Convective intensification induced by a descending dry

layer: a case study of CSIP IOP 9

Andrew Russell and Geraint VaughanCentre for Atmospheric Sciences

University of Manchester

1. CSIP – The Convective Storm Initiation Project

CSIP observational campaignwas a collaborative project

United Kingdom

• Universities of:* Reading* Leeds* Manchester* Salford* Bath

• The Met Office• Chilbolton Observatory

Germany

• Institut für Meteorologie und Klimaforschung (IMK), Karlsruhe

• Universität Braunschweig• GeoForschungsZentrum,

Potsdam

Courtesy of Cyril Morcrette

Courtesy of Cyril Morcrette

2. Synoptic Background

1645 UTCRainfall radar

IOP9: 18th July 2005

1645 UTCMSG visible

IOP9: 18th July 2005

1530 UTCCAMRa 3GHz

IOP9: 18th July 2005

MSG visible MSG WV

ECMWF PV TOMS O3

1200 UTC

MSG visible MSG WV

ECMWF PV TOMS O3

1200 UTC

MSG visible MSG WV

ECMWF PV TOMS O3

1200 UTC

MSG visible MSG WV

ECMWF PV TOMS O3

1200 UTC

3. Observations of the dry layer

GPS Water Vapour - Linkenholt

θw (ºC) and 10% Relative Humidity (RH) from

Radiosondes - SwanageSNR from wind profiling radar

– Linkenholt (plotted over Swanage sonde data)

IOP9: 18th July 2005

1645 UTC

LID

θw decreases θw decreases with height…with height…… … instability!instability!

3. How the convection was forced

1600 UTC

MSG visible MSG WV

ECMWF PV TOMS O3

1200 UTC

1200 UTC

ECMWF RH (shading) and T (contours)

1200 UTC

ECMWF PV (shading and contours) and θ (dashed contours)

For more thoughts on the upper-level origin of atmospheric lids, see my poster…

4. Conclusions

• Convective showers over southern England behind a cold front

• Dry intrusion overran moist surface layer resulting in potential instability

• Convection capped at 6 km by uppermost dry layer

• Interesting observations of the double descending layer, which had a role in both forcing and inhibiting the convection

Andrew RussellCentre for Atmospheric SciencesUniversity of Manchester

andrew.russell-2@manchester.ac.uk www.andrewrussell.co.uk