Climatology and Seasonal Variations of Temperatures and Gravity Wave Activities in the Mesopause Region Above Ft. Collins, CO (40.6°N, 105.1°W). Issue 11 (2nd June 2022)

• Record Type: Journal Article
• Authors: She, Chiao‐Yao; Yan, Zhao‐Ai; Gardner, Chester S.; Krueger, David A.; Hu, Xiong
• Is Part Of: Journal of geophysical research. Volume 127:Issue 11(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-06-02
• Subjects: climatology -- mesosphere and lower thermosphere -- temperature -- gravity wave activities -- sodium lidar; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1029/2021JD036291
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: Utilizing 956 nights of Na lidar nocturnal mesopause region temperature profiles acquired at Fort Collins, CO (40.6°N, 105.1°W) over a 20‐year period (March 1990–2010), we deduce background nightly mean temperature T ¯ ( z ) $\bar{T}(z)$ and the square of the buoyancy frequency N 2 ( z ) at 2‐km resolution between 83 and 105 km. The temperature climatology reveals the two‐level mesopause structure with clarity and sharp mesopause transitions, resulting in 102 days of summer from Days 121 to 222 of the year. The same data set analyzed at 10‐min and 1‐km resolution gives the gravity wave (GW) temperature perturbations T i '( z ) and the wave variance Var ( T ′( z )) and GW potential energy E pm ( z ) between 85 and 100 km. Seasonal averages of GW Var ( T ′( z )) and E pm ( z ) between 90 and 100 km, show that Var ( T ′) for spring and autumn are comparable and lower than for summer and winter. Due mainly to the higher background stability, or larger N 2 ( z ) in summer, E pm ( z ) between 85 and 100 km is comparable in spring, summer, and autumn seasons, but ∼30%–45% smaller than the winter values at the same altitude. The uncertainties are about 4% for winter and about 5% for the other three seasons. The values for E pm are (156.0, 176.2, 145.6, and 186.2 J/kg) at 85 km for (spring, summer, autumn, and winter) respectively, (125.4, 120.2, 115.2, and 168.7 J/kg) at 93 km, and (207.5, 180.5, 213.1, and 278.6 J/kg) at 100 km. Going up in altitude, all profiles first decrease and then increase, suggesting that climatologically, GWs break below 85 km. Key Points: With 956 nights of observations, we revisit the climatology of the background temperature and study seasonal gravity wave (GW) activities Sharp transitions are found at Days 121 and 222 between the higher radiation‐driven and the lower dynamic‐driven mesopauses at 40.6°N The winter GW potential energy is ∼40% higher than other seasons. Climatologically, their profiles suggest wave breaking below 85 km