NISCAIR Online Periodicals Repository Community: IJRSP Vol.38 [2009]

Joint statistics of rain rate and event duration for a tropical location in India

Sat, 28 Nov 2009 22:58:59 GMT

Title: Joint statistics of rain rate and event duration for a tropical location in India

Authors: Maitra, Animesh; Das, Saurabh; Shukla, Ashish K

Abstract: The optimum microwave link design requires the knowledge of rain rate distribution as well as of the duration statistics of the rain events. The rain rates measurements at Ahmedabad, a tropical location in India, are analysed and models for various event parameters are developed using three years of continuous measurements. The average number of cases with at least 1 min event duration shows an exponential dependence on the rainfall rate with a correlation coefficient of 0.93. Also, the average durations for different rainfall rates are found to follow a power law with a correlation coefficient of 0.97. It is found that the average duration more effectively represent the event duration at higher rain rates. The results are compared with those obtained for the temperate and other tropical locations to indicate the distinctiveness of the studied parameters over the location. It has been observed that although the tropical locations show similar qualitative features, the characteristics of the Indian region show quantitative difference from other tropical regions.

Page(s): 353-360

Analysis of data on net longwave, shortwave and global radiation during transition period in a tropical station in Southwestern Nigeria

Sat, 28 Nov 2009 22:58:59 GMT

Title: Analysis of data on net longwave, shortwave and global radiation during transition period in a tropical station in Southwestern Nigeria

Authors: Ogolo, E O; Falodun, S E; Oluyamo, S S; Nymphas, E F

Abstract: The present study examines the distribution of surface radiation balance components measured during the Nigerian Micrometeorological Experiment (NIMEX-1). A field study was conducted to measure surface heat fluxes in the boundary layer during the transition period which marks the end of dry season and the onset of wet season (15 February and 10 March 2004) in Southwestern part of Nigeria. Regression equations were obtained using daily average values and hourly mean values between net shortwave and net longwave radiation, respectively with the global radiation. Higher correlations with low standard error of measurement were obtained for daily mean values than hourly mean values. It was also observed that the peak value of each radiation during the period occurred for two hours in the afternoon on an average as expected.

Page(s): 347-352

Horizontal gradients of traffic related air pollutants near a major highway in Agra, India

Sat, 28 Nov 2009 22:58:59 GMT

Title: Horizontal gradients of traffic related air pollutants near a major highway in Agra, India

Authors: Sharma, Anshumala; Massey, David D; Taneja, Ajay

Abstract: In the present study, horizontal gradients of airborne particles and gases were observed perpendicular to the national highway (NH-2) in Agra, India. A negative association was found between distance (from the highway) and ambient concentrations of pollutants. Gradients suggest that the major impact of traffic flow on the pollutants concentration lies within 250 m distance. Over the total measured distance (0-500 m), the maximum percent decrease in concentrations was observed for total suspended particulate matter (TSPM), particulate matter with aerodynamic diameter less than 10 mm (PM₁₀), sulphur dioxide (SO₂), nitrogen dioxide (NO₂), ozone (O₃)andcarbon monoxide (CO) within 0-250 m distance range. However, no significant decrease in concentrations of carbon dioxide (CO₂)was obtained. Correlations between all of the pollutants considered in this study are positive with many of them being highly correlated and significant, which shows that their sources are almost similar. On comparing the pollutants concentrations with available standards of Central Pollution Control Board (CPCB), SO₂, CO, NO₂and O₃ concentrationswere found within the permissible limits, whereas PM₁₀concentration was found higher. This study generates data which can be useful for Asian city planners for planning residential colonies so as to cause minimum exposure to the residents.

Page(s): 338-346

Number concentration characteristics of ultrafine aerosols (atmospheric nanoparticles / aitken nuclei) during 2008 over western Himalayan region, Kullu-Manali, India

Sat, 28 Nov 2009 22:58:59 GMT

Title: Number concentration characteristics of ultrafine aerosols (atmospheric nanoparticles / aitken nuclei) during 2008 over western Himalayan region, Kullu-Manali, India

Authors: Sharma, Nand Lal; Kuniyal, J C; Singh, Mahavir; Negi, Ajay K; Singh, Kesar; Sharma, Priyanka

Abstract: The ultrafine particles of three sizes 200, 30 and 10 A [20 nm (aitken mode), 3 nm, 1 nm (nucleation mode / nano particles)] were monitored with water based condensation particle counter during January-December 2008 at Mohal in Kullu-Manali area of North western Himalayas. The results indicate that diurnal pattern has faint bimodal structure with two peaks, one in morning and other in evening but is not as distinct as found in plains. There is rather constant particle density pattern consistent with vehicular movement from morning till evening. This may also be due to abnormally large bursts of particles (nucleation bursts) which are found to be more in summer than winter, more during sunrise and less during afternoon. The weak nucleation bursts are found to be frequent throughout the year than very strong nucleation bursts which are mostly found during months of June, July and August. The monthly 24 h average density gradually picks up from January, increases rapidly in summer months and then decreases in winter. The density is more in summer than in winter, a trend opposite to plains, may be due to development of warm thermal layer on valley floor while cold layer developed along snowy hilltops in winter leading to convection of fine particles up the slopes of valley during daytime. The relatively more value in September and October is due to month long international Dussehra festival in the valley and unexpected lower values in November and December may be due to low local as well as tourist traffic flow; washout/rainout effects; and higher inversion layer. The vehicular survey conducted agrees well with diurnal, monthly as well as yearly averaged diurnal variation of fine particles. The annual average of 24 h average value of ultrafine particles of three size range is 18045±1212, 16811±2790, and 15407±3109 N cm^-3, respectively. The comparison with earlier results shows significant increase of ultrafine particles indicating impact of vehicular increase in the region.

Page(s): 326-337