African Regional Committee (Prepared by Aida Diongue-Niang and Benjamin Lamptey)

Transcription

1 WORLD METEOROLOGICAL ORGANIZATION COMMISSION FOR ATMOSPHERIC SCIENCES INTERNATIONAL CORE STEERING COMMITTEE FOR THORPEX Ninth Session Geneva (21 22 September 2011) CAS/ICSC-9/DOC4.1 (13 VI.2011) Item: 4.1 African Regional Committee (Prepared by Aida Diongue-Niang and Benjamin Lamptey) 1. Introduction This report provides a brief description of WWRP/THORPEX Africa. It is intended to inform the community on the past achievements and activities for Achievements After completion and dissemination of the Science and Implementation Plans to all African Meteorological Services inviting them to nominate national focal points, an initial workshop on High-Impact Weather (HIW) Predictability and Information System for Africa and African forecasters handbook was held in October 2009 at the United Nations Educational Scientific and Cultural Organization funded International Centre for Theoretical Physics (UNESCO/ICTP) in Trieste, Italy. The workshop aimed at providing momentum to THORPEX-Africa activities related to the HIW information system and assessment of forecasting system performance for African HIW. It was decided that while seeking for funding, the work should start in parallel with a few selected case studies (on a sub-regional basis; north, west, central, east, southern Africa) for which data collection (both weather and impact data) and data storage in the information system on one hand and model assessment to predict high-impact weather on the other hand will be performed. 1) The development of an African High impact weather information system The aim of the HIW Information System was to collect HIW events in the past two decades (i.e to 2010) and ongoing HIW events with a user friendly interface for analysis, processing and visualisation to facilitate integrated and multidisciplinary studies. It has been decided to start the activity with an interim prototype database with few selected case studies, the same as the ones targeted for the predictability studies here after. This will be used as a pilot demonstration to later build a comprehensive information system given funding opportunities. NHMSs national representatives involved in predictability studies committed their services to provide previously unavailable data (in situ data, forecast reports) to the new database and to gather impact data related to selected events. Others data (e.g. satellite, THORPEX Interactive Global Grand Ensemble (TIGGE) data) could be pointed by a referral; outcomes of research on the selected case studies will feed back the database. So far, some countries in West Africa and East Africa provided rainfall data related to the events. One Terabyte (1 TB) of disk space has been allocated by ICTP but there is the need to design the database and frame the associated metadata. The way the database should be designed was widely discussed during the October 2009 THORPEX-Africa workshop at ICTP. ICTP can help build the database that can be transferred to another African centre. This will require a person dedicated for this purpose who can go and work at ICTP as a visitor for a specified period of time. 2) Assessment of forecasting system performance for African high-impact weather (HIW) A workplan to handle HIW predictability studies has been detailed and proposed to THORPEX national focal points, coordinators of case studies and Regional Committee

2 CAS/ICSC-9/Doc.4.1, p. 2 members after the THORPEX-Africa workshop at ICTP. Here are the different phases and stages of the workplan: Phase 1: High-impact Weather Event Description Step 1: Synoptic Analysis of the selected high-impact event by focal points, coordinated at sub-regional level, to study its genesis, development, decay, the key atmospheric players in term of dynamics and thermodynamics, the sensible weather associated but also the impacts. Step 2: Extremeness of the event: aimed at analysing how extreme is the event regarding the available records; what makes the event exceptional in terms of intraseasonal and interannual variation; how is the mean season compared to climatology. Step3: Conceptual model of the high-impact weather event after performing a deeper analysis of the situation in order to understand local, regional and global processes involved at synoptic, intraseasonal, seasonal timescales. Phase 2: Verification of Forecast skill Step 1: Verification of forecasts issued by forecasters in order to measure how accurate was the forecast of the event. Step 2: Assessment of deterministic models to investigate the capacity of the models to predict the event for different lead times, with different models Step3: Assessment of ensemble models with regards the capacity of ensemble models and multi-model-ensembles to predict the event in the medium-range using TIGGE data Phase 3: Modelling Studies to rerun the case studies with sensitivity experiments, process studies, explore performance of high-resolution models and investigate the causes of the good or bad performance of the models relative to the case studies. Limited Area Models in the framework of TIGGEE (TIGGE-LAMS) could be set over different subregions to measure value added by ensemble LAMS. Workshops are scheduled after each phase completion to present and discuss results. For each sub-region (north, south, east/central, west) case studies related to flood events were chosen by focal points 3) Status of cases studies East/Central Africa case It concerns a severe flooding episode that hit East and Central Africa in the second half of October 1997 and caused devastating loss of life and property in some areas. As a first step in the synoptic description of this High Impact Weather event, all 4 countries were asked to supply in-situ data. Preliminary analyses of the station rainfall indicate that East Africa received excessive precipitations during October 1997; in R.D Congo, record rainfall was observed up to December In Ethiopia, most of the rains (averaging 60 to 90 percent of the monthly total rainfall) were received within 11 days over the period October, More south, record total rainfall was observed within 7 days within the period October, 1997 (averaging 50 to 70 percent of the monthly total rainfall for much of the North-eastern Highland and the Northern Coast of Tanzania). In an attempt to gain insight into the atmospheric processes involved, initial t results show that these excessive rainfalls occurred in association with strong ENSO conditions, a positive phase Indian Ocean Dipole (not shown) as well as significant Equatorial-Rossby (ER) wave activity occurring at this time period. For this case, step 2 of the phase1 has been achieved mainly by University la Réunion and Ethiopian met Service with data provided by Ethiopian, Tanzanian and Kenyan met Service.

