NOPR Collection: Special Issue: Improved understanding of the structure and dynamics of the middle atmosphere and its response to various geophysical phenomena (Guest Editor: Gopa Dutta)

Large scale anomalous temperature and wind variations in the lower and middle atmospheres during the solar eclipse of 15 January 2010

2014-02-01T00:00:00Z

Title: Large scale anomalous temperature and wind variations in the lower and middle atmospheres during the solar eclipse of 15 January 2010 Authors: Ramkumar, T K; Ghosh, Priyanka; Reddy, K Krishna; Kumar, K Niranjan; Kumar, S Balaji; Reddy, A Hari Krishna; Reddy, M Venkatrami; Prasad, S B Surendra Abstract: During 12-17 January 2010 centered around 15 January, annular solar eclipse event occurred over the Indian tropical region. The Indian Space Research Organisation (ISRO) sponsored and provided 18 GPS radiosondes (ISRO developed Dr Pisharoty sondes) to the Department of Physics, Yogi Vemana University, Kadapa (14.5°N, 78.9°E), to study the effects of solar eclipse on the atmospheric dynamics and structure. The analyses of the data obtained from these radiosondes launched by balloons indicate that during this eclipse period, the atmosphere experienced ever recorded largest stratospheric cooling (maximum cooling of ~15 K at 36 km). As a first time ever report, significant localized variations in the strength of the large-scale zonal Walker and meridional Hadley circulations were also found over the Indian longitude region during this solar eclipse event. Page(s): 75-82

A case study of gravity waves observed in OH rotational temperatures at Kolhapur (16.8ºN, 74.1ºE), India

2014-02-01T00:00:00Z

Title: A case study of gravity waves observed in OH rotational temperatures at Kolhapur (16.8ºN, 74.1ºE), India Authors: Parihar, Navin; Mukherjee, G K Abstract: Ground-based measurements of OH (8, 3) Meinel band emissions were carried out at Kolhapur (16.8ºN, 74.1ºE), India during November 2002 – May 2003 using two tilting filter photometers. OH rotational temperature ~ a proxy of atmospheric temperature around 87 km, were derived from the intensity information of P₁(2) and P₁(4) lines of OH (8, 3) band. On most nights, strong well-defined oscillations having periodicities in the range of 1 – 3 h were observed in OH temperature series. In this paper, a case study of such short-period oscillations, observed on few nights in the OH temperature, has been presented. Page(s): 67-74

Modulation of thermal structure in the upper troposphere and lower stratosphere (UTLS) region by inertia gravity waves: A case study inferred from simultaneous MST radar and GPS sonde observations

2014-02-01T00:00:00Z

Title: Modulation of thermal structure in the upper troposphere and lower stratosphere (UTLS) region by inertia gravity waves: A case study inferred from simultaneous MST radar and GPS sonde observations Authors: Das, Siddarth Shankar; Kumar, K K; Uma, K N; Ratnam, M V; Patra, A K; Das, S K; Ghosh, A K; Jain, A R Abstract: The observations of multiple layer structures in the MST radar backscattering echoes in the upper troposphere and lower stratosphere (UTLS) region are discussed in this paper. The fact remains same that the enhanced echoes seen in the radar backscattering are due to the strong positive and negative thermal gradients. Simultaneous observations of MST radar (1 hourly) and GPS sonde (6 hourly) over a tropical station Gadanki (13.5°N, 79.2°E) reveal the presence of 1.5-2 km vertical wavelength in the winds, temperature and radar backscattering echoes in the UTLS region during Indian summer monsoon (ISM). The analysis also reveals that the presence of inertia gravity wave (IGW) triggered due to tropical easterly jet (TEJ) associated with ISM is the prime candidate for the observed thermal gradients in the UTLS region. Page(s): 11-23

Effect of cumulus and microphysical parameterizations on the JAL cyclone prediction

2014-02-01T00:00:00Z

Title: Effect of cumulus and microphysical parameterizations on the JAL cyclone prediction Authors: Reddy, M Venkatarami; Prasad, S B Surendra; Krishna, U V Murali; Reddy, K Krishna Abstract: Weather Research and Forecasting (WRF) model is used to predict the track and intensity of JAL cyclone, which formed during 04-08 November 2010 over the Bay of Bengal. The model has been simulated with numerous experiments using the logical/scientific combination of convection and micro-physics schemes. The model simulations have been conducted with different initial conditions to know the effective track and intensity prediction of JAL cyclone. In addition, the effect of cumulus parameterization schemes at different resolution (27 and 9 km) on the cyclone track and intensity is reported. The model simulated results showed the importance of cumulus schemes and their role at 9 km horizontal resolution. The results indicate that the track predicted by Kain-Fritsch (KF) scheme is in good agreement with the observed track in all the experiments and the land fall error is minimum (~11 km) for the combination of Ferrier and KF scheme with 0000 hrs UTC on 04 November 2010 as initial condition. Strong intensity is produced by KF, New Grell (NG) schemes and weak intensity is produced by Betts-Miller-Janjic (BMJ) scheme with all microphysics parameterization (MP) combinations. Further, the dependency of intensity of cyclone has been studied in terms of surface latent heat flux, divergence and vorticity fields. To validate the model performance, different meteorological parameters are derived from the model simulations over three different regions and are compared with the observed meteorological parameters. The model results are in good agreement with the observed parameters, but variations are observed at the landfall /dissipation of the cyclone. Page(s): 103-123