P2.106
Impact of organized intraseasonal convective perturbations on the tropical circulation
PAPER WITHDRAWN
Hugo Bellenger, Laboratoire de Météotrologie Dynamique, Paris, France; and J. P. Duvel
Understanding processes responsible for the representation of intraseasonal convective perturbations in GCMs remains a challenge. Here, we study the role of large-scale organized convective perturbations in the triggering and the evolution of these perturbations. For this, we hypothesize that such large-scale convective perturbations can be triggered by forcing a GCM with observed intraseasonal SST anomalies. We thus compare two ensembles of simulations forced either with actual daily SST fields (high frequency, HF) or with low-pass filtered SST fields (T > 90 days; low frequency, LF). We obtain a more realistic representation of the intraseasonal variability in the HF simulations. Also, in HF simulations, there is a small increase of seasonal mean precipitation, but a strong and statistically significant increase of the seasonal mean low-level westerly flow. It is argued that it is mostly the ‘‘aggregation'' of the convection into a few large-scale organized intraseasonal events, and not the intensification of the seasonal mean precipitation, that acts to intensify the low-level westerly flow in the HF simulations. This non-linear behavior shows that a correct representation of intraseasonal variability in a GCM is required for a correct simulation of the average tropical circulation. This non-linear behavior is then further studied by inspecting the observed relation between the intraseasonal variability of the convection and the seasonal mean circulation.
Poster Session 2, Posters: Tropical Cyclone Modeling, Convection, Tropical Cyclone Structure, Intraseasonal Variability, T-PARC, TCS-08, Air-Sea Interaction, Convectively Coupled Waves, Tropical Cyclone Observations, Climate Change, Probabilistic Forecasting
Thursday, 13 May 2010, 3:30 PM-5:00 PM, Arizona Ballroom 7
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