Spatial and temporal variability of urban tree canopy temperature during summer 2010 in Berlin, Germany

Trees form a significant part of the urban vegetation. Their meteorological and climatological effects at all scales in urban environments make them a flexible tool for creating a landscape oriented to the needs of an urban dweller. This study aims at quantifying the spatio-temporal patterns of canopy temperature (T _C) and canopy-to-air temperature difference (?T _C) in relation to meteorological conditions and tree-specific (physiological) and urban site-specific characteristics. We observed T _C and ?T _C of 67 urban trees (18 species) using a high-resolution thermal-infrared (TIR) camera and meteorological measurements in the city of Berlin, Germany. TIR images were recorded at 1-min intervals over a period of 2?months from 1st July to 31st August 2010. The results showed that ?T _C depends on tree species, leaf size and fraction of impervious surfaces. Average canopy temperature was nearly equal to air temperature. Species-specific maximum ?T _C varied between 1.9?±?0.3?K (Populus nigra), 2.9?±?0.3?K (Quercus robur), 3.2?±?0.5?K (Fagus sylvatica), 3.9?±?1.0?K (Platanus acerifolia), 4.6?±?0.2?K (Acer pseudoplatanus), 5.0?±?0.5?K (A. platanoides) and 5.6?±?1.1?K (A. campestre). We analysed ?T _C for a hot and dry period (A) and a warm and wet period (B). The range of species-specific ?T _C at noon was nearly equal, i.e. 4.4?K for period A and 4.2?K for period B. Trees surrounded by high fraction of impervious surfaces showed consistently higher ?T _C. Knowledge of species-specific canopy temperature and the impacts of urban structures are essential in order to optimise the benefits from trees in cities. However, comprehensive evaluation and optimisation should take the full range of climatological effects into account.     

Variations in the oxygen-isotope composition of ancient Lake Superior between 10,600 and 8,800 cal BP

Variations in the oxygen-isotope composition of paleo-water bodies in the Lake Superior Basin provide information about the timing and pathways of glacial meltwater inflow into and within the Lake Superior Basin. Here, the oxygen-isotope compositions of Lake Superior have been determined using ostracodes from four sediment cores from across the Basin (Duluth, Caribou and Ile Parisienne sub-basins, Thunder Bay trough). The δ¹⁸O values indicate that lake water (Lake Minong) at ~10,600–10,400 cal [~9,400–9,250] BP was dominated by glacial meltwater derived from Lake Agassiz and the Laurentide Ice Sheet (LIS). From that time to ~9,000 cal [~8,100] BP, a period associated with formation of thick varves across the Lake Superior Basin, the δ¹⁸O values of Lake Minong decreased even further (−24 to −28‰), symptomatic of an increasing influx of glacial meltwater. Its supply was reduced between ~9,000 and ~8,900 cal [~8,100–8,000] BP, and lake water δ¹⁸O values grew higher by several per mil during this period. Between ~8,900 and ~8,800 cal [~8,000–7,950] BP, there was a return to δ¹⁸O values as low as −29‰ in some parts of the Lake Superior Basin, indicating a renewed influx of glacial meltwater before its final termination at ~8,800–8,700 cal [~7,950–7,900] BP. The sub-basins in the Lake Superior Basin generally displayed very similar patterns of lake water δ¹⁸O values, typical of a well-mixed system. The final stage of glacial meltwater input, however, was largely expressed near its input (Thunder Bay trough) and recognizable in dampened form mainly in the Duluth sub-basin to the west. Water in the easternmost Ile Parisienne sub-basin was enriched in ¹⁸O relative to the rest of the lake, particularly after ~10,000 cal [~8,900] BP, probably because of a strong influence of local precipitation/runoff, and perhaps also enhanced evaporation. By ~9,200 cal [~8,250] BP, lake water δ¹⁸O values in the Ile Parisienne sub-basin were similar to the adjacent Lake Huron Basin, suggesting a strong hydraulic connection between the two water bodies, and common responses to southern Ontario’s shift to warmer and dry climatic conditions after ~9,000 cal [~8,100] BP.     

Nebular shock waves generated by planetesimals passing through Jovian resonances: Possible sites for chondrule formation

Abstract— The primordial asteroid belt contained at least several hundred and possibly as many as 10,000 bodies with diameters of 1000 km or larger. Following the formation of Jupiter, nebular gas drag combined with passage of such bodies through Jovian resonances produced high eccentricities (e = 0.3‐0.5), low inclinations (i < 0.5°), and, therefore, high velocities (3–10 km/s) for “resonant” bodies relative to both nebular gas and non‐resonant planetesimals. These high velocities would have produced shock waves in the nebular gas through two mechanisms. First, bow shocks would be produced by supersonic motion of resonant bodies relative to the nebula. Second, high‐velocity collisions of resonant bodies with non‐resonant bodies would have generated impact vapor plume shocks near the collision sites. Both types of shocks would be sufficient to melt chondrule precursors in the nebula, and both are consistent with isotopic evidence for a time delay of ?1‐1.5 Myr between the formation of CAIs and most chondrules. Here, initial simulations are first reported of impact shock wave generation in the nebula and of the local nebular volumes that would be processed by these shocks as a function of impactor size and relative velocity. Second, the approximate maximum chondrule mass production is estimated for both bow shocks and impact‐generated shocks assuming a simplified planetesimal population and a rate of inward migration into resonances consistent with previous simulations. Based on these initial first‐order calculations, impact‐generated shocks can explain only a small fraction of the minimum likely mass of chondrules in the primordial asteroid belt (?10²⁴‐10²⁵g). However, bow shocks are potentially a more efficient source of chondrule production and can explain up to 10–100 times the estimated minimum chondrule mass.     

