青藏高原隆升影响东亚副热带西风急流的数值试验

Numerical Experiments for the Impacts of the Uplift of the Tibetan Plateau on the Variation of East Asian Subtropical Westerly Jet

利用p-σ九层区域气候模式进行高原隆升对东亚副热带西风急流影响的敏感性试验,分析高原隆升过程中西风急流垂直结构和水平结构的变化,并对其变化的原因进行初步分析.数值试验结果表明,在西风急流垂直结构上,高原隆升后冬季沿90°E高原南侧由低层到高层西风增强,沿115°E经圈在35°N以南中高层西风增强,35°N以北中高层西风减弱,夏季沿90°E高原南侧中高层东风明显减弱,沿140°E在35°N以南中高层西风增强,35°N以北中高层西风减弱.在西风急流水平结构上,冬季沿40°N从100°E到120°E一带200hPa西风风速显著减弱,而孟加拉湾至华南至日本南部海上一带200hPa西风风速则显著增强;夏季沿42°N从120°E到150°E一带200hPa西风风速显著减弱,而沿25°N从120°E到150°E一带200hPa西风风速则显著增强.冬季高原冷源作用加强和日本西南海上潜热增加所导致东亚500至200hPa平均温度发生变化以及高原隆起后对西风急流绕流作用的增强共同导致东亚西风急流发生变化,夏季则是高原热源作用加强以及朝鲜半岛和日本西南海上潜热减少导致东亚500至200hPa平均温度发生变化,进而导致东亚西风急流发生变化.此外,无论冬季还是夏季,对流层中上层温度变化及其所导致的200hPa风速变化均是在从高原隆升高度为现在高度的1/4至1/2期间变化最为显著.

Sensitive experiments were performed by using a regional climate model with p- σ incorporated coordinate to investigate the impacts of the uplift of the Tibetan Plateau on the East Asian subtropical westerly jet （EAWJ）. The variation of the vertical structure and the horizontal structure of EAWJ at the different uplift height of the Tibetan plateau as well as the reason for the variation of EAWJ had also been analyzed in this paper. The numerical experiment results indicate that with the uplifting of the Tibetan plateau the westerly jet along 90°E in winter from lower layer to upper layer is obviously strengthened to the south side of the plateau, and the westerly wind along 115°E in mid-upper layer is obviously enhanced to the south of 35°N, while the westerly wind weakens to the north of 35°N. In summer the changes of EAWJ in vertical structure are evident. Along 90°E the easterly wind in mid-upper layer is obviously weakened to the south of the plateau, and the westerly wind in mid-upper layer along 140°E is enhanced to the south of 35°N but it is obviously weakened to the north of 35°N. Analysis of the variation of the EAWJ horizontal structure shows that the zonal wind at 200 hPa along 40°N from 100°E to 120°E is weakened while the zonal wind at 200 hPa is strengthed from Bay of Bengal to South China area. In summer the zonal wind at 200 hPa is obviously weakened along 42°N from 120°E to 150°E while it is markedly enhanced along 25°N from 120° E to 150°E. The devouring role of the Plateau together with the variation of the temperature averaged from 500 hPa to 200 hPa which is caused by the enhance of the cold cradle role of the Plateau and the increase of the latent heat flux in the south of Japan bring on the changes of EAWJ in winter. While in summer , the decrease of the latent heat flux over the Korean Peninsula and south Japan together with the enhance of the warm cradle role of the Plateau results in the temperature change averaged from 500 hPa to 200 hPa, and further leads to the variation of EAWJ. In addition, regardless of the winter or the summer, the variation of temperature in the mid-upper troposphere and the resulted variation of the zonal wind at 200 hPa are most remarkable during the period from when the plateau height uplifts from 1/4 of the present height to half of the present height.