Australian wildfire smoke in the stratosphere: the decay phase in 2020/2021 and impact on ozone depletion Atmospheric Chemistry and Physics DOI 10.5194/acp-22-7417-2022 24 August 2022 We present and discuss 2 years of long-term lidar observations of the largest stratospheric perturbation by wildfire smoke ever observed. The smoke originated from the record-breaking Australian fires in 2019–2020 and affects climate conditions and even the ozone layer in the Southern Hemisphere. The obvious link between dense smoke occurrence in the stratosphere and strong ozone depletion found in the Arctic and in the Antarctic in 2020 can be regarded as a new aspect of climate change. Read more
New insights on the prevalence of drizzle in marine stratocumulus clouds based on a machine learning algorithm applied to radar Doppler spectra Atmospheric Chemistry and Physics DOI 10.5194/acp-22-7405-2022 22 August 2022 Drizzle (small rain droplets) is an important component of warm clouds; however, its existence is poorly understood. In this study, we capitalized on a machine-learning algorithm to develop a drizzle detection method. We applied this algorithm to investigate drizzle occurrence and found out that drizzle is far more ubiquitous than previously thought. This study demonstrates the ubiquitous nature of drizzle in clouds and will improve understanding of the associated microphysical process. Read more
Glacial runoff buffers droughts through the 21st century Earth System Dynamics DOI 10.5194/esd-13-935-2022 19 August 2022 Global climate models suggest that droughts could worsen over the coming century. In mountain basins with glaciers, glacial runoff can ease droughts, but glaciers are retreating worldwide. We analysed how one measure of drought conditions changes when accounting for glacial runoff that changes over time. Surprisingly, we found that glacial runoff can continue to buffer drought throughout the 21st century in most cases, even as the total amount of runoff declines. Read more
Downscaling of climate change scenarios for a high-resolution, site-specific assessment of drought stress risk for two viticultural regions with heterogeneous landscapes Earth System Dynamics DOI 10.5194/esd-13-911-2022 17 August 2022 We modelled water budget developments of viticultural growing regions on the spatial scale of individual vineyard plots with respect to landscape features like the available water capacity of the soils, slope, and aspect of the sites. We used an ensemble of climate simulations and focused on the occurrence of drought stress. The results show a high bandwidth of projected changes where the risk of potential drought stress becomes more apparent in steep-slope regions. Read more
Multi-century dynamics of the climate and carbon cycle under both high and net negative emissions scenarios Earth System Dynamics DOI 10.5194/esd-13-885-2022 15 August 2022 We explore the long-term dynamics of Earth’s climate and carbon cycles under a pair of contrasting scenarios to the year 2300 using six models that include both climate and carbon cycle dynamics. One scenario assumes very high emissions, while the second assumes a peak in emissions, followed by rapid declines to net negative emissions. We show that the models generally agree that warming is roughly proportional to carbon emissions but that many other aspects of the model projections differ. Read more
Gaps in network infrastructure limit our understanding of biogenic methane emissions for the United States Biogeosciences DOI 10.5194/bg-19-2507-2022 12 August 2022 To understand the CH4 flux potential of natural ecosystems and agricultural lands in the United States of America, a multi-scale CH4 observation network focused on CH4 flux rates, processes, and scaling methods is required. This can be achieved with a network of ground-based observations that are distributed based on climatic regions and land cover. Read more
Currents generated by the sea breeze in the southern Caspian Sea Ocean Science DOI 10.5194/os-18-675-2022 10 August 2022 The smaller thermal heat capacity of land relative to the sea results in land–sea thermal gradients with a daily cycle, called sea breeze systems, with the same daily periodicity. Since tides in the Caspian, as the largest enclosed basin with a persistent sea breeze system through the year, are very weak we found that most of the higher-frequency variations in coastal currents are a response to the sea breeze system. Read more
Training a supermodel with noisy and sparse observations: a case study with CPT and the synch rule on SPEEDO – v.1 Geoscientific Model Development DOI 10.5194/gmd-15-3831-2022 8 August 2022 In this study, we present a novel formulation to build a dynamical combination of models, the so-called supermodel, which needs to be trained based on data. Previously, we assumed complete and noise-free observations. Here, we move towards a realistic scenario and develop adaptations to the training methods in order to cope with sparse and noisy observations. The results are very promising and shed light on how to apply the method with state of the art general circulation models. Read more
Lévy noise versus Gaussian-noise-induced transitions in the Ghil–Sellers energy balance model Nonlinear Processes in Geophysics DOI 10.5194/npg-29-183-2022 5 August 2022 In most of the investigations on metastable systems, the stochastic forcing is modulated by Gaussian noise. Lévy noise laws, which describe jump processes, have recently received a lot of attention, but much less is known. We study stochastic versions of the Ghil–Sellers energy balance model, and we highlight the fundamental difference between how transitions are performed between the competing warm and snowball states, depending on whether Gaussian or Lévy noise acts as forcing. Read more
Assessing the consequences of including aerosol absorption in potential stratospheric aerosol injection climate intervention strategies Atmospheric Chemistry and Physics DOI 10.5194/acp-22-6135-2022 3 August 2022 Simulations are presented investigating the influence of moderately absorbing aerosol in the stratosphere to combat the impacts of climate change. A number of detrimental impacts are noted compared to sulfate aerosol, including (i) reduced cooling efficiency, (ii) increased deficits in global precipitation, (iii) delays in the recovery of the stratospheric ozone hole, and (iv) disruption of the stratospheric circulation and the wintertime storm tracks that impact European precipitation. Read more