The rate of granule ripple movement on Earth and Mars

The rate of movement for 3- and 10-cm-high granule ripples was documented in September of 2006 at Great Sand Dunes National Park and Preserve during a particularly strong wind event. Impact creep induced by saltating sand caused ∼24 granules min⁻¹ to cross each cm of crest length during wind that averaged ∼9 m s⁻¹ (at a height well above 1 m), which is substantially larger than the threshold for saltation of sand. Extension of this documented granule movement rate to Mars suggests that a 25-cm-high granule ripple should require from hundreds to thousands of Earth-years to move 1 cm under present atmospheric conditions.     

The 6dF Galaxy Survey: final redshift release (DR3) and southern large-scale structures

We report the final redshift release of the 6dF Galaxy Survey (6dFGS), a combined redshift and peculiar velocity survey over the southern sky  (| b | > 10°)  . Its 136 304 spectra have yielded 110 256 new extragalactic redshifts and a new catalogue of 125 071 galaxies making near-complete samples with  ( K , H , J , r _F, b _J) ≤ (12.65, 12.95, 13.75, 15.60, 16.75)  . The median redshift of the survey is 0.053. Survey data, including images, spectra, photometry and redshifts, are available through an online data base. We describe changes to the information in the data base since earlier interim data releases. Future releases will include velocity dispersions, distances and peculiar velocities for the brightest early-type galaxies, comprising about 10 per cent of the sample. Here we provide redshift maps of the southern local Universe with   z ≤ 0.1  , showing nearby large-scale structures in hitherto unseen detail. A number of regions known previously to have a paucity of galaxies are confirmed as significantly underdense regions. The URL of the 6dFGS data base is http://www-wfau.roe.ac.uk/6dFGS .     

On the V/Vm test for a recently published list of bright QSO's

When the V/V_m test is appropriately applied to a recently-published list of bright QSO's the result is closely consistent with the local hypothesis of the nature of QSO's. When an appropriate plot of these QSO's is made in a redshift-magnitude diagram there is no evidence of the density of points increasing reciprocally with flux, as it must do according to the cosmological theory. This new data, therefore, confirms the disproof of the cosmological theory given in Cardiff Preprint No. 88.     

A hybrid approach to flow net generation

By following a simple set of rules, a flow net can be manually constructed to obtain a graphical solution to the Laplace equation for simple two‐dimensional (2‐D) flow problems. With the advent of numerical solutions such as the finite difference and finite element methods, it is more common to generate a flow net automatically using the nodal head and flow values output by the computer program. Two methods have been published for automatically generating flow nets from finite element solutions: the stream‐function method and the particle‐tracking method. The stream‐function method works well for many cases, but it does not work for problems with holes in the mesh or internal sources or sinks. The particle‐tracking method works for all cases, but previously published algorithms that utilize this method do not result in the properly sized flow channels. A new approach is presented in this paper that is a hybrid of the stream‐function and particle‐tracking approaches. This method works for all cases and generates the properly sized flow channels. Copyright © 2001 John Wiley & Sons, Ltd.     

Rock Properties and Seismic Attenuation: Neural Network Analysis

—Using laboratory data, the influence of rock parameters on seismic attenuation has been analyzed using artificial neural networks and regression models. The predictive capabilities of the neural networks and multiple linear regresssion were compared. The neural network outperforms the multiple linear regression in predicting attenuation values, given a set of input of rock parameters. The neural network can make complex decision mappings and this capability is exploited to examine the influence of various rock parameters on the overall seismic attenuation. The results indicate that the most influential rock parameter on the overall attenuation is the clay content, closely followed by porosity. Though grain size contribution is of lower importance than clay content and porosity, its value of 16 percent is sufficiently significant to be considered in the modeling and interpretation of attenuation data.     

Identification and explanation of continental differences in the variability of annual runoff

Continental differences in the variability of annual runoff were investigated using an expanded and improved database to that used in previous work. A statistical analysis of the data, divided by continent and Köppen climate type, revealed that continental differences exist in the variability of annual runoff. The variability of annual runoff for temperate Australia, arid southern Africa and possibly temperate southern Africa were noted to be generally higher than that of other continents with data in the same climate type. A statistical analysis of annual precipitation by continent and Köppen climate type revealed that differences in the variability of annual precipitation could account for some but not all the observed differences in the variability of annual runoff. A literature review of potential causes of continental differences in evapotranspiration resulted in the hypothesis that the significantly higher variability of annual runoff in temperate Australia and possibly temperate southern Africa may be due to the distribution of evergreen and deciduous vegetation. The process model Macaque was used to test this hypothesis. The model results indicate that the variability of annual runoff may be between 1 and 99% higher for catchments covered in evergreen vegetation as opposed to deciduous vegetation, depending on mean annual precipitation and the seasonality of precipitation. It is suggested that the observed continental differences in the variability of annual runoff are largely caused by continental differences in the variability of annual precipitation and in temperate regions the distribution of evergreen and deciduous vegetation in conjunction with the distribution of mean annual precipitation and precipitation seasonality.