A study of the direct and indirect effects of aerosols using global satellite data sets of aerosol and cloud parameters

[1] The present study investigated the correlations between aerosol and cloud parameters derived from satellite remote sensing for evaluating the radiative forcing of the aerosol indirect effect. The global statistics showed that the effective particle radius and the optical thickness of low clouds correlate well with the column number concentration of the aerosol particles, indicating an aerosol indirect effect. A correlation of the cloud fraction with the aerosol number was also seen, whereas we could not find a significant correlation of the cloud-top temperature with the column aerosol number. Furthermore, the regional statistics presented that positive correlations between the cloud optical thickness and cloud fraction with the aerosol column number concentration exist in most regions consistent with the global mean statistics. However, the effective cloud particle radius showed a tendency similar to the global correlation only around the seashore regions. Using these correlations and assuming that the aerosol column number concentration has increased by 30% from the preindustrial era, the total radiative forcing of the aerosol indirect effect was evaluated to be about −0.6 to −1.2 W m−2. The radiative forcing of the aerosol direct effect from the satellite-retrieved parameters was also evaluated as −0.4 W m−2 over the ocean. The cloud-top temperature was found to be insensitive to the change in the aerosol number, although there was a distinct negative correlation between the aerosol number and cloud temperature at which the cloud particle grows to a radius of 14 μm. This particular dependency of the cloud temperature suggests that aerosols acts on clouds so as to change cloud particle size near the cloud top, optical thickness, and fraction but to keep their cloud-top temperature without causing a significant longwave radiative forcing.

[1]  S. Klein,et al.  The Seasonal Cycle of Low Stratiform Clouds , 1993 .

[2]  Sonoyo Mukai,et al.  Algorithm description of system flow for global aerosol distribution , 2000, Appl. Math. Comput..

[3]  T. Nakajima,et al.  Wide-Area Determination of Cloud Microphysical Properties from NOAA AVHRR Measurements for FIRE and ASTEX Regions , 1995 .

[4]  Alexander Khain,et al.  The Role of Sea Spray in Cleansing Air Pollution over Ocean via Cloud Processes , 2002, Science.

[5]  Olivier Boucher,et al.  The sulfate‐CCN‐cloud albedo effect , 1995 .

[6]  S. Twomey.  Pollution and the Planetary Albedo , 1974 .

[7]  W. Rossow,et al.  Advances in understanding clouds from ISCCP , 1999 .

[8]  Itamar M. Lensky,et al.  Satellite-Based Insights into Precipitation Formation Processes in Continental and Maritime Convective Clouds , 1998 .

[9]  Teruyuki Nakajima,et al.  Development of a Two-Channel Aerosol Retrieval Algorithm on a Global Scale Using NOAA AVHRR , 1999 .

[10]  Teruyuki Nakajima,et al.  A Global Determination of Cloud Microphysics with AVHRR Remote Sensing , 2001 .

[11]  Teruyuki Nakajima,et al.  A possible correlation between satellite‐derived cloud and aerosol microphysical parameters , 2001 .

[12]  T. L. Wolfe,et al.  An assessment of the impact of pollution on global cloud albedo , 1984 .

[13]  Yoram J. Kaufman,et al.  Effect of Amazon smoke on cloud microphysics and albedo - analysis from satellite imagery , 1993 .

[14]  R. Pincus,et al.  Effect of precipitation on the albedo susceptibility of clouds in the marine boundary layer , 1994, Nature.

[15]  D. W. Johnson,et al.  The Measurement and Parameterization of Effective Radius of Droplets in Warm Stratocumulus Clouds , 1994 .

[16]  V. Ramanathan,et al.  Reduction of tropical cloudiness by soot , 2000, Science.

[17]  Sonoyo Mukai,et al.  Combined use of OCTS and POLDER for cloud retrieval , 2002 .

[18]  Y. Kaufman,et al.  The effect of smoke particles on clouds and climate forcing , 1997 .

[19]  B. Holben,et al.  Single-Scattering Albedo and Radiative Forcing of Various Aerosol Species with a Global Three-Dimensional Model , 2002 .

[20]  D. L. Roberts,et al.  A climate model study of indirect radiative forcing by anthropogenic sulphate aerosols , 1994, Nature.

[21]  V. Ramanathan,et al.  Aerosols, Climate, and the Hydrological Cycle , 2001, Science.

[22]  B. Albrecht.  Aerosols, Cloud Microphysics, and Fractional Cloudiness , 1989, Science.

[23]  R. Welch,et al.  Global Survey of the Relationships of Cloud Albedo and Liquid Water Path with Droplet Size Using ISCCP , 1998 .

[24]  George A. Isaac,et al.  The relationship between cloud droplet number concentrations and anthropogenic pollution : observations and climatic implications , 1992 .

[25]  Garik Gutman,et al.  Retrieving microphysical properties near the tops of potential rain clouds by multispectral analysis of AVHRR data , 1994 .

[26]  Y. Tsushima,et al.  Modeling of the radiative process in an atmospheric general circulation model. , 2000, Applied optics.

[27]  Joyce E. Penner,et al.  Indirect effect of sulfate and carbonaceous aerosols: A mechanistic treatment , 2000 .

[28]  J. Coakley,et al.  Climate Forcing by Anthropogenic Aerosols , 1992, Science.

[29]  Sonoyo Mukai,et al.  Retrieval algorithm for atmospheric aerosols based on multi-angle viewing of ADEOS/POLDER , 1999 .

[30]  Melanie A. Wetzel,et al.  Satellite‐observed patterns in stratus microphysics, aerosol optical thickness, and shortwave radiative forcing , 1999 .

[31]  Rosenfeld,et al.  Suppression of rain and snow by urban and industrial air pollution , 2000, Science.

[32]  T. C. Johns,et al.  A search for human influences on the thermal structure of the atmosphere , 1995, Nature.

[33]  Alexander Smirnov,et al.  A Study of Global Aerosol Optical Climatology with Two-Channel AVHRR Remote Sensing , 2000 .

[34]  Yoram J. Kaufman,et al.  Fossil fuel and biomass burning effect on climate - Heating or cooling? , 1991 .

[35]  U. Lohmann,et al.  Impact of sulfate aerosols on albedo and lifetime of clouds: A sensitivity study with the ECHAM4 GCM , 1997 .

[36]  J. Hansen,et al.  Radiative forcing and climate response , 1997 .

[37]  A. Slingo,et al.  Predicting cloud‐droplet effective radius and indirect sulphate aerosol forcing using a general circulation model , 1996 .