Thermal Remote Sensing in Land Surface Processes - Chapter 7

Lập bản đồ các luồng năng lượng bề mặt với nhiệt độ bức xạ Hướng nhiệt độ bề mặt bức xạ, TR (φ), từ một góc φ đỉnh xem có được sử dụng để ước tính nhiệt độ bề mặt hợp lý thông lượng với mức độ thành công (Kustas và Norman 1996) khác nhau. Việc sử dụng TR (φ) thường xuyên liên quan đến các giả định gây tranh cãi rằng nó là tương đương với nhiệt độ khí động học ", cái gọi là T0, của bề mặt. . | Chapter 7 Mapping surface energy fluxes with radiometric temperature William P. Kustas John M. Norman Thomas J. Schmugge and Martha C. Anderson Introduction Directional radiometric surface temperature Tr Ộ from a zenith view angle Ộ has been used to estimate surface sensible heat flux with varying degrees of success Kustas and Norman 1996 . The use of Tr Ộ frequently involves the controversial assumption that it is equivalent to the so-called aerodynamic temperature To of the surface. To is the temperature that satisfies the bulk transport expression having the form To - Ta r To - Ta H . p C r where H is the sensible heat flux W m-2 pCp is the volumetric heat capacity of air Jm-3K-1 Ta is the air temperature at some reference height above the surface K Rex is an excess resistance associated with heat transport and Ra is the aerodynamic resistance s m-1 which has the following form in the surface layer Brutsaert 1982 ln zU - do zOM - Tm ln ZT - do zOM - h Ra --------------------------------------------------- k2 u In this equation dO is the displacement height u is the wind speed measured at height ZU k is von Karman s constant ZT is the height of the Ta measurement Tm and Th are the Monin-Obukhov stability functions for momentum and heat respectively ZOM is the roughness length for momentum transport. The excess resistance is often related to a roughness length for heat so that Rex ln ZOM ZOH ku where ZOH is the roughness length for heat transport and u is the friction velocity u uk ln zU - dO ZOM - Tm . To cannot be measured so it is often replaced with an observation of Tr 0 in equation . However for sparse canopies differences between To and Tr can be 10 . This has forced many users of this bulk transport or single-source approach to adjust ZOH or the ratio ln zOM zoh kB-1 ku REx Garratt and Hicks 1973 206 Kustas et al. to obtain good agreement with measured H. Most approaches have been empirical . Kustas et al. 1989 Stewart et al. .