Measurements of the mean structure, temperature, and circulation of the MLT

Vol. 55, Issue 3 (Heliophysics 2024 Decadal Whitepapers) American Astronomical Society (2023)


Anne K Smith, Colby Brabec, Jorge Chau, Xinzhao Chu, Bernd Funke, V Lynn Harvey, McArthur Jones Jr., Aimee Merkel, Steven Miller, Martin Mlynczak, Scott Osprey, Doug Rowland, Jia Yue

Understanding the mechanisms for tropical surface impacts of the quasi‐biennial oscillation (QBO)

Journal of Geophysical Research: Atmospheres Wiley 128:15 (2023) e2023JD038474


Jorge L García‐Franco, Lesley J Gray, Scott Osprey, Aleena M Jaison, Robin Chadwick, Jonathan Lin


The impact of the quasi-biennial oscillation (QBO) on tropical convection and precipitation is investigated through nudging experiments using the UK Met Office Hadley Center Unified Model. The model control simulations show robust links between the internally generated QBO and tropical precipitation and circulation. The model zonal wind in the tropical stratosphere was nudged above 90 hPa in atmosphere-only and coupled ocean-atmosphere configurations. The convection and precipitation in the atmosphere-only simulations do not differ between the experiments with and without nudging, which may indicate that SST-convection coupling is needed for any QBO influence on the tropical lower troposphere and surface. In the coupled experiments, the precipitation and sea-surface temperature relationships with the QBO phase disappear when nudging is applied. Imposing a realistic QBO-driven static stability anomaly in the upper-troposphere lower-stratosphere is not sufficient to simulate tropical surface impacts. The nudging reduced the influence of the lower troposphere on the upper branch of the Walker circulation, irrespective of the QBO, indicating that the upper tropospheric zonal circulation has been decoupled from the surface by the nudging. These results suggest that grid-point nudging mutes relevant feedback processes occurring at the tropopause level, including high cloud radiative effects and wave mean flow interactions, which may play a key role in stratospheric-tropospheric coupling.

Documenting the impacts of climate change on the middle and upper atmosphere and atmospheric drag of space objects

Stratosphere-troposphere Processes And their Role in Climate (SPARC) 61 (2023) 10-14


Juan Anel, Ingrid Cnossen, Juan Carlos Antuna-Marrero, Gufran Beig, Matthew Brown, Eelco Doornbos, Rolando Garcia, Lesley Gray, Daniel Marsh, Scott Osprey, Martin Mlynczak, Shaylah Maria Mutschler, Petr Pisoft, Viktoria Sofieva, Petr Sacha, Laura de la Torre, Shun-Rong Zhang

The Changing-Atmosphere Infra-Red Tomography Explorer (CAIRT)

Stratosphere-troposphere Processes And their Role in Climate (SPARC) 61 (2023) 6-9


Bjorn-Martin Sinnhuber, Martyn Chipperfield, Quentin Errera, Felix Friedl-Vallon, Bernd Funke, Sophie Godin-Beekmann, Scott Osprey, Inna Polichtchouk, Peter Preusse, Piera Raspollini, Pekka Verronen, Kaley Walker

North-West Europe hottest days are warming twice as fast as mean summer days

Geophysical Research Letters American Geophysical Union 50:10 (2023) e2023GL102757


Europe has seen a rapid increase in the frequency and intensity of hot extremes in recent decades. In this study it is shown, using ERA5 reanalysis data 1960–2021, that the hottest summer days in North-West Europe are warming approximately twice as fast as mean summer days. Moreover, this pattern stands out as relatively unusual across the Northern Hemisphere. It is also shown that comprehensive climate models fail to capture this difference in trends. A hypothesis is suggested to explain the differential rate of warming between the mean and hottest days, namely that the hottest days are often linked to warm advection from Iberia and North Africa, areas that are warming faster than North-West Europe. This hypothesis can account for about 25% of the difference between ERA5 and a climate model ensemble and hence further research is needed to understand the drivers of the differing trends in mean and extreme temperature.