地表以下虚假的风场资料对北半球夏季Hadley环流空间模态及下沉支未来预估的影响

Influences of False Subsurface Wind Data on Spatial Pattern of the Northern Hadley Circulation and Future Estimation of the Sinking Branch in Boreal Summer

本文利用12个CMIP5气候模式的风场资料,采用全球大气环流三型分解模型中的经圈型环流流函数,研究了地表以下虚假的风场资料对北半球夏季Hadley环流空间模态及下沉支位置未来预估的影响。结果表明:在计算Hadley环流的流函数时,由于垂直积分过程会将地表以下虚假的风场资料所带来的误差传递至整层的流函数,从而导致北半球夏季Hadley环流的空间模态中存在虚假的“小环流”,该“小环流”会导致Hadley环流下沉支位置的误判,并对下沉支位置变化趋势的准确计算产生较大影响;进一步的定量分析发现,在未来排放情境下(RCP8.5),地表以下虚假的风场资料所引起的误差会导致北半球夏季Hadley环流下沉支向极扩张趋势的高估。

Based on monthly data of wind field from 12 Coupled Model Intercomparison Project Phase 5 (CMIP5) models and the stream function of meridional circulation derived from the three-pattern decomposition global atmospheric circulation method (3P-DGAC), we investigate influences of false subsurface wind data on spatial pattern of the Northern Hadley circulation (HC) and future estimation of the sinking branch in boreal summer. It is found that errors caused by false subsurface wind data are passed to the stream function in the whole layer by vertically integrated process, which could lead to a false “minor circulation” embedded within Northern Hemispheric Hadley circulation (NHHC) in summer. The “minor circulation” would cause miscalculation of the location of the NHHC sinking branch, and it also has a significant effect on the accurate calculation of poleward expansion trend of NHHC. The result of the quantitative analysis shows that, in the 2040-2099 period under Representative Concentration Pathway 8.5 (RCP8.5) scenarios, the false wind data would lead to an overestimation of the poleward expansion trend of NHHC in summer.