NOPR Collection:

Variability of meteorological factors on surface refractive index over Mowe, a coastal area in Nigeria

2014-12-01T00:00:00Z

Title: Variability of meteorological factors on surface refractive index over Mowe, a coastal area in Nigeria Authors: Falade, J A; Adesanya, S O; Akinyemi, G A Abstract: Radio climatology is an important factor in understanding radio wave propagation particularly in the troposphere where time varying properties due to weather conditions are prevalent. Therefore, the diurnal and seasonal variations of surface radio refractivity for Mowe (06°E, 52°N) via Lagos in South-West Nigeria are studied. Particular emphasis is laid on diurnal variations of the surface refractivity, which is high through the night and drops sharply just before sunrise and starts to pick up slightly around 14:00 to 15:00 hrs LT. It drops to minimum around 16:00 hrs LT before it increases again. The sinusoidal patterns of plots are obtained for temperature, relative humidity and refractivity. The patterns of the profile obtained are attributed to the oscillatory movement of inter-tropical discontinuity (ITD), which largely dictate the condition of weather and account for high rainfall in the coastal region where the study is undertaken. The results show that surface radio refractivity, generally, has higher value during the rainy season than dry season, which partly coincide with the harmattan period. Page(s): 355-361

On the Markov chain models for monsoonal rainfall occurrence in different zones of West Bengal

2014-12-01T00:00:00Z

Title: On the Markov chain models for monsoonal rainfall occurrence in different zones of West Bengal Authors: Basak, Pijush Abstract: The probability distribution of pattern of rainfall during the monsoon season (June-September) over different regions of West Bengal (India) has been analysed with the help of Markov chain models of various orders. The analysis is based on relevant data of 25 years (1971-1995) for ten meteorological stations spread over the state. The determination of the proper order that best describes the precipitation over the region is carried out using Akaike’s Information Criteria. The analysis clearly indicates that first order Markov chain model is the best one for rainfall forecasting. It is found that there is a period of occurrence of rainfall phenomenon (2-4 days) over the various stations. Moreover, the steady state probabilities and mean occurrence time of precipitation days and dry days have also been calculated for first and second order Markov chain models. The computation reveals that the observed and theoretical values of steady state probabilities are realistically matched. Page(s): 349-354

Contribution of vehicular emission on urban air quality: Results from public strike in Hyderabad

2014-12-01T00:00:00Z

Title: Contribution of vehicular emission on urban air quality: Results from public strike in Hyderabad Authors: Mahalakshmi, D V; Sujatha, P; Naidu, C V; Chowdary, V M Abstract: The aim of this study is to analyse the amount of atmospheric pollution caused by vehicular traffic and the public strike, during which vehicular traffic is highly curtailed, offers an excellent opportunity for our purpose. The present study is carried out through systematic in situ measurements of particulate matter (PM), black carbon (BC) and carbon monoxide (CO) over the urban region of Hyderabad, India during two public strikes on 24 December 2009 and 18-21 January 2010. The results of the study suggest that the pollutant concentration decreases to a considerable extent, especially for BC, particulate matter (PM₁₀, PM_2.5and PM_1.0) and CO in both the cases indicating that vehicular emission alone is largest contributor to air pollution. A significant reduction of BC and PM (48% and 28%, respectively in first public strike and 27% and 30%, respectively in second public strike) was observed as compared to pre-strike period. A significant reduction of about 20% in CO concentration during strike period of 18-21 January 2010 was observed as compared to pre-strike period (14-17 January 2010). Page(s): 340-348

Anomalous behaviour of very low frequency signals during the earthquake events

2014-12-01T00:00:00Z

Title: Anomalous behaviour of very low frequency signals during the earthquake events Authors: Latha, T Madhavi; Naidu, P Peddi; Rao, D N Madhusudhana; Devi, M Indira Abstract: The seismo-ionospheric coupling has been extensively studied in the recent years adopting various ionospheric parameters, like the critical frequency of F₂ and E_s layers and total electron content (TEC). There have been reports of seismic signatures in the amplitude and phase of the very low frequency (VLF) waves when an intense earthquake occurs near the propagation path. In the present paper, the amplitude of VLF waves transmitted from GQD (UK), GBZ (UK) and TBB (Turkey) received in South France during the period 2010-2013 has been studied for the precursory effect of earthquakes on the morning and evening terminator timings (TT). Six earthquake events of magnitude greater than 5 have been considered. The results of the present study show that the evening terminator undergoes many fluctuations during the pre-earthquake period of 5-15 days. But the pre-earthquake fluctuations in the morning terminator are predominant for three events, namely 8 March 2010, 11 April 2010 and 22 May 2012. The VLF day (time between morning terminator and evening terminator) is observed to be longer in the pre-earthquake period for three events. Page(s): 333-339