Long-term trend and solar cycle in the middle atmosphere temperature revealed from merged HALOE and SABER datasets

Abstract The middle atmosphere temperature trend and solar cycle have been studied with long-term ground-based and satellite datasets and/or model simulations. Single satellite observations for middle atmosphere temperature are not long enough (less than 2 solar cycles) to derive long-term trend and solar cycle effects with great confidence. Using a nearly 30-year dataset merged from the Halogen Occultation Experiment (HALOE) observations between 1991 and 2005 and the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) observations between 2002 and 2019, we study the long-term trend and solar cycle in the middle atmosphere temperature between 45°S and 45°N. The cooling trend is significant below 75 km with a maximum value of ∼ -1.2 K/decade near 60–70 km in the southern hemisphere (SH) tropical and subtropical region. The SH cooling trend is larger than its counterpart in the northern hemisphere (NH). The trend derived from the SABER only dataset is ∼1.5 times smaller than that derived from the merged dataset, which is consistent with the upper stratospheric ozone recovery after 1995. The positive temperature response to the 11-year solar cycle is ∼1 K/100 solar flux units (sfu) in the upper stratosphere and lower mesosphere and increase to more than 2 K/100 sfu in the upper mesosphere of the middle latitudes. The temperature responses show clear hemispheric asymmetry with stronger responses below 70 km but weaker above in the SH than those in the NH. This is likely related to hemispheric asymmetry of wave activities induced by indirect solar radiation.