Search

Search Results

• 1. [Article] Application of Tree-Structured Regression for Regional Precipitation Prediction Using General Circulation Model Output

  This study presents a tree-structured regression (TSR) method to relate daily precipitation with a variety of free-atmosphere variables. Historical data were used to identify distinct weather patterns ...

  Citation × Citation Citation Abstract Copy Title: Application of Tree-Structured Regression for Regional Precipitation Prediction Using General Circulation Model Output Author: Li, Xiangshang, Sailor, David J. Year: 2000 This study presents a tree-structured regression (TSR) method to relate daily precipitation with a variety of free-atmosphere variables. Historical data were used to identify distinct weather patterns associated with differing types of precipitation events. Models were developed using 67% of the data for training and the remaining data for model validation. Seasonal models were built for each of 2 US sites: San Francisco, California, and San Antonio, Texas. The average correlation between observed and simulated daily precipitation data series is 0.75 for the training set and 0.68 for the validation set. Relative humidity was found to be the dominant variable in these TSR models. Output from an NCAR CSM (climate system model) transient simulation of climate change were then used to drive the TSR models in the prediction of precipitation characteristics under climate change. A preliminary screening of the GCM output variables for current climate, however, revealed significant problems for the San Antonio site. Specifically, the CSM missed the annual trends in humidity for the grid cell containing this site. CSM output for the San Francisco site was found to be much more reliable. Therefore, we present future precipitation estimates only for the San Francisco site. Title: Application of Tree-Structured Regression for Regional Precipitation Prediction Using General Circulation Model Output Author: Li, Xiangshang, Sailor, David J. Year: 2000 This study presents a tree-structured regression (TSR) method to relate daily precipitation with a variety of free-atmosphere variables. Historical data were used to identify distinct weather patterns associated with differing types of precipitation events. Models were developed using 67% of the data for training and the remaining data for model validation. Seasonal models were built for each of 2 US sites: San Francisco, California, and San Antonio, Texas. The average correlation between observed and simulated daily precipitation data series is 0.75 for the training set and 0.68 for the validation set. Relative humidity was found to be the dominant variable in these TSR models. Output from an NCAR CSM (climate system model) transient simulation of climate change were then used to drive the TSR models in the prediction of precipitation characteristics under climate change. A preliminary screening of the GCM output variables for current climate, however, revealed significant problems for the San Antonio site. Specifically, the CSM missed the annual trends in humidity for the grid cell containing this site. CSM output for the San Francisco site was found to be much more reliable. Therefore, we present future precipitation estimates only for the San Francisco site. Close

• 2. [Article] Climate Change Assessment in Columbia River Basin (CRB) Using Copula Based on Coupling of Temperature and Precipitation

  The multi downscaled-scenario products allow us to better assess the uncertainty of the variations of precipitation and temperature in the current and future periods. Joint Probability distribution functions ...

