Abstract:
Anthropogenic aerosols affect the radiative balance of the Earth-atmosphere system by scattering or absorbing sunlight, by acting as cloud condensation nuclei (CCN) or ice nuclei (IN) and thus modifying the optical properties and lifetimes of clouds, and by altering the local atmospheric thermodynamic status and thus cloud formation and dissipation. To understand the detailed mechanisms and strengths of the climate impacts of anthropogenic aerosols, an interactive aerosol-climate model has been developed based on the Community Climate System Model (CCSM) of NCAR. Its aerosol module describes the size, chemical composition, as well as the mixing states of various sulfate and carbonaceous particulate matters. Modeled aerosol properties including the strength and distribution of solar particulate absorption have been compared with satellite and surface network data. Several sets of long-term integrations have also been conducted to study the climate responses to the direct radiative forcing of various types of anthropogenic aerosols. One interesting finding of the recent study suggests that the radiative forcing of anthropogenic aerosols can cause a significant change in both quantity and distribution of tropical precipitation, ranging from Pacific and Indian to Atlantic Ocean. Because this change occurs mostly in places away from any major source regions of aerosols, it must have been implemented primarily through forced changes in the large-scale circulation. These results along with some detailed features of the model will be discussed.

Abstract:
Characteristics of water vapor transport were analyzed in terms of the flux-gradient (or flux-profile) function for water vapor (Phi_q) and eddy diffusivity (K_q) in the atmospheric surface layer. Roughness length of water vapor (z_0q) over land surfaces is also analyzed. Phi_q and K_q were estimated using the CASES-99 (Cooperative Atmosphere-Surface Exchange Study-1999) filed data and z_0q was analyzed using the FLOSS-II (Fluxes Over Snow Surface-II) data. It is found that, contrary to the previous assumption of scalar similarity, water vapor is transported less efficiently than heat under unstable atmosphere while being transported comparatively or even more efficiently under stable conditions in the atmospheric surface layer. Therefore, it is revealed that the water vapor is dissimilar to the heat. The degree of discrepancy between the fluxes of water vapor and heat is dependent on the atmospheric stability. Optimally determined functions for Phi_q were provided according to atmospheric stability. It is also found that z_0q is significantly smaller than those of the previous studies over bare soil and grass surfaces. Over snow surface, z_0q agrees quite well to the one of reference functions. Modified parameterizations for kB_q^(-1)[=ln(z_0m/z_0q)] for different land surface types are found to estimate the latent heat flux more accurately. Present results suggest dissimilarity between scalars (e.g., water vapor and heat) in the atmospheric surface layer. The cause of the dissimilarity is attributed to the different magnitude of buoyancy effect of the temperature and humidity fluctuation. The differences in the scalar fluxes suggest that different parameterizations for the water vapor and the heat are required for the flux estimations (e.g., Bowen ratio energy balance method, flux-profile method) and numerical models.

Abstract:
Clouds and convection play an important role in climate and weather related issues over various spatial and time scales. Despite the efforts have been made, representing clouds, convections and their radiative and precipitating processes in numerical weather and regional/global climate models remains a challenge. To help resolve these issues, a CloudSat-centric, multi-parameter A-Train (e.g., CloudSat, Calipso, AIRS, AMSR, MODIS, CERES) and high-resolution ECMWF analyses (INTRIM and YOTC) data set is being developed to characterize dynamical, macro-/microphysical, precipitating and radiative processes associated with clouds and convection to evaluate and constraint the key relevant model physical parameters/processes in numerical models. In this presentation, results from the comparisons between cloud, convection, and precipitation statistics derived from using the above data set will be presented. The errors in the estimated radiative fluxes and heating associated with ignoring convective/precipitating ice (something commonly done in GCMs) relative to the standard CloudSat radiation product as well as results from a stand alone Fu-Liou radiative transfer model will also be discussed.

Abstract:

Abstract:

Abstract:

Abstract:

Abstract:

Abstract: