Under the influence of global warming, heatwaves are becoming a major threat in many parts of the world, affecting human health and mortality, food security, forest fires, biodiversity, energy consumption, as well as the production and transportation networks. Seasonal forecasting is a promising tool to help mitigate these impacts on society. Previous studies have highlighted some predictive capacity of seasonal forecast systems for specific strong heatwaves such as those of 2003 and 2010. To our knowledge, this study is thus the first of its kind to systematically assess the prediction skill of heatwaves over Europe in a state-of-the-art seasonal forecast system. One major prerequisite to do so is to appropriately define heatwaves. Existing heatwave indices, built to measure heatwave duration and severity, are often designed for specific impacts and thus have limited robustness for an analysis of heatwave variability. In this study, we investigate the seasonal prediction skill of European summer heatwaves in the ECMWF System 5 operational forecast system by means of several dedicated metrics, as well as its added-value compared to a simple statistical model based on the linear trend. We are able to show, for the first time, that seasonal forecasts initialized in early May can provide potentially useful information of summer heatwave propensity, which is the tendency of a season to be predisposed to the occurrence of heatwaves.

在全球变暖的影响下，热浪正在成为世界许多地区的主要威胁，影响人类健康和死亡率、粮食安全、森林火灾、生物多样性、能源消耗以及生产和运输网络。季节性预测是一种很有前途的工具，可以帮助减轻这些对社会的影响。以前的研究强调了季节性预报系统对特定强热浪的一些预测能力，例如 2003 年和 2010 年的那些。 据我们所知，这项研究因此是第一次系统地评估欧洲热浪的预测能力。最先进的季节预测系统。这样做的一个主要先决条件是适当地定义热浪。现有的热浪指数，用于衡量热浪持续时间和严重程度，通常是针对特定影响而设计的，因此对热浪变化分析的稳健性有限。在本研究中，我们通过几个专用指标研究了 ECMWF System 5 运行预测系统中欧洲夏季热浪的季节性预测技巧，以及与基于线性趋势的简单统计模型相比的附加值。我们能够首次表明，在 5 月初初始化的季节性预测可以提供潜在的有用信息 以及与基于线性趋势的简单统计模型相比的附加值。我们能够首次表明，在 5 月初初始化的季节性预测可以提供潜在的有用信息 以及与基于线性趋势的简单统计模型相比的附加值。我们能够首次表明，在 5 月初初始化的季节性预测可以提供潜在的有用信息夏季热浪倾向，这是一个季节容易发生热浪的趋势。