Seasonal Variations of Low‐Latitude Migrating and Nonmigrating Diurnal and Semidiurnal Tides in TIMED‐SABER Temperature and Their Relationship With Source Variations

Abstract

Seasonal and source variations of migrating and nonmigrating tides are studied using Thermosphere‐Ionosphere‐Mesosphere Energetics and Dynamics‐Sounding of the Atmosphere using Broadband Emission Radiometry temperature data at 10°N (5–15°N) for the year 2009. The migrating DW1 shows equinoctial maximum and summer minimum at low latitudes. It shows equinoctial asymmetry with larger amplitudes during spring equinox than fall equinox. The migrating semidiurnal tidal amplitude (SW2) shows larger amplitudes (~20 K) during March–October at 30–60°S. Its seasonal variation resembles stratospheric (10 hPa) ozone variations at southern midlatitudes. During the sudden stratospheric warming of 2009, the SW1 shows larger amplitudes over the equator and it is generated due to nonlinear interaction between SW2 and planetary wave of zonal wave number 1. The eastward nonmigrating DE4 and DE3 tides enhance in summer. The DE3 and DE4 appear to be generated due to latent heat release in the troposphere, as their amplitudes in the National Center for Environmental Prediction (NCEP)'s Precipitable water vapor (proxy for latent heat release) enhance at similar times as in mesosphere. The DW2 and DW0 tides are likely to be generated due to nonlinear interaction between DW1 and planetary wave of zonal wave number 1. The SW3 enhancement during the early winter (November‐December) may be due to nonlinear interaction between DW1 and the large‐amplitude DW2. The nonlinear interactions of DW1 with planetary wave and nonmigrating tides explain the summer minimum and equinoctial asymmetry of DW1.

Climatological Westward‐Propagating Semidiurnal Tides and Their Composite Response to Sudden Stratospheric Warmings in SuperDARN and SD‐WACCM‐X

“…In April, QSPWs associated with the stratospheric final warming may again interact with SW2, whose growth recurs in Spring, to spawn SW1 and SW3. Alternatively, the non‐linear interactions between westward‐propagating diurnal tides of zonal wavenumbers 1 and 2 can theoretically lead to the seasonal climatological variation of SW3 (Sridharan, 2019), along with the changing tropospheric forcing below.…”

“…(1997), has been employed to extract climatological semidiurnal tides (e.g., Truskowski et al. (2014) and references therein) and their variations during SSW events (e.g., Sridharan, 2019). Single‐station observations can resolve the 12‐h tidal signature but, independently, cannot distinguish zonal wavenumbers.…”

Long‐Term Variability and Tendencies in Migrating Diurnal Tide From WACCM6 Simulations During 1850–2014

“…Knowledge of how natural forcings such as the solar cycle (SC), QBO, ENSO, and long-term changes in radiatively active gases (CO 2 , O 3 , CH 4 , N 2 O, chlorofluorocarbons) together affect the tidal amplitude is scarce. Although some studies have reported a link between the tidal variability and one or more of the above natural forcings (e.g., Dhadly et al, 2018;Gurubaran et al, 2005Gurubaran et al, , 2009Gurubaran & Rajaram, 1999;Hagan et al, 1999;Lieberman et al, 2007;Liu et al, 2017;Oberheide et al, 2011;Pedatella & Liu, 2012;Sridharan, 2019Sridharan, , 2020Sridharan et al, 2010;Trenberth et al, 2002;Vincent et al, 1998;Vitharana et al, 2019;Xu et al, 2009), they focus either on short periods or on a specific geographic location. Furthermore, none of these studies have looked at all of the different forcings combined.…”

Semidiurnal Tidal Influence on the Occurrence of Postmidnight F Region FAI Radar Echoes

“…They also noted the consecutive occurrence of counter electrojet events during the SSW of 2005. Sridharan (2019) observed enhancement of SW2 tide during northern hemispheric summer months and related it to similar ozone variations in the stratosphere. This could be the reason for the large occurrence of counter electrojet events during northern hemispheric summer months.…”