The temporal and spatial variation in soil temperature play a significant role in energy and water cycle between land surface and atmosphere on the Tibetan Plateau.Based on the observed soil temperature data（hourly d...The temporal and spatial variation in soil temperature play a significant role in energy and water cycle between land surface and atmosphere on the Tibetan Plateau.Based on the observed soil temperature data（hourly data from 1 January 2001 to 31 December 2005）obtained by GAME-Tibet,the diurnal,seasonal and interannual variations in soil temperature at BJ site（31.37°N,91.90°E; 4509 m a.s.l.）near Naqu in the central Tibetan Plateau were analyzed.Results showed that the average diurnal variation in soil temperature at 4 and 20 cm depth can be described as sinusoidal curve,which is consistent with the variation of solar radiation. However,the average diurnal variation in soil temperature under 60 cm was very weak.The average diurnal amplitude in soil temperature decreased by the exponential decay function with the increase of soil depth（R2=0.92,p〈0.01）.It is demonstrated that the average diurnal maximum soil temperature decreased by the exponential decay function with the increase of soil depth（R2=0.78,p〈0.01）.In contrast, the average diurnal minimum soil temperature increased by the exponential grow function with increasing of soil depth（R2=0.86,p〈0.01）.There were a linear negative correlation between the average annual maximum Ts and soil depth（R2=0.96, p〈0.01）,a logarithmic function relationship between the average annual minimum soil temperature and soil depth（R2=0.92,p〈0.01）.The average seasonal amplitude in soil temperature followed the exponential decay function with the increase of soil depth（R2=0.98,p〈0.01）.The mean annual soil temperature in each layer indicated a warming trend prominently.During the study period,the mean annual soil temperature at 4,20,40,60,80,100,130, 160,200 and 250 cm depth increased by 0.034,0.041, 0.061,0.056,0.062,0.050,0.057,0.051,0.047 and 0.042℃/a,respectively.展开更多
In this paper we study nonlinear periodic deep water waves propagating on a background shear current,which decays exponentially with depth.We extend the study of Cheng,Cang and Liao(2009) by introducing a second param...In this paper we study nonlinear periodic deep water waves propagating on a background shear current,which decays exponentially with depth.We extend the study of Cheng,Cang and Liao(2009) by introducing a second parameter which measures the depth of the shear current.A high-order convergent analytical series solution is obtained by the homotopy analysis method(HAM).A detailed analysis of the impact of the depth parameter is given.We find that increasing this parameter so that the shear current is thinner reduces the wave phase speed,smoothes the wave crest,sharpens the trough,and enlarges the maximum wave height for the case of propagating waves on an opposing current;while it produces the opposite effect on an aiding current.展开更多
基金sponsored jointly by the National Natural Science Foundation of China(41075007)the One Hundred Talent Program of the Chinese Academy of Sciences(29O827B11)the National Key Basic Research program of China(2010CB951404)
文摘The temporal and spatial variation in soil temperature play a significant role in energy and water cycle between land surface and atmosphere on the Tibetan Plateau.Based on the observed soil temperature data（hourly data from 1 January 2001 to 31 December 2005）obtained by GAME-Tibet,the diurnal,seasonal and interannual variations in soil temperature at BJ site（31.37°N,91.90°E; 4509 m a.s.l.）near Naqu in the central Tibetan Plateau were analyzed.Results showed that the average diurnal variation in soil temperature at 4 and 20 cm depth can be described as sinusoidal curve,which is consistent with the variation of solar radiation. However,the average diurnal variation in soil temperature under 60 cm was very weak.The average diurnal amplitude in soil temperature decreased by the exponential decay function with the increase of soil depth（R2=0.92,p〈0.01）.It is demonstrated that the average diurnal maximum soil temperature decreased by the exponential decay function with the increase of soil depth（R2=0.78,p〈0.01）.In contrast, the average diurnal minimum soil temperature increased by the exponential grow function with increasing of soil depth（R2=0.86,p〈0.01）.There were a linear negative correlation between the average annual maximum Ts and soil depth（R2=0.96, p〈0.01）,a logarithmic function relationship between the average annual minimum soil temperature and soil depth（R2=0.92,p〈0.01）.The average seasonal amplitude in soil temperature followed the exponential decay function with the increase of soil depth（R2=0.98,p〈0.01）.The mean annual soil temperature in each layer indicated a warming trend prominently.During the study period,the mean annual soil temperature at 4,20,40,60,80,100,130, 160,200 and 250 cm depth increased by 0.034,0.041, 0.061,0.056,0.062,0.050,0.057,0.051,0.047 and 0.042℃/a,respectively.
基金supported by the National Natural Science Foundation of China (Grant No.51002195)
文摘In this paper we study nonlinear periodic deep water waves propagating on a background shear current,which decays exponentially with depth.We extend the study of Cheng,Cang and Liao(2009) by introducing a second parameter which measures the depth of the shear current.A high-order convergent analytical series solution is obtained by the homotopy analysis method(HAM).A detailed analysis of the impact of the depth parameter is given.We find that increasing this parameter so that the shear current is thinner reduces the wave phase speed,smoothes the wave crest,sharpens the trough,and enlarges the maximum wave height for the case of propagating waves on an opposing current;while it produces the opposite effect on an aiding current.
