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| Titel |
Rain- vapour isotopic interaction over the south-west coast of India |
| VerfasserIn |
Lekshmy Palliyil Ravisankar, Midhun Madhavan, Ramesh Rengaswamy |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250106801
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| Publikation (Nr.) |
 EGU/EGU2015-6478.pdf |
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| Zusammenfassung |
| Boundary layer water vapor isotopic composition (δv) is an important factor that
controls the isotopic composition of evaporation flux and modulating the δ18O of tree
ring cellulose through plant physiological cycle. But due to the difficult sampling
procedure for water vapor, δv has rarely been quantified. Since many simple isotopic
models require δvas an input, mostly we assume that the water vapor is in isotopic
equilibrium with δof monthly rain (δr). Here we present simultaneous observations of
water vapour (~ 300 samples) and rainfall (~200 samples) isotopic ratios from two
stations in the south-west coast of India (both the stations are located in the west of
Western Ghats), sampled during April- October, 2012. Daily rain water and water
vapour (cryogenic trapping method) were collected according to the IAEA protocol
and the isotopic analyses (D and 18O) were done using a Thermo Fisher Delta V+
Isotope Ratio Mass Spectrometer. We observe that, water vapour and rain are close to
the equilibrium values during pre monsoon (April-May, É = δr - δv= 8.9 ± 1.4 ),
summer monsoon (June-September, É = 9.0 ± 1.8 ) and North- East (NE) monsoon
(October, É = 7.9 ± 2.9 ) seasons. However, some individual rain events show more
deviations from the equilibrium values. NE monsoon rainfall and water vapour are
isotopically more depleted in 18O compared to the pre monsoon and summer monsoon
seasons, in which the depletion is more in rain (~4 ) compared to water vapour
(~2 ). This is because of the 18O enrichment of ground level vapour due to local
evapo- transpiration (stations are at the leeward side of the Ghats), while rainfall is
directly formed from the NE monsoon clouds which is more depleted in 18O. These
results will be useful for the interpretation of δ18O of tree rings from south west. |
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