Abstract
The migrating diurnal tide (DW1) presents a unique latitudinal structure in the stratosphere, mesosphere, and lower thermosphere. In this paper, the physical mechanisms that govern its seasonal variation are examined in these three regions using the 31.5-year (1979–2010) output from the extended Canadian Middle Atmosphere Model (eCMAM30). DW1 annual variation in the stratosphere is mainly controlled by the short-wave heating in the high latitudes, but by both the short-wave and adiabatic heating in the low latitudes. In the mesosphere, linear and nonlinear advection play important roles in the semiannual variation of the tide whereas short-wave heating does not. In the lower thermosphere, the annual variation of DW1 is mainly governed by the short-wave heating and linear advection. This study illustrates the complexity of the main physical mechanisms modulating the seasonal variations of DW1 in different regions of the atmosphere.
Highlights
Atmospheric thermal tides are dominant global-scale wave motions in the middle and upper atmosphere
The migrating diurnal tide is one of the largest atmospheric tides at the low latitudes of
The objective of this paper is to examine the role of advection and solar heating in governing the seasonal variations of DW1 in the stratosphere, mesosphere, and lower thermosphere
Summary
Atmospheric thermal tides are dominant global-scale wave motions in the middle and upper atmosphere. They can be excited by the absorption of solar radiation from tropospheric water vapor (H2 O) and stratospheric ozone (O3 ) [1,2,3], latent heat release of deep convective systems [4,5], as well as nonlinear interactions between tides and planetary waves (PWs) [6,7,8]. Tides generated in the lower atmosphere can propagate upwards and deposit their energy and momentum in the upper atmosphere through dissipation processes and induce profound effects on the ionosphere and thermosphere [15,16,17,18].
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