Time-window-based filtering method for near-surface detection of leakage from geologic carbon sequestration sites

We use process-based modeling techniques to characterize the temporal features of natural biologically controlled surface CO₂ fluxes and the relationships between the assimilation and respiration fluxes. Based on these analyses, we develop a signal-enhancing technique that combines a novel time-window splitting scheme, a simple median filtering, and an appropriate scaling method to detect potential signals of leakage of CO₂ from geologic carbon sequestration sites from within datasets of net near-surface CO₂ flux measurements. The technique can be directly applied to measured data and does not require subjective gap filling or data-smoothing preprocessing. Preliminary application of the new method to flux measurements from a CO₂ shallow-release experiment appears promising for detecting a leakage signal relative to background variability. The leakage index of ±2 was found to span the range of biological variability for various ecosystems as determined by observing CO₂ flux data at various control sites for a number of years.     

Sensing with boots and trousers — qualitative field observations of shallow soil moisture patterns

While soil moisture patterns can be interesting traits to investigate spatio‐temporal heterogeneity of catchments relevant for various physical processes of soil–atmosphere interaction and soil water redistribution, many of the existing methods to capture spatial patterns are time consuming, expensive or need site‐specific calibration. In this study we present a quick and inexpensive supplementary field method for classifying soil wetness in wet environments. The seven wetness classes are based on qualitative indicators, which one can touch, hear or see on the soil surface. To counter critics that such qualitative methods are considerably affected by subjectivity, we performed systematic testing of the method by taking qualitative measurements in the field with 20 non‐expert raters. We then analyzed these in terms of degree of agreement and assessed the results against gravimetric sampling and time domain reflectometry measurements. In 70% of all classifications raters agreed on the wetness class assigned to the marked sampling locations and in 95% they were not off by more than one wetness class. The seven quantitative wetness classes agreed with gravimetric and time domain reflectometry measurements, although intermediate to wet classes showed an overlap of their range whereas the driest classes showed considerable spread. Despite some potential to optimize the method, it has been shown to be a reliable supplement to existing quantitative techniques for assessing soil moisture patterns in wet environments. Copyright © 2012 John Wiley & Sons, Ltd.     

The Equatorial Undercurrent in the central Atlantic and its relation to tropical Atlantic variability

Seasonal to interannual variations of the Equatorial Undercurrent (EUC) in the central Atlantic at 23°W are studied using shipboard observation taken during the period 1999–2011 as well as moored velocity time series covering the period May 2005–June 2011. The seasonal variations are dominated by an annual harmonic of the EUC transport and the EUC core depth (both at maximum during September), and a semiannual harmonic of the EUC core velocity (maximum during April and September). Substantial interannual variability during the period of moored observation included anomalous cold/warm equatorial Atlantic cold tongue events during 2005/2008. The easterly winds in the western equatorial Atlantic during boreal spring that represent the preconditioning of cold/warm events were strong/weak during 2005/2008 and associated with strong/weak boreal summer EUC transport. The anomalous year 2009 was instead associated with weak preconditioning and smallest EUC transport on record from January to July, but during August coldest SST anomalies in the eastern equatorial Atlantic were observed. The interannual variations of the EUC are discussed with respect to recently described variability of the tropical Atlantic Ocean.     

A new mathematical model of asymmetric hydraulic fracture growth

Hydraulic fractures generated by fluid injection in rock formations are often mapped by seismic monitoring. In many cases, the microseismicity is asymmetric relative to the injection well, which has been interpreted by stress gradient along the direction of the hydraulic fracture. We present a mathematical model of asymmetric hydrofracture growth based on relations between the solid‐phase stress and the fracture hydraulics. For single fracture and single injection point, the model has three parameters, hydraulic conductivities of the fracture wings, and normalised stress gradient and predicts the positions of the fracture tips as functions of time. The model is applied to a set of microseismic event locations that occurred during and after an injection process. Two different methods are suggested that make it possible to delineate the fracture tips from the set of microseismic events. This makes it possible to determine the model parameters and to check the agreement between the model prediction and the measured data. The comparison of the measured and modelled growth of fracture wings supports both the assumption of the non‐zero stress gradient and the existence of the post‐injection unilateral growth.     

Climate change impacts on international seaports: knowledge, perceptions, and planning efforts among port administrators

Seaports are located in vulnerable areas to climate change impacts: on coasts susceptible to sea-level rise and storms or at mouths of rivers susceptible to flooding. They serve a vital function within the local, regional, and global economy. Their locations in the heart of sensitive estuarine environments make it an imperative to minimize the impacts of natural hazards. Climate impacts, like a projected SLR of .6?m to 2?m and doubling of Category 4 and 5 hurricanes by 2100, will result in more extreme events at many seaports. To assess the current state of knowledge on this issue, we surveyed port authorities from around the world about how administrators felt climate change might impact their operations, what sea-level change would create operational problems, and how they planned to adapt to new environmental conditions. The planned rapid expansion of ports reported by the survey respondents indicates that adaptation measures should be considered as ports construct new infrastructure that may still be in use at the end of the century. Respondents agreed that the ports community needs to address this issue and most felt relatively uninformed about potential climate impacts. Although most ports felt that SLR would not be an issue at their port this century, sea-level rise was nevertheless an issue of great concern. Our results suggest opportunities for the scientific community to engage with port practitioners to prepare proactively for climate change impacts on this sector.     

