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

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. Key Points The migrating DW1 tide shows semiannual variation with larger amplitudes during equinox months DE3 and DE4 tides maximize in summer, when DW1 shows less amplitude and they are generated due to latent heat release in tropical convection The SW2 shows larger amplitudes during March‐October and its seasonal variation resembles that of 10‐hPa ozone at 30–60°S