Hunting for Saharan air with the NOAA G-IV jet

During the 2005 Atlantic hurricane season, NOAA's Hurricane Research Division (HRD) conducted first-ever aircraft missions of its Saharan Air Layer Experiment (SALEX). A total of four SALEX missions were flown using NOAA's G-IV high altitude jet, operating out of Barbados. GPS dropwindsondes were launched during these missions to sample the Saharan Air Layer (SAL) and its interactions with Tropical Storm Irene and other areas of tropical convection. The main goals of SALEX are to better understand how the SAL's dry air, mid-level easterly jet, and suspended mineral dust affect Atlantic tropical cyclone intensity change and to improve how well the SAL is represented in forecast models such as the Global Forecast System (GFS). Specific objectives of the 2005 SALEX G-IV flights that will be discussed include:

• Sampling of the SAL with GPS dropwindsondes to determine its thermodynamic and kinematic characteristics, particularly its vertical structure and the gradients that exist along its boundaries.

• Sampling regions where the SAL was impinging on a TC or area of tropical convection to assess how effectively various satellite imagery and products [e.g. GOES-12, Meteosat-8, and the constellation of passive microwave imagers (e.g. SSM/I)] was representing the SAL.

• Including the moisture information from the SALEX GPS dropwindsondes in operational parallel runs of the NOAA GFS model and assessing the impact of this data on the GFS initial/forecast humidity fields and its forecasts of TC track and intensity.

• Perfecting G-IV sampling strategies that will be used during HRD's participation in the African Monsoon Multidisciplinary Analyses (AMMA) field campaign during the 2006 Atlantic hurricane season.