Multi‐Model Projection of the Interannual Relationship Between Spring Hadley Circulation and East Asian Summer Circulation under Global Warming

Abstract

AbstractObservations indicate that spring Hadley circulation is tightly linked to East Asian summer circulations and precipitation on the interannual timescale. Whether does such a relationship tend to change under the background of global warming in the future? To answer this question, this work chose five climate models (GFDL_CM2_0, GFDL_CM2_1, IAP_FGOALS_1.0g, NCARCCSM, UKMO_HADCM3), which can well reproduce the observed interannual variability of spring Hadley circulation in the North Hemisphere and its linkage to East Asian summer atmospheric circulations and precipitation, based on overall assessment of models' simulation ability. Then, the potential change of the interannual variability of spring Hadley circulation and its interannual connection with East Asian summer circulations and precipitation under the A1B scenario are projected by using the outputs of these five climate models. To facilitate quantitative estimation of their changes, five indices are exploited in this study. The Northern Hemispheric Hadley circulation index (HCI) is defined as the maximum value of the zonal mean mass stream function occurring within the latitudinal zone of 0°–30°N, and the western Pacific subtropical high index (WPSHI) as the 850 hPa geopotential height anomalies averaged over the region (10°N–30°N, 110°E–150°E). The difference of zonal wind anomalies at 850 hPa between the region (10°N–20°N, 100°E–150°E) and (25°N–35°N, 100°E–150°E) and that at 200 hPa between the region (25°N–35°N, 80°E–150°E) and (40°N–50°N, 80°E–150°E) are used to define the East Asian summer monsoon index (EASMI) and the East Asian Jet index (EAJI), respectively. The East Asian rainfall index is represented by mean precipitation over the region (27°N–32°N, 110°E–130°E). The multi‐model ensemble (MME) results show that the interannual variability of the Northern Hemispheric Hadley circulation in spring tends to decrease by 23% in the late 21st century (2070–2099) as compared to the late 20th century (1970–1999). Concurrent with the decreasing interannual variability of spring Hadley circulation, its linkage to summer western Pacific subtropical high and East Asian summer monsoon is also projected to be weakened. The correlation coefficients between spring HCI and summer WPSHI (EASMI) decrease from 0.44 (–0.46) in the late 20th century to 0.19 (–0.15) in the late 21st century. Such a change can be simulated consistently by individual models. In addition, the MME results suggest that the association of spring Hadley circulation with summer East Asian jet and precipitation will be weakened as well. However, there are discrepancies in the changes of their relationships among individual models.