论文部分内容阅读
The Taklimakan Desert plays a significant role in formation of the climates of the northwestern China and three parameters (i.e.,the bulk transfer coefficients for momentum Cd,heat Ch and water vapor Cq) characterizing the energy and mass exchanges between the land surface and the atmosphere can illustrate the significance.These three parameters can be determined using the bulk transfer equations.In this process,two important parameters have to be determined: the aerodynamic roughness length (z0m) and the thermal roughness length (z0h).This study analyzed the diurnal and monthly variations of surface roughness lengths and bulk transfer coefficients based on the observed data from January to December 2009 in the hinterland of Taklimakan Desert.The flux method was adopted,and the parameterization scheme of z0m was developed,as well as characteristic of z0h and excess resistance to heat transfer (kB-1) were discussed.The calculated means of z0m and z0h are 2.91×10-3 m and 1.44×10-5 m,respectively.It should be noted that the temporal patterns of the diurnal and monthly variations of the parameters (i.e.,z0m,z0h,kB-1,Cd and Cd) obtained from Taklimakan Desert are fundamentally different from those reported from vegetated areas.Specifically,four unique features can be identified.First,z0m in the Taklimakan Desert does not change with seasons but is strongly dependent on wind speed.Second,z0h is considerably higher in daytimes than that in nighttimes.Third,the bulk transfer coefficients (Cd and Ch) values rise rapidly to reach their peaks at sunrise because the turbulence intensity is the highest at sunrise.Fourth,both Cd and Ch values are higher in winter and lower in summer.In addition,the calculated means of Cd and Ch are 4.88×10-3 and 2.52×10-3,respectively.