Circulation anomalies associated with tropical convection during northern winter

Abstract

Lagged cross correlations between outgoing longwave radiation (OLR) and National Meteorological Center global analyses are utilized to isolate the preferred upper-level and surface circulation anomalies associated with tropical convection during northern winter. Three intraseasonal time scales are studied: 30-70, 14-30, and 6-14 days. In the 30-70-day band, the upper-level circulation signals are zonally elongated, with zonal wavenumbers 0-2 dominant. Higher-frequency signals are dominated by zonal wavenumbers 5 and 6. In the 14-30-day band, convection over the eastern hemisphere is associated with upper-level anticyclones in the subtropics and appears to be linked in some cases to midlatitude wave trains. -from Authors