Is midlatitude convection an active or a passive player in producing global circulation patterns?

Citation
Dj. Stensrud et Jl. Anderson, Is midlatitude convection an active or a passive player in producing global circulation patterns?, J CLIMATE, 14(10), 2001, pp. 2222-2237
Citations number
43
Categorie Soggetti
Earth Sciences
Journal title
JOURNAL OF CLIMATE
ISSN journal
08948755 → ACNP
Volume
14
Issue
10
Year of publication
2001
Pages
2222 - 2237
Database
ISI
SICI code
0894-8755(2001)14:10<2222:IMCAAO>2.0.ZU;2-Q
Abstract
The ability of persistent midlatitude convective regions to influence hemis pheric circulation patterns during the Northern Hemisphere summer is invest igated. Global rainfall data over a 15-yr period indicate anomalously large July total rainfalls occurred over mesoscale-sized, midlatitude regions of North America and/or Southeast Asia during the years of 1987, 1991, 1992, and 1993. The anomalous 200-hPa vorticity patterns for these same years are suggestive of Rossby wave trains emanating from the regions of anomalous r ainfall in the midlatitudes. Results from an analysis of an 11-yr mean monthly 200-hPa July wind field i ndicate that, in the climatological mean, Rossby waveguides are present tha t could assist in developing a large-scale response from mesoscale-sized re gions of persistent convection in the midlatitudes. This hypothesis is test ed using a barotropic model linearized about the 200-hPa July time-mean flo w and forced by the observed divergence anomalies. The model results are in qualitative agreement in the observed July vorticity anomalies for the fou r years investigated. Model results forced by observed tropical forcings fo r the same years do not demonstrate any significant influence on the midlat itude circulation. It is argued that persistent midlatitude convective regi ons may play a role in the development, maintenance, and dissipation of the large-scale circulations that help to support the convective regions.