Saharan Air Layer

Principle Investigator : Jason Dunion (UM-CIMAS/HRD)

SeaWiFS/NASA/GSFC

Team Members:

Sim Aberson (HRD)
Bill Barry (HRD)
Mike Black (HRD)
Neal Dorst (HRD)
Steve Feuer (HRD)
Jeff Hawkins (NRL)
John Kaplan (HRD)
Chris Landsea (HRD)
Paul Leighton (HRD)
Frank Marks (HRD)
Mark Powell (HRD)
Joseph Prospero (UM/CIMAS)
Rob Rogers (UM-CIMAS/HRD)
Chris Velden (UW/CIMSS)

Objectives:
Improve our understanding of the mechanisms by which the Saharan Air Layer’s (SAL’s) embedded mineral dust, low humidity, and low-level wind surge affect Atlantic tropical cyclone genesis and intensity change.

improve the representation of dry air in forecast models
investigate how the SAL interacts with the tropical cyclone inner core
improve our understanding of the SAL’s vertical structure
investigate the effect of mineral dust on cloud microphysics
improve the representation of vertical wind shear that is enhanced by the SAL surge
investigate the mechanisms that lead to strong SAL outbreaks over Africa
investigate the mechanisms by which the SAL maintains its thermodynamic structure

Methods:

conduct the SALEX experiment as described in the HRD hurricane field program (HFP)
SAL monitoring: GOES, MSG, SSM/I, AMSU, Terra, and Aqua satellites
SAL sampling: GPS dropsondes, LASE DIAL LIDAR (aerosol & moisture)
Data processing: GPS processing software, new code development to automate the ability to look at specific SAL characteristics (humidity/temperature/winds)

Accomplishments:

automated geostationary satellite imagery was developed to track the SAL continuously and is available in real-time
SALEX was added to the HRD HFP beginning in 2002
Four SALEX missions flown during 2005 HFP

References:
Dunion, J.P., and C.S. Velden, 2003: The impact of the Saharan Air Layer on Atlantic tropical cyclone activity. Bull. Amer. Meteor. Soc., (Submitted).

Dunion, J.P., and C.S. Velden, 2003: The Impact of the Saharan Air Layer on Atlantic tropical cyclones. 57^th Annual Interdepartmental Hurricane Conference. Miami, FL, Office of Fed. Coord. For Meteor. Services and Supporting Research, NOAA.

Future Work:

develop alternative satellite tools to replace GOES-8 coverage beyond 2002
develop a new Jordan sounding (SAL versus non-SAL)
investigate the impact of humidity data on TC track and intensity model forecasts
examine how effectively global models are capturing the SAL’s low humidity
develop an improved humidity parameter for use in SHIPS

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Last modified: 1/24/2006

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