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• 1. [Article] Precipitation characteristics for landslide hazard assessment for the central Oregon Coast Range

  Precipitation data from 1988-1995 for 13 rain gauges of the Department of Forest Engineering rain gauge network, and a longer precipitation record, 1976-1995, at Mapleton were analyzed. The objectives ...

  Citation × Citation Citation Abstract Copy Title: Precipitation characteristics for landslide hazard assessment for the central Oregon Coast Range Author: Surfleet, Christopher G. Precipitation data from 1988-1995 for 13 rain gauges of the Department of Forest Engineering rain gauge network, and a longer precipitation record, 1976-1995, at Mapleton were analyzed. The objectives were to assess the spatial and temporal distribution of precipitation intensity and antecedent precipitation, and understand the role of these characteristics for triggering debris slides from headwalls in the central Oregon Coast Range. Frequency distribution curves and recurrence intervals using a partial-duration series were calculated for the maximum 5-minute, 30 minute, 1 hour, 2 hour, 6 hour precipitation durations and antecedent precipitation index (API) for the rain gauge network and the maximum 1 hour and 2 hour precipitation durations for Mapleton. Isohyet lines showing selected 2-year precipitation intensities and API were used to characterize the spatial distribution of precipitation intensity and API across the central Oregon Coast Range. The effect of elevation on this spatial distribution was investigated. An attempt to quantify the occurrence of high intensity precipitation occurring with high antecedent precipitation, which is hypothesized to trigger debris slides, was done by testing if the highest precipitation intensities (greater than a 1 -year recurrence interval) occurred during the storms with the highest API. API and precipitation intensity were tested for correlation to discern if a particular precipitation duration could be used to predict API, thus make it possible to use a precipitation intensity based threshold to assess the general hazard of landslides. Precipitation intensities associated with selected recurrence intervals vary considerably over the study area. Precipitation values for selected durations and recurrence intervals could vary as much as 50% or larger for selected rain gauge locations. Precipitation intensities are higher in the central portion of the study area, centered around the ridges of the Siuslaw River watershed, with decreasing intensity toward the northern and southern boundaries possibly due to topographic influences. Higher API values are found more frequent where the high precipitation intensity spatial trends exists. Relationships between short duration precipitation intensities with elevation, and API with elevation, within the rain gauge network could not be determined. No single precipitation intensity, including total storm precipitation, showed a strong positive correlation with high API for the entire rain gauge network. It appears that any attempts to predict the precipitation characteristics which trigger headwall failure by a precipitation intensity threshold in the central Oregon Coast Range is not possible. Attempts to assess the risk of headwall failure by high API may be possible. High precipitation intensities occurred with high antecedent precipitation conditions and they occur at the highest antecedent precipitation conditions. Title: Precipitation characteristics for landslide hazard assessment for the central Oregon Coast Range Author: Surfleet, Christopher G. Precipitation data from 1988-1995 for 13 rain gauges of the Department of Forest Engineering rain gauge network, and a longer precipitation record, 1976-1995, at Mapleton were analyzed. The objectives were to assess the spatial and temporal distribution of precipitation intensity and antecedent precipitation, and understand the role of these characteristics for triggering debris slides from headwalls in the central Oregon Coast Range. Frequency distribution curves and recurrence intervals using a partial-duration series were calculated for the maximum 5-minute, 30 minute, 1 hour, 2 hour, 6 hour precipitation durations and antecedent precipitation index (API) for the rain gauge network and the maximum 1 hour and 2 hour precipitation durations for Mapleton. Isohyet lines showing selected 2-year precipitation intensities and API were used to characterize the spatial distribution of precipitation intensity and API across the central Oregon Coast Range. The effect of elevation on this spatial distribution was investigated. An attempt to quantify the occurrence of high intensity precipitation occurring with high antecedent precipitation, which is hypothesized to trigger debris slides, was done by testing if the highest precipitation intensities (greater than a 1 -year recurrence interval) occurred during the storms with the highest API. API and precipitation intensity were tested for correlation to discern if a particular precipitation duration could be used to predict API, thus make it possible to use a precipitation intensity based threshold to assess the general hazard of landslides. Precipitation intensities associated with selected recurrence intervals vary considerably over the study area. Precipitation values for selected durations and recurrence intervals could vary as much as 50% or larger for selected rain gauge locations. Precipitation intensities are higher in the central portion of the study area, centered around the ridges of the Siuslaw River watershed, with decreasing intensity toward the northern and southern boundaries possibly due to topographic influences. Higher API values are found more frequent where the high precipitation intensity spatial trends exists. Relationships between short duration precipitation intensities with elevation, and API with elevation, within the rain gauge network could not be determined. No single precipitation intensity, including total storm precipitation, showed a strong positive correlation with high API for the entire rain gauge network. It appears that any attempts to predict the precipitation characteristics which trigger headwall failure by a precipitation intensity threshold in the central Oregon Coast Range is not possible. Attempts to assess the risk of headwall failure by high API may be possible. High precipitation intensities occurred with high antecedent precipitation conditions and they occur at the highest antecedent precipitation conditions. Close

