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We conducted the campaign studies on Black Carbon (BC) aerosol measured at two different locations such as semi-arid rural, Anantapur (ATP) and tropical wet and dry urban, Tirupati (TPTY) of Andhra Pradesh. The campaign took place from June 1 to June 30, 2015. We studied diurnal variations and weekdays/weekends differences of BC mass Concentration and its correlations with meteorological parameters for two sites. BC exhibits a strong weekly cycle in which weekend concentrations are significantly lower than weekday concentrations by ∼14 and 31% for ATP and TPTY due to the decrease in the local traffic volumes during weekends due to a well-known ‘weekend effect’. An estimation of percentage of contribution of BC indicates the main sources of BC as fossil fuel combustion and which is dominantly observed at TPTY than at ATP. Finally, the influence of the transported air masses has also been discussed with the help of HYSPLIT air mass backward trajectories.

Continuous ground-based measurements of CO, SO 2 and NO 2 were carried out in a semi-arid rural area, Anantapur [14.62 0 N, 77.65 0 E], Southern India, for the period January 2012–December 2012. The maximum CO concentration was observed in winter (310 ± 17 ppbv) followed by summer (180 ± 21 ppbv) and post monsoon (174 ± 20 ppbv), while the minimum in monsoon (72 ± 9 ppbv). Seasonal mean NO 2 /NOx ratios for monsoon, post monsoon, winter and summer were about 0.88, 0.91, 0.76 and 0.80 respectively, indicating a higher conversion of NO to NO 2 over the measurement site. Monthly mean low SO 2 mixing ratio was found (0.46 ± 0.02 ppbv) in monsoon and high (2.42 ± 0.21 ppbv) in winter. Keeping the emissions aside, the levels of CO, SO 2 and NO 2 were influenced by meteorology, urban effects and trans-boundary transport in the lower troposphere. Atmospheric boundary layer (ABL) had the good correlation coefficient (R = 0.76) with solar radiation during daytime, while it was mainly correlated with wind speed during night time (R = 0.42). Diurnal trend of atmospheric visibility was found to be maximum during noon times at around (14:00–16:00 h) about 76 k.m. and minimum during morning periods (06:00–08:00 h) about 45 k.m. A strong positive correlation was observed between BC and CO (R = 0.71) with an average slope, suggesting common or proximate sources likely to be traffic emissions contribution for the production of BC and CO. The SO 2 /NOx and CO/NOx study were strongly suggested that mobile sources were larger contributors over the site and the evidence of transport of emissions from other surrounding regions. Tropospheric Ultraviolet Visible (TUV) radiative transfer model was used to calculate the Photolysis rate coefficients (J(O 3 ), J(NO 2 )). Chemical box model (NCAR-MM) was used to simulate diurnal variation of CO and the results were reported.

Aerosol optical properties are continuously measured at a semi-arid station, Anantapur from June 2012 to May 2013 which describes the impact of surface aerosols on climate change over the region. Scattering coefficient (σ sct ) and absorption coefficient (σ abs ) are obtained from integrating Nephelometer and Aethalometer, respectively. Also, the single scattering albedo (ω 0 ), Scattering/absorption Angstrom exponents were examined during the period of study. Diurnal variations of σ sct and σ abs show a bi-peak pattern with two maxima and one minimum in a day. The largest values of σ sct and σ abs are obtained in winter while the lowest values are measured in monsoon. From the measurements σ sct 550 and σ abs 550 are found to be 110 ± 12.23 Mm − 1 and 33 ± 5.2 Mm − 1 , respectively during the study period. An analysis of the ω 0 suggests that there is a more absorbing fraction in the particle composition over the measurement site. The ω 0 obtained in the surface boundary layer of Anantapur is below the critical value of 0.86 that determines the shift from cooling to warming. A relationship between scattering/absorption coefficients and scattering/absorption Angstrom exponent and single scattering albedo is further examined. In order to understand the origins of the air masses in the study region, we performed seven-day back trajectory analyses based on the NOAA HYSPLIT model. These trajectories were computed at several altitudes (3000 m, 1500 m, and 500 m) for June 2012 and May 2013. These results put in evidence the need of efforts to reduce absorbing particles (black carbon) emissions to avoid the possible warming that would result from the reductions of the cooling aerosol only.

This paper presents the long – term observational studies on aerosol optical properties measured at Sri Krishnadevaraya University (SKU) campus (14° 62′ N, 77° 65′ E, 331m asl), Anantapur, in southern India during 2007–2013 using a ground based Multi – Wavelength solar Radiometer (MWR). Seasonal mean values of Aerosol Optical Depth (AOD) for the whole study period were observed to be 0.34 ± 0.03, 0.45 ± 0.04, 0.24 ± 0.04, and 0.31 ± 0.03 during the winter, summer, monsoon and post – monsoon, respectively. Annual mean values of Angstrom exponent (α) (turbidity coefficient (β)) varied from 0.68 ± 0.25 (0.18 ± 0.03) to 1.1 ± 0.12 (0.32 ± 0.12) during 2007–2013. However, high values of α in the range of 0.8–1.1 were observed during the winter, while low values in the range 0.3–0.7 were noticed during the monsoon. The frequency distribution of AODs during winter in the range of 0.2–0.4 is about 78%, while summer these were shifted from 0.3 to 0.6 around ∼70%, which indicated the dust strongly affects this region. The accumulated frequencies of Angstrom exponent (α) less than 1.0 and greater than 1.0 were about 69% and 31%, respectively, occurred in the summer months indicates the dominance of coarse particles. Columnar size distributions, retrieved from the spectral optical depths, in general, show a bimodal log normal distribution in the optically active size range. The seasonal mean effective radius (Reff) was found to be high in monsoon (∼0.61 μm) and low in winter (∼0.38 μm). The highest mean mass loading values are lies between 475 ± 36 to 769 ± 49 mg m−2 during the summer, whereas the lowest value in the range 204 ± 19 to 278 ± 23 mg m−2 during the monsoon. The difference between α and curvature effect have been studied as a function of AOD on seasonal basis. Finally, to understand the contribution of long range transported aerosols, we have investigated this analysis making use of back trajectories obtained from the HYSPLIT model for different seasons.