  Citation × Citation Citation Abstract Copy Title: Climate Change Assessment in Columbia River Basin (CRB) Using Copula Based on Coupling of Temperature and Precipitation Author: Qin, Yueyue Year: 2015 The multi downscaled-scenario products allow us to better assess the uncertainty of the variations of precipitation and temperature in the current and future periods. Joint Probability distribution functions (PDFs), of both the climatic variables, might help better understand the interdependence of the two, and thus in-turn help in accessing the future with confidence. In the present study, we have used multi-modelled statistically downscaled ensemble of precipitation and temperature variables. The dataset used is multi-model ensemble of 10 Global Climate Models (GCMs) downscaled product from CMIP5 daily dataset, using the Bias Correction and Spatial Downscaling (BCSD) technique, generated at Portland State University. The multi-model ensemble PDFs of both precipitation and temperature is evaluated for summer (dry) and winter (wet) periods for 10 sub-basins across Columbia River Basin (CRB). Eventually, Copula is applied to establish the joint distribution of two variables on multi-model ensemble data. Results have indicated that the probabilistic distribution helps remove the limitations on marginal distributions of variables in question and helps in better prediction. The joint distribution is then used to estimate the change in trends of said variables in future, along with estimation of the probabilities of the given change. The joint distribution trends are varied, but certainly positive, for summer and winter time scales based on sub-basins. Dry season, generally, is indicating towards higher positive changes in precipitation than temperature (as compared to historical) across sub-basins with wet season inferring otherwise. Probabilities of changes in future, as estimated by the joint precipitation and temperature, also indicates varied degree and forms during dry season whereas the wet season is rather constant across all the sub-basins. Title: Climate Change Assessment in Columbia River Basin (CRB) Using Copula Based on Coupling of Temperature and Precipitation Author: Qin, Yueyue Year: 2015 The multi downscaled-scenario products allow us to better assess the uncertainty of the variations of precipitation and temperature in the current and future periods. Joint Probability distribution functions (PDFs), of both the climatic variables, might help better understand the interdependence of the two, and thus in-turn help in accessing the future with confidence. In the present study, we have used multi-modelled statistically downscaled ensemble of precipitation and temperature variables. The dataset used is multi-model ensemble of 10 Global Climate Models (GCMs) downscaled product from CMIP5 daily dataset, using the Bias Correction and Spatial Downscaling (BCSD) technique, generated at Portland State University. The multi-model ensemble PDFs of both precipitation and temperature is evaluated for summer (dry) and winter (wet) periods for 10 sub-basins across Columbia River Basin (CRB). Eventually, Copula is applied to establish the joint distribution of two variables on multi-model ensemble data. Results have indicated that the probabilistic distribution helps remove the limitations on marginal distributions of variables in question and helps in better prediction. The joint distribution is then used to estimate the change in trends of said variables in future, along with estimation of the probabilities of the given change. The joint distribution trends are varied, but certainly positive, for summer and winter time scales based on sub-basins. Dry season, generally, is indicating towards higher positive changes in precipitation than temperature (as compared to historical) across sub-basins with wet season inferring otherwise. Probabilities of changes in future, as estimated by the joint precipitation and temperature, also indicates varied degree and forms during dry season whereas the wet season is rather constant across all the sub-basins. Close

• 3. [Article] Climate Change and Freshwater Resources in Oregon

  Climate change will affect various sectors of water resources in Oregon in the 21st century. The observed trends in streamflow show significant declines in September flow and, although not significant, ...

