Quantifying hail size distributions from the sky – application of drone aerial photogrammetry Atmospheric Measurement Techniques DOI 10.5194/amt-13-747-2020 25 February 2020 Collecting measurements of hail size and shape is difficult due to the infrequent and dangerous nature of hailstorms. To improve upon this, a new technique called HailPixel is introduced for measuring hail using aerial imagery collected by a drone. A combination of machine learning and computer vision methods is used to extract the shape of thousands of hailstones from the aerial imagery. The improved statistics from the much larger HailPixel dataset show significant benefits. Read more
Surface water as a cause of land degradation from dryland salinity Hydrology and Earth System Sciences DOI 10.5194/hess-24-717-2020 25 February 2020 Secondary dryland salinity is a global land degradation issue. Our understanding of causal processes is adapted from wet and hydrologically connected landscapes and concludes that low end-of-catchment runoff indicates land clearing alters water balance in favour of increased infiltration and rising groundwater that bring salts to the surface causing salinity. This study shows surface flows play an important role in causing valley floor recharge and dryland salinity in low-gradient landscapes. Read more
Variations in soil chemical and physical properties explain basin-wideAmazon forest soil carbon concentrations SOIL DOI 10.5194/soil-6-53-2020 20 February 2020 Amazon soils hold as much carbon © as is contained in the vegetation. In this work we sampled soils across 8 different Amazonian countries to try to understand which soil properties control current Amazonian soil C concentrations. We confirm previous knowledge that highly developed soils hold C through clay content interactions but also show a previously unreported mechanism of soil C stabilization in the younger Amazonian soil types which hold C through aluminium organic matter interactions. Read more
A multi-model analysis of teleconnected crop yield variability in a range of cropping systems Earth System Dynamics DOI 10.5194/esd-11-113-2020 20 February 2020 In this study, we analyse the impacts of three major climate oscillations on global crop production. Our results show that maize, rice, soybean, and wheat yields are influenced by climate oscillations to a wide extent and in several important crop-producing regions. We observe larger impacts if crops are rainfed or fully fertilized, while irrigation tends to mitigate the impacts. These results can potentially help to increase the resilience of the global food system to climate-related shocks. Read more
Modal shift in North Atlantic seasonality during the last deglaciation Climate of the Past DOI 10.5194/cp-16-265-2020 18 February 2020 Here, mid-ocean seasonality is resolved through time, using differences in the oxygen isotope composition between individual shells of the commonly used (sub)polar planktonic foraminifera species in ocean-climate reconstruction, N. pachyderma and G. bulloides . Single-specimen isotope measurements during the deglacial period revealed a surprising bimodality, the cause of which was investigated. Read more
Dimensions of marine phytoplankton diversity Biogeosciences DOI 10.5194/bg-17-609-2020 18 February 2020 Phytoplankton are an essential component of the marine food web and earth’s carbon cycle. We use observations, ecological theory and a unique trait-based ecosystem model to explain controls on patterns of marine phytoplankton biodiversity. We find that different dimensions of diversity (size classes, biogeochemical functional groups, thermal norms) are controlled by a disparate combination of mechanisms. This may explain why previous studies of phytoplankton diversity had conflicting results. Read more
A new look at the environmental conditions favorable to secondary ice production Atmospheric Chemistry and Physics DOI 10.5194/acp-20-1391-2020 13 February 2020 This study attempts identification of mechanisms of secondary ice production (SIP) based on the observation of small faceted ice crystals. It was found that in both mesoscale convective systems and frontal clouds, SIP was observed right above the melting layer and extended to the higher altitudes with colder temperatures. A principal conclusion of this work is that the freezing drop shattering mechanism is plausibly accounting for the measured ice concentrations in the observed condition. Read more
Machine learning and soil sciences: a review aided by machine learning tools SOIL DOI 10.5194/soil-6-35-2020 13 February 2020 The application of machine learning (ML) has shown an accelerated adoption in soil sciences. It is a difficult task to manually review all papers on the application of ML. This paper aims to provide a review of the application of ML aided by topic modelling in order to find patterns in a large collection of publications. The objective is to gain insight into the applications and to discuss research gaps. We found 12 main topics and that ML methods usually perform better than traditional ones. Read more
Global catchment modelling using World-Wide HYPE (WWH), open data, andstepwise parameter estimation Hydrology and Earth System Sciences DOI 10.5194/hess-24-535-2020 11 February 2020 How far can we reach in predicting river flow globally, using integrated catchment modelling and open global data? For the first time, a catchment model was applied world-wide, covering the entire globe with a relatively high resolution. The results show that stepwise calibration provided better performance than traditional modelling of the globe. The study highlights that open data and models are crucial to advance hydrological sciences by sharing knowledge and enabling transparent evaluation. Read more
Mapping the drivers of uncertainty in atmospheric selenium deposition with global sensitivity analysis Atmospheric Chemistry and Physics DOI 10.5194/acp-20-1363-2020 11 February 2020 The amount of the micronutrient selenium in food largely depends on the amount and form of selenium in soil. The atmosphere acts as a source of selenium to soils through deposition, yet little information is available about atmospheric selenium cycling. Therefore, we built the first global atmospheric selenium model. Through sensitivity and uncertainty analysis we determine that selenium can be transported thousands of kilometers and that measurements of selenium emissions should be prioritized. Read more
