4,536 research outputs found
SNOWMIP2: An evaluation of forest snow process simulation
Get PDFThe Northern Hemisphere has large areas that are forested and seasonally snow covered. Compared with open areas, forest canopies strongly influence interactions between the atmosphere and snow on the ground by sheltering the snow from wind and solar radiation and by intercepting falling snow, and these influences have important consequences for the meteorology, hydrology and ecology of forests. Many of the land surface models used in meteorological and hydrological forecasting now include representations of canopy snow processes, but these have not been widely tested in comparison with observations. Phase 2 of the Snow Model Intercomparison Project (SnowMIP2) was therefore designed as an intercomparison of surface mass and energy balance simulations for snow in forested areas. Model forcing and calibration data for sites with paired forested and open plots were supplied to modelling groups. Participants in 11 countries contributed outputs from 33 models, and results are published here for sites in Canada, the USA and Switzerland. On average, the models perform fairly well in simulating snow accumulation and ablation, although there is a wide inter-model spread and a tendency to underestimate differences in snow mass between open and forested areas. Most models capture the large differences in surface albedos and temperatures between forest canopies and open snow well. There is, however, a strong tendency for models to underestimate soil temperatures under snow, particularly for forest sites, and this would have large consequences for simulations of runoff and biological processes in the soil
Spatio-temporal influence of tundra snow properties on Ku-band (17.2 GHz) backscatter
Get PDFDuring the 2010/11 boreal winter, a distributed set of backscatter measurements was collected using a ground-based Ku-band (17.2 GHz) scatterometer system at 26 open tundra sites. A standard snow-sampling procedure was completed after each scan to evaluate local variability in snow layering, depth, density and water equivalent (SWE) within the scatterometer field of view. The shallow depths and large basal depth hoar encountered presented an opportunity to evaluate backscatter under a set of previously untested conditions. Strong Ku-band response was found with increasing snow depth and snow water equivalent (SWE). In particular, co-polarized vertical backscatter increased by 0.82 dB for every 1 cm increase in SWE (R2 = 0.62). While the result indicated strong potential for Ku-band retrieval of shallow snow properties, it did not characterize the influence of sub-scan variability. An enhanced snow-sampling procedure was introduced to generate detailed characterizations of stratigraphy within the scatterometer field of view using near-infrared photography along the length of a 5m trench. Changes in snow properties along the trench were used to discuss variations in the collocated backscatter response. A pair of contrasting observation sites was used to highlight uncertainties in backscatter response related to short length scale spatial variability in the observed tundra environment
Alice Rowe Snow Correspondence
Get PDFEntries include brief biographical information, a typed biography, a handwritten letter of presentation to the collection, a handwritten biographical letter detailing the lives of her parents and husband as well as herself, a print publisher advertisement with a book description and illustrations including the Bark Russell in a school of whales with a book order form, and a typed letter of correspondence from the Maine State Library concerning the diary of Snow\u27s father as it appeared in American Neptune magazine and in receipt of Snow\u27s book gift to the Maine Author Collection
Morphological and behavioral adaptations of moose to climate, snow, and forage
Get PDFThis thesis focuses on the behavioural and morphological adaptations of moose to snow and climate: specifically, seasonal migration, habitat choice, and following behaviour, plus the relationships among morphology, climate, snow, and seasonality. I examine intake and availability of winter forage, and perform one of the first large-scale tests of a widely used optimal foraging model by videotaping free-ranging moose making their own choices. The study of seasonal migration and habitat choice showed that the effect of snow differs with variation in snow severity: in locations with large differences in snow depths in a short distance, snow depth is important, but in locations where snow depth is less variable, snow quality emerges as more important. The thesis is one of the first to use a new method to evaluate the importance of snow quality. Testing between competing hypotheses to explain morphology, the importance of snow was further emphasized relative to temperature and latitude. In snowier areas, moose had larger hooves and longer legs than expected from their size and age. Morphology both conformed to, and was in opposition to some of the most well-known ecogeographical rules: in areas with cold winters, moose were heavier (Bergmann’s rule) and had shorter ears (Allen’s rule). There was also some evidence that moose morphology was related to heat stress during summer. The quality of the two main winter forages (birch and willows) differed within and