  Citation × Citation Citation Abstract Copy Title: Climate Change and Freshwater Resources in Oregon Author: Chang, Heejun, Jones, Julie Year: 2010 Climate change will affect various sectors of water resources in Oregon in the 21st century. The observed trends in streamflow show significant declines in September flow and, although not significant, increases in March flow in many transient rain-snow basins. These streamflow trends are associated with rising temperature and coincident declines in snowpack in spring in the latter half of the 20th century. While there are no distinct trends in high precipitation events, such events are associated with climate variability such as ENSO and PDO. Effects of ENSO and PDO are more pronounced at the beginning and end of the wet season in the Willamette River basin. The amount and seasonality of water supply is projected to shift as the distribution of precipitation changes and temperatures rise. Higher summer air temperatures accompanied by reduced precipitation are projected to increase evapotranspiration and decrease stream flow in summer. Although there are no distinct spatial patterns of changes in precipitation and temperature across the State in the 21st century (uniform increase in temperature across the region), significant regional variations do exist. The magnitude of change depends on the importance of snow in the current water budget, so projected changes are greater for mountainous regions than for low-elevation areas. Transient rain-snow basins, such as those in the Western Cascade basins, are projected to be more sensitive to these changes in precipitation and temperature. The high Cascade basins that are primarily fed by deep groundwater systems could sustain low flow during summer months. Basins in the east of the Cascades are projected to have low summer flow in a distant future as groundwater recharge declines over time. April 1 snow water equivalent (SWE) will decline and the center timing of runoff will become earlier in transient rain-snow basins as snowpack is projected to decline consistently in the 21st century. These model projections should be viewed with caution for several reasons when considering climate change impacts on water supply in Oregon. First, this chapter shows that few consistent trends in runoff are apparent in streamflow records from Oregon; instead, the direction and magnitude of change in streamflow varies by season, by basin size, and among ecoregions in Oregon. Second, observed streamflow trends (e.g., declining flows in summer, or in September) may be explained by factors that may not be directly related to global climate change. For example, recent low-flow years are attributable to low precipitation years (especially 2001 and 2005) and perhaps to interannual variations in snowpack associated with cyclical variation in ocean temperatures, while long-term decreases in summer flows are attributable to the combination of summer precipitation decline and increasing water withdrawals for consumptive use. Third, model projections do not account for possible resilience and adaptations in natural ecosystems that may alter water use and lead to smaller than expected changes in streamflow. More work is needed on vegetation responses to climate variability, the interactions between soil water and vegetation, and the relationship between streamflow and precipitation (runoff ratios) in large basins. Title: Climate Change and Freshwater Resources in Oregon Author: Chang, Heejun, Jones, Julie Year: 2010 Climate change will affect various sectors of water resources in Oregon in the 21st century. The observed trends in streamflow show significant declines in September flow and, although not significant, increases in March flow in many transient rain-snow basins. These streamflow trends are associated with rising temperature and coincident declines in snowpack in spring in the latter half of the 20th century. While there are no distinct trends in high precipitation events, such events are associated with climate variability such as ENSO and PDO. Effects of ENSO and PDO are more pronounced at the beginning and end of the wet season in the Willamette River basin. The amount and seasonality of water supply is projected to shift as the distribution of precipitation changes and temperatures rise. Higher summer air temperatures accompanied by reduced precipitation are projected to increase evapotranspiration and decrease stream flow in summer. Although there are no distinct spatial patterns of changes in precipitation and temperature across the State in the 21st century (uniform increase in temperature across the region), significant regional variations do exist. The magnitude of change depends on the importance of snow in the current water budget, so projected changes are greater for mountainous regions than for low-elevation areas. Transient rain-snow basins, such as those in the Western Cascade basins, are projected to be more sensitive to these changes in precipitation and temperature. The high Cascade basins that are primarily fed by deep groundwater systems could sustain low flow during summer months. Basins in the east of the Cascades are projected to have low summer flow in a distant future as groundwater recharge declines over time. April 1 snow water equivalent (SWE) will decline and the center timing of runoff will become earlier in transient rain-snow basins as snowpack is projected to decline consistently in the 21st century. These model projections should be viewed with caution for several reasons when considering climate change impacts on water supply in Oregon. First, this chapter shows that few consistent trends in runoff are apparent in streamflow records from Oregon; instead, the direction and magnitude of change in streamflow varies by season, by basin size, and among ecoregions in Oregon. Second, observed streamflow trends (e.g., declining flows in summer, or in September) may be explained by factors that may not be directly related to global climate change. For example, recent low-flow years are attributable to low precipitation years (especially 2001 and 2005) and perhaps to interannual variations in snowpack associated with cyclical variation in ocean temperatures, while long-term decreases in summer flows are attributable to the combination of summer precipitation decline and increasing water withdrawals for consumptive use. Third, model projections do not account for possible resilience and adaptations in natural ecosystems that may alter water use and lead to smaller than expected changes in streamflow. More work is needed on vegetation responses to climate variability, the interactions between soil water and vegetation, and the relationship between streamflow and precipitation (runoff ratios) in large basins. Close

• 4. [Article] Understanding the Joint Behavior of Temperature and Precipitation for Climate Change Impact Studies

  The multiple downscaled-scenario products allow us to assess the uncertainty of the variations of precipitation and temperature in the current and future periods. Probabilistic assessments of both climatic ...

