Abstract
The atmospheric heat source over the Qinghai–Tibetan Plateau (QTP) in spring has an important impact on the climate of the surrounding regions. However, there have been few systematic studies of the dominant mode of the heat source and the cross-seasonal connections with the preceding winter and following summer. Using a distinct empirical orthogonal function (DEOF) decomposition method, we obtained the leading mode of the spring heat source over the QTP and the surrounding regions and analyzed its precursors in the previous winter and lagging effects in the following summer. Our results show that the first mode (DEOF1) was characterized by a warm plateau and cold surrounding regions. The positive phase was significantly associated with the warm Arctic–cold Siberia (WACS) pattern (r = 0.39, p = .01) and the La Niña-like SST anomaly in the Pacific in the preceding winter and the following East Asian subtropical summer monsoon (r = –0.44, p = .01), resulting in a widespread drought in China during the following summer. The cold anomaly in Siberia and the warm anomaly at mid-to low latitudes in winter associated with the WACS pattern coincide with the DEOF1 mode of the heat source over the QTP and its surroundings through change of meridional temperature gradient and wave-flow interactions. A mid-latitude wave train excited by the WACS and the thermal difference in the meridional direction of the spring DEOF1 mode caused high-pressure anomalies over the QTP and the mid-latitude region of East Asia, influencing central and eastern China. This anomaly was not conducive to the northward advancement of the East Asian summer monsoon, resulting in drought in most of China in spring and summer. The cross-seasonal relationship between the main mode of the spring heat source on the QTP and the preceding winter WACS pattern and the following East Asian summer monsoon can be used as a reference in climate prediction studies.
Highlights
The Qinghai–Tibetan Plateau (QTP) covers a quarter of China’s land area and has an average altitude >4,000 m, making it the highest and most complex plateau in the world
We used atmospheric heat source/sink dataset over the Tibetan Plateau based on satellite and 80 routine meteorological station (Duan, 2019), provided by the National Tibetan Plateau Data Center of China, to verify the heat source data calculated by the ERA5 reanalysis data
We verified the cross-seasonal relationships in the observations between the spring QTP 〈Q1〉 and the previous winter and postsummer climate factors using two methods: 1) partial correlation analysis to test the dependence and independence of these relations; and 2) CMIP6 Historical simulation test data to verify whether such relationships exist in the model
Summary
The Qinghai–Tibetan Plateau (QTP) covers a quarter of China’s land area and has an average altitude >4,000 m, making it the highest and most complex plateau in the world. Some studies have shown that this change is an important signal of the seasonal change in the thermal field over the QTP (Yanai et al, 1992; Daisuke et al, 2003) This transformation of the heat source has an important impact on the seasonal transition of the atmospheric circulation in late summer. We obtained the main mode of the heat source in spring and studied its cross-seasonal relationship with the atmospheric circulation in the preceding winter and following summer. This is of great scientific significance for the in-depth understanding of the change in the QTP heat source in spring and climate variability in East Asia and can be used as a reference value for cross-seasonal climate prediction
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