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 National Science
Foundation Award #0627908 |
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SGER: Significance Testing of the Role of Recurving Tropical Cyclones in Subsequent Winter Climate Modulation |
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| Investigator(s): |
Robert Hart (PI)
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| Sponsor: |
Florida State University, FL 32306 8506445260
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| Start Date/Expiration Date |
2006-06-01 to 2007-05-31 (amended 2006-05-03) |
| Awarded Amount to Date: |
$23,836 |
| Abstract: Recent preliminary research by the PI has identified a strong and intuitive relationship between the frequency of hemispheric-total recurving tropical cyclones (TCs) and the subsequent winter climate. When the total number of northern hemisphere TCs recurving north of 40 degrees latitude exceeds 12 (one standard deviation above the mean of 9), the subsequent winter is considerably less active (7-15%) baroclinically. Consequently, the midlatitudes are warmer than normal (by at least one degree Celsius for a three-month mean over January through March), and precipitation is at least 10% above normal for that three-month mean. The converse is also true for years in which the number of recurving TCs is five or less. This winter climate anomaly is caused by a reduction or enhancement, respectively, of the winter potential energy of the atmosphere induced by the earlier TC-induced heat transport. This preliminary research argues that a single recurving TC weakens the pole to equator temperature gradient by 0.5-1.5%, depending on the historical reanalysis used. With an average of nine recurving TCs per year, TCs perform 5-15% of the hemispheric heat transport, quantifying a role that has remained solely qualitative thus far.
Many critical questions are raised by these results and that is the basis for this grant: Why is the atmospheric memory of the TC impact so long (months), rather than removed within days? How do the various basins of the world contribute toward this TC heat transport? What is the critical time of autumn for recurving TCs to drive anomalous winter climate? These results suggest a unique view wherein TCs are integral to the variability and forcing of global climate, rather than incidental and solely responsive to other forcings, such as the El Nino - Southern Oscillation (ENSO). The intellectual merit of this work is to test the robustness of the preliminary results. Although an effort has been made to ensure that the recurving TCs are the forcing mechanism at work here, further examination is necessary. Is there an overriding climate forcing that is driving BOTH the recurving TC frequency and the subsequent winter climate together? Other potential overriding forcing mechanisms need to be eliminated before the recurving TCs can be claimed as the dominant forcing mechanism. The grant's goal is to eliminate, when possible, those alternative slow-manifold forcing mechanisms, such as the Madden Julian Oscillation (MJO), Quasi-biennial Oscillation (QBO), and solar cycle activity. Although the PI has established the statistical significance for the anomalous winter mean 500mb temperature flux driven by recurving TCs, statistical significance of other established anomalies will be examined: winter surface temperature and precipitation anomalies, polar and subtropical jet stream anomalies, and mean meridional circulation anomalies (Hadley, Ferrell, Polar cell anomalies).
Broader Impacts: When TC recurving frequency is known in late autumn or early winter, improved winter seasonal climate forecasts may be possible globally. Such improved forecasts would decrease the financial losses globally resulting from inefficient anticipated energy usage. Overall, the results of the preliminary research argue for a much larger role of TCs in climate forcing than is currently acknowledged. If the work to be conducted establishes the robustness of the preliminary research, a new paradigm will be set for tropical cyclone forcing of climate. |
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| NSF Org: |
ATM - Division of Atmospheric Sciences |
| Award Number: |
0627908 |
| Award Instrument: |
Standard Grant |
| Program Manager: |
Jay S. Fein
ATM Division of Atmospheric Sciences
GEO Directorate for Geosciences
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| NSF Program(s): |
CLIMATE & LARGE-SCALE DYNAMICS |
| Field Application(s): |
Other nsf.applications NEC |
| Program Reference Code(s): |
SMALL GRANTS-EXPLORATORY RSRCH, 9237
UNASSIGNED, 0000 |
| Program Element Code(s): |
5740 |
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