  Citation × Citation Citation Abstract Copy Title: Understanding the Joint Behavior of Temperature and Precipitation for Climate Change Impact Studies Author: Rana, Arun, Moradkhani, Hamid, Qin, Yueyue Year: 2016 The multiple downscaled-scenario products allow us to assess the uncertainty of the variations of precipitation and temperature in the current and future periods. Probabilistic assessments of both climatic variables help better understand the interdependence of the two, and thus in-turn help in assessing the future with confidence. In the present study, we use ensemble of statistically downscaled precipitation and temperature from various models. The dataset used is multi-model ensemble of 10 Global Climate Models (GCMs) downscaled product from CMIP5 daily dataset, using the Bias Correction and Spatial Downscaling (BCSD) technique, generated at Portland State University. The multi-model ensemble of both precipitation and temperature is evaluated for dry and wet periods for 10 sub-basins across Columbia River Basin (CRB). Thereafter, Copula is applied to establish the joint distribution of two variables on multi-model ensemble data. The joint distribution is then used to estimate the change in trends of said variables in future, along with estimation of the probabilities of the given change. The joint distribution trends varies, but certainly positive, for dry and wet periods in sub-basins of CRB. Dry season, generally, is indicating a higher positive change in precipitation than temperature (as compared to historical) across sub-basins with wet season inferring otherwise. Probabilities of changes in future, as estimated from the joint distribution indicate varied degrees and forms during dry season whereas the wet season is rather constant across all the sub-basins. Title: Understanding the Joint Behavior of Temperature and Precipitation for Climate Change Impact Studies Author: Rana, Arun, Moradkhani, Hamid, Qin, Yueyue Year: 2016 The multiple downscaled-scenario products allow us to assess the uncertainty of the variations of precipitation and temperature in the current and future periods. Probabilistic assessments of both climatic variables help better understand the interdependence of the two, and thus in-turn help in assessing the future with confidence. In the present study, we use ensemble of statistically downscaled precipitation and temperature from various models. The dataset used is multi-model ensemble of 10 Global Climate Models (GCMs) downscaled product from CMIP5 daily dataset, using the Bias Correction and Spatial Downscaling (BCSD) technique, generated at Portland State University. The multi-model ensemble of both precipitation and temperature is evaluated for dry and wet periods for 10 sub-basins across Columbia River Basin (CRB). Thereafter, Copula is applied to establish the joint distribution of two variables on multi-model ensemble data. The joint distribution is then used to estimate the change in trends of said variables in future, along with estimation of the probabilities of the given change. The joint distribution trends varies, but certainly positive, for dry and wet periods in sub-basins of CRB. Dry season, generally, is indicating a higher positive change in precipitation than temperature (as compared to historical) across sub-basins with wet season inferring otherwise. Probabilities of changes in future, as estimated from the joint distribution indicate varied degrees and forms during dry season whereas the wet season is rather constant across all the sub-basins. Close

• 5. [Article] Coupling snowpack and groundwater dynamics to interpret historical streamflow trends in the western United States

  To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. The published article is copyrighted by Wiley-Blackwell and can be found at: http:...

  Citation × Citation Citation Abstract Copy Title: Coupling snowpack and groundwater dynamics to interpret historical streamflow trends in the western United States Author: Lewis, Sarah L., Safeeq, Mohammad, Tague, Christina. L., Grant, Gordon E. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. The published article is copyrighted by Wiley-Blackwell and can be found at: http://onlinelibrary.wiley.com/. Title: Coupling snowpack and groundwater dynamics to interpret historical streamflow trends in the western United States Author: Lewis, Sarah L., Safeeq, Mohammad, Tague, Christina. L., Grant, Gordon E. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. The published article is copyrighted by Wiley-Blackwell and can be found at: http://onlinelibrary.wiley.com/. Close

• 6. [Article] A Comparative Assessment of Projected Meteorological and Hydrological Droughts: Elucidating the Role of Temperature

  The changing climate and the associated future increases in temperature are expected to have impacts on drought characteristics and hydrologic cycle. This paper investigates the projected changes in spatiotemporal ...

