An investigation of long-distance propagation of gravity waves under CAWSES India Phase II Programme

Abstract

Abstract. Coordinated measurements of airglow features from the mesosphere-lower thermosphere (MLT) region were performed at Allahabad (25.5 • N, 81.9 • E) and Gadanki (13.5 • N, 79.2 • E), India to study the propagation of gravity waves in 13-27 • N latitude range during the period June 2009 to May 2010 under CAWSES (Climate And Weather of Sun Earth System) India Phase II Programme. At Allahabad, imaging observations of OH broadband emissions and OI 557.7 nm emission were made using an all-sky imager, while at Gadanki photometric measurements of OH (6, 2) Meinel band and O 2 (0, 1) Atmospheric band emissions were carried out. On many occasions, the nightly observations reveal the presence of similar waves at both locations. Typically, the period of observed similar waves lay in the 2.2-4.5 h range, had large phase speeds (∼ 77-331 m s −1 ) and large wavelengths (∼ 1194-2746 km). The images of outgoing long-wave radiation activity of the National Oceanic and Atmospheric Administration (NOAA) and the high-resolution infrared images of KALPANA-1 satellite suggest that such waves possibly originated from some nearby convective sources. An analysis of their propagation characteristics in conjunction with SABER/TIMED temperature profiles and Horizontal Wind Model (HWM 2007) wind estimates suggest that the waves propagated over long distances (∼ 1200-2000 km) in atmospheric ducts.

An investigation of the ionospheric F region near the EIA crest in India using OI 777.4 and 630.0 nm nightglow observations

“…Examples are atomic oxygen density (Lednyts'kyy et al, 2014;Russell et al, 2005), vertical transport (Broadfoot and Gardner, 2001;Hays et al, 2003), mesospheric temperatures (Innis et al, 2001;Scheer and Reisin, 2007;Holmen et al, 2014;Parihar et al, 2017, and references cited therein), mesospheric winds (Lloyd et al, 1990), density and pressure (Takahashi et al, 2004), thermospheric temperatures and wind velocities (Cocks, 1983;Vila et al, 1998;Ford et al, 2006Ford et al, , 2008Nakamura et al, 2017), F region peak electron density and its height (Sahai et al, 1981;Makela et al, 2001), F region zonal drifts (Yao and Makela, 2007), etc. Often the derived parameters are then utilized to understand the behaviour of the emitting region, mainly its chemistry, dynamics and electrodynamics (Semenov, 1988;Fagundes et al, 2001;Makela et al, 2001Makela et al, , 2004Shiokawa et al, 2003;Scheer and Reisin, 2007;Ford et al, 2008;López-González et al, 2009;Parihar et al, 2013;Holmen et al, 2014). Other ground-based techniques include lidars and radars; however, airglow experiments remain a favourite due to their wellestablished simplicity, cost-effectiveness and capability for continuous operation on a longer timescale (Ford et al, 2008;Espy et al, 2011;Holmen et al, 2014;Scheer and Reisin, 2007).…”

A comparison of ground-based hydroxyl airglow temperatures with SABER/TIMED measurements over 23° N, India

“…Around 825 nm, the quantum efficiency of the CCD detector is 70-80 % and the dark current is less than 0.001 e − pixel −1 s −1 . Parihar and Taori (2015) described this imaging system in detail. Optical filters for monitoring P 1 (2) line and P 1 (4) line had a bandwidth of ∼ 1.1 nm, while that of the 857.0 nm filter was ∼ 2.0 nm.…”

“…Using this technique, the time series of the intensity of P 1 (2) line, P 1 (4) line and background emissions for five locations were recorded for further analysis. This process was described in detail in Parihar and Taori (2015). A typical example of such a generated intensity series of P 1 (2) Figure 1.…”

Mesospheric gravity wave characteristics and identification of their sources around spring equinox over Indian low latitudes

“…From the Indian sector, there are also several reports (e.g., Mukherjee 2003Pragati et al, 2010;Lakshmi Narayanan and Gurubaran, 2013;Parihar and Taori, 2015) which document the small-scale gravity wave characteristics. For example, using 5 months of OH airglow imager data from January to May 2008 at Allahabad (25.45 • N, 81.85 • E), Pragati et al (2010) reported that most of the small-scale gravity waves propagate to the north and northeast in March and May.…”

“…Likewise, during 2007 Lakshmi Narayanan and Gurubaran (2013) reported the seasonal variation of the gravity wave characteristics over Tirunelveli (8.71 • N, 77.81 • E). Recently, Parihar and Taori (2015) investigated the longdistance propagating gravity waves using the coordinated bi-station airglow data (Airglow photometer over Gadanki (13.5 • N, 79.2 • E) and all-sky airglow imager over Allahabad (25.5 • N, 81.9 • E)). They concluded that convection might be a source of the noted long-distance gravity wave events.…”