基于MODIS数据地表温度反演劈窗算法的比较研究

选取QIN和SOB两种代表性劈窗算法对辽宁地区地表温度进行反演,并分析二者的精度和误差分布。结果表明：QIN和SOB算法反演的地表温度（TS）与地面气象台站准同步观测的气温和地温的线性拟合显著,SOB算法线性拟合更好;从误差分布直方图上看,两种算法的反演结果与地温更接近,SOB算法与同步气温和地温在±2 ℃之间的误差比例略高于QIN算法;在野外开展与卫星遥感空间尺度一致的地表温度观测试验,QIN和SOB算法与实测值的平均绝对误差均为1.5 ℃;与NASA官网发布的地表温度产品对比发现,QIN和SOB算法的平均绝对误差分别为1.75 ℃、1.70 ℃;因此QIN、SOB算法在辽宁地区均适用,SOB算法误差更小。     

Parameterization of snow-free land surface albedo as a function of vegetation phenology based on MODIS data and applied in climate modelling

The aim of this study was to develop an advanced parameterization of the snow-free land surface albedo for climate modelling describing the temporal variation of surface albedo as a function of vegetation phenology on a monthly time scale. To estimate the effect of vegetation phenology on snow-free land surface albedo, remotely sensed data products from the Moderate-Resolution Imaging Spectroradiometer (MODIS) on board the NASA Terra platform measured during 2001 to 2004 are used. The snow-free surface albedo variability is determined by the optical contrast between the vegetation canopy and the underlying soil surface. The MODIS products of the white-sky albedo for total shortwave broad bands and the fraction of absorbed photosynthetically active radiation (FPAR) are analysed to separate the vegetation canopy albedo from the underlying soil albedo. Global maps of pure soil albedo and pure vegetation albedo are derived on a 0.5° regular latitude/longitude grid, re-sampling the high-resolution information from remote sensing-measured pixel level to the model grid scale and filling up gaps from the satellite data. These global maps show that in the northern and mid-latitudes soils are mostly darker than vegetation, whereas in the lower latitudes, especially in semi-deserts, soil albedo is mostly higher than vegetation albedo. The separated soil and vegetation albedo can be applied to compute the annual surface albedo cycle from monthly varying leaf area index. This parameterization is especially designed for the land surface scheme of the regional climate model REMO and the global climate model ECHAM5, but can easily be integrated into the land surface schemes of other regional and global climate models.     

Estimation of the sensible heat flux of a semi-arid area using surface radiative temperature measurements

In the framework of an international field program for the study of semi-arid areas, observations were done in the region called La Crau in southern France. In this paper, the use of the surface radiative temperature for the determination of the sensible heat flux is addressed. We found that, once proper values of the roughness length of momentum (z ₀) and heat (z ₀h) are set, the sensible heat flux can be reliably predicted with a one-layer resistance model using standard observations of wind speed and air temperature, together with the surface temperature. The latter quantity has to be known with a precision better than ±2°C. From our observations, the value of the parameterB ^–1k ^–1 In (z ₀ z ₀h) was found to be 9.2, which falls between values quoted by Brutsaert (1982) for grass and bluff bodies.     

Aerodynamic and canopy resistance of short-rotation forest in relation to leaf area index and climate

The aerodynamic and canopy resistances of a willow short-rotation stand were estimated during the course of a growing season on the basis of micrometeorological measurements. The normalized roughness length (z ₀/h) decreased from about 0.10 at a leaf area index of one to 0.05 at a leaf area index of seven. This implies that the aerodynamic resistance at peak leaf area index is more than twice the value at zero leaf area index, all other variables unchanged. The canopy resistance depended strongly on air water concentration deficit and on leaf area index. The Lohammar equation showed good agreement between estimated and measured canopy resistances over the whole course of leaf development. The stand was well-coupled to the atmosphere only for very small values of leaf area indices, less than one, and it was practically de-coupled for leaf area indices above two. From the point of view of factors controlling evaporation, this type of stand acts as a traditional forest at the beginning and end of the season and as an agricultural crop in the middle of the season.     

