Predicting Impacts of Cyclones in South-East Africa (PICSEA)

平均每年有14个热带气旋在南印度洋形成，大部分在11月至4月之间。其中，每年约有2-3个气旋在东南部非洲登陆，最常见的是莫桑比克和马达加斯加。在这些国家，热带气旋与约三分之一的极端日降水事件有关，极端日降水事件的定义是累计降雨量超过50毫米(2英寸)的日子。2012年热带气旋登陆莫桑比克造成严重洪灾，造成6500万美元损失和150人死亡。2018年初，马达加斯加发生两次气旋登陆，造成23人死亡，2.1万人流离失所。塞舌尔群岛也受到热带气旋的影响，包括2016年的5类(最严重的)Fantala。尽管东南部非洲人口易受热带气旋和相关灾害的影响，但人们对当代天气和气候预测系统预测气旋路径、强度和风雨影响的能力知之甚少。此外，可能存在特殊的热带大气环流模式，为更准确的气旋预报提供了“机会之窗”。例如，厄尔尼诺现象(温暖的赤道太平洋温度)可为更准确地预测热带气旋及其影响提供背景。“东南亚气旋的预测影响”项目(PICSEA)通过提供迄今为止对热带气旋及其对东南部非洲影响的预报系统的最全面评估，解决了这些缺点。对于如何最好地解读南印度洋热带气旋预报，各国气象机构、人道主义组织和日益增长的基于预报的金融界提供建议，迫切需要这种评估。具体地说，PICSEA将确定哪些预报系统、提前时间和背景热带环流导致相对准确的热带气旋预测。灾害管理机构什么时候应该相信登陆热带气旋的预报，什么时候不应该相信？最初，PICSEA将评估三个天气预报中心对热带气旋路径、强度和相关危险(主要是风和雨)的预报的准确性：英国气象局、欧洲中期天气预报中心和美国国家环境预报中心。我们每个中心都有10到30年的预测数据，包括每个预测的多次实现。我们将确定当代预报系统可以在多大程度上以及在多长时间内提前预报与非洲东南部热带气旋相关的极端风和降雨。接下来，PICSEA将确定是否有特定的背景热带条件，如厄尔尼诺或拉尼娜，导致或多或少准确的预报。我们将通过评估预测精度来实现这一点，条件是背景条件的类型。在拉尼娜或厄尔尼诺期间，与气旋相关的危害的技能更强吗？在某些特殊情况下，预报员和灾害管理机构应该更多还是更少地信任这些预报？最后，PICSEA将与合作组织--莫桑比克、马达加斯加和塞舌尔的国家气象组织，以及红十字会/红新月会气候中心--合作，为解释热带气旋预报提供指导。红十字会/红新月会气候中心是向人道主义组织和基于预报的金融界提供科学建议的主要提供者。我们将与预报员和灾害管理机构合作，提高他们对何时可以信任和不能信任有关龙卷风影响的预报信息的理解。该中心还将为东南部非洲气象机构的预报员提供使用这一指南的培训以及热带气象学的背景培训。

On average, 14 tropical cyclones per year form in the southern Indian Ocean, most in the months between November and April. Of these, about 2-3 cyclones per year make landfall in southeast Africa, most often in Mozambique and Madagascar. In these countries, tropical cyclones are associated with approximately one-third of all extreme daily precipitation events, defined as days with rainfall accumulations greater than 50 mm (2 inches). Tropical cyclone landfalls in Mozambique in 2012 caused severe flooding, resulting in US$65 million in damage and 150 deaths. Two cyclone landfalls in Madagascar in early 2018 resulted in 23 deaths and displaced 21,000. The Seychelles archipelago is also affected by tropical cyclones, including category 5 (the most severe) Fantala in 2016.Despite the vulnerability of the southeast African population to tropical cyclones and related hazards, little is known about the ability of contemporary weather and climate prediction systems to forecast cyclone tracks, intensities, and wind and rain impacts. Further, there may be particular tropical atmospheric circulation patterns that provide "windows of opportunity" for more accurate cyclone forecasts. For instance, El Nino conditions (warm equatorial Pacific Ocean temperatures) may provide the backdrop for more accurate predictions of tropical cyclones and their impacts.The "Predicting Impacts of Cyclones in South-East Asia" (PICSEA) project addresses these shortcomings by providing the most comprehensive assessment of forecast systems to date for tropical cyclones and their effects on southeast Africa. This assessment is needed desperately to give advice to national meteorological agencies, humanitarian organisations and the growing forecast-based finance community on how best to interpret forecasts of tropical cyclones in the southern Indian Ocean. Specifically, PICSEA will determine which forecast systems, lead times and background tropical circulations lead to relatively more or less accurate tropical cyclone predictions. When should disaster management agencies trust a forecast for a landfalling tropical cyclone, and when should they not?Initially, PICSEA will assess the accuracy of predictions of tropical cyclone tracks, intensities and associated hazards (primarily wind and rain) from three weather forecasting centres: the UK Met Office, the European Centre for Medium-range Weather Forecasts and the US National Centers for Environmental Prediction. We have 10-30 years of forecast data for each centre, including multiple realisations of each forecast. We will determine to what extent, and how far in advance, contemporary prediction systems can forecast the extreme winds and rainfall associated with tropical cyclones in southeast Africa.Next, PICSEA will determine whether there are particular background tropical conditions, such as El Nino or La Nina, that lead to more or less accurate forecasts. We will do this by evaluating forecast accuracy conditioned on the type of background conditions. Is skill for cyclone-related hazards greater during La Nina or El Nino? Are there particular circumstances under which forecasters and disaster-management agencies should trust these forecasts more, or less?Finally, PICSEA will work together with partner organisations -- national meteorological organisations in Mozambique, Madagascar and the Seychelles, as well as the Red Cross / Red Crescent Climate Center, a key provider of scientific advice to humanitarian organisations and the forecast-based finance community -- to develop guidance for interpreting tropical cyclone forecasts. We will work with forecasters and disaster-management agencies to improve their understanding of when they can, and cannot, trust forecast information on cyclone impacts. PICSEA will also provide training in the use of this guidance, as well as background training on tropical meteorology, for forecasters in southeast African meteorological agencies.