FY-3A陆表温度反演及高温天气过程动态监测

采用FY-3A/VIRR数据,利用Becker局地分裂窗改进算法反演得到逐日陆表温度 (LST), 对2009年一次高温天气过程进行动态监测, 并分析不同下垫面的热环境变化。结果显示:此过程中可见光红外扫描辐射计 (VIRR) 陆表温度产品在敦煌辐射校正场地两次验证的误差为-0.17 K和1.77 K,与同时间过境的MODIS产品均方根误差为2.64 K,直方图对比陆表温度的频数分布基本一致;对高温天气过程监测发现,此次出现以华北的石家庄、郑州、北京等地和西北地区东部的西安等地为中心的两个陆表温度高值区, 部分地区达到了320.2 K以上;城市剖面资料证实城市热岛现象存在,并发现工矿用地的热岛效应不容忽视,主要是大面积的工矿用地周围植被破坏严重,地表增温更为显著。     

Modeling land surface phenology in a mixed temperate forest using MODIS measurements of leaf area index and land surface temperature

The development of satellite-derived vegetation indices and metrics has enabled researchers to monitor land surface phenology (LSP). While the use of satellite data to monitor LSP is prevalent, there has been minimal effort to model LSP in temperate climates using satellite observations of the land surface. Satellite-derived LSP models are beneficial for studying past and future changes in phenology and related ecosystem processes (e.g., water, energy, and carbon fluxes). The purpose of this study was to model LSP during the spring in a mixed temperate forest using satellite-derived measurements of leaf area index (LAI) and land surface temperature (LST). As part of the model validation process, the use of LST as a proxy for air temperature to model LSP was also investigated. The results indicate that LST derived from the MODIS Terra sensor at 10:30?a.m. (local solar time) can be used to develop a LSP model that predicts the full profile of LAI from winter dormancy to maturity and the date when LAI reaches half of the annual maximum (LAI_50%) with relatively low error. In addition, the modeled LAI values closely tracked in situ observations of the phenological development of the dominant deciduous tree species located in the study area where the model was developed. A comparison of LST and daily maximum air temperature at two levels above the ground surface revealed distinct differences and nonlinearities in the relationship between these two variables. However, accumulated growing degree-days calculated from each of these variables were similar because the largest differences between LST and daily maximum air temperature occurred prior to the beginning of heat accumulation. Consequently, the model predictions of LAI_50% derived from the use of LST and daily maximum air temperature were similar. When the developed model was applied in two other mixed forests, the errors were larger due to substantial interannual variability in the relationship between LAI and heat accumulation and systematic differences in this relationship between sites. Although the model cannot be successfully applied in these other mixed forests, the ability of the model to capture a consistent relationship between satellite estimates of LAI and LST in the study area where it was developed demonstrates that satellite observations of the land surface can be used in certain locations to create LSP phenology models. When validated, the models can be used to examine past and future changes in phenology and related ecosystem processes.     

Trends of urban surface temperature and heat island characteristics in the Mediterranean

Urban air temperature studies usually focus on the urban canopy heat island phenomenon, whereby the city center experiences higher near surface air temperatures compared to its surrounding non-urban areas. The Land Surface Temperature (LST) is used instead of urban air temperature to identify the Surface Urban Heat Island (SUHI). In this study, the nighttime LST and SUHI characteristics and trends in the seventeen largest Mediterranean cities were investigated, by analyzing satellite observations for the period 2001–2012. SUHI averages and trends were based on an innovative approach of comparing urban pixels to randomly selected non-urban pixels, which carries the potential to better standardize satellite-derived SUHI estimations. A positive trend for both LST and SUHI for the majority of the examined cities was documented. Furthermore, a 0.1 °C decade^?1 increase in urban LST corresponded to an increase in SUHI by about 0.04 °C decade^?1. A longitudinal differentiation was found in the urban LST trends, with higher positive values appearing in the eastern Mediterranean. Examination of urban infrastructure and development factors during the same period revealed correlations with SUHI trends, which can be used to explain differences among cities. However, the majority of the cities examined show considerably increased trends in terms of the enhancement of SUHI. These findings are considered important so as to promote sustainable urbanization, as well as to support the development of heat island adaptation and mitigation plans in the Mediterranean.     

