Arctic aerosol and Arctic climate: Results from an energy budget model

An energy budget model is used to study the effect on Arctic climate of optically active aerosol in the Arctic atmosphere. The dependence of the change in surface temperature on the vertical distribution of the aerosol and on the radiative properties of the aerosol-free atmosphere, the Arctic surface, and the aerosol, itself, are calculated. An extensive sensitivity analysis is performed to assess the degree to which the results of the model are dependent upon the assumptions underlying it.List of Symbols Used I ₀ Solar flux at the top of the Arctic Atmosphere (Arctic here means 70° N latitude to the pole) - a _S Surface albedo of the Arctic (a _S ^c is the value of surface albedo at which the sign of the surface temperature perturbation changes) - Reflection coefficient of the aerosol-free Arctic atmosphere - Absorption coefficient of the aerosol-free Arctic atmosphere - Transmission coefficient of the aerosol-free Arctic atmosphere - RI ₀ Total flux of sunlight reflected from the Arctic - A _A I ₀ Total flux of sunlight absorbed in the Arctic atmosphere - A _S I ₀ Total flux of sunlight absorbed at the Arctic surface - A _aer I ₀ Total flux of sunlight absorbed in the Arctic aerosol - Q _A Net atmospheric flow of energy, per unit of Arctic surface area, north across 70° N latitude - Q _S Net oceanic flow of energy, per unit of Arctic surface area, north across 70° N latitude - E Convective plus latent heat fluxes from surface to atmosphere - F _A Net flow of energy to the Arctic atmosphere - F _S Net flow of energy to the Arctic surface - T _A An effective temperature of the Arctic atmosphere - T _S Surface temperature of the Arctic - w Single-scattering albedo of the aerosol - t Optical depth of the aerosol - g Fraction of incident radiation scattered forward by the aerosol - Reflection coefficient of the aerosol - Absorption coefficient of the aerosol - Transmission coefficient of the aerosol - p,q Number of atmospheric layers and the inverse of the fraction of incident IR absorbed in each layer in the energy budget model - F,G,H Measures of the amount of IR-active atmosphere above the surface, the aerosol, and the clouds     

Isotopic evidence of Holocene climatic change in the San Juan Mountains, Colorado

The δD of cellulose from ¹⁴C-dated wood, collected in the San Juan Mountains of southwestern Colorado, decreased by about 45‰ from 9600 to 3100 yr B.P. and an additional 25‰ to the present. The wood samples are from trees that grew above present-day tree line and reflect a time of warmer average summer temperatures. These changes in δD are interpreted to indicate a major change during the Holocene in the sources of moisture, in the seasonality of precipitation, or in both.     

Proposed method for groundwater vulnerability mapping in carbonate (karstic) aquifers: the COP method

The ‘COP method’ has been developed for the assessment of intrinsic vulnerability of carbonate aquifers in the frame of the European COST Action 620. This method uses the properties of overlying layers above the water table (O factor), the concentration of flow (C factor) and precipitation (P factor) over the aquifer, as the parameters to assess the intrinsic vulnerability of groundwater. This method considers karst characteristics, such as the presence of swallow holes (C factor) and their catchment areas as well as karstic landforms, as factors which decrease the natural protection provided by overlying layers (O factor). The P factor allows for consideration of the spatial and temporal variability of precipitation, which is considered the transport agent of contamination. Two carbonate aquifers in the South of Spain, Sierra de Líbar (a conduit flow system) and Torremolinos (a diffuse flow system), have been selected for the application and validation of the method and the results have been compared with three methods widely applied in different aquifers around the world (AVI, GOD and DRASTIC). Comparisons with these methods and validation tools (hydrogeological data and tracer test) show the advantages of the COP method in the assessment of vulnerability of karstic groundwaters.     

Spatial variability of soil quality in the surroundings of a saline lake environment

The spatial variability of the quality of the soil on the shores of a lagoon affected by hydromorphy and/or salinity can be identified (Laguna de Villacañas, Castilla La Mancha) by the use of multitemporal Landsat images in order to analyse these changes. For this purpose, TM and ETM images along with field observations and certain edaphic laboratory parameters are used. In order to identify saline-hydromorphic soils, the spatial variability of chemical and physical properties of a transect, which includes from Solonchaks to Regosols and Cambisols, have been correlated with the Normalised Difference Vegetation Index (NDVI). This index, chosen for specific dates, has proven to be very useful in detecting halophytic vegetation and relating it to the variability of the quality of these soils.     

Texture development and elastic stresses in magnesiowűstite at high pressure

Cubic magnesiowűstite has been deformed in a diamond anvil cell at room temperature. We present results for (Mg_0.4Fe_0.6)O, (Mg_0.25Fe_0.75)O, and (Mg_0.1Fe_0.9)O up to 37, 16, and 18 GPa, respectively. The diffraction images, obtained with the radial diffraction technique, are analyzed using both single peak intensities and a Rietveld method. For all samples, we observe a [100] fiber texture but the texture strength decreases with increasing iron content. This texture pattern is consistent with {110}〈1-10〉 slip. The images were also analyzed for stress, elastic strains, and elastic anisotropy. In general, the stress measured in magnesiowűstite samples is lower than previously measured on MgO. The elastic anisotropy deduced from the X-ray measurements shows a broad agreement with models based on measurements with other techniques.