The seasonal cycle of atmospheric heating and temperature

4 The seasonal cycle of the heating of the atmosphere is divided into a component due to direct 5 solar absorption in the atmosphere, and a component due to the flux of energy from the 6 surface to the atmosphere via latent, sensible, and radiative heat fluxes. Both observations 7 and coupled climate models are analyzed. The vast majority of the seasonal heating of the 8 Northern extratropics (78% in the observations and 67% in the model average) is due to 9 atmospheric shortwave absorption. In the southern extratropics, the seasonal heating of the 10 atmosphere is entirely due to atmospheric shortwave absorption in both the observations and 11 the models, and the surface heat flux opposes the seasonal heating of the atmosphere. The 12 seasonal cycle of atmospheric temperature is surface amplified in the northern extratropics 13 and nearly barotropic in the southern hemisphere; in both cases, the vertical profile of 14 temperature reflects the source of the seasonal heating. 15 In the northern extratropics, the seasonal cycle of atmospheric heating over land differs 16 markedly from that over the ocean. Over the land, the surface energy fluxes compliment the 17 driving absorbed shortwave flux; over the ocean they oppose the absorbed shortwave flux. 18 This gives rise to large seasonal differences in the temperature of the atmosphere over land 19 and ocean. Downgradient temperature advection by the mean westerly winds damps the 20 seasonal cycle of heating of the atmosphere over the land and amplifies it over the ocean. 21 The seasonal cycle in the zonal energy transport is 4.1 PW. 22 Finally, we examine the change in the seasonal cycle of atmospheric heating in 11 CMIP3 23 models due to a doubling of atmospheric carbon dioxide from pre-industrial concentrations. 24 We find the seasonal heating of the troposphere is everywhere enhanced by increased short25 wave absorption by water vapor; it is reduced where sea ice has been replaced by ocean which 26