Precipitation isoscape of high reliefs: interpolation scheme designed and tested for monthly resolved precipitation oxygen isotope records of an Alpine domain
Stable oxygen isotope composition of atmospheric precipitation (δ<sup>18</sup>O<sub>p</sub>) was scrutinized from 39 stations distributed over Switzerland and its border zone. Monthly amount-weighted δ<sup>18</sup>O<sub>p</sub> valu...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2014-02-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/14/1897/2014/acp-14-1897-2014.pdf |
| Summary: | Stable oxygen isotope composition of atmospheric precipitation (δ<sup>18</sup>O<sub>p</sub>) was scrutinized from 39 stations distributed over
Switzerland and its border zone. Monthly amount-weighted δ<sup>18</sup>O<sub>p</sub> values averaged over the 1995–2000 period showed the
expected strong linear altitude dependence (−0.15 to −0.22‰ per
100 m) only during the summer season (May–September). Steeper gradients
(~ −0.56 to −0.60‰ per 100 m) were observed for winter
months over a low elevation belt, while hardly any altitudinal difference was
seen for high elevation stations. This dichotomous pattern could be explained
by the characteristically shallower vertical atmospheric mixing height during
winter season and provides empirical evidence for recently simulated effects
of stratified atmospheric flow on orographic precipitation isotopic ratios.
This helps explain "anomalous" deflected altitudinal water isotope profiles
reported from many other high relief regions. Grids and isotope distribution
maps of the monthly δ<sup>18</sup>O<sub>p</sub> have been calculated over the
study region for 1995–1996. The adopted interpolation method took into
account both the variable mixing heights and the seasonal difference in the
isotopic lapse rate and combined them with residual kriging. The presented
data set allows a point estimation of δ<sup>18</sup>O<sub>p</sub> with
monthly resolution. According to the test calculations executed on subsets,
this biannual data set can be extended back to 1992 with maintained fidelity
and, with a reduced station subset, even back to 1983 at the expense of faded
reliability of the derived δ<sup>18</sup>O<sub>p</sub> estimates, mainly in
the eastern part of Switzerland. Before 1983, reliable results can only be
expected for the Swiss Plateau since important stations representing eastern
and south-western Switzerland were not yet in operation. |
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| ISSN: | 1680-7316 1680-7324 |