Random and externally controlled occurrences of Dansgaard–Oeschger events Climate of the Past DOI 10.5194/cp-14-609-2018 16 May 2018 The climate of the last glacial period was frequently interrupted by rapid warming events, the cause of which is still unknown. One open question is whether the occurrence of events is random or externally controlled. We studied the temporal characteristics of warm and cold phases using statistical null models and find that they are well described as random processes modulated by two different external climate factors. This may help distinguish physical mechanisms for rapid climate change. Read more
Effects of climatic seasonality on the isotopic composition of evaporating soil waters Hydrology and Earth System Sciences DOI 10.5194/hess-22-2881-2018 15 May 2018 Evaporation causes the isotopic composition of soil water to become different from that of the original precipitation source. If multiple samples originating from the same source are available, they can be used to reconstruct the original source composition. However, soil water is influenced by seasonal variability in both precipitation sources and evaporation patterns. We show that this variability, if not accounted for, can lead to biased estimates of the precipitation source water. Read more
Crossing the chasm: how to develop weather and climate models for next generation computers? Geoscientific Model Development DOI 10.5194/gmd-11-1799-2018 8 May 2018 Weather and climate models consist of complex software evolving in response to both scientific requirements and changing computing hardware. After years of relatively stable hardware, more diversity is arriving. It is possible that this hardware diversity and the pace of change may lead to an inability for modelling groups to manage their software development. This “chasm” between aspiration and reality may need to be bridged by large community efforts rather than traditional “in-house” efforts. Read more
Contrails and their impact on shortwave radiation and photovoltaic power production – a regional model study Atmospheric Chemistry and Physics DOI 10.5194/acp-18-6393-2018 7 May 2018 A numerical model also used for operational weather forecast was applied to investigate the impact of contrails and contrail cirrus on the radiative fluxes at the earth’s surface. Accounting for contrails produced by aircraft enables the model to simulate high clouds that are otherwise missing. In a case study, we find that the effect of these extra clouds is to reduce the incoming shortwave radiation at the surface as well as the production of photovoltaic power by up to 10 %. Read more
Technical note: Open-paleo-data implementation pilot – the PAGES 2k special issue Climate of the Past DOI 10.5194/cp-14-593-2018 3 May 2018 We explain the procedure used to attain a high and consistent level of data stewardship across a special issue of the journal Climate of the Past. We discuss the challenges related to (1) determining which data are essential for public archival, (2) using data generated by others, and (3) understanding data citations. We anticipate that open-data sharing in paleo sciences will accelerate as the advantages become more evident and as practices that reduce data loss become the accepted convention. Read more
Vertical wind velocity measurements using a five-hole probe with remotely piloted aircraft to study aerosol–cloud interactions Atmospheric Measurement Techniques DOI 10.5194/amt-11-2583-2018 3 May 2018 Remotely piloted aircraft systems (RPAS), commonly called UAVs, are used in atmospheric science for in situ measurements. The presented work shows wind measurements from a five-hole probe on an RPAS. Comparisons with other instruments (sonic anemometer and cloud radar) show good agreement, validating the RPAS measurements. In situ vertical wind measurements at cloud base are highlighted because they are a major parameter needed for simulating aerosol–cloud interactions, though rarely collected. Read more
Brief communication: Unabated wastage of the Juneau and Stikine icefields (southeast Alaska) in the early 21st century The Cryosphere DOI 10.5194/tc-12-1523-2018 27 April 2018 Two recent studies suggested a slowdown in mass loss after 2000 of the Juneau and Stikine icefields, accounting for 10% of the total ice cover in Alaska. Here, the ASTER-based geodetic mass balances are revisited, carefully avoiding the use of the SRTM DEM, because of the unknown penetration depth of the SRTM C-band radar signal. We find strongly negative mass balances from 2000 to 2016 for both icefields, in agreement with airborne laser altimetry. Mass losses are thus continuing unabated. Read more
