Overview of Southern Hemisphere THORPEX Regional Plans and Activities
A Southern Hemisphere Science Plan has been developed to provide input to the development of an Implementation Plan for Southern Hemisphere THORPEX, involving scientists from South America, Australia, New Zealand, Southern Hemisphere Africa and Southern Hemisphere nations in the Pacific, Atlantic and Indian Oceans working through a SH Regional Committee.

The SH Science plan develops a rationale for a Southern Hemisphere regional focus for THORPEX that emphasises a number of features that a unique to the hemisphere. These include (i) a large percentage of the Southern Hemisphere is covered by oceans; (ii) the various countries of the hemisphere have strongly overlapping problems associated with the monitoring and forecasting of weather and climate; (iii) large differences from the Northern Hemisphere in terms of the meteorology on the 1-day to 2 weeks timescale which is partly due to the weaker orographic and continental forcing of the Southern Hemisphere flow; (iv) the peculiar feature of the Southern Hemisphere summer circulation characterized by three major subtropical fronts (South Pacific Convergence Zone - SPCZ, South Atlantic Convergence Zone - SACZ and South Indian Convergence Zone –SICZ.

An important aspect that emerged from discussions between scientists across the Southern Hemisphere is the commonality in forecast problems across the hemisphere which provides a major justification for a coordinated SH THORPEX campaign. Examples of the commonality include:

• Fire weather is common to Australia and South Africa, and in both cases is associated with synoptic scale conditions leading to strong pressure gradients with a cross continental trajectory.
• The Madden Julian Oscillation is a major modifier of weather on the 1-2 week timescale (and longer) for the tropical portions of Southern Hemisphere Africa, South America and Australia-New Zealand.
• Cut-off lows are producers of major wide-spread flooding events off the east coast of all three southern hemisphere continents.
• Rapid cyclogenesis causing gale-force winds and rapid sea swells have brought about major boating disasters off the east coasts of South Africa, South America and Australia.
• Wide spread flooding and loss of life associated with tropical cyclone landfall is the major high impact phenomenon for the Australian tropical coastline, the South Pacific countries and the region of Mozambique, Madagascar and Mauritius.
• Semi-stationary mid-tropospheric (blocking) anticyclones lead to extended heat-wave conditions over southern Africa, central region of South America and Australia.

The evolving Science Plan was discussed at a two-day Workshop held in Melbourne, Australia during 28-29 November 2005. The Workshop’s aim was to initiate discussions towards the establishment of a Southern Hemisphere THORPEX Committee and to determine initial research foci and plans for international cooperation within the Southern Hemisphere on conducting research and observing system test projects. The Science plan was further revised and then presented at a WWRP/THORPEX Scientific Conference on "Improving the Global Prediction of High Impact Weather and a Review of Southern Hemisphere THORPEX Plans for THORPEX" held from 13 to 15 February 2006, in Cape Town, South Africa. At the conclusion of this Conference it was decided to form a Southern Hemisphere Regional THORPEX Committee to take this Science Plan forward and develop an associated Implementation Plan.

The Southern Hemisphere Regional Committee (SHRC) was formed with K. Puri (Bureau of Meteorology) and N. Gordon (MetService New Zealand) as co-Chairs following the recommendations from the WWRP/THORPEX Scientific Conference on ‘Improving the Global Prediction of High Impact Weather and a Review of Southern Hemisphere THORPEX Plans for THORPEX’ held in Cape Town from 13 to 15 February 2006. As shown in Table 1 the membership of the Committee includes representatives from key Southern Hemisphere countries.

The initial activity of the SHRC has been to develop an Implementation Plan based on the Science Plan. It was agreed at the outset that the plan needed to be kept simple and short. The key consideration was to focus on a small group of areas that are important and where the Committee can actually achieve useful results bearing in mind the major restriction in the level of funding available. The SH Plan follows closely the International Science Plan in developing the Research Objectives under three sub-programmes, namely (i) Predictability and Dynamical Processes; ii) Data Assimilation and Observing Strategies, including Observing Systems (iii) Societal and Economic Applications. The three sub-programmes and teams were set up as follows:

1. Predictability and Dynamical Processes

THORPEX will carry out studies of predictability and dynamical processes to determine which spatial and temporal scales of motion must be better observed, analyzed, parameterized, and simulated for the improvement of short and medium-range forecasts. Concurrent research and numerical experimentation with real and idealized observations will be used to develop strategies for the design and deployment of new observing systems, and to optimize and improve methods for the assimilation of observations.

Team: Convenors: J. McBride and M. Gan
Members: C. Mutai, I. Simmonds, K.Puri

Possible areas:

• Real-time monitoring of dynamics and predictability – set up a publicly accessible web page to monitor predictability and dynamical processes in real time; this is probably the quickest and most feasible thing to do, and will tend to maintain the feeling of communication amongst countries;
• Tropical systems – tropical cyclones, MJO etc;
• The Antarctic and SH polar latitudes phenomena.

2. Data Assimilation and Observing Strategies, including Observing Systems

A central aspect of THORpex is to improve the use of existing in-situ and space-based observations. In addition, THORpex will develop and evaluate new observing technology designed to improve the observational quality and coverage in critical regions of the atmosphere. The observing system field-test and evaluation will be accomplished during a series of regional field experiments designed to address specific predictability issues. The regional experiments will provide data sets to test observing strategies, data assimilation, and predictability hypotheses in particular geographic areas of the southern hemisphere.

Team: Convenors: P. Steinle and M. Uddstrom
Members: W. Tennant, E. Bobadilla, E. Ebert

Possible areas:

• Collaboration between centres interested in Southern Hemisphere NWP in general and data assimilation in particular;
• Data assimilation in the tropics;
• Characterization of background errors in the tropics and southern hemisphere. This should include their estimation, specification and evolution for high resolution NWP;
• The development of performance metrics suited to assessing southern hemisphere high impact weather predictions and the impact of these forecasts on the major users;
• Methods for processing and assimilating high volume satellite data. This should include observation error characterization, forward modelling, data thinning and compression, and for targeting both instruments and processing of the observations. This should encompass all sources of satellite data;
• The use of new observing systems that are suited for use within southern hemisphere countries;
• The assessment and monitoring of the southern hemisphere observing network;
• Provide input from assessment and impact studies;
• Assess information from studies that assimilate routinely available observation network reports and make appropriate recommendations for adjusting networks and for further investigation;
• Determine what is the impact of different/new systems on a research basis, e.g. AMDAR humidity observations;
• Look into cost against usefulness of certain stations and set priorities.

3. Societal and Economics Research and Applications

The societal and economic impact component will assess the costs and benefits of implementing THORPEX research results into operational practice. This assessment will be made available to operational and research agencies that make decisions on the future allocation of finite resources to the various components of civilian and military weather services. The assessment of costs and benefits associated with the production and use of weather information is a complex interdisciplinary issue. THORPEX societal impact studies will integrate the meteorological operations and research elements with broader societal concerns through three research components: a) assessment of high-impact weather and forecasts, b) use and value of forecast information, c) development of verification measures.

Team: Convenors: E. Poolman and M. Ratag
Members: N. Gordon, A. Ngari, M. Marino

Possible areas:

• Identify high-impact weather forecasts;
• Assess the impact of improved forecast systems;
• Develop advanced forecast verification measures;
• Estimate net benefits of improved forecast systems;
• Develop new user-specific weather products;
• Facilitate transfer of THORPEX advances to forecast centres.