NOPR Collection:

Harmful electromagnetic environment near transmission tower

2014-01-29T16:53:31Z

Title: Harmful electromagnetic environment near transmission tower Authors: Pathak, P P; Kumar, Vijay; Vats, R P Abstract: The penetration of RF and microwave electromagnetic fields into human body and its possible consequences are studied. Earlier observations are theoretically verified which show that the radiation from high power transmission tower is more harmful to the people living nearby as compared to that from the low power transmission tower. Absorption of electric component of electromagnetic radiation falling on the body, which increases with frequency, may result into temperature rise in the body. However, the magnetic induction, being very weak in comparison to the earth's magnetic field, is expected to have no effect on the human body. Page(s): 238-241

Aerosol optical depth variation observed using sun-photometer over Indore

2014-01-17T16:51:23Z

Title: Aerosol optical depth variation observed using sun-photometer over Indore Authors: Gupta, Pawan; Gadhavi, Harish; Jayaraman, A Abstract: Columnar aerosol optical depth measurements have been made over Indore (22.7° N, 75.9° E) during May 2001-March 2002 at four spectral bands centred around 400, 499, 668 and 858 nm using a hand-held sun-photometer. The aerosol optical depth (AOD) shows seasonal variation with high values in summer and low values in winter. The summer-increase is found to be due to the high wind speed producing larger amount of wind-derived dust particles. As the summer monsoon sets in at the end of June there is an appreciable decrease in the AOD values. The AOD values decrease further in winter and the decrease is more at higher wavelengths indicating that there is a general reduction in the number of bigger particles. Also during winter months the wind direction changed to southerly and south-easterly which brings air that is more rural to the measurement site. The amplitude of the observed high AOD values in summer and low during winter, is higher for longer wavelengths which shows that the coarse particles contribute more to the observed variation as compared to sub-micron particles. Comparison of the AOD values over Indore with that of Trivandrum and Visakhapatnam shows that the Indore values are comparable to that of Vi sakhapatnam, but much higher than the Trivandrum values indicating the influence of industrialization and higher population. Page(s): 229-237

Diurnal and seasonal variations of point discharge current during thunderstorms at a tropical inland station

2014-01-18T16:51:04Z

Title: Diurnal and seasonal variations of point discharge current during thunderstorms at a tropical inland station Authors: Kandalgaonkar, S S; Tinmaker, M I R; Kulkarni, M K; Nath, Asha Abstract: The data of point discharge current (PDC) measurements during a total of 65 thunderstorms at Pune (18°32'N, 73°51'E) are analyzed to study the PDC local diurnal variation and some issues related with the current. The analysis shows that about 83% of the total quarter hours occupied by PDC are localized between 1400 hrs LT and 2400 hrs LT and the remaining 17% are sparsely distributed over midnight to early hours in the morning. The net result of this study revealed that PDC is the dominant agent for the negative charging of the earth’s surface and should be identified as an active element participating in global electrical circuit. The phase relationship between the positive and negative current during the diurnal period suggests that the active period of current of one polarity has a preferred time of occurrence over the other and by the late night hours the positive charge showed its sustained occurrence over the negative one. The seasonal relationship between storm averaged PDC and monthly mean maximum surface air temperature has also been examined. The comparison of seasonal average amplitude of PDC has suggested a strong positive correlation with the monthly mean maximum surface air temperature. The average amplitude of PDC during thunderstorm in premonsoon season is found to be about three times higher than those during the monsoon season. An examination of association between duration and amplitude variation of PDC showed that storms that are closer to the station within 4 km have longer duration and stronger current amplitude than when they are more than 4 km away. Page(s): 221-228

Drop size distribution of rainfall of different intensities

2014-01-20T16:52:03Z

Title: Drop size distribution of rainfall of different intensities Authors: Kumar, V Sasi; Sampath, S; Vinayak, P V S S K Abstract: Drop size distribution was measured at Thiruvananthapuram, Kerala State, India, during April, June and July 2001 using a Joss-Waldvogel type disdrometer. The instrument gives the number of drops in 20 size classes ranging from 0.3 mm to > 5 mm. Each month's data were sorted, based on rainfall intensity, into periods of rainfall intensity < 1 mm/h r, 1-3 mm/ hr, 3-10 mm/hr, 10-30 mm/hr and > 30 mm/hr. The average number of drops in each size class was computed for each set of data. Exponential and Г distribution functions were then fitted to each data set. The results showed that, in June and July, the data approximated an exponential distribution for low rainfall intensities, but became closer to the Г distribution at higher intensities. However, in April all data fitted the Г distribution, irrespective of rainfall intensity. Page(s): 217-220