Observing Water Vapor with GNSS Radio Occultation Data
Presenter:
Ulrich Foelsche
Institute of Physics and Wegener Center for Climate and Global Change, University of Graz, Austria
Institute of Physics and Wegener Center for Climate and Global Change, University of Graz, Austria
Talk
GNSS RO data contain important water vapor information in the (lower) troposphere.
We looked at two specific phenomena, associated with considerable water vapor transport, which are notorious for producing extreme precipitation.
(1) \"Vb cyclones\", and in particular \"Genoa Lows\" advect high amounts of moisture from the Mediterranean Sea to Central Europe.
They constitute only a few percents of all Central European Cyclones, but are responsible for an important fraction of extreme large-scale precipitations events, leading to intense flooding.
(2) Atmospheric rivers (ARs) are comparatively narrow (~500 km wide) and long (~2000 km) corridors of intense water vapor transport, situated on the warm side of polar cold fronts.
They are responsible for the majority of the poleward water vapor transport across the mid latitudes and for extreme precipitation events, including some of the most important European ones in recent years.
Although the narrow bands of ARs are challenging for any limb-sounding technique, we can clearly identify them in RO data.
By analyzing differences between daily values and long-term averages, we can clearly see the temporal evolution and vertical structure of ARs, providing a nice complement to data from microwave and infrared sounders, which give a good picture of the integrated water vapor content and the horizontal structure, but very little information about the vertical structure.
The results about \"Vb cyclones\" are preliminary, but indicate a very similar behavior.
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