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- Author or Editor: Henry F. Diaz x
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Abstract
Using state monthly values of the Palmer Drought Index from January 1895 through April 1981, thespatial and temporal features of dry and wet episodes over the contiguous United States were analyzed. Thevariance spectrum of the area under both drought and wet spells in the western United States (17 westernmoststates) was also investigated.
The main results are as follows. Consistent with the findings of previous investigators, the interior andwestern portions of the United States are found to be more drought-prone than other parts of the country.By contrast, the likelihood of drought occurrence in states near coastal areas is considerably less. Prolongedmoisture abnormalities also tend to occur over the more drought-prone states indicating a tendency towardbimodality (either too dry or too wet).
The variance spectrum of the area under drought in the western United States exhibits a red-type spectrum,whereas the wet spell area exhibits relatively greater variance at the highest and intermediate frequencies(2 and 3-9 years). In a few regions of the United States, the initiation and termination of drought episodestend to occur more often at certain times of the year. For most regions, however, this preference is onlymarginal or non-existent.
Abstract
Using state monthly values of the Palmer Drought Index from January 1895 through April 1981, thespatial and temporal features of dry and wet episodes over the contiguous United States were analyzed. Thevariance spectrum of the area under both drought and wet spells in the western United States (17 westernmoststates) was also investigated.
The main results are as follows. Consistent with the findings of previous investigators, the interior andwestern portions of the United States are found to be more drought-prone than other parts of the country.By contrast, the likelihood of drought occurrence in states near coastal areas is considerably less. Prolongedmoisture abnormalities also tend to occur over the more drought-prone states indicating a tendency towardbimodality (either too dry or too wet).
The variance spectrum of the area under drought in the western United States exhibits a red-type spectrum,whereas the wet spell area exhibits relatively greater variance at the highest and intermediate frequencies(2 and 3-9 years). In a few regions of the United States, the initiation and termination of drought episodestend to occur more often at certain times of the year. For most regions, however, this preference is onlymarginal or non-existent.
Abstract
The separate contribution of December, January and February temperature to the net seasonal anomaly for the 1975–76 through 1981–82 winter seasons is analyzed. It is found that the January departures contributed by far the most toward making these seven winter seasons well below average in much of the contiguous United States, particularly in the eastern half of the country.
Each of these Januaries averaged from below to much-below the long-term average. By contrast, the Decembers and Februaries ranged from much-below to much-above the long-term mean.
Intraseasonal relationships were explored to see what role monthly persistence may have played during these seven winters. It was found that although there was a general tendency for anomalies to persist in sign from one month to the next, particularly in the eastern third and the far West of the United States, the coldness of the Januaries appears to be the result of an intensified meridional circulation occurring for the most part, during the calendar month of January.
Abstract
The separate contribution of December, January and February temperature to the net seasonal anomaly for the 1975–76 through 1981–82 winter seasons is analyzed. It is found that the January departures contributed by far the most toward making these seven winter seasons well below average in much of the contiguous United States, particularly in the eastern half of the country.
Each of these Januaries averaged from below to much-below the long-term average. By contrast, the Decembers and Februaries ranged from much-below to much-above the long-term mean.
Intraseasonal relationships were explored to see what role monthly persistence may have played during these seven winters. It was found that although there was a general tendency for anomalies to persist in sign from one month to the next, particularly in the eastern third and the far West of the United States, the coldness of the Januaries appears to be the result of an intensified meridional circulation occurring for the most part, during the calendar month of January.
Abstract
The spatial patterns and temporal trends of temperature and precipitation for northern North America (Alaska Canada and western Greenland) have been analyzed. Over approximately the past hundred years, three temperature regimes are identified that correspond roughly to similar climatic regimes identified in separate studies for the contiguous United States. Through 1980, warming is evident only from around the mid-1920s to about the early 1960s. No recent trends are present in winter or fall. Some cooling is evident during summer while spring shows cooling from 1963 to 1976 and warming thereafter.
Spatially, the largest changes occur in areas where variations in the amplitude of the long waves result in large advective differences; these areas are also sensitive to fluctuations in the mean position of the arctic front. Changes from one temperature regime to another occur quite abruptly and last for several years to a few decades.
