Laboratory evidence of organic peroxide and peroxyhemiacetal formation in the aqueous phase and implications for aqueous OH Atmospheric Chemistry and Physics DOI 10.5194/acp-15-12867-2015 19 November 2015 This paper demonstrates organic peroxide and peroxyhemiacetal formation during aqueous photooxidation of methylglyoxal using ultra-high-resolution Fourier transform ion cyclotron resonance electrospray ionization mass spectrometry (FTICR-MS). Then, we provide simulation results of organic peroxide/peroxyhemiacetal formation in clouds and wet aerosols and discuss organic peroxides as a source of condensed-phase OH radicals and as a contributor to aqueous secondary organic aerosol (SOA). Read more
Ice water content vertical profiles of high-level clouds: classification and impact on radiative fluxes Atmospheric Chemistry and Physics DOI 10.5194/acp-15-12327-2015 9 November 2015 We discuss the shape of ice water content (IWC) vertical profiles in high ice clouds and its effect on radiative properties of these clouds, both in short- and in long-wave bands (SW and LW). We suggest a set of primitive shapes (rectangular, isosceles trapezoid, lower and upper triangle) and propose a statistical parameterization using ice water path (IWP) as a single parameter. We estimate and explain simulated differences in LW/SW atmospheric radiances for suggested IWC shapes. Read more
Reducing uncertainties in projections of Antarctic ice mass loss The Cryosphere DOI 10.5194/tc-9-2043-2015 9 November 2015 Projections of Antarctic dynamics and contribution to sea-level rise are evaluated in the light of intercomparison exercises dedicated to evaluate models’ ability of representing coastal changes. Uncertainties in projections can be substantially decreased if a selection of models is made and models that are unqualified for the representation of coastal dynamics are excluded. Read more
Modelling Mediterranean agro-ecosystems by including agricultural trees in the LPJmL model Geoscientific Model Development DOI 10.5194/gmd-8-3545-2015 5 November 2015 This study presents the inclusion of 10 Mediterranean agricultural plants in an agro-ecosystem model (LPJmL): nut trees, date palms, citrus trees, orchards, olive trees, grapes, cotton, potatoes, vegetables and fodder grasses. The model was successfully tested in three model outputs: agricultural yields, irrigation requirements and soil carbon density. With this development presented, LPJmL is now able to simulate in good detail and mechanistically the functioning of Mediterranean agriculture. Read more
Expanding the validity of the ensemble Kalman filter without the intrinsic need for inflation Nonlinear Processes in Geophysics DOI 10.5194/npg-22-645-2015 3 November 2015 The popular data assimilation technique known as the ensemble Kalman filter (EnKF) suffers from sampling errors due to the limited size of the ensemble. This deficiency is usually cured by inflating the sampled error covariances and by using localization. This paper further develops and discusses the finite-size EnKF, or EnKF-N, a variant of the EnKF that does not require inflation. It expands the use of the EnKF-N to a wider range of dynamical regimes. Read more
Local- and regional-scale measurements of CH4, δ13CH4, and C2H6 in the Uintah Basin using a mobile stable isotope analyzer Atmospheric Measurement Techniques DOI 10.5194/amt-8-4539-2015 30 October 2015 We describe an innovative instrument based on cavity ring-down spectroscopy that analyzes the stable isotopes of methane in the ambient atmosphere. This instrument was used to study atmospheric emissions from oil and gas extraction activities in the Uintah Basin in Utah. These measurements suggest that 85 ± 7% of the total emissions in the basin are from natural gas production. The easy field deployment of this instrument can enable similar regional attribution studies across the world. Read more
Regional analysis of groundwater droughts using hydrograph classification Hydrology and Earth System Sciences DOI 10.5194/hess-19-4327-2015 28 October 2015 To improve the design of drought monitoring networks and water resource management during episodes of drought, there is a need for a better understanding of spatial variations in the response of aquifers to major meteorological droughts. This paper is the first to describe a suite of methods to quantify such variations. Using an analysis of groundwater level data for a case study from the UK, the influence of catchment characteristics on the varied response of groundwater to droughts is explored. Read more
The importance of Asia as a source of black carbon to the European Arctic during springtime 2013 Atmospheric Chemistry and Physics DOI 10.5194/acp-15-11537-2015 20 October 2015 We show that during the springtime of 2013, the anthropogenic pollution particularly from sources in Asia, contributed significantly to black carbon across the European Arctic free troposphere. In contrast to previous studies, the contribution from open wildfires was minimal. Given that Asian pollution is likely to continue to rise over the coming years, it is likely that the radiative forcing in the Arctic will also continue to increase. Read more
Earthquakes and depleted gas reservoirs: which comes first? Natural Hazards and Earth System Sciences DOI 10.5194/nhess-15-2201-2015 7 October 2015 While the debate is on the possibility that the 2012 Emilia quakes could have been triggered by human activity, we studied the inverse relationship between hydrocarbon and seismicity. Overlapping a data set of gas and oil wells with a database of seismic sources, we found that only 1/19 wells falling on the largest faults is currently productive, while the highest ratio of productive wells is found outside the seismogenic sources. In general, productive gas wells are anti-correlated with faults. Read more
ECCO version 4: an integrated framework for non-linear inverse modeling and global ocean state estimation Geoscientific Model Development DOI 10.5194/gmd-8-3071-2015 6 October 2015 The ECCO v4 non-linear inverse modeling framework and its reference solution are made publicly available. The inverse estimate of ocean physics and atmospheric forcing yields a dynamically consistent and global state estimate without unidentified sources of heat and salt that closely fits in situ and satellite data. Any user can reproduce it accurately. Parametric and external model uncertainties are of comparable magnitudes and generally exceed structural model uncertainties. Read more
