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  • Cambridge University Press  (8)
  • 2000-2004
  • 1995-1999  (8)
  • 1985-1989
  • 1945-1949
  • 1
    Publication Date: 1995-01-01
    Description: Data from a rawinsonde network are used to provide aerological estimates of monthly precipitation minus evaporation (P – E) averaged over the region north of 70° N. Using published climatological estimates of E, area-averaged P is obtained for each month and year as a residual. Using surface temperatures from the rawinsonde network, the fraction of precipitation falling as snow is then estimated. Over the 1974–91 study period, precipitation and snowfall (water equivalent) have annual means of 26.6 and 19.0 cm. respectively. Assuming a representative aged snowpack density of 330 kg m−3 yields a total snow depth of 57.5 cm. The mean annual cycles of both variables display an autumn maximum, but because of the temperature dependency, nearly all precipitation falls as rain during July and August. Composite analyses reveal that increased precipitation for all seasons and increased snowfall for winter and autumn are favored by a “winter-type” circulation pattern, characterized by stronger troughs over the Atlantic and Eurasian sectors of the Arctic, associated with increased cyclonic activity over the Arctic peripheral seas.
    Print ISSN: 0260-3055
    Electronic ISSN: 1727-5644
    Topics: Geography , Geosciences
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  • 2
    Publication Date: 1995-01-01
    Description: Historical and reconstructed snow-cover data show evidence of a gradual increase in snow cover over the continental interior of North America (NA) during much of the 20th century, primarily in response to increasing snowfall. A rapid decrease in Canadian-prairies snow cover after 1970 is not observed over the Great Plains. Analysis of snow-cover-climate relationships revealed systematic increases in the sensitivity of snow cover to Northern Hemisphere (NH) temperatures over the 1940-65 period. This change is mainly due to an increase in snowfall-temperature sensitivity during this period. Seasonal analysis revealed that the observed increase in snow-cover and snowfall temperature sensitivity is primarily a spring phenomenon. A marked increase in the importance of the spring period is observed around 1960, which coincides with a well-documented change in atmospheric circulation over NA. The post-1960 period is characterized by a significant inverse relationship between snow cover and hemispheric air temperature over the Canadian prairies and northern Great Plains regions.
    Print ISSN: 0260-3055
    Electronic ISSN: 1727-5644
    Topics: Geography , Geosciences
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  • 3
    Publication Date: 1995-01-01
    Description: An analysis of snow-cover variability over Northern Hemisphere land masses reveals a continuation of the subnormal coverage that began in the late 1980s (relative to the 1972–present interval). While the 1994 snow year (September 1993–August 1994) exhibited a return to near-normal hemispheric extent, only three months during this period had above-normal coverage. Only 11 of the past 88 months (through October 1994) have been above the norm. Deficits have been most common in spring, over both the Eurasian and North American continents. This is a hemisphere-wide situation; positive correlations are identified between hemispheric and regional snow extents in spring, as well as in fall and winter. A number of significant associations are also recognized between regions during these three seasons; however, it is uncommon to see more than 50% of the variance in one region explained by another. These correlations are most common between adjacent regions, but some are found between regions on different continents. Only in spring are significant positive relationships between non-adjacent regions on the same continent observed.
    Print ISSN: 0260-3055
    Electronic ISSN: 1727-5644
    Topics: Geography , Geosciences
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  • 4
    Publication Date: 1995-01-01
    Description: An analysis of snow-cover variability over Northern Hemisphere land masses reveals a continuation of the subnormal coverage that began in the late 1980s (relative to the 1972–present interval). While the 1994 snow year (September 1993–August 1994) exhibited a return to near-normal hemispheric extent, only three months during this period had above-normal coverage. Only 11 of the past 88 months (through October 1994) have been above the norm. Deficits have been most common in spring, over both the Eurasian and North American continents. This is a hemisphere-wide situation; positive correlations are identified between hemispheric and regional snow extents in spring, as well as in fall and winter. A number of significant associations are also recognized between regions during these three seasons; however, it is uncommon to see more than 50% of the variance in one region explained by another. These correlations are most common between adjacent regions, but some are found between regions on different continents. Only in spring are significant positive relationships between non-adjacent regions on the same continent observed.