There are two areas where well-defined precipitation changes coincide with temperature changes: the southern Canadian Plains near the 100°W meridian; and from the Great Lakes to James Bay northeastward toward Labrador. The location of these areas within a principal storm corridor suggests that the changes are associated with southward and northward shifts in the storm track that runs from the upper Midwest/Great Lakes region along the St. Lawrence River Valley toward the North Atlantic.
Abstract
The spatial patterns and temporal trends of temperature and precipitation for northern North America (Alaska Canada and western Greenland) have been analyzed. Over approximately the past hundred years, three temperature regimes are identified that correspond roughly to similar climatic regimes identified in separate studies for the contiguous United States. Through 1980, warming is evident only from around the mid-1920s to about the early 1960s. No recent trends are present in winter or fall. Some cooling is evident during summer while spring shows cooling from 1963 to 1976 and warming thereafter.
Spatially, the largest changes occur in areas where variations in the amplitude of the long waves result in large advective differences; these areas are also sensitive to fluctuations in the mean position of the arctic front. Changes from one temperature regime to another occur quite abruptly and last for several years to a few decades.
There are two areas where well-defined precipitation changes coincide with temperature changes: the southern Canadian Plains near the 100°W meridian; and from the Great Lakes to James Bay northeastward toward Labrador. The location of these areas within a principal storm corridor suggests that the changes are associated with southward and northward shifts in the storm track that runs from the upper Midwest/Great Lakes region along the St. Lawrence River Valley toward the North Atlantic.
Abstract
The relationship between anomalous seasonal surface temperature and precipitation in the contiguous United States and concomitant fluctuations of western Northern Hemisphere 700 mb height as a function of latitude are examined. Findings are consistent with other studies dealing with the spatial patterns of midtropospheric teleconnections and their surface manifestations. A strong inverse relationship between temperature in the eastern United States and heights in the western Northern Hemisphere polar regions is present during winter and spring, especially in winter. In summer the association is positive and is most evident in the southern tier of states. Fewer significant correlations are found between seasonal precipitation and midtropospheric height, with the strongest ones occurring in winter and summer.
It is shown that in winter, during the period 1948–81. the frequency of below-average 700 mb heights has increased in the temperate latitudes of the western Northern Hemisphere. At the same time, a general increase in above normal polar latitude heights has taken place. This in turn has been associated with lower winter temperatures in the eastern United States.
Some suggestions are offered as to the physical-synoptic mechanisms underlying these relationships, although this report is mainly of a fact finding nature. Several data tables and charts are presented for purposes of application to climate studies and long range forecasting.
Abstract
The relationship between anomalous seasonal surface temperature and precipitation in the contiguous United States and concomitant fluctuations of western Northern Hemisphere 700 mb height as a function of latitude are examined. Findings are consistent with other studies dealing with the spatial patterns of midtropospheric teleconnections and their surface manifestations. A strong inverse relationship between temperature in the eastern United States and heights in the western Northern Hemisphere polar regions is present during winter and spring, especially in winter. In summer the association is positive and is most evident in the southern tier of states. Fewer significant correlations are found between seasonal precipitation and midtropospheric height, with the strongest ones occurring in winter and summer.
It is shown that in winter, during the period 1948–81. the frequency of below-average 700 mb heights has increased in the temperate latitudes of the western Northern Hemisphere. At the same time, a general increase in above normal polar latitude heights has taken place. This in turn has been associated with lower winter temperatures in the eastern United States.
Some suggestions are offered as to the physical-synoptic mechanisms underlying these relationships, although this report is mainly of a fact finding nature. Several data tables and charts are presented for purposes of application to climate studies and long range forecasting.
Abstract
Site-specific total electric energy and heating oil consumption for individual residences show a very high correlation with National Weather Service airport temperature data when transformed to heating degree days. Correlations of regional total residential electrical consumption with airport heating degree days for about 40 000 dwelling units in an area of ∼6500 km2 over an 11-year period indicate that temperature is a dominant cause of short-term usage fluctuations. Cost increases since 1973 appear to have only temporarily slowed the growth rate in consumption. A time series of national population-weighted heating degree day totals for the period 1898–1978 provides a scenario of possible variations of weather-related residential energy consumption.
