Impacts of internal climate variability on meteorological drought changes in China

Drought is one of the extreme events that can be caused by internal climate variability （ICV） and external forcing （EF）. Here, the authors investigate the relative contributions of ICY and EF to meteorological drought changes in China using 40 members from the Community Earth System Model Large Ensemble （CESE_LE） project for historical simulations （in response to greenhouse gases and other EF） and future simulations under the RCP8.5 scenario. The authors use the Standardized Precipitation Index （SPI） to represent meteorological drought, and then define and analyze four drought parameters （frequency, severity, duration, and maximum duration） over eight regions of China. For historical periods, the ICV plays a dominant role in drought variation, while with global warming under the RCP8.5 scenario the EF becomes the prominent factor for drought characteristics. With the global warming signal, the effect of ICV varies with the drought parameters. This study suggests that the ICV should be taken into account when climate model simulations are used to investigate drought--in particular, for historical periods.

A dominant role of internal climate variability in controlling Atlantic multidecadal variability during the past 1200 years

Subject Code:D02With the support by the National Natural Science Foundation of China,a collaborative study by the research group led by Prof.Yang Bao(杨保)from the Key Laboratory of Desert and Desertification,Northwest Institute of Eco-Environment and Resources of the Chinese Academy of Sciences,and

Simulation by CMIP5 Models of the Atlantic Multidecadal Oscillation and Its Climate Impacts

This study focuses on the climatic impacts of the Atlantic Multidecadal Oscillation （AMO） as a mode of internal vari- ability. Given the difficulties involved in excluding the effects of external forcing from internal variation, i.e., owing to the short record length of instrumental observations and historical simulations, we assess and compare the AMO and its related climatic impacts both in observations and in the ＂Pre-industrial＂ experiments of models participating in CMIP5. First, we evaluate the skill of the 25 CMIP5 models＇ ＂Historical＂ simulations in simulating the observational AMO, and find there is generally a considerable range of skill among them in this regard. Six of the models with higher skill relative to the other models are selected to investigate the AMO-related climate impacts, and it is found that their ＂Pre-industrial＂ simulations capture the essential features of the AMO. A positive AMO favors warmer surface temperature around the North Atlantic, and the Atlantic ITCZ shifts northward leading to more rainfall in the Sahel and less rainfall in Brazil. Furthermore, the results confirm the existence of a teleconnection between the AMO and East Asian surface temperature, as well as the late withdrawal of the Indian summer monsoon, during positive AMO phases. These connections could be mainly caused by internal climate variability. Opposite patterns are true for the negative phase of the AMO.

Brief News of International Workshop on Climate Variabilities (IWCV) Held on July 13-17,1992 in Beijing

Climatic anomalies have drawn more and more attentions not only in the worldwide scientific circle, but also in the respect of many governments in the last decade. The floods and drought occurred in China and many other countries cause severe damages and lead to the crises of grain production, water resources and energy. The sustained aridity in Africa and other Continents and the land desertization make millions of people face imperilling of starvation. All these greatly affect the long-term development of nations, societies and economics