Comparison of vertical wavelengths of gravity waves emitted by convection in the UTLS region at Koto Tabang (0.20°S, 100.32°E) and Gadanki (13.5°N, 79.2°E) using radars

Abstract

Observations of wind components and convection systems were made using suite of instruments centered on the Equatorial Atmosphere Radar (EAR) at Koto Tabang, Indonesia (0.20°S, 100.32°E) during April-May 2004 in the first Coupling Processes in Equatorial Atmosphere (CPEA) campaign. Experiments were also conducted using Indian Mesosphere Stratosphere Troposphere (MST) Radar in India at Gadanki <span style="font-family:TimesNewRoman;mso-bidi-font-family:TimesNewRoman;color:black" lang="EN-GB">(13.5°<span style="font-family: TimesNewRoman;mso-bidi-font-family:TimesNewRoman;color:black" lang="EN-GB">N, 79.2°<span style="font-family: TimesNewRoman;mso-bidi-font-family:TimesNewRoman;color:black" lang="EN-GB">E) during June 2000, which is highly convective season after the onset of south - west monsoon over southern part of India. During convective events, radar reflectivity showed the temporal evolution of convection with different vertical velocities and depth of penetration (seen from mid troposphere to upper troposphere). Observations covered several convective events that enabled to present forcing scale in the vertical direction by observing vertical wavelength (λ_z) associated with gravity wave structure and updrafts. Analysis of five convection events over Indonesian region and two convection events over Indian region revealed that λ_z of gravity waves mostly dominated in the range of 1-3 km between 10 and 20 km heights immediately after passing the convective storm over the radar sites. On the other hand, vertical wavelengths computed during formation of convective updrafts over a period of ~1 hour (typical time of storm) were about 5-8 km, which is a representative of updrafts characteristics. At both locations, λ_z increases gradually after the convection moved away from radars. Dynamics in the upper troposphere and lower stratosphere seems affected by the interaction of short λ_z(~1-3 km) gravity waves with then prevailing easterly wind. Dominant wave periods were observed in the range of 10-60 min with preference of shorter wave periods (~10-20 min) at Gadanki and longer periods (~30-50 min) at Koto Tabang possibly having a relationship with quasi-periodic behaviour of rainfall and updrafts formation patterns.<span style="font-family:TimesNewRoman; mso-bidi-font-family:TimesNewRoman" lang="EN-GB">

</span></span></span></span>