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• 1. [Article] Impact of Soil Moisture–Atmosphere Interactions on Surface Temperature Distribution

  Understanding how different physical processes can shape the probability distribution function (PDF) of surface temperature, in particular the tails of the distribution, is essential for the attribution ...

  Citation × Citation Citation Abstract Copy Title: Impact of Soil Moisture–Atmosphere Interactions on Surface Temperature Distribution Author: Berg, Alexis, Lintner, Benjamin R., Findell, Kirsten L., Malyshev, Sergey, Loikith, Paul C., Gentine, Pierre Year: 2014 Understanding how different physical processes can shape the probability distribution function (PDF) of surface temperature, in particular the tails of the distribution, is essential for the attribution and projection of future extreme temperature events. In this study, the contribution of soil moisture–atmosphere interactions to surface temperature PDFs is investigated. Soil moisture represents a key variable in the coupling of the land and atmosphere, since it controls the partitioning of available energy between sensible and latent heat flux at the surface. Consequently, soil moisture variability driven by the atmosphere may feed back onto the near-surface climate—in particular, temperature. In this study, two simulations of the current-generation Geophysical Fluid Dynamics Laboratory (GFDL) Earth System Model, with and without interactive soil moisture, are analyzed in order to assess how soil moisture dynamics impact the simulated climate. Comparison of these simulations shows that soil moisture dynamics enhance both temperature mean and variance over regional ‘‘hotspots’’ of land–atmosphere coupling.Moreover, higher-order distribution moments, such as skewness and kurtosis, are also significantly impacted, suggesting an asymmetric impact on the positive and negative extremes of the temperature PDF. Such changes are interpreted in the context of altered distributions of the surface turbulent and radiative fluxes. That the moments of the temperature distribution may respond differentially to soil moisture dynamics underscores the importance of analyzing moments beyond the mean and variance to characterize fully the interplay of soil moisture and near-surface temperature. In addition, it is shown that soil moisture dynamics impacts daily temperature variability at different time scales over different regions in the model. Title: Impact of Soil Moisture–Atmosphere Interactions on Surface Temperature Distribution Author: Berg, Alexis, Lintner, Benjamin R., Findell, Kirsten L., Malyshev, Sergey, Loikith, Paul C., Gentine, Pierre Year: 2014 Understanding how different physical processes can shape the probability distribution function (PDF) of surface temperature, in particular the tails of the distribution, is essential for the attribution and projection of future extreme temperature events. In this study, the contribution of soil moisture–atmosphere interactions to surface temperature PDFs is investigated. Soil moisture represents a key variable in the coupling of the land and atmosphere, since it controls the partitioning of available energy between sensible and latent heat flux at the surface. Consequently, soil moisture variability driven by the atmosphere may feed back onto the near-surface climate—in particular, temperature. In this study, two simulations of the current-generation Geophysical Fluid Dynamics Laboratory (GFDL) Earth System Model, with and without interactive soil moisture, are analyzed in order to assess how soil moisture dynamics impact the simulated climate. Comparison of these simulations shows that soil moisture dynamics enhance both temperature mean and variance over regional ‘‘hotspots’’ of land–atmosphere coupling.Moreover, higher-order distribution moments, such as skewness and kurtosis, are also significantly impacted, suggesting an asymmetric impact on the positive and negative extremes of the temperature PDF. Such changes are interpreted in the context of altered distributions of the surface turbulent and radiative fluxes. That the moments of the temperature distribution may respond differentially to soil moisture dynamics underscores the importance of analyzing moments beyond the mean and variance to characterize fully the interplay of soil moisture and near-surface temperature. In addition, it is shown that soil moisture dynamics impacts daily temperature variability at different time scales over different regions in the model. Close

• 2. [Article] The Influence of Recurrent Modes of Climate Variability on the Occurrence of Winter and Summer Extreme Temperatures over North America

  The influence of the Pacific–North American (PNA) pattern, the northern annular mode (NAM), and the El Ni~no–Southern Oscillation (ENSO) on extreme temperature days and months over North America is examined. ...

