A field experiment on modeling the impact of aerosol layers on the variability of solar insolation and meteorological characteristics of the surface layer

Described are the results of a field experiment carried out in 2010 on studying the impact of artificial aerosol formations on the solar insolation intensity and thermal characteristics of the atmospheric surface layer. The composition of the measuring equipment complex is given and the results of the experiment and its theoretical analysis are presented. It is demonstrated that the solar radiation flux decrease results in rather rapid response of the surface air layer manifesting itself in the considerable decrease in temperature and turbulent heat fluxes. The theoretical estimates corroborate the obtained experimental data. The field experiment is the continuation of researches carried out in 2008 and 2009.     

Earthquake readiness in volatile regions: the case of Israel

Natural Hazards - The Jordan Rift Valley is a high-risk low-occurrence zone for earthquakes, with documented incidences within the last millennium causing widespread destruction. This research...     

Strengths and weaknesses of acoustic pipe microphone systems in ephemeral,sandy, gravel-bed rivers

We calibrated an acoustic pipe microphone system to monitor bedload flux in a sandy, gravel-bed ephemeral channel. Ours is a first attempt to test the limit of an acoustic surrogate bedload system in a channel with a high content of sand. Calibrations varied in quality; significant data subsetting was required to achieve R² values >0.75. Several data quality issues had to be addressed: (1) apparent pulses, which occur when a sensor records an impulse from sediment impacting the surrounding substrate rather than directly impacting the sensor, were frequent, especially at higher signal amplifications. (2) The impact sensors were frequently covered by gravel sheets. This prompted the development of a cover detection protocol that rejected part of the impact sensor record when at least one sensor was partially or fully covered. (3) Because of the lack of sensor sensitivity to impacts of sand-sized particles, which was anticipated, and the considerable sand component of bedload in this channel, a grain size-limited bedload flux was estimated. This was accomplished by sampling the bedload captured by slot samplers and evaluating the variation of grain size with increasing flow strength. This considerably improved the results when compared to attempts at estimating the flux of the entire distribution of grain sizes. This calibration is a successful first attempt, though the impact sensors required several site-specific calibration steps. A universal set of equations using impact sensors to estimate bedload transport of fine-gravel with a large content of sand remains elusive. Notwithstanding, our study demonstrates the utility of impact sensor data, producing relatively low root mean square errors that are independent of measurements of flow strength (i.e. discharge). These tools will be particularly useful in settings that would benefit from new methodologies for estimating bedload transport in sand-rich gravel-bed rivers, such as the American desert Southwest.     

The formation and viability of a non-basin water management: The US–Canada case

Despite the much-vaunted advantages of basin-wide management many transboundary water regimes do not conform in practice to the basin-wide scale. This study examines whether a spatial alternative that includes only parts of the basin is indeed viable. To this end the US–Canada case is examined. Two questions are asked: why has a non-basin scale been adopted? And whether this option is indeed viable. The review of the negotiations leading up to the US–Canada 1909 Boundary Treaty, and to the establishment of the International Joint Commission (IJC) to control the boundary water (i.e., only the water that crosses the boundary at the point of crossing), shows that the choice of this scale was an outcome of a deadlock in negotiations at the basin scale. The boundary scale was chosen as it reduced the number of players involved in the decision-making process and, consequently, the political costs of a basin-wide agreement. Inevitably, in the subsequent decades the regime faced challenges due to the discrepancy between its jurisdiction and basins. Perhaps the most severe challenge was posed by the Chicago Diversion that was excluded from the regime jurisdiction. Therefore, the paper focuses on how the boundary scale addressed the Chicago diversion externalities. The discussion of this case suggests that the combination of the flexibility of the regime and its interpretations, the nature of the resource (inter-connected lakes) and the two-way upstream–downstream relations along the borders allowed this challenge to be contained. It seems, thus, that a regime can indeed be set at a different scale than the basin-wide one and still be viable.     

Assessing streamflow sensitivity to variations in glacier mass balance

We examine long-term streamflow and mass balance data from two Alaskan glaciers located in climatically distinct basins: Gulkana Glacier, a continental glacier located in the Alaska Range, and Wolverine Glacier, a maritime glacier located in the Kenai Mountains. Over the 1966–2011 study interval, both glaciers lost mass, primarily as a result of summer warming, and streamflow increased in both basins. We estimate total glacier runoff via summer mass balance and quantify the fraction of runoff related to annual mass imbalances. In both climates, annual (net) mass balance contributes, on average, less than 20 % of total streamflow, substantially less than the fraction related to summer mass loss (>50 %), which occurs even in years of glacier growth. The streamflow fraction related to changes in annual balance increased significantly only in the continental environment. In the maritime climate, where deep winter snowpacks and frequent rain events drive consistently high runoff, the magnitude of this streamflow fraction was small and highly variable, precluding detection of any existing trend. Furthermore, our findings suggest that glacier mass change is likely to impact total basin water yield, timing of runoff and water quality in the continental environment. However, the impacts of maritime glacier change appear more likely to be limited to water quality and runoff timing.