Trends in the high-latitude mesosphere temperature and mesopause revealed by SABER

Abstract

The temperature trend in the mesosphere and lower-thermosphere (MLT) region can be regarded as an indicator of climate change. Using temperature profiles measured by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument during 2002–2023 and binning them based on the yaw cycle, we obtain a continuous dataset with a wide local time coverage at 50° S–80° N or 80° S–50° N. The seasonal change in temperature, caused by the forward drift in the SABER yaw cycle, is removed using the climatological temperature of the Naval Research Laboratory's Mass Spectrometer Incoherent Scatter Radar model (MSIS2.0). The corrected temperature without any waves is regarded as the mean temperature. At 50° S–50° N, the cooling trends in the mean temperature are significant in the MLT region and are in agreement with previous studies. The novel finding is that the cooling trends of ≥ l2 K per decade exhibit seasonal symmetry and reach peaks of ≥ 6 K per decade at high latitudes around the summer solstice. Moreover, there are warming trends of 1–2.5 K per decade at an altitude range of 10−2–10−3 hPa, specifically at latitudes higher than 55° N in October and December and at latitudes higher than 55° S in April and August. Over the past 22 years, the mesopause temperature (altitude) in the northern summer polar region has been ∼ 5–11 K (∼ 1 km) colder (lower) than that in the corresponding southern region. The trends in the mesopause temperature are dependent on latitudes and months, but they are negative at most latitudes and reach larger magnitudes at high latitudes. These results indicate that the temperature in the high-latitude MLT region is more sensitive to dynamic changes.