Abstract:
Ozoneisa gaswithits moleculecontainingthreeoxygenatoms,blue in colourandhas a
strongpungentodor. The depletion of ozone layer is a global issue and not just a problem
limitedto the countries in the polar region. Concern about the ozone depletion has an
obviousbasis; the ozone layer reduces the amount of harmful UV-B radiation in the
wavelengthrange of 280-315 nm from the sun that reaches the earth surface. Total
amountof ozone molecules occupying a column overhead, widely known as the ozone
columndensity, is measured in many countries all over the world to understand the
amountof harmfulUV-B radiation reaching to the earth surface and to study the recovery
rateof depletedozone layer.
Thisstudy describes an attempt made to study the ozone columnar density in various
locationsin Sri Lanka. To the best of our knowledge this is the first time that such a
groundbased study has been carried out in Sri Lanka. Measurements were conducted in
sixplacesColombo, Galle, Hambanthota , Monaragala , Diyatalawa and Kandy during
theperiodNovember 2002 to May 2003.
A MICROTOPII 5-channel Ozone Monitor & Sun Photometer tested and calibrated
usingDobson Spectrometer was used for the measurement. The instrument measures
directsolar radiation at 300.0, 305.5, and 312.5 nm windows and calculate the ozone
columndensity in Dobson Units. Hourly ozone column density data between 0800 h to
1700h were obtained and downloadedto a computer connectedto the instrument.
Accuratelocation parameters needed for ozone calculation were obtained using a GPS
instrument.Data were analyzed using Minitab Statistical package.
Thehighestozone density was observed at the noon and the results tally with those of
internationalmeasurements. The average ozone columnar density value over Sri Lanka
obtainedfor these seven month period was (2831:20) DU with maximum value 385 DU
recordedin June and minimum 215 DU in February. The monthly variation of ozone
columnardensitymeasured over Sri Lanka is found to be tally with that of satellite data