JPEG2000 Image Compression on Solar EUV Images

For future solar missions as well as ground-based telescopes, efficient ways to return and process data have become increasingly important. Solar Orbiter, which is the next ESA/NASA mission to explore the Sun and the heliosphere, is a deep-space mission, which implies a limited telemetry rate that makes efficient onboard data compression a necessity to achieve the mission science goals. Missions like the Solar Dynamics Observatory (SDO) and future ground-based telescopes such as the Daniel K. Inouye Solar Telescope, on the other hand, face the challenge of making petabyte-sized solar data archives accessible to the solar community. New image compression standards address these challenges by implementing efficient and flexible compression algorithms that can be tailored to user requirements. We analyse solar images from the Atmospheric Imaging Assembly (AIA) instrument onboard SDO to study the effect of lossy JPEG2000 (from the Joint Photographic Experts Group 2000) image compression at different bitrates. To assess the quality of compressed images, we use the mean structural similarity (MSSIM) index as well as the widely used peak signal-to-noise ratio (PSNR) as metrics and compare the two in the context of solar EUV images. In addition, we perform tests to validate the scientific use of the lossily compressed images by analysing examples of an on-disc and off-limb coronal-loop oscillation time-series observed by AIA/SDO.     

The CLIVAR C20C project: skill of simulating Indian monsoon rainfall on interannual to decadal timescales. Does GHG forcing play a role?

The ability of atmospheric general circulation models (AGCMs), that are forced with observed sea surface temperatures (SSTs), to simulate the Indian monsoon rainfall (IMR) variability on interannual to decadal timescales is analyzed in a multimodel intercomparison. The multimodel ensemble has been performed within the CLIVAR International “Climate of the 20th Century” (C20C) Project. This paper is part of a C20C intercomparison of key climate time series. Whereas on the interannual timescale there is modest skill in reproducing the observed IMR variability, on decadal timescale the skill is much larger. It is shown that the decadal IMR variability is largely forced, most likely by tropical sea surface temperatures (SSTs), but as well by extratropical and especially Atlantic Multidecadal Oscillation (AMO) related SSTs. In particular there has been a decrease from the late 1950s to the 1990s that corresponds to a general warming of tropical SSTs. Using a selection of control integrations from the World Climate Research Programme’s (WCRP’s) Coupled Model Intercomparison Project phase 3 (CMIP3), it is shown that the increase of greenhouse gases (GHG) in the twentieth century has not significantly contributed to the observed decadal IMR variability.     

Mechanical design of the solar telescope GREGOR

The mechanical structure of the GREGOR telescope was installed at the Observatorio del Teide, Tenerife, in 2004. New concepts for mounting and cooling of the 1.5‐meter primary mirror were introduced. GREGOR is an open telescope, therefore the dome is completely open during observations to allow for air flushing through the open, but stiff telescope structure. Backside cooling system of the primary mirror keeps the mirror surface close to ambient temperature to prevent mirror seeing. The large collecting area of the primary mirror results in high energy density at the field stop at the prime focus of the primary which needs to be removed. The optical elements are supported by precision alignment systems and should provide a stable solar image at the optical lab. The coudé train can be evacuated and serves as a natural barrier between the outer environmental conditions and the air‐conditioned optical laboratory with its sensitive scientific instrumentation. The telescope was successfully commissioned and will start its nominal operation during 2013 (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

An economic analysis of potential impacts of climate change in Egypt

Projections of climate impacts on crop yields simulated for different General Circulation Model (GCM) scenarios are used, in a recursively dynamic general equilibrium framework, to account for potential economy-wide impacts of climate change in Egypt. Comparing these impact projections to those obtained under a reference, business-as-usual, scenario assuming some moderate changes in the political, economic or technological spheres, indicates that global warming has potentially negative effects. The analysis is based on a global assessment of potential climate change-induced variations in world commodity production and trade. The Egyptian agricultural sector, and the non-agricultural sector to a lesser extent, are projected to be increasingly less self-sufficient. Specific potential adverse impacts are identified. The simulation results show that high-cost adaptation measures involving major changes in the agricultural system and practices may mitigate these adverse impacts. Stimulating economic development of the rural areas and creating appropriate conditions for effective diffusion and development of technologies — particularly for the agricultural sector — would seem a desirable strategy. Perhaps, more importantly, the simulation results show that the assumption of exogenously determined technological progress may be inappropriate, in which case the potential adverse impacts of a future warming of the global climate are likely to be fewer than is indicated in this study — if prevailing constraints on productivity growth in the major food and feed grains are ‘released’ by endogenous advances in technology.