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Occurrence of lower cloud albedo in ship tracks

The concept of geoengineering by marine cloud brightening is based on seeding marine stratocumulus clouds with sub-micrometer sea-salt particles to enhance the cloud droplet number concentration and cloud albedo, thereby producing a climate cooling effect. The efficacy of this as a strategy for global cooling rests on the extent to which aerosol-perturbed marine clouds will respond with increased albedo. It is found that the sign (increase or decrease) and magnitude of the albedo response in ship tracks depends on the mesoscale cloud structure, the free tropospheric humidity, and cloud top height.

Improving the active involvement of stakeholders and the public in flood risk management – tools of an involvement strategy and case study results from Austria, Germany and Italy

Natural Hazards and Earth System Sciences
DOI 10.5194/nhess-12-2785-2012
11 September 2012

This paper presents basic elements and the application of two innovative approaches as a part of an “involvement strategy” that aims at the active involvement of all interested parties (stakeholders) for assessing, reviewing and updating flood risk management plans, as formulated in the EU Flood Risk Management Directive 2007/60/EC.

The carbon budget of terrestrial ecosystems in East Asia over the last two decades

Biogeosciences
DOI 10.5194/bg-9-3571-2012
7 September 2012

We estimate the current terrestrial carbon balance of East Asia and its driving mechanisms during 1990–2009 using three different approaches: inventories combined with satellite greenness measurements, terrestrial ecosystem carbon cycle models and atmospheric inversion models.

The “step feature” of suprathermal ion distributions: a discriminator between acceleration processes?

With this study, we draw the attention to the so-called “step feature” of the velocity distributions of suprathermal particles in the solar wind and offer a criterion that allows one to distinguish between those scenarios that employ velocity diffusion, i.e. second-order Fermi processes, which are prime candidates in the present debate.

Water resources trends in Middle East and North Africa towards 2050

Changes in water resources availability can be expected as consequences of climate change, population growth, economic development and environmental considerations. A two-stage modeling approach is used to explore the impact of these changes in the Middle East and North Africa region.

Tree height integrated into pantropical forest biomass estimates

Aboveground tropical tree biomass and carbon storage estimates commonly ignore tree height (H). We estimate the effect of incorporating H on tropics-wide forest biomass estimates in 327 plots across four continents using 42 656 H and diameter measurements and harvested trees from 20 sites to answer various questions.

A synthesis of carbon in international trade

In a globalised world, the transfer of carbon between regions, either physically or embodied in production, represents a substantial fraction of global carbon emissions. The resulting emission transfers are important for balancing regional carbon budgets and for understanding the drivers of emissions.

The scientific basis for a satellite mission to retrieve CCN concentrations and their impacts on convective clouds

The cloud-mediated aerosol radiative forcing is widely recognized as the main source of uncertainty in our knowledge of the anthropogenic forcing on climate. Here, we present a new conceptual framework to help us overcome the challenges for improving our understanding, using relatively simple passive satellite measurements in the visible and infared (IR).

Summer ammonia measurements in a densely populated Mediterranean city

Real-time measurements of ambient concentrations of gas-phase ammonia (NH₃) were performed in Barcelona (NE Spain) in summer between May and September 2011. Two measurement sites were selected: one in an urban background traffic-influenced area (UB) and the other in the historical city centre (CC).

Value of medium range weather forecasts in the improvement of seasonal hydrologic prediction skill

We investigated the contribution of medium range weather forecasts with lead times of up to 14 days to seasonal hydrologic prediction skill over the conterminous United States (CONUS).

Photoproduction of ammonium in the southeastern Beaufort Sea and its biogeochemical implications

During the August 2009 Mackenzie Light and Carbon (MALINA) Program, the absorbed photon-based efficiency spectra of NH₄⁺photoproduction (i.e. photoammonification) were determined using water samples from the SE Beaufort Sea, including the Mackenzie River estuary, shelf, and Canada Basin.

Assessing climate model software quality: a defect density analysis of three models

We found that the climate models all have very low defect densities compared to well-known, similarly sized open-source projects. We discuss the implications of our findings for the assessment of climate model software trustworthiness.

