and discussed.

Parametric Study of Calibration Blackbody Uncertainty Using Design of Experiments

NASA is developing the Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission to provide accurate measurements to substantially improve understanding of climate change. CLARREO will include a Reflected Solar (RS) Suite, an Infrared (IR) Suite, and a Global Navigation Satellite System-Radio Occultation (GNSS-RO). The IR Suite consists of a Fourier Transform Spectrometer (FTS) covering 5 to 50 micrometers (2000-200 cm-1 wavenumbers) and on-orbit calibration and verification systems. The IR instrument will use a cavity blackbody view and a deep space view for on-orbit calibration. The calibration blackbody and the verification system blackbody will both have Phase Change Cells (PCCs) to accurately provide a SI reference to absolute temperature. One of the most critical parts of obtaining accurate CLARREO IR scene measurements relies on knowing the spectral radiance output from the blackbody calibration source. The blackbody spectral radiance must be known with a low uncertainty, and the magnitude of the uncertainty itself must be reliably quantified. This study focuses on determining which parameters in the spectral radiance equation of the calibration blackbody are critical to the blackbody accuracy. Fourteen parameters are identified and explored. Design of Experiments (DOE) is applied to systematically set up an experiment (i.e., parameter settings and number of runs) to explore the effects of these 14 parameters. The experiment is done by computer simulation to estimate uncertainty of the calibration blackbody spectral radiance. Within the explored ranges, only 4 out of 14 parameters were discovered to be critical to the total uncertainty in blackbody radiance, and should be designed, manufactured, and/or controlled carefully. The uncertainties obtained by computer simulation are also compared to those obtained using the “Law of Propagation of Uncertainty”. The two methods produce statistically different uncertainties. Nevertheless, the differences are small and are not considered to be important. A follow-up study has been planned to examine the total combined uncertainty of the CLARREO IR Suite, with a total of 47 contributing parameters. The DOE method will help in identifying critical parameters that need to be effectively and efficiently designed to meet the stringent IR measurement accuracy requirements within the limited resources.

Confidence Measure of the Shallow-Water Bathymetry Map Obtained through the Fusion of Lidar and Multiband Image Data

With the advancement of Lidar technology,bottom depth(H)of optically shallow waters(OSW)can be measured accurately with an airborne or space-borne Lidar system(H_(Lidar) hereafter),but this data product consists of a line format,rather than the desired charts or maps,particularly when the Lidar system is on a satellite.Meanwhile,radiometric measurements from multiband imagers can also be used to infer H(H_(imager) hereafter)of OSW with variable accuracy,though a map of bottom depth can be obtained.It is logical and advantageous to use the two data sources from collocated measurements to generate a more accurate bathymetry map of OSW,where usually image-specific empirical algorithms are developed and applied.Here,after an overview of both the empirical and semianalytical algorithms for the estimation of H from multiband imagers,we emphasize that the uncertainty of H_(imager) varies spatially,although it is straightforward to draw regressions between H_(Lidar) and radiometric data for the generation of H_(imager).Further,we present a prototype system to map the confidence of H_(imager) pixel-wise,which has been lacking until today in the practices of passive remote sensing of bathymetry.We advocate the generation of a confidence measure in parallel with H_(imager),which is important and urgent for broad user communities.

Surveys of rodent-borne disease in Thailand with a focus on scrub typhus assessment

The epidemiology of many rodent-borne diseases in South-East Asia remains ill-defined.Scrub typhus and lep-tospirosis are common and medically significant,while other zoonotic diseases,such as spotted fever group Rickettsiae have been identified,but their overall medical significance is unknown.Rodent surveillance was con-ducted from June 2002 to July 2004 in 18 provinces from Thailand.Traps were set up for one to three nights.Blood and serum samples and animal tissue samples(liver,spleen,kidney and urinary bladder)were collected.Chigger-mites,ticks and fleas were removed from captured rodents.Atotal of 4536 wild-caught rodents from 27 species were captured over two years of animal trapping.Rattus rattus was the dominant species,followed by Rattus exulans and Bandicota indica.Almost 43000 ectoparasites were removed from the captured animals.Approximately 98%of the ectoparasites were chigger-mites,of which 46%belonged to the genus Leptotrombidium(scrub typhus vector).Other genera included Schoengastia and Blankaartia.Tick and flea specimens together comprised less than 1%of the sample.Among the five species of ticks collected,Haemaphysalis bandicota was the predominant species caught,followed by Ixodes granulatus other Haemaphysalis spp.,Rhipicephalus spp.and Dermacentor spp.Only two species of fleas were collected and Xenopsylla cheopis(rat flea)was the predominant species.Using both commercial diagnostic kits and in-house molecular assays,animal tissue samples were examined and screened for zoonotic diseases.Seven zoonotic diseases were detected:scrub typhus,leptospirosis,murine typhus,tick typhus,bartonella,babesiosis and trypanosomiasis.Most samples were positive for scrub typhus.Other zoonotic diseases still under investigation include borrelosis,ehrlichiosis,the plague,and other rickettsial diseases.Using geo-graphic information systems,global positioning systems and remote sensing technology,epidemiological and environmental data were combined to assess the relative risk in different biotopes within highly endemic areas of scrub typhus in Thailand.

Development of an operational land water mask for MODIS Collection 6,and influence on downstream data products

Data from the Moderate Resolution Imaging Spectro-radiometer(MODIS)on-board the Earth Observing System Terra and Aqua satellites are processed using a land water mask to determine when an algorithm no longer needs to be run or when an algorithm needs to follow a different pathway.Entering the fourth reprocessing(Collection 6(C6))the MODIS team replaced the 1 km water mask with a 500 m water mask for improved representation of the continental surfaces.The new water mask represents more small water bodies for an overall increase in water surface from 1%to 2%of the continental surface.While this is still a small fraction of the overall global surface area the increase is more dramatic in certain areas such as the Arctic and Boreal regions where there are dramatic increases in water surface area in the new mask.MODIS products generated by the on-going C6 reprocessing using the new land water mask show significant impact in areas with high concentrations of change in the land water mask.Here differences between the Collection 5(C5)and C6 water masks and the impact of these differences on the MOD04 aerosol product and the MOD11 land surface temperature product are shown.

3维场景植被冠层多波段模拟研究进展

植被冠层辐射散射信号中蕴含了丰富的植被信息,通过构建植被冠层辐射散射模型,可以实现植被结构等生物物理参数的遥感定量反演。迄今为止,可见光/近红外、热红外、微波波段均已发展了大量的模型,这些模型在参数反演方面各具优势,但不同波段的模型又有其自身的局限性。跨波段的联合模拟可以实现模型间的优势互补,进而提高地表参数的反演精度,近年来已有学者专注于可见光/近红外与热红外模型,热红外与微波模型,主被动微波模型,以及可见光/近红外与微波模型的联合模拟和协同反演,但多是两两联合,且主要是基于经验模型或解析模型。基于3维场景的植被冠层辐射散射特性模拟模型可以细致刻画不同组分的结构和空间分布特征,对于由植被结构引起的多次散射和组分比例变化的考虑具有优势。本文主要介绍了3维模拟模型在可见光/近红外、热红外和微波波段,以及跨波段联合模拟方面的研究进展,从模型机理、场景统一、以及组分理化参数的统一的角度,探讨了构建多波段3维模拟系统的可行性,展望了多波段3维模拟模型的发展趋势。