State of the Climate in 2021

Author(s):
Blunden, J.; Boyer, T.
Publication title: Bulletin of the American Meteorological Society
2022
 | Volume: 103 | Issue: 8
2022
DOI: 10.1175/2022BAMSStateoftheClimate.1
Abstract:
Abstract Editors note: For easy download the posted pdf of the State of the Climate in 2021 is a low-resolution file. A hig… Abstract Editors note: For easy download the posted pdf of the State of the Climate in 2021 is a low-resolution file. A high-resolution copy of the report is available by clicking here . Please be patient as it may take a few minutes for the high-resolution file to download. more
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State of the Climate in 2022

Author(s):
Blunden, J.; Boyer, T.; Bartow-Gillies, E.
Publication title: Bulletin of the American Meteorological Society
2023
 | Volume: 104 | Issue: 9
2023
DOI: 10.1175/2023BAMSStateoftheClimate.1
Abstract:
Abstract Editors note: For easy download the posted pdf of the State of the Climate in 2022 is a low-resolution file. A hig… Abstract Editors note: For easy download the posted pdf of the State of the Climate in 2022 is a low-resolution file. A high-resolution copy of the report is available by clicking here . Please be patient as it may take a few minutes for the high-resolution file to download. more
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State of the Climate in 2023

Author(s):
Blunden, J.; Boyer, T.
Publication title: Bulletin of the American Meteorological Society
2024
 | Volume: 105 | Issue: 8
2024
DOI: 10.1175/2024BAMSStateoftheClimate.1
Abstract:
Abstract Editors note: For easy download the posted pdf of the State of the Climate in 2023 is a low-resolution file. A hig… Abstract Editors note: For easy download the posted pdf of the State of the Climate in 2023 is a low-resolution file. A high-resolution copy of the report is available by clicking here . Please be patient as it may take a few minutes for the high-resolution file to download. more
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Stepwise Subduction Observed at a Front in the Marginal Ice Zone in Fram Strait

Author(s):
Hofmann, Z.; von Appen, W.-J.; Kanzow, T.; Becker, H.; Hagemann, J.; Hufnagel, L.; Iversen, M.H.
Publication title: Journal of Geophysical Research: Oceans
2024
 | Volume: 129 | Issue: 5
2024
DOI: 10.1029/2023JC020641
Abstract:
At high latitudes, submesoscale dynamics act on scales of (Formula presented.) (100 m–1 km) and are associated with the breakdown of geostrophic balan… At high latitudes, submesoscale dynamics act on scales of (Formula presented.) (100 m–1 km) and are associated with the breakdown of geostrophic balance, vertical velocities, and energy cascading to small scales. Submesoscale features such as fronts, filaments, and eddies are ubiquitous in marginal ice zones forced by the large horizontal density gradients. In July 2020, we identified multiple fronts and filaments using a towed undulating vehicle near the sea ice edge in central Fram Strait, the oceanic gateway to the Arctic Ocean between Greenland and Svalbard. Sea ice covered the entire study region 1–2 weeks earlier, and a stratified meltwater layer was present. We observed a front between warm and saline Atlantic Water (AW) and cold and fresh Polar Water (PW) at 30–85 m depth, where we identified a subsurface maximum in chlorophyll fluorescence and other biogeochemical properties extending along the tilted isopycnals down to 75 m, indicating subduction of AW (mixed with meltwater) that had previously occurred. The meltwater layer also featured multiple shallow fronts, one of which exhibited high velocities and a subsurface maximum in chlorophyll fluorescence, possibly indicating subduction of PW below the meltwater layer. The fronts at different depth levels suggest a stepwise subduction process near the ice edge, where water subducts from the surface below the meltwater and then further down along subsurface fronts. The submesoscale features were part of a larger-scale mesoscale pattern in the marginal ice zone. As sea ice continuously retreats, such features may become more common in the Arctic Ocean. © 2024. The Authors. more
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Stratocumulus adjustments to aerosol perturbations disentangled with a causal approach

Author(s):
Fons, E; Runge, J; Neubauer, D; Lohmann, U
Publication title: NPJ CLIMATE AND ATMOSPHERIC SCIENCE
2023
 | Volume: 6 | Issue: 1
2023
DOI: 10.1038/s41612-023-00452-w
Abstract:
A large fraction of the uncertainty around future global warming is due to the cooling effect of aerosol-liquid cloud interactions, and in particular … A large fraction of the uncertainty around future global warming is due to the cooling effect of aerosol-liquid cloud interactions, and in particular to the elusive sign of liquid water path (LWP) adjustments to aerosol perturbations. To quantify this adjustment, we propose a causal approach that combines physical knowledge in the form of a causal graph with geostationary satellite observations of stratocumulus clouds. This allows us to remove confounding influences from large-scale meteorology and to disentangle counteracting physical processes (cloud-top entrainment enhancement and precipitation suppression due to aerosol perturbations) on different timescales. This results in weak LWP adjustments that are time-dependent (first positive then negative) and meteorological regime-dependent. More importantly, the causal approach reveals that failing to account for covariations of cloud droplet sizes and cloud depth, which are, respectively, a mediator and a confounder of entrainment and precipitation influences, leads to an overly negative aerosol-induced LWP response. This would result in an underestimation of the cooling influence of aerosol-cloud interactions. more
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Strong persistent cooling of the stratosphere after the Hunga eruption

