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• 1. [Article] Surface temperature lapse rates over complex terrain: Lessons from the Cascade Mountains

  The typically sparse distribution of weather stations in mountainous terrain inadequately resolves temperature variability. Accordingly, high‐resolution gridding of climate data (for applications such ...

  Citation × Citation Citation Abstract Copy Title: Surface temperature lapse rates over complex terrain: Lessons from the Cascade Mountains Author: Mote, Philip W., Lundquist, Jessica D., Minder, Justin R. The typically sparse distribution of weather stations in mountainous terrain inadequately resolves temperature variability. Accordingly, high‐resolution gridding of climate data (for applications such as hydrological modeling) often relies on assumptions such as a constant surface temperature lapse rate (i.e., decrease of surface temperature with altitude) of 6.5°C km⁻¹. Using an example of the Cascade Mountains, we describe the temporal and spatial variability of the surface temperature lapse rate, combining data from: (1) COOP stations, (2) nearby radiosonde launches, (3) a temporary dense network of sensors, (4) forecasts from the MM5 regional model, and (5) PRISM geo‐statistical analyses. On the windward side of the range, the various data sources reveal annual mean lapse rates of 3.9–5.2°C km⁻¹, substantially smaller than the often‐assumed 6.5°C km⁻¹. The data sets show similar seasonal and diurnal variability, with lapse rates smallest (2.5–3.5°C km⁻¹) in late‐summer minimum temperatures, and largest (6.5–7.5°C km⁻¹) in spring maximum temperatures. Geographic (windward versus lee side) differences in lapse rates are found to be substantial. Using a simple runoff model, we show the appreciable implications of these results for hydrological modeling. Title: Surface temperature lapse rates over complex terrain: Lessons from the Cascade Mountains Author: Mote, Philip W., Lundquist, Jessica D., Minder, Justin R. The typically sparse distribution of weather stations in mountainous terrain inadequately resolves temperature variability. Accordingly, high‐resolution gridding of climate data (for applications such as hydrological modeling) often relies on assumptions such as a constant surface temperature lapse rate (i.e., decrease of surface temperature with altitude) of 6.5°C km⁻¹. Using an example of the Cascade Mountains, we describe the temporal and spatial variability of the surface temperature lapse rate, combining data from: (1) COOP stations, (2) nearby radiosonde launches, (3) a temporary dense network of sensors, (4) forecasts from the MM5 regional model, and (5) PRISM geo‐statistical analyses. On the windward side of the range, the various data sources reveal annual mean lapse rates of 3.9–5.2°C km⁻¹, substantially smaller than the often‐assumed 6.5°C km⁻¹. The data sets show similar seasonal and diurnal variability, with lapse rates smallest (2.5–3.5°C km⁻¹) in late‐summer minimum temperatures, and largest (6.5–7.5°C km⁻¹) in spring maximum temperatures. Geographic (windward versus lee side) differences in lapse rates are found to be substantial. Using a simple runoff model, we show the appreciable implications of these results for hydrological modeling. Close

• 2. [Article] Assessing the Impacts of Global Warming on Snowpack in the Washington Cascades

  The decrease in mountain snowpack associated with global warming is difficult to estimate in the presence of the large year-to-year natural variability in observations of snow-water equivalent (SWE). A ...

