Economic impacts and analysis methods of extreme precipitation estimates for eastern Colorado

August 1986.Includes bibliographical references (pages 56-59).Dams are designed to store water and to ensure human safety and as such they must withstand, in their lifetimes, any extreme precipitation event in their drainage basin. Correct estimation of this event is critical because on one hand it must provide an adequate level of safety to not occur, but it must not be any greater than needed since the high costs of dam construction and modifications are directly related to the magnitude of the estimated extreme event. Most frequently the extreme precipitation event is labeled as the Probable Maximum Precipitation, or PMP. National and state concerns over the adequacy of existing dams in the United States as well as increased development of the Front Range led to state dam risk reclassification and federal redefinition of new PMP values issued for Colorado in 1984. The study area included the region from the Continental Divide to the 103rd Meridian. Study of the implementation of PMP values and their potential economic impacts in Colorado reveals that an enormous cost will result in Colorado. Techniques for estimating cost of modifications for spillways were developed. Among 162 high risk dams, the estimated total cost for modification was approximately $184 million. The economic value of this precipitation estimate is$9.45 million per inch change of rainfall in this limited study area. In one elevation region, 7000 to 9000 feet, the costs is approximately $15.76 million per inch change of rainfall. Regional cost analyses revealed the South Platte River Division had the greatest costs. Inherent limitations in the PMP procedure and the cost of spillway modifications have made evaluating other alternatives necessary. Special aspects of estimates for extreme precipitation, such as snowmelt runoff versus extreme precipitation events and climate variations were examined. Four methods for estimating extreme precipitation events were evaluated; the traditional PMP, the paleogeological, the cloud/mesoscale dynamic model, and the statistical approaches. A collection of approaches were recommended for Colorado dam design in three elevation regions: the plains, the foothills, and the mountains.Supported by NOAA under Grant No. NA-85-RAH-05045 through CIRA

Rooftop and ground standard temperatures: a comparison of physical differences

July 2000.Includes bibliographical references (pages 48-49).Accuracy and continuity of surface air temperature measurements are critical for many meteorological activities including short-term weather forecasting, warnings, and climate monitoring. In the United States and worldwide, most air temperature observations have historically been taken at a height of approximately 1.25 to 1.5 meters above the ground over a grass surface. In the last two decades, there has been a rapid expansion of nonfederal weather station networks to support state, regional and community needs. Many of these new weather stations are located on rooftops for reasons of security or convenience. Mixing these rooftop observations indiscriminately with observations from standard screen-height can pose significant issues for weather forecasting and verification, weather and climate analysis and climate applications such as energy demand planning and forecasting by large public utilities. This study establishes the physical mechanisms which cause a rooftop sensor to have a temperature bias relative to a nearby ground sensor. From a surface energy balance perspective, the physical characteristics of a surface are analyzed and related to temperature bias. This study identifies the surfaces and conditions leading to rooftop temperature bias in both maximum and minimum temperatures. These concepts are verified through both surface radiating temperature measurements and air temperature measurements contrasting roof and ground temperatures. Guidelines are then proposed to establish which roofs are unsuitable for temperature measurements and under what conditions a rooftop is vulnerable to temperature bias. Results indicate that overcast skies lead to small rooftop to ground differences in both surface radiating temperature and air temperature. Observations show differences of approximately 1 degree C or less in radiating temperature and less than 1 degree C in air temperature. An exception was observed where a wall effect led to more than a 2 degree C difference in air temperatures between roof and ground. Clear or partly cloudy skies allow larger rooftop temperature biases to develop. Roof to ground differences in surface radiating temperatures of up to 30 degrees C were observed. Although air temperature measurements were not made at all locations, observations show roof to ground differences of 3 degrees C for radiating temperature differences of 14 degrees C. The potential for even greater roof-ground air temperature differences exists at sites where radiating temperatures are further apart.Supported by the NOAA, National Weather Service, Office of Meteorology under grant NA67RJ0 152 Amend 21

Colorado precipitation event and variability analysis

July 1986.Bibliography: pages 101-102

Colorado monthly temperature and precipitation summary for period 1951-1970

March, 1977

Colorado climate summary water-year series: October 1993-September 1994

December 1994.Annual

Simulation of the daytime boundary layer evolution in deep mountain valleys

December, 1981.Bibliography: pages 96-100.Sponsored by the National Science Foundation ATM76-84405.Sponsored by the National Science Foundation ATM80-15309

Colorado climate summary water-year series: October 1989-September 1990

January 1991.Annual

Diurnal radiance patterns of finite and semi-infinite clouds in observations of cloud fields

December, 1981.Includes bibliographical references.Sponsored by the National Science Foundation ATM78-27556

Colorado climate summary water-year series: January 1977-September 1977, October 1977-September 1978

December 1978.Annual

Inference of stratospheric temperature and water-vapor structure from limb radiance profiles

February 1972.Includes bibliographical references