Regional-scale analysis of convective systems in the

2006 West African Monsoon season

Nick GuySteven Rutledge, Rob Cifelli,

and Timothy LangColorado State University

Tom RickenbachEast Carolina University

21 July 2009

Motivations

• Categorize MCS- and sub-MCS -scale convective systems in 2006 monsoon season

• Obtain statistics for MCS- and sub-MCS -designated convection on a regional scale

• Use of multiple platforms for analysis and verification of mesoscale model simulations

Radar LocationsTOGA

NPOL

MIT

Common Operating Period: 15 August – 16 September 2006

Seasonal Stats # Mean Time (hrs) Total Rain Fraction

Total Area Fraction

TOGA MCS 6 10.8 0.670 0.395

Maritime Sub-MCS 28 6.5 0.33 0.605

NPOL MCS 12 9.5 0.733 0.576

Coastal Sub-MCS 45 5.9 0.267 0.424

MIT MCS 37 12.1 0.923 0.873

Continental Sub-MCS 82 5.2 0.077 0.127

Precipitation Climatology

Anomaly – Deviation from TRMM climatological precipitation mean

WAM Region

TOGA (Maritime)[Mean ~ 1.0]

NPOL (Coastal)[Mean ~ 0.9]

MIT (Continental)[Mean ~ 1.1]

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Seasonal Rainrates

Good trend agreement between ground and satellite products

Track bands of precip associated with disturbances

1

2

Lightning Climatology

NPOL

MCS and Sub-MCS StatisticsSystem Stats Mean Conv

FractionMean CAPE

(Jkg-1)WWLLN

# Rain Area Before

Arrival

During Flashes

(CG)

TOGA MCS 6 0.614 0.149 1115 1006 107

Maritime Sub-MCS 28 0.613 0.126 658 654 1

NPOL MCS 12 0.688 0.187 1630 1299 98

Coastal Sub-MCS 45 0.759 0.238 1665 1528 14

MIT MCS 37 0.634 0.199 2276 1625 75

Continental Sub-MCS 82 0.676 0.253 2037 2221 3

Case StatisticsMCS Case Stats Mean Conv

FractionMean CAPE

(Jkg-1)WWLLN Tb < 233 K

Rain Area Before

Arrival

During Flashes

(CG)

Fraction

TOGA Case 1 0.794 0.140 1697 1544 385 0.281

Maritime Case 2 0.743 0.238 1585 779 10 0.175

NPOL Case 1 0.710 0.187 2712 1989 1 0.299

Coastal Case 2 0.605 0.173 1616 929 150 0.555

MIT Case 1 0.532 0.110 2446 903 220 0.356

Continental Case 2 0.736 0.248 2382 2344 11 0.320

Vertical Structure

Summary

• 2006 WAM season is “average” – Via TRMM rainfall and lightning climatology (domain: 0-30N,

30W-30E)

• Regional analysis defined via 3 radar sites represents continental, coastal, and maritime locations– TOGA (maritime) domain average for precipitation– NPOL (coastal) domain below average for precipitation– MIT (continental) domain slightly above average for precipitation– MCS scale events constitute greater fraction of rainfall inland

• Large precipitation events tracked across longitudinal domain

• No apparent first order correlation to environmental variables – must look at wave forcing as well

• Vertical structure varies with region, resembling typical “continental” and “maritime” structures

Future Work• AEWs: Define and calculate associated

convective statistics for each domain• Case Studies:

– 5-10 Sep 2006 possibly associated with non-developing wave

– 8-12 Sep 2006 possibly associated/interacts with wave that produced Hurricane Helene

– 12-14 Sep 2006

• Closer look at the satellite vs. ground products relationship

• Work with NASA Goddard Space Flight Center (Greenbelt, MD) to assess mesoscale model simulations of 2006 WAM events

Wave Passages

Wave definitions from Janicot et al (2008)