Impact of spatial heterogeneity of soil moisture on mesoscale fluctuations and mesoscale fluxes
土壤含水量空间尺度分布非均匀对中尺度脉动量和通量的影响研究

Land surface heat fluxes and atmospheric boundary layer (ABL) are simulated using the Regional Atmospheric Modeling System (RAMS). Eight experiments on land-surface wetness discontinuities with heterogeneous length scales from 40km to 2km are carried out without large-scale background wind. The two-dimensional amplitude spectra of land surface heat fluxes, mesoscale fluctuations and mesoscale heat fluxes are analyzed by two-dimensional fast Fourier transform algorithm (FFT). Then ABL parameterization for large-scale models, such as GCM (General Circulation Model) is discussed. The results show that amplitude spectra of the land surface heat fluxes and the mesoscale fluctuations in each experiment reach maximum, when wave number is corresponding to heterogeneous length scale, and when different length scales coexist, the largest scale is dominant. Differently, amplitude spectra of the mesoscale heat fluxes, besides wave number corresponding to heterogeneous length scale, still have several peaks at other wave numbers. It appears that the relationships between the land surface heat fluxes and the heterogeneous length scale are significant, but the mesoscale heat fluxes don't indicate similar relationships with heterogeneous length scale. The representability of grid-cell averaged surface fluxes is good but that of mesoscale fluxes is not so good.