Effects of business-as-usual anthropogenic emissions on air quality

The atmospheric chemistry general circulation model EMAC has been used to estimate the impact of anthropogenic emission changes on global and regional air quality in recent and future years (2005, 2010, 2025 and 2050). The emission scenario assumes that population and economic growth largely determine energy and food consumption and consequent pollution sources with the current technologies (“business as usual”).

Aerosol information content analysis of multi-angle high spectral resolution measurements and its benefit for high accuracy greenhouse gas retrievals

In this paper, we investigate the combined aerosol and greenhouse gas retrieval using multiple satellite viewing angles simultaneously. We find that this method greatly enhances the ability to retrieve aerosol properties by 2–3 degrees of freedom.

Statistical adaptation of ALADIN RCM outputs over the French Alps – application to future climate and snow cover

In this study, snowpack scenarios are modelled across the French Alps using dynamically downscaled variables from the ALADIN Regional Climate Model (RCM) for the control period (1961–1990) and three emission scenarios (SRES B1, A1B and A2) for the mid- and late 21st century (2021–2050 and 2071–2100).

Climatic and geologic controls on suspended sediment flux in the Sutlej River Valley, western Himalaya

Here, we present a comprehensive analysis of the spatiotemporal trends in suspended sediment flux based on daily data during the past decade (2001–2009) from four sites along the Sutlej River and from four of its main tributaries.

Enhancing flood resilience through improved risk communications

Natural Hazards and Earth System Sciences
DOI 10.5194/nhess-12-2271-2012
20 July 2012

A framework of guiding recommendations for effective pre-flood and flood warning communications derived from the URFlood project (2nd ERA-Net CRUE Research Funding Initiative) from extensive quantitative and qualitative research in Finland, Ireland, Italy and Scotland is presented.

Risk perception – issues for flood management in Europe

Natural Hazards and Earth System Sciences
DOI 10.5194/nhess-12-2299-2012
20 July 2012

Public perception of flood risk and flood risk information is often overlooked when developing flood risk management plans. As scientists and the public at large perceive risk in very different ways, flood risk management strategies are known to have failed in the past due to this disconnect between authorities and the public. This paper uses a novel approach in exploring the role of public perception in developing flood risk communication strategies in Europe.

Detecting anthropogenic carbon dioxide uptake and ocean acidification in the North Atlantic Ocean

Fossil fuel use, cement manufacture and land-use changes are the primary sources of anthropogenic carbon dioxide (CO₂) to the atmosphere, with the ocean absorbing approximately 30% (Sabine et al., 2004). Ocean uptake and chemical equilibration of anthropogenic CO₂ with seawater results in a gradual reduction in seawater pH and saturation states (Ω) for calcium carbonate (CaCO₃) minerals in a process termed ocean acidification.

Comparison of OH concentration measurements by DOAS and LIF during SAPHIR chamber experiments at high OH reactivity and low NO concentration

During recent field campaigns, hydroxyl radical (OH) concentrations that were measured by laser-induced fluorescence (LIF) were up to a factor of ten larger than predicted by current chemical models for conditions of high OH reactivity and low NO concentration. These discrepancies, which were observed in forests and urban-influenced rural environments, are so far not entirely understood.

Searching for the seafloor signature of the 21 May 2003 Boumerdès earthquake offshore central Algeria

Natural Hazards and Earth System Sciences
DOI 10.5194/nhess-12-2159-2012
10 July 2012

Shaking by moderate to large earthquakes in the Mediterranean Sea has proved in the past to potentially trigger catastrophic sediment collapse and flow. On 21 May 2003, a magnitude 6.8 earthquake located near Boumerdès (central Algerian coast) triggered large turbidity currents responsible for 29 submarine cable breaks at the foot of the continental slope over ~150 km from west to east.

Extrapolating glacier mass balance to the mountain-range scale: the European Alps 1900–2100

This study addresses the extrapolation of in-situ glacier mass balance measurements to the mountain-range scale and aims at deriving time series of area-averaged mass balance and ice volume change for all glaciers in the European Alps for the period 1900–2100.