The onset of the spring phytoplankton bloom in the coastal North Sea supports the Disturbance Recovery Hypothesis Biogeosciences DOI 10.5194/bg-19-2417-2022 1 August 2022 In oceanic waters, the accumulation of phytoplankton biomass in winter, when light still limits growth, is attributed to a decrease in grazing as the mixed layer deepens. However, in coastal areas, it is not clear whether winter biomass can accumulate without this deepening. Using 21 years of weekly data, we found that in the Scottish coastal North Sea, the seasonal increase in light availability triggers the accumulation of phytoplankton biomass in winter, when light limitation is strongest. Read more
Warming of 0.5 °C may cause double the economic loss and increase the population affected by floods in China Natural Hazards and Earth System Sciences DOI 10.5194/nhess-22-1577-2022 29 July 2022 The impact of extreme events is increasing with global warming. Based on future scenario data and an improved quantitative assessment model of natural-disaster risk, this study analyses the spatial and temporal patterns of floods in China at 1.5 °C and 2 °C of global warming, quantitatively assesses the socioeconomic risks posed by floods, and determines the integrated risk levels. Global warming of 1.5 °C can effectively reduce the population affected and the economic risks of floods. Read more
Projections of hydrofluorocarbon (HFC) emissions and the resulting global warming based on recent trends in observed abundances and current policies Atmospheric Chemistry and Physics DOI 10.5194/acp-22-6087-2022 27 July 2022 The emissions of hydrofluorocarbons (HFCs) have increased significantly in the past as a result of the phasing out of ozone-depleting substances. Observations indicate that HFCs are used much less in certain refrigeration applications than previously projected. Current policies are projected to reduce emissions and the surface temperature contribution of HFCs from 0.28–0.44 °C to 0.14–0.31 °C in 2100. The Kigali Amendment is projected to reduce the contributions further to 0.04 °C in 2100. Read more
Marine heatwaves in the Arabian Sea Ocean Science DOI 10.5194/os-18-639-2022 25 July 2022 Marine heatwaves refer to discrete, prolonged warm ocean conditions known to cause severe destruction in marine ecosystems. We find that coastal waters off the west coast of India have experienced a rapid multifold increase in heatwave days since the early 80s. This resulted in more frequent and longer marine heatwave events in the last decade. We show that the rapid warming in the Arabian Sea in the last decade is the primary cause of the observed enhanced heatwave events in this basin. Read more
Using neural networks to improve simulations in the gray zone Nonlinear Processes in Geophysics DOI 10.5194/npg-29-171-2022 22 July 2022 Our regional numerical weather prediction models run at kilometer-scale resolutions. Processes that occur at smaller scales not yet resolved contribute significantly to the atmospheric flow. We use a neural network (NN) to represent the unresolved part of physical process such as cumulus clouds. We test this approach on a simplified, yet representative, 1D model and find that the NN corrections vastly improve the model forecast up to a couple of days. Read more
Establishing an integrated workflow identifying and linking surface and subsurface lineaments for mineral exploration under cover: example from the Gawler Craton, South Australia Solid Earth DOI 10.5194/se-13-827-2022 20 July 2022 The insights of this study will help to improve our understanding on how to identify basement linear structures and how these lineaments could be related to surface lineaments or geology in the context of the Central Gawler Craton, South Australia. This contribution suggests a targeting concept for identifying the structural footprint of subsurface mineral systems by combining remotely sensed data corresponding to surface and subsurface features. Read more
HESS Opinions: Chemical transport modeling in subsurface hydrological systems – space, time, and the “holy grail” of “upscaling” Hydrology and Earth System Sciences DOI 10.5194/hess-26-2161-2022 18 July 2022 Extensive efforts have focused on quantifying conservative chemical transport in geological formations. We assert that an explicit accounting of temporal information, under uncertainty, in addition to spatial information, is fundamental to an effective modelling formulation. We further assert that efforts to apply chemical transport equations at large length scales, based on measurements and model parameter values relevant to significantly smaller length scales, are an unattainable “holy grail”. Read more
Technical Note: Past and future warming – direct comparison on multi-century timescales Climate of the Past DOI 10.5194/cp-18-911-2022 15 July 2022 Global mean surface temperatures are rising to levels unprecedented in over 100 000 years. This conclusion takes into account both recent global warming and likely future warming, which thereby enables a direct comparison with paleotemperature reconstructions on multi-century timescales. Read more
The Lehtinen–Pirjola method modified for efficient modelling of geomagnetically induced currents in multiple voltage levels of a power network Annales Geophysicae DOI 10.5194/angeo-40-205-2022 13 July 2022 The Lehtinen-Pirjola (LP) method is widely used for modelling geomagnetically induced currents (GIC) in power systems but was developed when the main aim was to model GIC in only the highest voltage level of a power network. Here we present a modification to the LP method designed to provide an efficient method for modelling GIC in multiple voltage levels. We also show how existing software can easily be converted to the new method and provide examples of calculations. Read more
Coupling human and natural systems for sustainability: experience from China’s Loess Plateau Earth System Dynamics DOI 10.5194/esd-13-795-2022 11 July 2022 To understand the dynamics of a coupled human and natural system (CHANS) and promote its sustainability, we propose a conceptual “pattern-process-service-sustainability” cascade framework. The use of this framework is systematically illustrated by a review of CHANS research experience in China’s Loess Plateau in terms of coupling landscape patterns and ecological processes, linking ecological processes to ecosystem services, and promoting social-ecological sustainability. Read more