  Citation × Citation Citation Abstract Copy Title: A Comparative Assessment of Projected Meteorological and Hydrological Droughts: Elucidating the Role of Temperature Author: Ahmadalipour, Ali, Moradkhani, Hamid, Demirel, Mehmet C. Year: 2017 The changing climate and the associated future increases in temperature are expected to have impacts on drought characteristics and hydrologic cycle. This paper investigates the projected changes in spatiotemporal characteristics of droughts and their future attributes over the Willamette River Basin (WRB) in the Pacific Northwest U.S. The analysis is performed using two subsets of downscaled CMIP5 global climate models (GCMs) each consisting of 10 models from two future scenarios (RCP4.5 and RCP8.5) for 30 years of historical period (1970–1999) and 90 years of future projections (2010–2099). Hydrologic modeling is conducted using the Precipitation Runoff Modeling System (PRMS) as a robust distributed hydrologic model with lower computational cost compared to other models. Meteorological and hydrological droughts are studied using three drought indices (i.e. Standardized Precipitation Index, Standardized Precipitation Evapotranspiration Index, Standardized Streamflow Index). Results reveal that the intensity and duration of hydrological droughts are expected to increase over the WRB, albeit the annual precipitation is expected to increase. On the other hand, the intensity of meteorological droughts do not indicate an aggravation for most cases. We explore the changes of hydrometeolorogical variables over the basin in order to understand the causes for such differences and to discover the controlling factors of drought. Furthermore, the uncertainty of projections are quantified for model, scenario, and downscaling uncertainty. Title: A Comparative Assessment of Projected Meteorological and Hydrological Droughts: Elucidating the Role of Temperature Author: Ahmadalipour, Ali, Moradkhani, Hamid, Demirel, Mehmet C. Year: 2017 The changing climate and the associated future increases in temperature are expected to have impacts on drought characteristics and hydrologic cycle. This paper investigates the projected changes in spatiotemporal characteristics of droughts and their future attributes over the Willamette River Basin (WRB) in the Pacific Northwest U.S. The analysis is performed using two subsets of downscaled CMIP5 global climate models (GCMs) each consisting of 10 models from two future scenarios (RCP4.5 and RCP8.5) for 30 years of historical period (1970–1999) and 90 years of future projections (2010–2099). Hydrologic modeling is conducted using the Precipitation Runoff Modeling System (PRMS) as a robust distributed hydrologic model with lower computational cost compared to other models. Meteorological and hydrological droughts are studied using three drought indices (i.e. Standardized Precipitation Index, Standardized Precipitation Evapotranspiration Index, Standardized Streamflow Index). Results reveal that the intensity and duration of hydrological droughts are expected to increase over the WRB, albeit the annual precipitation is expected to increase. On the other hand, the intensity of meteorological droughts do not indicate an aggravation for most cases. We explore the changes of hydrometeolorogical variables over the basin in order to understand the causes for such differences and to discover the controlling factors of drought. Furthermore, the uncertainty of projections are quantified for model, scenario, and downscaling uncertainty. Close

• 7. [Article] Watershed Response to Climate Change and Fire-Burns in the Upper Umatilla River Basin Using the Precipitation Runoff Modeling System

  This study provides an analysis of watershed response to climate change and forest fire impacts, to better understand the hydrologic budget and inform water management decisions for present and future ...

