Atmospherice Response to

sharp SST gradients

by Justin Small

Justin is interested in the response of the atmosphere to sharp SST gradients. His previous work focused on the Equatorial Front region (Small et al 2003, JCLI, Small et al 2005 JAS) whilst his current work is on the response to the Gulf Stream. The background conditions of the atmosphere in these two regions are very different (steady trade winds vs mid-latitude storm track) yet there are some indications that the boundary layer response is similar, as seen from observations (Chelton et al 2001 JCLI, Hashizume et al 2001, JGR, Chelton et al 2004 Science, Xie 2004 BAMS).

Justin has been using a regional atmospheric model to study the effects, forced at the surface by evolving SST from AMSR-E, and at the lateral boundaries by NCEP/NCAR reanalysis. He wants to use the model to look at the response of a set of synoptic low pressure systems to the Gulf Stream. He would also like to look at interannual variability of storm track and the link to the Gulf Stream, (but that may be ambitious using a regional model).

The figure below shows how the 10 m wind speed is clearly modulated by the Gulf Stream path. These results, from the model, closely relate to those observed. Future work will analyse the deeper response, boundary layer and possibly beyond.

Regarding publications relevant to the WG, Justin suggests some related to the question ‘What is the nature of air-sea interaction in the western boundary current regions?’. Focusing on the Gulf Stream, there were a number of relevant papers in the 80s and 90s particularly on the Genesis of Atlantic Lows Experiment (GALE).

References:
Dirks et al 1988, BAMS, GALE overview
Sweet et al 1981, MWR, in situ flights over GS
Riordan and Lin 1992 MWR coastal front response to GS
Holt and Raman 1992, MWR
Wayland and Raman, 1989, BLM
Hobbs 1987 GRL, rainband over GS
Young and Sikora 2003, mwr,  clouds and boundary layer circulations over GS

Model studies:
Wai and Stage 1989 QJRMS
Huang and Raman 1988 BLM
Song et al 2007 JGR (in press)
Reed et al 1992, MWR, regional model
Doyle and Warner 1990, 1992, MWR, mesoscale modeling for GALE
Li, Y et al 2002, JGR, mesoscale modeling over GALE