Remote Sensing Observations of Clouds

Clouds are an important component of the Earth’s climate system. They also provide mediums for aqueous and heterogeneous oxidation processes to occur in the atmosphere. Accumulation of greenhouse gases (GHGs) and aerosol particles in the Earth’s atmosphere can change cloud cover through a number of different feedback mechanisms. We plan to use AVHRR (Advanced Very High Resolution Radiometer) cloud imagery data to determine how cloud cover has changed over the last two decades over select regions of the globe. In the stratosphere (top image) cloud cover changes can delay the recovery of the ozone layer. In the troposphere (bottom image) cloud cover changes can affect surface temperatures, wind patterns and rainfall.

 

High Cloud Cover Changes in the Arctic: These AVHRR images show the changes in the wintertime polar stratospheric cloud cover for two select years (1980 on top and 2000 on bottom). This project will involve analyzing data over the last 25 years to extract an observational trend in high polar stratospheric cloud cover. Clouds that form high up in the atmosphere aren’t influenced by surface feedbacks, and therefore, documenting decadal changes in their trends can provide solid evidence for global climate change at high altitudes, which are mainly driven by GHG forcing (GHGs warm the surface climate but they cool the climate of the upper atmosphere).

 

 

Greenland Cloud Cover Changes:This project will explore how changes in cloud cover, induced by greenhouse gas emissions, can affect the surface climate variables such as temperature and wind direction. Both factors play important roles in determining the ice balance of the Earth system. For example, Greenland (or other ice bodies) ice sheet melt regions are growing with time (image from the recent Arctic Climate Impact Assessment report). We plan to use the AVHRR cloud imaginary data over Greenland to explore how changes in cloud cover overhead may influence the rate of ice melting by inducing changes in temperature and wind direction near the surface.

 

 

 

 

Marine particles and Coastal Climate: Marine aerosols, lofted from the sea surface by wind activity, serve as cloud condensation nuclei for marine clouds. Some recent studies indicate that dumping of agricultural waste, sewage leakage, and deposition of air pollution can trigger chlorophyll blooming near coastal regions, contaminating the ocean surface with organic matter (i.e. Beman et al., Nature, 2005). In this project we plan to explore whether observed changes in the ocean albedo (or chlorophyll content of seawater) seen by the SeaWIFS instrument (image above) can lead to a measurable impacts on marine cloud cover using the AVHRR cloud imaginary data. Changes in marine cloud cover can directly impactprecipitation patterns and subequetly access to water supplies alongside coastal areas. This project will involve collaborations with Kevin Arrigo in the Department of Geophysics.

 

Relevant References

Tabazadeh, A., K. Drdla, M. R. Schoeberl, P. Hamill, and O. B. Toon., Arctic "ozone hole" in a cold volcanic stratosphere, Proc. Natl. Acad. Sci.,99, 2609, 2002. (Cover Story)

Tabazadeh, A., E. J. Jensen, O. B. Toon. K. Drdla and M. R. Schoeberl, Role of the stratospheric polar freezing belt in denitrification, Science, 291, 2591, 2001. (Research Report)

Tabazadeh, A., M. L. Santee, M. Y. Danilin, H. C. Pumphrey, P. A. Newman, P. J. Hamill, and L. Mergenthaler, Quantifying denitrification and its effect on ozone recovery, Science,288, 1407, 2000. (AAAS issued a press release on this article)

Pagan. K. L., A. Tabazadeh, K. Drdla, M. E. Hervig, S. D. Eckerman, E. V. Browell, M. J. Legg, and P. G. Foshi, Observational evidence against lee wave generation of NAT clouds in early December 1999 within the Artic vortex, J. Geophys. Res., 109, D04312. doi: 10/1029/2003JD003846, 2004.

Irie, H., K. L. Pagan, A. Tabazadeh, M.J. Legg and T. Sugita, Investigation of polar stratospheric cloud solid particle formation mechanisims using ILAS and AVHRR observations in the Arctic, Geophys. Res. Lett., 31, doi: 10.1029/2004GL020246, 2004.

Santee, M. L., A. Tabazadeh, G. L. Manney, M. D. Fromm, R. M. Bevilacqua, and N. J. Livesey, Inferring PSC composition in the Arctic from UARS MLS HNO3 and POAM II aerosol extinction measurements, J. Geophys. Res., 107(D10), 10.1029/2000JD000227, 2002.

Stone, E. M., A. Tabazadeh, E. J. Jensen, H. C. Pumphery, M. L. Santee, and J. L. Mergenthaler, Onset, extent, and duration of dehydration in the southern hemisphere polar vortex, J. Geophys. Res., 106, 22,979, 2001.

Danilin, M. Y., M. L. Santee, J. M. Rodriquez, M. K. W. Ko, J. M. Mergenthaler, J. B. Kumer and A. Tabazadeh, and N. J. Livesey, Trajectory hunting: A case study of rapid chlorine activation in December 1992 as seen by UARS, J. Geophys. Res., 105, 4003, 2000.

Santee, M. L., A. Tabazadeh, G. L. Manney, R. J. Salawitch, L. Froidevaux, W. G. Read, and J. W. Waters, UARS MLS HNO3 observations: Implications for Antarctic PSCs, J. Geophys. Res., 103, 13,285, 1998.

Massie, S., M. Santee, W. Read, J. Dye., W. Randel, X. Tie, F. Wu, and G. Brasseur, A. Tabazadeh, Simultaneous observations of polar stratospheric clouds and HNO3 over Scandinavia in January, 1992, Geophys. Res. Lett., 24, 595, 1997.