  Citation × Citation Citation Abstract Copy Title: Watershed Response to Climate Change and Fire-Burns in the Upper Umatilla River Basin Using the Precipitation Runoff Modeling System Author: Yazzie, Kimberly Crystal Year: 2016 This study provides an analysis of watershed response to climate change and forest fire impacts, to better understand the hydrologic budget and inform water management decisions for present and future needs. The study site is 2,365 km2, located in the upper Umatilla River Basin (URB) in northeastern Oregon. The Precipitation Runoff Modeling System, a distributed-parameter, physical-process watershed model, was used in this study. Model calibration yielded a Nash Sutcliffe Model Efficiency of 0.73 for both calibration (1995-2010) and validation (2010-2014) of daily streamflow. Ten Global Climate Models using Coupled Model Intercomparison Project Phase 5 experiments with Representative Concentration Pathways 4.5 and 8.5 (RCP), were used to observe hydrologic regime shifts in the 2020s, 2050s, and 2080s. Mean center timing of flow occurs earlier in the year in both pre- and post-fire conditions, where there are increased winter flows and decreased summer flows throughout the 21st century. Change in temperature and percent change in precipitation is more variable in the summer than winter increasing over time, with a slight decrease in winter precipitation in the 2080s in RCP 8.5. Temperature increases 1.6°C in RCP 4.5 and 3.3°C in RCP 8.5 by the end of the 21st century. The ratio of Snow Water Equivalent to Precipitation decreases 96% in the 2080s in RCP 8.5 before forest cover reduction, and decreases 90-99% after forest cover reduction. Potential basin recharge and the base-flow index are both sustained throughout the 21st century with slight declines before forest cover reduction, with an increase in basin recharge and increase in base-flows in the 2080s after fire-burns. However, the simulated sustained base-flows and area-weighted basin recharge in this study, do not take into account the complex geologic structure of the Columbia River Basalt Group (CRBG). A more robust characterization and simulation of URB aquifer recharge would involve coupling the PRMS model with a groundwater model in a future study. Although groundwater recharge in the CRBG in the URB is not well understood, the long-term decline of groundwater storage presents a serious environmental challenge for the Confederated Tribes of the Umatilla Indian Reservation and communities in the URB. Title: Watershed Response to Climate Change and Fire-Burns in the Upper Umatilla River Basin Using the Precipitation Runoff Modeling System Author: Yazzie, Kimberly Crystal Year: 2016 This study provides an analysis of watershed response to climate change and forest fire impacts, to better understand the hydrologic budget and inform water management decisions for present and future needs. The study site is 2,365 km2, located in the upper Umatilla River Basin (URB) in northeastern Oregon. The Precipitation Runoff Modeling System, a distributed-parameter, physical-process watershed model, was used in this study. Model calibration yielded a Nash Sutcliffe Model Efficiency of 0.73 for both calibration (1995-2010) and validation (2010-2014) of daily streamflow. Ten Global Climate Models using Coupled Model Intercomparison Project Phase 5 experiments with Representative Concentration Pathways 4.5 and 8.5 (RCP), were used to observe hydrologic regime shifts in the 2020s, 2050s, and 2080s. Mean center timing of flow occurs earlier in the year in both pre- and post-fire conditions, where there are increased winter flows and decreased summer flows throughout the 21st century. Change in temperature and percent change in precipitation is more variable in the summer than winter increasing over time, with a slight decrease in winter precipitation in the 2080s in RCP 8.5. Temperature increases 1.6°C in RCP 4.5 and 3.3°C in RCP 8.5 by the end of the 21st century. The ratio of Snow Water Equivalent to Precipitation decreases 96% in the 2080s in RCP 8.5 before forest cover reduction, and decreases 90-99% after forest cover reduction. Potential basin recharge and the base-flow index are both sustained throughout the 21st century with slight declines before forest cover reduction, with an increase in basin recharge and increase in base-flows in the 2080s after fire-burns. However, the simulated sustained base-flows and area-weighted basin recharge in this study, do not take into account the complex geologic structure of the Columbia River Basalt Group (CRBG). A more robust characterization and simulation of URB aquifer recharge would involve coupling the PRMS model with a groundwater model in a future study. Although groundwater recharge in the CRBG in the URB is not well understood, the long-term decline of groundwater storage presents a serious environmental challenge for the Confederated Tribes of the Umatilla Indian Reservation and communities in the URB. Close

• 8. [Article] Utilizing Humidity and Temperature Data to Advance Monitoring and Prediction of Meteorological Drought

  The fraction of land area over the Continental United States experiencing extreme hot and dry conditions has been increasing over the past several decades, consistent with expectation from anthropogenic ...

