Characteristics Of Inertia-gravity Waves Research Articles

An investigation into the characteristics of inertia gravity waves in the upper troposphere/lower stratosphere using a 205 MHz wind profiling radar

ABSTRACTA stratosphere-troposphere (ST) wind profiler at 205 MHz is operational at the Advanced Centre for Atmospheric Radar Research (10.04N; 76.33E), Cochin University of Science and Technology, India. This profiler provides accurate three-dimensional wind profiles for an altitude range of 315 m to 20 km. In this paper, we present the characteristics of inertia-gravity waves (IGWs) observed in the upper troposphere/lower stratosphere from uninterrupted observations of wind profiles taken from 22–27 October 2016. The propagation properties of the waves were derived using hodograph analysis. The intrinsic period of the IGWs is found to be 28.75 hours, and the vertical and horizontal wavelengths of the wave are 3.74 and 1221 km, respectively. The hodograph shows a clockwise rotation of the ellipse, which indicates an upward propagation of energy from the upper troposphere to the lower stratosphere. These waves were observed in conjunction with a persistent deep depression over the Bay of Bengal.

Inertia gravity wave characteristics and associated fluxes observed using five years of radiosonde measurements over a tropical station

In the present study, characteristics of inertia gravity waves (IGWs), associated momentum and heat fluxes, and their source mechanisms have been studied using five years (2006–2011) of high resolution radiosonde observations collected from the tropical station, Gadanki (13.5°N, 79.2°E), India. The deduced horizontal wavelengths are of the order of a few 1000s km in the troposphere and stratosphere in contrast to those low horizontal wavelengths reported earlier from this location. The estimated horizontal wavelengths match well with those reported very recently using satellite (HIRDLS and SABER) measurements. Clear link between the fluxes and background wind are noticed with enhanced values during the westward phase of zonal wind. Although two sources for the generation of IGWs namely strong convection and wind shears coexist during monsoon season, wind shear is found to be mainly responsible.

Inertia gravity waves associated with deep convection observed during the summers of 2005 and 2007 in Korea

[1] Characteristics of inertia gravity waves associated with convection are investigated in the lower stratosphere using high-resolution radiosonde data observed from 18 June to 15 July of 2005 and 2007 in Korea. Three-dimensional ray-tracing model and reanalysis data are used to investigate the propagation and the sources of the observed waves. The observed waves associated with convections are discriminated based on the existence of convections when and where the rays reach the average height range of convective clouds. Waves observed in 2005 and 2007 show similar spectral characteristics, but wave energy in 2007 is significantly larger than in 2005. The observed waves propagate from three source regions: the northeastern, southeastern, and western regions around Korea. They show preferential propagation directions based on their sources, and convections from the western region generate larger-amplitude gravity waves than the other two regions. The spectral characteristics of the observed waves are determined largely by those of the convective forcing, along with the wave propagation condition associated with background wind and stability. The significantly larger mean wave energy in 2007 occurs because more observed waves originate from the western region of Korea in 2007 than in 2005 where convective forcing is much larger than in the other source regions.

Characteristics of inertia-gravity waves around jet stream from radiosonde observations in Wuhan (30.5°N, 114.4°E)

The 5 years’ radiosonde data obtained from January 2000 to December 2004 in Wuhan (30.5°N, 114.4°E) have been used for studying the behaviors of inertia-gravity waves in the vicinity of the jet stream. It is observed that the wave intensity has a similar seasonal variation with the jet stream intensity with a strong winter maximum and a summer minimum. Moreover, a similar inter-annual trend for both the wave intensity and jet stream intensity is also found. These results suggest that the jet stream may be the predominant source of the inertia-gravity waves in the troposphere and lower stratosphere over Wuhan in the period of the 5 years. It is noticed from 28 radiosonde profiles during wintertime that the energy of inertia-gravity waves exhibits upward and downward propagation respectively above and below the jet stream. This indicates that the source of the inertia-gravity waves is within the jet stream. In these cases, the twin waves below and above the jet stream usually hold similar amplitudes. The horizontal propagation of the twin waves also shows some interesting relationship.

Characteristics of inertia gravity waves over the South Pacific as revealed by radiosonde observations

Using horizontal wind and temperature data with fine vertical resolution obtained by radiosondes, we investigate the characteristics of parameters and propagation properties of inertia gravity waves in the upper troposphere and lower stratosphere in the subtropics and extratropics over the South Pacific where very few observations have so far been done. Components extracted by a band‐pass filter having cutoff vertical wavelengths of 0.5 and 5 km are analyzed as gravity waves. Gravity wave parameters such as intrinsic frequency , vertical and horizontal wavelengths, and phase and group velocities are estimated by hodograph analysis. The statistics on such parameters are presented for both the stratosphere and troposphere for the three latitudinal ranges 17°–24°S, 25°–33°S, and 34°–48°S. The horizontal wavelengths decrease and increases with increasing latitude south. The dominant values for the Coriolis parameter f divided by are ∼0.5 in the lower stratosphere and ∼0.3 in the troposphere, with little dependence on latitude. The dominant vertical wavelengths for upward propagating waves are longer in the troposphere than in the lower stratosphere. The most dominant direction of horizontal propagation is southward, with a little bias toward southeastward. A case study using ray tracing suggests that the major source of such southeastward waves is located in the upper troposphere. Notable northward propagation of gravity waves is also found in the subtropical lower stratosphere. The source of the gravity waves is considered to be a cutoff cyclone developing in the upper troposphere.