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Size-Resolved Aerosols Concentration during Extreme Events over a site in NorthWestern India Sunita Verma1, Pramod Kumar2, Swagata Payra1,3, Divya Prakash1 and Brent Holben4 1 2 Birla Institute of Technology (BIT) Mesra, Extension Centre Jaipur, Rajasthan, INDIA Laboratoire de Mecanique et d'Energetique Evry Universite d'Evry-91020, Evry Cedex 3 now at CNRM GAME, Météo-France, CNRS UMR3589, France 4 NASA Goddard Space Flight Center, Greenbelt, MD, USA Contact: [email protected] Introduction Aerosols play an important role in the atmospheric system of our planet. They have a relevant impact on the Earth's radiation budget by direct scattering/absorption of sunlight and by changing cloud properties. Thus they play a major role in the climate system. Aerosol study is challenging due to the complexity of their physical/chemical transformations and the uncertainties in sources/sinks. Thus a long term in-situ dataset is important on regional bases than global average basis. The aerosol number concentrations (ANC) and size distributions over Jaipur in Northwestern India is studied to identify the potential regional sources. The study investigates the effect of different sources during two special events which are contradictory in nature. One is dust storm (DS) while the other one is Diwali (DW) which is celebrated during winter season in India. Jaipur is east side of the Thar Desert and south/west side of the IGP region. There are lot of studies focussed over IGP region. One of the most important focuses is the effect of dust aerosol on climate. Elevated heat pump hypothesis is one of them (when it is coated with anthropogenic/black carbon at IGP region). Observational Analysis 1.0 AOT ( α < 0 . 2 5 ) 0.9 AOT ( α > 0 . 7 0 ) dV / dl n R ( µ/ m µ m) Ae r osol Opt i ca l Th i ck n e ss Figure: The size segregated aerosol number concentration during summer and winter V SD ( α < 0 . 2 5 ) seasons 0.35 V SD ( α > 0 . 7 0 ) 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 300 400 500 600 700 800 W a ve le n gt h ( n m ) 900 1000 1100 0.30 0.25 Figure: Diurnal (24 h) variation in fine and coarse particle during (a) dust storm. The observed meteorological parameters (b) during dust storm 0.20 0.15 0.10 0.05 0.00 0.01 0.1 1 Ra di u s ( µ m ) 10 100 We have separated the background aerosol loading (non-dust) conditions from the typical dusty conditions over Jaipur by dividing the AOT retrievals into two groups of low and high A.E. (α) values for AOT and size distribution. Relatively small change in AOT values are observed with a declining slope at increasing wavelengths i.e AOT340nm=0.65 to AOT1020nm= 0.52 in greater dust loading conditions (α<0.25) while low AOT (<0.3) values are observed for α>0.7 with a declining steep slope at increasing wavelengths in background aerosol SSA spectra Figure: Diurnal (24 h) variation in fine and coarse particle during (a) Diwali and observed (b) meteorological parameters Conclusions The variation in size distribution of aerosols during two seasons is clearly reflected in the log normal size distribution curves. The log normal size distribution curves reveals that the particle size less than 0.8 micro meter has key contributor in winter for higher ANC. It also shows that finer particles are less and coarser particles are more during summer. PSCF Analysis If a trajectory endpoint lies in the ijth cell, the air parcel assumes to collect PM emitted in the cell and transports along the traj. to the monitoring site PSCFij is the conditional probability that an air parcel that passed through the ijth cell had a high concentration upon arrival at the monitoring site. Acknowledgements We greatly acknowledge SERB, Department of Science and Technology (DST), Govt. of India for financial support under research project SR/S4/AS:39/2009. The authors thank the NOAA Air Resources Laboratory (ARL) for the provision of the HYSPLIT transport and dispersion model and website http://www.arl.noaa.gov/ready.php. CIMEL instrument at BIT, Jaipur site is supported under AERONET network by National Aeronautics and Space Administration (NASA). Coarse particle dominates in summer than winter. In winter the fine particle in 0.3 to 0.8 um range is much higher than summer over Jaipur The feature of Bi-modal distribution is showing in volume size distribution and it is more distinct in winter than summer. Results of PSCF are analyzed to find the different source of regions. It has been found that coarse particle mainly comes from the adjacent desert area whereas the contributions of fine particle is mainly local. In DS, the ANC in coarse mode (2 < particle diameter <20 µm) is significantly high while in DW, the ANC in fine mode (0.3 < particle diameter < 2 µm) exhibit higher concentration. During DS the fine and coarse mode particles increased 4.61 and 36.26 times while during DW it increased 3.83 and 0.95 times, respectively. The fine particles increases during diwali festival due to fire crackers burning. The fine particles are not dispersed due to the stable atmospheric condition during winter period in diwali. References Prakash D, Payra S., Soni M., and Verma S, Aerosol particle behavior during Dust Storm and Diwali over an urban location in North Western India, DOI: 10.1007/s11069-013-0780-1, 1-13, Natural Hazards.2013. Payra, S., Verma, S., Prakash, D., Kumar, P., Soni, M., Holben, B., Aerosols properties during dust-storm episodes over Jaipur, Northwestern India, AIP Conference Proceedings, vol. 1527, pp. 515–518, 2013. S. Verma, Payra S., Gautam R., Prakash D, Soni, M., Holben B., and Bell S., Dust events and their influence on aerosol optical properties over Jaipur in Northwestern India, Environmental Monitoring and Assessment (ISSN 0167-63690), Springer, EMAS-D-12-11425, (DOI: 10.1007/s10661-013-3103-9), 2013. Dey S, Tripathi SN, Singh RP, Holben BN (2004) Influence of dust storms on the aerosol optical properties over the Indo-Gangetic basin. J Geophys Res. doi:10.1029/2004JD004924.