Seedability of Winter Orographic Storms in Utah

The primary objective of this research has been to collect and analyze data from (randomized) seeded and unseeded winter storms over the Wasatch Mountains for the purpose of developing and designing cloud seeding technology. Two field programs were conducted sequentially; the first was done by airborne seeding and the second by seeding from mountaintop generators. Analysis of precipitation estimators based upon radar and/or rawinsonde data and target precipitation show that increased precipitation due to seeding may occur under certain meteorological conditions. Favorable conditions were found when the supercooled water concentration as measured by aircraft icing rates was high. Precipitation in these particular seeded storms was several times the amount estimated from relationships derived from meteorological parameters and unseeded precipitation. Based upon thes

Research on Increased Winter Orographic Precipitation by Cloud Seeding (FY 1979) Development of Cloud Seedability Criteria

This research continues the exploration of improved cloud seeding technology through the use of airborne seeding, cloud physics measurements from a research aircraft and ground based measurements for the purpose of understanding transport and diffusion of seeding material, developing seedability criteria, and documenting in-cloud responses to seeding. Development of precipitation measuring and memory devices was continued with the aim of obtaining a network of gages well suited for measurement of winter snowfall in mountainous regions. Results of the research are highlighted by the development of criteria for seeding winter orographic storms. It was found that the cloud top temperature and vertical motion apparently are the primary factors governing seedability. Indices of vertical motion are also described, so the seedability criteria can be measured readily in operational type projects. It was found that silver iodide released from aircraft upwind of the target area did not diffuse very well by the time the plumes arrived over the target area about an hour later, so that overseeding occurred inside the plumes, and outside the plumes the clouds were underseeded. Precipitation measurements in a target area and other locations as possible controls indicate that correlations of around 0.8 or 0.85 probably could be obtained with suitably placed gages, with the consequence that the duration of an experiment to verify a set of seeding criteria would be reduced by a factor of 3 or 4 compared to what would be required in the absence of controls

Research on Increased Winter Orographic Precipitation by Cloud Seeding (FY 1980)

This research continues the development of new instrumentation relevant to the advancement of cloud seeding technology and the analysis of data collected to better understand cloud seeding potential in winter orographic clouds. Instrumentation development included the state of construction of a NOAA type dual frequency radiometer for the continuous measurement of supercooled liquid water and the completion of an expendable balloon-borne system for measuring vertical profiles of supercooled liquid water. The analysis of data collected on the project was directed primarily at the interpretation of the vertical profiles of supercooled liquid water and vertical motion. Results indicate that sharp vertical gradients of supercooled liquid water often exist in winter orographic clouds. The relationships between measured supercooled liquid water and other variables strongly support previous findings that the precipitation augmentation potential of winter orographic clouds is substantial when the cloud top temperature is -22°C or warmer ad the cross-barrier wind speed (at mountaintop levels) is 8 m s -1 or greater

Program Development Plan for an Operational Cloud Seeding Project in Utah With Evaluation Included

Operation Framework In the arid climate of Southern and Central Utah, there is a continuing need to augment water supplies. While much of the water is needed for summertime use, particularly for irrigation, most of the available water is supplied by winter storms. Therefore, it is for the augmentation of the water stored naturally as snowpack at higher elevations that cloud seeding can make its greatest contribution. Over the past several years, an attempt has been made to augment the snowpack by cloud seeding. Although there is a physical basis for expecting an increase in precipitation from a scientifically managed cloud seeding program, the empirical evidence that such increases have actually resulted is inconclusive. If the desired increases have not been achieved, the most likely explanation is that the empirical data necessary to distinguish seeding opportunities adequately have not been collected and applied. Presently, it is worthwhile to design a cloud seeding program in which plans are made beforehand to obtain appropriate field data for use in the execution and evaluation of the program. Inasmuch as both the clouds available for seeding and the precipitation and storage of water in the form of snowpack are concentrated in the mountains, the area of precipitation augmentation is best confined also to the mountains. Even though the duration of the seeding program may be indefinite, the duration of operation to be evaluated should be defined in advance and carried out as planned. To do otherwise could introduce unwanted bias and doubtful conclusions. Although an improved operational project with an extensive evaluation included in the design costs much more than that of a simple cloud seeding effort, the benefits will undoubtedly justify the expenditure. The reason is twofold. In terms of immediate benefits, the program will improve determination of which clouds or storms are seedable and concentrate the seeding effort where it will be most beneficial. In the long run, a properly planned and executed evaluation will produce results that will enhance the long term stability of the seeding program as a while. Concerning the socio-economic impact of more effective cloud seeding, the benefits of an increased snowpack are likely to far exceed both the cost of benefits of an increased snowpack are likely to far exceed both the cost of the program and any occasional undesirable side effects. However, the disbenefits of the program should not be overlooked. Potential problems include increased flooding during spring runoff, increased avalanche hazard, and increased inconvenience to mountain communities. On the other hand, only artificial increases of precipitation in these occurrences can reasonably be attributed to cloud seeding. Therefore, it is worthwhile to include in the plan sufficient measurements that can be used to deal with such problems on a rational basis. Finally, a public education effort should be included so that information on all aspects of the cloud seeding program and its reason for being are available to the public. Research Framework The research associated with this program should be primarily directed toward achieving a definitive evaluation of seeding effects. To accomplish this goal, the evaluation must be specifically designed to do so. Therefore, there are two requirements placed upon the total program, one is to increase precipitation, the other is to clearly demonstrate that precipitation has indeed been increased. A secondary objective of the research is to develop a knowledge of the actual potential for increased precipitation in the target area. Measurements of relevant parameters over space and time are needed to determine the spatial and temporal variability as well as the frequency of seedable storms. At the same time, the vertical temperature stability at low levels is needed to determine the fraction of time ground seeding generators are effective. In order to increase precipitation efficiently, these measurements are needed anyway. The only extra work needed to improve our knowledge of seeding potential is an analysis of such data as it becomes available. Research to develop improved methods of indentifying seedability, determine what type of seeding material to use, or decide whether it is better to seed by air or ground requires systematic data collection, but the effort needs to be much more concentrated than appropriate for the general clouding seeding operation and evaluation described here. Such research data collection and evaluation are best left to controlled experiments such as are being conducted at Utah State University. The present project should, in contrast, emphasize measurements needed in the application of previous research results and evaluation of what is actually achieved by cloud seeding in an operational mode. The technology employed should not include promising methods or approaches still being studied but not yet tested in confirmatory experiments