• 2. [Article] A stochastic precipitation event model for use in erosion simulations

  Mathematical models of the precipitation process are needed to effectively use historical precipitation data in the design and planning of engineering projects and for analysis of watershed runoff behavior. ...

  Citation × Citation Citation Abstract Copy Title: A stochastic precipitation event model for use in erosion simulations Author: Istok, J. D. Mathematical models of the precipitation process are needed to effectively use historical precipitation data in the design and planning of engineering projects and for analysis of watershed runoff behavior. Existing simple models based on the assumptions of independent, identically-distributed random variables are insufficient to describe several features of the historical precipitation process. The objective of this research was to develop a stochastic model of hourly precipitation that preserves the pattern of occurrence of precipitation events throughout the year as well as several characteristics of the duration, amount, and intensity of precipitation within events. Historical precipitation data for Salem, Oregon were analyzed to identify the patterns of occurrence of precipitation events and the dependence structure of the precipitation during events. The results of this analysis were used to guide the development of a general model of the precipitation process, based on the theory of stochastic cluster processes. The developed model consists of several parts. A Poisson cluster process is used to describe the pattern of occurrence of precipitation events. In this process, the time between clusters and the number of events within clusters are exponentially distributed random variables. The duration of events and the time between events within clusters are described with identical Logarithmic Negative Mixture distributions. The hourly precipitation amounts within events are described with a nonstationary, first-order autoregression model. To test the precipitation model, parameters were estimated for each month using 31 years of hourly precipitation data for Salem and Pendleton, Oregon, two stations from very different climatic regimes. The results of Monte Carlo simulations showed that the model accurately reproduces the seasonal pattern of event occurrence and the marginal and conditional distributions of the magnitude, duration, and intensity of precipitation during events. Autocorrelation functions for the historical and simulated data were also similar. It is concluded that the model has potential for use in many hydrologic applications that use historical precipitation data. Title: A stochastic precipitation event model for use in erosion simulations Author: Istok, J. D. Mathematical models of the precipitation process are needed to effectively use historical precipitation data in the design and planning of engineering projects and for analysis of watershed runoff behavior. Existing simple models based on the assumptions of independent, identically-distributed random variables are insufficient to describe several features of the historical precipitation process. The objective of this research was to develop a stochastic model of hourly precipitation that preserves the pattern of occurrence of precipitation events throughout the year as well as several characteristics of the duration, amount, and intensity of precipitation within events. Historical precipitation data for Salem, Oregon were analyzed to identify the patterns of occurrence of precipitation events and the dependence structure of the precipitation during events. The results of this analysis were used to guide the development of a general model of the precipitation process, based on the theory of stochastic cluster processes. The developed model consists of several parts. A Poisson cluster process is used to describe the pattern of occurrence of precipitation events. In this process, the time between clusters and the number of events within clusters are exponentially distributed random variables. The duration of events and the time between events within clusters are described with identical Logarithmic Negative Mixture distributions. The hourly precipitation amounts within events are described with a nonstationary, first-order autoregression model. To test the precipitation model, parameters were estimated for each month using 31 years of hourly precipitation data for Salem and Pendleton, Oregon, two stations from very different climatic regimes. The results of Monte Carlo simulations showed that the model accurately reproduces the seasonal pattern of event occurrence and the marginal and conditional distributions of the magnitude, duration, and intensity of precipitation during events. Autocorrelation functions for the historical and simulated data were also similar. It is concluded that the model has potential for use in many hydrologic applications that use historical precipitation data. Close

