Long-term trends and solar response of the mesopause temperatures
observed by TIMED/SABER during the 2002-2019 period
Abstract
The global distribution and variations of the monthly mesopause
temperature are presented during 2002-2019 covering the latitudes of
83°S-83°N based on Sounding of the Atmosphere using Broadband Emission
Radiometry (SABER) observations. To investigate the long-term trend and
solar response of the mesopause temperature, a three-component harmonic
fit is first applied to remove the seasonal variation from the monthly
temperature data series. Then a multiple linear regression model is
performed to residual temperatures versus constant, time series, solar
activity, and geomagnetic activity terms. In this study, the mesopause
temperature shows a cooling trend through all latitudes ranging from
-0.002 to -0.113 K/year with a mean of -0.069 ± 0.036 K/year. The
cooling trends in the southern hemisphere are observed to be relatively
stronger than those in the northern hemisphere. For high latitudes
(60°– 80°), significant negative trends can be detected during the
non-summer time, while no significant trends are found for summertime.
The mesopause temperature shows apparent positive responses to solar
activity through all latitudes ranging from 2.74 to 4.76 K/100sfu with a
mean of 3.94 ± 0.59 K/100sfu, which are more significant and stable in
the northern hemisphere. There is a pronounced drop in solar response
near the equator, which could be caused by tidal forcing at low
latitudes. It is noteworthy that the length of the time interval for
analysis is the main factor influencing the quality of the results. Our
results, using an eighteen years interval, are expected to be a robust
reference for the mesopause temperature variations.