ABSTRACT
The spatial pattern of precipitation responses to CO2 concentration increases significantly influences global weather and climate variability by altering the location of tropical heating in a warmer climate. In this study, we analyze the Coupled Model Intercomparison Project Phase 5 (CMIP5) climate model projections of tropical Pacific rainfall response to quadrupled increase of CO2. We found that the precipitation changes to the CO2 concentration increase cannot be interpreted by a weakening or strengthening of large-scale east-west coupling across the tropical Pacific basin, i.e., Walker circulation. By calculating the water vapor transport, we suggest instead that different responses of the Walker and Hadley circulations to the increasing CO2 concentration shape the details of the spatial pattern of precipitation in the tropical Pacific. Therefore, more regionally perturbed circulations over the tropical Pacific, which is influenced by the mean state change in the tropical Pacific and the enhanced precipitation outside the tropical Pacific, lead to greater increases in precipitation in the western equatorial Pacific as compared to the eastern tropical Pacific in a warmer climate.
ABSTRACT
The radiative properties of atmospheric aerosols are determined by their masses, chemical characteristics, and optical properties, such as aerosol optical depth (AOD), Angström parameter (alpha) and single scattering albedo (SSA). In particular, the aerosol optical properties determine the surface temperature perturbation that may give some information in understanding regional atmospheric radiative forcing. To understand the radiative forcing and regional source of an aerosol, the present study focused on the analysis of the aerosol optical properties based on two different observations in the spring season, during the special Asian dust storm period. The Korean Global Atmosphere Watch Observatory (KGAWO), at Anmyeon Island, and the ACE-Asia super-site, at Gosan, Jeju Island, have measured radiations and aerosols since 2000. The sites are located in the mid-west and south of the Korean peninsula, which are strongly affected by the Asian dust coming from China every spring. The aerosol optical properties, measured by ground-based sun and sky radiometers, over both sites were analyzed to gain an understanding of the radiation and climate properties. The probability distributions of the aerosol optical depths were rather narrow, with a modal value of approximately 0.38 at both sites during 2001 and 2002. The Angström parameter frequency distributions showed two peaks at Anmyeon GAW, but only one peak at the Jeju ACE-Asia super site. One peak, around 0.63, characterizes the situation of a day having Asian dust, the second peak, around 1.13, corresponded to the relatively dust-free cases. The correlation between the aerosol optical depth and the Angström exponents resulted in a wide range of the Angström parameter, alpha, over a wide range of optical depths at Anmyeon, whereas a narrow range of alpha, with moderate to low values for the AOD at Jeju. Under dust free conditions the single scattering albedo (SSA) decreased with wavelength, while in the presence of Asian dust, the SSA either stayed neutral, or increased slightly with wavelength at Anmyeon, and showed higher value than Jeju. The change in the surface temperature was highly correlated with increases in the aerosol optical depth at Anmyeon to a greater extent than at Jeju.