A new method, with application, for analysis of the impacts on flood risk of widely distributed enhanced hillslope storage Hydrology and Earth System Sciences DOI 10.5194/hess-22-2589-2018 27 April 2018 Flooding is a significant hazard and extreme events in recent years have focused attention on effective means of reducing its risk. An approach known as natural flood management (NFM) seeks to increase flood resilience by a range of measures that work with natural processes. The paper develops a modelling approach to assess one type NFM of intervention – distributed additional hillslope storage features – and demonstrates that more strategic placement is required than has hitherto been applied. Read more
Adaption of an array spectroradiometer for total ozone column retrieval using direct solar irradiance measurements in the UV spectral range Atmospheric Measurement Techniques DOI 10.5194/amt-11-2477-2018 27 April 2018 A compact array spectroradiometer technology that enables precise and robust measurements of UV spectral irradiance is presented. We show that this instrument can retrieve total ozone column (TOC) accurately. The internal stray light, which is often the limiting factor for measurements in the UV spectral range, is physically reduced so that no other stray-light reduction methods are needed. During an international total ozone measurement intercomparison, the high quality was verified. Read more
Global evaluation and calibration of a passive air sampler for gaseous mercury Atmospheric Chemistry and Physics DOI 10.5194/acp-18-5905-2018 26 April 2018 A new passive air sampler for gaseous mercury was tested at 20 sites on four continents. These sites have in common that they use the state-of-the-art active air sampling technique for gaseous mercury on a continuous basis and therefore allow for an evaluation and calibration of the passive sampler. The sampler proved to work exceptionally well, with a precision and accuracy on par with the active instrument and better than what has previously been achieved with passive samplers. Read more
Novel pathway of SO2 oxidation in the atmosphere: reactions with monoterpene ozonolysis intermediates and secondary organic aerosol Atmospheric Chemistry and Physics DOI 10.5194/acp-18-5549-2018 24 April 2018 Synergistic effects between SOA formation and SO2 oxidation through Criegee chemistry and reactive uptake by organic peroxides were observed. The relative importance of these two pathways (Criegee vs. peroxide) varies with relative humidity. The latter SO2 loss mechanism to organic peroxides in SOA has not previously been identified. Our results suggest a new pathway of atmospheric SO2 oxidation, which may contribute to the missing mechanisms of high-sulfate production in the polluted areas. Read more
Using satellite measurements of N2O to remove dynamical variability from HCl measurements Atmospheric Chemistry and Physics DOI 10.5194/acp-18-5691-2018 24 April 2018 Detecting trends in short data sets of stratospheric molecules is difficult because of variability due to dynamical fluctuations. We suggest that one way around this difficulty is using the measurements of one molecule to remove dynamical variability from the measurements of another molecule. We illustrate this using Aura MLS measurements of N2O to help us sort out issues in the determination of trends in HCl. This shows that HCl is decreasing throughout the middle stratosphere as expected. Read more
The influence of atmospheric grid resolution in a climate model-forced ice sheet simulation The Cryosphere DOI 10.5194/tc-12-1499-2018 23 April 2018 Coupled climate–ice sheet simulations have been growing in popularity in recent years. Experiments of this type are however challenging as ice sheets evolve over multi-millennial timescales, which is beyond the practical integration limit of most Earth system models. A common method to increase model throughput is to trade resolution for computational efficiency (compromise accuracy for speed). Here we analyze how the resolution of an atmospheric general circulation model (AGCM) influences the simulation quality in a stand-alone ice sheet model. Four identical AGCM simulations of the Last Glacial Maximum (LGM) were run at different horizontal resolutions: T85 (1.4∘), T42 (2.8∘), T31 (3.8∘), and T21 (5.6∘). These simulations were subsequently used as forcing of an ice sheet model. Read more