Research on Increased Precipitation by Cloud Seeding: Development Phase

Development of several instrumentation systems for measuring atmospheric variables related to winter orogaraphic cloud seeding was undertaken. A heated tipping bucket precipitation gage was modified both for reliable use and accuracy of data. A solid state memory device was also developed at UWRL for this project. A parachute dropsonde for measuring vertical air motion was further developed. In addition, instrumentation was placed on board an aircraft for measuring concentrations of super cooled water, ice nuclei, and ice crystals. Airborne measurements during cloud seeding with silver iodide showed that the plumes of seeding material could be detected over a target area, and that basic factors involved with precipitation could be measured. That is, measurements of vertical motion, concentrations of super cooled water and precipitation size ice crystals along with precipitation on the ground gave a reasonable picture of the gross features of orographic storms. Indications of seeding effects were found only very tentatively. Further study and development are planned in order to better identify seeding effects

Preliminary Study of the Northern Utah Hail Suppression Project

This study represents an examination of the possibilities for evaluating the northern Utah summertime rain-enhancement hail-suppression project. This study i

Evaluation of Southern and Central Utah Cloud Seeding Program

An evaluation of a winter operational-type cloud seeding project in Utah is made by developing meteorological predictors of target precipitation. Twenty-four hour precipitation amounts in seven unseeded years are matched with 12:00 GMT rawinsonde data to form predictor-predictand relationships. Application of the predictors to the first two years of the project indicates that the observed seeded precipitation is about what would be found in the absence of seeding

Invasive Fire Ants Reduce Reproductive Success and Alter the Reproductive Strategies of a Native Vertebrate Insectivore

BACKGROUND: Introduced organisms can alter ecosystems by disrupting natural ecological relationships. For example, red imported fire ants (Solenopsis invicta) have disrupted native arthropod communities throughout much of their introduced range. By competing for many of the same food resources as insectivorous vertebrates, fire ants also have the potential to disrupt vertebrate communities. METHODOLOGY/PRINCIPAL FINDINGS: To explore the effects of fire ants on a native insectivorous vertebrate, we compared the reproductive success and strategies of eastern bluebirds (Sialia sialis) inhabiting territories with different abundances of fire ants. We also created experimental dyads of adjacent territories comprised of one territory with artificially reduced fire ant abundance (treated) and one territory that was unmanipulated (control). We found that more bluebird young fledged from treated territories than from adjacent control territories. Fire ant abundance also explained significant variation in two measures of reproductive success across the study population: number of fledglings and hatching success of second clutches. Furthermore, the likelihood of bluebird parents re-nesting in the same territory was negatively influenced by the abundance of foraging fire ants, and parents nesting in territories with experimentally reduced abundances of fire ants produced male-biased broods relative to pairs in adjacent control territories. CONCLUSIONS/SIGNIFICANCE: Introduced fire ants altered both the reproductive success (number of fledglings, hatching success) and strategies (decision to renest, offspring sex-ratio) of eastern bluebirds. These results illustrate the negative effects that invasive species can have on native biota, including species from taxonomically distant groups