• 3. [Article] Evaluation of precipitation data applied to hydrological simulation using MMS-PRMS for the Whitewater River Basin in Kansas

  Precipitation is one of the most important components contributing to hydrological dynamics. Spatially distributed precipitation data can be obtained by satellite, radar, rain gages, etc, to serve various ...

  Citation × Citation Citation Abstract Copy Title: Evaluation of precipitation data applied to hydrological simulation using MMS-PRMS for the Whitewater River Basin in Kansas Author: Lin, Wei Precipitation is one of the most important components contributing to hydrological dynamics. Spatially distributed precipitation data can be obtained by satellite, radar, rain gages, etc, to serve various purposes. Currently, the most commonly used precipitation data still rely on gage-based measurement techniques that provide timely precipitation information with high quality and reliability. The National Oceanic and Atmospheric Administration (NOAA) and its cooperative climate stations are the primary resources of this form of precipitation data at the federal level. For hydrological simulation of precipitation-runoff for a watershed, precipitation is a critical model input that has a significant impact on the certainty and accuracy of simulation. To better understand the hydrological process within Whitewater River Basin in Kansas, the Precipitation-Runoff Model System (PRMS) was applied to this area, where the Cooperative Atmosphere-Surface Exchange Study (CASES) has set up an intensively instrumented site managed by Hydrologic Science Team (HST) of Oregon State University for rainfall data collection. Two rainfall data sources, NOAA and HST, were used in this study to simulate the stream response to rainfall within the basin. Different simulation results were acquired compared and analyzed. The study concluded that better simulation results were obtained with MMS-PRMS using integrated spatially distributed precipitation data, which was not available as a standard NOAA product. For a large basin, it is necessary to collect precipitation data within the area of interest in addition to standard NOAA data to produce an accurate hydrological model. It was suggested that to guarantee the quality of precipitation-runoff simulation using MMS-PRMS, the coverage of each rain gage should not be larger than 40 to 50 square kilometers (about 15-20 square miles). It was also learned that the precipitation data from local supplementary measurements are unlikely to be a satisfactory substitute for current NOAA data in hydrological simulation due to the short time period of measurement. The combination of standard NOAA data and additional data from an intensively measured site, such as CASES, or from radar, would allow more for better simulation. Title: Evaluation of precipitation data applied to hydrological simulation using MMS-PRMS for the Whitewater River Basin in Kansas Author: Lin, Wei Precipitation is one of the most important components contributing to hydrological dynamics. Spatially distributed precipitation data can be obtained by satellite, radar, rain gages, etc, to serve various purposes. Currently, the most commonly used precipitation data still rely on gage-based measurement techniques that provide timely precipitation information with high quality and reliability. The National Oceanic and Atmospheric Administration (NOAA) and its cooperative climate stations are the primary resources of this form of precipitation data at the federal level. For hydrological simulation of precipitation-runoff for a watershed, precipitation is a critical model input that has a significant impact on the certainty and accuracy of simulation. To better understand the hydrological process within Whitewater River Basin in Kansas, the Precipitation-Runoff Model System (PRMS) was applied to this area, where the Cooperative Atmosphere-Surface Exchange Study (CASES) has set up an intensively instrumented site managed by Hydrologic Science Team (HST) of Oregon State University for rainfall data collection. Two rainfall data sources, NOAA and HST, were used in this study to simulate the stream response to rainfall within the basin. Different simulation results were acquired compared and analyzed. The study concluded that better simulation results were obtained with MMS-PRMS using integrated spatially distributed precipitation data, which was not available as a standard NOAA product. For a large basin, it is necessary to collect precipitation data within the area of interest in addition to standard NOAA data to produce an accurate hydrological model. It was suggested that to guarantee the quality of precipitation-runoff simulation using MMS-PRMS, the coverage of each rain gage should not be larger than 40 to 50 square kilometers (about 15-20 square miles). It was also learned that the precipitation data from local supplementary measurements are unlikely to be a satisfactory substitute for current NOAA data in hydrological simulation due to the short time period of measurement. The combination of standard NOAA data and additional data from an intensively measured site, such as CASES, or from radar, would allow more for better simulation. Close

