半球谱模式的风场初值及其对资料同化的影响

THE INITIAL WIND SCHEME OF THE HEMISPHERIC SPECTRAL MODEL AND ITS EFFECT ON THE DATA ASSIMILATION

利用半球谱模式（Ｔ４２Ｌ９）进行了大量的资料同化和预报试验。结果表明，半球风场初值方案对资料同化和预报有重要的影响。不恰当的初值处理会导致虚假散度源，在非绝热模式中可能进一步诱发虚假的强降水与相应的潜热释放。很明显，这个问题既不同于Ｄａｌｌｅｙ［１］所分析的半球／全球范围效应，也不同于所谓的赤道资料效应。文章在前人研究的基础上，提出了散度和涡度修正方案，进而用对比试验方法讨论了该方案与其他方案的差异以及对同化的影响。初步试验表明，散度修正方案是半球资料同化中克服初值计算误差的一个较好的选择。

series of data assimilation and forecast test has been carried out with a hemispheric spectral model. It was found that the numerical scheme for determing hemispheric initial wind is important to data assimilation and forecast. An inappropriate scheme may cause the computational divergence sources near the equator, which are responsible for the spurious strong precipitation and corresponding latent heat release. Obviously, this problem differs from either the hemispheric/global domain effect or the tropical data effect pointed by Daley et al. Based on the previous studies. the new divergence and vorticity correction schemes is presented. and the difference with other schemes and its effects on the data assimilation are discussed against the control test.Preliminary tests have shown that the new divergence correction scheme proposed in this paper may be a preferable choice to overcome the initial computational errors in a hemispheric data assimilation.