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• 21. [Article] Impact of an Elevated Temperature Environment on Sn-Ag-Cu Interconnect Board Level High-G Mechanical Shock Performance

  The mechanical stability of Sn-Ag-Cu interconnects with low and high silver content against mechanical shock at room and elevated temperatures was investigated. With a heating element-embedded printed ...

  Citation × Citation Citation Abstract Copy Title: Impact of an Elevated Temperature Environment on Sn-Ag-Cu Interconnect Board Level High-G Mechanical Shock Performance Author: Lee, Tae-Kyu, Chen, Zhiqiang, Baty, Greg, Bieler, Thomas R., Kim, Choong-Un Year: 2016 The mechanical stability of Sn-Ag-Cu interconnects with low and high silver content against mechanical shock at room and elevated temperatures was investigated. With a heating element-embedded printed circuit board design, a test temperature from room temperature to 80°C was established. High impact shock tests were applied to isothermally pre-conditioned ball-grid array interconnects. Under cyclic shock testing, degradation and improved shock performances were identified associated with test temperature variation and non-solder mask defined and solder-mask defined pad design configuration differences. Different crack propagation paths were observed, induced by the effect of the elevated temperature test conditions and isothermal aging pre-conditions. Title: Impact of an Elevated Temperature Environment on Sn-Ag-Cu Interconnect Board Level High-G Mechanical Shock Performance Author: Lee, Tae-Kyu, Chen, Zhiqiang, Baty, Greg, Bieler, Thomas R., Kim, Choong-Un Year: 2016 The mechanical stability of Sn-Ag-Cu interconnects with low and high silver content against mechanical shock at room and elevated temperatures was investigated. With a heating element-embedded printed circuit board design, a test temperature from room temperature to 80°C was established. High impact shock tests were applied to isothermally pre-conditioned ball-grid array interconnects. Under cyclic shock testing, degradation and improved shock performances were identified associated with test temperature variation and non-solder mask defined and solder-mask defined pad design configuration differences. Different crack propagation paths were observed, induced by the effect of the elevated temperature test conditions and isothermal aging pre-conditions. Close

• 22. [Article] Short-tailed temperature distributions over North America and Implications for Future Changes in Extremes

  Some regions of North America exhibit nonnormal temperature distributions. Shorter-than-Gaussian warm tails are a special subset of these cases, with potentially meaningful implications for future changes ...

  Citation × Citation Citation Abstract Copy Title: Short-tailed temperature distributions over North America and Implications for Future Changes in Extremes Author: Loikith, Paul C., Neelin, J. David Year: 2015 Some regions of North America exhibit nonnormal temperature distributions. Shorter-than-Gaussian warm tails are a special subset of these cases, with potentially meaningful implications for future changes in extreme warm temperatures under anthropogenic global warming. Locations exhibiting shorter-than-Gaussian warm tails would experience a greater increase in extreme warm temperature exceedances than a location with a Gaussian or long warm-side tail under a simple uniform warm shift in the distribution. Here we identify regions exhibiting such behavior over North America and demonstrate the effect of a simple warm shift on changes in extreme warm temperature exceedances. Some locations exceed the 95th percentile of the original distribution by greater than 40% of the time after this uniform shift. While the manner in which distributions change under global warming may be more complex than a simple shift, these results provide an observational baseline for climate model evaluation. Title: Short-tailed temperature distributions over North America and Implications for Future Changes in Extremes Author: Loikith, Paul C., Neelin, J. David Year: 2015 Some regions of North America exhibit nonnormal temperature distributions. Shorter-than-Gaussian warm tails are a special subset of these cases, with potentially meaningful implications for future changes in extreme warm temperatures under anthropogenic global warming. Locations exhibiting shorter-than-Gaussian warm tails would experience a greater increase in extreme warm temperature exceedances than a location with a Gaussian or long warm-side tail under a simple uniform warm shift in the distribution. Here we identify regions exhibiting such behavior over North America and demonstrate the effect of a simple warm shift on changes in extreme warm temperature exceedances. Some locations exceed the 95th percentile of the original distribution by greater than 40% of the time after this uniform shift. While the manner in which distributions change under global warming may be more complex than a simple shift, these results provide an observational baseline for climate model evaluation. Close

• 23. [Article] Surface-enhanced Raman scattering at elevated temperatures

  The effect on surface-enhanced Raman scattering due to the increase in temperature of the metallic substrate is studied via a simple model for physisorbed molecules. Surface roughness is represented by ...