  Citation × Citation Citation Abstract Copy Title: Utilizing Humidity and Temperature Data to Advance Monitoring and Prediction of Meteorological Drought Author: Behrangi, Ali, Loikith, Paul C., Fetzer, Eric J., Nguyen, Hai M., Granger, Stephanie L. Year: 2015 The fraction of land area over the Continental United States experiencing extreme hot and dry conditions has been increasing over the past several decades, consistent with expectation from anthropogenic climate change. A clear concurrent change in precipitation, however, has not been confirmed. Vapor pressure deficit (VPD), combining temperature and humidity, is utilized here as an indicator of the background atmospheric conditions associated with meteorological drought. Furthermore, atmospheric conditions associated with warm season drought events are assessed by partitioning associated VPD anomalies into the temperature and humidity components. This approach suggests that the concurrence of anomalously high temperature and low humidity was an important driver of the rapid development and evolution of the exceptionally severe 2011 Texas and the 2012 Great Plains droughts. By classification of a decade of extreme drought events and tracking them back in time, it was found that near surface atmospheric temperature and humidity add essential information to the commonly used precipitation-based drought indicators and can advance efforts to determine the timing of drought onset and its severity. Title: Utilizing Humidity and Temperature Data to Advance Monitoring and Prediction of Meteorological Drought Author: Behrangi, Ali, Loikith, Paul C., Fetzer, Eric J., Nguyen, Hai M., Granger, Stephanie L. Year: 2015 The fraction of land area over the Continental United States experiencing extreme hot and dry conditions has been increasing over the past several decades, consistent with expectation from anthropogenic climate change. A clear concurrent change in precipitation, however, has not been confirmed. Vapor pressure deficit (VPD), combining temperature and humidity, is utilized here as an indicator of the background atmospheric conditions associated with meteorological drought. Furthermore, atmospheric conditions associated with warm season drought events are assessed by partitioning associated VPD anomalies into the temperature and humidity components. This approach suggests that the concurrence of anomalously high temperature and low humidity was an important driver of the rapid development and evolution of the exceptionally severe 2011 Texas and the 2012 Great Plains droughts. By classification of a decade of extreme drought events and tracking them back in time, it was found that near surface atmospheric temperature and humidity add essential information to the commonly used precipitation-based drought indicators and can advance efforts to determine the timing of drought onset and its severity. Close

• 9. [Article] Glacier Change in the North Cascades, Washington: 1900-2009

  Glaciers respond to local climate changes making them important indicators of regional climate change. The North Cascades region of Washington is the most glaciated region in the lower-48 states with approximately ...

  Citation × Citation Citation Abstract Copy Title: Glacier Change in the North Cascades, Washington: 1900-2009 Author: Dick, Kristina Amanda Year: 2013 Glaciers respond to local climate changes making them important indicators of regional climate change. The North Cascades region of Washington is the most glaciated region in the lower-48 states with approximately 25% of all glaciers and 40% of the total ice-covered area. While there are many on-going investigations of specific glaciers, little research has addressed the entire glacier cover of the region. A reference inventory of glaciers was derived from a comparison of two different inventories dating to about 1958. The different inventories agree within 93% of total number of glaciers and 94% of total ice-covered area. To quantify glacier change over the past century aerial photographs, topographic maps, and geologic maps were used. In ~1900 total area was about 533.89 ± 22.77 km2 and by 2009 the area was reduced by -56% ± 3% to 236.20 ± 12.60 km2. Most of that change occurred in the first half of the 20th century, between 1900 and 1958, -245.59 ± 25.97 km2 (-46% ± 5%) was lost, followed by a period of stability/growth in mid-century (-1% ± 3% from 1958-1990) then decline since the 1990s (-9% ± 3% from 1990-2009). The century-scale loss is associated with increasing regional temperatures warming in winter and summer; precipitation shows no trend. On a decadal time scale winter precipitation and winter and summer temperatures are important factors correlated with area loss. Topographically, smaller glaciers at lower elevations with steeper slopes and higher mean insolation exhibited greater loss than higher, gentler more shaded glaciers. Title: Glacier Change in the North Cascades, Washington: 1900-2009 Author: Dick, Kristina Amanda Year: 2013 Glaciers respond to local climate changes making them important indicators of regional climate change. The North Cascades region of Washington is the most glaciated region in the lower-48 states with approximately 25% of all glaciers and 40% of the total ice-covered area. While there are many on-going investigations of specific glaciers, little research has addressed the entire glacier cover of the region. A reference inventory of glaciers was derived from a comparison of two different inventories dating to about 1958. The different inventories agree within 93% of total number of glaciers and 94% of total ice-covered area. To quantify glacier change over the past century aerial photographs, topographic maps, and geologic maps were used. In ~1900 total area was about 533.89 ± 22.77 km2 and by 2009 the area was reduced by -56% ± 3% to 236.20 ± 12.60 km2. Most of that change occurred in the first half of the 20th century, between 1900 and 1958, -245.59 ± 25.97 km2 (-46% ± 5%) was lost, followed by a period of stability/growth in mid-century (-1% ± 3% from 1958-1990) then decline since the 1990s (-9% ± 3% from 1990-2009). The century-scale loss is associated with increasing regional temperatures warming in winter and summer; precipitation shows no trend. On a decadal time scale winter precipitation and winter and summer temperatures are important factors correlated with area loss. Topographically, smaller glaciers at lower elevations with steeper slopes and higher mean insolation exhibited greater loss than higher, gentler more shaded glaciers. Close