  Citation × Citation Citation Abstract Copy Title: The Influence of Recurrent Modes of Climate Variability on the Occurrence of Winter and Summer Extreme Temperatures over North America Author: Loikith, Paul C., Broccoli, Anthony J. Year: 2014 The influence of the Pacific–North American (PNA) pattern, the northern annular mode (NAM), and the El Ni~no–Southern Oscillation (ENSO) on extreme temperature days and months over North America is examined. Associations between extreme temperature days and months are strongest with the PNA and NAM andweaker for ENSO. In general, the associationwith extremes tends to be stronger onmonthly than daily time scales and for winter as compared to summer. Extreme temperatures are associated with the PNAandNAMin the vicinity of the centers of action of these circulation patterns; however, many extremes also occur on days when the amplitude and polarity of these patterns do not favor their occurrence. In winter, synoptic-scale, transient weather disturbances are important drivers of extreme temperature days; however, many of these smaller-scale events are concurrent with amplified PNA or NAMpatterns. Associations are weaker in summer when other physicalmechanisms affecting the surface energy balance, such as anomalous soilmoisture content, also influence the occurrence of extreme temperatures. Title: The Influence of Recurrent Modes of Climate Variability on the Occurrence of Winter and Summer Extreme Temperatures over North America Author: Loikith, Paul C., Broccoli, Anthony J. Year: 2014 The influence of the Pacific–North American (PNA) pattern, the northern annular mode (NAM), and the El Ni~no–Southern Oscillation (ENSO) on extreme temperature days and months over North America is examined. Associations between extreme temperature days and months are strongest with the PNA and NAM andweaker for ENSO. In general, the associationwith extremes tends to be stronger onmonthly than daily time scales and for winter as compared to summer. Extreme temperatures are associated with the PNAandNAMin the vicinity of the centers of action of these circulation patterns; however, many extremes also occur on days when the amplitude and polarity of these patterns do not favor their occurrence. In winter, synoptic-scale, transient weather disturbances are important drivers of extreme temperature days; however, many of these smaller-scale events are concurrent with amplified PNA or NAMpatterns. Associations are weaker in summer when other physicalmechanisms affecting the surface energy balance, such as anomalous soilmoisture content, also influence the occurrence of extreme temperatures. Close

• 3. [Article] The effect of soil temperature and soil moisture stress on S-urea mineralization and ryegrass yield

  A growth chamber experiment was conducted to determine the rate of S-urea mineralization and effect of S-urea on the yield of ryegrass (Lolium multiflorum) grown in Steiwer soil as influenced by soil temperature ...

