Synoptic, Topographic, and Diurnal Effects Synoptic, Topographic, and Diurnal Effects on Summer Convection in South Americaon Summer Convection in South America

Ulrike RomatschkeUlrike RomatschkeUniversity of Washington, University of Vienna

Robert A. Houze Jr., Socorro Medina, Kristen Rasmussen Robert A. Houze Jr., Socorro Medina, Kristen Rasmussen University of Washington

ICAM, Rastatt, Germany, May 15, 2009

Ulrike RomatschkeUlrike Romatschke, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009

Sponsored in part by:

NSF Award# ATM-0505739

NSF Award# ATM-0820586

NASA Award# NNX07AD59G

Ulrike RomatschkeUlrike Romatschke, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009

ObjectivesInvestigate Distribution of convection

Find regions ofmaximum convective intensitymaximum precipitation

Forcing of convection bySynoptic conditionsTopographyDiurnal heating

Connection with precipitation climatology

Ulrike RomatschkeUlrike Romatschke, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009

DataData

Tropical Rainfall Measuring Mission Tropical Rainfall Measuring Mission Precipitation Radar (TRMM PR)Precipitation Radar (TRMM PR) 3D reflectivity3D reflectivity

10 years (December 1998 – February 2008)10 years (December 1998 – February 2008) Summer months: December, January, FebruarySummer months: December, January, February

NCEP reanalysisNCEP reanalysis Large-scale environmentLarge-scale environment

Ulrike RomatschkeUlrike Romatschke, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009

Classification of radar echo structures Classification of radar echo structures within convective systems within convective systems

Deep Convective CoresDeep Convective CoresContiguous convective echo Contiguous convective echo ≥ ≥ 40 dBZ and 40 dBZ and ≥≥ 10 km in 10 km in

heightheight

Wide Convective CoresWide Convective CoresContiguous convective echo Contiguous convective echo ≥ 4≥ 40 dBZ and 0 dBZ and ≥≥ 1000 km 1000 km² ²

in areain area

Broad Stratiform RegionsBroad Stratiform RegionsContiguous stratiform echo Contiguous stratiform echo ≥≥ 50 000 km 50 000 km² in area² in area

Ulrike RomatschkeUlrike Romatschke, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009

Distribution of radar echo structures

Deep Deep convectivconvective corese cores

Broad Broad stratiform stratiform regionsregions

Wide Wide convective convective

corescores

Precip. Precip. climatologyclimatology

Ulrike RomatschkeUlrike Romatschke, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009

Regions of interest

Foothills Foothills NorthNorth

La Plata La Plata BasinBasin

Foothills Foothills South South

Ulrike RomatschkeUlrike Romatschke, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009

Synoptic forcingSynoptic forcing

Ulrike RomatschkeUlrike Romatschke, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009

500 mb geopotential height anomaly500 mb geopotential height anomaly Surface pressure anomalySurface pressure anomaly

Composites, wide convective cores, La Plata BasinComposites, wide convective cores, La Plata Basin

Surface winds (~02 LT)Surface winds (~02 LT)

Foothills South, La Plata Basin

[mb][mb]

Ulrike RomatschkeUlrike Romatschke, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009

500 mb geopotential height anomaly500 mb geopotential height anomaly Surface pressure anomalySurface pressure anomaly

Composites, wide convective cores, Foothills NorthComposites, wide convective cores, Foothills North

Surface winds (02 LT)Surface winds (02 LT)

Foothills North

[mb][mb]

Ulrike RomatschkeUlrike Romatschke, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009

Diurnal and Topographic Diurnal and Topographic forcingforcing

Ulrike RomatschkeUlrike Romatschke, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009

Foothills South, La Plata BasinDeep convective cores

Wide convective cores

Broad stratiform regions

Ulrike RomatschkeUlrike Romatschke, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009

Foothills North

Wide convective

cores

Broad stratiform regions

Ulrike RomatschkeUlrike Romatschke, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009

Deep Convective cores

06 UTC 06 UTC ~02 LT~02 LT

00 UTC 00 UTC ~20 LT~20 LT

18 UTC 18 UTC ~14 LT~14 LT

12 UTC 12 UTC ~08 LT~08 LT

Ulrike RomatschkeUlrike Romatschke, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009

Wide convective cores

06 UTC 06 UTC ~02 LT~02 LT

00 UTC 00 UTC ~20 LT~20 LT

18 UTC 18 UTC ~14 LT~14 LT

12 UTC 12 UTC ~08 LT~08 LT

Ulrike RomatschkeUlrike Romatschke, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009

Broad stratiform regions

06 UTC 06 UTC ~02 LT~02 LT

00 UTC 00 UTC ~20 LT~20 LT

18 UTC 18 UTC ~14 LT~14 LT

12 UTC 12 UTC ~08 LT~08 LT

Ulrike RomatschkeUlrike Romatschke, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009

Foothills South, La Plata Basin

06 UTC 06 UTC ~02 LT~02 LT

00 UTC 00 UTC ~20 LT~20 LT

18 UTC 18 UTC ~14 LT~14 LT

12 UTC 12 UTC ~08 LT~08 LT

10 m s10 m s-1-1

Composite winds and divergence, wide convective cores, La Plata BasinComposite winds and divergence, wide convective cores, La Plata Basin

DivergenceDivergence

Ulrike RomatschkeUlrike Romatschke, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009

Foothills North

06 UTC 06 UTC ~02 LT~02 LT

00 UTC 00 UTC ~20 LT~20 LT

18 UTC 18 UTC ~14 LT~14 LT

12 UTC 12 UTC ~08 LT~08 LT

10 m s10 m s-1-1

Composite winds and divergence, wide convective coresComposite winds and divergence, wide convective cores

DivergenceDivergence

Ulrike RomatschkeUlrike Romatschke, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009, University of Washington, University of Vienna, ICAM, Rastatt, Germany, May 15, 2009

Conclusions

Synoptic low location criticalMoisture transport by low-level jet from tropics to

subtropics Diurnal heating

Daytime deep and wide convective cores in Foothills South triggered by lifting over lower slopes

Divergence at the Foothills North prevents convection

Nocturnal coolingDownslope flow and convergence at the foothills

leads to maxima in wide convective cores and broad stratiform regions.