The utility of regional Chinese seismograms for source and path studies in central Asia

Summary. Broadband seismograms from the National Seismic Network of the People's Republic of China (PRC) have recently become available through a data exchange programme between NOAA and the State Seismological Bureau of the PRC. In this study, regional surface waves recorded at the Urumchi station located about 700 km north of the Tibetan Plateau in the Sinkiang Province are used to study East Kazakh explosions and wave propagation in central Asia. The data consist of broadband (flat to displacement between 0.1 and 10 Hz), photographic records from an SK Kirnos galvanometric system. Simultaneous inversion of Rayleigh wave phase and group velocities for the path from East Kazakh through the Dzhungarian Basin yields a crustal model dominated by the presence of very low velocities and a strong positive velocity gradient above 15 km depth. Velocities below 15 km depth are not significantly different from other continental structures underlain by Palaeozoic or Precambrian basement. Seismic moments were estimated for seven East Kazakh explosions using models of explosion sources with associated tectonic strain release. The largest explosion studied occurred on 1980 September 14 and had an m_b of 6.2 and a seismic moment of 2.7 × 10²³ dyn cm. The observed amplitude spectra of Rayleigh waves are richer in high frequencies than spectra calculated from our models. This could be caused by a path effect involving seismic wave focusing by the Dzhungarian Basin, although source medium effects cannot be ruled out.     

A coastal prediction system as an event response tool: Particle tracking simulation of an anhydrous ammonia spill in Tampa Bay

A coastal prediction system for Tampa Bay, comprised of a numerical circulation model and Lagrangian particle transport model, rapidly produces hindcast/forecast simulations that alert authorities to high impact areas following the introduction of hazardous material into the bay. The effectiveness of the prediction system as an event response tool is evaluated during an anhydrous ammonia spill. A week-long simulation predicts the trajectory of the material due to winds and currents. Physical transport of the model particles alternates from being tidally driven to being driven both by wind action and residual circulation. A forecast simulation showing particle distribution drove field sampling that resulted in the detection of a Pseudo-nitzschia bloom likely initiated from excess ammonium in the bay. An online component of the coastal prediction system is in development to better manage response and mitigation efforts for future hazardous material spills in Tampa Bay.     

Small‐scale variability in surface moisture on a fine‐grained beach: implications for modeling aeolian transport

Small‐scale variations in surface moisture content were measured on a fine‐grained beach using a Delta‐T Theta probe. The resulting data set was used to examine the implications of small‐scale variability for estimating aeolian transport potential. Surface moisture measurements were collected on a 40 cm × 40 cm grid at 10 cm intervals, providing a total of 25 measurements for each grid data set. A total of 44 grid data sets were obtained from a representative set of beach sub‐environments. Measured moisture contents ranged from about 0% (dry) to 25% (saturated), by weight. The moisture content range within a grid data set was found to vary from less than 1% to almost 15%. The magnitude of within‐grid variability varied consistently with the mean moisture content of the grid sets, following an approximately normal distribution. Both very wet and very dry grid data sets exhibited little internal variability in moisture content, while intermediate moisture contents were associated with higher levels of variability. Thus, at intermediate moisture contents it was apparent that some portions of the beach surface could be dry enough to allow aeolian transport (i.e. moisture content is below the critical threshold), while adjacent portions are too wet for transport to occur. To examine the implications of this finding, cumulative distribution functions were calculated to model the relative proportions of beach surface area expected to be above or below specified threshold moisture levels (4%, 7%, and 14%). It was found that the implicit inclusion of small‐scale variability in surface moisture levels typically resulted in changes of less than 1% in the beach area available for transport, suggesting that this parameter can be ignored at larger spatial scales. Copyright © 2009 John Wiley & Sons, Ltd.     

Community collaboration and climate change research in the Canadian Arctic

Research on climate change impacts, vulnerability and adaptation, particularly projects aiming to contribute to practical adaptation initiatives, requires active involvement and collaboration with community members and local, regional and national organizations that use this research for policy-making. Arctic communities are already experiencing and adapting to environmental and socio-cultural changes, and researchers have a practical and ethical responsibility to engage with communities that are the focus of the research. This paper draws on the experiences of researchers working with communities across the Canadian Arctic, together with the expertise of Inuit organizations, Northern research institutes and community partners, to outline key considerations for effectively engaging Arctic communities in collaborative research. These considerations include: initiating early and ongoing communication with communities, and regional and national contacts; involving communities in research design and development; facilitating opportunities for local employment; and disseminating research findings. Examples of each consideration are drawn from climate change research conducted with communities in the Canadian Arctic.     

Coral reef metrics and habitat equivalency analysis

When coral reefs held in United States public trust are injured by incidents such as vessel groundings or oil spills, a natural resource damage assessment (NRDA) process may be conducted to quantify the resource service loss. Coral cover has been used as an indicator metric to represent lost services in habitat equivalency analyses for determination of compensatory restoration. Depending on the injury and habitat, however, lost services may be more comprehensively represented by alternative approaches such as composite metrics which incorporate other coral reef community characteristics, or a resource-scale approach utilizing size-frequency distributions of injured organisms. We describe the evolving state of practice for capturing coral reef ecosystem services within the natural resources damage assessment context, explore applications and limitations of current metrics, and suggest future directions that may increase the likelihood that NRDA metrics more fully address ecosystem services affected by an injury.     

Impact of soil moisture heterogeneity length scale and gradients on daytime coupled land‐cloudy boundary layer interactions

Using a coupled large‐eddy simulation–land surface model framework, the impact of two‐dimensional soil moisture heterogeneity on the cloudy boundary layer under varied free‐atmosphere stabilities is investigated. Specifically, the impacts of soil moisture heterogeneity length scale and heterogeneity in terms of soil moisture gradients on micrometeorological states, surface fluxes, boundary layer characteristics, and cloud development are examined. The results show that mesoscale circulations due to surface heterogeneity in soil moisture play an important role in transferring water vapour within the boundary layer and in regulating cloud distribution at the entrainment zone, which, in turn, provides feedbacks on boundary layer/surface energy budgets. The initial domain‐averaged soil moisture is identical for all homogenous and heterogeneous cases; however, the soil moisture heterogeneity in gradient and length scale between dry and wet regions has a significant impact on the estimates of near‐surface micrometeorological properties and surface fluxes, which further affect the boundary layer states and characteristics. Both liquid water potential temperature and liquid water mixing ratio increase with an increasing soil moisture gradient, whereas the amount of specific humidity decreases. Heterogeneity length scale and free atmosphere stability also amplify these impacts on the boundary layer structure and cloud formation. In a low atmospheric stability condition that potentially allows for a deeper boundary layer and a higher entrainment rate, cloud base height and cloud thickness significantly increase as the soil moisture gradient and length scale increase. Analysis to differentiate the influences of surface heterogeneity type (i.e. length scale vs gradient) shows that in general soil moisture gradient provides a larger impact than heterogeneity length scale, although the heterogeneity length scale is large enough to initiate circulation features responsible for differences in the coupled system between homogeneous and heterogeneous soil moisture cases. Copyright © 2012 John Wiley & Sons, Ltd.