  Citation × Citation Citation Abstract Copy Title: The effect of soil temperature and soil moisture stress on S-urea mineralization and ryegrass yield Author: Akratanakul, Wanee A growth chamber experiment was conducted to determine the rate of S-urea mineralization and effect of S-urea on the yield of ryegrass (Lolium multiflorum) grown in Steiwer soil as influenced by soil temperature (60, 75, and 90° F) and soil moisture stress (0. 10, 0.35, and 2.50 bars). Plant yield, nitrogen and sulphur uptake and amount of S-urea mineralized were studied. The optimum conditions for ryegrass growth appeared to vary due to the interaction between soil temperature and moisture status. Increasing root temperature indicated a higher soil moisture content was required for optimum ryegrass growth. High soil temperature and low soil water suction decreased the percent plant nitrogen in 31-day old seedlings. Ryegrass N-uptake was highest in the 31-day old seedlings maintained at 0.35 bar soil water suction and a root temperature of 75° F. Optimum conditions for S-urea mineralization to available NH₄ + NO₃ occurred at a soil temperature of 90° F and moisture stress of 0.10 bar. Moreover, the mineralization exceeded 60 percent of the S-urea added in only 9 days after application under these warm moist soil conditions. The amount of nitrogen mineralized was directly related to plant growth. While SO₄-S mineralized from S-urea varied directly with soil temperature and moisture content unlike nitrogen mineralization no interaction between these two factors was observed. Sulphur and nitrogen status in plants proved to have a close relationship. At low soil temperature and high soil moisture content luxury consumption of sulphate by ryegrass likely occurred. Title: The effect of soil temperature and soil moisture stress on S-urea mineralization and ryegrass yield Author: Akratanakul, Wanee A growth chamber experiment was conducted to determine the rate of S-urea mineralization and effect of S-urea on the yield of ryegrass (Lolium multiflorum) grown in Steiwer soil as influenced by soil temperature (60, 75, and 90° F) and soil moisture stress (0. 10, 0.35, and 2.50 bars). Plant yield, nitrogen and sulphur uptake and amount of S-urea mineralized were studied. The optimum conditions for ryegrass growth appeared to vary due to the interaction between soil temperature and moisture status. Increasing root temperature indicated a higher soil moisture content was required for optimum ryegrass growth. High soil temperature and low soil water suction decreased the percent plant nitrogen in 31-day old seedlings. Ryegrass N-uptake was highest in the 31-day old seedlings maintained at 0.35 bar soil water suction and a root temperature of 75° F. Optimum conditions for S-urea mineralization to available NH₄ + NO₃ occurred at a soil temperature of 90° F and moisture stress of 0.10 bar. Moreover, the mineralization exceeded 60 percent of the S-urea added in only 9 days after application under these warm moist soil conditions. The amount of nitrogen mineralized was directly related to plant growth. While SO₄-S mineralized from S-urea varied directly with soil temperature and moisture content unlike nitrogen mineralization no interaction between these two factors was observed. Sulphur and nitrogen status in plants proved to have a close relationship. At low soil temperature and high soil moisture content luxury consumption of sulphate by ryegrass likely occurred. Close

• 4. [Article] Nitrogen uptake by wheat (Triticum aestivum VILL., Host) as a function of root temperature and plant water stress

  The effect of soil temperature and plant water stress on nitrogen uptake, growth rate and transpiration rate of wheat (Triticum aestivum VILL. , Host) seedlings was studied. A special apparatus for the ...