Bioerosion by euendoliths decreases in phosphate-enriched skeletons of living corals

While the role of microboring organisms, or euendoliths, is relatively well known in dead coral skeletons, their function in live corals remains poorly understood. They are suggested to behave like ectosymbionts or parasites, impacting their host’s health. However, the species composition of microboring communities, their abundance and dynamics in live corals under various environmental conditions have never been explored.

Building an 18 000-year-long paleo-earthquake record from detailed deep-sea turbidite characterisation in Poverty Bay, New Zealand

Natural Hazards and Earth System Sciences
DOI 10.5194/nhess-12-2077-2012
27 June 2012

Our results show that the progressive characterisation of a turbidite record from a single sedimentary system can provide a continuous paleo-earthquake history in regions of short historical record and incomplete onland paleo-earthquake evidences. The systematic description of each turbidite enables us to infer the triggering mechanism.

Novel water source for endolithic life in the hyperarid core of the Atacama Desert

Our results explain how life has colonized and adapted to one of the most extreme environments on our planet, expanding the water activity envelope for life on Earth, and broadening the spectrum of possible habitats for life beyond our planet.

Severe wind gust thresholds for Meteoalarm derived from uniform return periods in ECA&D

Natural Hazards and Earth System Sciences
DOI 10.5194/nhess-12-1969-2012
25 June 2012

In this study we present an alternative wind gust warning guideline for Meteoalarm, the severe weather warning website for Europe. There are unrealistically large differences in levels and issuing frequencies of all warning levels currently in use between neighbouring Meteoalarm countries. This study provides a guide for the Meteoalarm community to review their wind gust warning thresholds.

Introduction to the European Monitoring and Evaluation Programme (EMEP) and observed atmospheric composition change during 1972–2009

European scale harmonized monitoring of atmospheric composition was initiated in the early 1970s, and the activity has generated a comprehensive dataset which allows the evaluation of regional and spatial trends of air pollution during a period of nearly 40 yr.

Impact of heat and drought stress on arable crop production in Belgium

Natural Hazards and Earth System Sciences
DOI 10.5194/nhess-12-1911-2012
18 June 2012

Modelling approaches are needed to accelerate understanding of adverse weather impacts on crop performances and yields. The aim was to elicit biometeorological conditions that affect Belgian arable crop yield, commensurate with the scale of climatic impacts.

Towards a merged satellite and in situ fluorescence ocean chlorophyll product

Understanding the ocean carbon cycle requires a precise assessment of phytoplankton biomass in the oceans. In terms of numbers of observations, satellite data represent the largest available data set. However, as they are limited to surface waters, they have to be merged with in situ observations.

Solar irradiance reduction to counteract radiative forcing from a quadrupling of CO₂: climate responses simulated by four earth system models

In this study we compare the response of four state-of-the-art Earth system models to climate engineering under scenario G1 of two model intercomparison projects: GeoMIP (Geoengineering Model Intercomparison Project) and IMPLICC (EU project “Implications and risks of engineering solar radiation to limit climate change”).

Organic matter dynamics and stable isotope signature as tracers of the sources of suspended sediment

Suspended sediment (SS) and organic matter in rivers can harm brown trout Salmo trutta by affecting the health and fitness of free swimming fish and by causing siltation of the riverbed. The temporal and spatial dynamics of sediment, carbon (C), and nitrogen (N) during the brown trout spawning season in a small river of the Swiss Plateau were assessed and C isotopes as well as the C/N atomic ratio were used to distinguish autochthonous and allochthonous sources of organic matter in SS loads.

The spatial structure of European wind storms as characterized by bivariate extreme-value Copulas

Natural Hazards and Earth System Sciences
DOI 10.5194/nhess-12-1769-2012
29 May 2012

The winds associated with extra-tropical cyclones are amongst the costliest natural perils in Europe. Re/insurance companies typically have insured exposure at multiple locations and hence the losses they incur from any individual storm crucially depend on that storm’s spatial structure. Motivated by this, this study investigates the spatial structure of the most extreme windstorms in Europe.