Comprehensive study on the influence of evapotranspiration and albedo on surface temperature related to changes in the leaf area index

Many studies have investigated the influence of evapotranspiration and albedo and emphasize their separate effects but ignore their interactive influences by changing vegetation status in large amplitudes. This paper focuses on the comprehensive influence of evapotranspiration and albedo on surface temperature by changing the leaf area index(LAI) between 30–90 N.Two LAI datasets with seasonally different amplitudes of vegetation change between 30–90N were used in the simulations.Seasonal differences between the results of the simulations are compared, and the major findings are as follows.(1) The interactive effects of evapotranspiration and albedo on surface temperature were different over different regions during three seasons [March–April–May(MAM), June–July–August(JJA), and September–October–November(SON)], i.e., they were always the same over the southeastern United States during these three seasons but were opposite over most regions between30–90 N during JJA.(2) Either evapotranspiration or albedo tended to be dominant over different areas and during different seasons. For example, evapotranspiration dominated almost all regions between 30–90N during JJA, whereas albedo played a dominant role over northwestern Eurasia during MAM and over central Eurasia during SON.(3) The response of evapotranspiration and albedo to an increase in LAI with different ranges showed different paces and signals. With relatively small amplitudes of increased LAI, the rate of the relative increase in evapotranspiration was quick, and positive changes happened in albedo. But both relative changes in evapotranspiration and albedo tended to be gentle, and the ratio of negative changes of albedo increased with relatively large increased amplitudes of LAI.     

Soil temperature response in Korea to a changing climate using a land surface model

The land surface processes play an important role in weather and climate systems through its regulation of radiation, heat, water and momentum fluxes. Soil temperature (ST) is one of the most important parameters in the land surface processes; however, there are few extensive measurements of ST with a long time series in the world. According to the CLImatology of Parameters at the Surface (CLIPS) methodology, the output of a trusted Soil-Vegetation- Atmosphere Transfer (SVAT) scheme can be utilized instead of observations to investigate the regional climate of interest. In this study, ST in South Korea is estimated in a view of future climate using the output from a trusted SVAT scheme — the University of TOrino model of land Process Interaction with Atmosphere (UTOPIA), which is driven by a regional climate model. Here characteristic changes in ST are analyzed under the IPCC A2 future climate for 2046-2055 and 2091-2100, and are compared with those under the reference climate for 1996-2005. The UTOPIA results were validated using the observed ST in the reference climate, and the model proved to produce reasonable ST in South Korea. The UTOPIA simulations indicate that ST increases due to environmental change, especially in air temperature (AT), in the future climate. The increment of ST is proportional to that of AT except for winter. In wintertime, the ST variations are different from region to region mainly due to variations in snow cover, which keeps ST from significant changes by the climate change.     

Observed variations of leaf area index and its relationship with surface temperatures during warm seasons

Summary The leaf area index (LAI) is one of the most critical variables describing the biophysical and biochemical properties of the land cover in the remote sensing and climate models. In this study, the climatological variations of LAI is analyzed with NOAA’s 14-year (1981–1994) Advanced Very High Resolution Radiometer (AVHRR) measurements. More attention is given to the 14 months of Julys or the warm seasons, in which interannual LAI variations contain more pronounced signals of dynamic forcing associated with the tropical rainforests and the temperate forests around 60° N. Furthermore, projecting the LAI anomalies into the empirical orthogonal function time series of El Ni?o and other climatologically important events shows that the large-scale circulations play an important role in determining the interannual variations of LAI, likely through the changes of surface insolation, precipitation and soil moisture. It is found that on the global scale LAI and the land surface and skin temperatures are negatively correlated, namely, decreasing LAI corresponds to warm temperatures. However, the regional LAI effects on the land surface climate vary significantly from regions to regions. Received October 13, 2001 Revised December 28, 2001     

Aerosol optical thickness retrieval over non-Lambertian land surface with synergistic use of AATSR radiance measurements and MODIS derived Albedo Model Parameters

Various algorithms have recently been developed in order to retrieve the aerosol optical thickness (AOT) at continental scales. However, they are, to some extent, subject to large uncertainties resulting from some necessary physical assumptions on land surface anisotropy and level of brightness. In fact, disentangling aerosol and surface signals contained in the top of atmosphere (TOA) radiance received at the satellite level are a matter of difficulty because a single sensor itself cannot gather all required spatial, temporal, spectral and angular information. In particular, each instrument yields limited scanning configuration due to its platform's orbital characteristics. In this regard, a synergetic approach is presented which merges Advanced Along-Track Scanning Radiometer (AATSR) TOA radiances and the MODerate resolution Imaging Spectroradiometer (MODIS) Bi-directional Reflectance Distribution Function (BRDF)/Albedo Model Parameters Product for the retrieval of AOT at 0.55, 0.66, and 0.87 µm wavelengths over non-Lambertian land surface at a 5 km spatial resolution. In this approach, BRDF products serve to assess the surface reflectance in the AATSR geometry as a boundary layer. The peculiarity of the approach is that no specific assumption is required about the spectral characteristics of land surface, thus allowing for a quantitative retrieval of aerosol particles over any arbitrary land unit in virtue of combining forward and nadir AATSR observations. We obtain on average differences within 0.1τ compared to in situ AErosol RObotic NETwork (AERONET) measurements and 36 retrievals corresponding to 27 January, 12 February, 16 March, 28 May, 26 June, and 21 July 2006, respectively, over the city of Beijing in China. Pearson's correlation coefficient is 0.94 and 0.96 for nadir and forward AATSR, respectively. These suggest that AOT retrieval over land is indeed feasible by taking benefit of the validated MODIS BRDF. Besides, the first results indicate that the AATSR retrievals might be used to evaluate the spectral behaviour of the AOT.     