  Citation × Citation Citation Abstract Copy Title: Nitrogen uptake by wheat (Triticum aestivum VILL., Host) as a function of root temperature and plant water stress Author: Sepaskhah, Ali Reza The effect of soil temperature and plant water stress on nitrogen uptake, growth rate and transpiration rate of wheat (Triticum aestivum VILL. , Host) seedlings was studied. A special apparatus for the control of plant water stress and root temperature was used. Leaf area was measured by the air flow planimeter technique. Dry matter weight was determined with a Mettler balance after oven drying of the plant material. Nitrogen concentration in shoots and roots was determined by the micro-Kjeldahl procedure. The transpiration rate was obtained with a constant-water level graduated burette device operating on the principle of a Mariotte bottle. Growth rate of shoots and roots was slowest at the extreme temperatures with a maximum rate of growth occurring around a root temperature of 24° C. The growth rate was higher at a plant water stress of 0.35 bar than at a plant water stress of 2.5 bars. Rates of transpiration decreased steadily with increasing plant water stress. The increase of transpiration rate with root temperature increase was attributed to the change of water viscosity and increased root cell membrane permeability. The nitrogen content of roots and shoots increased as root temperatures increased from 10.0 to 25.0°C, while there was no significant difference at plant water stresses of 0.35 and 2.5 bars. The increase in rate of nitrogen uptake was found to be proportional to the increase in rate of root growth. The same proportionality described a decrease in the rate of nitrogen uptake as a result of decreased rate of root growth. The rate of leaf area increase was found to be related to the rate of dry matter increase of the shoot. This relation was the same at all root temperatures and plant water stresses considered. Title: Nitrogen uptake by wheat (Triticum aestivum VILL., Host) as a function of root temperature and plant water stress Author: Sepaskhah, Ali Reza The effect of soil temperature and plant water stress on nitrogen uptake, growth rate and transpiration rate of wheat (Triticum aestivum VILL. , Host) seedlings was studied. A special apparatus for the control of plant water stress and root temperature was used. Leaf area was measured by the air flow planimeter technique. Dry matter weight was determined with a Mettler balance after oven drying of the plant material. Nitrogen concentration in shoots and roots was determined by the micro-Kjeldahl procedure. The transpiration rate was obtained with a constant-water level graduated burette device operating on the principle of a Mariotte bottle. Growth rate of shoots and roots was slowest at the extreme temperatures with a maximum rate of growth occurring around a root temperature of 24° C. The growth rate was higher at a plant water stress of 0.35 bar than at a plant water stress of 2.5 bars. Rates of transpiration decreased steadily with increasing plant water stress. The increase of transpiration rate with root temperature increase was attributed to the change of water viscosity and increased root cell membrane permeability. The nitrogen content of roots and shoots increased as root temperatures increased from 10.0 to 25.0°C, while there was no significant difference at plant water stresses of 0.35 and 2.5 bars. The increase in rate of nitrogen uptake was found to be proportional to the increase in rate of root growth. The same proportionality described a decrease in the rate of nitrogen uptake as a result of decreased rate of root growth. The rate of leaf area increase was found to be related to the rate of dry matter increase of the shoot. This relation was the same at all root temperatures and plant water stresses considered. Close

