Publication Date:
2023-07-26
Description:
Dry intrusion (DI) air streams typically comprise the cold and dry sector of extratropical cyclones. These air parcels descend slantwise from the midlatitude upper troposphere towards the surface in lower latitudes, where the airstreams typically fan out behind the cyclone’s trailing cold front. In this talk I will review recent results based on a Lagrangian-based global climatology of DIs using ECMWF reanalysis data, allowing the quantification of the intrusions’ occurrence frequencies and association with extreme weather. Using representative case studies and longer-term climatologies we understand that DI air starts its descent from the upper troposphere behind midlatitude troughs of Rossby waves. When interacting with cyclones in the storm tracks, they are associated with strong cold fronts in the cyclone southwest quadrant (in the northern hemisphere) and with marked anomalies in the lower troposphere. Namely, dry and cold anomalies prevail, together with strong winds and destabilized lower troposphere. The modification of the lower troposphere by DIs entails strong associations with a diverse set of weather extremes, from heavy precipitation ahead of the dry air, strong winds and extreme cold temperatures, to wildfires in southeast Australia and Saharan dust storms. Finally, we note that surface extremes associated with DIs may extend beyond the midlatitudes, into subtropical and tropical regions.
Language:
English
Type:
info:eu-repo/semantics/conferenceObject
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