Thesis (M.S. in geology with a major in hydrogeology)--Washington State University, December 2007. / Includes bibliographical references (p. 57-67).

The objective of this study was to ascertain the magnitude and distribution of rainfall over coastal waters of the northwestern United States and to compare values with those at nearby land stations. Precipitation was measured with gauges at Totem, rainfall amounts were assessed from weather reports at lightships off the coast, and precipitation frequencies at lightships and land stations were examined. Results from the three methods were quite consistent; precipitation. on at sea was only about one-third that at coastal land stations. These values are appreciably less than previous estimates of oceanic rainfall in this area, and they support the view that a significant horizontal gradient of precipitation may exist between the coast and open sea. Rainfall typically occurs both at sea and ashore on the same day, but it rains fewer hours at sea. The relative amount of rain at sea varies with the type of atmospheric system, and rainfall at the coast appears to be intensified by frictional processes. Estimates of evaporation minus precipitation are less negative than earlier ones; consideration of their relation to surface salinity leads to distributions that are in good agreement with oceanographic knowledge. The newer values suggest that in this region the heat gain by the atmosphere may be less (but moisture entrainment may be greater) than was thought. / Graduation date: 1973

The WSR-57 weather radar operated by the National Weather Service at Sacramento, California, plus a network of precipitation gages provided data for this comparison of radar reflectivity with precipitation rates. Located in a valley with mountains within range of the radar on three sides, this radar has varying sensitivity for precipitation rates as a result of the terrain effects. Variation in the terrain surrounding the radar has led to a very wide scatter in precipitation rates associated with any particular radar reflectivity. The radar failed to detect precipitation up to 77% of the time over the Coast Range at ranges greater than 100 nm. Linear regression analyses revealed very poor correlation between the raingage indicated precipitation rate and the radar reflectivity. These analyses resulted in values of (R²), the coefficient of determination, ranging from zero as a minimum to only 0.502 as a maximum. Such results are generally much poorer than results obtained by others. The poor correlations and both overestimation and underestimation of rainfall resulted from factors such as range, terrain blocking, windward or leeward exposure, freezing level height, beam height and width, and the distribution of water vapor in the vertical. / Graduation date: 1976

Thesis (M.S.)--Oregon State University, 1985. / Typescript (photocopy). Includes bibliographical references (leaves 121-127). Also available online.

Thesis (M.S.)--University of Delaware, 2007. / Principal faculty advisor: David R. Legates, Dept. of Geography. Includes bibliographical references.

Thesis (Ph. D.)--Ohio State University, 1982. / Includes bibliographical references (leaves 121-124). Available online via OhioLINK's ETD Center

In the beginning of the 2007 crop year, the Federal Crop Insurance Corporation (FCIC) launched the Pasture, Rangeland, Forage Rainfall Index Pilot Program (PRF-RI) for six states. This insurance is an index and not individual insurance. Risk Management Agency officials claim that PRF-RI insurance mitigates the risk because index and forage production move in the same direction. Therefore when the index is low there is the expectation that production will also be low. PRF-RI is a pilot program and ranchers are skeptical as to whether or not it is viable to purchase the insurance. The objective of this research was to determine the economic benefits of rainfall insurance in selected counties in Texas and estimate the probability of indemnities under different types of coverage levels and index intervals. Historical rainfall indices were simulated for all index intervals and a multivariate empirical distribution of rainfall indices were used. The model was run for alternative scenarios on the available coverage levels (90%, 85%, 80%, 75%, 70%) and relevant premium rates. Each scenario resulted in an estimate of the insurance benefits variable probability density function for a particular coverage level. Stochastic Dominance with Respect to a Function (SDRF), Stochastic Efficiency with Respect to a Function (SERF), and StopLight chart were used to rank the benefits of alternative coverage levels. The results indicated that for all regions tested, the best alternative when purchasing PRF-RI was to buy the 90% coverage level. Probabilities of earning net indemnities decreased at lower coverage levels. December-January is a critical time period that should be taken into consideration by the ranchers. The results indicated also that insurance returns depend on the region where the policy is purchased. In southern and eastern parts of Texas net indemnities appeared to be significantly less and have lower probabilities of being positive than in West Texas. Ranchers from West Texas may be able to significantly benefit from the insurance.

In this study, large scale rainfall simulation was used to evaluate runoff generation from canopy and intercanopy areas within an ashe juniper woodland of the Edwards Plateau. One 3 x 12 m site was established beneath the canopy of mature ashe juniper trees and two sites were established in intercanopy areas. At the base of each plot a trench was constructed for capturing and monitoring shallow subsurface flow. Rainfall simulations on the juniper site produced little surface runoff even though rainfall intensity exceeded 145mm/hour on some occasions. A total of 82.6% of the water applied to the juniper dominated site was accounted for as shallow subsurface flow. The dynamic nature of shallow subsurface flow indicate this process is driven chiefly by macropore flow. On the intercanopy site, 12.67% of the water left the site as surface runoff and ≤3% left as shallow subsurface flow. Large root channels and conduits, which were not present on the intercanopy site, within the soil may promote shallow subsurface flow beneath the juniper canopy. This study is the first to document and suggest shallow subsurface flow occurs on Texas rangelands. The results of this experiment indicate shallow subsurface flow is an important mode of runoff generation on the Edwards Plateau.

The thicketization of the semi-arid region of the United States has resulted in a dramatic change allowing invasive woody species to dominate the landscape with an unknown impact to the water budget. This landscape transformation has created a need to study the hydrology of the region and in particular the effects of increased brush on the water cycle. To study the effects of invasive brush on the water budget, a portable abovecanopy rainfall simulator was developed for plot scale hydrologic research. The rainfall simulator was tested at various field locations, including within the Edwards Plateau, to replicate natural rainfall events on typical hillslope-scale plots. The rainfall simulator was used to quantify aspects of the water budget for a 7 m by 14 m research plot on the Edwards Plateau in Texas. Three rainfall simulation dates were selected for detailed hydrologic analysis. Overall, throughfall accounted for 74% of the water applied to the plot, while 26% of applied water was in the form of stemflow. Lateral subsurface flow represented 33% of the water measured leaving the research plot. A notable result of rainfall simulations was extensive lateral subsurface flow and no surface runoff. The rainfall simulator has proven to be a cost-effective and efficient research tool for replicating natural rainfall in arid and semi-arid environments.

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Supervisor: John M. Sharp. Vita. Includes bibliographical references. Also available from UMI.