Abstract
Site-specific total electric energy and heating oil consumption for individual residences show a very high correlation with National Weather Service airport temperature data when transformed to heating degree days. Correlations of regional total residential electrical consumption with airport heating degree days for about 40 000 dwelling units in an area of ∼6500 km2 over an 11-year period indicate that temperature is a dominant cause of short-term usage fluctuations. Cost increases since 1973 appear to have only temporarily slowed the growth rate in consumption. A time series of national population-weighted heating degree day totals for the period 1898–1978 provides a scenario of possible variations of weather-related residential energy consumption.
Abstract
The effects on potential heating, cooling and water demand induced by the shift and growth of population from cooler and wetter regions of the country to warmer and drier areas were examined. Heating and cooling degree day totals for each of the 48 contiguous states were weighted by population to obtain national totals using U.S. Census figures starting with the 1930 Census. We also developed categorical measures of population in relation to mean annual precipitation and precipitation variability. The water year October to September was used instead of the calendar year to take into account seasonal factors.
The shift in population from the Northeast and Midwest to the South and Southwest United States has resulted in relatively lower heating but greater cooling demand on a national basis in the 1980s as compared with the results obtained using the 1930 Census.
The increase in population in the arid West has increased the region's sensitivity to precipitation, and hence streamflow fluctuations.
Abstract
The effects on potential heating, cooling and water demand induced by the shift and growth of population from cooler and wetter regions of the country to warmer and drier areas were examined. Heating and cooling degree day totals for each of the 48 contiguous states were weighted by population to obtain national totals using U.S. Census figures starting with the 1930 Census. We also developed categorical measures of population in relation to mean annual precipitation and precipitation variability. The water year October to September was used instead of the calendar year to take into account seasonal factors.
The shift in population from the Northeast and Midwest to the South and Southwest United States has resulted in relatively lower heating but greater cooling demand on a national basis in the 1980s as compared with the results obtained using the 1930 Census.
The increase in population in the arid West has increased the region's sensitivity to precipitation, and hence streamflow fluctuations.
Abstract
Principal component (PC) analysis performed on irregularly spaced data can produce distorted loading patterns. We provide an example to demonstrate some distorted patterns which can result from the direct application of PC analysis (or eigenvector analysis, factor analysis, or asymptotic singular decomposition) on irregularly spaced data. The PCs overestimate loadings in areas of dense data. The problem can be avoided by interpolating the irregularly spaced data to a grid which closely approximates equal-area.
Abstract
Principal component (PC) analysis performed on irregularly spaced data can produce distorted loading patterns. We provide an example to demonstrate some distorted patterns which can result from the direct application of PC analysis (or eigenvector analysis, factor analysis, or asymptotic singular decomposition) on irregularly spaced data. The PCs overestimate loadings in areas of dense data. The problem can be avoided by interpolating the irregularly spaced data to a grid which closely approximates equal-area.
Abstract
The possible effects of climatic fluctuations on renewable water supplies in the western United States was examined, especially as it is impacted by the growth of population and water consumption in recent decades.
Precipitation fluctuations in the Colorado River Basin states have differed depending upon their location, but have tended to fluctuate with a time scale of one to two decades. Longer-term regimes may also be operative. For example, the Upper Basin states (Colorado and Utah) experienced a prolonged wet interval from about the turn of this century to around 1930; from 1930 to around 1978, drier than normal years tended to outnumber wet ones; and since 1978 the Upper Basin has been exceedingly wet. Lower Basin states also experienced the early wet period and drier conditions after the mid-1940s, but they undergo somewhat different alternations of wetness and dryness. However, from the point of view of water supply, precipitation variability in the Upper Basin, particularly in Colorado, is more critical.
Reservoir capacity in the and western states is expected to gain little in additional storage capacity during the next couple of decades; in addition, withdrawal of water from the Colorado River is approaching the legal limits. The effect of a future prolonged drought on the order of those which have occurred in recent decades, or in a worse case, those which have occurred in past centuries from tree ring studies, could have far more serious consequences than any in previous experience due to the large population increases in the region. These population trends show all signs of continuing, at least in the near future. The impact of a drought, however, would depend on the level of reservoir capacity that is present at the time of drought onset as well as its intensity and longevity; reservoirs in the West are presently at or near capacity.
Abstract
The possible effects of climatic fluctuations on renewable water supplies in the western United States was examined, especially as it is impacted by the growth of population and water consumption in recent decades.
