Raj P Guleria
Articles written in Journal of Earth System Science
Volume 121 Issue 1 February 2012 pp 221-235
Nand L Sharma Jagdish C Kuniyal Mahavir Singh Pitamber P Dhyani Raj P Guleria Harinder K Thakur Pan S Rawat
Aerosol parameters are measured using a ground-based Multi-wavelength Radiometer (MWR) at Mohal (31.90°N, 77.11°E, 1154 m amsl) in the Kullu valley during clear sky days of a seasonal year. The study shows that the values of spectral aerosol optical depths (AODs) at 500 nm and the Ångstrom turbidity coefficient ‘𝛽’ (a measure of columnar loading in atmosphere) are high (0.41 ± 0.03, 0.27 ± 0.01) in summer, moderate (0.30 ± 0.03, 0.15 ± 0.03) in monsoon, low (0.19 ± 0.02, 0.08 ± 0.01) in winter and lowest (0.18 ± 0.01, 0.07 ± 0.01) in autumn, respectively. The Ångstrom wavelength exponent ‘𝛼’ (indicator of the fraction of accumulation-mode particles to coarse-mode particles) has an opposite trend having lowest value (0.64 ± 0.06) in summer, low (0.99 ± 0.10) in monsoon, moderate (1.20 ± 0.15) in winter and highest value (1.52 ± 0.03) in autumn. The annual mean value of AOD at 500 nm, ‘𝛼’ and ‘𝛽’ are 0.24 ± 0.01, 1.06 ± 0.09 and 0.14 ± 0.01, respectively. The fractional asymmetry factor is more negative in summer due to enhanced tourists’ arrival and also in autumn months due to the monthlong International Kullu Dussehra fair. The AOD values given by MWR and satellite-based moderate resolution imaging spectro-radiometer have good correlation of 0.76, 0.92 and 0.97 on diurnal, monthly and seasonal basis, respectively. The AODs at 500 nm as well as ‘𝛽’ are found to be highly correlated, while ‘𝛼’ is found to be strongly anti-correlated with temperature and wind speed suggesting high AODs and turbidity but low concentration of fine particles during hot and windy days. With wind direction, the AOD and ‘𝛽’ are found to be strongly anti-correlated, while ‘𝛼’ is strongly correlated.
Volume 131, 2022
All articles
Continuous Article Publishing mode
Click here for Editorial Note on CAP Mode
© 2021-2022 Indian Academy of Sciences, Bengaluru.