Drivers of flood risk change in residential areas

Natural Hazards and Earth System Sciences
DOI 10.5194/nhess-12-1641-2012
23 May 2012

The observed increase of direct flood damage over the last decades may be caused by changes in the meteorological drivers of floods, or by changing land-use patterns and socio-economic developments. It is still widely unknown to which extent these factors will contribute to future flood risk changes.

Photo-lability of deep ocean dissolved black carbon

Dissolved black carbon (DBC) is a significant component of the oceanic dissolved organic carbon (DOC) pool. In the current study, the photo-lability of DBC, DOC and coloured dissolved organic matter (CDOM; ultraviolet-visible absorbance) were determined over the course of a 28 day irradiation of North Atlantic Deep Water under a solar simulator.

On the role of ozone in long-term trends in the upper atmosphere-ionosphere system

Recently, Walsh and Oliver (2011) suggested that the long-term cooling of the upper thermosphere (above 200 km) may be due largely to the stratospheric ozone depletion. Here, we show that the role of ozone is very important in the mesosphere and lower thermosphere but not in the upper thermosphere.

Estimating the climate significance of halogen-driven ozone loss in the tropical marine troposphere

We find that the implementation of oceanic halogen sources and chemistry in climate models is an important component of the natural background ozone budget and we suggest that it needs to be considered when estimating both preindustrial ozone baseline levels and long term changes in tropospheric ozone.

The regulation of the air: a hypothesis

Solid Earth
DOI 10.5194/se-3-87-2012
12 March 2012

We propose the hypothesis that natural selection, acting on the specificity or preference for CO₂ over O₂ of the enzyme rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase), has controlled the CO₂:O₂ ratio of the atmosphere since the evolution of photosynthesis and has also sustained the Earth’s greenhouse-set surface temperature.

Global characteristics of the lunar tidal modulation of the equatorial electrojet derived from CHAMP observations

It has been known since many decades that lunar tide has an influence on the strength of the equatorial electrojet (EEJ). There has, however, never been a comprehensive study of the tidal effect on a global scale. Based on the continuous magnetic field measurements by the CHAMP satellite over 10 years it is possible to investigate the various aspects of lunar effects on the EEJ.

Evidence of a possible turning point in solar UV-B over Canada, Europe and Japan

This study examines the long-term variability of UV solar irradiances at 305 nm and 325 nm over selected sites in Canada, Europe and Japan. Site selection was restricted to the availability of the most complete UV spectroradiometric datasets during the period 1990–2011. The analysis includes the long-term variability of total ozone, aerosol optical depth and cloud fraction at the sites studied.

A tsunami wave recorded near a glacier front

Natural Hazards and Earth System Sciences
DOI 10.5194/nhess-12-415-2012
27 February 2012

We observed a tsunami wave near the glacier front in the Temple Fjord (Spitsbergen). Two temperature and pressure recorders were deployed on a wire from the ice approximately 300 m from the glacier front. The measurements allowed us to estimate the wave number of these waves and the Young’s modulus of the ice.

Revisiting “Narrow Bipolar Event” intracloud lightning using the FORTE satellite

The lightning stroke called a “Narrow Bipolar Event”, or NBE, is an intracloud discharge responsible for significant charge redistribution. The NBE occurs within 10–20 μs, and some associated process emits irregular bursts of intense radio noise, fading at shorter timescales, sporadically during the charge transfer.

Tomography of the 2011 Iwaki earthquake (M 7.0) and Fukushima nuclear power plant area

Solid Earth
DOI 10.5194/se-3-43-2012
14 February 2012

High-resolution tomographic images of the crust and upper mantle in and around the area of the 2011 Iwaki earthquake (M 7.0) and the Fukushima nuclear power plant are determined by inverting a large number of high-quality arrival times with both the finite-frequency and ray tomography methods. The similar structures under the Iwaki source area and the Fukushima nuclear power plant suggest that the security of the nuclear power plant site should be strengthened to withstand potential large earthquakes in the future.

Magnetopause displacements: the possible role of dust

Large compressions of the magnetopause are proposed to occasionally result from temporary encounters of the magnetosphere with dust streams in interplanetary space. Such streams may have their origin in cometary dust tails or asteroids which cross the inner heliosphere or in meteoroids in Earth’s vicinity.