Understanding African Easterly Waves and their Predictability: a moist singular vector appraoch

西非夏季风中的东风波对该地区至关重要，因为对流降雨主要由它们组织。这种降雨的变化会对已经脆弱的人口造成毁灭性的影响。这些天气系统中有一小部分在北大西洋下游转化为飓风。然而，尽管这些东浪具有重要意义，天气和气候模式在预测它们和模拟该地区的季节性降雨分布方面仍然存在困难。人们已经开发出一种技术，可以发现初始数据的微小变化，即“最佳扰动”，这种变化会导致天气预报的最大变化，例如在一天内。这项技术已被用来帮助了解中纬度地区强冲击风暴的增长。它也是一个方案的基础，该方案为产生综合天气预报的预报系统提供一系列略有不同的初始条件。这个集合给出了未来天气事件发生概率的指示。最优摄动也用于指示热带气旋行为的敏感性，但该技术尚未用于热带地区。在这个项目中，一个产生这些最佳扰动的新版本的软件包将应用于西非的东风波。它将被用来帮助这些系统的理论认识。这将为在2006年一系列国际运动中使用重要的新观测提供基础。它还将展示非洲东风波的可预测性，包括它们带来的对流降雨以及它们转变为飓风的可能性。该项目将为天气预报中心建立一个综合预报系统提供基础，该系统最初集中于热带地区，但也可能有助于建议中纬度地区随后的变化。

The easterly waves that occur in West African summer monsoon are of vital importance to the region as the convective rainfall is mostly organised by them. The variability of this rainfall can have devastating impacts on the already vulnerable population. A small number of these weather systems transform downstream in the north Atlantic into hurricanes. However, despite the significance of these easterly waves, weather and climate models continue to have difficulties in predicting them and simulating the seasonal rainfall distribution in the region. A technique has been developed to find small changes to initial data, 'optimal perturbations', that produce the largest changes in the weather predicted in, for example, one day. This technique has been used to help understand the growth of high impact storms in middle latitudes. It is also the basis for a scheme that provides a range of slightly different initial conditions for a forecast system that produces an ensemble of weather forecasts. This ensemble gives indications of the probability of future weather events. Optimal perturbations are also used for giving indications of the sensitivity of tropical cyclone behaviour, but the technique has otherwise not been used for the tropics. In this project, a new version of the package to produce these optimal perturbations will be applied to the easterly waves in West Africa. It will be used to help the theoretical understanding of these systems. This will give a basis for using the important new observations that will be taken in 2006 in a series of international campaigns. It will also show how predictable African easterly waves are, including the convective rainfall they give and the likelihood that they will turn in to a hurricane. The project will provide a basis for weather forecast centres to construct an ensemble forecast system that is focussed initially on the tropics, but may also help in suggesting subsequent changes in middle latitudes.