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Downstream control of blocking and Rossby wave breaking by extratropical cyclones

温带气旋对阻塞和罗斯贝波破碎的下游控制

基本信息

批准号：
1643655
负责人：
金额：
--
依托单位：
University of Reading
依托单位国家：
英国
项目类别：
Studentship
财政年份：
2015
资助国家：
英国
起止时间：
2015 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=studentship-1643655
关键词：
Downstream control blocking Rossby wave

项目摘要

Skillful weather and climate forecasts on timescales from hours to centuries are vital for protecting lives and livelihoods and managing the effects of climate change. The Observing System Research and Predictability Experiment (THORPEX) of the World Meteorological Organization grew out of a recognition that, despite continued improvements in numerical weather prediction forecasts (THORPEX specifically considered 1-14 day lead times), further improvements needed to be made. Errors in these forecasts arise due to errors in the initial conditions (the chaotic `butterfly effect'), boundary conditions (e.g. sea surface temperature errors in a weather forecast) and errors in the model formulation (so-called model error). Errors occurring at tropopause level propagate downstream due to their influence on the development, propagation and breaking of the planetary-scale Rossby waves associated with meanders of the upper-level (~10 km high) jet stream. Ridges and troughs in the jet stream are the major driver of the development of extratropical cyclones (a.k.a winter storms) associated with strong surface winds and rain as well as blocking events associated with e.g. summer heatwaves and health impacts due to the trapping of pollutants. One type of systematic error is that due to the mis-representation of diabatic processes such as clouds and radiation in extratropical cyclones, resulting from the necessity to parametrize convection and other moist processes in global (and most regional) weather forecast models. The influence of errors in the representation of these processes in a given storm are propagated downstream and so can affect the forecast of future developing storms or blocking episodes, leading to so-called 'forecast busts'. Identification of such systematic errors is the first step to determining model improvements to reduce them. The CASE partner for this project is the Met Office and our collaboration is with both the 'ensemble forecasting' and 'model evaluation and diagnostics' research groups. In a seamless model prediction system, such as the Met Office's operational climate and weather forecast model (known as the Unified Model), identification and reduction of systematic errors using one component of the system (here we use the weather forecasting component) can potentially improve forecasts across all forecast time horizons from hours to centuries. In this project we causally associate errors in tropopause structure caused by the mis-representation of diabatic processes in extratropical cyclones and determine their influence on downstream error in Rossby-wave breaking and blocking.

从几小时到几个世纪的时间尺度上熟练的天气和气候预报对于保护生命和生计以及管理气候变化的影响至关重要。世界气象组织的观测系统研究和可预测性实验（THORPEX）源于一种认识，即尽管数值天气预报不断改进（THORPEX特别考虑了1-14天的提前期），但需要进一步改进。这些预报的误差是由于初始条件的误差（混沌的“蝴蝶效应”）、边界条件的误差（例如天气预报中的海面温度误差）和模式制定的误差（所谓的模式误差）造成的。发生在对流层顶的误差会向下游传播，这是由于它们对与高层（~10 km）急流弯曲有关的行星尺度罗斯比波的发展、传播和破裂产生影响。急流中的脊和槽是与强地面风和雨有关的温带气旋（又称冬季风暴）发展的主要驱动力，以及与夏季热浪和因污染物捕获而造成的健康影响有关的阻塞事件。系统误差的一种类型是由于在全球（和大多数区域）天气预报模式中必须参数化对流和其他潮湿过程而导致的非绝热过程，如温带气旋中的云和辐射的错误表示。在一个给定的风暴中，这些过程的表示错误的影响会向下游传播，因此会影响对未来发展中的风暴或阻塞事件的预测，导致所谓的“预测萧条”。识别这种系统误差是决定改进模型以减少它们的第一步。这个项目的CASE合作伙伴是英国气象局，我们的合作伙伴是“集合预测”和“模型评估和诊断”研究小组。在一个无缝模型预测系统中，比如英国气象局的气候和天气预报模型（被称为“统一模型”），使用系统的一个组件（这里我们使用天气预报组件）识别和减少系统误差，可以潜在地提高从几个小时到几个世纪的所有预测时间范围的预测。在这个项目中，我们将对流层顶结构的误差与温带气旋中非绝热过程的错误表示联系起来，并确定它们对罗斯波破碎和阻塞的下游误差的影响。