• 5. [Article] Rainfall seasonality and an ecohydrological feedback offset the potential impact of climate warming on evapotranspiration and groundwater recharge

  This is the publisher’s final pdf. The published article is copyrighted by the American Geophysical Union and can be found at: http://onlinelibrary.wiley.com/journal/10.1002/%28ISSN%291944-7973.

  Citation × Citation Citation Abstract Copy Title: Rainfall seasonality and an ecohydrological feedback offset the potential impact of climate warming on evapotranspiration and groundwater recharge Author: McDonnell, Jeffrey J., Pangle, Luke A., Gregg, Jillian W. This is the publisher’s final pdf. The published article is copyrighted by the American Geophysical Union and can be found at: http://onlinelibrary.wiley.com/journal/10.1002/%28ISSN%291944-7973. Title: Rainfall seasonality and an ecohydrological feedback offset the potential impact of climate warming on evapotranspiration and groundwater recharge Author: McDonnell, Jeffrey J., Pangle, Luke A., Gregg, Jillian W. This is the publisher’s final pdf. The published article is copyrighted by the American Geophysical Union and can be found at: http://onlinelibrary.wiley.com/journal/10.1002/%28ISSN%291944-7973. Close

• 6. [Article] Prediction of Soil Layer R-Value Dependence on Moisture Content

  This study focuses on how green roof thermal performance is affected by the soil moisture in summer condition. It aims to determine whether moist soil is a better insulator during the summer months than ...

  Citation × Citation Citation Abstract Copy Title: Prediction of Soil Layer R-Value Dependence on Moisture Content Author: Liu, Ziyang Year: 2011 This study focuses on how green roof thermal performance is affected by the soil moisture in summer condition. It aims to determine whether moist soil is a better insulator during the summer months than dry soil. A soil model is developed to predict simultaneous conduction, convection, and surface evaporation for a layer of moist soil representing a green roof. It used to analyze evaporation process and its affect on the soil resistance. The model considers only bare soil without vegetation on the roof. The model predicts the soil surface temperature as it is affected by soil moisture content, which can then be used to calculate heat transfer through the soil layer. An experimental dry out test was conducted to measure the soil moisture and soil temperature histories. Comparison of the predicted and measured sol surface temperature shows that the model reasonably captures the actual behavior. The evaporative cooling effectively reduces the soil surface temperature and heat flux in moist soil and can be used as an effective way to insulate the roof. Title: Prediction of Soil Layer R-Value Dependence on Moisture Content Author: Liu, Ziyang Year: 2011 This study focuses on how green roof thermal performance is affected by the soil moisture in summer condition. It aims to determine whether moist soil is a better insulator during the summer months than dry soil. A soil model is developed to predict simultaneous conduction, convection, and surface evaporation for a layer of moist soil representing a green roof. It used to analyze evaporation process and its affect on the soil resistance. The model considers only bare soil without vegetation on the roof. The model predicts the soil surface temperature as it is affected by soil moisture content, which can then be used to calculate heat transfer through the soil layer. An experimental dry out test was conducted to measure the soil moisture and soil temperature histories. Comparison of the predicted and measured sol surface temperature shows that the model reasonably captures the actual behavior. The evaporative cooling effectively reduces the soil surface temperature and heat flux in moist soil and can be used as an effective way to insulate the roof. Close

• 7. [Article] Leaf stress in corn, beans, and tomatoes under optimum soil moisture conditions

  Under adverse soil moisture conditions a critical water stress or water potential develops in the plant and productivity is reduced, or in extreme cases, terminated. Research to determine the soil moisture ...

