Abstract
Abstract. Analyses of hourly radiosonde data of temperature, wind, and relative humidity during four days (two with convection and two with no convection) as a part of an intensive observation period in CPEA-2 campaign over Koto Tabang (100.32° E, 0.20° S), Indonesia, are presented. Characteristics of gravity waves in terms of dominant wave frequencies at different heights and their vertical wavelengths are shown in the lower stratosphere during a convective and non-convective period. Gravity waves with periods ~10 h and ~4–5 h were found dominant near tropopause (a region of high stability) on all days of observation. Vertical propagation of gravity waves were seen modified near heights of the three identified strong wind shears (at ~16, 20, and 25 km heights) due to wave-mean flow interaction. Between 17 and 21 km heights, meridional wind fluctuations dominated over zonal wind, whereas from 22 to 30 km heights, wave fluctuations with periods ~3–5 h and ~8–10 h in zonal wind and temperature were highly associated, suggesting zonal orientation of wave propagation. Gravity waves from tropopause region to 30 km heights were analyzed. In general, vertical wavelength of 2–5 km dominated in all the mean-removed (~ weekly mean) wind and temperature hourly profiles. Computed vertical wavelength spectra are similar, in most of the cases, to the source spectra (1–16 km height) except that of zonal wind spectra, which is broad during active convection. Interestingly, during and after convection, gravity waves with short vertical wavelength (~2 km) and short period (~2–3 h) emerged, which were confined in the close vicinity of tropopause, and were not identified on non-convective days, suggesting convection to be the source for them. Some wave features near strong wind shear (at 25 km height) were also observed with short vertical wavelengths in both convective and non-convective days, suggesting wind shear to be the sole cause of generation and seemingly not associated with deep convection below. A drop in the temperature up to ~4–5 K (after removal of diurnal component) was observed at ~16 km height near a strong wind shear (~45–55 m s−1 km−1) during active period of convection.
Highlights
The active cumulus convection in the equatorial region is the source of many unique atmospheric processes that couple the Earth’s atmosphere from bottom to top and from equator to poles
We focused on the characteristics of short period gravity waves (GWs) with time periods of 2–10 h in the UTLS region
An attempt has been made to present the general characteristics of the emerged wave system in terms of vertical wavelengths and prominent wave frequencies, and the vertical structure of the convective system during an intensive observation period, by launching hourly radiosonde and radars data under Coupling Processes in the Equatorial Atmosphere (CPEA)-II campaign
Summary
The active cumulus convection in the equatorial region is the source of many unique atmospheric processes that couple the Earth’s atmosphere from bottom to top and from equator to poles. Owing to the minimal Coriolis effect present in the equatorial region, a wide range of atmospheric waves in time and space are generated, which propagate upward and interact with the background mean flow. The Indonesian region, located in the equatorial belt, is known for its most active and strong convective activities where the vertical coupling takes place most conspicuously. The diurnal strong localized convection activities modulate the ambient atmospheric conditions in the troposphere and lower stratosphere (UTLS) region. Short period gravity waves (with a period range of a few minutes to a few hours) had been reported directly above convection using radar data (Dhaka et al, 2005, 2006, 2007b).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
