Shortwave Cloud and Aerosol Radiative Forcings and Their Effects on the Vertical Local Heating/Cooling Rates

L. Akana Nguimdo, D. Njomo

Department of Electrical and Electronic Engineering, University of Buea, Buea, Cameroun..
Environmental Energy Technologies Laboratory (EETL), Faculty of Sciences, University of Yaoundé 1, Yaoundé, Cameroon.

DOI: 10.4236/acs.2013.33035                

Abstract

An analysis of atmospheric SW-radiative forcing and local heating/cooling rate is made using a one year temporal and vertical profiles of aerosol and cloud over Yaoundé (11.51°E, 3.83°N). It appears that the direct influence of aerosols on the surface compared to the TOA can be 3 times larger. Annual mean value obtained at 559 mb altitude is +27.74 W/m² with range from 0 to +43 W/m². At 904 mb, we obtained an annual mean of ﹣46.22 W/m² with range from ﹣65 to ﹣9 W/m². Frequency distribution indicates that more than 95% of ARF are between +10 and +70 W/m² at 559 mb (upper limit of UL), and more than 85% of ARF are between ﹣70 and ﹣10 W/m² at 904 mb (upper limit of PBL). This sign change is explained by the fact that the backscattering peaks at the upper limit of the aerosol PBL layer. The maximum CRF is noted at TOA where it reaches ﹣600 W/m² based on the time interval and the structure of clouds. The highest values occur between 11.50 and 13.50 LST. Clouds lead to a general heating of the entire atmospheric column with a much greater effect near the surface. Aerosols effect on the heating rate profile show strong cooling during the day for the lower atmosphere, with slight heating at the upper atmosphere. This cooling contribution generally increases from the surface and peacks at the upper boundary of aerosol layer where reflectivity is the most important. Depending on the moment of the day, average heating effect of clouds peacks at surface or within the middle troposphere due to the absorption by clouds particles. Vertical profiles deeply evolve exhibiting differences that exceed ﹣3 K/day according to altitude from one hour to another during a given mean solar day.

Keywords

Planetary Boundary Layer; Upper Layer; Clear Sky Flux; All-Sky Flux; Net Downward Flux; Radiative Forcing; Heating/Cooling Rates

