There’s more to the UK winter than the stratosphere

The title might seem rather obvious - or a surprising statement coming from me! But what I seek to achieve in this short blog post is provide a simple reminder that historically cold weather has indeed happened without a sudden stratospheric warming (or significant stratospheric polar vortex disruption). The role of the stratosphere can sometimes … Continue reading There’s more to the UK winter than the stratosphere

10 FAQs on “Increased shear in the North Atlantic upper-level jet stream over the past four decades”

Lee, S. H., P. D. Williams, and T. H. A. Frame, 2019: Increased shear in the North Atlantic upper-level jet stream over the past four decades. Nature, https://doi.org/10.1038/s41586-019-1465-z. What is the key result of the study? Our study shows that the annual-mean vertical west-to-east (zonal) wind shear over the North Atlantic at aircraft cruising altitudes (within the … Continue reading 10 FAQs on “Increased shear in the North Atlantic upper-level jet stream over the past four decades”

A “winter heatwave” in a warming world

The final week of February 2019 has been characterised by anomalously warm, record-setting conditions over NW Europe. The United Kingdom broke its all-time maximum record temperature for February on several occasions and at several stations - the previous record of 19.7C from 1998 was obliterated, replaced with a new record of 21.2C (a huge difference … Continue reading A “winter heatwave” in a warming world

Not all SSWs were created equal

Non-downward propagating SSWs?  Major stratospheric sudden warming events (SSWs) attract widespread attention because they are now known to have significant impacts on the tropospheric circulation (e.g. Baldwin and Dunkerton 2001, hereafter BD01). Anomalies in the stratospheric circulation (often expressed as the Northern Annual Mode (NAM) index, or polar cap geopotential height anomalies) propagate downwards through … Continue reading Not all SSWs were created equal

The Stratosphere – why do we care?

I study the stratosphere, the layer of atmosphere above the troposphere that extends from about 10-50 km above the surface. Some people might joke (I hope) that "nobody cares about the stratosphere", primarily because, unlike the troposphere, it contains no 'weather' in the traditional sense. Being very dry (...literally), it can't be seen on visible … Continue reading The Stratosphere – why do we care?