EFFECTS OF INITIAL FLOW ON CLOSE-IN PLANET ATMOSPHERIC CIRCULATION

Abstract

We use a general circulation model to study the three-dimensional (3-D) flow\nand temperature distributions of atmospheres on tidally synchronized extrasolar\nplanets. In this work, we focus on the sensitivity of the evolution to the\ninitial flow state, which has not received much attention in 3-D modeling\nstudies. We find that different initial states lead to markedly different\ndistributions-even under the application of strong forcing (large day-night\ntemperature difference with a short "thermal drag time") that may be\nrepresentative of close-in planets. This is in contrast with the results or\nassumptions of many published studies. In general, coherent jets and vortices\n(and their associated temperature distributions) characterize the flow, and\nthey evolve differently in time, depending on the initial condition. If the\ncoherent structures reach a quasi- stationary state, their spatial locations\nstill vary. The result underlines the fact that circulation models are\ncurrently unsuitable for making quantitative predictions (e.g., location and\nsize of a "hot spot") without better constrained, and well posed, initial\nconditions.\n