青藏高原东北侧伏旱环流强迫场的数值研究

过去的研究结果指出，青藏高原东北侧的伏旱是在副高控制下的干旱，其干旱的典型环流呈上下一致的正压结构。为进一步研究青藏高原东北侧伏旱环流的维持机制，利用一个带有强迫和耗散的球面无辐散准地转正压涡度方程谱模式和经过严格挑选的五个实际典型伏旱个例（共48d)环流场，通过求解平衡方程得到了伏旱环流强迫场，再用该强迫场分别在有强迫和无强迫情形下进行了8d的数值试验。结果表明：伏旱环流的平均维持时间在一周左右，影响和维持它的外界强迫主要来自青藏高原北侧，干旱环流强迫场的存在对干旱环流的维持有重要影响。

A Numerical Study on the Forcing Field of Midsummer Drought Circulation on the Northeast Side of Qinghai-Xizang Plateau

The previous results show that the midsummer drought on thenortheast side of Qinghai-Xizang Plateau is a drought controled by the subtropical latitude high, and the structure of drought circulation displayes a barotropic state. In order to study the maintaining mechanism of the drought circulation, the resultant circulation of 5 typical midsummer drought cases and its forcing field were calculated, and the numerical experiment utilizing a spherical, nondivergent, quasi-geostrophic, barotropic vorticity equation spectral model with forcing and dissipation termes was made. The results show that the mean duration of maintenance of drought circulation is about a week or so, the existence of drougt flow forcing source regions is critical for the maintenance of the drought circulation. The main forcing source region is in the North of Qinghai-Xizang Plateau.