Assimilation of DAWN Doppler wind lidar data during the 2017 Convective Processes Experiment (CPEX): impact on precipitation and flow structure Atmospheric Measurement Techniques DOI 10.5194/amt-14-3333-2021 25 June 2021 The assimilation of airborne-based three-dimensional winds into a mesoscale weather forecast model resulted in better agreement with airborne radar-derived precipitation 3-D structure at later model time steps. More importantly, there was also a discernible impact on the resultant wind and moisture structure, in accord with independent analysis of the wind structure and external satellite observations. DAWN Doppler wind lidar data during the 2017 Convective Processes Experiment (CPEX): impact on precipitation and flow structure">Read more
Glacier detachments and rock-ice avalanches in the Petra Pervogo range, Tajikistan (1973–2019) Natural Hazards and Earth System Sciences DOI 10.5194/nhess-21-1409-2021 24 June 2021 A cluster of 13 large mass flow events including five detachments of entire valley glaciers was observed in the Petra Pervogo range, Tajikistan, in 1973–2019. The local clustering provides additional understanding of the influence of temperature, seismic activity, and geology. Most events occurred in summer of years with mean annual air temperatures higher than the past 46-year trend. The glaciers rest on weak bedrock and are rather short, making them sensitive to friction loss due to meltwater. Read more
Regional variation in the effectiveness of methane-based and land-based climate mitigation options Earth System Dynamics DOI 10.5194/esd-12-513-2021 23 June 2021 We model greenhouse gas emission scenarios consistent with limiting global warming to either 1.5 or 2 °C above pre-industrial levels. We quantify the effectiveness of methane emission control and land-based mitigation options regionally. Our results highlight the importance of reducing methane emissions for realistic emission pathways that meet the global warming targets. For land-based mitigation, growing bioenergy crops on existing agricultural land is preferable to replacing forests. Read more
Atmospheric extremes caused high oceanward sea surface slope triggering the biggest calving event in more than 50 years at the Amery Ice Shelf The Cryosphere DOI 10.5194/tc-15-2147-2021 22 June 2021 The unexpected September 2019 calving event from the Amery Ice Shelf, the largest since 1963 and which occurred almost a decade earlier than expected, was triggered by atmospheric extremes. Explosive twin polar cyclones provided a deterministic role in this event by creating oceanward sea surface slope triggering the calving. The observed record-anomalous atmospheric conditions were promoted by blocking ridges and Antarctic-wide anomalous poleward transport of heat and moisture. Read more
Heterogeneous interactions between SO2 and organic peroxides in submicron aerosol Atmospheric Chemistry and Physics DOI 10.5194/acp-21-6647-2021 21 June 2021 Discrepancies between atmospheric modeling and field observations, especially in highly polluted cities, have highlighted the lack of understanding of sulfate formation mechanisms and kinetics. Here, we directly quantify the reactive uptake coefficient of SO2 onto organic peroxides and study the important governing factors. The SO2 uptake rate was observed to depend on RH, peroxide amount and reactivity, pH, and ionic strength, which provides a framework to better predict sulfate formation. Read more
On the phenomenon of the blue sun Climate of the Past DOI 10.5194/cp-17-969-2021 18 June 2021 This study investigates the physical processes leading to the rare phenomenon of the sun appearing blue or green. The phenomenon is caused by anomalous scattering by, e.g., volcanic or forest fire aerosols. Unlike most other studies, our study includes a full treatment of the effect of Rayleigh scattering on the colour of the sun. We investigate different factors and revisit a historic example, i.e. the Canadian forest fires in 1950, that led to blue sun events in different European countries. Read more
Effects of Earth system feedbacks on the potential mitigation of large-scale tropical forest restoration Biogeosciences DOI 10.5194/bg-18-2627-2021 17 June 2021 Estimates of large-scale tree planting and forest restoration as a carbon sequestration tool typically miss a crucial aspect: the Earth system response to the increased land carbon sink from new vegetation. We assess the impact of tropical forest restoration using an Earth system model under a scenario that limits warming to 2 °C. Almost two-thirds of the carbon impact of forest restoration is offset by negative carbon cycle feedbacks, suggesting a more modest benefit than in previous studies. Read more
Revision of the World Meteorological Organization Global Atmosphere Watch (WMO/GAW) CO2 calibration scale Atmospheric Measurement Techniques DOI 10.5194/amt-14-3015-2021 16 June 2021 We have recently revised the carbon dioxide calibration scale used by numerous laboratories that measure atmospheric CO2. The revision follows from an improved understanding of the manometric method used to determine the absolute amount of CO2 in an atmospheric air sample. The new scale is 0.18 μmol mol−1 (ppm) greater than the previous scale at 400 ppm CO2. While this difference is small in relative terms (0.045 %), it is significant in terms of atmospheric monitoring. WMO/GAW) CO2 calibration scale">Read more
Observing the timescales of aerosol–cloud interactions in snapshot satellite images Atmospheric Chemistry and Physics DOI 10.5194/acp-21-6093-2021 15 June 2021 Cloud responses to aerosol are time-sensitive, but this development is rarely observed. This study uses isolated aerosol perturbations from ships to measure this development and shows that macrophysical (width, cloud fraction, detectability) and microphysical (droplet number) properties of ship tracks vary strongly with time since emission, background cloud and meteorological state. This temporal development should be considered when constraining aerosol–cloud interactions with observations. Read more
On the attribution of industrial-era glacier mass loss to anthropogenic climate change The Cryosphere DOI 10.5194/tc-15-1889-2021 14 June 2021 The worldwide retreat of mountain glaciers and consequent loss of ice mass is one of the most obvious signs of a changing climate and has significant implications for the hydrology and natural hazards in mountain landscapes. Consistent with our understanding of the human role in temperature change, we demonstrate that the central estimate of the size of the human-caused mass loss is essentially 100 % of the observed loss. This assessment resolves some important inconsistencies in the literature. Read more
