NISCAIR Online Periodicals Repository Collection: IJRSP Vol.39(4) [August 2010]

Carbonaceous aerosols at a suburban site in Indo-Gangetic plain

Title: Carbonaceous aerosols at a suburban site in Indo-Gangetic plain

Authors: Satsangi, Aparna; Pachauri, Tripti; Singla, Vyoma; Lakhani, Anita; Kumari, K Maharaj

Abstract: Carbonaceous aerosols are emitted by combustion sources and may influence the climate by altering the radiation balance of the atmosphere. The carbonaceous component of the atmospheric aerosols is composed of two main fractions, viz. organic carbon (OC) and black carbon (BC). BC is emitted from the incomplete combustion while OC comes from the primary emission such as traffic exhaust and biomass burning and is also formed through atmospheric chemical conversion processes. Carbonaceous aerosols were monitored at a suburban site, Dayalbagh, Agra from January to October 2009 in the present study. It was found that total suspended particulate mass (TSPM) varied from 79 to 658 g m^-3with an average of 273±179.9 g m^-3. Also, daily concentrations of OC and BC ranged from 20.4 to 147.4 g m^-3and from 1.4 to 20.3 g m^-3 with the overall average concentrations of 60.9±40.5 g m^-3and 7.5±4.6 g m^-3, respectively. OC/BC ratios indicate the emission sources of carbonaceous aerosols. When the OC/BC ratio exceeds 2.0, it indicates that carbonaceous aerosols mainly originate from secondary organic transformation. Daily average OC/BC ratio varied between 5.2 and 16.2 with an average of 8.1. To give an insight into the source contribution of OC and BC, correlation coefficient was determined. The correlation coefficient is found to be 0.79. This indicates that major fraction of OC and BC originates from a common source. Distinct monthly variation was observed in their concentrations.

Page(s): 218-222

Measurement of atmospheric aerosols during monsoon and winter seasons at Roorkee, India

Title: Measurement of atmospheric aerosols during monsoon and winter seasons at Roorkee, India

Authors: Saxena, Deepti; Yadav, R; Kumar, Adarsh; Rai, Jagdish

Abstract: Measurement of aerosol concentration has been carried out in view of some meteorological parameters like wind speed, temperature, relative humidity and rainfall during south-east (SE) monsoon (June-September 2006) and winter (November 2006-February 2007) at Roorkee, India. The measurements were done with the help of laser beam scatterometer for wide range of aerosols (0.05-3.0 μm). The present study reveals the fact that the number density of aerosols is very much affected by meteorological parameters. The aerosol concentration was minimum in August, September and November 2006 and remained around maximum during June-July 2006 and January-February 2007. During monsoon period, the rain plays important role in characterizing aerosol density. The aerosol concentration and size were found to be decreased during September 2006 although relative humidity was found to be very high due to scavenging of aerosol particles.

Page(s): 208-217

Preliminary reverse impulse in SC (Y) at off - equatorial stations in India

Title: Preliminary reverse impulse in SC (Y) at off - equatorial stations in India

Authors: Rastogi, R G; Ahmed, K

Abstract: The storm sudden commencement (SSC) at 2345 hrs UT on 24 September 1998, occurring at around local sunrise for Indian stations had produced uniquely two–step impulses on the H magnetogram at all stations. The amplitude ∆H had increased progressively from Trivandrum to Gulmarg, unlike the characteristic of the day time equatorial enhancement of SC (H). The solar wind parameters too showed abnormal variations during the period of SC. The magnetogram trace for declination (or eastward field Y) recorded a preliminary reverse impulse (PRI) close to the latitude of Sq focus at stations Gulmarg, Ujjain, Nagpur and Shillong. The PRI was absent in SC (Y) at equatorial stations Trivandrum and Pondicherry. This observations show a new complex relationship between the ionospheric dynamo and magnetospheric dawn / dusk electric field with the equatorial geomagnetic field around sunrise.

Page(s): 203-207

Diurnal and seasonal variation of fading rates of E- and F- region echoes during IGY and IQSY at the equatorial station of Ibadan

Title: Diurnal and seasonal variation of fading rates of E- and F- region echoes during IGY and IQSY at the equatorial station of Ibadan

Authors: Somoye, E O

Abstract: Fading rates of E- and F-region echoes observed at Ibadan (7.4°N, 3.9°E, 6°S dip) during the International Geophysical Year (IGY) 1958 and the International Quiet Year of the Sun (IQSY) 1964 are investigated for diurnal and seasonal variations. The fading rates of E- and F-region echoes are found to be of the same order of magnitude during the IQSY. However, the same is not true during IGY indicating that fading of F-region echoes is dependent on solar activity while that of E-region echoes is not as fading rate of E-region echoes are about the same during both epochs. The fading rate is found to be maximum at noon and minimum at sunrise and sunset for E-region echoes during both epochs and for F-region echoes during IQSY. During IGY, fading rate is maximum at noon; and minimum at sunrise and 2000 hrs LT (i.e. post sunset) at both epochs and for the two regions about same times of reversal of F-region East-West (EW) and E×B vertical drift during solar maximum. The maximum at noon appears to be due to: (i) continuous daytime rise in hmF2 which enhances irregularities and (ii) spread F irregularities generated by sudden increase in E×B plasma uplift not seen by the close-spaced antenna technique used in the present study. F-region fading rate is maximum during December solstice while E-region fading rates show no seasonal variation.

Page(s): 194-202