Regional Analysis of West African Monsoonal Convective

Systems During 2006

Nick Guy, Steven. A. Rutledge, and Brenda Dolan

Colorado State University

N/AMMA 2006 Observational Campaign

Radar Common Operating Period: 19 Aug – 16 Sep 2006

MIT Radar (UTC+1)Niamey, Niger

NPOL Radar (UTC+0)Kawsara, Senegal

TOGA Radar (UTC-1)Praia, Cape Verde

Evidence of propagating modes

• Disturbance generation over east Africa

• Propagates westward with various points of regeneration

• How does this contribute locally?

• What do local diurnal cycles look like at these three locations?

Averaged over 12-17°N

Environmental CharacteristicsCAPE CIN

0 – 6 km Shear

VAD Analysis

E

NE

E SW

NE

SE E

Con Con ConDiv Div Div

Precipitation Feature Analysis

• Grouped precipitation features– MCS and Sub-MCS spatial scale

• Producing 1-hour statistics• Common time binned into hour of

day to produce diurnal representation

MCS Sub-MCS

Season

Diurnal Characteristics

MCS Convective MCS Stratiform

Precipitation

Convectivevs.

Stratiform

Vertical Structureof total

common period

Total Total

Wave vs. No Wave

• Common time frame shows a distinct separation of characteristics due to convective spatial scale

• Deep convection has been shown to be modulated by African Easterly Waves

• What differences are seen at the local scale?• Partition data in terms of wave and non-wave

influence • Berry et al. 2007 algorithm definition of trough

tracking used

Vertical Reflectivity

Diurnal Characteristics

Precipitation

ConvectiveVs.

Stratiform

MCS Feature Size

AEW No Wave

Summary• Characteristic zonal differences in convection

are observed between the three unique sites attributable to:– AEW activity– Zonal variability environmental characteristics

• Continental site shows most favorable environment for linearly organized convection, though the coastal site also displays this behavior

• Coastal site maintains most abundant reservoir of available convective energy

• Large cap and shear at continental site results in explosive organized convective growth

• Continental and maritime sites show similar vertical growth, though the continental site exhibits much larger reflectivity values at low levels

Summary• Wave forcing at the continental and

coastal sites show the greatest differences in stratiform extent and precipitation

• Wave organization results in greater precipitation feature size and therefore precipitation

• Vertical growth does not show strong wave dependence at the maritime and coastal sites

• Diurnal peaks show variability in distribution and magnitude due to “wave influence”