Aerodynamic roughness length （Z0m） is a key factor in surface flux estimations with remote sensing algorithms and/or land surface models. This paper calculates ZOrn over several land surfaces, with 3 years of experi...Aerodynamic roughness length （Z0m） is a key factor in surface flux estimations with remote sensing algorithms and/or land surface models. This paper calculates ZOrn over several land surfaces, with 3 years of experimental data from Xiaotangshan. The results show that Z0m is direction-dependent, mainly due to the heterogeneity of the size and spatial distribution of the roughness elements inside the source area along different wind directions. Furthermore, a heuristic parameterization of the aerodynamic roughness length for heterogeneous surfaces is proposed. Individual Z0m over each surface component （patch） is calculated firstly with the characteristic parameters of the roughness elements （vegetation height, leaf area index, etc.）, then Z0m over the whole experimental field is aggregated, using the footprint weighting method.展开更多
Based on Hadley Center monthly global SST,1960-2009 NCEP/NCAR reanalysis data and observation rainfall data over 160 stations across China,the combined effect of Indian Ocean Dipole(IOD)and Pacific SSTA(ENSO)on winter...Based on Hadley Center monthly global SST,1960-2009 NCEP/NCAR reanalysis data and observation rainfall data over 160 stations across China,the combined effect of Indian Ocean Dipole(IOD)and Pacific SSTA(ENSO)on winter rainfall in China and their different roles are investigated in the work.The study focuses on the differences among the winter precipitation pattern during the years with Indian Ocean Dipole(IOD)only,ENSO only,and IOD and ENSO concurrence.It is shown that although the occurrences of the sea surface temperature anomalies of IOD and ENSO are of a high degree of synergy,their impacts on the winter precipitation are not the same.In the year with positive phase of IOD,the winter rainfall will be more than normal in Southwest China(except western Yunnan),North China and Northeast China while it will be less in Yangtze River and Huaihe River Basins.The result is contrary during the year with negative phase of IOD.However,the impact of IOD positive phase on winter precipitation is more significant than that of the negative phase.When the IOD appears along with ENSO,the ENSO signal will enhance the influence of IOD on winter precipitation of Southwest China(except western Yunnan),Inner Mongolia and Northeast China.In addition,this paper makes a preliminary analysis of the circulation causes of the relationship between IOD and the winter rainfall in China.展开更多
基金supported by the Hi-tech Research and Development Program of China(2007AA12Z175)the Special Research Foundation of the Public Benefit Industry (GYHY200706046)+1 种基金the Project funded by the National Natural Science Foundation of China (Grant No. 40671128)the National Basic Research Program of China (2007CB714401)
文摘Aerodynamic roughness length （Z0m） is a key factor in surface flux estimations with remote sensing algorithms and/or land surface models. This paper calculates ZOrn over several land surfaces, with 3 years of experimental data from Xiaotangshan. The results show that Z0m is direction-dependent, mainly due to the heterogeneity of the size and spatial distribution of the roughness elements inside the source area along different wind directions. Furthermore, a heuristic parameterization of the aerodynamic roughness length for heterogeneous surfaces is proposed. Individual Z0m over each surface component （patch） is calculated firstly with the characteristic parameters of the roughness elements （vegetation height, leaf area index, etc.）, then Z0m over the whole experimental field is aggregated, using the footprint weighting method.
基金National Natural Science Foundation of China(41175051)National Basic Research Program of China(973 Program)(2012CB957804)
文摘Based on Hadley Center monthly global SST,1960-2009 NCEP/NCAR reanalysis data and observation rainfall data over 160 stations across China,the combined effect of Indian Ocean Dipole(IOD)and Pacific SSTA(ENSO)on winter rainfall in China and their different roles are investigated in the work.The study focuses on the differences among the winter precipitation pattern during the years with Indian Ocean Dipole(IOD)only,ENSO only,and IOD and ENSO concurrence.It is shown that although the occurrences of the sea surface temperature anomalies of IOD and ENSO are of a high degree of synergy,their impacts on the winter precipitation are not the same.In the year with positive phase of IOD,the winter rainfall will be more than normal in Southwest China(except western Yunnan),North China and Northeast China while it will be less in Yangtze River and Huaihe River Basins.The result is contrary during the year with negative phase of IOD.However,the impact of IOD positive phase on winter precipitation is more significant than that of the negative phase.When the IOD appears along with ENSO,the ENSO signal will enhance the influence of IOD on winter precipitation of Southwest China(except western Yunnan),Inner Mongolia and Northeast China.In addition,this paper makes a preliminary analysis of the circulation causes of the relationship between IOD and the winter rainfall in China.
