The Tropospheric Energy Budgets of two Heat Source Regions within the Southwest-East Asian Summer Monsoon System: the Arabian Desert Empty Quarter and the Qinghai-Xizang Plateau

Abstract Resolution of a complex Hermitian matrix derived from monthly mean 850-hPa wind fields during the summer season (June–August) from 1968 to 2004 revealed four different modes of East Asian summer monsoon (EASM) variability. The leading EASM mode, accounting for 19.6% of the variance, is characterized by two different modes (M11 and M12) or their combination. Both portray a closed cyclonic or anticyclonic circulation anomaly over the western North Pacific (WNP), South China Sea (SCS), and southeastern China; corresponding anomalous geopotential height fields show a wave train structure from the WNP across Japan, the Okhotsk Sea, and Alaska to North America. Thus, the leading EASM mode characterizes the teleconnection pattern of the WNP-EASM. The correlation between M11 (M12) and the dynamic index for the WNP-EASM is 0.85 (0.51). M11 has leading spectral peaks at 15 and 3 yr, whereas M12 displays a predominant peak at 2 yr. It is found that M11 has interdecadal variations, with the transition years being circa 1973 and 1989, respectively. M11 is closely related to air–sea interactions in the SCS and the northwestern Pacific, and its association with the convective heat source over the northwestern Pacific is secondary. In contrast, M12 is closely related to the tropical convective heat source rather than tropical western Pacific sea surface temperature (SST). The second EASM mode, accounting for 12.8% of the variance, is identified and characterized by two distinct and alternating modes or their linear combination (M21 and M22). One mode (M21) closely relates to the dual blocking high pattern detected in anomalous sea level pressure (SLP) and 500-hPa geopotential heights over the Ural Mountains and the Okhotsk Sea. The other (M22) corresponds to a dipole blocking anomaly in anomalous SLP and geopotential heights, with opposing anomalous centers in the south of Japan and the Korean peninsula, and the area between Lake Baikal and the Okhotsk Sea. M22 shows significant correlations with summer mean rainfall in southern and southeastern China. Thus, a single index of EASM is inappropriate for investigating and predicting the EASM.

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Numerical Modeling of Topography-Modulated Dust Aerosol Distribution and Its Influence on the Onset of East Asian Summer Monsoon

Advances in Meteorology ◽

10.1155/2016/6951942 ◽

2016 ◽

Vol 2016 ◽

pp. 1-15 ◽

Cited By ~ 2

Author(s):

Hui Sun ◽

Xiaodong Liu

Keyword(s):

Heat Source ◽

East Asia ◽

Summer Monsoon ◽

East Asian Summer Monsoon ◽

Asian Summer Monsoon ◽

East Asian ◽

Dust Aerosol ◽

Summer Monsoon Onset ◽

Aerosol Distribution ◽

Asian Summer

A regional climate model coupled with a dust module was used to simulate dust aerosol distribution and its effects on the atmospheric heat source over the TP, East Asian summer monsoon onset, and precipitation in East Asia modulated by the uplift of the northern TP. We carried out four experiments, including a modern (i.e., high-mountain) experiment with (HMD) and without (HM) the major deserts in Northwest China and a low-mountain experiment with (LMD) and without (LM) the deserts. The results show that dust greatly increases in the Taklamakan Desert accompanied with the uplift of the northern TP, and the increase exceeds 150 µg kg−1in spring. A strong cyclone in the Tarim Basin produced by the uplifted northern TP enhances dust emissions in the Taklamakan Desert in summer. Meanwhile, the dust loading over the TP also increases induced by the uplift of the northern TP, causing the heat source over the TP decreased. Under the condition of the northern TP uplift to present altitude, dust delays the East Asia summer monsoon onset by two pentads and one pentad, respectively, in the southern and northern monsoon regions and greatly suppresses precipitation in East Asia compared with results in the low terrain experiments.

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