Seasonal variation of the Hough modes of the diurnal component of ozone heating evaluated from Aura Microwave Limb Sounder observations

Abstract

The global distribution of atmospheric ozone from August 2004 to December 2008 observed by Aura Microwave Limb Sounder is used to calculate the daily ozone heating rate. Comparison with a photochemical model shows that the Strobel/Zhu parameterized model of the solar heating rate gives an accurate diurnal cycle of the heating in the 10–70 km altitude range. The heating calculated using the Strobel/Zhu model is decomposed into Hough modes and the annual (AO), semiannual (SAO), and quasi‐biennial (QBO) periodicities of each Hough mode are presented. The results show that the majority of the O3 heating goes into the symmetric (1,−2), (1,1), and (1,−4) modes. The largest propagating mode (1,1) and the largest trapped mode (1,−2) have obvious SAO signatures near 47 km, where the heating magnitude is largest. The forcing of the propagating (1,1) mode by ozone heating is larger during solstices than during equinoxes. There are also AO in the (1,−2) and (1,1) modes. The QBO signatures are relatively weak in the two modes in the region of large heating rate. The heating rate of the strongest propagating mode (1,1) reaches maximum near December/January solstice; that for the strongest trapped mode (1,−2) reaches maximum near equinoxes. The strongest annual variation takes place in the (1,−1) mode; it reaches 3.6 K/d near 45 km at the December/January solstice. A new parameterization of the diurnal component of the heating rate, which covers the vertical range from 10 km to 70 km, is developed based on the seasonal variations in each Hough mode.