TITLE:
Spatial and Temporal Variability of Total Column Ozone over the Indian Subcontinent: A Study Based on Nimbus-7 TOMS Satellite
AUTHORS:
Vazhathottathil Madhu
KEYWORDS:
Total Column Ozone, Quasi-Biennial Oscillation, Interannual Variability, Morlet Wavelet
JOURNAL NAME:
Atmospheric and Climate Sciences,
Vol.4 No.5,
November
26,
2014
ABSTRACT: The distribution and variability of ozone
is very important to the atmospheric thermal structures, and it can exert their
greater influence on climate. Present study is based on Nimbus-7 TOMS overpass
column ozone for a period of 14 years (1979-1992) over twelve selected Indian
stations from south to north latitude and it explores the spatial and temporal
variability of Total Column Ozone (TCO). For this investigation an advanced
statistical methods such as Factor Analysis and Morlet wavelet transform are
employed. Total column ozone variability over these stations is grouped into
two clusters (Eigen value greater than 1) by the Multivariate Factor analysis.
It is found that the Group I stations shows the same nature of variability
mainly due the first factor as the primarily loading and whereas as the Group
II stations shows the same nature of variability due to second factor as the
primary loading. The correlation value of TCO decreases from 0.9 to 0.32 as we
move from south to north stations (lower latitude to higher latitude). The
total column ozone over tropical stations is maximum during monsoon season with
peak in the month of June and that for the higher latitude stations is during
the pre-monsoon season. Annual average of TCO for tropical stations is about
265 DU and that for subtropical stations is about 280 DU and a difference of
15 DU is noted in the annual average of TCO between tropical and subtropical stations.
A large reduction in TCO is noted over the Indian subcontinent in the year
1985, the same year in which the ozone hole over Antarctica was discovered. It
is also found that two prominent oscillations are present in total column
ozone one with a periodicity of 16 to18 months and other with 28 to 32 months
(QBO periodicity) apart from the annual oscillations. These oscillations are
found to be significant at above 95% level of confidence when tested with Power
Spectrum method. Tropical TCO shows high concentration during the westerly
phase and low concentration during the easterly phase of the equatorial
stratospheric quasi-biennial oscillation.