3 CAS/ICSC-9/Doc.4.1, p. 3 West Africa case It concerns a severe flash flood that hits Ouagadoudou, Burkina Faso on September 1 st, 2009 and many other flash floods in the Sahelian region (e.g. Dakar, Senegal; Rosso Mauritania; Agadez, Niger) during the first decade of September. Indeed, the first decade of September 2009 coincided with a very active phase of the West African monsoon (WAM). Analyses indicate the occurrence of a deep easterly wave with embedded mesoscale convective systems near its trough giving heavy rainfall as long as the easterly wave moves eastward. It is Burkina Faso which experienced the heaviest rainfall; in Ouagadougou, the capital city, the total rainfall exceeded 200mm per day, with 260mm of rainfall recorded at Ouagadougou during ten hours of continuous rain, causing nine deaths, destroyed houses (250), bridges and roads, displacement of people (nearly ). For this case the step 1 (synoptic analysis) and step 2 (extremeness of the event) of phase 1 are ongoing. Southern Africa case On the 11 and 12 th November 2008 there were heavy rainfall events in some parts of South Africa. These rainfall events led to the death of 27 people in Western Cape province (situated southern part of the country). Most provinces in the interior of South Africa experienced convective rainfall with many lightning strokes recorded. The main weather events that caused this were cut off low, troughs, fronts and surface lows. The synoptic analysis for this case study (step 1 of phase 1) has been provided. North Africa case(s) Interesting case studies of flooding affecting Algeria in October/November 2008, July 2009 and April 2010 have been submitting for further studies. Synoptic study (step 1 of phase 1) for the April 2O10 case has been submitted 4) Participation to RA1-XV session at Marrakech in November 2011 Before the XV session of the WMO Regional Association I (RAI, Africa) a report on THORPEX-Africa progress, since RAI-XIV in 2007, was sent to the RAI president. THORPEX-Africa presentation was preceded by CAS presentation by Michel Beland. THORPEX-Africa motivation, implementation activities, progress, HIW information system, request to PRs and delegates for their support. The RAI president and management team and many heads of Met services expressed their support to THORPEX and required more interaction with RAI. They also include a working group on Improved Weather Forecast and natural disasters in the RAI working group. 3. Planned activities for some highlights Implementation activities Linking THORPEX-Africa to operations o Design a template on High Impact Weather (HIW) events and encourage and promote reporting of HIW close to near real-time and also promote close to near real-time verification of the events. For areas without Severe Weather Forecast Demonstration Projects (SWFDPs) (e.g. West Africa), develop a dedicated web page with products that can be derived from ECMWF model outputs. o o Customized TIGGE products for applications in Africa (related to temperature, wind, humidity, and rainfall) Working with the TIGGE Working Groups and the SWFDPs where they exist for example Southern Africa and East Africa and working directly with groups of National Meteorological and Hydrological Services (NMHSs) in other cases. For both TIGGE and ECMWF products, encourage NMHSs to provide feedback on the value of these products. THORPEX-Africa should contribute to scientific evaluation of these products.

4 CAS/ICSC-9/Doc.4.1, p. 4 Following-up the set of case studies engaging the working groups (E.g.; PDP, TIGGE) to the maximum extent. Encouraging universities and NMHSs to collaborate on activities related to predictability Following-up the development of the HIW Information System when dedicated personnel are available (incorporating HIW reporting, case studies, socio-economic information, data related to the events, etc). The Information System will initially be hosted at the ICTP and eventually transferred to an African centre. Training On the use of the ensemble products (mostly forecasters) On the skills to enable NMHSs to add value to model products, particularly multimodel ensemble data. Resources Implementation of major THORPEX Africa activities requires additional resources. Previous initiatives for funding did not succeed. The resources required are funding for two individuals to implement (i) High Impact Weather Information System, (ii) Generate test products for (and manage) a dedicated website, Ideally funding is also required for post-docs and graduate students to conduct predictability studies and analyses of High Impact Weather events and for supporting facilities, networking, scientific visits and training programs. Next meeting The last proper Regional Committee (RC) meeting was held in July 2008 in South Africa. It is proposed to hold a Regional Committee meeting conjointly with small workshop involving some RC members and others resource persons. The aim of this workshop will be to develop templates to be submitted to NHMSs indicating HIW for further study, to develop programs to derive products ECMWF if access is provided and to discuss West and East/Central Africa case studies. The RC meeting will help to propose new membership with specific work assigned to each member of the RC.

5 CAS/ICSC-9/Doc.4.1, p. 5 Annex 1 Current membership of the African Regional Committee for THORPEX Ernest Afiesimama, Meteorological Agency, Nigeria Amare Babu, National Meteorological Service, Ethiopia Kwabena Asomanin Anaman, Ghana Institute of Management and Public Administration (GIMPA) Accra, Ghana Arona Diedhiou, Institute for Research and Development (IRD), France Aida Diongue-Niang, Meteorological Agency, Senegal, co-chair Andre Kamga Foamouhoue, African Centre of Meteorological Applications and Development (ACMAD), Niger Joseph Katongo KANYANGA, Zambia Meteorological Department Benjamin Lamptey, Regional Maritime University, Accra, Ghana, co-chair Abdellah Mokssit, Meterological Office, Morocco Zilore Mumba, African Centre of Meteorological Applications and Development (ACMAD), Niger Isaac Ngwana, South African Weather Service Franklin Opijah, University of Nairobi, Kenya It was proposed to replace Zilore MUMBA who is no longer at ACMAD by his successor at ACMAD: to replace Abdallah MOKSSIT by Miloud BESSAFI at La Reunion University. In the terms of reference of the regional committee it was stated that, after 4 years (then December 2011), half of the members should step down and replaced by new members. The membership should be kept at ten or below.