  Citation × Citation Citation Abstract Copy Title: Surface-enhanced Raman scattering at elevated temperatures Author: Leung, P.T., Hider, M. H., Sánchez, Erik J. Year: 1996 The effect on surface-enhanced Raman scattering due to the increase in temperature of the metallic substrate is studied via a simple model for physisorbed molecules. Surface roughness is represented by a spherical or spheroidal island, and the temperature effects on the surface plasmon are accounted for via a slightly modified Ujihara model. It is found that the enhancement ratio in general decreases as substrate temperature increases. For noble metals like silver, this temperature effect is particularly pronounced at scattering frequencies close to that of the surface-plasmon resonance; and for frequencies well below the surface plasmon frequency, the enhancement ratio is relatively insensitive to the change of substrate temperature. A tentative explanation is provided for our modeling results, and the implications from these results are discussed. Title: Surface-enhanced Raman scattering at elevated temperatures Author: Leung, P.T., Hider, M. H., Sánchez, Erik J. Year: 1996 The effect on surface-enhanced Raman scattering due to the increase in temperature of the metallic substrate is studied via a simple model for physisorbed molecules. Surface roughness is represented by a spherical or spheroidal island, and the temperature effects on the surface plasmon are accounted for via a slightly modified Ujihara model. It is found that the enhancement ratio in general decreases as substrate temperature increases. For noble metals like silver, this temperature effect is particularly pronounced at scattering frequencies close to that of the surface-plasmon resonance; and for frequencies well below the surface plasmon frequency, the enhancement ratio is relatively insensitive to the change of substrate temperature. A tentative explanation is provided for our modeling results, and the implications from these results are discussed. Close

• 24. [Article] Computation of dark frames in digital imagers

  Dark current is caused by electrons that are thermally exited into the conduction band. These electrons are collected by the well of the CCD and add a false signal to the chip. We will present an algorithm ...

  Citation × Citation Citation Abstract Copy Title: Computation of dark frames in digital imagers Author: Widenhorn, Ralf, Rest, Armin, Blouke, Morley M., Berry, Richard L., Bodegom, Erik Year: 2007 Dark current is caused by electrons that are thermally exited into the conduction band. These electrons are collected by the well of the CCD and add a false signal to the chip. We will present an algorithm that automatically corrects for dark current. It uses a calibration protocol to characterize the image sensor for different temperatures. For a given exposure time, the dark current of every pixel is characteristic of a specific temperature. The dark current of every pixel can therefore be used as an indicator of the temperature. Hot pixels have the highest signal-to-noise ratio and are the best temperature sensors. We use the dark current of a several hundred hot pixels to sense the chip temperature and predict the dark current of all pixels on the chip. Dark current computation is not a new concept, but our approach is unique. Some advantages of our method include applicability for poorly temperature-controlled camera systems and the possibility of ex post facto dark current correction. Title: Computation of dark frames in digital imagers Author: Widenhorn, Ralf, Rest, Armin, Blouke, Morley M., Berry, Richard L., Bodegom, Erik Year: 2007 Dark current is caused by electrons that are thermally exited into the conduction band. These electrons are collected by the well of the CCD and add a false signal to the chip. We will present an algorithm that automatically corrects for dark current. It uses a calibration protocol to characterize the image sensor for different temperatures. For a given exposure time, the dark current of every pixel is characteristic of a specific temperature. The dark current of every pixel can therefore be used as an indicator of the temperature. Hot pixels have the highest signal-to-noise ratio and are the best temperature sensors. We use the dark current of a several hundred hot pixels to sense the chip temperature and predict the dark current of all pixels on the chip. Dark current computation is not a new concept, but our approach is unique. Some advantages of our method include applicability for poorly temperature-controlled camera systems and the possibility of ex post facto dark current correction. Close

• 25. [Article] Temperature Dependent Transcription Initiation in Archaea: Interplay between Transcription Factor B and Promoter Sequence

  In Pyrococcus furiosus (Pfu), a hyperthermophile archaeon, two transcription factor Bs, TFB1 and TFB2 are encoded in the genomic DNA. TFB1 is the primary TFB in Pfu, and is homologous to transcription ...

