East Asian climate change in the 21st century as simulated by the coupled climate model ECHO-G under IPCC SRES scenarios

Abstract

Future climate changes over East Asia are studied from ensemble simulations of the coupled climate model ECHO-G, based on the Intergovernmental Panel on Climate Change (IPCC), Special Report on Emissions Scenarios (SRES) A2 and B2 scenarios. Three ensemble experiments are performed: the A2 scenario experiment with greenhouse-gas (GHG) plus sulfate aerosol forcing (referred to as A2), and the A2 and B2 scenario experiments, with GHG forcing only (A2G and B2G respectively). All experiments show that East Asian near surface temperature (T2m) and precipitation (PCP) will increase in the 21st century with larger amplitudes than global means. Seasonally varying changes are found as a larger warming in winter and fall and a stronger PCP in summer. Relative roles of large-scale and convective precipitations (LSP and CP) are analyzed extensively. A mass flux scheme with an adjustment closure is used for cumulus parameterization. In the global mean, LSP dominates total PCP increase whereas CP controls PCP reductions near the equator in December-January-February (DJF) and 30-40 degrees S in June-July-August (JJA). The latter originates from a weakening of the northern winter Hadley circulation and an increased static stability in the Southern Hemisphere, supporting previous results. For the East Asian mean, the CP change explains most of the increase of total PCP in JJA while the LSP change plays a more critical role in DJF. The LSP increase over the North Pacific in DJF is well associated with strengthened [weakened] baroclinicity north [south] of 40 degrees N, i.e., a poleward shift of storm track. Aerosol effects on East Asian climate change (A2 minus A2G patterns) are characterized by cooling and drying with patterns similar to those of the mean changes. This is inconsistent with localized features found in previous works, indicating large uncertainty in regional responses to aerosol forcing. A possible impact of GHG mitigation over the late 21st century (A2G minus B2G patterns) is more pronounced in T2m than in PCP changes, with similar patterns as in aerosol effects. Simulated CP and LSP contributions to PCP changes are insensitive to the aerosol effect as well as that of GHG mitigations.