Linking hydraulic traits to tropical forest function in a size-structured and trait-driven model (TFS v.1-Hydro) Geoscientific Model Development DOI 10.5194/gmd-9-4227-2016 24 November 2016 We developed a plant hydraulics model for tropical forests based on established plant physiological theory, and parameterized it by conducting a pantropical hydraulic trait survey. We show that a substantial amount of trait diversity can be represented in the model by a reduced set of trait dimensions. The fully parameterized model is able capture tree-level variation in water status and improves simulations of total ecosystem transpiration, showing how to incorporate hydraulic traits in models. Read more
Multi-annual modes in the 20th century temperature variability in reanalyses and CMIP5 models Geoscientific Model Development DOI 10.5194/gmd-9-4097-2016 17 November 2016 This study compares the 20th century multi-annual climate variability modes in reanalysis data sets (ERA-20C and 20CR) and 12 climate model simulations using the randomised multi-channel singular spectrum analysis. The reanalysis data sets are remarkably similar on all timescales, except that the spectral power in ERA-20C is systematically slightly higher than in 20CR. None of the climate models closely reproduce all aspects of the reanalysis spectra, although many aspects are represented well. Read more
Quantifying the loss of processed natural gas within California’s South Coast Air Basin using long-term measurements of ethane and methane Atmospheric Chemistry and Physics DOI 10.5194/acp-16-14091-2016 15 November 2016 This paper investigates the cause of the known underestimate of bottom-up inventories of methane in California’s South Coast Air Basin (SoCAB). We use total column measurements of methane, ethane, carbon monoxide, and other trace gases beginning in the late 1980s to calculate emissions and attribute sources of excess methane to the atmosphere. We conclude that more than half of the excess methane to the SoCAB atmosphere is attributable to processed natural gas. Read more
Refinement of the ice absorption spectrum in the visible using radiance profile measurements in Antarctic snow The Cryosphere DOI 10.5194/tc-10-2655-2016 14 November 2016 The absorption of visible light in ice is very weak but its precise value is unknown. By measuring the profile of light intensity in snow, Warren and Brand (2006) deduced that light is attenuated by a factor 2 per kilometer in pure ice at a wavelength of 400 nm. We replicated their experiment on a large number of samples and found that ice absorption is at least 10 times stronger. The paper explores various potential physical and statistical biases that could impact the experiment. Read more
Accounting for model error in air quality forecasts: an application of 4DEnVar to the assimilation of atmospheric composition using QG-Chem 1.0 Geoscientific Model Development DOI 10.5194/gmd-9-3933-2016 8 November 2016 This paper analyses methods to assimilate chemical measurements in air quality models. We developed a reduced-order atmospheric chemistry model, which was used to compare results from different assimilation algorithms. Using an ensemble variational method (4DEnVar), we exploited the dynamical information provided by hourly measurements of chemical concentrations to diagnose model biases and improve next-day forecasts for several species of interest for air quality. Read more
Brief communication: Impacts of a developing polynya off Commonwealth Bay, East Antarctica, triggered by grounding of iceberg B09B The Cryosphere DOI 10.5194/tc-10-2603-2016 4 November 2016 Here we report new data from in situ oceanographic surveys and high-resolution ocean modelling experiments in the Commonwealth Bay region of East Antarctica, where in 2010 there was a major reconfiguration of the regional icescape due to the collision of the 97 km long iceberg B09B with the Mertz Glacier tongue. Here we compare post-calving observations with high-resolution ocean modelling which suggest that this reconfiguration has led to the development of a new polynya off Commonwealth Bay. Read more
Effects of ocean acidification on pelagic carbon fluxes in a mesocosm experiment Biogeosciences DOI 10.5194/bg-13-6081-2016 4 November 2016 We performed an experiment in the Baltic Sea in order to investigate the consequences of the increasing CO2levels on biological processes in the free water mass. There was more accumulation of organic carbon at high CO2levels. Surprisingly, this was caused by reduced loss processes (respiration and bacterial production) in a high-CO2environment, and not by increased photosynthetic fixation of CO2. Our carbon budget can be used to better disentangle the effects of ocean acidification. Read more
Seasonal evolution of the effective thermal conductivity of the snow and the soil in high Arctic herb tundra at Bylot Island, Canada The Cryosphere DOI 10.5194/tc-10-2573-2016 2 November 2016 The thermal conductivity (TC) of the snow and top soil greatly impacts the permafrost energy budget. We report the first winter-long monitoring of snow and soil TC in the high Arctic. The data and field observations show the formation of a highly insulating basal depth hoar layer overlaid by a more conductive wind slab. Detailed snow physics models developed for alpine snow cannot reproduce observations because they neglect the strong upward vertical water vapor flux prevailing in Arctic snow. Read more
Towards improved and more routine Earth system model evaluation in CMIP Earth System Dynamics DOI 10.5194/esd-7-813-2016 1 November 2016 We argue that the CMIP community has reached a critical juncture at which many baseline aspects of model evaluation need to be performed much more efficiently to enable a systematic and rapid performance assessment of the large number of models participating in CMIP, and we announce our intention to implement such a system for CMIP6. At the same time, continuous scientific research is required to develop innovative metrics and diagnostics that help narrowing the spread in climate projections. Read more
The BErkeley Atmospheric CO2 Observation Network: initial evaluation Atmospheric Chemistry and Physics DOI 10.5194/acp-16-13449-2016 31 October 2016 We describe the design of and first results from the BErkeley Atmospheric CO2 Observation Network, a distributed instrument of 28 CO2 sensors stationed across and around the city of Oakland, California at ~ 2 km intervals. We evaluate the network via 4 performance parameters (cost, reliability, precision, systematic uncertainty) and find this high density technique to be sufficiently cost-effective and rigorous to inform understanding of small-scale urban emissions relevant to climate regulation. Read more