  Citation × Citation Citation Abstract Copy Title: Assessing the Impacts of Global Warming on Snowpack in the Washington Cascades Author: Mote, Philip W., Stoelinga, Mark T., Lettenmaier, Dennis P., Casola, Joseph H., Wallace, John M., Cuo, Lan, Livneh, Ben The decrease in mountain snowpack associated with global warming is difficult to estimate in the presence of the large year-to-year natural variability in observations of snow-water equivalent (SWE). A more robust approach for inferring the impacts of global warming is to estimate the temperature sensitivity (λ) of spring snowpack and multiply it by putative past and future temperature rises observed across the Northern Hemisphere. Estimates of λ can be obtained from (i) simple geometric considerations based on the notion that as the seasonal-mean temperature rises by the amount δT, the freezing level and the entire snowpack should rise by the increment δT/Γ, where Γ is the mean lapse rate; (ii) the regression of 1 April SWE measurements upon mean winter temperatures; (iii) a hydrological model forced by daily temperature and precipitation observations; and (iv) the use of inferred accumulated snowfall derived from daily temperature and precipitation data as a proxy for SWE. All four methods yield an estimated sensitivity of 20% of spring snowpack lost per degree Celsius temperature rise. The increase of precipitation accompanying a 1°C warming can be expected to decrease the sensitivity to 16%. Considering observations of temperature rise over the Northern Hemisphere, it is estimated that spring snow-water equivalent in the Cascades portion of the Puget Sound drainage basin should have declined by 8%–16% over the past 30 yr resulting from global warming, and it can be expected to decline by another 11%–21% by 2050. These losses would be statistically undetectable from a trend analysis of the region’s snowpack over the past 30 yr. Title: Assessing the Impacts of Global Warming on Snowpack in the Washington Cascades Author: Mote, Philip W., Stoelinga, Mark T., Lettenmaier, Dennis P., Casola, Joseph H., Wallace, John M., Cuo, Lan, Livneh, Ben The decrease in mountain snowpack associated with global warming is difficult to estimate in the presence of the large year-to-year natural variability in observations of snow-water equivalent (SWE). A more robust approach for inferring the impacts of global warming is to estimate the temperature sensitivity (λ) of spring snowpack and multiply it by putative past and future temperature rises observed across the Northern Hemisphere. Estimates of λ can be obtained from (i) simple geometric considerations based on the notion that as the seasonal-mean temperature rises by the amount δT, the freezing level and the entire snowpack should rise by the increment δT/Γ, where Γ is the mean lapse rate; (ii) the regression of 1 April SWE measurements upon mean winter temperatures; (iii) a hydrological model forced by daily temperature and precipitation observations; and (iv) the use of inferred accumulated snowfall derived from daily temperature and precipitation data as a proxy for SWE. All four methods yield an estimated sensitivity of 20% of spring snowpack lost per degree Celsius temperature rise. The increase of precipitation accompanying a 1°C warming can be expected to decrease the sensitivity to 16%. Considering observations of temperature rise over the Northern Hemisphere, it is estimated that spring snow-water equivalent in the Cascades portion of the Puget Sound drainage basin should have declined by 8%–16% over the past 30 yr resulting from global warming, and it can be expected to decline by another 11%–21% by 2050. These losses would be statistically undetectable from a trend analysis of the region’s snowpack over the past 30 yr. Close

• 3. [Article] Climate-Driven Variability and Trends in Mountain Snowpack in Western North America

  Records of 1 April snow water equivalent (SWE) are examined here using multiple linear regression against reference time series of temperature and precipitation. This method permits 1) an examination of ...

  Citation × Citation Citation Abstract Copy Title: Climate-Driven Variability and Trends in Mountain Snowpack in Western North America Author: Mote, Philip W. Records of 1 April snow water equivalent (SWE) are examined here using multiple linear regression against reference time series of temperature and precipitation. This method permits 1) an examination of the separate roles of temperature and precipitation in determining the trends in SWE; 2) an estimation of the sensitivity of SWE to warming trends, and its distribution across western North America and as a function of elevation; and 3) inferences about responses of SWE to future warming. These results emphasize the sensitivity to warming of the mountains of northern California and the Cascades of Oregon and Washington. In addition, the contribution of modes of Pacific climate variability is examined and found to be responsible for about 10%–60% of the trends in SWE, depending on the period of record and climate index. Title: Climate-Driven Variability and Trends in Mountain Snowpack in Western North America Author: Mote, Philip W. Records of 1 April snow water equivalent (SWE) are examined here using multiple linear regression against reference time series of temperature and precipitation. This method permits 1) an examination of the separate roles of temperature and precipitation in determining the trends in SWE; 2) an estimation of the sensitivity of SWE to warming trends, and its distribution across western North America and as a function of elevation; and 3) inferences about responses of SWE to future warming. These results emphasize the sensitivity to warming of the mountains of northern California and the Cascades of Oregon and Washington. In addition, the contribution of modes of Pacific climate variability is examined and found to be responsible for about 10%–60% of the trends in SWE, depending on the period of record and climate index. Close

• 4. [Article] Trends in snow water equivcalent in the Pacific Northwest and their climatic causes

  Observations of snow water equivalent (SWE) in the Pacific Northwest are examined and compared with variability and trends in temperature and precipitation at nearby climate stations. At most locations, ...