利用ASTER数据分析南京城市地表温度分布

城市环境日益受到人们重视, 南京是长江下游人口密集的城市, 研究南京市地表温度分布对了解南京城市气候, 改善生活环境, 为城市发展规划提供有效的气象服务具有一定科学意义。该文利用2002年8月21日10:30 (北京时) ASTER热红外数据, 在ENVI软件的支持下, 通过劈窗算法反演南京城市地表温度, 进一步生成城市地表温度分布等温线图。用同时相ETM+数据进行验证, 二者十分吻合, 说明ASTER反演结果可靠。结果表明:南京市存在明显的热岛效应, 城市地表温度分布差异大; 不同下垫面的地表温度差异明显, 城区地表温度总体高于郊区, 植被覆盖密集区地表温度低于植被稀疏地, 具有较大水域面积和较密植被的城中各大公园形成多个冷岛, 长江水体温度最低; 随着城市的扩大, 新城区热岛效应更加明显。水体和密集植被能显著改善城市环境。     

Mitigating the surface urban heat island: Mechanism study and sensitivity analysis

In a surface urban heat island (SUHI), the urban land surface temperature (LST) is usually higher than the temperature of the surrounding rural areas due to human activities and surface characteristics. Because a SUHI has many adverse impacts on urban environment and human health, SUHI mitigation strategies are very important. This paper investigates the mechanism of a SUHI based on the basic physical laws that control the formation of a SUHI; five mitigation strategies are proposed, namely: sprinkling and watering; paving a pervious surface; reducing the anthropogenic heat (AH) release; using a “white roof”; increasing the fractional vegetation cover or leaf area index (LAI). To quantify the effect of these mitigation strategies, 26 sets of experiments are designed and implemented by running the integrated urban land model (IUM). The results of the sensitivity analysis indicate that sprinkling and watering is an effective measure for mitigating a SUHI for an entire day. Decreasing the AH release is also useful for both night- and daytime SUHI mitigation; however, the cooling extent is proportional to the diurnal cycle of AH. Increasing the albedo can reduce the LST in the daytime, especially when the solar radiation is significant; the cooling extent is approximately proportional to the diurnal cycle of the net radiation. Increasing the pervious surface percentage can mitigate the SUHI especially in the daytime. Increasing the fractional vegetation cover can mitigate the SUHI in the daytime but may aggravate the SUHI at night.     

对NOAA／AVHRR通道反照率和植被指数的大气影响订正试验

在利用大气窗区进行遥感时,大气成分对辐射的吸收和散射作用造成辐射消弱,从而影响气象卫星（AVHRR）两个通道（可见光和近红外）反演地表反照率值及其差和比的植被指数值。在选取实测卫星资料对其作预处理并考虑仪器定标衰减作用后,利用LOWTRAN－7大气辐射传输模式对卫星资料进行大气订正的探讨,指出气溶胶、水汽等大气参数是订正计算中的敏感因子。       

NOAA卫星沙尘暴光谱特征分析及信息提取研究

通过对2000—2002年多次沙尘暴过程NOAA卫星AVHRR资料的分析,研究了沙尘、云、沙漠、戈壁、积雪、裸地、植被等不同目标物的光谱特性,发现沙尘暴在AVHRR-2中各通道均有不同程度的反映。1,2通道中沙尘的反射率较高(介于云和沙漠之间);4,5通道的亮温低于晴空地表高于云;在3通道中沙尘表现的很独特,其亮度温度为所有研究目标物中最高的,表明通道3包含较多的沙尘信息,AVHRR-3取代AVHRR-2后对监测沙尘有不利影响。在此基础上提出定量提取沙尘信息的两种沙尘判识指数,并利用沙尘判识指数成功地提取多次沙尘暴过程的沙尘信息。结果表明：利用多通道组合沙尘判识指数能够对沙尘信息进行有效提取。     

LST在农业气候热量区划中的应用方法研究

根据广西的自然地理特点和现有卫星遥感资料，对国内外10多种反演LST(1and surfacete mperature，陆面温度)的分裂窗算法及其相关的参数估算方法进行了适用性分析。在此基础上找出了适用于计算广西白天LST的算法，并应用该算法计算了晴空条件下的LST，获得了逐日各个时次的LST实况分布。通过模板分析，找到了求算多年LST气候平均图的途径。针对云剔除问题，通过对公共晴空区的统计分析，建立了不同图像间的数值补偿关系，从而有效地消除了云的影响，最终处理生成了广西多年和不同季节的平均LST空间分布图像。分析结果表明：在10km以上的宏观尺度上，广西平均LST的空间分布与平均气温的空间分布规律基本一致，而在1km尺度上，LST的空间特征更为精细、客观，更有利于反映与作物生长关系更为密切的下垫面热量资源的气候分布，是农业气候区划中更为有效的热量区划因子。     

