The measurements using a ground based multi wavelength radiometer
(MWR) at Mohal (31°54′N, 77°07′E, 1154 m AMSL) in the Kullu
valley of Northwestern Himalayan region show that the spectral aerosol
optical depth (AOD) and turbidity coefficient, β, are high in summer,
moderate in monsoon season, low i...
The measurements using a ground based multi wavelength radiometer
(MWR) at Mohal (31°54′N, 77°07′E, 1154 m AMSL) in the Kullu
valley of Northwestern Himalayan region show that the spectral aerosol
optical depth (AOD) and turbidity coefficient, β, are high in summer,
moderate in monsoon season, low in winter and lowest in autumn, while
wavelength exponent, α, has an opposite trend. Average annual value of
AOD at 500 nm is 0.24±0.01, 0.43±0.02, and 0.28±0.02; that of β is
0.14±0.01, 0.22±0.02, and 0.17±0.03; and that of α is 1.06±0.09,
1.16±0.10, and 0.86±0.13, respectively, for clear, hazy and partially clear
sky days. The considerably greater value of β on hazy days indicates
more coarse particles in mountain haze. The fractional asymmetry factor
(AF) is more negative in summer and autumn months. The AOD and β
have significantly positive correlation with temperature and wind speed,
suggesting high AODs and turbidity on hot and windy days.