Measurement of Columnar Aerosol, Ozone and Precipitable Water at Some High Altitude Sites in North India

Multi-wavelength sunphotometric observations have been collected at a few high altitude remote locations in North India during 20-31 May 2000. Columnar Aerosol Optical Depth (AOD) at six wavelengths in the 380-1020 nm range, ozone and precipitable water have been collected at five locations. Similar observations have also been made at New Delhi, an urban location in nearly the same longitude but about 4° south of the above stations, for comparison during 2-5 June 2000. AODs are the smallest at the most remote locations of Rohtang Pass and Madhi. Aerosol loading over New Delhi is on an average 4 times that observed at the remote locations. Aerosol size distributions at these locations showed both mono-modal and bi-modal size distributions. Time evolutions of aerosol size distribution at Mohal, Kothi and New Delhi revealed interesting features. Both ozone and precipitable water showed good inverse relationship with station altitude. Average columnar content of ozone at New Delhi is higher by 37 DU from that for all the remote locations. Rohtang Pass at the altitude of over 4100 m showed a very dry atmosphere with precipitable water values almost 1-2 orders of magnitude lesser than that at New Delhi. The high altitude locations of Mohal and Kothi show evidence of influence of human activity on the observed parameters