• 10. [Article] Assessing Mechanisms of Climate Change Impact on the Upland Forest Water Balance of the Willamette River Basin, Oregon

  Projected changes in air temperature, precipitation, and vapor pressure for the Willamette River Basin (Oregon, USA) over the next century will have significant impacts on the river basin water balance, ...

  Citation × Citation Citation Abstract Copy Title: Assessing Mechanisms of Climate Change Impact on the Upland Forest Water Balance of the Willamette River Basin, Oregon Author: Turner, David P., Conklin, David R., Vache, Kellie B., Schwartz, Cynthia, Nolin, Anne, Chang, Heejun, Watson, Eric, Bolte, John P. Year: 2016 Projected changes in air temperature, precipitation, and vapor pressure for the Willamette River Basin (Oregon, USA) over the next century will have significant impacts on the river basin water balance, notably on the amount of evapotranspiration (ET). Mechanisms of impact on ET will be both direct and indirect, but there is limited understanding of their absolute and relative magnitudes. Here, we developed a spatially explicit, daily time-step, modeling infrastructure to simulate the basin-wide water balance that accounts for meteorological influences, as well as effects mediated by changing vegetation cover type, leaf area, and ecophysiology. Three CMIP5 climate scenarios (Lowclim, Reference, and HighClim) were run for the 2010–2100 period. Besides warmer temperatures, the climate scenarios were characterized by wetter winters and increasing vapor pressure deficits. In the mid-range Reference scenario, our landscape simulation model (Envision) projected a continuation of forest cover on the uplands but a threefold increase in area burned per year. A decline (12–30%) in basin-wide mean leaf area index (LAI) in forests was projected in all scenarios. The lower LAIs drove a corresponding decline in ET. In a sensitivity test, the effect of increasing CO2 on stomatal conductance induced a further substantial decrease (11–18%) in basin-wide mean ET. The net effect of decreases in ET and increases in winter precipitation was an increase in annual streamflow. These results support the inclusion of changes in land cover, land use, LAI, and ecophysiology in efforts to anticipate impacts of climate change on basin-scale water balances. Title: Assessing Mechanisms of Climate Change Impact on the Upland Forest Water Balance of the Willamette River Basin, Oregon Author: Turner, David P., Conklin, David R., Vache, Kellie B., Schwartz, Cynthia, Nolin, Anne, Chang, Heejun, Watson, Eric, Bolte, John P. Year: 2016 Projected changes in air temperature, precipitation, and vapor pressure for the Willamette River Basin (Oregon, USA) over the next century will have significant impacts on the river basin water balance, notably on the amount of evapotranspiration (ET). Mechanisms of impact on ET will be both direct and indirect, but there is limited understanding of their absolute and relative magnitudes. Here, we developed a spatially explicit, daily time-step, modeling infrastructure to simulate the basin-wide water balance that accounts for meteorological influences, as well as effects mediated by changing vegetation cover type, leaf area, and ecophysiology. Three CMIP5 climate scenarios (Lowclim, Reference, and HighClim) were run for the 2010–2100 period. Besides warmer temperatures, the climate scenarios were characterized by wetter winters and increasing vapor pressure deficits. In the mid-range Reference scenario, our landscape simulation model (Envision) projected a continuation of forest cover on the uplands but a threefold increase in area burned per year. A decline (12–30%) in basin-wide mean leaf area index (LAI) in forests was projected in all scenarios. The lower LAIs drove a corresponding decline in ET. In a sensitivity test, the effect of increasing CO2 on stomatal conductance induced a further substantial decrease (11–18%) in basin-wide mean ET. The net effect of decreases in ET and increases in winter precipitation was an increase in annual streamflow. These results support the inclusion of changes in land cover, land use, LAI, and ecophysiology in efforts to anticipate impacts of climate change on basin-scale water balances. Close