Recent highlights from Cluster, the first 3-D magnetospheric mission Annales Geophysicae DOI 10.5194/angeo-33-1221-2015 2 October 2015 This paper presents recent highlights from the Cluster mission on solar wind turbulence, magnetopause asymmetries and magnetosheath density enhancements, dipolarisation currents, reconnection variability, FTE in greatest detail, plasmaspheric wind and re-filling of the plasmasphere, radiation belts, updates of magnetospheric electric and magnetic field models, and magnetosheath and magnetopause properties under low Mach number. Public access to all high-resolution data (CSA) is also presented. Read more
Evaluating the climate and air quality impacts of short-lived pollutants Atmospheric Chemistry and Physics DOI 10.5194/acp-15-10529-2015 24 September 2015 This paper presents a summary of the findings of the ECLIPSE EU project. The project has investigated the climate and air quality impacts of short-lived climate pollutants (especially methane, ozone, aerosols) and has designed a global mitigation strategy that maximizes co-benefits between air quality and climate policy. Transient climate model simulations allowed quantifying the impacts on temperature (e.g., reduction in global warming by 0.22K for the decade 2041-2050) and precipitation. Read more
POM.gpu-v1.0: a GPU-based Princeton Ocean Model Geoscientific Model Development DOI 10.5194/gmd-8-2815-2015 9 September 2015 Graphics processing units (GPUs) are an attractive solution in many scientific applications due to their high performance. However, most existing GPU conversions of climate models use GPUs for only a few computationally intensive regions. In the present study, we redesign the mpiPOM (a parallel version of the Princeton Ocean Model) with GPUs. We show that the performance of the new model on a workstation containing four GPUs is comparable to that on a powerful cluster with 408 standard CPU cores, and it reduces the energy consumption by a factor of 6.8. Read more
Impact of climate and land cover changes on tropospheric ozone air quality and public health in East Asia between 1980 and 2010 Atmospheric Chemistry and Physics DOI 10.5194/acp-15-10093-2015 9 September 2015 Historical land cover and land use change alone between 1980 and 2010 could lead to reduced summertime surface ozone by up to 4ppbv in East Asia. Climate change alone could lead to an increase in summertime ozone by 2-10ppbv in most of East Asia. Land cover change could offset part of the climate effect and lead to a previously unknown public health benefit. The sensitivity of surface ozone to land cover change is more dependent on dry deposition than isoprene emission in most of East Asia. Read more
The feasibility of water vapor sounding of the cloudy boundary layer using a differential absorption radar technique Atmospheric Measurement Techniques DOI 10.5194/amt-8-3631-2015 8 September 2015 This paper describes the feasibility of using a differential absorption radar technique for the remote sensing of water vapor within clouds near the Earth surface from a spaceborne platform. The proposed methodology is shown to be theoretically achievable and complimentary to existing water vapor remote sensing methods. Read more
Past changes in the vertical distribution of ozone – Part 3: Analysis and interpretation of trends Atmospheric Chemistry and Physics DOI 10.5194/acp-15-9965-2015 7 September 2015 Trends in the vertical distribution of ozone are reported for new and recently revised data sets. The amount of ozone-depleting compounds in the stratosphere peaked in the second half of the 1990s. We examine the trends before and after that peak to see if any change in trend is discernible. The previously reported decreases are confirmed. Furthermore, the downward trend in upper stratospheric ozone has not continued. The possible significance of any increase is discussed in detail. Read more
Diesel-related hydrocarbons can dominate gas phase reactive carbon in megacities Atmospheric Chemistry and Physics DOI 10.5194/acp-15-9983-2015 7 September 2015 Technological shifts between fuel sources have had unexpected impacts on atmospheric composition and these significant changes can go undetected if source-specific monitoring infrastructure is not in place. We present chemically comprehensive, continuous measurements of organic compounds in a developed megacity (London), that show diesel-related hydrocarbons can dominate reactive carbon and ozone formation potential, highlighting a serious underestimation of this source in emission inventories. Read more
Retrieving the paleoclimatic signal from the deeper part of the EPICA Dome C ice core The Cryosphere DOI 10.5194/tc-9-1633-2015 20 August 2015 The oldest paleoclimatic information is buried within the lowermost layers of deep ice cores. It is therefore essential to judge how deep these records remain unaltered. We study the bottom 60 meters of the EPICA Dome C ice core from central Antarctica to show that the paleoclimatic signal is only affected at the small scale (decimeters) in terms of some of the global ice properties. However our data suggest that the time scale has been considerably distorted by mechanical stretching. Read more
Observation of a new type of low-frequency waves at comet 67P/Churyumov-Gerasimenko Annales Geophysicae DOI 10.5194/angeo-33-1031-2015 19 August 2015 We present a first report on magnetic field measurements made in the coma of comet 67P/C-G in its low activity state. The plasma environment is dominated by quasi-coherent, large-amplitude, compressional magnetic field oscillations around 40 mHz, differing from the observations at strongly active comets where waves at the cometary ion gyro-frequencies are the main feature. We propose a cross-field current instability associated with the newborn cometary ions as a possible source mechanism. Read more
Century-scale simulations of the response of the West Antarctic Ice Sheet to a warming climate The Cryosphere DOI 10.5194/tc-9-1579-2015 18 August 2015 We used a high resolution ice sheet model capable of resolving grouding line dynamics (BISICLES) to compute responses of the major West Antarctic ice streams to projections of ocean and atmospheric warming. This is computationally demanding, and although other groups have considered parts of West Antarctica, we think this is the first calculation for the whole region at the sub-kilometer resolution that we show is required. Read more