Global S&T Development Trend Analysis Platform of Resources and Environment
How predictable were this summer’s European temperature records? | |
admin | |
2019-08-27 | |
发布年 | 2019 |
语种 | 英语 |
国家 | 欧洲 |
领域 | 地球科学 ; 气候变化 |
正文(英文) | ![]() Several European national and city temperature records tumbled this summer during two separate heatwaves in June and July. How well can such extreme events be predicted using a state-of-the-art global forecasting system? We have looked at ECMWF’s 2-metre temperature forecasts for three locations where national records were broken. These records are 46.0°C in the French village of Vérargues on 28 June; 42.6°C in the town of Lingen in Germany on 25 July; and 38.7° in the city of Cambridge in the UK on 25 July. The July heatwave also set new temperature records in Belgium, Luxembourg and the Netherlands. Key findings are that
To understand these findings, it is important to bear in mind two things:
Let’s now look at the predictions made by ENS and HRES for the three locations. Vérargues: 46.0°CSuccessive ENS and HRES forecasts for maximum 2-metre temperature on 28 June for the grid box containing Vérargues are shown below.
The blue box-and-whisker symbols indicate the range of predicted values in each ENS forecast. The red box-and-whisker symbol shows the climatological range of temperatures in that grid box. The ensemble started to predict above-average temperatures 10 days ahead of the event, and as early as 7 days ahead most ensemble members predicted top temperatures in excess of the 99th percentile of the local climate. Although more than three days ahead the ensemble was very confident of temperatures well above the 99th percentile of the local climate, even the shortest-range ENS and HRES forecasts remained below the 46°C recorded at Vérargues. There are two reasons for this. One is that the predictions were for average conditions in the grid box as a whole. They did not take into account local variations, for example in soil moisture and vegetation. The other is that, in common with other global forecasting systems, ECMWF forecasts have biases in near-surface predictions. These include a tendency, in many parts of Europe, to underpredict maximum temperatures in summer. Possible ways to remedy this are being investigated. Lingen: 42.6°C
The ensemble started to predict warmer than average conditions 12 days before 25 July. In subsequent forecasts, predicted top temperatures steadily rose. Six days ahead, most ensemble members predicted top temperatures above the 99th percentile of the local climate. Once again, predicted temperatures remained a few degrees below the 42.6°C recorded at Lingen, for the reasons outlined above for the case of Vérargues. An interesting feature in this case is a high degree of jumpiness in HRES forecasts 8 to 9 days ahead of the event, with a prediction of about 38°C one day and 26°C the next. A forecaster looking just at the HRES would have had no way of knowing what confidence to attach to these different forecasts. The ENS forecasts provide a fuller picture. They show that the HRES forecasts were made at a time when uncertainty was still high and that they were part of a large spread of possible outcomes. Cambridge: 38.7°C
The ensemble started to consistently predict warmer than average conditions 11 days before 25 July, and six days ahead most ensemble members predicted top temperatures above the 99th percentile of the local climate. However, in this case the range of predicted possible outcomes remained relatively large until about 4 days ahead of the event. This is because until then it was not clear how far west exactly the southerly flow bringing highly unusual temperatures would reach. Between about 8 and 9 days ahead, the HRES forecasts for Cambridge once again show some big jumps, between about 23°C one day and about 34°C the next. The evolution of the ENS is much more consistent and shows that the HRES forecasts are different possible realisations in a situation marked by great uncertainty. In Cambridge, too, the predicted temperatures remained well under the recorded 38.7°C, which may have been boosted by the location of the measuring station in an urban environment. How good were the forecasts?ECMWF’s medium-range forecasts provided good advance indications of highly unusual temperatures in the three locations shown. There was overall good consistency between successive forecasts and high confidence that extreme temperatures would occur as early as about a week in advance. Nevertheless, the predicted temperatures did not quite match the national records, for two reasons. The first is that, in any global forecasting system, predictions are made for average values in grid boxes which are typically at least about 10 km kilometres wide. The second is that, in common with other global forecasting systems, in many locations in Europe there are known biases in ECMWF’s near-surface forecasts, including a tendency to underpredict maximum temperatures in summer. Although biases can to some extent be removed statistically, there is value in having less biased direct model output, and for this reason addressing biases in near-surface forecasts is an active area of research at ECMWF. Initial results show that such biases are closely related to the coupling between the atmosphere and the land surface, but work to identify and isolate the influence of the different factors involved is continuing. |
URL | 查看原文 |
来源平台 | European Centre for Medium-Range Weather Forecasts |
文献类型 | 新闻 |
条目标识符 | http://119.78.100.173/C666/handle/2XK7JSWQ/136110 |
专题 | 地球科学 气候变化 |
推荐引用方式 GB/T 7714 | admin. How predictable were this summer’s European temperature records?. 2019. |
条目包含的文件 | 条目无相关文件。 |
个性服务 |
推荐该条目 |
保存到收藏夹 |
查看访问统计 |
导出为Endnote文件 |
谷歌学术 |
谷歌学术中相似的文章 |
[admin]的文章 |
百度学术 |
百度学术中相似的文章 |
[admin]的文章 |
必应学术 |
必应学术中相似的文章 |
[admin]的文章 |
相关权益政策 |
暂无数据 |
收藏/分享 |
除非特别说明,本系统中所有内容都受版权保护,并保留所有权利。
修改评论