Exposure-plant response of ambient ozone over the tropical Indian region Indian Institute of Tropical Meteorology, 411008 Pune, India
Received: 27 Nov 2008 – Published in Atmos. Chem. Phys. Discuss.: 09 Feb 2009 – Published: 29 Jul 2009Abstract. A high resolution regional chemistry-transport model has been used to study
the distribution of exposure-plant response index (AOT40, Accumulated
exposure Over a Threshold of 40 ppb, expressed as ppb h) over the Indian
geographical region for the year 2003 as case study. The directives on ozone
pollution in ambient air provided by United Nations Economic Commission for
Europe (UNECE) and World Health Organization (WHO) for vegetation protection
(AOT40) have been used to assess the air quality. A substantial temporal and
spatial variation in AOT40 values has been observed across the Indian
region. Large areas of India show ozone values above the AOT40 threshold
limit (3000 ppb h for 3 months). Simulated AOT40 values are found to be
substantially higher throughout the year over the most fertile Indo-Gangetic
plains than the other regions of India, which can have an adverse effect on
plants and vegetation in this region. The observed monthly AOT40 values
reported from an Indian station, agree reasonably well with model simulated
results. There is an underestimation of AOT40 in the model results during
the periods of highest ozone concentration from December to March. We find
that the simulated AOT40 target values for protection of vegetation is
exceeded even in individual months, especially during November to April.
Necessary and effective emission reduction strategies are therefore required
to be developed in order to curb the surface level ozone pollution to
protect the vegetation from further damage in India whose economy is highly
dependent on agricultural sector and may influence the global balance.
Citation: Deb Roy, S., Beig, G., and Ghude, Sachin D.: Exposure-plant response of ambient ozone over the tropical Indian region, Atmos. Chem. Phys., 9, 5253-5260, doi:10.5194/acp-9-5253-2009, 2009.