Study on Microwave Remote Sensing of Atmosphere, Cloud and Rain

In this paper, recent research of microwave remote sensing of atmosphere, cloud and rain in China is presented. It includes the following aspects:(1) Progress in the development of multifrequency radiometer and its characteristics and parameters;(2) Application of microwave remote sensing in prediction of atmospheric boundary layer. The atmospheric temperature profiles are derived with 5 mm (54.5 GHz) radiometer angle-scanning observations. Due to the fact that microwave radiometer could monitor the atmospheric temperature profile continuously and make the initialization of numerical model any time, it is helpful for improving the accuracy in prediction of the evolution of atmospheric boundary layer;(3) Theory and application of microwave radiometers in monitoring atmospheric temperature, humidity and water content in cloud. The field experiment of International Satellite Cloud Climatology Project (ISCCP) at Shionomisaki and Amami Oshima of Japan for studies of cloud and weather has been described;(4) Satellite remote sensing of atmosphere and cloud. The TIROS-N TOVS satellite data are used to obtain at-mospheric temperature profile. The results are compared with those of radiosonde, with rms deviation smaller than that of the current operational TOVS processing;(5) Microwave remote sensing and communication. The atmospheric attenuations are derived with microwave remote sensing methods such as solar radiation method etc., in order to obtain the local value instantaneously. The characteristics of Beijing’s rainfall have been analysed and the probability of microwave attenuation of rain is predicted;(6) For improvement of the accuracy of rainfall measurement, a radiometer-radar system (λ= 3.2 cm) has been developed. The variation of rainfull distribution and area-rainfall may be obtained by its measurements, which may be helpful for hydrological prediction.The prospect of microwave remote sensing in meteorology is also discussed.     

我国温度植被旱情指数TVDI的应用现状及问题简述

植被指数和地表温度是2类常见的遥感干旱监测方法,它们分别利用植被受旱时植被指数降低和植被冠层温度升高这2种重要的生理表现来监测干旱。但植被指数对干旱指示具有一定滞后性,地表温度监测干旱时易受土地背景等影响。基于特征空间的温度植被旱情指数(TVDI)综合了植被指数和地表温度监测干旱的特点,物理意义明确,克服部分单独使用植被指数或地表温度的缺点,是目前干旱研究和业务应用中使用最广的遥感干旱指数之一。本文介绍了TVDI的原理、计算方法、应用中的改进及TVDI干旱监测方法,旨在为TVDI的研究及应用提供一些参考。     

The surface urban heat island in the city of Brno (Czech Republic) derived from land surface temperatures and selected reasons for its spatial variability

Thermal infrared images from Landsat satellites are used to derive land surface temperatures (LST) and to calculate the intensity of the surface urban heat island (UHI) during the summer season in and around the city of Brno (Czech Republic). Overall relief, land use structure, and the distribution of built-up areas determine LST and UHI spatial variability in the study area. Land-cover classes, amount and vigor of vegetation, and density of built-up areas are used as explanatory variables. The highest LST values typically occur in industrial and commercial areas, which contribute significantly to surface UHI intensity. The intensity of surface UHI, defined as the difference between mean LST for urban and rural areas, reached 4.2 and 6.7 °C in the two images analyzed. Analysis of two surface characteristics in terms of the amount of vegetation cover, represented by normalized difference vegetation index, demonstrates the predominance of LST variability (56–67 % of explained variance) over the degree of urbanization as represented by density of buildings (37–40 % of LST variance).     

卫星遥感结合数值模式估算金塔绿洲非均匀地表能量通量

针对遥感在面上计算的特点,将模式模拟的气象要素区域分布替代以往使用的单点观测值作为遥感估算蒸散发模型的初始场,引入到SEBS(Surface Energy Balance System)模型中,利用EOS/MODIS遥感资料对金塔绿洲非均匀下垫面地表能量通量进行了估算。对比估算结果与实测值表明,引入数值模拟结果后,绿洲地表感热通量的估算误差平均减小了5.8%,潜热通量的误差平均减小了5.5%,说明数值模拟结果的引入比较成功。通过分析地表通量的区域分布特征表明,数值模拟结果的引入在一定程度上更加细致地刻画了荒漠绿洲能量平衡的分布特征,在戈壁荒漠地区,潜热通量非常小,而绿洲集中的地区及水库附近出现了潜热通量的极大值。     

The impact of climatic and non-climatic factors on land surface temperature in southwestern Romania

