NOPR Collection:

Characteristics of spread-F at a temperate latitude station, Jamaica

2016-10-28T09:24:32Z

Title: Characteristics of spread-F at a temperate latitude station, Jamaica Authors: Rastogi, R G Abstract: The characteristics of spread-F at a temperate latitude station vis-à-vis those at an equatorial station in the same longitude zone are described. Temperate latitude spread signature on the ionogram is shown to be due to a number of off-vertical reflections superimposed over the normal vertical p’-f trace. At temperate latitude, the background f region ionization seems to increase during spread-F conditions. Onset time of spread-F seems to increase with distance from the equator, being about 1930 hrs at the equator, about 2200 hrs at the anomaly crest region, and about 0000 hrs at temperate latitudes. Page(s): 160-163

Study of vertical wind and temperature turbulence in a convective boundary layer from sodar observation at Thumba

2016-10-28T09:22:50Z

Title: Study of vertical wind and temperature turbulence in a convective boundary layer from sodar observation at Thumba Authors: Nair, K Narayanan; Kunhikrishnan, P K; Gupta, K Sen; Ramachandran, Radhika Abstract: Sodar data obtained during convective condition at the coastal station, Thumba, have been analysed to study the turbulent nature of vertical wind (w) and the temperature structure parameter (C). The height profile has a slope of -4/3 indicating that the boundary layer was convectively driven during the period of observation. From the autocorelogram of w, the eddy sizes during convection have been estimated. The frequency distribution of w and C shows as non-Gaussian behaviour with positive skewness and the coefficient of skewness has a lower value at a lower height. Page(s): 157-159

A dynamical 2-D wind model for middle atmosphere

2016-10-28T09:14:37Z

Title: A dynamical 2-D wind model for middle atmosphere Authors: Kumar, Somesh; Nagpal, O P Abstract: A two –dimensional zonal wind model has been developed by solving basic wind equations under quasi-geostrophic and quasi-hydrostatic approximations. A realistic value of mean Kelvin wave flux observed experimentally is use to reproduce the westerly phase of semi-annual oscillation (SAO) in the model. The computed winds are qualitatively in good agreement with the observations. Further efforts to incorporate quasi-biennial oscillation (QBO) by way of model refinement are underway. Page(s): 150-156

Supervised classification of SAMIR data over ocean for distinguishing clear and cloudy atmosphere

2016-10-28T09:13:10Z

Title: Supervised classification of SAMIR data over ocean for distinguishing clear and cloudy atmosphere Authors: Pathak, P N Abstract: NOAA-7 cloud imageries have been used in a supervised classification of the SAMIR data and liquid water effect has been delineated. The analysis has allowed the determination of threshold brightness temperatures for the SAMIR data for distinguishing clear and cloudy atmosphere over ocean. Page(s): 144-149