Abstract
The total column aerosol optical depth, ozone and water vapor using a MICRO-processor based Total Ozone Portable Spectrometer (MICROTOPS II) and its sun photometer version have been routinely measured at the Indian Institute of Tropical Meteorology (IITM), Pune (18° 32' N, 73° 51' E, 559 m above mean sea level), India, with a view to establish an aerosol climatology over this fast growing tropical urban station. This paper focuses on spectral-temporal variations, inter-annual variability and long-term trends in the above aerosol and pre-cursor gas distributions over Pune. Besides a strong wavelength dependence of aerosol optical depth (AOD), the radiometer derived total column ozone values are found to correlate well with those estimated from the NASA’s Earth Probe, Total Ozone Mapping Spectrometer (TOMS) satellite observations during the study period. The results also indicate a decreasing trend in all the above parameters, possibly due to absorbing anthropogenic aerosols during the study period, and lower Angstrom exponent, implying the prevalence of coarse-mode aerosol particles, originating from marine air mass, from around May to July, which is consistent with the ratio between the optical depths measured at 1020 and 380 nm.
Highlights
There has been mounting evidence of the importance of both natural and anthropogenic aerosols, in the context of climate change, through their influence on formation of clouds, their effect on minor species concentration and their potential to scatter and absorb incoming solar radiation (Charlson et al 1992)
We present the results of the synthesis of this extensive database, focusing on the long-term trends in the spectraltemporal variations in aerosol optical depth (AOD), total column ozone (TCO) and precipitable water content (PWC)
We focus our analysis primarily on the spectral-temporal variations of AOD, TCO and PWC during the winter monsoon months of December-May when the air flow is primarily from the northeast direction
Summary
There has been mounting evidence of the importance of both natural and anthropogenic aerosols, in the context of climate change, through their influence on formation of clouds, their effect on minor species concentration and their potential to scatter and absorb incoming solar radiation (Charlson et al 1992). A wide variety of aerosol, ozone and water vapor products have been routinely measured using a ground-based, multi-filter (covering from UV to NIR wavelength region) solar radiometers at the Indian Institute of Tropical Meteorology (IITM), Pune 73o 51' E, Altitude 559 m), India These products include column-integrated aerosol optical depth (AOD), size distribution (ASD), ozone (TCO) and precipitable water content (PWC). In this communication, we present the results of the synthesis of this extensive database, focusing on the long-term trends in the spectraltemporal variations in AOD, TCO and PWC. We present the inter-annual variability of these parameters with a particular emphasis on the winter (urban / continental environment) and summer (maritime environment) monsoon periods since aerosols over this experimental station behave altogether differently and quite interestingly during these seasons
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