Land surface temperature is one of the most important parameters related to global warming. It depends mainly on soil type, discontinuous vegetation cover, or lack of precipitation. The main purpose of this paper is to investigate the relationship between high LST, synoptic conditions and air masses trajectories, vegetation cover, and soil type in one of the driest region in Romania. In order to calculate the land surface temperature and normalized difference vegetation index, five satellite images of LANDSAT missions 5 and 7, covering a period of 26 years (1986–2011), were selected, all of them collected in the month of June. The areas with low vegetation density were derived from normalized difference vegetation index, while soil types have been extracted from Corine Land Cover database. HYSPLIT application was employed to identify the air masses origin based on their backward trajectories for each of the five study cases. Pearson, logarithmic, and quadratic correlations were used to detect the relationships between land surface temperature and observed ground temperatures, as well as between land surface temperature and normalized difference vegetation index. The most important findings are: strong correlation between land surface temperature derived from satellite images and maximum ground temperature recorded in a weather station located in the area, as well as between areas with land surface temperature equal to or higher than 40.0 °C and those with lack of vegetation; the sandy soils are the most prone to high land surface temperature and lack of vegetation, followed by the chernozems and brown soils; extremely severe drought events may occur in the region.     

Mapping of Land-Atmosphere Heat Fluxes and Surface Parameters with Remote Sensing Data

A variational data assimilation scheme is used to infer two key parameters ofthe surface energy balance that control the partitioning of available energy intolatent, sensible, and ground heat fluxes (LE, H, and G). Remotely sensedland surface temperature (LST) is the principal data source. Maps ofdiurnal energy balance components are presented for a basin with varied landcover (Arno Basin, Italy) for a 18-day period in July 1996.Given available energy, the major unknown (dimensionless) parameters requiredfor partitioning among fluxes are: (1) Landscape effects on near-surfaceturbulence as captured by the bulk heat transfer coefficient C_BN underneutral conditions and (2) surface control of the relative magnitudes of LEand H as represented by the evaporative fraction E_F. The data assimilationscheme merges 1.1-km resolution remotely sensed LST images (based onoptical, thermal and microwave measurements from two different satelliteplatforms) into a parsimonious model of heat diffusion. Both the measurementsand the model predictions are considered uncertain. Posterior error statisticsthat represent uncertainty of the estimated parameters are also derived.Maps of C_BN show spatial patterns consistent with the dominant land useand basin physiography. Daily maps of E_F exhibit spatial variationscorresponding to land cover and land use – the day-to-day variations inE_F show fluctuations consistent with rain events and drydowns experiencedduring the period. Based on these parameters and available environmentalvariables, maps of diurnal LE and H may be produced (in this paper daytimeLE maps are reported).The application demonstrates that remotely sensed land surface temperaturesequences contain significant amount of information of the partitioning ofavailable energy among the fluxes. The variational data assimilation frameworkis shown to be an efficient and parsimonious approach without reliance onempirical relationships such as those based on vegetation indices.     

中小城市地表温度空间分异及其与下垫面关系的遥感影像研究

以Landsat TM 影像为主要数据源,采用单窗算法反演河南省南阳市市区的地表温度。在GIS支持下,研究全区地表温度的空间分异特征,并探讨了地表温度与下垫面特征的关系。结果显示：研究区内高温斑块主要集中在仓储区和商业与公共服务区,该类区域过高的LST对城市环境有明显的负面影响;拦蓄河流所营造的水体是面积较大的低温斑块,对改善城市热环境和中小型城市拦蓄河流措施有一定意义;研究区内LST的空间自相关性在不同方向上有明显差别,东-西方向和东北-西南方向上空间自相关的范围较大,这种格局与区内水体走向有关;地表温度与道路密度指数呈明显正相关。提出中小城市可在仓储用地和交通发达地段周边规划绿地和水体,以抑制热岛呈大面积连片分布。     

Development of satellite green vegetation fraction time series for use in mesoscale modeling: application to the European heat wave 2006

A method is presented for development of satellite green vegetation fraction (GVF) time series for use in the Weather Research and Forecasting (WRF) model. The GVF data is in the WRF model used to describe the temporal evolution of many land surface parameters, in addition to the evolution of vegetation. Several high-resolution GVF products, derived from high-quality satellite retrievals from Moderate Resolution Imaging Spectroradiometer images, were produced and their performance was evaluated in long-term WRF simulations. The atmospheric conditions during the 2006 heat wave year over Europe were simulated since significant interannual variability in vegetation seasonality was found. Such interannual variability is expected to increase in the coming decades due to climatic changes. The simulation using a quadratic normalized difference vegetation index to GVF relationship resulted in consistent improvements of modeled temperatures. The model mean temperature cold bias was reduced by 10 % for the whole domain and by 20–45 % in areas affected by the heat wave. The study shows that WRF simulations during heat waves and droughts, when vegetation conditions deviate from the climatology, require concurrent land surface properties in order to produce accurate results.     

