Variation of cloud amount over China and the relationship with ENSO from 1951 to 2014

Abstract

ABSTRACTIn this study, the climatic trend of the total cloud amount (TCA) and the low cloud amount (LCA) was studied using climate diagnostic methods while the correlations and possible physical mechanism between TCA, LCA and El Niño and Southern Oscillation (ENSO) were analysed and discussed. The results indicated that the annual average TCA and LCA reduced with increasing latitude while a significant decreasing trend has been derived for TCA and LCA; the trend rate is 0.9% per decade and 0.2% per decade, respectively. Moreover, the most obvious reduction area of TCA was focused in Northeast China and for LCA, it was located in the surrounding area of the Shaanxi province. The cloud amounts of the four seasons also showed a reducing tendency except the LCA of summer. Meanwhile, the spectrum analysis showed that TCA has 10, 5.7, 3.6 and 2.8 year periods and LCA has 10, 4, 2.7 and 2.1 year‐long time cycles. Further analysis also revealed that the annual average TCA has a significant negative correlation with ENSO, and the most remarkable negative correlation centre is focused on central China. However, the relationship of the annual average LCA with ENSO is relatively weak. Except in spring, the spatial correlation distribution of TCA and LCA with ENSO in the other seasons was consistent with that of the annual average TCA and LCA, and 4‐year periods of TCA and LCA coincide with the cycle of ENSO. This reveals that ENSO has an impact on inter‐annual variations of TCA and LCA over China. It is generally considered that ENSO, through the atmospheric circulation situation, causes variation of cloud amounts.