Geology topics

Gregory J. McCabe

Publications and source records attributed to Gregory J. McCabe.

81 records · Page 5Linked to original sources

USGS1999

Evaluating the use of “goodness‐of‐fit” measures in hydrologic and hydroclimatic model validation

Correlation and correlation‐based measures (e.g., the coefficient of determination) have been widely used to evaluate the “goodness‐of‐fit” of hydrologic and hydroclimatic models. These measures are oversensitive to extreme values (outliers) and are insensitive to additive and proportional differences between model predictions and observations. Because of these limitations, correlation‐based measures can indicate that a model is a good predictor, even when it is not. In this paper, useful alternative goodness‐of‐fit or relative error measures (including the coefficient of efficiency and the index of agreement) that overcome many of the limitations of correlation‐based measures are discussed. Modifications to these statistics to aid in interpretation are presented. It is concluded that correlation and correlation‐based measures should not be used to assess the goodness‐of‐fit of a hydrologic or hydroclimatic model and that additional evaluation measures (such as summary statistics and absolute error measures) should supplement model evaluation tools.

Water Resources Research↗

USGS1999

A Possible connection between the 1878 yellow fever epidemic in the southern United States and the 1877-78 El Niño episode

One of the most severe outbreaks of yellow fever, a viral disease transmitted by the Aedes aegypti mosquito, affected the southern United States in the summer of 1878. The economic and human toll was enormous, and the city of Memphis, Tennessee, was one of the most affected. The authors suggest that as a consequence of one of the strongest El Niño episodes on record—that which occurred in 1877-78—exceptional climate anomalies occurred in the United States (as well as in many other parts of the world), which may have been partly responsible for the widespread nature and severity of the 1878 yellow fever outbreak. This study documents some of the extreme climate anomalies that were recorded in 1877 and 1878 in parts of the eastern United States, with particular emphasis on highlighting the evolution of these anomalies, as they might have contributed to the epidemic. Other years with major outbreaks of yellow fever in the eighteenth and nineteenth centuries also occurred during the course of El Niño episodes, a fact that appears not to have been noted before in the literature.

Bulletin of the American Meteorological Society↗

USGS1999

Explaining spatial variability in mean annual runoff in the conterminous United States

The hydrologic concepts needed in a water-balance model to estimate the spatial variation in mean annual runoff for the 344 climate divisions in the conterminous United States (U.S.) were determined. The concepts that were evaluated were the climatic supply of water (precipitation), climatic demand for water (potential evapotranspiration), seasonality in supply and demand, and soil-moisture-storage capacity. Most (91%) of the spatial variability in mean annual runoff for the climate divisions in the conterminous U.S. was explained by the spatial variability of mean annual precipitation minus mean annual potential evapotranspiration. When soil-moisture-storage capacity and seasonality in supply and demand were added to the water balance, the explained variance in mean annual runoff increased slightly, and the error in estimated mean annual runoff decreased significantly. Adding soil-moisture-storage capacity and seasonality in supply and demand provided the most improvement in areas where seasonal supply and demand are out of phase.

conterminous United States↗

USGS1994

Sensitivity of water resources in the Delaware River basin to climate variability and change

Because of the greenhouse effect, projected increases in atmospheric carbon dioxide levels might cause global warming, which in turn could result in changes in precipitation patterns and evapotranspiration and in increases in sea level. This report describes the greenhouse effect; discusses the problems and uncertainties associated with the detection, prediction, and effects of climate change; and presents the results of sensitivity analyses of how climate change might affect water resources in the Delaware River basin. Sensitivity analyses suggest that potentially serious shortfalls of certain water resources in the basin could result if some scenarios for climate change come true . The results of model simulations of the basin streamflow demonstrate the difficulty in distinguishing the effects that climate change versus natural climate variability have on streamflow and water supply . The future direction of basin changes in most water resources, furthermore, cannot be precisely determined because of uncertainty in current projections of regional temperature and precipitation . This large uncertainty indicates that, for resource planning, information defining the sensitivities of water resources to a range of climate change is most relevant . The sensitivity analyses could be useful in developing contingency plans for evaluating and responding to changes, should they occur.

