The Weighted Average of the Nocturnal/Diurnal Long-Term Trend of the Mesopause Temperature from 2002 to 2018

We present a long-term temperature trend of the mesopause region where the average is weighted between the diurnal and nocturnal temperature profiles using Utah State University (USU) Na lidar observation with data sets ranging from 2002 to 2018. The mesopause region is between ~80-105km in altitude, where some of the coldest atmospheric temperatures have been observed. Such cold temperatures occur due to the lack of effective absorption of solar radiation and radiative cooling of carbon dioxide. The levels of carbon dioxide have been steadily increasing throughout the atmosphere for the past few decades, and the trends in the upper atmosphere are another indication of the global climate change. Various studies have indicated cooling trend in the upper atmosphere, while the magnitude of the trend varies noticeably. In this research, a customized linear regression model fit is applied to determine the optimized parameters within the mesopause region at altitude increments of 0.5 km. At 90 km altitude, the linear trend parameter is found to be -0.06 K/Year for the nocturnal profiles and -0.07 K/Year for the weighted average nocturnal/diurnal profiles. Though it has been verified that the cooling trend continues in the past decade, the computational aspect of the study requires further analysis and comparison in the future.