  Citation × Citation Citation Abstract Copy Title: Temperature Dependent Transcription Initiation in Archaea: Interplay between Transcription Factor B and Promoter Sequence Author: Wu, Ming-Hsiao Year: 2014 In Pyrococcus furiosus (Pfu), a hyperthermophile archaeon, two transcription factor Bs, TFB1 and TFB2 are encoded in the genomic DNA. TFB1 is the primary TFB in Pfu, and is homologous to transcription factor IIB (TFIIB) in eukaryotes. TFB2 is proposed to be a secondary TFB that is compared to TFB1, TFB2 lacks the conserved B-finger / B-reader / B-linker regions which assist RNA polymerase in transcription start site selection and promoter opening functions respectively. P. furiosus, like all Archaea, encodes a single transcription factor E (TFE), that is homologous to the N-terminus of transcription factor II E (TFIIE) α subunit in eukaryotes. TFE stabilizes the transcription bubble when present, although it is not required for in vitro transcription. In this study, in vitro transcription is used to reveal how TFB2 responds to different temperature (65 °C, 70 °C, 75 °C, 80 °C, and 85 °C) at promoters for three different kinds of gene: non-temperature responsive, heat-shock induced, and cold-shock induced in the absence or presence of TFE. The activity of transcription complexes formed by TFB2 is always lower than by TFB1 in all temperatures and promoters. However, with heat-shock gene promoters, the activity of transcription complexes formed by TFB2 increases more than those formed with TFB1 with increasing temperatures. The temperature-dependent activities of TFB1 and TFB2 are similar with the non-temperature responsive gene promoter. With the cold-shock gene promoter, the activity of transcription complexes formed by both TFB1 and TFB2 has the highest activity in lower temperatures. When TFE is present, the activity of transcription complexes formed by TFB2 is enhanced with heat-shock gene promoters particularly at lower temperatures, and makes TFB2 behave more similarly to TFB1. With the non-temperature responsive gene promoter, TFB2 still behaves similarly to TFB1 when TFE is present. However, with the cold-shock gene promoter, most of the activity of transcription complexes formed by TFB1 and TFB2 remain the same, but only the activity of TFB1 decreases at 75 °C. The results suggest that TFB2 may play a role in heat-shock response through its increased sensitivity to temperature, and that TFE can modulate this temperature response. Title: Temperature Dependent Transcription Initiation in Archaea: Interplay between Transcription Factor B and Promoter Sequence Author: Wu, Ming-Hsiao Year: 2014 In Pyrococcus furiosus (Pfu), a hyperthermophile archaeon, two transcription factor Bs, TFB1 and TFB2 are encoded in the genomic DNA. TFB1 is the primary TFB in Pfu, and is homologous to transcription factor IIB (TFIIB) in eukaryotes. TFB2 is proposed to be a secondary TFB that is compared to TFB1, TFB2 lacks the conserved B-finger / B-reader / B-linker regions which assist RNA polymerase in transcription start site selection and promoter opening functions respectively. P. furiosus, like all Archaea, encodes a single transcription factor E (TFE), that is homologous to the N-terminus of transcription factor II E (TFIIE) α subunit in eukaryotes. TFE stabilizes the transcription bubble when present, although it is not required for in vitro transcription. In this study, in vitro transcription is used to reveal how TFB2 responds to different temperature (65 °C, 70 °C, 75 °C, 80 °C, and 85 °C) at promoters for three different kinds of gene: non-temperature responsive, heat-shock induced, and cold-shock induced in the absence or presence of TFE. The activity of transcription complexes formed by TFB2 is always lower than by TFB1 in all temperatures and promoters. However, with heat-shock gene promoters, the activity of transcription complexes formed by TFB2 increases more than those formed with TFB1 with increasing temperatures. The temperature-dependent activities of TFB1 and TFB2 are similar with the non-temperature responsive gene promoter. With the cold-shock gene promoter, the activity of transcription complexes formed by both TFB1 and TFB2 has the highest activity in lower temperatures. When TFE is present, the activity of transcription complexes formed by TFB2 is enhanced with heat-shock gene promoters particularly at lower temperatures, and makes TFB2 behave more similarly to TFB1. With the non-temperature responsive gene promoter, TFB2 still behaves similarly to TFB1 when TFE is present. However, with the cold-shock gene promoter, most of the activity of transcription complexes formed by TFB1 and TFB2 remain the same, but only the activity of TFB1 decreases at 75 °C. The results suggest that TFB2 may play a role in heat-shock response through its increased sensitivity to temperature, and that TFE can modulate this temperature response. Close

• 26. [Article] The Influence of Ambient Temperature on Green Roof R-values

  Green roofs can be an effective and appealing way to increase the energy efficiency of buildings by providing active insulation. As plants in the green roof transpire, there is a reduction in heat flux ...

