Spatial representativeness and the location bias of flux footprints over inhomogeneous areas

被引:120
作者
Schmid, HP [1 ]
Lloyd, CR
机构
[1] Indiana Univ, Dept Geog, Bloomington, IN 47405 USA
[2] Inst Hydrol, Wallingford OX10 8BB, Oxon, England
基金
英国自然环境研究理事会;
关键词
inhomogenous areas; flux observations; footprint; aggregation; representativeness;
D O I
10.1016/S0168-1923(98)00119-1
中图分类号
S3 [农学(农艺学)];
学科分类号
0901 ;
摘要
Turbulent fluxes over natural vegetation are spatially inhomogeneous up to a level called the physical blending height. Measurements below this blending height suffer from a location bias that varies with sensor height, wind direction and stability. The location bias is the degree, to which a flux measured at a given location differs from the aggregated ecosystem-scale Bur. This location bias is analyzed using the source area/footprint approach, where the aggregated surface conditions contained in the footprint are compared to average surface conditions in the ecosystem. When a single observation event at a given location is considered, this method leads to a quantitative measure of the sensor location bias. It provides an objective estimate of how a given flux observation compares to the ecosystem scale flux. The expected sensor location bias is expressed as the fraction of surface variability not accounted for by measurements at a given sensor height, independent of its location within the ecosystem. It results from a convolution of the footprint filter function with a detailed surface condition database. These tools to examine the spatial representativeness of flux measurements are applied to an inhomogeneous savannah surface (Tiger bush) in the Sahel region of Niger, and to measurements of evaporation collected during the HAPEX-Sahel held campaign. Published by Elsevier Science B.V.
引用
收藏
页码:195 / 209
页数:15
相关论文
共 30 条
[1]  
[Anonymous], P 8 S TURB DIFF SAN
[2]   Flux footprints within and over forest canopies [J].
Baldocchi, D .
BOUNDARY-LAYER METEOROLOGY, 1997, 85 (02) :273-292
[3]  
CLAUSSEN M, 1989, BEITR PHYS ATMOS, V62, P236
[4]   ENERGY AND WATER BUDGETS OF AN AREA OF PATTERNED WOODLAND IN THE SAHEL [J].
CULF, AD ;
ALLEN, SJ ;
GASH, JHC ;
LLOYD, CR ;
WALLACE, JS .
AGRICULTURAL AND FOREST METEOROLOGY, 1993, 66 (1-2) :65-80
[5]  
DOLMAN AJ, 1992, ANN GEOPHYS, V10, P930
[6]   Experimental evaluation of analytical and Lagrangian surface-layer flux footprint models [J].
Finn, D ;
Lamb, B ;
Leclerc, MY ;
Horst, TW .
BOUNDARY-LAYER METEOROLOGY, 1996, 80 (03) :283-308
[7]   HAPEX-SAHEL - A LARGE-SCALE STUDY OF LAND-ATMOSPHERE INTERACTIONS IN THE SEMIARID TROPICS [J].
GOUTORBE, JP ;
LEBEL, T ;
TINGA, A ;
BESSEMOULIN, P ;
BROUWER, J ;
DOLMAN, AJ ;
ENGMAN, ET ;
GASH, JHC ;
HOEPFFNER, M ;
KABAT, P ;
KERR, YH ;
MONTENY, B ;
PRINCE, S ;
SAID, F ;
SELLERS, P ;
WALLACE, JS .
ANNALES GEOPHYSICAE-ATMOSPHERES HYDROSPHERES AND SPACE SCIENCES, 1994, 12 (01) :53-64
[8]   APPLIED DISPERSION MODELING BASED ON METEOROLOGICAL SCALING PARAMETERS [J].
GRYNING, SE ;
HOLTSLAG, AAM ;
IRWIN, JS ;
SIVERTSEN, B .
ATMOSPHERIC ENVIRONMENT, 1987, 21 (01) :79-89
[9]   SCALING THE ATMOSPHERIC BOUNDARY-LAYER [J].
HOLTSLAG, AAM ;
NIEUWSTADT, FTM .
BOUNDARY-LAYER METEOROLOGY, 1986, 36 (1-2) :201-209
[10]   FOOTPRINT ESTIMATION FOR SCALAR FLUX MEASUREMENTS IN THE ATMOSPHERIC SURFACE-LAYER [J].
HORST, TW ;
WEIL, JC .
BOUNDARY-LAYER METEOROLOGY, 1992, 59 (03) :279-296