| NSF Org: |
AGS Division of Atmospheric and Geospace Sciences |
| Recipient: |
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| Initial Amendment Date: | July 5, 2012 |
| Latest Amendment Date: | July 5, 2012 |
| Award Number: | 1158984 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Eric DeWeaver
edeweave@nsf.gov (703)292-8527 AGS Division of Atmospheric and Geospace Sciences GEO Directorate for Geosciences |
| Start Date: | September 1, 2012 |
| End Date: | December 31, 2016 (Estimated) |
| Total Intended Award Amount: | $601,553.00 |
| Total Awarded Amount to Date: | $601,553.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
874 TRADITIONS WAY TALLAHASSEE FL US 32306-0001 (850)644-5260 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
FL US 32306-4520 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | Climate & Large-Scale Dynamics |
| Primary Program Source: |
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| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
This project examines the rainy seasons of East Africa, including their interannual variability and connections to rainfall variability in other parts of Africa. The region considered is roughly Tanzania, Uganda, and Kenya. Most of the rainfall in this region comes in two seasons, the "long rains" occurring between March and May, and the "short rains" during the October to December season. Of the two, the short rains account for most of the interannual rainfall variability and have much stronger connections to sea surface temperature. The project addresses a set of four general topics. First, the research will examine the causes of the general aridity of the region, which is unusual for an equatorial region. Second, the role of the Turkana jet in determining the regional precipitation climatology and the year-to-year variability of the rains will be considered. The Turkana jet is a low-level jet that flows through a narrow gap between the Ethiopian and East African highlands, and has not been extensively studied. Third, the extent to which a local intertropical convergence zone (ITCZ) is responsible for the seasonality and interannual variability of rainfall will be determined. The seasonality and variability of rainfall over much of Africa is commonly attributed to ITCZ movement, but this paradigm is problematic over East Africa. Fourth, the research will provide an examination of interannual variability of the rainy seasons, both for the short and long rains, seeking to understand the relative roles of Indian (particularly the Indian Ocean Dipole Mode), Pacific (El Nino), and Atlantic Ocean variability in determining rainfall variability, and the reasons for dipole teleconnection patterns between rainfall anomalies in East Africa and in other parts of Africa. The work would also consider the possibility that the climate of the region has changed in recent years. A novel aspect of the work is the use of a rain gauge record extending back to 1874, along with semi-quantitative precipitation time series for several regions of East Africa extending back to 1820.
The work has societal impact through its focus on the behavior of droughts and floods in East Africa, which take a heavy toll on the people of the region. The work could lead to statistical relationships between rainfall and sea surface temperature which could be useful for forecasting variations in the rainy seasons, including prolonged periods of flood and drought. In addition, the project supports two graduate students, thereby training the next generation of researchers in the field.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
This project consisted of several diverse studies related to interannual and interdecadal rainfall variability over drought-prone regions of eastern Africa. The main topics examined included the low-level Turkana Jet, seasonal drought forecasting, documentation of interannual variability, causes of interannual variability.
We updated rainfall records for Kenya, Uganda, Tanzania, Rwanda and Burundi and expanded station coverage in these countries roughly three-fold and produced a rainfall time series for the region that extends from 1874 to 2012. It is by far the longest ever published.
We completed a detailed climatology of the Turkana Jet and examined the thermodynamic factors controlling its development. This research produced evidence that this low-level jet is a major factor in creating the arid conditions that prevail over much of eastern equatorial Africa, in the pronounced year-t-year variability in the region, and in the absence of rainfall during the boreal summer.
We produced seasonal forecast models for eastern Africa for each month of the long rains season: March, April, and May. It was demonstrated that the variables important for seasonal forecasting are markedly different for each month and that forecasts are improved when individual months as opposed to the whole season are considered.
We also produced a detailed description of drought occurrence in eastern Africa during the past two decades and examined factors that produce these droughts. These were shown to be non-stationary, with the most robust being zonal winds over the equatorial Indian Ocean. Single factors were shown to be responsible for drought years, while very wet years occurred only when several factors occurred synchronously.
The P.I. also produced two articles for journals with a broad readership. One, a review of climate and rainfall variability in eastern Africa, was accepted for publication in Reviews of Geophysics. The second, documentary the inadequacy of the ITCZ paradigm for the seasonal cycle in equatorial Africa, was submitted to the Bulletin of the American Meteorological Society and accepted pending revisions.
Last Modified: 04/06/2017
Modified by: Sharon E Nicholson
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