气象卫星遥感地表温度推算近地表气温方法研究

气温是各种植物生理、水文、气象、环境等模式或模型中的一个非常重要的近地表气象参数.多年来气温数据以离散的常规气象站点观测为主,连续分布的格点气温数据则以站点资料插值而得到,分辨率低,无法反映地形等下垫面因素对局地气温的影响,在农业气候区划等研究中具有一定的局限性.随着卫星遥感地表温度算法的日趋成熟,为探讨卫星遥感地表温度数据在气温观测中的可能性和可行性,利用全中国2340个站点1998 2007年的逐旬平均最高气温数据,以及相应时段的NOAA/AVHRR旬最高地表温度数据,以线性回归及拟合模型为主,通过考虑植被指数、土地覆盖类型、季节、风速、气压、降水等各类影响因子,建立了旬最高地表温度与旬平均最高气温间的推算模型,并利用未参与建模的2002-2003年的常规气象站点气温数据,同时与推算气温和插值气温结果进行对比分析.结果表明,利用卫星遥感地表温度数据推算的旬值气温数据可取得较高的精度,尤其在地形复杂地区以及站点稀疏地区精度明显高于插值气温结果.     

Impact of enhanced forest conditions on land surface characteristics over central India using LIS

Theoretical and Applied Climatology - Both runoff and rainfall do not happen at the same time and there is a certain lag in time. The length of lag time and lagged intensity are greatly affected by...     

Estimating surface sensible heat flux using sodar and surface temperature measurements in the evolving convective boundary layer

A simple method is described for estimating the sensible heat flux by using a Doppler sodar system and a thermal probe. This method, which can be applied to a convective boundary layer in morning hours, is based on knowing the zero heat flux level from the reflectivity and the vertical wind speed.     

基于MODIS数据的陕西地表温度监测

地表温度是反映土壤—植被—大气系统能量流动与物质交换的重要参数,讨论了利用EO S/M OD IS资料反演地表温度的分裂窗方法各参数获取及其在陕西省的应用;建立了基于M OD IS遥感资料和地面自动气象站观测资料反演地表温度的统计模型。监测试验结果表明:利用分裂窗方法反演陕西地表温度,其中参数设定仍需要做大量工作;统计方法考虑季节差异,在地表状况不太复杂时也能取得较好的监测效果。     

Evaluating the impacts of land use and land cover changes on surface air temperature using the WRF-mosaic approach

如何量化土地利用/覆盖变化(LUCC)对区域气候的影响,是人类活动影响气候变化研究中的一个难点。本文利用卫星遥感反映过去三十年东亚区域土地利用变化数据,基于Mosaic近似考虑土地利用及其变化次网格尺度过程,量化了LUCC对地表辐射收支及气温的影响。过去三十年土地利用/覆盖变化对东亚区域总体呈降温效应(中国东部地区增温效应),LUCC导致的地表反照率变化影响地表辐射收支,中国和东亚区域的辐射强迫分别为-0.56 W m~(-2)和-0.50 W m~(-2)。     

Precipitation as a control of vegetation phenology for temperate steppes in China

已有的物候研究主要针对温度的影响,而降水量的物候效应研究相对较少。文中用NDVI比率法分析内蒙古草原两个同温样带的年降水量与草原物候之间的关系。结果表明,在中国温带草原区,年降雨量增加能显著促进春季植物的萌芽和夏季最高生物量日期的到来,而年平均温度起抑制的作用。在低纬度的同温样带(内蒙古中部草原),年降水量增加能延迟生长期结束日期,而在高纬度地区(呼伦贝尔草原)年降水量增加会轻微提前结束生长期。因此在内蒙古中部草原年降水量增加能明显延长草原植被的生长期。