In the present study, collocated and simultaneous measurements on meteorological parameters and solar radiation on horizontal surface were obtained from different meteorological sensors and pyranometer sensor over a semi-arid station, Anantapur (14.62° N, 77.65° E and 331 m asl) during January–December 2013. The temperature is usually lower at midnight, decreasing in the early hours of the morning around 08:00 LT (Local Time) (24.71 ± 2.7 °C), and then increasing rapidly until just after midday at 15:00 LT (31.88 ± 3.2 °C). It decreases to 26.70 ± 2.9 °C during the night around 23:00 LT. The relative humidity ranges from 30–76%, 20–65%, 46–80% and 48–90% during winter, summer, monsoon, and post-monsoon seasons respectively. The diurnal variation of soil moisture exhibits slight variations at different depths over the region. The diurnal and monthly variations of solar radiation as well as clearness index (k t ), diffusion index (k d ) were studied in the present study. In diurnal variation, it shows a steady rise in solar radiation received at the surface after 7:30 LT and attains a maximum solar radiation between 12:00 – 13:00 LT. The amount of solar radiation also varies depending on the time of day and the season. The annual mean of daily global, extraterrestrial and diffuse radiation at Anantapur is found to be 202.43 ± 40.45, 408.15 ± 61.63 and 49.33 ± 11.26 W/m 2 . The high global and diffuse solar radiations were observed during March-May (257.67 ± 34.18 W/m 2 , 65.07 ± 11.20 W/m 2 ) whereas low global and diffuse solar radiations during monsoon months (137.66 ± 12.41, 33.47 ± 7.44 W/m 2 ). In the case of extraterrestrial solar radiation was high in the month of December (472.92 ± 0.67 W/m 2 ) and low in the month of June (312.87 ± 2.58 W/m 2 ).

Continuous real-time measurements of aerosol scattering properties were investigated at Anantapur (14° 62′ N, 77° 65′ E, 331 m asl), a semi-arid region in southern India for the period of January 2011–December 2011, using a three-wavelength Integrating Nephelometer. Aerosols scattering properties like the scattering coefficient (σsp), backscattering coefficient (σbsp), scattering Angstrom exponent (A), backscattering ratio (bλ) and asymmetry parameter (gλ) were measured for the period of study. The average values of (±standard deviation) σsp, σbsp at 550 nm ( σ sp 550 , σ bsp 550 ) and A(700/450) were found to be 97 (±9.2) M m−1 and 14 (±0.93) M m−1 and 1.02 (±0.3), respectively. The estimated average values of bλ and gλ at 550 nm from σ sp 550 and σ bsp 550 were 0.13 (±0.09) and 0.59 (±0.1), respectively. The maximum asymmetry parameter at 550 nm was found to be 0.63 ± 0.01 in the month of October and minimum (0.52 ± 0.03) during March, which shows the opposite trend with backscattering ratio. Significant correlation coefficients were noticed between different aerosol optical properties. The highest values of σ sp 550 were observed during weekdays whereas low values during weekends. Scattering Angstrom exponent for the summer and winter seasons has been consistent with the input of fine mode particles from anthropogenic origin.

The continuous measurements of surface ozone (O3) and oxides of nitrogen (NOx) present in the ambient air were carried out on a semi-arid rural area in Anantapur [14.62° N, 77.65° E], South India during the period beginning from March 2012 to February 2013. The diurnal variation of surface ozone (O3) showed a minimum at sun rise and late evenings and maximum at noon time, due to slow titration of O3 with oxides of nitrogen (NOx). The monthly average minimum/maximum of O3 observed in August/March was 19.9 ± 0.3/55.8 ± 2.9 ppbv. The monthly average variation of NOx was found to be high (6.67 ± 0.8) in November and noticed low (2.07 ± 0.2) concentrations in May. The monthly mean maximum of O3 during day time (night time) was observed as 64.9 ± 5.3 (45.3 ± 4.1) ppbv in March, and mean low concentration was about 19.9 ± 1.02 (12.8 ± 0.9) ppbv in August. The monthly mean enhanced concentration of NOx during the day time/night time was about 5.0 ± 0.6/8.7 ± 0.9 in November and the fallen concentration was noticed 1.5 ± 0.2/2.7 ± 0.3 in May. The spatial distribution of O3 was associated with the air flow pattern, air mass trajectories and boundary layer heights. The water vapor content also played a significant role in the diurnal variation of O3 in addition to photo chemistry. The diurnal variation of UV radiation with O3 and NOx has been analyzed and the results are reported. And the diurnal and seasonal variations in boundary layer height have also been discussed. The monthly mean variation of aerosol optical depth (AOD) is similar to that of tropospheric ozone, with a correlation coefficient of r = 0.60. The diurnal and seasonal patterns of ozone were simulated using the chemical box model (NCAR Mater Mechanism) and when compared with the observed ones, the results are found to be in good agreement with the observed ones.