Trends of 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 yaw cycle, we get continuous dataset with wide local time coverage at 50° S–80° N or 80° S–50° N. The seasonal change of temperature, caused by the forward drift of SABER yaw cycle, is removed by using the climatological temperature of MSIS2.0. The corrected temperature without any waves and is regarded as the mean temperature. At 50° S–50° N, the cooling trends of 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 ≥2 K/decade exhibit seasonal symmetric and reach peaks of ≥6 K/decade at highest latitudes around the summer solstice. Moreover, there are warming trends of 1–2.5 K/decade at pressure height 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. The mesopause temperature (height) in the northern summer polar region is colder (lower) than that in the southern counterpart by ~5–11 K (~1 km) over the past 22 years. The trends of the mesopause temperature are dependent on latitudes and months. But they are negative at most latitudes and reach larger magnitudes at highest latitudes. These results indicate that the temperature in high latitude MLT region is more sensitive to dynamic changes.