Climatic soil moisture deficit - climate and soil data integration in a GIS

This paper discusses a GIS based implementation of a model for soil droughtiness assessment evaluating the impact of possible climate change. It focuses, in particular, on the development of a methodology for mapping Available Water Capacity. An assessment of the Soil Drought Susceptibility for Scotland in the year 2030 is made and illustrated with maps and derived statistics.     

Winter mortality risk for American ginseng (Panax quinquefolium) in Saskatchewan

North American ginseng is native to the deciduous forest region of eastern North America but is now cultivated in areas well beyond its natural range. In recent years an expanding market has attracted growers in climatically less suitable regions, including the Canadian prairies. The ginseng root requires at least four years to reach marketable size and is sensitive to injury when the temperature drops below about −4°C. Such temperatures are not unusual in the prairies; thus winter kill is a hazard that may limit ginseng production in this region of Canada. This study analyses the risks of winter soil temperatures falling below levels critical for the survival of ginseng in Saskatchewan. It appears that winter conditions may be too severe for reliable production of this lucrative crop, although application of straw mulch and additional benefits of trapped snow could reduce the risk of winter kill.     

Localization in rate-dependent shearing deformation, with application to torsion testing

The localization of plastic deformation in rock is of particular interest in geology in connection with the formation of “ductile” shear zones. It is commonly conjectured that strain softening, as evidenced by a falling stress–strain curve at constant strain rate, is likely to lead to strain localization. Yet observations in torsion tests at constant twist rate fail to show such an effect. However, a more sophisticated analysis using the theory of Fressengeas and Molinari (J. Mech. Phys. Solids 1987, 35, 185–211) for material showing strain-rate dependence of the flow stress does show that, when the boundary conditions are specified in terms of displacements, no localization is predicted in case of strain softening. In contrast, if the boundary conditions are set in terms of forces, localization can be expected for a strain softening material. This prediction needs experimental testing.     

Comparison of theoretical and observed temperature profiles in Devon Island ice cap, Canada

Summary. A non-steady-state theoretical model is used to predict the present variation of temperature with depth in two boreholes in the Devon Island ice cap, Arctic Canada. The boreholes are 300 m apart and one of them reaches bedrock. The heat transfer equation is solved numerically with the record of past temperatures obtained from measurements of the variations of oxygen—isotope ratio with depth in the cores as surface boundary condition. The effects of ice advection, refreezing of meltwater percolating from the surface (the amount of which is recorded in the cores), heating due to firn compaction and ice deformation, and heat flow in the bedrock below the ice sheet are all included in the model. The free parameters are geothermal heat flux, present surface temperature and heat loss at the surface which depends on the depth of meltwater penetration and other factors. Agreement between observed and predicted temperature—depth profiles is very close. Latent heat released by percolating meltwater is the predominating factor in determining the temperature distribution in the upper half of each borehole. The temperature distribution is insensitive to the value of the factor used to convert oxygen—isotope ratio to temperature.     

Detecting trends that are nonlinear and asymmetric on diurnal and seasonal time scales

Trends in climate time series are often nonlinear and temporally-asymmetric, i.e. the trend is different for different seasons and/or hours of the day. Here a method is developed that allows the nonlinearity and temporal asymmetry of a trend to be investigated simultaneously. First, nonlinear trend components are extracted from a univariate time series, by adapting a nonparametric dimension-reduction method. Then, the nonlinear trend components are substituted into a regression model in which the periodic mean component and the periodic variation in the amplitude of the nonlinear trend are modeled using harmonic functions of the seasonal and diurnal periods. Third, trend patterns in the positive and negative anomalies are investigated, by extending the nonlinear trend model using indicator variables. Fourth, a non-local inferential test is developed to test the statistical significance of the trend patterns. The nonlinear trend model is applied to a simulated time series, as well as to long-term high-resolution temperature records from five Southern Hemisphere sites: Lucas Heights, Sydney Airport, Cape Grim, Macquarie Island and Law Dome. Our method should be generally useful for identifying the effect of both climate-related factors and observation/site-related factors on seasonal and diurnal trends in meteorological data series.     

How well do coupled models replicate ocean energetics relevant to ENSO?

Accurate replication of the processes associated with the energetics of the tropical ocean is necessary if coupled GCMs are to simulate the physics of ENSO correctly, including the transfer of energy from the winds to the ocean thermocline and energy dissipation during the ENSO cycle. Here, we analyze ocean energetics in coupled GCMs in terms of two integral parameters describing net energy loss in the system using the approach recently proposed by Brown and Fedorov (J Clim 23:1563?C1580, 2010a) and Fedorov (J Clim 20:1108?C1117, 2007). These parameters are (1) the efficiency ?? of the conversion of wind power into the buoyancy power that controls the rate of change of the available potential energy (APE) in the ocean and (2) the e-folding rate ?? that characterizes the damping of APE by turbulent diffusion and other processes. Estimating these two parameters for coupled models reveals potential deficiencies (and large differences) in how state-of-the-art coupled GCMs reproduce the ocean energetics as compared to ocean-only models and data assimilating models. The majority of the coupled models we analyzed show a lower efficiency (values of ?? in the range of 10?C50% versus 50?C60% for ocean-only simulations or reanalysis) and a relatively strong energy damping (values of ??^?1 in the range 0.4?C1?years versus 0.9?C1.2?years). These differences in the model energetics appear to reflect differences in the simulated thermal structure of the tropical ocean, the structure of ocean equatorial currents, and deficiencies in the way coupled models simulate ENSO.