Wave Characteristics

by Acsrinivasan
(India)

Original Text: Wave Characteristics


In the current work we have studied source mechanisms of the Convectively generated Gravity Waves (CGWs) through continuous observations of MST Radar, ERA-Interim Reanalysis, NCEP OLR and MTSAT-1R TBB datasets during the convection events due to the passage of thunderstorm and squall-line over Gadanki during 27-30 September 2004. The waves generated due to latent heat release and their vertical wavelengths calculated using winds and temperature; Brunt-Vaisala frequency from temperature profiles for the entire period show the thermal forcing mechanism. Short period Gravity Waves (GWs) observed using wavelet analysis shows the mechanical oscillator mechanism and different periodicities during initial, mature and dissipative phases of convection. Transient mountain effect is noticed as a dominant source mechanism for the present case with strong updrafts and downdrafts from the radar vertical winds (even in isentropes) with strong easterly wind shear and wave-breaking phenomenon was noticed during the squall-line passage which are due to the existence of mesoscale convective systems as noticed from the NCEP OLR. Apparent downward phase propagation is observed in temperature and meridional wind perturbations, zonal wind and horizontal wind shear reveals the easterly phase of the QBO. The energy-propagation during the period of observation was mostly upwards as the momentum flux above the storm height was negative even there is positive shear zone above the storm level for the entire period of study, and showing significant contribution for the transport of momentum and energy through gravity waves to the middle and upper atmosphere.

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Revised Text:

In the current work we have studied source mechanisms of the Convectively generated Gravity Waves (CGWs) through continuous observations of MST Radar, ERA-Interim Reanalysis, NCEP OLR and MTSAT-1R TBB data-sets during the convection events resulting from the passage of thunderstorms and squall-lines over Gadanki during 27-30 September 2004. The waves were generated due to latent heat release and their vertical wavelengths calculated using winds and temperatures. Brunt-Vaisala frequency from temperature profiles for the entire period show the thermal forcing mechanism. Short period Gravity Waves (GWs), observed using wavelet analysis, show the mechanical oscillator mechanism and different periodicities during the initial, mature and dissipative phases of convection.

Transient mountain effect was noticed as a dominant source mechanism for the presented case, with strong updrafts and downdrafts from the radar vertical winds (even in isentropes) with strong easterly wind shear. Wave-breaking phenomenon was noticed during squall-line passage, which was due to the existence of meso-scale convective systems as noticed from the NCEP OLR.

Apparent downward phase propagation was observed in temperature and meridional wind perturbations. Zonal wind and horizontal wind shear reveals the easterly phase of the QBO. The energy-propagation during the period of observation was mostly upwards, as the momentum flux above the storm height was negative. There was a positive shear zone above the storm level for the entire period of study, showing significant contribution to the transport of momentum and energy through gravity waves to the middle and upper atmosphere.

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