Multiple Factors affecting the African Easterly Jet and Cyclogenesis over the Tropical

Atlantic

PI: W. LauCo-Is: O. Reale, A. Dasilva, K.M.Kim, and E. Wilcox

This proposal will address specific scientific issues at the “weather-climate interface” with the focus on the AEJ, and its roles in transport of Saharan Air Layer (SAL) and Saharan Airborne Dust (SAD), and their impacts on the genesis of Atlantic tropical cyclone, and the regional water cycle.

Goal To better understand the role of SAL and SAD in cyclogenesis over the tropical Atlantic, through the interaction with the African Easterly Jet, and the possible weather and climatic impacts over the Caribbean and US southeast region.

MODIS Image - March 2, 2003

Science questions

Weather focus• What is the role of the SAL in affecting the strength and evolution of the AEJ? In the formation of AEWs?• How does SAL suppress formation of tropical cyclones from AEWs? • Can better assimilation of SAL data lead to increase in skill in prediction of tropical cyclogenesis?

Climate focus• What are the roles of the AEJ and AEW in transport of SAD ?• How does SAD affect the water and energy cycles of the West Africa/Atlantic region? • What are the possible climatic impacts of SAD through large scale winds hear and SST, on TC frequency and

intensity over the Caribbean and the US southeast region ?

Proposed Research Tasks

• Task 1: Provide forecast guidance (weather forecast, cyclogensis potential, dust storm and dispersion) for the field phase of NAMMA; the forecast will provide baseline statistics for tropical cyclogeneses, of NASA operational GEOS5 model, in conjunction with MAP06 (Oreste, DaSilva, Lau)

• Task 2: Perform GEOS5 hindcasts experiments with improved initial conditions from assimilated NAMMA data and relevant satellite data (AIRS, MODIS and OMI, Cloudsat/Calipso) to study the effects of SAD and SAL on the AEJ and mechanisms of cyclogenesis modulation. (Oreste, Lau, DaSilva)

• Task 3: Conduct numerical experiments with the coupled aerosol-GEOS5 climate models to test hypotheses regarding impacts of aerosol direct forcing on water cycle and climate, and interaction with the AEJ and the West Africa monsoon climate system. (Lau, Kim, DaSilva)

• Task 4: Investigate effects of dust on CCN and IN in modifying precipitation system evolution using an aerosol-cloud microphysics parameterization in the GEOS GCM, and validation with NAMMA data. (Wilcox, Sud, Lau)

What do I need?Dust concentration, optical thickness, horizontal and vertical distribution under-flying Calipso/Cloudsat to calibrate and estimate direct effects of aerosol

Wind and moisture vertical profiles across and perpendicular to AEJ axis, to locate lateral movement of AEJ, AEW, with respect to dust transport and atmospheric heating by dust, and location of ITCZ

Cloud drop size distribution, radar echo, vertical profiles of hydrometeor and dust to estimate indirect aerosol effects on cloud and rain system evolution

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