To what extent could water isotopic measurements help us understand model biases in the water cycle over Western Siberia
We evaluate the isotopic composition of water vapor and precipitation simulated by the LMDZ (Laboratoire de Météorologie Dynamique-Zoom) GCM (General Circulation Model) over Siberia using several data sets: TES (Tropospheric Emission Spectrometer) and GOSAT (Greenhouse gases Observing SATellite) sat...
| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2014-09-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/14/9807/2014/acp-14-9807-2014.pdf |
| Summary: | We evaluate the isotopic composition of water vapor and precipitation
simulated by the LMDZ (Laboratoire de Météorologie Dynamique-Zoom) GCM
(General Circulation Model) over Siberia using several data sets: TES
(Tropospheric Emission Spectrometer) and GOSAT (Greenhouse gases Observing
SATellite) satellite observations of tropospheric water vapor, GNIP (Global
Network for Isotopes in Precipitation) and SNIP (Siberian Network for
Isotopes in Precipitation) precipitation networks, and daily, in situ
measurements of water vapor and precipitation at the Kourovka site in Western
Siberia. LMDZ captures the spatial, seasonal and daily variations reasonably
well, but it underestimates humidity (<i>q</i>) in summer and overestimates
δ<i>D</i> in the vapor and precipitation in all seasons. The performance of
LMDZ is put in the context of other isotopic models from the SWING2 (Stable
Water Intercomparison Group phase 2) models. There is significant spread
among models in the simulation of δ<i>D</i>, and of the
δ<i>D</i>-<i>q</i> relationship. This confirms that δ<i>D</i>
brings additional information compared to <i>q</i> only. We specifically
investigate the added value of water isotopic measurements to interpret the
warm and dry bias featured by most GCMs over mid and high latitude continents
in summer. The analysis of the slopes in δ<i>D</i>-<i>q</i> diagrams and
of processes controlling δ<i>D</i> and <i>q</i> variations suggests that
the cause of the dry bias could be either a problem in the large-scale
advection transporting too much dry and warm air from the south, or too
strong boundary-layer mixing. However, δ<i>D</i>-<i>q</i> diagrams using
the available data do not tell the full story. Additional measurements would
be needed, or a more sophisticated theoretical framework would need to be
developed. |
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| ISSN: | 1680-7316 1680-7324 |