between species. Willows had more available browse, and lower levels of secondary defence compounds than birch, but also less nitrogen and more fibre. These differences in forage quality also emerged in the test of the Spalinger-Hobbs model, as moose preferentially fed on willow, which was also the faster food to ingest. Most importantly, the analysis revealed that the foraging parameters varied within a foraging bout, and thus parameterizing the model from only the first few minutes of a bout would greatly mis-estimate intake. In the face of climate change, my results emphasize the need for research relating behaviour and morphology to environmental conditions. As moose are well adapted to snow and winter conditions, climate change may have negative consequences on southern populations as temperatures will rise, and some ranges may become unsuitable
Polynesia [cartographic material] /
No full textMap of Polynesia, with eastern Australia as Terra Australis, showing the Pacific islands, population, religions, number of missionaries and native assistants.; Imprint on map: London: Published by John Snow, 35 Paternsoter Row.; Prime meridian: Greenwich.; Plate from: A narrative of missionary enterprises in the South Sea Islands / John Williams. London : Published for the author, by J. Snow, 1837.; Also available in an electronic version via the internet at: http://nla.gov.au/nla.map-rm3970
Edgar Snow in China
No full textIn 1928, Edgar Snow (1905-1972) set out to see the world, hoping to make his mark as a travel-adventure writer. Shanghai was to be a mere stopover, but Snow stayed on in China for thirteen more years. The idealistic young Midwesterner became a journalist and ultimately developed close friendships with China's emerging revolutionary leaders. His 1938 classic, Red Star over China , strongly influenced American views of the Chinese Communists and is still in print nearly sixty years later.This biography breaks fresh ground with its unique and extensive use of Snow's diaries of over forty years. These writings convey Snow's private hopes and fears, his moods and motivations. Thomas skillfully links them with Snow's public writings and deeds. By recreating the milieu in which Snow worked in China, Thomas provides a clearer understanding of both the man and his times.Snow came to China devoid of any political agenda or sinological background. He returned home a politically astute China hand and famed journalist-author. His writing had taken on the nature of political action, which resulted in troubled soul-searching that Snow usually confined to his diary. Thomas's portrait of Ed Snow reveals a man caught up in an important historical moment, a man who profoundly influenced, and was influenced by, the events that swirled around him
The author tells the legend of her grandfather, Cyrus Rackliff, who ignored a pr
No full textThe author tells the legend of her grandfather, Cyrus Rackliff, who ignored a premonition and went duck hunting on Green Island, where he shot himself below the knee. Illustrated with Andrew Wyeth painting and the poem Cyrus by Wilbert Snow
The Impact of Climate Change upon the Snowmelt Hydrology of an Upland UK Catchment
Get PDFSnowmelt hydrology is important in the winter flow regime of upland catchments in the UK as it can attenuate the extremes of the river flow hydrograph. The sensitivity of snow accumulation and melt to changes in climate, in particular to increases in temperature, could impact upon the variability of the winter flow regime. The potential impacts of this change are increases in flood risk and decreases in low flows. Hence this project investigated the consequences of projected climatic change upon snowmelt hydrology of the Dacre Beck catchment in the English Lake District. A distributed snowmelt model was created which spatialised temperature and precipitation data across the catchment. The model accumulated snow when the temperature fell below 0°C and applied one of three temperature-index snowmelt equations to melt the accumulated snowpack. The model was driven using stochastic baseline and projected (2050s medium emissions) weather series calculated using the UKCP09 weather generator. The results showed a large future reduction in both winter snow accumulation and the magnitude of snowmelt hydrology. However, the limited hydrological process representation of the model meant it could not reliably forecast changes in the winter flow regime. Therefore the snow accumulation and melt equations were incorporated into the physically based Connectivity Runoff Model (CRUM). This improved model was calibrated to observed discharge data within a Generalised Likelihood Uncertainty Estimation (GLUE) framework before being run with a sample of baseline and projected UKCP09 weather generator series. The results showed that both high and low flows in the winter flow regime were likely to increase which contradicted previous expectations but it was unclear about the role of snowmelt hydrology in these changes. Further investigation using temperature perturbed weather series found that these changes in the winter flow regime were most likely caused by increases in rainfall which overrode the impact of changes in snowmelt hydrology
Determination of snow depth and water equivalent by remote sensing