  Citation × Citation Citation Abstract Copy Title: The Influence of Ambient Temperature on Green Roof R-values Author: Cox, Bryce Kevin Year: 2010 Green roofs can be an effective and appealing way to increase the energy efficiency of buildings by providing active insulation. As plants in the green roof transpire, there is a reduction in heat flux that is conducted through the green roof. The R-value, or thermal resistance, of a green roof is an effective measurement of thermal performance because it can be easily included in building energy calculations applicable to many different buildings and situations. The purpose of this study was to determine if an increase in ambient temperature would cause an increase in the R-value of green roofs. Test trays containing green roof materials were tested in a low speed wind tunnel equipped to determine the R-value of the trays. Three different plant species were tested in this study, ryegrass (Lolium perenne), sedum (Sedum hispanicum), and vinca (Vinca minor). For each test in this study the relative humidity was maintained at 45% and the soil was saturated with water. The trays were tested at four different ambient temperatures, ranging from room temperature to 120ºF. The resulting R-values for sedum ranged from 1.37 to 3.28 ft²h°F/BTU, for ryegrass the R-values ranged from 2.15 to 3.62 ft²h°F/BTU, and for vinca the R-values ranged from 3.15 to 5.19 ft²h°F/BTU. The average R-value for all the tests in this study was 3.20 ft²h°F/BTU. The results showed an increase in R-value with increasing temperature. Applying an ANOVA analysis to the data, the relationship between temperature and R-value for all three plant species was found to be statistically significant. Title: The Influence of Ambient Temperature on Green Roof R-values Author: Cox, Bryce Kevin Year: 2010 Green roofs can be an effective and appealing way to increase the energy efficiency of buildings by providing active insulation. As plants in the green roof transpire, there is a reduction in heat flux that is conducted through the green roof. The R-value, or thermal resistance, of a green roof is an effective measurement of thermal performance because it can be easily included in building energy calculations applicable to many different buildings and situations. The purpose of this study was to determine if an increase in ambient temperature would cause an increase in the R-value of green roofs. Test trays containing green roof materials were tested in a low speed wind tunnel equipped to determine the R-value of the trays. Three different plant species were tested in this study, ryegrass (Lolium perenne), sedum (Sedum hispanicum), and vinca (Vinca minor). For each test in this study the relative humidity was maintained at 45% and the soil was saturated with water. The trays were tested at four different ambient temperatures, ranging from room temperature to 120ºF. The resulting R-values for sedum ranged from 1.37 to 3.28 ft²h°F/BTU, for ryegrass the R-values ranged from 2.15 to 3.62 ft²h°F/BTU, and for vinca the R-values ranged from 3.15 to 5.19 ft²h°F/BTU. The average R-value for all the tests in this study was 3.20 ft²h°F/BTU. The results showed an increase in R-value with increasing temperature. Applying an ANOVA analysis to the data, the relationship between temperature and R-value for all three plant species was found to be statistically significant. Close

• 27. [Article] Effect of ethanol on thermoregulation in the goldfish, Carassius auratus

  In an attempt to elucidate the mechanism by which ethanol affects vertebrate thermoregulation, the effect of ethanol on temperature selection was studied in the goldfish, Carassius auratus. Ethanol was ...