  Citation × Citation Citation Abstract Copy Title: Leaf stress in corn, beans, and tomatoes under optimum soil moisture conditions Author: Nilsson, Colin Wayne Under adverse soil moisture conditions a critical water stress or water potential develops in the plant and productivity is reduced, or in extreme cases, terminated. Research to determine the soil moisture status for maximum production of specific crops has been conducted for decades. The results have done much to increase the productivity of the irrigable acreage. Yet, even with irrigation water available, under adverse atmospheric conditions water stress will still develop in the agronomic crops. The degree of stress that develops and the duration, however, is generally unknown. Limited research in controlled environments has been conducted, but actual plant water stress levels under field conditions have not been studied. The purpose of this research was to determine the levels of leaf water potential (water stress) that develop in specific horticultural crops under conditions of optimum soil moisture. Further studies were made to relate the leaf water potential to atmospheric parameters and leaf temperature. Three horticultural crops, sweet corn (Zea mays), tomatoes (Lycopersicon esculentum), and bush beans (Phaseolus vulgaris) were grown on a Cloquato silt loam soil under high soil moisture conditions and exposed to the natural atmospheric conditions common to the Willamette Valley of Oregon. A pressure chamber was used to monitor, in the field, the leaf water potential that developed during each of five days throughout the summer months. An infrared radiometer was utilized to monitor the temperatures of the leaves during the same periods. Sweet corn consistently developed the highest leaf water potential, reaching as high as 13.0 atmospheres. The tomatoes and beans developed leaf water potentials above 10.0 atmospheres. On all five days the corn plants developed leaf water potentials above the critical 8.0 to 9.0 atmospheres suction levels reported in the literature by other investigators. On four of the five days, the Ψl of the tomato and bean plants equalled or exceeded these critical levels although not to the same degree as the corn plants. The length of time that the leaf water potential remained above 8.0 atmospheres suction varied, but lasted up to 9 1/4 hours in the corn and up to 7 hours in the beans and tomatoes. During these periods photosynthesis formation, soluble nitrogenous and phosphorous compounds formation, RNA accumulation, carbohydrate synthesis, and cell growth are reportedly impaired, limiting productivity. Leaf temperature under these stress conditions followed closely the same general trends as ambient air temperature. High levels of leaf water potential did not necessarily cause the temperature of the leaf to rise significantly. Leaf temperatures exceeded ambient air temperature by a maximum of 3.8 °C, but were generally in close agreement with or below ambient air temperature. The results of this study indicated that many horticulture crops may be limited in productivity by fairly frequent periods of critical leaf water potential even though soil moisture levels are adequate. On none of the five days studies were made did the atmospheric conditions exceed those normally experienced in the Willamette Valley. The maximum air temperature was 32.5 °C and the maximum solar radiation level was 1.16 cal/cm²/min. Further investigation is required to determine the effects on yield, quantity and quality,of detrimental plant water potentials and to develop means of alleviating Ψl before it reaches detrimental levels. Further investigation could also lead to a new outlook in plant breeding. Title: Leaf stress in corn, beans, and tomatoes under optimum soil moisture conditions Author: Nilsson, Colin Wayne Under adverse soil moisture conditions a critical water stress or water potential develops in the plant and productivity is reduced, or in extreme cases, terminated. Research to determine the soil moisture status for maximum production of specific crops has been conducted for decades. The results have done much to increase the productivity of the irrigable acreage. Yet, even with irrigation water available, under adverse atmospheric conditions water stress will still develop in the agronomic crops. The degree of stress that develops and the duration, however, is generally unknown. Limited research in controlled environments has been conducted, but actual plant water stress levels under field conditions have not been studied. The purpose of this research was to determine the levels of leaf water potential (water stress) that develop in specific horticultural crops under conditions of optimum soil moisture. Further studies were made to relate the leaf water potential to atmospheric parameters and leaf temperature. Three horticultural crops, sweet corn (Zea mays), tomatoes (Lycopersicon esculentum), and bush beans (Phaseolus vulgaris) were grown on a Cloquato silt loam soil under high soil moisture conditions and exposed to the natural atmospheric conditions common to the Willamette Valley of Oregon. A pressure chamber was used to monitor, in the field, the leaf water potential that developed during each of five days throughout the summer months. An infrared radiometer was utilized to monitor the temperatures of the leaves during the same periods. Sweet corn consistently developed the highest leaf water potential, reaching as high as 13.0 atmospheres. The tomatoes and beans developed leaf water potentials above 10.0 atmospheres. On all five days the corn plants developed leaf water potentials above the critical 8.0 to 9.0 atmospheres suction levels reported in the literature by other investigators. On four of the five days, the Ψl of the tomato and bean plants equalled or exceeded these critical levels although not to the same degree as the corn plants. The length of time that the leaf water potential remained above 8.0 atmospheres suction varied, but lasted up to 9 1/4 hours in the corn and up to 7 hours in the beans and tomatoes. During these periods photosynthesis formation, soluble nitrogenous and phosphorous compounds formation, RNA accumulation, carbohydrate synthesis, and cell growth are reportedly impaired, limiting productivity. Leaf temperature under these stress conditions followed closely the same general trends as ambient air temperature. High levels of leaf water potential did not necessarily cause the temperature of the leaf to rise significantly. Leaf temperatures exceeded ambient air temperature by a maximum of 3.8 °C, but were generally in close agreement with or below ambient air temperature. The results of this study indicated that many horticulture crops may be limited in productivity by fairly frequent periods of critical leaf water potential even though soil moisture levels are adequate. On none of the five days studies were made did the atmospheric conditions exceed those normally experienced in the Willamette Valley. The maximum air temperature was 32.5 °C and the maximum solar radiation level was 1.16 cal/cm²/min. Further investigation is required to determine the effects on yield, quantity and quality,of detrimental plant water potentials and to develop means of alleviating Ψl before it reaches detrimental levels. Further investigation could also lead to a new outlook in plant breeding. Close