Get PDFSubmitted to Office of Water Research and Technology, U.S. Department of the Interior.June 1976.This exploratory study was designed to investigate the possibilities of using inexpensive aerial remote sensing methods to measure the snowpack and its water content. The relation of snow depth and elevation on the same aspect (north or south) was definitely linear but the slopes of the regression lines varied between months and between years. Thus no uniform prediction was possible of snow depth over an entire watershed from a single measurement at one point. Example: The regression equation for March 4, 1972 on the north aspect was YSNOW DEPTH(dm)= -24.5 + (1.10 ± 0.51)XELEV(100m). Snow depth and water equivalent were consistently related to melt date, sometimes quite strongly. The addition of vegetation density to the equation significantly increased the proportion of variability of snow depth which is accounted for. Little strength was added by including the other environmental factors, - aspect, elevation, and slope degree. However, elevation was more strongly related to snow depth early in the spring and aspect was more strongly related later. Prediction of water equivalent was improved by including degree of slope early in the season, and by including aspect and then slope later in the season. An example of multiple regression equation with a multiple R of 0.81 is YSNMAR= -14.0 + 0.08XMELTDA+ 0.095XVEGDEN+ 0.004XELEV - 0.021XFROMN- 0.053XSLOPE where subscripts mean SNow depth (dm) in MARch, MELT DAte (year-day), VEGetation DENsity (100-foot candles), ELEVation (meters), azimuth FROM due North less than 180° (degrees), and degree of SLOPE (Percent). Therefore by measuring the melt date and environmental variables one could predict snow depth and water equivalent, once these equations were established for a given area. Melt date can be measured by observation from two aerial flights at three-day intervals in early spring. The relationship between the elevation of the snow-melt line and time was determined to be linear for each of the three years observed. The average slope of the linear regression was 19.64 meters per day (0.82 meters per hour) during the snow melt period. This rate of recedence was consistent during the three-year period of observation. The variation in date over the three-year period for the snow-melt line to be at a given elevation, was approximately equivalent to the time period for the snow-melt line to raise 600 meters. The photogrammetric determination of snow depths over the area was restricted by the limited number of ground control targets. The measurement and computational procedures for the photographic imagery were adequate for the intended purpose. The determination of the location of additional visible ground control in the available photography would permit more definitive results. The point measurement of the elevation of snow fields can be accomplished if there are sufficient shadows due to vegetation or image texture due to dirt or surface irregularities. Our conclusion is that determination of snow depth and water equivalent by remote sensing from aircraft is possible. We have uncovered the basic principles but further work is needed to develop the method.OWRT Project no. A-019-COLO; supported (in part) by funds provided by the United States Department of the Interior, Office of Water Research and Technology, as authorized by the Water Resources Research Act of 1964, and pursuant to Grant Agreement Nos. 14-31-0001-3806, 14-13-0001-4006, and 14-31-0001-5006
Improved Parameterization of Snow Albedo in WRF + Noah: Methodology Based on a Severe Snow Event on the Tibetan Plateau
No full textSnowfall and the subsequent evolution of the snowpack have a large effect on the surface energy balance and water cycle of the Tibetan Plateau (TP). The effects of snow cover can be represented by the WRF coupled with a land surface scheme. The widely used Noah scheme is computationally efficient, but its poor representation of albedo needs considerable improvement. In this study, an improved albedo scheme is developed using a satellite-retrieved albedo that takes snow depth and age into account. Numerical experiments were then conducted to simulate a severe snow event in March 2017. The performance of the coupled WRF/Noah model, which implemented the improved albedo scheme, is compared against the model’s performance using the default Noah albedo scheme and against the coupled WRF/CLM that applied CLM albedo scheme. When the improved albedo scheme is implemented, the albedo overestimation in the southeastern TP is reduced, reducing the RMSE of the air temperature by 0.7°C. The improved albedo scheme also attains the highest correlation between the satellite-derived and the model-estimated albedo, which provides for a realistic representation of both the snow water equivalent (SWE) spatial distribution in the heavy snowbelt (SWE > 6 mm) and the maximum SWE in the eastern TP. The underestimated albedo in the coupled WRF/CLM leads to underestimating the regional maximum SWE and a consequent failure to estimate SWE in the heavy snowbelt accurately. Our study demonstrates the feasibility of improving the Noah albedo scheme and provides a theoretical reference for researchers aiming to improve albedo schemes further.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Optical and Laser Remote Sensin
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