923 research outputs found
Economic impacts and analysis methods of extreme precipitation estimates for eastern Colorado
Get PDFAugust 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 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
Get PDFJuly 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
Simulation of the daytime boundary layer evolution in deep mountain valleys
Get PDFDecember, 1981.Bibliography: pages 96-100.Sponsored by the National Science Foundation ATM76-84405.Sponsored by the National Science Foundation ATM80-15309
Diurnal radiance patterns of finite and semi-infinite clouds in observations of cloud fields
Get PDFDecember, 1981.Includes bibliographical references.Sponsored by the National Science Foundation ATM78-27556
Examination of deep stable layers in the intermountain region of the western United States
Get PDFDecember 1986.Also issued as Paul G. Wolyn's thesis (M.S.) -- Colorado State University, 1986.Includes bibliographical references.The definition of a deep stable layer sed in this report is 65% of the lowest 1.5km of the 1200 GMT sounding having a lapse rate of 2.5°Ckm-1 or less. Deep stable layers are associated with one important group of days which can potentially cause poor regional air quality in the intermountain region of the western United States. At Grand Junction, CO, Salt Lake City, UT, Winnemucca, NV, and Boise, ID they cause low daytime convective boundary layer heights and can allow for light winds near the surface even if moderate or strong synoptic scale winds aloft are present. A climatology of deep stable layer days showed that at the four intermountain region stations most of the days with deep stable layers occurred in December and January. Using a strict deep stable layer definition and episode criteria, episodes of three days or longer occurred on the average at least once every two years at Salt Lake City and Winnemucca, and at least once a year at Boise and Grand Junction. An analysis of the mixing volumes for five consecutive Decembers at the four intermountain region stations shows that all the deep stable layer days had low mixing volumes. A deep stable layer episode, which occurred from December 6 to December 23, 1980 at the four intermountain region stations, was examined in-depth to study the life cycle of a deep stable layer episode and to study the importance of different meteorological factors to the initiation, continuation, and termination of the episode. The initiation of the episode is associated with the movement of a warm ridge aloft into the region and is accompanied by a descending region of rapid warming and strong stability. Synoptic-scale warm air advection and subsidence are both important mechanisms for causing the warming aloft. Weak incoming solar radiation resulting in modest surface heating is important to prevent the destruction of the descending stable region. When the region of rapid warming descended to 0.5km-1.5km it formed a capping stable layer. In this part of the episode called the continuation phase, a disturbance was able to weaken the deep stable layer but not terminate it. The longwave radiative effects of fog may be important in this phase of the episode. The termination of the episode is associated with the destruction of the warm ridge aloft and the movement of disturbances into the region. Surface heating may be important for aiding in the termination of the episode. The presence of a thick fog layer can require a stronger disturbance to terminate the episode.Sponsored by the National Science Foundation ATM-8304328
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