Acid Deposition Long-Term Trends (1986) / Chapter Skim
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3. Uncertainties in Trends in Acid Deposition: The Role of Climatic Fluctuations
3. Uncertainties in Trends in Acid Deposition: The Role of Climatic Fluctuations
Pages 93-108
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From page 93... ...
Considerable attention has focused on the influence of meteorological processes on acid deposition, with particular emphasis on source-receptor relationships to determine the origin and the route of transport of deposited materials (National Research Council 1983)
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From page 94... ...
This chapter focuses not on this aspect but rather on the general synoptic weather conditions that produce precipitation in the eastern United States. Besides summertime convective storms, which are often dispersed spatially, the primary sources of precipitation in the eastern United States are organized frontal system associated with low-pressure centers (cyclones)
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From page 95... ...
Precipitation records for the eastern United States are characterized by fairly large year-to-year variations of precipitation superimposed on long-term trends. In the Adirondack Mountains, for example, precipitation in some years is approximately 50 percent higher than in
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From page 96... ...
Unfortunately, little is known about the extent to which year-to-year variations in the number and size of precipitation events affect total acid deposition, principally because reliable long-term precipitation chemistry data sets are not available. Changes in cloud cover (cloud type and extent)
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From page 97... ...
The occurrence of individual precipitation events with respect to the timing of sample collection may be of considerable importance in comparing historical data sets, particularly of stream-water chemistry. The acid shock phenomenon -- low-pH water at the start of snowmelt-is fairly well known (National Research Council of Canada 1981)
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From page 98... ...
. By adjusting the calculated pH values to take "excess" calcium and magnesium into account, changes in pH between the 1950s and late 1970s appear to be less than reported previously for most of the eastern united States (compare Figures 3.4(b)
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From page 99... ...
September 1980 median pH distribution from National Acid Deposition Program network. See Chapter 5 for a detailed discussion of these data (Stensland and Semonin 1982)
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From page 100... ...
1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 NEW ENGLAND M I DO LE AT LANTI C EAST NORTH CENTRAL WEST NORTH CENTRAL SOUTH ATLANTIC EAST SOUTH CENTRAL FIGURE 3.5 P.I.s (<3) for regions of the eastern United States, 1895-1981 (after Diaz 1983)
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From page 101... ...
has the maximum number of air stagnation cases. An analysis of the number of stagnation cases each year in the eastern United States over the past 50 years reveals an increase
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From page 103... ...
. This does not imply that all parts of the country experienced an increase in stagnation days over the 50 years, but it does mean that the total number of cases within the entire eastern United States has increased.
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From page 104... ...
The changes in mean monthly or seasonal temperature that have been observed are only one isolated measure of climate. It is probable that these temperature changes reflect adjustments in large-scale circulation patterns of the eastern United States involving a multitude of other, more subtle changes in climate, such as length of the growing season, frequency of frosts, growing degree days, type and amount of cloudiness, vapor pressure, net radiation, and wind direction.
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From page 105... ...
\20~ 90t 60 30 pF} o —30 —60 _90 -,20 1921 195S ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ' ~ ~ ~ ~ ~ ~ I ~ l ~ I ~~ ~ ~ ~ ~ ~ ~ ~ · ~ · - ~ ~ - - ~ · - - ~ · - - ~ · - - ~ · - - ~ - - - ~ · - - ~ 95 99 1 7 ~ ~ ,5 t9 23 27 3' 35 ~ 43 47 51 55 ~ 63 67 7t 75 ~ YEA. t189S.1979} FIGURE 3.9 Cumulative departures of long-term mean monthly temperature in the contiguous United States; monthly means compiled from January 1895 to March 1979.
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From page 106... ...
FIGURE 3.10 Mean seasonal and annual temperature differences (OF)
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From page 107... ...
1983. Some aspects of major wet and dry periods in the contiguous United States, 1895-1981.
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From page 108... ...
1982. Another interpretation of the pH trend in the United States.
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