Understanding snow bedform formation by adding sintering to a cellular automata model The Cryosphere DOI 10.5194/tc-13-3239-2019 17 December 2019 Snow surfaces, under the action of wind, form beautiful shapes such as waves and dunes. This study is the first ever study to simulate these shapes using a state-of-the-art numerical modelling tool. While these beautiful and ephemeral shapes on snow surfaces are fascinating from a purely aesthetic point of view, they are also critical in regulating the transfer of heat and mass between the atmosphere and snowpacks, thus being of huge importance to the Earth system. Read more
A comparative assessment of the uncertainties of global surface ocean CO2 estimates using a machine-learning ensemble (CSIR-ML6 version 2019a) – have we hit the wall? Geoscientific Model Development DOI 10.5194/gmd-12-5113-2019 17 December 2019 The ocean plays a vital role in mitigating climate change by taking up atmospheric carbon dioxide (CO2). Historically sparse ship-based measurements of surface ocean CO2make direct estimates of CO2exchange changes unreliable. We introduce a machine-learning ensemble approach to fill these observational gaps. Our method performs incrementally better relative to past methods, leading to our hypothesis that we are perhaps reaching the limitation of machine-learning algorithms’ capability. CSIR-ML6 version 2019a) – have we hit the wall?">Read more
On the seasonal variation in observed size distributions in northern Europe and their changes with decreasing anthropogenic emissions in Europe: climatology and trend analysis based on 17 years of data from Aspvreten, Sweden Atmospheric Chemistry and Physics DOI 10.5194/acp-19-14849-2019 17 December 2019 In this study we explore 17 years of aerosol number size distribution data (10–390 nm) observed at Aspvreten (58.8° N, 17.4° E, 25 m a.s.l.). The station, located in northern Europe, is representative of rural background conditions. The study focused on identifying trends in aerosol number size distribution properties. The study shows that total number has decreased by 30 % and aerosol submicron mass by 50 % on average. Observed trends vary strongly with both season and particle size. Read more
Stepwise chemical abrasion–isotope dilution–thermal ionization mass spectrometry with trace element analysis of microfractured Hadean zircon Geochronology DOI 10.5194/gchron-1-85-2019 17 December 2019 The oldest known minerals on Earth are Hadean (> 4.0 Ga) zircons from the Jack Hills, Australia. We present the first application to such Hadean zircons of stepwise chemical abrasion–isotope dilution–thermal ionization mass spectrometry with trace element analysis (stepwise CA-ID-TIMS-TEA). We examine the evolution in the U–Pb age and trace element chemistry of zircon domains accessed by successive chemical abrasion steps in the context of the geologic history of the Jack Hills zircons. Read more
Societal breakdown as an emergent property of large-scale behavioural models of land use change Earth System Dynamics DOI 10.5194/esd-10-809-2019 10 December 2019 Concerns are growing that human activity will lead to social and environmental breakdown, but it is hard to anticipate when and where such breakdowns might occur. We developed a new model of land management decisions in Europe to explore possible future changes and found that decision-making that takes into account social and environmental conditions can produce unexpected outcomes that include societal breakdown in challenging conditions. Read more
First reported case of thunderstorm asthma in Israel Natural Hazards and Earth System Sciences DOI 10.5194/nhess-19-2715-2019 10 December 2019 During severe thunderstorms, cold outflows can eject pollen and dust particles from the surface, releasing allergens and causingthunderstorm asthmaepidemics in sensitive populations. We report the first case in Israel that occurred on 25 October 2015. The emergency room presentation records from three hospitals in central Israel showed a clear increase in patients with respiratory complaints immediately after the passage of a massive super-cell thunderstorm in the area. Read more
The diurnal cycle of the smoky marine boundary layer observed during August in the remote southeast Atlantic Atmospheric Chemistry and Physics DOI 10.5194/acp-19-14493-2019 10 December 2019 Boundary layer (BL) semi-direct effects in the remote SE Atlantic are investigated using LASIC field measurements and satellite retrievals. Low-cloud cover and cloud liquid water path decrease with increasing smoke loadings in the BL. Daily-mean surface-based mixed layer is warmer by 0.5 K, moisture accumulates near the surface throughout the night, and the BL deepens by 200 m, with LWPs and cloud top heights increasing, in the sunlit morning hours, as part of the smoke-altered BL diurnal cycle. Read more
Can we use sea surface temperature and productivity proxy records to reconstruct Ekman upwelling? Climate of the Past DOI 10.5194/cp-15-1985-2019 10 December 2019 We test two assumptions that are often made in paleoclimate studies by using observations and ask whether temperature and productivity proxy records in the Southern California Current can be used to reconstruct Ekman upwelling. By examining the covariation between alongshore wind stress, temperature, and productivity, we found that the dominant covarying pattern does not reflect Ekman upwelling. Other upwelling patterns found are timescale dependent. Multiple proxies can improve reconstruction. Read more
Large-scale particulate air pollution and chemical fingerprint of volcanic sulfate aerosols from the 2014–2015 Holuhraun flood lava eruption of Bárðarbunga volcano (Iceland) Atmospheric Chemistry and Physics DOI 10.5194/acp-19-14253-2019 3 December 2019 This study, benefiting especially from recently developed mass spectrometry observations of aerosols, highlights unknown properties of volcanic sulfates in the troposphere. It shows their specific chemical fingerprint, distinct from those of freshly emitted industrial sulfates and background aerosols. We also demonstrate the large-scale persistence of the volcanic sulfate pollution over weeks. Hence, these results cast light on the impact of tropospheric eruptions on air quality and climate. Read more
Low-temperature triple-capillary cryostat for ice crystal growth studies Atmospheric Measurement Techniques DOI 10.5194/amt-12-6143-2019 3 December 2019 We have built a triple-capillary cryostat designed to reduce potential instrumental effects that may have influenced earlier measurements and to improve our understanding of the processes responsible for ice crystal shapes and sizes. In this cryostat, a crystal forms on one of three well-separated and ultrafine capillaries. In this paper we describe the new instrument and present several observations made using the instrument to illustrate the instrument’s advantages. Read more