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	J. Hansen, W. Rossow, B. Carlson, A. Lacis, L. Travis, A. Del Genio, I. Fung, B. Cairns, M. Mishchenko and M. Sato, “Low-Cost Long-Term Monitoring of Global Climate Forcing and Feedbacks,” Climate Change, Vol. 31, No. 2-4, 1995, pp. 247-271. doi:10.1007/BF01095149
[2]	Z. Li, “Influence of Absorbing Aerosols on the Inference of Solar Surface Radiation Budget and Cloud Absorption,” Journal of Climate, Vol. 11, 1998, pp. 5-15. doi:10.1175/1520-0442(1998)011<0005:IOAAOT>2.0.CO;2
[3]	Z. Li and A. P. Trishcenko, “Quantifying Uncertainties in Determining SW Radiative Forcing and Cloud Absorption Due to Variability in Atmospheric Conditions,” Journal of the Atmospheric Sciences, Vol. 58, 2000, pp. 376-379. doi:10.1175/1520-0469(2001)058<0376:QUIDSC>2.0.CO;2
[4]	R. D. Cess, G. L. Potter, J. P. Blanchet, G. J. Boer, S. J. Ghan, J. T. Kiehl, H. Le Treut, Z.-X. Li, X.-Z. Liang, J. F. B. Mitchell, J.-J. Morcrette, D. A. Randall, M. R. Riches, E. Roeckner, U. Schlese, A. Slingo, K. E. Taylor, W. M. Washington, R. T. Wetherald and I. Yagai, “Interpretation of Cloud-Climate Feedbacks as Produced by 14 Atmospheric General Circulation Models,” Science, Vol. 245, No. 4917, 1989, pp. 513-516. doi:10.1126/science.245.4917.513
[5]	IPCC, “Climate Change, the IPCC Scientific Assessment,” Cambridge University Press, Cambridge, 1995.
[6]	M.-D. Chou and M. J. Suarez, “A Solar Radiation Parameterization for Atmospheric Studies (CLIRAD-SW),” In: NASA Technical Memorandum, 1999, pp. 1-38.
[7]	V. Ramanathan, B. Subasilar, G. J. Zhang, W. Conant, R. D. Cess, J. T. Kiehl, H. Grassl and L. Shi, “Warm Pool Heat Budget and Shortwave Cloud Forcing: A Missing Physics,” Science, Vol. 267, No. 5197, 1995, pp. 499-503. doi:10.1126/science.267.5197.499
[8]	J. A. Coakley, R. D. Cess and F. B. Yurevich, “The Effect of Tropospheric Aerosols on the Earth’s Radiation Budget: A Parameterization for Climate Models,” Journal of Atmospheric Sciences, Vol. 40, No. 1, 1983, pp. 116-138. doi:10.1175/1520-0469(1983)040<0116:TEOTAO>2.0.CO;2
[9]	O. E. Garcia, A. M. Diaz, F. J. Exposito and J. P. Diaz, “Aerosol Radiative Forcing and Forcing Efficiency in the UVB Regions Affected by Saharan and Asian Mineral dust,” Journal of the Atmospheric Sciences, Vol. 66, No. 4, 2009, pp. 1033-1040. doi:10.1175/2008JAS2816.1
[10]	NASA, “Report of the Aerosol Interdisplinary Research Program Workshop, October 30-November 1,” NASA, Washington DC, 1996.
[11]	M. D. King, Y. J. Kaufman, W. P. Menzel and D. Tanre, “Remote Sensing of Cloud, Aerosol, and Water Vapour Properties from the Moderate Resolution Imaging Spectrometer (MODIS),” IEEE Transactions on Geoscience and Remote Sensing, Vol. 30, 1992, pp. 2-27. doi:10.1109/36.124212
[12]	G. M. McFarquhar and A. J. Heymsfield, “Parameterization of Tropical Cirrus Ice Crystal Size Distribution and Implications for Radiative Transfer: Results from CEPEX,” Journal of Atmospheric Sciences, Vol. 54, No. 17, 1997, pp. 2187-2200. doi:10.1175/1520-0469(1997)054<2187:POTCIC>2.0.CO;2
[13]	G. M. McFarquhar and S. G. Cober, “Single Scattering Properties of Mixed Phased Artic Clouds at Solar Wavelengths: Impacts on Radiative Transfer,” Journal of Climate, Vol. 17, No. 19, 2004, pp. 3799-3813. doi:10.1175/1520-0442(2004)017<3799:SPOMAC>2.0.CO;2
[14]	Y. Liu, W. Wu, M. P. Jensen and T. Toto, “Relationship between Cloud Radiative Forcing, Cloud Fraction and Cloud Albedo, and New Surface—Based Approach for Determining Cloud Albedo,” Atmospheric Chemistry and Physics, Vol. 11, No. 14, 2011, pp. 7155-7170. doi:10.5194/acp-11-7155-2011
[15]	N. L. Akana and D. Njomo, “Assessing the Aerosol Optical Thickness in Cameroon Using Ground-Based Solar radiation Measurements,” Advanced Science Letters, Vol. 3, 2010, pp. 1-7.