• 4. [Article] An analysis of the distribution of precipitation and runoff from the historical record for the continental United States

  Characterizing the distribution of precipitation at regional scales is a requirement for the development of regional scale, spatially distributed hydrologic water balance models. This study performs a ...

  Citation × Citation Citation Abstract Copy Title: An analysis of the distribution of precipitation and runoff from the historical record for the continental United States Author: Dolph, Jayne Ellen Characterizing the distribution of precipitation at regional scales is a requirement for the development of regional scale, spatially distributed hydrologic water balance models. This study performs a preliminary assessment of the utility and limitations of historical hydro-meteorological data for providing spatially distributed precipitation estimates over large areas. The historical data are used in a spatial analysis to characterize regional patterns of precipitation and runoff across the conterminous United States. Precipitation and runoff "surfaces" generated from interpolation of point measurements capture broad regional patterns. A distributed water balance is calculated over the continent using long-term (1948 -1988) and seven-year (1982 -1988) annual average values to check the reliability of precipitation estimates. The resulting "input-output surfaces" illustrate the deficiency (low elevation bias) of historical precipitation measurements in the mountainous western United States where snowmelt is an important component of the annual runoff. The incorporation of high elevation snow measurements into the precipitation record for the seven-year average significantly improves the water budget estimates in these regions and enhances the utility of historical data for providing spatially distributed precipitation estimates at regional and continental scales. Title: An analysis of the distribution of precipitation and runoff from the historical record for the continental United States Author: Dolph, Jayne Ellen Characterizing the distribution of precipitation at regional scales is a requirement for the development of regional scale, spatially distributed hydrologic water balance models. This study performs a preliminary assessment of the utility and limitations of historical hydro-meteorological data for providing spatially distributed precipitation estimates over large areas. The historical data are used in a spatial analysis to characterize regional patterns of precipitation and runoff across the conterminous United States. Precipitation and runoff "surfaces" generated from interpolation of point measurements capture broad regional patterns. A distributed water balance is calculated over the continent using long-term (1948 -1988) and seven-year (1982 -1988) annual average values to check the reliability of precipitation estimates. The resulting "input-output surfaces" illustrate the deficiency (low elevation bias) of historical precipitation measurements in the mountainous western United States where snowmelt is an important component of the annual runoff. The incorporation of high elevation snow measurements into the precipitation record for the seven-year average significantly improves the water budget estimates in these regions and enhances the utility of historical data for providing spatially distributed precipitation estimates at regional and continental scales. Close

• 5. [Article] Fallow-cropping systems in the Pacific Northwest

  Information contained within documents may be obsolete. Please check for recent information at the OSU Extension Service website: http://extension.oregonstate.edu/catalog/results.php?cat=Agriculture