Author(s):
Stocker, Matthias; Steiner, Andrea K.; Ladstädter, Florian; Foelsche, Ulrich; Randel, William J.
Publication title: Communications Earth & Environment
2024
 | Volume: 5 | Issue: 1
2024
DOI: 10.1038/s43247-024-01620-3
Abstract:
The 2022 eruption of the Hunga volcano was a major event that propelled aerosols and water vapor up to an altitude of 53–57 km. It caused an unprecede… The 2022 eruption of the Hunga volcano was a major event that propelled aerosols and water vapor up to an altitude of 53–57 km. It caused an unprecedented stratospheric hydration that is expected to affect composition, thermal structure, circulation and dynamics for years. Using vertically high resolved satellite observations from radio occultation, we focus on the temperature impact in the stratosphere from the eruption in January 2022 until December 2023. Separating the signals of the Hunga eruption from the broader stratospheric variability reveals a strong persistent radiative cooling of up to –4 K in the tropical and subtropical middle stratosphere from early after the eruption until mid-2023, clearly corresponding to the water vapor distribution. Our results provide new insights from observations into both the localized temperature changes and the persistent stratospheric cooling caused by the Hunga eruption and document this exceptional climatic effect not seen for previous volcanic eruptions. more
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Subseasonal Prediction of Regional Antarctic Sea Ice by a Deep Learning Model

Author(s):
Wang, Y.; Yuan, X.; Ren, Y.; Bushuk, M.; Shu, Q.; Li, C.; Li, X.
Publication title: Geophysical Research Letters
2023
 | Volume: 50 | Issue: 17
2023
DOI: 10.1029/2023GL104347
Abstract:
Antarctic sea ice concentration (SIC) prediction at seasonal scale has been documented, but a gap remains at subseasonal scale (1–8 weeks) due to limi… Antarctic sea ice concentration (SIC) prediction at seasonal scale has been documented, but a gap remains at subseasonal scale (1–8 weeks) due to limited understanding of ice-related physical mechanisms. To overcome this limitation, we developed a deep learning model named Sea Ice Prediction Network (SIPNet) that can predict SIC without the need to account for complex physical processes. Compared to mainstream dynamical models like European Centre for Medium-Range Weather Forecasts, National Centers for Environmental Prediction, and Seamless System for Prediction and Earth System Research developed at Geophysical Fluid Dynamics Laboratory, as well as a relatively advanced statistical model like the linear Markov model, SIPNet outperforms them all, effectively filling the gap in subseasonal Antarctic SIC prediction capability. SIPNet results indicate that autumn SIC variability contributes the most to sea ice predictability, whereas spring contributes the least. In addition, the Weddell Sea displays the highest sea ice predictability, while predictability is low in the West Pacific. SIPNet can also capture the signal of ENSO and SAM on sea ice. © 2023. The Authors. more
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Sudden Stratospheric Warmings in the Northern Hemisphere Observed With IASI

Author(s):
Bouillon, M.; Safieddine, S.; Clerbaux, C.
Publication title: Journal of Geophysical Research: Atmospheres
2023
 | Volume: 128 | Issue: 17
2023
DOI: 10.1029/2023JD038692
Abstract:
Sudden Stratospheric Warming events (SSW) are extreme phenomena during which stratospheric temperature can increase by tens of degrees in a few days. … Sudden Stratospheric Warming events (SSW) are extreme phenomena during which stratospheric temperature can increase by tens of degrees in a few days. They are due to the propagation and breaking of the planetary waves, leading to a perturbation of the polar vortex. SSWs also influence polar ozone concentrations and midlatitude weather. The Infrared Atmospheric Sounding Interferometers (IASI) monitor atmospheric composition and temperature globally since 2007, and they are ideal to observe the changes of temperature and ozone during SSWs. Since the launch of the first IASI, there have been several SSWs in the Northern Hemisphere, including eight major events that are investigated in this study. We find that during major SSWs, the temperature anomaly propagates from 10 hPa to the lower stratosphere and the maximum anomaly at 200 hPa is correlated to the maximum anomaly at 10 hPa. During these events, negative anomalies of temperature in Europe and Russia and positive anomalies in Canada and Greenland are often observed at 750 hPa. The cold air outbreaks that usually follow major SSWs are responsible for anomalies of −15 K. Finally, we look at the evolution of the total ozone column following major events. Major SSWs lead to higher springtime ozone concentrations and the ozone anomaly in March is correlated to the duration of the positive temperature anomaly at 10 hPa. These results show the potential of the IASI mission and its successors, IASI-New Generation, for the study of SSWs and their effects on weather and atmospheric composition. © 2023 The Authors. more
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Summer snow on Arctic sea ice modulated by the Arctic Oscillation

