1 Patterns of convection in Africa and opportunities for collaboration Arlene Laing National Center for Atmospheric Research MMM/ESSL/

2 MOTIVATION Prediction of warm season precipitation is encumbered on improving understanding of initiation and evolution of organized convection. Societal need for improved precipitation prediction in Africa. Radar-based studies in US found that organized convective precipitation displays coherence in propagation (Carbone et al 2002) Studies of East Asia, Australia, Europe used IR data to track cold cloud clusters and found similar coherence How similar or different is organized convection in Africa? What can be inferred about prediction of precipitation from the behavior of deep convection?How similar or different is organized convection in Africa? What can be inferred about prediction of precipitation from the behavior of deep convection?

3 Seasonal distribution of African MCCs Laing and Fritsch, 1993

4 Study Domains & Period Main Focus May - August 5-year (1999 to 2003) 2-year Sep-Oct: 1999, year Nov–Dec: 1999, 2003 Meteosat-7 IR, 30min May - Aug 0 20W 20E 20S 20N 0 40E Average Elevation 35S - 20S (km) Nov - Dec Sep-Oct Average Elevation 0- 20N (km)

5 Brightness temperatures (< 253K, 233K, 213K) identifies organized convection most likely to be precipitating Pixel colder than threshold constitutes ‘‘event’’ at given distance – time coordinate (Hovmoller space) Caveats: IR advantage: high temporal tracking capability Problems: Identification of warm rain, underestimation of early stage of convection, distinguishing between deep convection and thick cirrusMethods

6 Tropical N. Africa: 16 – 30 June K233K213K Coherence in propagation – like other warm season continental convection & precipitation

Seasonal & Diurnal Distribution Average Hourly Percentage of Cold Cloud, T bb < 253K Average Elevation 0-20N (km) PREFERRED ZONES Initiation in lee of high terrain Local & Propagating Convection Seasonal migration Land/Ocean Diurnal Cycles Peak Monsoon 1 Jul–15 Aug Pre- Monsoon 15 May–30 Jun

8 0 20W20E40 Average Elevation, 0-20N (km) EPISODES 16 – 30 June 1999 Mean Diurnal Cycle % of time with T bb < 233K 0 20W20E40 Average Elevation, 0-20N (km) UTC

9 Comparing Continents Region (Longitude of Domain) Span (km) Duration (h)Phase Speed All episodes (ms -1 ) Contiguous US (37deg) 838 (1 per day mean) 18.5 (1 per day mean) Median – 13.6 East Asia (50deg) 620( 1 per day mean) 11.6 (1 per day mean) Mean – 12.4 Europe (50 deg) Mean – Mean – 8.56Mean – Median – 13.6 Africa (60deg) Mean Median Mean – 25.5 Median – 18.0 Mean – 12.0 Median – 11.2

10 Link with other projects & programs African Monsoon Multidisciplinary Analysis (AMMA)

11 African Contacts & Institutions Amadou Gaye, UCAD, Senegal, Co-Chair, AMMA Water Cycle Debo Adeyawa, (Federal University of Technology, Akure, Nigeria) –Collaborator with Ed Zipser on studies of TRMM diurnal cycles and convective systems Arona Diedhiou, AGHRYMET, Niger, Co-Chair, PIAF

12 UCAR Institutions (AMMA Water Cycle) SUNY Albany, Chris Thorncroft Howard University, Greg Jenkins U of Oklahoma, Peter Lamb MIT, Fatih Eltahir MIT, Earle Williams U of North Dakota, Paul Kucera

13 SH AFRICA Summer (20S – 35S) 1100 UTC 9 Dec 1800 UTC 9 Dec 2000 UTC 9 Dec 0430 UTC 10 Dec Dec E20E30E40E 1100 UTC 9 Dec 1500 UTC 9 Dec 1800 UTC 9 Dec 2000 UTC 9 Dec 2330 UTC 9 Dec 0430 UTC 10 Dec

14 Links with other programs Peter Chen, WMO World Weather Watch –WMO Severe Weather Forecasting Demonstration Project (SWFDP), with a few National Meteorological Services, regional centers & centers that produce global products –“challenges we face … is to provide the necessary training to support and sustain the use of certain NWP products that are not being used there, or products that could be better "tuned" for better performance in this region” –Glad to hear of this initiative, sharing info with Dr. Jack Hayes, Director of World Weather Watch –Will use my research on southern African convection in project this year Chris Reason, University of Cape Town, South Africa

15 COMET Contribution Joint proposal with UNEP to the UN Foundation for enhancing environmental literacy in Africa –Use of broadcasters –Partnership with NEETF (National Env. Edu. Training Foundation) COMET Modules in wide use –With additional funds could adapt modules to be Africa-centered Tropical Meteorology Textbook (Laing and Evans)

16 Summary Tropical N. Africa Organized convection over Africa occur as coherent sequences Similar phase speeds to other continents although average zonal span and duration are greater (larger longitudinal domain) Large fraction of episodes initiate in the lee of high terrain Propagation leads to delayed-phase shift in diurnal maximum Convection occur with moderate vertical shear of zonal wind Without steering winds, longevity, and spatial span of events are greatly diminished, and significant propagation ceases Imagery shows evidence of gravity currents and mesoscale convective vortices (MCVs). Some MCVs became tropical cyclones close to west coast of Africa (e.g., Cindy, Gert, Alberto)

17 Summary: Mid-latitude S. Africa Similar coherent pattern of convection Episodes of organized convection are less frequent than other domains Phase speeds less than other continents High terrain aids in convective initiation Regime with propagation exhibit delayed-phase shift in diurnal max Examining westerly wind shear to determine influence on propagation (propagating vs non-propagating regimes)

18 Mean Diurnal Cycles (JJA) W20E Average Elevation, 0-20N (km) % of time T bb < 253K UTC UTC