On the basis of Coupled Model Intercomparison Project phase 5 (CMIP5) models, this study have examined the ability of models to capture the El Niño/Southern Oscillation (ENSO)-Indian Ocean Basin Mode (IOBM) relationship, and investigated the characteristics of interdecadal change of ENSO-IOBM relationship as well as the response of the ENSO-IOBM relationship to the global warming. Among 23 CMIP5 models, the capability of models in representing the IOBM depends largely on the simulation of ENSO. Moreover, half of the models can reproduce the unstable ENSO-IOBM relationship. Considering the simulations of ENSO, ENSO-IOBM relationship and interdecadal change, 6 of 23 CMIP5 models are chosen for further investigation. The interdecadal change of ENSO-IOBM relationship is relative to the three ENSO-related processes. During the high correlation (HC) period, the tropospheric temperature (TT) mechanism, oceanic Rossby waves and antisymmetric wind pattern are strong, prolonging the persistence of IOBM. In comparison, during the low correlation (LC) period, the three processes are weak. The results show that the shallow thermocline in the southwestern Indian Ocean (SWIO), increased interannual variability and prolonged periodicity of ENSO are all responsible for the interdecadal change.Furthermore, the possible changes of ENSO-IOBM relationship in the future are investigated. The ENSO-related tropical Indian Ocean (TIO) warming is strengthened under global warming. Despite the deepened thermocline over SWIO and unchanged ENSO activity, the ENSO-related TIO warming is strengthened by the enhanced TT mechanism, which is caused by the increased saturated specific humidity. The results reveal that there is more downward net heat flux (NHF) over the TIO, which is conducive to the TIO warming, and the latent heat flux (LHF) change makes a great contribution to the NHF change. The weakened upward or strengthened downward LHF is possibly due to the decreased anomalous sea-air temperature difference by strengthened TT mechanism.

Based on observed daily precipitation data, monthly gridded radiosonde upper air temperature and sea surface temperature data from the UK Met Office Hadley Centre, monthly surface air temperature from the Climatic Research Unit at the University of East Anglia and the NCEP/NCAR monthly reanalysis data, this study investigates the spatial and temporal variations of light rain events over China and the mid-high latitudes of the Northern Hemisphere during 1961-2010, and discusses the relationship between the change of light rain events and atmospheric stability, sea surface temperature and atmospheric circulation. The light rain events over East China display a decreasing trend of 3.0%/10 a in summer and winter half years. Over Northwest China, an increasing trend of 4.1%/10 a is found in winter half years, but there is no trend in summer half years. Using empirical orthogonal function (EOF) analysis, it is found that the first two principal components of light rain events over the mid-high latitudes of the Northern Hemisphere show long time scale variations in summer and winter half years. The first EOF modes (EOF1s) for summer and winter half years both depict a long-term increase in light rain events over North America and Southern Europe as well as Northwest China (except in summer half years), and a long-term decrease over most of the Eurasia (Central Europe, Eastern Europe, North Asia and East China). The second EOF mode (EOF2) for summer half year shows that light rain events increase over North America, Southern Europe and South China, but decrease over Eurasia north of 45°N from 1961 to early 1980s, while the trends reverse from late 1980s to 2010. The second EOF mode (EOF2) for winter half years indicates that light rain events increase over North America and South and North China, but decrease over Eurasia north of 40°N from 1961 to early 1980s, while the trends reverse from late 1980s to 2009. Correlation analysis and linear regression analysis suggest that EOF1s may be related to the change in atmospheric static stability associated with global warming, and EOF2s are possibly linked to the AMO. light rain, the mid-high latitudes of the Northern Hemisphere, EOF, atmospheric stability, global warming Citation: Huang G, Wen G H. Spatial and temporal variations of light rain events over China and the mid-high latitudes of the Northern Hemisphere.