Ozone and temperature decadal solar-cycle responses, and their relation to diurnal variations in the stratosphere, mesosphere, and lower thermosphere, based on measurements from SABER on TIMED
Abstract. There is evidence that the ozone and temperature responses to the solar cycle of ~ 11 years depend on the local times of measurements. Here we present relevant results based on SABER data over a full diurnal cycle, not available previously. In this area, almost all satellite data used are made at only one or two fixed local times, which can be different among various satellites. Consequently, estimates of responses can be different depending on the specific data set. Also, over years, due to orbital drift, the local times of measurements of some satellites have also drifted. In contrast, SABER makes measurements at various local times, providing the opportunity to estimate diurnal variations over 24 hrs. We can then also estimate responses to the solar cycle over both a diurnal cycle and at the fixed local times of specific satellite data for comparison. Our results of responses, based on zonal means of SABER measurements, agree favorably with previous studies based on data from the HALOE instrument, which measured data only at sunrise and sunset, thereby supporting the analysis of both studies. We find that for ozone above ~ 40 km, zonal means reflecting specific local times (e.g., 6, 12, 18, 24 hrs) lead to different values of responses, and to different responses based on zonal means that are also averages over the 24 hours of local time, as in 3D models. For temperature, effects of diurnal variations on the responses are not negligible even at ~ 30 km and above. We also have considered the consequences of local-time variations due to orbital drifts of certain operational satellites, and for both ozone and temperature, their effects can be significant above ~ 30 km. Previous studies based other satellite data do not describe their treatment, if any, of local times. Some studies also analyzed data merged from different sources, with measurements made at different local times. Generally, the results of these studies do not agree so well among themselves. Although responses are a function of diurnal variations, this is not to say that they are the major reason for the differences, as there are likely other data-related issues. The effects due to satellite orbital drift may explain some unexpected variations in the responses, especially above 40 km.