Research On Extreme Climate Events

Based on the comprehensive review of extreme climate events, it is pointed out that there are still many problems needed to be understood. This paper focus on the topics of the evolution of extreme climate events over time, the temporal and spatial distribution of the China's arid events, the method of abrupt climate detection, the extreme daily rainfall variations and climate complexity in Beijing area. The main conclusions are as follows:1) There exists two obvious jump of the frequency of the record-breaking events of the Palmer Drought Severity Index (PDSI) over China. The main features of the two jumps are that the PDSI record-breaking events are significantly above normal. And there is good correlation between the frequency of PDSI record-breaking events and the Pacific Decadal Oscillation.2) A new method, moving cut data-rescaled range analysis (MC-R/S), is proposed in this paper. Tests on time series suggest that the MC-R/S method almost does not depend on the length of subseries and are less affected by noises. The MC-R/S method is very suitable to detect abrupt changes of dynamic structure.3) By using Detrended Fluctuation Analysis (DFA) method, it was found that the drought and waterlogging indexes (DWI) exhibit scaling and long-range correlation characteristics. Namely, the occurrence of drought and waterlogging has persistence characteristic.4) By using extreme precipitation indices proposed by ETCCDMI Project, analysis indicates that the changes of the intensity and frequency of the extreme daily precipitation in Beijing area shows a downward trend, and the intensity and frequency of daily precipitation decrease drastically since the late 1990s.5) By using multi-scale sample entropy method, we analyze daily precipitation and daily temperature time series in order to study the complexity of the climate in Beijing. Study shows that the spatial distribution pattern of multi-scale sample entropy of the precipitation and daily temperature reflects the atmospheric circulation pattern in Beijing area as well as the impact of topography on climate. Spatial distribution of the multi-scale sample entropy of precipitation reflects the transport direction of water vapor and spatial variation of precipitation gradient. We also find that urbanization in Beijing increase the complexity of precipitation and the impact of urbanization on daily temperature is not significant.