Precipitation fluctuations in the Colorado River Basin states have differed depending upon their location, but have tended to fluctuate with a time scale of one to two decades. Longer-term regimes may also be operative. For example, the Upper Basin states (Colorado and Utah) experienced a prolonged wet interval from about the turn of this century to around 1930; from 1930 to around 1978, drier than normal years tended to outnumber wet ones; and since 1978 the Upper Basin has been exceedingly wet. Lower Basin states also experienced the early wet period and drier conditions after the mid-1940s, but they undergo somewhat different alternations of wetness and dryness. However, from the point of view of water supply, precipitation variability in the Upper Basin, particularly in Colorado, is more critical.
Reservoir capacity in the and western states is expected to gain little in additional storage capacity during the next couple of decades; in addition, withdrawal of water from the Colorado River is approaching the legal limits. The effect of a future prolonged drought on the order of those which have occurred in recent decades, or in a worse case, those which have occurred in past centuries from tree ring studies, could have far more serious consequences than any in previous experience due to the large population increases in the region. These population trends show all signs of continuing, at least in the near future. The impact of a drought, however, would depend on the level of reservoir capacity that is present at the time of drought onset as well as its intensity and longevity; reservoirs in the West are presently at or near capacity.
Abstract
The development of serially complete (no missing values) daily maximum–minimum temperatures and total precipitation time series over the western United States is documented. Several estimation techniques based on spatial objective analysis schemes are used to estimate daily values, with the &ldquost” estimate chosen as a missing value replacement. The development of a continuous and complete daily dataset will be useful in a variety of meteorological and hydrological research applications.
The spatial interpolation schemes are evaluated separately by interpolation method and calendar month. Cross validation of the results indicates a distinct seasonality to the efficiency (error) of the estimates, although no systematic bias in the estimation procedures was found. The resulting number of serially complete daily time series for the western United States (all states west of the Mississippi River) includes 2034 maximum–minimum temperature stations and 2962 total daily precipitation locations.
Abstract
The development of serially complete (no missing values) daily maximum–minimum temperatures and total precipitation time series over the western United States is documented. Several estimation techniques based on spatial objective analysis schemes are used to estimate daily values, with the &ldquost” estimate chosen as a missing value replacement. The development of a continuous and complete daily dataset will be useful in a variety of meteorological and hydrological research applications.
The spatial interpolation schemes are evaluated separately by interpolation method and calendar month. Cross validation of the results indicates a distinct seasonality to the efficiency (error) of the estimates, although no systematic bias in the estimation procedures was found. The resulting number of serially complete daily time series for the western United States (all states west of the Mississippi River) includes 2034 maximum–minimum temperature stations and 2962 total daily precipitation locations.
Abstract
One of the major concerns with detecting global climate change is the quality of the data. Climate data are extremely sensitive to errant values and outliers. Prior to analysis of these time series, it is important to remove outliers in a methodical manner.
This study provides statistically derived bounds for the uncertainty associated with surface temperature and precipitation measurements and yields a baseline dataset for validation of climate models as well as for a variety of other climatological uses. A two-step procedure using objective analysis was used to identify outliers. The first step was a temporal check that determines if a particular monthly value is consistent with other monthly values for the same station. The second step utilizes six different spatial interpolation techniques to estimate each monthly time series. Each of the methods is ranked according to its respective correlation coefficients with the actual time series, and the technique with the highest correlation coefficient is chosen as the best estimator. For both temperature and precipitation, a multiple regression scheme was found to be the best estimator for the majority of records. Results from the two steps are merged, and a combined set of quality control flags are generated.
Abstract
One of the major concerns with detecting global climate change is the quality of the data. Climate data are extremely sensitive to errant values and outliers. Prior to analysis of these time series, it is important to remove outliers in a methodical manner.
This study provides statistically derived bounds for the uncertainty associated with surface temperature and precipitation measurements and yields a baseline dataset for validation of climate models as well as for a variety of other climatological uses. A two-step procedure using objective analysis was used to identify outliers. The first step was a temporal check that determines if a particular monthly value is consistent with other monthly values for the same station. The second step utilizes six different spatial interpolation techniques to estimate each monthly time series. Each of the methods is ranked according to its respective correlation coefficients with the actual time series, and the technique with the highest correlation coefficient is chosen as the best estimator. For both temperature and precipitation, a multiple regression scheme was found to be the best estimator for the majority of records. Results from the two steps are merged, and a combined set of quality control flags are generated.