  Citation × Citation Citation Abstract Copy Title: Effect of ethanol on thermoregulation in the goldfish, Carassius auratus Author: O'Connor, Candace Sharon Year: 1986 In an attempt to elucidate the mechanism by which ethanol affects vertebrate thermoregulation, the effect of ethanol on temperature selection was studied in the goldfish, Carassius auratus. Ethanol was administered to 10 to 15 g fish by mixing it in the water of a temperature gradient. The dose response curve was very steep between 0.5% (v/v) ethanol (no response) and 0.7% (significant lowering of selected temperature in treated fish). Fish were exposed to concentrations of ethanol as high as 1.7%, at which concentration most experimental fish lost their ability to swim upright in the water. At concentrations higher than 0.7%, the magnitude of the effect did not increase with increasing concentration of ethanol; treated animals continued to select temperatures about 2 C below temperatures selected by controls. Experiments alternating exposure to 1.0% ethanol and water showed that the rate of onset and disappearance of the ethanol effect was rapid (within 10 min). Other experiments exposing fish to 1.0% ethanol for up to 3 hr showed that the effect remained stable for this period of time. The thermoregulatory responses of fish are behavioral, and therefore relatively easy to observe and quantify. Ethanol produces a prompt, stable and reproducible depression of selected temperature in the goldfish. Because the temperature at which fish regulate is controlled by a central nervous system set point and not altered by effects on peripheral effector systems, it appears that ethanol may cause hypothermia in goldfish by directly acting to lower the set point. Title: Effect of ethanol on thermoregulation in the goldfish, Carassius auratus Author: O'Connor, Candace Sharon Year: 1986 In an attempt to elucidate the mechanism by which ethanol affects vertebrate thermoregulation, the effect of ethanol on temperature selection was studied in the goldfish, Carassius auratus. Ethanol was administered to 10 to 15 g fish by mixing it in the water of a temperature gradient. The dose response curve was very steep between 0.5% (v/v) ethanol (no response) and 0.7% (significant lowering of selected temperature in treated fish). Fish were exposed to concentrations of ethanol as high as 1.7%, at which concentration most experimental fish lost their ability to swim upright in the water. At concentrations higher than 0.7%, the magnitude of the effect did not increase with increasing concentration of ethanol; treated animals continued to select temperatures about 2 C below temperatures selected by controls. Experiments alternating exposure to 1.0% ethanol and water showed that the rate of onset and disappearance of the ethanol effect was rapid (within 10 min). Other experiments exposing fish to 1.0% ethanol for up to 3 hr showed that the effect remained stable for this period of time. The thermoregulatory responses of fish are behavioral, and therefore relatively easy to observe and quantify. Ethanol produces a prompt, stable and reproducible depression of selected temperature in the goldfish. Because the temperature at which fish regulate is controlled by a central nervous system set point and not altered by effects on peripheral effector systems, it appears that ethanol may cause hypothermia in goldfish by directly acting to lower the set point. Close

• 28. [Article] Climatology of Katabatic Winds in the McMurdo Dry Valleys, Southern Victoria Land, Antarctica

  Katabatic winds dramatically affect the climate of the McMurdo dry valleys, Antarctica. Winter wind events can increase local air temperatures by 30°C. The frequency of katabatic winds largely controls ...

  Citation × Citation Citation Abstract Copy Title: Climatology of Katabatic Winds in the McMurdo Dry Valleys, Southern Victoria Land, Antarctica Author: Nylen, Thomas H., Fountain, Andrew G., Doran, Peter T. Year: 2004 Katabatic winds dramatically affect the climate of the McMurdo dry valleys, Antarctica. Winter wind events can increase local air temperatures by 30°C. The frequency of katabatic winds largely controls winter (June to August) temperatures, increasing 1°C per 1% increase in katabatic frequency, and it overwhelms the effect of topographic elevation (lapse rate). Summer katabatic winds are important, but their influence on summer temperature is less. The spatial distribution of katabatic winds varies significantly. Winter events increase by 14% for every 10 km up valley toward the ice sheet, and summer events increase by 3%. The spatial distribution of katabatic frequency seems to be partly controlled by inversions. The relatively slow propagation speed of a katabatic front compared to its wind speed suggests a highly turbulent flow. The apparent wind skip (down-valley stations can be affected before up-valley ones) may be caused by flow deflection in the complex topography and by flow over inversions, which eventually break down. A strong return flow occurs at down-valley stations prior to onset of the katabatic winds and after they dissipate. Although the onset and termination of the katabatic winds are typically abrupt, elevated air temperatures remain for days afterward. We estimate that current frequencies of katabatic winds increase annual average temperatures by 0.7° to 2.2°C, depending on location. Seasonally, they increase (decrease) winter average temperatures (relative humidity) by 0.8° to 4.2° (−1.8 to −8.5%) and summer temperatures by 0.1° to 0.4°C (−0.9% to −4.1%). Long-term changes of dry valley air temperatures cannot be understood without knowledge of changes in katabatic winds. Title: Climatology of Katabatic Winds in the McMurdo Dry Valleys, Southern Victoria Land, Antarctica Author: Nylen, Thomas H., Fountain, Andrew G., Doran, Peter T. Year: 2004 Katabatic winds dramatically affect the climate of the McMurdo dry valleys, Antarctica. Winter wind events can increase local air temperatures by 30°C. The frequency of katabatic winds largely controls winter (June to August) temperatures, increasing 1°C per 1% increase in katabatic frequency, and it overwhelms the effect of topographic elevation (lapse rate). Summer katabatic winds are important, but their influence on summer temperature is less. The spatial distribution of katabatic winds varies significantly. Winter events increase by 14% for every 10 km up valley toward the ice sheet, and summer events increase by 3%. The spatial distribution of katabatic frequency seems to be partly controlled by inversions. The relatively slow propagation speed of a katabatic front compared to its wind speed suggests a highly turbulent flow. The apparent wind skip (down-valley stations can be affected before up-valley ones) may be caused by flow deflection in the complex topography and by flow over inversions, which eventually break down. A strong return flow occurs at down-valley stations prior to onset of the katabatic winds and after they dissipate. Although the onset and termination of the katabatic winds are typically abrupt, elevated air temperatures remain for days afterward. We estimate that current frequencies of katabatic winds increase annual average temperatures by 0.7° to 2.2°C, depending on location. Seasonally, they increase (decrease) winter average temperatures (relative humidity) by 0.8° to 4.2° (−1.8 to −8.5%) and summer temperatures by 0.1° to 0.4°C (−0.9% to −4.1%). Long-term changes of dry valley air temperatures cannot be understood without knowledge of changes in katabatic winds. Close

