Insolation in Titan's troposphere

Seasonality in Titan's troposphere is driven by latitudinally varying insolation. We show that the latitudinal distributions of insolation in the troposphere and at the surface, based on Huygens DISR measurements, can be approximated analytically with nonzero extinction optical depths tau, and are not equivalent to that at the top of the atmosphere (tau = 0), as has been assumed previously. This has implications for the temperature distribution and the circulation, which we explore with a simple box model. The surface temperature maximum and the upwelling arm of thermally-direct meridional circulation reach the mid-latitudes, not the poles, during summertime. (C) 2011 Elsevier Inc. All rights reserved.