• 8. [Article] Climate Warming, Soil Moisture Dynamics, and Water Budget Partitioning: Experimental Results from a Willamette Valley Ecosystem

  Presented at The Oregon Water Conference, May 24-25, 2011, Corvallis, OR.

  Citation × Citation Citation Abstract Copy Title: Climate Warming, Soil Moisture Dynamics, and Water Budget Partitioning: Experimental Results from a Willamette Valley Ecosystem Author: McDonnell, Jeffrey, Gregg, Jillian, Pangle, Luke Presented at The Oregon Water Conference, May 24-25, 2011, Corvallis, OR. Title: Climate Warming, Soil Moisture Dynamics, and Water Budget Partitioning: Experimental Results from a Willamette Valley Ecosystem Author: McDonnell, Jeffrey, Gregg, Jillian, Pangle, Luke Presented at The Oregon Water Conference, May 24-25, 2011, Corvallis, OR. Close

• 9. [Article] Twentieth-Century Trends in Runoff, Evapotranspiration, and Soil Moisture in the Western United States

  A physically based hydrology model is used to produce time series for the period 1916–2003 of evapotranspiration (ET), runoff, and soil moisture (SM) over the western United States from which long-term ...

  Citation × Citation Citation Abstract Copy Title: Twentieth-Century Trends in Runoff, Evapotranspiration, and Soil Moisture in the Western United States Author: Clark, Martyn P., Lettenmaier, Dennis P., Mote, Philip W., Hamlet, Alan F. A physically based hydrology model is used to produce time series for the period 1916–2003 of evapotranspiration (ET), runoff, and soil moisture (SM) over the western United States from which long-term trends are evaluated. The results show that trends in ET in spring and summer are determined primarily by trends in precipitation and snowmelt that determine water availability. From April to June, ET trends are mostly positive due primarily to earlier snowmelt and earlier emergence of snow-free ground, and secondarily to increasing trends in spring precipitation. From July to September trends in ET are more strongly influenced by precipitation trends, with the exception of areas (most notably California) that receive little summer precipitation and have experienced large changes in snowmelt timing. Trends in the seasonal timing of ET are modest, but during the period 1947–2003 when temperature trends are large, they reflect a shift of ET from midsummer to early summer and late spring. As in other studies, it is found that runoff is occurring earlier in spring, a trend that is related primarily to increasing temperature, and is most apparent during 1947–2003. Trends in the annual runoff ratio, a variable critical to western water management, are determined primarily by trends in cool season precipitation, rather than changes in the timing of runoff or ET. It was found that the signature of temperature-related trends in runoff and SM is strongly keyed to mean midwinter [December–February (DJF)] temperatures. Areas with warmer winter temperatures show increasing trends in the runoff fraction as early as February, and colder areas as late as June. Trends toward earlier spring SM recharge are apparent and increasing trends in SM on 1 April are evident over much of the region. The 1 July SM trends are less affected by snowmelt changes and are controlled more by precipitation trends. Title: Twentieth-Century Trends in Runoff, Evapotranspiration, and Soil Moisture in the Western United States Author: Clark, Martyn P., Lettenmaier, Dennis P., Mote, Philip W., Hamlet, Alan F. A physically based hydrology model is used to produce time series for the period 1916–2003 of evapotranspiration (ET), runoff, and soil moisture (SM) over the western United States from which long-term trends are evaluated. The results show that trends in ET in spring and summer are determined primarily by trends in precipitation and snowmelt that determine water availability. From April to June, ET trends are mostly positive due primarily to earlier snowmelt and earlier emergence of snow-free ground, and secondarily to increasing trends in spring precipitation. From July to September trends in ET are more strongly influenced by precipitation trends, with the exception of areas (most notably California) that receive little summer precipitation and have experienced large changes in snowmelt timing. Trends in the seasonal timing of ET are modest, but during the period 1947–2003 when temperature trends are large, they reflect a shift of ET from midsummer to early summer and late spring. As in other studies, it is found that runoff is occurring earlier in spring, a trend that is related primarily to increasing temperature, and is most apparent during 1947–2003. Trends in the annual runoff ratio, a variable critical to western water management, are determined primarily by trends in cool season precipitation, rather than changes in the timing of runoff or ET. It was found that the signature of temperature-related trends in runoff and SM is strongly keyed to mean midwinter [December–February (DJF)] temperatures. Areas with warmer winter temperatures show increasing trends in the runoff fraction as early as February, and colder areas as late as June. Trends toward earlier spring SM recharge are apparent and increasing trends in SM on 1 April are evident over much of the region. The 1 July SM trends are less affected by snowmelt changes and are controlled more by precipitation trends. Close

• 10. [Article] Feasibility of soil moisture monitoring with heated fiber optics

  This is the publisher’s final pdf. The published article is copyrighted by American Geophysical Union and can be found at: http://sites.agu.org/

  Citation × Citation Citation Abstract Copy Title: Feasibility of soil moisture monitoring with heated fiber optics Author: Gregory, Christopher, van de Giesen, Nick, Selker, John S., Cuenca, Richard, Tufillaro, Nick, English, Marshal, Tyler, Scott, Gil‐Rodriguez, Maria, Sayde, Chadi This is the publisher’s final pdf. The published article is copyrighted by American Geophysical Union and can be found at: http://sites.agu.org/ Title: Feasibility of soil moisture monitoring with heated fiber optics Author: Gregory, Christopher, van de Giesen, Nick, Selker, John S., Cuenca, Richard, Tufillaro, Nick, English, Marshal, Tyler, Scott, Gil‐Rodriguez, Maria, Sayde, Chadi This is the publisher’s final pdf. The published article is copyrighted by American Geophysical Union and can be found at: http://sites.agu.org/ Close