Considering the future of anthropogenic gas-phase organic compound emissions and the increasing influence of non-combustion sources on urban air quality Atmospheric Chemistry and Physics DOI 10.5194/acp-18-5391-2018 20 April 2018 Following decades of successful regulatory policies focused on combustion-related sources (e.g. motor vehicles), emissions from non-combustion sources have become increasingly important for urban air quality. Using multiple approaches, we demonstrate that emissions from consumer, commercial, and industrial products and materials have become prominent contributors to the formation of photochemical smog (i.e. secondary organic particulate matter and ozone) and its associated health effects. Read more
Moving beyond the age–depth model paradigm in deep-sea palaeoclimate archives: dual radiocarbon and stable isotope analysis on single foraminifera Climate of the Past DOI 10.5194/cp-14-515-2018 20 April 2018 Palaeoclimate reconstructions from deep-sea sediment archives provide valuable insight into past rapid climate change, but only a small proportion of the ocean is suitable for such reconstructions using the existing state of the art, i.e. the age–depth approach. We use dual radiocarbon (14C) and stable isotope analysis on single foraminifera to bypass the long-standing age–depth approach, thus facilitating past ocean chemistry reconstructions from vast, previously untapped ocean areas. Read more
Mercury distribution and transport in the North Atlantic Ocean along the Geotraces-GA01 transect Biogeosciences DOI 10.5194/bg-15-2309-2018 19 April 2018 We first report the mercury distribution in the water section across the subpolar and subtropical gyres of the North Atlantic Ocean (GEOTRACES-GA01 transect). It allows the characterisation of various seawater types in terms of mercury content and the quantification of mercury transport associated with the Atlantic Meridional Overturning Circulation. It shows the nutrient-like biogeochemical behaviour of mercury in this ocean. Read more
Interannual drivers of the seasonal cycle of CO2 in the Southern Ocean Biogeosciences DOI 10.5194/bg-15-2361-2018 19 April 2018 The Southern Ocean accounts for a large portion of the variability in oceanic CO2 uptake. However, the drivers of these changes are not understood due to a lack of observations. In this study, we used an ensemble of gap-filling methods to estimate surface CO2. We found that winter was a more important driver of longer-term variability driven by changes in wind stress. Summer variability of CO2 was driven primarily by increases in primary production. Read more
Brief communication: Loss of life due to Hurricane Harvey Natural Hazards and Earth System Sciences DOI 10.5194/nhess-18-1073-2018 19 April 2018 An analysis was made of the loss of life directly caused by Hurricane Harvey. Information was collected for 70 fatalities that occurred directly due to the event. Most of the fatalities occurred in the greater Houston area, which was most severely affected by extreme rainfall and heavy flooding. The majority of fatalities in this area were recovered outside the designated 100- and 500-year flood zones. Most fatalities occurred due to drowning (81 %), particularly in and around vehicles. Read more
Regional evapotranspiration from an image-based implementation of the Surface Temperature Initiated Closure (STIC1.2) model and its validation across an aridity gradient in the conterminous US Hydrology and Earth System Sciences DOI 10.5194/hess-22-2311-2018 18 April 2018 We report the first ever regional-scale implementation of the Surface Temperature Initiated Closure (STIC1.2) model for mapping evapotranspiration (ET) using MODIS land surface and gridded climate datasets to overcome the existing uncertainties in aerodynamic temperature and conductance estimation in global ET models. Validation and intercomparison with SEBS and MOD16 products across an aridity gradient in the US manifested better ET mapping potential of STIC1.2 in different climates and biomes. Read more
A protocol for the intercomparison of marine fishery and ecosystem models: Fish-MIP v1.0 Geoscientific Model Development DOI 10.5194/gmd-11-1421-2018 13 April 2018 Model intercomparison studies in the climate and Earth sciences communities have been crucial for strengthening future projections. Given the speed and magnitude of anthropogenic change in the marine environment, the time is ripe for similar comparisons among models of fisheries and marine ecosystems. We describe the Fisheries and Marine Ecosystem Model Intercomparison Project, which brings together the marine ecosystem modelling community to inform long-term projections of marine ecosystems. Read more