I have written up some broad background on my cloud research during the summer. I am hoping to use some of the knowledge I gained. I would also like to connect cloud processes to human activities. During the summer, we used images taken from an automated ground based camera. Continuing my research, I will use the same skills but apply them to satellite imagery which can provide a larger picture and therefore larger context.
Clouds play an important role in the climate of our atmosphere and earth, in fact clouds and aerosols “contribute the largest uncertainty to estimates and interpretations of the Earth’s changing energy budget”(Boucher IPCC AR4 573). This is because clouds reflect incoming solar radiation, and absorb and re-emit terrestrial radiation. The occurrence and composition of clouds depends on local temperature, humidity and meteorological conditions as well as aerosol content. Different cloud types have a very different net heating effect on the atmosphere and surface, therefore it is important to be able to differentiate cloud types from observations. However, systematic ground observations of cloud type were largely discontinued in the mid-1990’s. Furthermore, there is often disagreement and discontinuity between observations depending on the instrument and location of observation (Dai et al. 2006).
Despite clouds being a global phenomenon, ground based observations are only able to capture a small portion of the atmosphere. This portion is often called the soda straw view which can be extrapolated and worked into small grid scale models (Ackerman 2003). Many cloud observations in the United States are managed by the Atmospheric Radiation Measurement (ARM) program who have many research sites both stationary and mobile. In Figure 1, you can see the Southern Great Plains Site in Lamont Oklahoma with a climate model scale grid and the soda straw over the research site. Within the site are different instruments that measure cloud base height, the amount of clouds in the sky, aerosols, wind speed, humidity, and many others. Of these instruments, the instrument that most closely resembles human observers is the Total Sky Imager which takes a picture a hemispheric mirror that reflects the sky. While preliminary work has been done to threshold these images to detect clouds, little work has been done to automatically classify the images by cloud type.
Even if we had a robust record of cloud observations, we still could not answer what is happening to clouds globally. Patterns of cloud formation are very different across land and ocean as well as land formations like mountains and deserts. While it is hard to see what patterns emerge from global cloud coverage and types, work has been done to aggregate cloud data in Spain (or US) to see what patterns emerge. (Tang 2012 or Sanchez-Lorenzo 2012).
Descriptive: What are properties of clouds? What effect do clouds have on the atmosphere and vice versa? What contemporary debates are there concerning clouds and climate change?
Explanatory: Why would cloud types and cloud cover change over time? How do cloud observations factor into climate models? How are clouds changing -> scale, location, time span?
Evaluative: How good are cloud observations? How good are climate models at explaining global cloud patterns based on soda straw observations? How effective would cloud seeding be?
Works Cited
Tang, Qiuhong, and Guoyong Leng. 2012. “Changes in Cloud Cover, Precipitation, and Summer Temperature in North America from 1982 to 2009.” Journal of Climate 26 (5): 1733–44. doi:10.1175/JCLI-D-12-00225.1.
Dai, Aiguo, Thomas R. Karl, Bomin Sun, and Kevin E. Trenberth. 2006. “Recent Trends in Cloudiness over the United States: A Tale of Monitoring Inadequacies.” Bulletin of the American Meteorological Society 87 (5): 597–606. doi:10.1175/BAMS-87-5-597.
Sanchez-Lorenzo, A., J. Calbó, and M. Wild. 2012. “Increasing Cloud Cover in the 20th Century: Review and New Findings in Spain.” Clim. Past 8 (4): 1199–1212. doi:10.5194/cp-8-1199-2012.
Ackerman, Thomas P., and Gerald M. Stokes. 2003. “The Atmospheric Radiation Measurement Program.” Physics Today 56 (1): 38–44. doi:10.1063/1.1554135.
Boucher, O., D. Randall, P. Artaxo, C. Bretherton, G. Feingold, P. Forster, V.-M. Kerminen, Y. Kondo, H. Liao, U. Lohmann, P. Rasch, S.K. Satheesh, S. Sherwood, B. Stevens and X.Y. Zhang, 2013: Clouds and Aerosols. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.