• 29. [Article] Surface Temperature Probability Distributions in the NARCCAP Hindcast Experiment: Evaluation Methodology, Metrics, and Results

  Methodology is developed and applied to evaluate the characteristics of daily surface temperature distributions in a six-member regional climate model (RCM) hindcast experiment conducted as part of the ...

  Citation × Citation Citation Abstract Copy Title: Surface Temperature Probability Distributions in the NARCCAP Hindcast Experiment: Evaluation Methodology, Metrics, and Results Author: Loikith, Paul C., Waliser, Duane E., Lee, Huikyo, Kim, Jinwon, Neelin, J. David, Lintner, Benjamin R., McGinnis, Seth, Mattmann, Chris A., Mears, Linda O. Year: 2015 Methodology is developed and applied to evaluate the characteristics of daily surface temperature distributions in a six-member regional climate model (RCM) hindcast experiment conducted as part of the North American Regional Climate Change Assessment Program (NARCCAP). A surface temperature dataset combining gridded station observations and reanalysis is employed as the primary reference. Temperature biases are documented across the distribution, focusing on the median and tails. Temperature variance is generally higher in the RCMs than reference, while skewness is reasonably simulated in winter over the entire domain and over the western United States and Canada in summer. Substantial differences in skewness exist over the southern and eastern portions of the domain in summer. Four examples with observed long-tailed probability distribution functions (PDFs) are selected for model comparison. Long cold tails in the winter are simulated with high fidelity for Seattle, Washington, and Chicago, Illinois. In summer, theRCMs are unable to capture the distribution width and long warm tails for the coastal location of Los Angeles, California, while long cold tails are poorly realized for Houston, Texas. The evaluation results are repeated using two additional reanalysis products adjusted by station observations and two standard reanalysis products to assess the impact of observational uncertainty. Results are robust when compared with those obtained using the adjusted reanalysis products as reference, while larger uncertainties are introduced when standard reanalysis is employed as reference. Model biases identified in this work will allow for further investigation into associated mechanisms and implications for future simulations of temperature extremes. Title: Surface Temperature Probability Distributions in the NARCCAP Hindcast Experiment: Evaluation Methodology, Metrics, and Results Author: Loikith, Paul C., Waliser, Duane E., Lee, Huikyo, Kim, Jinwon, Neelin, J. David, Lintner, Benjamin R., McGinnis, Seth, Mattmann, Chris A., Mears, Linda O. Year: 2015 Methodology is developed and applied to evaluate the characteristics of daily surface temperature distributions in a six-member regional climate model (RCM) hindcast experiment conducted as part of the North American Regional Climate Change Assessment Program (NARCCAP). A surface temperature dataset combining gridded station observations and reanalysis is employed as the primary reference. Temperature biases are documented across the distribution, focusing on the median and tails. Temperature variance is generally higher in the RCMs than reference, while skewness is reasonably simulated in winter over the entire domain and over the western United States and Canada in summer. Substantial differences in skewness exist over the southern and eastern portions of the domain in summer. Four examples with observed long-tailed probability distribution functions (PDFs) are selected for model comparison. Long cold tails in the winter are simulated with high fidelity for Seattle, Washington, and Chicago, Illinois. In summer, theRCMs are unable to capture the distribution width and long warm tails for the coastal location of Los Angeles, California, while long cold tails are poorly realized for Houston, Texas. The evaluation results are repeated using two additional reanalysis products adjusted by station observations and two standard reanalysis products to assess the impact of observational uncertainty. Results are robust when compared with those obtained using the adjusted reanalysis products as reference, while larger uncertainties are introduced when standard reanalysis is employed as reference. Model biases identified in this work will allow for further investigation into associated mechanisms and implications for future simulations of temperature extremes. Close

