Ozone observations taken during the past 23–45 years by Dobson spectrophotometer at six stations of India have been analyzed to examine its long‐term trend over this subcontinent. These stations are Kodaikanal (10°N, 77°E), Pune (18°N, 74°E), Mount Abu/Ahmedabad (24°N, 72°E), Varanasi (25°N, 82°E), New Delhi (28°N, 77°E), and Srinagar (34°N, 74°E). An increasing trend of this species over the years has been noticed at all the places, except at Varanasi, where a decreasing trend has been found. The Nimbus 7 total ozone mapping spectrometer data at all the six stations have been compared with the Dobson data. Good agreement is found at all the stations except at Kodaikanal and Ahmedabad. The cause of these trends could be attributed, partly, to the trends of ozone in the troposphere.
A solar eclipse occurred across India on October 24, 1995. Vertical ozone column was measured at New Delhi (28.4°N, 77.1°E) by a Brewer spectrometer during this event. We found that at the time of maximum obscuration of the Sun the ozone column decreased by about 25 Dobson units (DU) from its preeclipse value. These results are compared with the measurements obtained elsewhere in India by other techniques during the same event. The NO 2 slant column density measured at Ahmedabad (23.0°N, 72.4°E) by visible absorption spectroscopy showed a wavelike variation during the eclipse. These variations did not follow the variation of the obscuration of the Sun during the eclipse. Correlation between ozone column, UV flux, and NO 2 column could not be established because observations were not taken at sufficiently close intervals.
Radiosonde observations taken during the past 32 years at New Delhi (28°N, 77°E) and 26 years at Thiruvananthapuram (8°N, 76°E) have been analyzed to examine the long‐term trend of tropopause height (TPH) and tropopause temperature (TPT) at these two stations. It appears that TPH is increasing and TPT is decreasing over the years. The trend of change is not same throughout the period of study. Considering the whole period of data we find that the increase of TPH is in the range of +0.57 to +1.13%/decade and the decrease of TPT is in the range range of −0.53 to −0.94%/decade. Qualitatively this is explainable with the decreasing trend of ozone in the stratosphere.
A solar eclipse occurred over Ahmedabad, India (23°N, 72°E) on 24 October 1995. We measured the vertical column abundance of ozone during this event using a Dobson spectrophotometer. We found that a sharp fall in the ozone column began from its normal value ∼15 minutes before the maximum obscuration (MO) of the sun, followed by a sharp rise ∼10 minutes after the MO. About 15 minutes after the MO, ozone column returned to normal values, but a wavelike fluctuation was still seen.
'%3e%3ccircle r='20' fill='%23008'/%3e%3ccircle r='17.5' fill='%23fff'/%3e%3ccircle r='3.5' fill='%23008'/%3e%3cg id='d'%3e%3cg id='c'%3e%3cg id='b'%3e%3cg id='a' fill='%23008'%3e%3ccircle r='.875' transform='rotate(7.5 -8.75 133.5)'/%3e%3cpath d='M0 17.5.6 7 0 2l-.6 5L0 17.5z'/%3e%3c/g%3e%3cuse xlink:href='%23a' transform='rotate(15)'/%3e%3c/g%3e%3cuse xlink:href='%23b' transform='rotate(30)'/%3e%3c/g%3e%3cuse xlink:href='%23c' transform='rotate(60)'/%3e%3c/g%3e%3cuse xlink:href='%23d' transform='rotate(120)'/%3e%3cuse xlink:href='%23d' transform='rotate(-120)'/%3e%3c/g%3e%3c/svg%3e)