TITLE:
Temporal Distribution of Total Column Ozone over Cochin—A Study Based on in Situ Measurements and ECMWF Reanalysis
AUTHORS:
Vazhathottathil Madhu, Karthika Gangadharan
KEYWORDS:
Total Column Ozone (TCO), Solar Cycle, Seasonal Variability, Quasi-Biennial Oscillation
JOURNAL NAME:
Open Journal of Marine Science,
Vol.6 No.2,
March
9,
2016
ABSTRACT: The variability of
Atmospheric ozone is very important to understand the radiative balance of the
earth-atmospheric system and climate change. In order to understand the
temporal variability of total column ozone (TCO) over the coastal station
Cochin (9.95°N, 76.27°E), we used the ECMWF (European Centre for Medium-Range
Weather Forecasts) reanalysis TCO and ground based measurements using Microtop
II Sun Photometer (Ozonometer). The trend, seasonal changes and diurnal
variation of ozone concentration have been studied in detail for the period
1981-2014. Cochin is a tropical coastal station with tropical monsoon climate
and hence we examined the variability of TCO during pre-monsoon (March-May),
monsoon (June-September) and post monsoon (October-December) seasons.
Significant variations are noted in the TCO for the different seasons during
the period of study. Based on the measurements and analysis, it is observed
that TCO is maximum during monsoon and minimum during pre- and post-monsoon. We
computed the TCO climatology for pre-monsoon (262.0 DU), monsoon (275 DU) and
post-monsoon (253 DU) seasons and found that TCO shows a decadal trend (solar
cycle). During monsoon season TCO varies with an increase of approximately 14
DU from the pre-monsoon value and a decrease of 22 DU from the post-monsoon
value. The increase in TCO concentration during monsoon may be attributed to
the monsoonal wind circulations and organized convection. The validation of
ECMWF TCO with in situ measurements using Microtop II
Ozonometer has been carried out for the year 2015 and found that the values are
positively correlated. The diurnal variability of TCO was examined for vernal
and autumnal equinox days and noticed the change in variability.