Four-stream isosector approximation for canopy radiative transfer

被引:11
作者
Tian, Yuhong [1 ]
Dickinson, Robert E. [1 ]
Zhou, Liming [1 ]
机构
[1] Georgia Inst Technol, Sch Earth & Atmospher Sci, Atlanta, GA USA
关键词
D O I
10.1029/2006JD007545
中图分类号
P4 [大气科学(气象学)];
学科分类号
0706 ; 070601 ;
摘要
This study develops an analytical four-stream isosector approximation for solar radiative transfer in a homogeneous canopy, based on the approximation of four spherical sectors of isotropic intensities (constant values for light intensities). Compared to results from a multilayer radiative transfer model, the four-stream isosector approximation substantially improves the accuracy in calculation of albedo, transmittance, and absorptance with respect to the corresponding two-stream approximation. For direct incident radiation, it has errors mostly under 5% for leaf area index less than 5, even when sun angles are very low, while the two-stream method has errors of about 10% or higher; more improvement is achieved in albedo and transmittance in the visible band, and transmittance and absorptance in the near-infrared (NIR) band. For diffuse incident radiation, both the two-stream and four-stream approximations always have a higher accuracy in the NIR band than in the visible band, but the improvement of the four-stream approximation is larger for the visible band than for the NIR band. In addition, they have a higher accuracy in describing canopy albedo, transmittance and absorption for direct incident radiation than for diffuse incident radiation. However, the improvement of the four-stream is higher for diffuse incident radiation than for direct incident radiation. The inclusion of soil albedo as the low boundary does not degrade the performance of the four-stream approximation. As an analytical model, the four-stream approximation can be easily applied as an efficient approach to improving the parameterization of land surface radiation in climate models.
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页数:12
相关论文
共 24 条
[1]  
Abell M.L., 2004, DIFFERENTIAL EQUATIO
[2]  
BONAN G, 1996, NCARTN429
[3]  
COAKLEY JA, 1975, J ATMOS SCI, V32, P409, DOI 10.1175/1520-0469(1975)032<0409:TTSAIR>2.0.CO
[4]  
2
[5]  
DICKINSON RE, 1983, ADV GEOPHYS, V25, P305
[6]  
KING MD, 1986, J ATMOS SCI, V43, P784, DOI 10.1175/1520-0469(1986)043<0784:CAOSMS>2.0.CO
[7]  
2
[8]   Estimation of vegetation canopy leaf area index and fraction of absorbed photosynthetically active radiation from atmosphere-corrected MISR data [J].
Knyazikhin, Y ;
Martonchik, JV ;
Diner, DJ ;
Myneni, RB ;
Verstraete, M ;
Pinty, B ;
Gobron, N .
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 1998, 103 (D24) :32239-32256
[9]  
Knyazikhin Y, 1998, J GEOPHYS RES-ATMOS, V103, P32257, DOI [10.1029/98JD02462, 10.1029/98JD02461]
[10]  
Li J, 1996, J ATMOS SCI, V53, P1174, DOI 10.1175/1520-0469(1996)053<1174:FSSHEA>2.0.CO