Dr. R. Saravanan
| Title | Professor |
| Research Interests | Variability and predictability of climate on seasonal to millennial timescales. Coupled ocean-atmosphere interaction. Large-scale dynamics of the atmosphere and the oceans. |
| Education | Ph. D., Princeton University (1990) |
| Office Location | Room Room 1014B, O&M Bldg |
| Office Phone | 979-845-0175 |
| Fax | 979-862-4466 |
| r.saravanan@tamu.edu | |
| Mailing Address |
Department of Atmospheric Sciences Texas A&M University 3150 TAMU College Station, TX 77843-3150 |
Research Interests
My research focuses on the mathematical and physical aspects of the climate system. Of primary interest to me are the physical mechanisms that are responsible for the climate of the Earth, in the present, in the past (paleoclimate), and in the future (climate change). This means addressing questions such as: How does the interaction between the atmosphere and the ocean affect climate? What is the global impact of El Niño? I am also interested in the statistical issues that arise in trying to quantify climate change. Can we simply blame the next big hurricane, or the next major drought on human activities? Or, should we carefully consider the statistical and physical aspects of natural climate variability before drawing such conclusions?
One of important goals of my research is to help improve predictions of climate. Surface boundary conditions play an important role in determining climate predictability. Foreknowledge of the sea surface temperature or the sea ice distribution can help predict the evolution of atmospheric flow on time scales of months to years. Currently my predictability research is focused on the tropical Atlantic sea surface temperatures and on long-term rainfall trends in the Sahel region of Africa. Listed below are some highlights of my recent research in this area.
-
Was the prolonged drought in Sahel due to deforestation? We
used a numerical model of the atmosphere and land system (created by
NASA) to address this question. Observed sea surface temperatures
during the 20th century were used as the boundary condition to carry
out numerical integrations using the model. No changes were made to
the land conditions. We found that the model could simulate the Sahel
drought even without the deforestation effect, implying that the
drought was most likely caused by changes in the oceanic conditions
(Giannini,
Saravanan, and Chang; Science, 2003; see figure below).
Figure: Indices of Sahel rainfall variability. Observations
used the average of stations between 10°N and 20°N, 20°W and
40°E. Model numbers were based on the ensemble-mean average of
gridboxes between 10°N and 20°N, 20°W and 35°E. The correlation
between observed and modeled indices of ( JAS) rainfall over 1930–2000
is 0.60. (Time series are standardized to allow for an immediate
comparison, because variability in the ensemble mean is muted in
comparison to the single observed realization. The ratio of observed
to ensemble- mean standard deviations in the Sahel is 4.)
- What is the role of air-sea interaction in tropical Atlantic predictability? Although not as well-known as El Niño, the tropical Atlantic region is perhaps one of the regions of the world which has a rather predictable climate, at least on seasonal timescales. Some of this predictive skill arises simply from the influence of the adjoining Pacific El Niño phenomenon. The remainder of the predictive skill is believed to arise from air-sea interaction that is local to the tropical Atlantic. We have carried out several studies using a hierarchy of coupled and uncoupled numerical models which show that thermodynamic air-sea interaction may play an important role in persisting sea surface temperature anomalies and make them more predictable. (Figure)
Selected Publications
Deser, C., A. Capotondi, R. Saravanan and A. Phillips, 2005: Tropical Pacific and Atlantic Climate Variability in CCSM3. Journal of Climate, submitted. (PDF)
Barreiro, M., P. Chang, L. Ji, R. Saravanan, A. Giannini, 2005: Dynamical Elements of Predicting Boreal Spring Tropical Atlantic Sea-Surface Temperatures. Dynamics of Atmospheres and Oceans, 31, 61-85. (PDF)
Barreiro, M., P. Chang, and R. Saravanan, 2005: Simulated Precipitation Response to SST Forcing and Potential Predictability in the Region of the South Atlantic Convergence Zone. Climate Dynamics, 24, 105-114. (PDF)
Giannini, A., R. Saravanan, P. Chang, 2005: Dynamics of the boreal summer African monsoon in the NSIPP1 atmospheric model. Climate Dynamics, 25, 517-535. (PDF)
Saravanan, R. and P. Chang, 2004: Thermodynamic coupling and predictability of tropical sea surface temperature. In: Earth's Climate: The Ocean-Atmosphere Interaction, Geophysical Monograph 147, American Geophysical Union, Washington, DC. C. Wang, S-P. Xie, J.A. Carton, eds. 171-180pp.
Giannini, A., Saravanan, R., Chang, P., 2004: The preconditioning role of Tropical Atlantic Variability in the development of the ENSO teleconnection: implications for the prediction of Nordeste rainfall. Climate Dynamics, 22, 839-855. (PDF)
Deser, C., G. Magnusdottir, R. Saravanan, and A. Phillips, 2004: The effects of North Atlantic SST and sea-ice anomalies on the winter circulation in CCM3: Part II: Direct and indirect components of the response. Journal of Climate, 17, 877-889. (PDF)
Magnusdottir, G., C. Deser, and R. Saravanan, 2004: The effects of North Atlantic SST and sea-ice anomalies on the winter circulation in CCM3: Part I: Main features and storm-track characteristics of the response. Journal of Climate, 17, 857-876. (PDF)
Giannini, A., R. Saravanan, and P. Chang, 2003: Oceanic forcing of Sahel rainfall on interannual to interdecadal time scales. Science, 302, 1027-1030. (PDF)
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