• 30. [Article] Use of Distance Weighted Metrics to Investigate Landscape-Stream Temperature Relationships Across Different Temporal Scales

  Stream ecosystems have experienced significant negative impacts from land use, resource exploitation, and urban development. Statistical models allow researchers to explore the relationships between these ...

  Citation × Citation Citation Abstract Copy Title: Use of Distance Weighted Metrics to Investigate Landscape-Stream Temperature Relationships Across Different Temporal Scales Author: Watson, Eric Craig Year: 2016 Stream ecosystems have experienced significant negative impacts from land use, resource exploitation, and urban development. Statistical models allow researchers to explore the relationships between these landscape variables and stream conditions. Weighting the relevant landscape variables based on hydrologically defined distances offers a potential method of increasing the predictive capacity of statistical models. Using observations from three grouped watersheds in the Portland Metro Area (n=66), I have explored the use of three different weighting schemes against the standard method of taking an areal average. These four different model groups were applied to four stream temperature metrics: mean seven-day moving average maximum daily temperature (Mean7dTmax), number of days exceeding 17.8 °C (Tmax7d>17.8), mean daily range in stream temperature (Range_DTR), and the coefficient of variation in maximum daily temperature (CV_Tmax). These metrics were quantified for the 2011 dry season. The strength of these model groups were also examined at a monthly basis for each of the four months within the dry season. The results demonstrate mixed effectiveness of the weighting schemes, dependent on both the stream temperature metric being predicted as well as the time scale under investigation. Models for Mean7dTmax showed no benefit from the inclusion of distance weighted metrics, while models for Range_DTR consistently improved using distance weighted explanatory variables. Trends in the models for 7dTmax>17.8 and CV_Tmax varied based on temporal scale. Additionally, all model groups demonstrated greater explanatory power in early summer months than in late summer months. Title: Use of Distance Weighted Metrics to Investigate Landscape-Stream Temperature Relationships Across Different Temporal Scales Author: Watson, Eric Craig Year: 2016 Stream ecosystems have experienced significant negative impacts from land use, resource exploitation, and urban development. Statistical models allow researchers to explore the relationships between these landscape variables and stream conditions. Weighting the relevant landscape variables based on hydrologically defined distances offers a potential method of increasing the predictive capacity of statistical models. Using observations from three grouped watersheds in the Portland Metro Area (n=66), I have explored the use of three different weighting schemes against the standard method of taking an areal average. These four different model groups were applied to four stream temperature metrics: mean seven-day moving average maximum daily temperature (Mean7dTmax), number of days exceeding 17.8 °C (Tmax7d>17.8), mean daily range in stream temperature (Range_DTR), and the coefficient of variation in maximum daily temperature (CV_Tmax). These metrics were quantified for the 2011 dry season. The strength of these model groups were also examined at a monthly basis for each of the four months within the dry season. The results demonstrate mixed effectiveness of the weighting schemes, dependent on both the stream temperature metric being predicted as well as the time scale under investigation. Models for Mean7dTmax showed no benefit from the inclusion of distance weighted metrics, while models for Range_DTR consistently improved using distance weighted explanatory variables. Trends in the models for 7dTmax>17.8 and CV_Tmax varied based on temporal scale. Additionally, all model groups demonstrated greater explanatory power in early summer months than in late summer months. Close