  Citation × Citation Citation Abstract Copy Title: Fallow-cropping systems in the Pacific Northwest Author: Glenn, David Michael, Bolton, Floyd E. Information contained within documents may be obsolete. Please check for recent information at the OSU Extension Service website: http://extension.oregonstate.edu/catalog/results.php?cat=Agriculture Title: Fallow-cropping systems in the Pacific Northwest Author: Glenn, David Michael, Bolton, Floyd E. Information contained within documents may be obsolete. Please check for recent information at the OSU Extension Service website: http://extension.oregonstate.edu/catalog/results.php?cat=Agriculture Close

• 6. [Article] The late spring secondary precipitation maximum in the interior Pacific Northwest

  The Late Spring Secondary Precipitation Maximum in the Interior Pacific Northwest results from a complex system of climatic controls. The Secondary Maximum is most strongly developed over the high plateau ...

  Citation × Citation Citation Abstract Copy Title: The late spring secondary precipitation maximum in the interior Pacific Northwest Author: Quinn, Robert The Late Spring Secondary Precipitation Maximum in the Interior Pacific Northwest results from a complex system of climatic controls. The Secondary Maximum is most strongly developed over the high plateau of Oregon immediately in the lee of the Cascade Mountains. Local topographic organization exerts strong control over the magnitude and timing of the secondary maximum in the inter-montane region. There is a detectable poleward shift of the precipitation maximum in the interior Northwest from April to June. A synoptic precipitation climatology was developed for the Pacific Northwest for the months of February to July. Surface and 500 millibar circulation maps indicate reorganization of atmospheric flow from strongly zonal flow in midwinter to more highly meridional flow in May and June. Precipitation producing synoptic disturbances manifest a decided evolution from those dominated by warm advection in winter to those dominated by strong, cool advection in May and June. Spokane radiosonde data indicate that increased destabilization of the atmosphere accompanied by increased precipitable moisture is primarily responsible for the increase in average rainfall in May and June. The Secondary Precipitation Maximum is characterized by an increase in precipitation intensity, but is not accompanied by an increase in precipitation frequency. A case history of an early and late spring precipitation producing synoptic sequence is presented. Seasonal changes in precipitation intensity west and east of the Cascades must be related to corresponding changes in the sensible and latent heat budget of the region. Average monthly equivalent potential temperature data indicate pronounced reorganization of the surface temperature field west and east of the Cascades during the period of February to July. Large sensible and latent heat additions occur east of the Cascades in May and June and should be effective in destabilizing maritime polar air masses moving across the interior. Title: The late spring secondary precipitation maximum in the interior Pacific Northwest Author: Quinn, Robert The Late Spring Secondary Precipitation Maximum in the Interior Pacific Northwest results from a complex system of climatic controls. The Secondary Maximum is most strongly developed over the high plateau of Oregon immediately in the lee of the Cascade Mountains. Local topographic organization exerts strong control over the magnitude and timing of the secondary maximum in the inter-montane region. There is a detectable poleward shift of the precipitation maximum in the interior Northwest from April to June. A synoptic precipitation climatology was developed for the Pacific Northwest for the months of February to July. Surface and 500 millibar circulation maps indicate reorganization of atmospheric flow from strongly zonal flow in midwinter to more highly meridional flow in May and June. Precipitation producing synoptic disturbances manifest a decided evolution from those dominated by warm advection in winter to those dominated by strong, cool advection in May and June. Spokane radiosonde data indicate that increased destabilization of the atmosphere accompanied by increased precipitable moisture is primarily responsible for the increase in average rainfall in May and June. The Secondary Precipitation Maximum is characterized by an increase in precipitation intensity, but is not accompanied by an increase in precipitation frequency. A case history of an early and late spring precipitation producing synoptic sequence is presented. Seasonal changes in precipitation intensity west and east of the Cascades must be related to corresponding changes in the sensible and latent heat budget of the region. Average monthly equivalent potential temperature data indicate pronounced reorganization of the surface temperature field west and east of the Cascades during the period of February to July. Large sensible and latent heat additions occur east of the Cascades in May and June and should be effective in destabilizing maritime polar air masses moving across the interior. Close

• 7. [Article] An investigation of precipitation from solid solution in an aluminum-magnesium-silicon alloy using x-ray diffraction techniques

  The thesis was an investigation into the mechanism of precipitation from solid solution in an Aluminum-0.7% Magnesium-0.6% Silicon alloy containing iron impurities. Laue x-ray diffraction patterns were ...

