1.College of atmospheric sciences, Lanzhou University;2.贵州省气象台
为了研究湍涡对中尺度绿洲灌溉的响应，利用WRF大涡模拟模块（WRF-LES）在西北半干旱区绿洲区开展灌溉前（BI）和灌溉后（AI）两个大涡模拟试验，其中绿洲上发生的灌溉可能会改变绿洲非均匀强度。利用面积平均的办法计算湍流热通量并利用小波分析将湍流热通量模态分解到不同的尺度。 结果表明灌溉增加了土壤湿度，引起绿洲内部非均匀强度增加，灌溉对垂直热通量以及通量频散都有较大影响。AI中的湍涡为网状，与BI中一致。AI与BI中的感热通量的频散高度都随着感热通量的减小而减小。AI与BI中感热通量小波能量谱尺度一致，但是BI强度比AI小。潜热通量的频散高度依赖于感热通量，且潜热通量能量谱随高度减小。 空间滞后相关系数的结果表明由于灌溉前地表加热较强，感热通量对地表热通量的响应高度在灌溉之前（BI）比灌溉后（AI）更高。灌溉后的通量模态的飘移距离小于灌溉前的。
To investigate the response of turbulent eddies to the mesoscale heterogeneous land use change over oasis in Northwestern China, two experiments with the cases of before irrigation (BI) and after irrigation (AI) using WRF-LES model are carried out, where heterogeneity strength would be changed by irrigation over oasis. The area-averaged method is used to calculate the area-averaged flux, and the wavelet analysis is used to decompose the pattern of surface turbulent heat fluxes into multi-scale pattern. The results show that the irrigation has large influence on the vertical heat flux, soil moisture, and soil temperature. Irrigation increases the heterogeneity strength, which has large influence on the dispersion of flux pattern. The dispersion height of sensible heat flux decreases with the decrease of sensible heat flux after irrigation. The shape of turbulent eddies in AI is reticular which is similar with that in BI but the energy spectra of sensible heat flux pattern decreases after irrigation. In addition, the dispersion height of latent heat flux depends on the sensible heat flux but the energy spectra of latent heat flux pattern decreases after irrigation. From the spatial lag correlation coefficient, the height of response of vertical heat flux to the surface flux before irrigation is higher than that after irrigation. The shift distance after irrigation is less than that before irrigation. Strong surface heating results in large correlation coefficients and strong entrainment in the top of convective boundary layer.