Ice core evidence for a 20th century increase in surface mass balance in coastal Dronning Maud Land, East Antarctica The Cryosphere DOI 10.5194/tc-10-2501-2016 25 October 2016 The reconstruction of past snow accumulation rates is crucial in the context of recent climate change and sea level rise. We measured ~ 250 years of snow accumulation using a 120 m ice core drilled in coastal East Antarctica, where such long records are very scarce. This study is the first to show an increase in snow accumulation, beginning in the 20th and particularly marked in the last 50 years, thereby confirming model predictions of increased snowfall associated with climate change. Read more
Leaf waxes in litter and topsoils along a European transect SOIL DOI 10.5194/soil-2-551-2016 25 October 2016 For this study we systematically investigated the molecular pattern of leaf waxes in litter and topsoils along a European transect to assess their potential for palaeoenvironmental reconstruction. Our results show that leaf wax patterns depend on the type of vegetation. The vegetation signal is not only found in the litter; it can also be preserved to some degree in the topsoil. Read more
Influence of groundwater on distribution of dwarf wedgemussels (Alasmidonta heterodon) in the upper reaches of the Delaware River, northeastern USA Hydrology and Earth System Sciences DOI 10.5194/hess-20-4323-2016 25 October 2016 The remaining populations of the endangered dwarf wedgemussel (DWM) (Alasmidonta heterodon) in the upper Delaware River, northeastern USA, were thought to be located in areas of substantial groundwater discharge to the river. Physical, thermal, and geophysical methods applied at several spatial scales indicate that DWM are located within or directly downstream of areas of substantial groundwater discharge to the river. DWM may depend on groundwater discharge for their survival. Read more
Glacier change and glacial lake outburst flood risk in the Bolivian Andes The Cryosphere DOI 10.5194/tc-10-2399-2016 20 October 2016 This is the first study of recent glacier change for the whole of the Bolivian Cordillera Oriental from 1986 to 2014. These glaciers have shrunk by ~ 43 %, which is a concern for regional water resources. We provide the first quantification of meltwater lake development across the Bolivian Andes as glaciers have receded. These lakes have increased markedly in number and area. We identify 25 lakes as potential outburst flood risks to downstream communities. These lakes require further monitoring. Read more
Optical properties and aging of light-absorbing secondary organic aerosol Atmospheric Chemistry and Physics DOI 10.5194/acp-16-12815-2016 14 October 2016 Light absorbing organic aerosols (BrC) absorb sunlight thereby influencing climate; however, understanding of the link between their optical properties and environmental variables remains limited. Our chamber experiment results suggest that variables including NOxconcentration, RH level, and photolysis time have considerable influence on secondary BrC optical properties. The results contribute to a more accurate characterization of the impacts of aerosols on climate, especially in urban areas. Read more
GMMIP (v1.0) contribution to CMIP6: Global Monsoons Model Inter-comparison Project Geoscientific Model Development DOI 10.5194/gmd-9-3589-2016 10 October 2016 This paper tells why to launch the Global Monsoons Model Inter-comparison Project (GMMIP) and how to achieve its scientific goals on monsoon variability. It addresses the scientific questions to be answered, describes three tiered experiments comprehensively and proposes a basic analysis framework to guide future research. It will help the monsoon research communities to understand the objectives of the GMMIP and the modelling groups involved in the GMMIP conduct the experiments successfully. Read more
Brief communication: Sendai framework for disaster risk reduction – success or warning sign for Paris? Natural Hazards and Earth System Sciences DOI 10.5194/nhess-16-2189-2016 30 September 2016 In March 2015, a new international blueprint for disaster risk reduction (DRR) has been adopted in Sendai, Japan, at the end of the Third UN World Conference on Disaster Risk Reduction (WCDRR, March 14–18, 2015). We review and discuss the agreed commitments and targets, as well as the negotiation leading the Sendai Framework for DRR (SFDRR), and discuss briefly its implication for the later UN-led negotiations on sustainable development goals and climate change. Read more
Screening of cloud microorganisms isolated at the Puy de Dôme (France) station for the production of biosurfactants Atmospheric Chemistry and Physics DOI 10.5194/acp-16-12347-2016 29 September 2016 A total of 480 microorganisms collected from 39 clouds sampled in France were isolated and identified. This unique collection was screened for biosurfactant production by measuring the surface tension. 41 % of the tested strains were active producers.Pseudomonas, the most frequently detected genus in clouds, was the dominant group for the production of biosurfactants. Further, the potential impact of the production of biosurfactants by cloud microorganisms on atmospheric processes is discussed. Read more
First characterization and validation of FORLI-HNO3 vertical profiles retrieved from IASI/Metop Atmospheric Measurement Techniques DOI 10.5194/amt-9-4783-2016 27 September 2016 HNO3 concentrations are obtained from the IASI instrument and the data set is characterized for the first time in terms of vertical profiles, averaging kernels and error profiles. A validation is also conducted through a comparison with ground-based FTIR measurements, with good results. The data set is then used to analyse HNO3 spatial and temporal variability for the year 2011. The latitudinal gradient and the large seasonal variability in polar regions are well represented with IASI data. Read more
Quantifying ice loss in the eastern Himalayas since 1974 using declassified spy satellite imagery The Cryosphere DOI 10.5194/tc-10-2203-2016 23 September 2016 Here we utilize declassified spy satellite imagery to quantify ice volume loss of glaciers in the eastern Himalayas over approximately the last three decades. Clean-ice and debris-covered glaciers show similar magnitudes of ice loss, while calving glaciers are contributing a disproportionately large amount to total ice loss. Results highlight important physical processes affecting the ice mass budget and associated water resources in the Himalayas. Read more