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

Abstract

[1] 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.

Temporal and spatial distributions of atmospheric wave energy in the equatorial stratosphere revealed by GPS radio occultation temperature data obtained with the CHAMP satellite during 2001–2006

“…2 was suppressed in 2002/2003 and 2004/2005, which seem to be a result of the wave-mean flow interaction with the QBO, as reported by de la Torre et al (2006), who also used CHAMP GPS RO data. A comparable interaction was also reported by Sato and Dunkerton (1997) using routine radiosonde soundings at Singapore.…”

“…In DJF, the centers are north-east of Papua New Guinea and between Borneo and Sumatra islands; in MAM, however, the entire pattern seems to be slightly shifted south-westward so that enhanced E p is east of Borneo and west of Sumatra. Alexander et al (2008) analyzed the seasonal variations of gravity wave activity using tropospheric wind data collected with equatorial atmosphere radar (EAR) at Koto Ta- of E p from the zonal mean is also averaged for 5 years (right). From top to bottom, the panels show the results every 3 months in June-July-August, September-October-November, December-January-February, and March-April-May, respectively.…”

“…The long-term behavior of temperature variance was studied by using CHAMP GPS RO data during a 5-year period from May 2001 to April 2006 (de la Torre et al, 2006). These researchers reported the latitude, height, and time variations of stratospheric wave activity with vertical wave lengths shorter than 10 km, but they did not discuss any horizontal variations, as the variance was averaged zonally.…”

A remarkable correlation between short period gravity waves and semiannual oscillation of the zonal wind in the equatorial mesopause region

“…Although the GW variance alone cannot tell whether wave-mean flow interaction is taking place or not (which requires divergence of momentum flux), here we try to understand what causes such a good correlation between the two, considering that the GWs are contributing to the MSAO. Alexander et al (2008) have shown that the GW variance in the troposphere has a seasonal variation, with the variance being more during equinoxes and less during solstices. Thus, more GWs are generated during equinoxes and less during solstices.…”

Diurnal variation of short-period (20–120 min) gravity waves in the equatorial Mesosphere and Lower Thermosphere and its relation to deep tropical convection

“…Dutta et al, 2009;Alexander et al, 2008b) and in the MLT region (e.g. Kovalam et al, 2006;Taylor et al, 2009).…”