Water Supply Paper↗

USGS1994

Atmospheric circulation and snowpack in the Gunnison River Basin

Winter mean 700-millibar height anomalies over the eastern North Pacific Ocean and the western United States are related to variability in snowpack accumulations measured on or about April 1 in the Gunnison River Basin in Colorado. Higher-than-average snowpack accumulations are associated with negative 700-millibar height anomalies (anomalous cyclonic circulation) over the western United States and over most of the eastern North Pacific Ocean. The anomalous cyclonic circulation enhances the movement of moisture from the eastern North Pacific Ocean into the southwestern United States. Variability in winter mean 700-millibar height anomalies explain over 50 percent of the variability in snowpack accumulations in the Gunnison River Basin. The statistically significant linear relations between 700-millibar height anomalies and snowpack accumulations in the Gunnison River Basin can be used with general-circulation-model simulations of future 700-millibar height anomalies to estimate changes in snowpack accumulations in the Gunnison River Basin for future climatic conditions.

Conference Paper↗

USGS1993

Sensitivity of water resources in the Delaware River basin to climate variability and change

Because of the "greenhouse effect," projected increases in atmospheric carbon dioxide levels might cause global warming, which in turn could result in changes in precipitation patterns and evapotranspiration and in increases in sea level. This report describes the greenhouse effect; discusses the problems and uncertainties associated with the detection, prediction, and effects of climatic change, and presents the results of sensitivity-analysis studies of the potential effects of climate change on water resources in the Delaware River basin. On the basis of sensitivity analyses, potentially serious shortfalls of certain water resources in the basin could result if some climatic-change scenarios become true. The results of basin streamflow-model simulations in this study demonstrate the difficulty in distinguishing effects of climatic change on streamflow and water supply from effects of natural variability in current climate. The future direction of basin changes in most water resources, furthermore, cannot be determined precisely because of uncertainty in current projections of regional temperature and precipitation. This large uncertainty indicates that, for resource planning, information defining the sensitivities of water resources to a range of climate change is most relevant. The sensitivity analyses could be useful in developing contingency plans on how to evaluate and respond to changes, should they occur.

Delaware;New Jersey;Pennsylvania↗

USGS1991

Uncertainty in climate change and drought

A series of projections of climate change were applied to a watershed model of the Delaware River basin to identify sources of uncertainty in predicting effects of climate change on drought in the basin as defined by New York City reservoir contents. The watershed model is a calibrated, monthly time-step water-balance model that incorporates the operation of reservoirs and diversion canals, and accounts for all inflows to and outflows from the basin at several key nodes. The model assesses the effects of projected climate change on reservoir contents by calculating the frequency with which the basin enters drought conditions under a range of climate-change conditions. Two primary sources of uncertainty that affect predictions of drought frequency in the Delaware River basin were considered: (1) uncertainty in the amount of change in mean air temperature and precipitation, and (2) uncertainty in the effects of natural climate variability on future temperature and precipitation. Model results indicate that changes in drought frequency in the Delaware River basin are highly sensitive to changes in mean precipitation; therefore, the uncertainty associated with predictions of future precipitation has a large effect on the prediction of future drought frequency in the basin.

Conference Paper↗

USGS1990

A conceptual weather-type classification procedure for the Philadelphia, Pennsylvania, area

A simple method of weather-type classification, based on a conceptual model of pressure systems that pass through the Philadelphia, Pennsylvania, area, has been developed. The only inputs required for the procedure are daily mean wind direction and cloud cover, which are used to index the relative position of pressure systems and fronts to Philadelphia. Daily mean wind-direction and cloud-cover data recorded at Philadelphia, Pennsylvania, from January 1954 through August 1988 were used to categorize daily weather conditions. The conceptual weather types reflect changes in daily air and dew-point temperatures, and changes in monthly mean temperature and monthly and annual precipitation. The weather-type classification produced by using the conceptual model was similar to a classification produced by using a multivariate statistical classification procedure. Even though the conceptual weather types are derived from a small amount of data, they appear to account for the variability of daily weather patterns sufficiently to describe distinct weather conditions for use in environmental analyses of weather-sensitive processes.

Pennsylvania↗

USGS1990

Simulated effects of climatic change on runoff and drought in the Delaware River Basin

Various projection of climatic change were applied to watershed models of the Delaware River basin. Simulations indicate that a warming could reduce annual runoff by as much as 25 percent if current precipitation patterns continue. Simulations indicate that the largest changes in basin drought are in response to relatively small changes in precipitation. Basin drought was less sensitive to increases in temperature, reservoir capacity, ground-water pumpage during drought, and consumptive water use--in that order of importance. The effects of global warming on basin runoff and drought cannot be determined precisely, as yet, principally because of the unreliability of precipitation projections.

Conference Paper↗