Seasonal gravity wave activity observed with the Equatorial Atmosphere Radar and its relation to rainfall information from the Tropical Rainfall Measuring Mission

Five years of tropospheric data below 12 km from the Equatorial Atmosphere Radar (EAR) are examined for seasonal and interannual gravity wave activity. Results are compared with data from the Tropical Rainfall Measuring Mission (TRMM) satellite. A semiannual cycle of vertical wind variances inside and above convection is found. Maxima occur at the equinoxes and minima at the solstices. This semiannual cycle is also observed in the TRMM storm height and surface rainfall. Half of the vertical wind variance above convection is due to waves with periods of less than 2 h, with the rest coming from waves with periods of less than 24 h. On average, 78% of the total horizontal wind variance above convection is due to waves with periods of less than 24 h. The TRMM rainfall at 2 km altitude is greater than the EAR surface rainfall, suggesting that the EAR site is not representative of regional rainfall conditions. Momentum fluxes are calculated and shown to be dominated by multiday processes, although standard deviations are greater than the mean values.