    Print ISSN: 0260-3055
    Electronic ISSN: 1727-5644
    Topics: Geography , Geosciences
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  • 5
    Publication Date: 1995-01-01
    Description: Data from a rawinsonde network are used to provide aerological estimates of monthly precipitation minus evaporation (P – E) averaged over the region north of 70° N. Using published climatological estimates of E, area-averaged P is obtained for each month and year as a residual. Using surface temperatures from the rawinsonde network, the fraction of precipitation falling as snow is then estimated. Over the 1974–91 study period, precipitation and snowfall (water equivalent) have annual means of 26.6 and 19.0 cm. respectively. Assuming a representative aged snowpack density of 330 kg m−3 yields a total snow depth of 57.5 cm. The mean annual cycles of both variables display an autumn maximum, but because of the temperature dependency, nearly all precipitation falls as rain during July and August. Composite analyses reveal that increased precipitation for all seasons and increased snowfall for winter and autumn are favored by a “winter-type” circulation pattern, characterized by stronger troughs over the Atlantic and Eurasian sectors of the Arctic, associated with increased cyclonic activity over the Arctic peripheral seas.
    Print ISSN: 0260-3055
    Electronic ISSN: 1727-5644
    Topics: Geography , Geosciences
    Location Call Number Expected Availability
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  • 6
    Publication Date: 1997-01-01
    Description: Accurate information concerning snow cover, and associated impacts of snow on regional surface albedo, needs to be available for empirical studies and for the validation of climate models. Here, a new integrated dataset for Northern Hemisphere lands is discussed, including files of visible and microwave satellite-derived snow estimates and in situ station data. These files will be used to examine snow extent, snow depth and surface albedo over five-day intervals, and have been generated using geographic-information system techniques. Visible and station observations extend from 1972 to present, and microwave estimates from 1979 to present, The 1×1° gridded files permit the strengths and weaknesses of the individual data sources to be identified and quantified. Also included is a hemispheric time series of snow extern derived from the visible satellite file. Of note are the two pronounced regimes of Northern Hemisphere extent during the past several decades. Between 1972 and 1985, 12 month running means of snow extent fluctuated around a mean of 25.9 × 106 km2. An abrupt transition occurred in 1986 and 1987, and since then mean annual extern has been 24.2 × 106 km2. Recent decreases are found from late winter to early summer.
    Print ISSN: 0260-3055
    Electronic ISSN: 1727-5644
    Topics: Geography , Geosciences
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  • 7
    Publication Date: 1997-01-01
    Description: Accurate information concerning snow cover, and associated impacts of snow on regional surface albedo, needs to be available for empirical studies and for the validation of climate models. Here, a new integrated dataset for Northern Hemisphere lands is discussed, including files of visible and microwave satellite-derived snow estimates and in situ station data. These files will be used to examine snow extent, snow depth and surface albedo over five-day intervals, and have been generated using geographic-information system techniques. Visible and station observations extend from 1972 to present, and microwave estimates from 1979 to present, The 1×1° gridded files permit the strengths and weaknesses of the individual data sources to be identified and quantified. Also included is a hemispheric time series of snow extern derived from the visible satellite file. Of note are the two pronounced regimes of Northern Hemisphere extent during the past several decades. Between 1972 and 1985, 12 month running means of snow extent fluctuated around a mean of 25.9 × 10 km2. An abrupt transition occurred in 1986 and 1987, and since then mean annual extern has been 24.2 × 106km2. Recent decreases are found from late winter to early summer.
    Print ISSN: 0260-3055
    Electronic ISSN: 1727-5644
    Topics: Geography , Geosciences
    Location Call Number Expected Availability
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  • 8
    Publication Date: 1995-01-01
    Description: Historical and reconstructed snow-cover data show evidence of a gradual increase in snow cover over the continental interior of North America (NA) during much of the 20th century, primarily in response to increasing snowfall. A rapid decrease in Canadian-prairies snow cover after 1970 is not observed over the Great Plains. Analysis of snow-cover-climate relationships revealed systematic increases in the sensitivity of snow cover to Northern Hemisphere (NH) temperatures over the 1940-65 period. This change is mainly due to an increase in snowfall-temperature sensitivity during this period. Seasonal analysis revealed that the observed increase in snow-cover and snowfall temperature sensitivity is primarily a spring phenomenon. A marked increase in the importance of the spring period is observed around 1960, which coincides with a well-documented change in atmospheric circulation over NA. The post-1960 period is characterized by a significant inverse relationship between snow cover and hemispheric air temperature over the Canadian prairies and northern Great Plains regions.
    Print ISSN: 0260-3055
    Electronic ISSN: 1727-5644
    Topics: Geography , Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
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