  Citation × Citation Citation Abstract Copy Title: An investigation of precipitation from solid solution in an aluminum-magnesium-silicon alloy using x-ray diffraction techniques Author: Guthrie, J. L. (James Leonard), 1937- The thesis was an investigation into the mechanism of precipitation from solid solution in an Aluminum-0.7% Magnesium-0.6% Silicon alloy containing iron impurities. Laue x-ray diffraction patterns were obtained from solution heat treated and aged single crystal specimens in various crystallographic orientations. Precipitation related streaking was detected on some of the patterns from aged specimens. From an analysis of the streaking it was concluded that precipitate stringlets formed during the early stages of precipitation and that the stringlets were coherent with the solid solution in the <100> directions. From the experimental results it was not possible to determine the degree of strengthening due to coherency. Title: An investigation of precipitation from solid solution in an aluminum-magnesium-silicon alloy using x-ray diffraction techniques Author: Guthrie, J. L. (James Leonard), 1937- The thesis was an investigation into the mechanism of precipitation from solid solution in an Aluminum-0.7% Magnesium-0.6% Silicon alloy containing iron impurities. Laue x-ray diffraction patterns were obtained from solution heat treated and aged single crystal specimens in various crystallographic orientations. Precipitation related streaking was detected on some of the patterns from aged specimens. From an analysis of the streaking it was concluded that precipitate stringlets formed during the early stages of precipitation and that the stringlets were coherent with the solid solution in the <100> directions. From the experimental results it was not possible to determine the degree of strengthening due to coherency. Close

• 8. [Article] Frequency Modes of Monsoon Precipitation in Arizona and New Mexico

  The interannual and intraseasonal variability of the North American monsoon is of great interest because a large proportion of the annual precipitation for Arizona and New Mexico arrives during the summer ...

  Citation × Citation Citation Abstract Copy Title: Frequency Modes of Monsoon Precipitation in Arizona and New Mexico Author: Hall-McKim, Eileen A., Nolin, Anne W. The interannual and intraseasonal variability of the North American monsoon is of great interest because a large proportion of the annual precipitation for Arizona and New Mexico arrives during the summer monsoon. Forty-one years of daily monsoon season precipitation data for Arizona and New Mexico were studied using wavelet analysis. This time-localized spectral analysis method reveals that periodicities of less than 8 days are positively correlated with mean daily precipitation during the 1 July–15 September monsoon period. Roughly 17% of the years indicate no significant periodicity during the monsoon period for either region and are associated with low monsoon precipitation. High- and low-frequency modes explain an equivalent percentage of the variance in monsoon precipitation in both Arizona and New Mexico, and in many years concurrent multiple periodicities occur. Wavelet analysis was effective in identifying the contribution of high-frequency modes that had not been discerned in previous studies. These results suggest that precipitation processes during the monsoon season are modulated by phenomena operating at synoptic (2–8 days) and longer (>8 days) time scales and point to the need for further studies to better understand the associated atmospheric processes. Title: Frequency Modes of Monsoon Precipitation in Arizona and New Mexico Author: Hall-McKim, Eileen A., Nolin, Anne W. The interannual and intraseasonal variability of the North American monsoon is of great interest because a large proportion of the annual precipitation for Arizona and New Mexico arrives during the summer monsoon. Forty-one years of daily monsoon season precipitation data for Arizona and New Mexico were studied using wavelet analysis. This time-localized spectral analysis method reveals that periodicities of less than 8 days are positively correlated with mean daily precipitation during the 1 July–15 September monsoon period. Roughly 17% of the years indicate no significant periodicity during the monsoon period for either region and are associated with low monsoon precipitation. High- and low-frequency modes explain an equivalent percentage of the variance in monsoon precipitation in both Arizona and New Mexico, and in many years concurrent multiple periodicities occur. Wavelet analysis was effective in identifying the contribution of high-frequency modes that had not been discerned in previous studies. These results suggest that precipitation processes during the monsoon season are modulated by phenomena operating at synoptic (2–8 days) and longer (>8 days) time scales and point to the need for further studies to better understand the associated atmospheric processes. Close