应用卫星资料分析苏州夏季城市热岛效应

利用苏州2004-2007年自动气象站资料以及购自中国科学院对地观测与数字地球科学中心的Landsat 5卫星(25 m分辨率)资料,分析研究苏州地区城市热岛总体特点以及分布规律,并对可能变化做一些探讨.分析认为,由于城市热岛效应,苏州地区气温呈中间高两侧低的分布特征,气温高值中心呈西北-东南走向,沿太湖及沿江地区气温相对较低;苏州城市地表温度呈明显的放射型分布,以市区中心向四周呈放射状分布.     

Utility of Radiometric–aerodynamic Temperature Relations for Heat Flux Estimation

In many land-surface models using bulk transfer (one-source) approaches, the application of radiometric surface temperature observations in energy flux computations has given mixed results. This is due in part to the non-unique relationship between the so-called aerodynamic temperature, which relates to the efficiency of heat exchange between the land surface and overlying atmosphere, and a surface temperature measurement from a thermal-infrared radiometer, which largely corresponds to a weighted soil and canopy temperature as a function of radiometer viewing angle. A number of studies over the past several years using multi-source canopy models and/or experimental data have developed simplified methods to accommodate radiometric–aerodynamic temperature differences in one-source approaches. A recent investigation related the variability in the radiometric–aerodynamic relation to solar radiation using experimental data from a variety of landscapes, while another used a multi-source canopy model combined with measurements over a wide range in vegetation density to derive a relationship based on leaf area index. In this study, simulations by a detailed multi-source soil–plant–environment model, Cupid, which considers both radiative and turbulent exchanges across the soil–canopy–air interface, are used to explore the radiometric–aerodynamic temperature relations for a semi-arid shrubland ecosystem under a range of leaf area/canopy cover, soil moisture and meteorological conditions. The simulated radiometric-aerodynamic temperatures indicate that, while solar radiation and leaf area both strongly affect the magnitude of this temperature difference, the relationships are non-unique, having significant variability depending on local conditions. These simulations also show that soil–canopy temperature differences are highly correlated with variations in the radiometric–aerodynamic temperature differences, with the slope being primarily a function of leaf area. This result suggests that two-source schemes with reliable estimates of component soil and canopy temperatures and associated resistances may be better able to accommodate variability in the radiometric–aerodynamic relation for a wider range in vegetated canopy cover conditions than is possible with one-source schemes. However, comparisons of sensible heat flux estimates with Cupid using a simplified two-source model and a one-source model accommodating variability in the radiometric-aerodynamic relation based on vegetation density gave similar scatter. On the other hand, with experimental data from the shrubland site, the two-source model generally outperformed the one-source scheme. Clearly, vegetation density/leaf area has a major effect on the radiometric–aerodynamic temperature relation and must be considered in either one-source or two-source formulations. Hence these adjusted one-source models require similar inputs as in two-source approaches, but provide as output only bulk heat fluxes; this is not as useful for monitoring vegetation conditions.     

Sensitivity of an ecosystem model to hydrology and temperature

We tested the sensitivity of a dynamic ecosystem model (LPJ-GUESS) to the representation of soil moisture and soil temperature and to uncertainties in the prediction of precipitation and air temperature. We linked the ecosystem model with an advanced hydrological model (JULES) and used its soil moisture and soil temperature as input into the ecosystem model. We analysed these sensitivities along a latitudinal gradient in northern Russia. Differences in soil temperature and soil moisture had only little influence on the vegetation carbon fluxes, whereas the soil carbon fluxes were very sensitive to the JULES soil estimations. The sensitivity changed with latitude, showing stronger influence in the more northern grid cell. The sensitivity of modelled responses of both soil carbon fluxes and vegetation carbon fluxes to uncertainties in soil temperature were high, as both soil and vegetation carbon fluxes were strongly impacted. In contrast, uncertainties in the estimation of the amount of precipitation had little influence on the soil or vegetation carbon fluxes. The high sensitivity of soil respiration to soil temperature and moisture suggests that we should strive for a better understanding and representation of soil processes in ecosystem models to improve the reliability of predictions of future ecosystem changes.