[16]	N. L. Akana and D. Njomo, “Profiles of Cloud Fraction and Water Content Deduced from Ground-Based Solar Radiation Measurements,” Asian Pacific Journal of Atmospheric Science, Vol. 46, No. 4, 2010, pp. 483-496.
[17]	J. T. Kiehl, J. J. Hack, G. B. Bonan, B. A. Boville, D. L. Williamson and P. J. Rasch, “The National Center for Atmospheric Research Community Climate Model: CCM3,” American Meteorological Society, Vol. 11, 1998, pp. 1131-1149.
[18]	O. E. Garcia, A. M. Diaz, F. J. Exposito and J. P. Diaz, “Shortwave Radiative Forcing and Efficiency of Key Aerosol Type Using AERONET Data,” Atmospheric Chemistry and Physics Discussions, Vol. 11, No. 12, 2011, pp. 32647-32684.
[19]	S. A. McFarlane, J. H. Mather and T. P. Ackerman, “Analysis of Tropical Radiative Heating Profile: A Comparison of Models and Observations,” Journal of Geophysical Research, Vol. 112, 2007, Article ID: D14218. doi:10.1029/2006JD008290
[20]	G. P. Anderson, J. H. Chetwynd, S. A. Clough, E. P. She1tle and F. X. Kneizys, “AFGL Atmospheric Constituent Profiles (0 120 km),” Environmental Research Paper, Vol. 954, 1986, pp. 1-46.
[21]	US Climate Change Science Program, “Atmospheric Aerosol Properties and Climate IMPACT,” Synthesis and Assessment Product 2.3.
[22]	I. N. Sokolik and O. B. Toon, “Incorporation of Mineralogical Composition into Models of the Radiative Properties of Mineral Aerosol from UV to IR Wavelengths,” Journal of Geophysical Research, Vol. 104, No. D8, 1999, pp. 9423-9444. doi:10.1029/1998JD200048
[23]	A. Smirnov, N. B. Holben, N. T. O’Neill, T. F. Eck, D. L. Westphal, A. K. Goroch, C. Pietras, O. Dubovik and I. Slutsker, “Atmospheric Aerosol Optical Properties in the Persian Gulf,” Journal of Atmospheric Sciences, Vol. 59, No. 3, 2002, pp. 620-634. doi:10.1175/1520-0469(2002)059<0620:AAOPIT>2.0.CO;2
[24]	N. Hatzianastassiou, C. Matsoukas, E. Drakakis, P. W. Stackhouse Jr., P. Koepke, A. Fotiadi, K. G. Pavlakis and I. Vardavas, “The Direct Effect of Aerosol on Solar Radiation Based on Satellite Observations, Reanalysis Datasets, and Spectral Aerosol Optical Properties from Global Aerosol Data Set (DADS),” Atmospheric Chemistry and Physics Discussions, Vol. 7, 2007, pp. 753-783. doi:10.5194/acpd-7-753-2007
[25]	L. Zhou, R. T. Pinker and I. Laszlo, “Shortwave Radiative Cloud Forcing in the Tropical Pacific Including the 1982-1983 and 1987 EL NINOs,” International Journal of Climatology, Vol. 16, No. 1, 1996, pp. 1-13. doi:10.1002/(SICI)1097-0088(199601)16:1<1::AID-JOC990>3.0.CO;2-5
[26]	T. A. Terasova and I. F. A. Cavalcanty, “Annual Cycle of Cloud Radiative Forcing over South America Simulations with CPTEC/COLA AGCM and SRB Data,” Preprints of Sixth International Conference on Southern Hemisphere Meteorology and Oceanography, AMS, Boston, 2000.
[27]	B.-J. Sohn and F. R. Robertson, “Intercomparison of Observed Cloud Radiative Forcing: A Zonal and Global Perspective,” Bulletin of the American Meteorology Society, Vol.74, No. 6, 1993, pp. 997-1006. doi:10.1175/1520-0477(1993)074<0997:IOOCRF>2.0.CO;2
[28]	D. M. Shupe, P. Zuidema and T. Uttal, “Cloud Radiative Heating Rate Forcing from Profiles of Retrieved Artic Cloud Microphysics,” Proceedings for the Twelfth ARM Science Team Meeting, St. Petersburg, 8-12 April 2002.
[29]	N. L. Akana and D. Njomo, “Spatial and Temporal Distributions of Downwelling Solar Radiation in Cameroon as Derived Using a Parameterized Solar Radiative Transfer Model in a Molecular Atmosphere,” JP Journal of Heat and Mass Transfer, Vol. 3, No. 2, 2009, pp. 73-93.
[30]	J. Su, J. Huang, Q. Fu, P. Minnis, J. Ge and J. Bi, “Estimation of Asian Dust Aerosol Effect on Cloud Radiation Forcing Using Fu-Liou Radiative Model and CERES Measurements,” Atmospheric Chemistry and Physics Discussions, Vol. 8, No. 1, 2008, pp. 2061-2084.