Author(s):
Webster, M.A.; Riihelä, A.; Kacimi, S.; Ballinger, T.J.; Blanchard-Wrigglesworth, E.; Parker, C.L.; Boisvert, L.
Publication title: Nature Geoscience
2024
 | Volume: 17 | Issue: 10
2024
DOI: 10.1038/s41561-024-01525-y
Abstract:
Since the 1970s, Arctic sea ice has undergone unprecedented change, becoming thinner, less extensive and less resilient to summer melt. Snow’s high al… Since the 1970s, Arctic sea ice has undergone unprecedented change, becoming thinner, less extensive and less resilient to summer melt. Snow’s high albedo greatly reduces solar absorption in sea ice and the upper ocean, which mitigates sea–ice melt and ocean warming. However, the drivers of summertime snow depth variability are unknown. The Arctic Oscillation is a mode of natural climate variability, influencing Arctic snowfall and air temperatures. Thus, it may affect summertime snow conditions on Arctic sea ice. Here we examine the role of the Arctic Oscillation in summer snow depth variability on Arctic sea ice in 1980–2020 using atmospheric reanalysis, snow modelling and satellite data. The positive phase leads to greater snow accumulation, ranging up to ~4.5 cm near the North Pole, and higher surface albedo in summer. There are more intense, frequent Arctic cyclones, cooler temperatures aloft and greater snowfall relative to negative and neutral phases; these conditions facilitate a more persistent summer snow cover, which may lessen sea-ice melt and ocean warming. The Arctic Oscillation influence on summertime snow weakens after 2007, which suggests that future warming and Arctic sea-ice loss might modify the relationship between the Arctic Oscillation and snow on Arctic sea ice. © The Author(s) 2024. more
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Superparameterised cloud effects in the EMAC general circulation model (v2.50) - Influences of model configuration

Author(s):
Rybka, H.; Tost, H.
Publication title: Geoscientific Model Development
2020
 | Volume: 13 | Issue: 6
2020
DOI: 10.5194/gmd-13-2671-2020
Abstract:
A new module has been implemented in the fifth generation of the ECMWF/Hamburg (ECHAM5)/Modular Earth Submodel System (MESSy) Atmospheric Chemistry (E… A new module has been implemented in the fifth generation of the ECMWF/Hamburg (ECHAM5)/Modular Earth Submodel System (MESSy) Atmospheric Chemistry (EMAC) model that simulates cloud-related processes on a much smaller grid. This so-called superparameterisation acts as a replacement for the convection parameterisation and large-scale cloud scheme. The concept of embedding a cloud-resolving model (CRM) inside of each grid box of a general circulation model leads to an explicit representation of cloud dynamics. The new model component is evaluated against observations and the conventional usage of EMAC using a convection parameterisation. In particular, effects of applying different configurations of the superparameterisation are analysed in a systematical way. Consequences of changing the CRM's orientation, cell size and number of cells range from regional differences in cloud amount up to global impacts on precipitation distribution and its variability. For some edge case setups, the analysed climate state of superparameterised simulations even deteriorates from the mean observed energy budget. In the current model configuration, different climate regimes can be formed that are mainly driven by some of the parameters of the CRM. Presently, the simulated total cloud cover is at the lower edge of the CMIP5 model ensemble. However, certain "tuning" of the current model configuration could improve the slightly underestimated cloud cover, which will result in a shift of the simulated climate. The simulation results show that especially tropical precipitation is better represented with the superparameterisation in the EMAC model configuration. Furthermore, the diurnal cycle of precipitation is heavily affected by the choice of the CRM parameters. However, despite an improvement of the representation of the continental diurnal cycle in some configurations, other parameter choices result in a deterioration compared to the reference simulation using a conventional convection parameterisation. The ability of the superparameterisation to represent latent and sensible heat flux climatology is independent of the chosen CRM setup. Evaluation of in-atmosphere cloud amounts depending on the chosen CRM setup shows that cloud development can significantly be influenced on the large scale using a too-small CRM domain size. Therefore, a careful selection of the CRM setup is recommended using 32 or more CRM cells to compensate for computational expenses. © 2020 Copernicus GmbH. All rights reserved. more
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