Seasonal and interannual variability in atmospheric turbidity over South Africa

Aerosols affect climate by attenuating solar radiation and acting as cloud condensation nuclei. Despite their importance in the climate system, our understanding of the time-space variability of aerosols is fragmentary. Measurements and reliable estimates of atmospheric turbidity—the total column amount of aerosol—are scarce in most countries and this is especially true in the Southern Hemisphere. Very little is known about the seasonal, interannual and spatial variability of aerosols over the southern half of the globe. In this paper, we estimate monthly averaged atmospheric turbidity from surface climate data at eight locations in South Africa, regardless of cloud cover. Findings include new estimates of turbidity trends and variability over South Africa. Seasonal trends are evident at many stations, although there is no consistent trend. Over recent decades, turbidity has generally been stable at six of the eight stations. Our methodology can be applied at any location where the requisite climate data are available and, therefore, holds promise for a more complete, and possibly global, climatology of aerosols. Copyright © 2001 Royal Meteorological Society

[1]  C. Justus,et al.  Estimation of daily and monthly direct, diffuse and global solar radiation from sunshine duration measurements , 1984 .

[2]  Yoram J. Kaufman,et al.  Information on aerosol size distribution contained in solar reflected spectral radiances , 1996 .

[3]  Robert E. Davis,et al.  Statistics for the evaluation and comparison of models , 1985 .

[4]  S. Lykoudis,et al.  Estimation of the Linke and Unsworth–Monteith turbidity factors in the visible spectrum: application for Athens, Greece , 1998 .

[5]  M. Blumthaler,et al.  Measurements of the spectral aerosol optical depth using a sun photometer , 1997 .

[6]  Thomas K. Van Heuklon.  Estimating atmospheric ozone for solar radiation models , 1979 .

[7]  E. Chen,et al.  A fusion protein required for vesicle-mediated transport in both mammalian cells and yeast , 1989, Nature.

[8]  Sami D. Alaruri,et al.  Atmospheric turbidity in Kuwait , 1987 .

[9]  P. Poggi,et al.  Correlations for direct normal and global horizontal irradiation on a French Mediterranean site , 1991 .

[10]  K. Wenzel,et al.  RADIATIVE PROPERTIES OF DESERT DUST AND ITS EFFECT ON RADIATIVE BALANCE , 1999 .

[11]  G. Hidy,et al.  Aerosols and climate: Anthropogenic emissions and trends for 50 years , 1997 .

[12]  K. Sahami,et al.  Analysis of clear hour solar irradiation for seven Canadian stations , 1995 .

[13]  J. Freund.  Aerosol optical depth in the Canadian arctic , 1983 .

[14]  J. Penner,et al.  Quantifying and minimizing uncertainty of climate forcing by anthropogenic aerosols , 1994 .

[15]  R. Welch,et al.  First estimates of the radiative forcing of aerosols generated from biomass burning using satellite data , 1996 .

[16]  C. Liousse,et al.  Contribution of the different aerosol species to the aerosol mass load and optical depth over the northeastern tropical Atlantic , 1999 .

[17]  J. Deluisi,et al.  Features and effects of aerosol optical depth observed at Mauna Loa, Hawaii: 1982–1992 , 1994 .

[18]  Turbidity of the atmosphere at solar noon for Edmonton, Alberta, Canada☆ , 1977 .

[19]  J. Kiehl.  Solving the Aerosol Puzzle , 1999, Science.

[20]  J. Adedokun,et al.  Spectral solar radiation measurements and turbidity: Comparative studies within a tropical and a sub-arctic environment , 1997 .

[21]  N. O'Neill,et al.  Measurement of aerosol optical depth in the Pacific Ocean and the North Atlantic , 1994 .

[22]  Larry L. Stowe,et al.  Characterization of tropospheric aerosols over the oceans with the NOAA advanced very high resolution radiometer optical thickness operational product , 1997 .

[23]  T. Wigley,et al.  Implications for climate and sea level of revised IPCC emissions scenarios , 1992, Nature.

[24]  J. Garrison,et al.  Critical evaluation of precipitable water and atmospheric turbidity in Canada using measured hourly solar irradiance , 1998 .

[25]  P. Kassomenos,et al.  Estimates of effective aerosol optical depths from spectral solar radiation measurements , 1996 .

[26]  M. Chendo,et al.  Atmospheric turbidity and the diffuse irradiance in Lagos, Nigeria , 1997 .

[27]  H. Power.  Estimating atmospheric turbidity from climate data , 2001 .

[28]  S. Pashiardis,et al.  Recent measurements of broad-band turbidity parameters in the island of Cyprus , 1996 .

[29]  J. Davies,et al.  Turbidity in Eastern Canada , 1983 .

[30]  Philip B. Russell,et al.  Aerosol optical depth retrieval using ATSR-2 and AVHRR data during TARFOX , 1999 .

[31]  M. Wendisch,et al.  Measurements of the optical depth and retrieval of aerosol parametersin the polar regions , 1991 .

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

[33]  C. Gueymard.  Analysis of monthly average atmospheric precipitable water and turbidity in Canada and Northern United States , 1994 .

[34]  J. Peterson,et al.  Interactions between air pollution and solar radiation , 1977 .

[35]  T. Wigley,et al.  Possible climate change due to SO2-derived cloud condensation nuclei , 1989, Nature.

[36]  A. Smirnov,et al.  AERONET-a federated instrument network and data archive for aerosol Characterization , 1998 .

[37]  A. Louche,et al.  Determination of Ångström's turbidity coefficient from direct total solar irradiance measurements , 1987 .

[38]  A. Karnieli,et al.  Aerosol optical depths in a semiarid region , 1997 .

[39]  Glenn E. Shaw,et al.  Atmospheric Turbidity in the Polar Regions. , 1982 .

[40]  Gerrit de Leeuw,et al.  A new algorithm to determine the spectral aerosol optical depth from satellite radiometer measurements , 1998 .

[41]  H. Nfaoui,et al.  Estimation of daily and monthly direct, diffuse and global solar radiation in Rabat (Morocco) , 1993 .

[42]  Christine A. O'Neill,et al.  Effects of Aerosol from Biomass Burning on the Global Radiation Budget , 1992, Science.

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

[44]  L. Thomason,et al.  Volcanic perturbation of the atmosphere in both polar regions: 1991–1994 , 1996 .

[45]  Philip B. Russell,et al.  Aerosol properties and radiative effects in the United States East Coast haze plume: An overview of the Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX) , 1999 .

[46]  C. Gueymard.  Mathermatically integrable parameterization of clear-sky beam and global irradiances and its use in daily irradiation applications , 1993 .

[47]  T. Eck,et al.  Effect of dry‐season biomass burning on Amazon basin aerosol concentrations and optical properties, 1992–1994 , 1996 .