Surface air temperature patterns on a decadal scale in China using self‐organizing map and their relationship to Indo‐Pacific warm pool

Abstract

ABSTRACTIn this study, nine decadal‐scale surface air temperature (SAT) patterns in China during 1902–2007 were obtained from Climatic Research Unit data using the self‐organizing map based on the ensemble empirical mode decomposition. To further investigate the relationship between decadal SAT patterns in China and the Indo‐Pacific warm pool (IPWP), we aggregated the selected nine neurons into three significant types based on the similarities of the reference vectors using a hierarchical agglomerative clustering approach. Among the three patterns, Pattern 1 is a cold pattern and Pattern 3 is a warm pattern. Pattern 2 is a medium mode, in which the west of China is cold, but eastern China is warm. The relationship between the IPWP and SAT in China at the decadal scale can be summarized as follows. When the IPWP is warmer, easterly wind anomalies are stronger over the equatorial Pacific Ocean, the IPWP shrinks westwards predominantly and the heat centre is to the west. Furthermore, easterly wind anomalies strengthen the trade winds, so that poleward energy transport by the ocean increases, while poleward energy transport by the atmosphere decreases in the tropics. Meanwhile, the Aleutian Low and East Asian trough strengthen, and the meridional circulation is dominated, which is of benefit to cold air from the high latitude that move to the southeast, making the temperature in China colder. In contrast, the warm pool is colder, and the westerly wind anomalies are prevailing, making the IPWP extending eastward. Zonal circulation is dominant in the mid‐latitudes, which weakens the cold airflow into China and leads to warmer temperatures there.