Abstract
The changes in the winter climatology and variability of the East Asian winter monsoon (EAWM) for the late 21st century (2070–2099) under the Representative Concentration Pathway (RCP) 4.5 and 8.5 scenarios are projected in terms of EAWM indices (EAWMIs). Firstly, the capability of the climate models participating in the Coupled Model Intercomparison Project phase 5 (CMIP5) in simulating the boreal winter climatology and the interannual variability of the EAWM for the late 20th century (1971–2000) is examined. Nine of twenty-three climate models are selected based on the pattern correlations with observation and a multi-model ensemble is applied to the nine model data. Three of twelve EAWMIs that show the most significant temporal correlations between the observation and CMIP5 surface air temperatures are utilized. The ensemble CMIP5 is capable of reproducing the overall features of the EAWM in spite of some biases in the region. The negative correlations between the EAWMIs and boreal winter temperature are well reproduced and 3–5 years of the major interannual variation observed in this region are also well simulated according to power spectral analyses of the simulated indices. The fields regressed onto the indices that resemble the composite strong winter monsoon pattern are simulated more or less weakly in CMIP5 compared to the observation. However, the regressed fields of sea level pressure, surface air temperature, 500-hPa geopotential height, and 300-hPa zonal wind are well established with pattern correlations above 0.83 between CMIP5 and observation data. The differences between RCPs and Historical indicate strong warming, which increases with latitude, ranging from 1 to 5 °C under RCP4.5 and from 3 to 7 °C under RCP8.5 in the East Asian region. The anomalous southerly winds generally become stronger, implying weaker EAWMs in both scenarios. These features are also identified with fields regressed onto the indices in RCPs. The future projections reveal that the interannual variability of the indices will be maintained with an intensity similar to that of the present. The correlation between monsoon indices and Arctic Oscillation increases over time. On the other hand, the correlation between monsoon indices and North Atlantic Oscillation decreases.
Highlights
The East Asian winter monsoon (EAWM), which is related to the Siberian High (SH), the Aleutian Low (AL), lowlevel northerly winds, and the surface air temperature over eastern China, Korea, and Japan, is the major climate component in East Asia (EA) during the boreal winter (Lau and Li 1984; Chang et al 2006; Wang et al 2013)
The warm bias at the surface is significant over the SH region extending to the zonal direction
The magnitude of the temperature at 2-m height (T2m) bias is larger over land than over ocean
Summary
The East Asian winter monsoon (EAWM), which is related to the Siberian High (SH), the Aleutian Low (AL), lowlevel northerly winds, and the surface air temperature over eastern China, Korea, and Japan, is the major climate component in East Asia (EA) during the boreal winter (Lau and Li 1984; Chang et al 2006; Wang et al 2013). Limited studies have been performed to enhance our understanding of the EAWM under future climate change scenarios (Wei and Bao 2012; Gong et al 2014) because of its complicated thermodynamics (Wang et al 2001). Hori and Ueda (2006) evaluated nine CGCMs and found that the weakening of the tropical local Hadley circulation is likely to weaken the EA Jet and the resultant EAWM under A1B scenario These studies focused on the changes of the EAWM under global warming emissions scenarios (IPCC 2000). The present study goal is to examine the performance of reproducibility of the EA winter atmospheric circulations using the CMIP5 dataset and its future change under the Representative Concentration Pathway (RCP) 4.5 and 8.5 in terms of EAWMIs. Section 2 describes reanalysis datasets and presents a brief description of the models and analysis method.
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