• 9. [Article] Paired stable isotopologues in precipitation and vapor: A case study of the amount effect within western tropical Pacific storms

  Access to this item has been restricted by repository administrators at the request of the publisher until October 16, 2016.

  Citation × Citation Citation Abstract Copy Title: Paired stable isotopologues in precipitation and vapor: A case study of the amount effect within western tropical Pacific storms Author: Noone, David, Cobb, Kim M., Conroy, Jessica L., Konecky, Bronwen L., Moerman, Jessica W. Access to this item has been restricted by repository administrators at the request of the publisher until October 16, 2016. Title: Paired stable isotopologues in precipitation and vapor: A case study of the amount effect within western tropical Pacific storms Author: Noone, David, Cobb, Kim M., Conroy, Jessica L., Konecky, Bronwen L., Moerman, Jessica W. Access to this item has been restricted by repository administrators at the request of the publisher until October 16, 2016. Close

• 10. [Article] Three Recent Flavors of Drought in the Pacific Northwest

  In common with much of the western United States, the Pacific Northwest (defined in this paper as Washington and Oregon) has experienced an unusual number of droughts in the past decade. This paper describes ...

  Citation × Citation Citation Abstract Copy Title: Three Recent Flavors of Drought in the Pacific Northwest Author: Bumbaco, Karin A., Mote, Philip W. In common with much of the western United States, the Pacific Northwest (defined in this paper as Washington and Oregon) has experienced an unusual number of droughts in the past decade. This paper describes three of these droughts in terms of the precipitation, temperature, and soil moisture anomalies, and discusses different drought impacts experienced in the Pacific Northwest (PNW). For the first drought, in 2001, low winter precipitation in the PNW produced very low streamflow that primarily affected farmers and hydropower generation. For the second, in 2003, low summer precipitation in Washington (WA), and low summer precipitation and a warm winter in Oregon (OR) primarily affected streamflow and forests. For the last, in 2005, a lack of snowpack due to warm temperatures during significant winter precipitation events in WA, and low winter precipitation in OR, had a variety of different agricultural and hydrologic impacts. Although the proximal causes of droughts are easily quantified, the ultimate causes are not as clear. Better precipitation observations in the PNW are required to provide timely monitoring of conditions leading to droughts to improve prediction in the future Title: Three Recent Flavors of Drought in the Pacific Northwest Author: Bumbaco, Karin A., Mote, Philip W. In common with much of the western United States, the Pacific Northwest (defined in this paper as Washington and Oregon) has experienced an unusual number of droughts in the past decade. This paper describes three of these droughts in terms of the precipitation, temperature, and soil moisture anomalies, and discusses different drought impacts experienced in the Pacific Northwest (PNW). For the first drought, in 2001, low winter precipitation in the PNW produced very low streamflow that primarily affected farmers and hydropower generation. For the second, in 2003, low summer precipitation in Washington (WA), and low summer precipitation and a warm winter in Oregon (OR) primarily affected streamflow and forests. For the last, in 2005, a lack of snowpack due to warm temperatures during significant winter precipitation events in WA, and low winter precipitation in OR, had a variety of different agricultural and hydrologic impacts. Although the proximal causes of droughts are easily quantified, the ultimate causes are not as clear. Better precipitation observations in the PNW are required to provide timely monitoring of conditions leading to droughts to improve prediction in the future Close