CAJ | 학술논문

研究I的结果表明：线性平衡方程（LBE）在热带地区不适用，而进一步改进方向是削弱LBE在该区域的约束程度。本文以此为基础，在GRAPES（global/regional assimilation and prediction system）全球变分同化系统中引入动力与统计混合平衡约束方案。新方案在逐层求解 LBE 的基础上增加垂直方向的线性回归，回归系数随纬度和高度变化。针对背景误差协方差的分析表明，新方案可以更好的保证独立分析变量间预报误差不相关的基本要求，并大幅度减小热带地区平衡气压预报误差方差的量值和占总方差的比例。单点试验结果表明，与 LBE方案相比，新方案对中、高纬影响很小，但在热带地区成功实现了风、压场分析的解耦，两者分析更为独立。并且，虽未考虑具体波动模态，但新方案给出的风、压场协相关结构与研究I的理论分析结果相近。一个月的同化循环与预报结果表明，引入新方案后，赤道外地区的同化预报效果为中性偏正，而热带地区风场的同化预报效果显著提高，LBE方案中平流层低层的风场同化预报异常被基本消除。
연구I적결과표명：선성평형방정（LBE）재열대지구불괄용，이진일보개진방향시삭약LBE재해구역적약속정도。본문이차위기출，재GRAPES（global/regional assimilation and prediction system）전구변분동화계통중인입동력여통계혼합평형약속방안。신방안재축층구해 LBE 적기출상증가수직방향적선성회귀，회귀계수수위도화고도변화。침대배경오차협방차적분석표명，신방안가이경호적보증독립분석변량간예보오차불상관적기본요구，병대폭도감소열대지구평형기압예보오차방차적량치화점총방차적비례。단점시험결과표명，여 LBE방안상비，신방안대중、고위영향흔소，단재열대지구성공실현료풍、압장분석적해우，량자분석경위독립。병차，수미고필구체파동모태，단신방안급출적풍、압장협상관결구여연구I적이론분석결과상근。일개월적동화순배여예보결과표명，인입신방안후，적도외지구적동화예보효과위중성편정，이열대지구풍장적동화예보효과현저제고，LBE방안중평류층저층적풍장동화예보이상피기본소제。
The results of Part I of this study show that the imposition of the Linear Balance Equation (LBE) in the tropics is not correct and additional steps should be taken to decouple the analysis of mass and wind fields. Based on the results in Part I, this paper developed a LBE-regression hybrid balance constraint in GRAPES (global/regional assimilation and prediction system) global variational data assimilation system. In the new scheme, after the calculation of LBE on each level, a vertical regression whose coefficients could vary at different latitudes and model levels was introduced. By analyzing and comparing the implied background error covariance of different schemes, the authors found that the new scheme could efficiently reduce the unreasonable correlations of control variables. Additionally, the forecast error variance of the balanced pressure and its ratio to the whole pressure were also both dramatically reduced in the tropics. Results of the single-observation experiments indicated that, the new scheme had little impacts on the mid-and high-latitude compared to the LBE scheme, but it did successfully decouple the mass/wind analyses in the tropics. Although equatorial wave modes were not explicitly considered in the new scheme, the structure of covariance was consist with the theory analysis results based on those modes in Part I. The results of cycle analysis and forecast experiments in one month showed that, the new scheme could bring slightly positive results in the extratropics and significantly improve the wind analysis and forecast accuracy in the tropics, the abnormally large tropical wind errors in the LBE scheme were dramatically suppressed.