  Citation × Citation Citation Abstract Copy Title: Trends in snow water equivcalent in the Pacific Northwest and their climatic causes Author: Mote, Philip W. Observations of snow water equivalent (SWE) in the Pacific Northwest are examined and compared with variability and trends in temperature and precipitation at nearby climate stations. At most locations, especially below about 1800 m, substantial declines in SWE coincide with significant increases in temperature, and occur in spite of increases in precipitation. Title: Trends in snow water equivcalent in the Pacific Northwest and their climatic causes Author: Mote, Philip W. Observations of snow water equivalent (SWE) in the Pacific Northwest are examined and compared with variability and trends in temperature and precipitation at nearby climate stations. At most locations, especially below about 1800 m, substantial declines in SWE coincide with significant increases in temperature, and occur in spite of increases in precipitation. Close

• 5. [Article] Seasonal variations of water vapor in the tropical lower stratosphere

  Measurements of stratospheric water vapor by the Microwave Limb Sounder aboard the Upper Atmosphere Research Satellite show that in the tropical lower stratosphere, low-frequency variations are closely related ...

  Citation × Citation Citation Abstract Copy Title: Seasonal variations of water vapor in the tropical lower stratosphere Author: Harwood, Robert S., Waters, Joe W., Holton, James R., Rosenloh, Karen H., Mote, Philip W. Measurements of stratospheric water vapor by the Microwave Limb Sounder aboard the Upper Atmosphere Research Satellite show that in the tropical lower stratosphere, low-frequency variations are closely related to the annual cycle in tropical tropopause temperatures. Tropical stratospheric air appears to retain information about the tropopause conditions it encountered for over a year as it rises through the stratosphere. We use a two-dimensional Lagrangian model to relate MLS measurements to the temperature that tropical air parcels encountered when crossing the 100 hPa surface. Title: Seasonal variations of water vapor in the tropical lower stratosphere Author: Harwood, Robert S., Waters, Joe W., Holton, James R., Rosenloh, Karen H., Mote, Philip W. Measurements of stratospheric water vapor by the Microwave Limb Sounder aboard the Upper Atmosphere Research Satellite show that in the tropical lower stratosphere, low-frequency variations are closely related to the annual cycle in tropical tropopause temperatures. Tropical stratospheric air appears to retain information about the tropopause conditions it encountered for over a year as it rises through the stratosphere. We use a two-dimensional Lagrangian model to relate MLS measurements to the temperature that tropical air parcels encountered when crossing the 100 hPa surface. Close

• 6. [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

• 7. [Article] Seasonal Climate Variability and Change in the Pacific Northwest of the United States

  This is the publisher’s final pdf. The published article is copyrighted by the American Meteorological Society and can be found at: http://journals.ametsoc.org/loi/clim.

  Citation × Citation Citation Abstract Copy Title: Seasonal Climate Variability and Change in the Pacific Northwest of the United States Author: Rupp, David E., Abatzoglou, John T., Mote, Philip W. This is the publisher’s final pdf. The published article is copyrighted by the American Meteorological Society and can be found at: http://journals.ametsoc.org/loi/clim. Title: Seasonal Climate Variability and Change in the Pacific Northwest of the United States Author: Rupp, David E., Abatzoglou, John T., Mote, Philip W. This is the publisher’s final pdf. The published article is copyrighted by the American Meteorological Society and can be found at: http://journals.ametsoc.org/loi/clim. Close

• 8. [Article] Variability of clouds and water vapor in low latitudes: view from Moderate Resolution Imaging Spectroradiometer (MODIS)

  This paper shows a small sampling of the atmospheric fields provided by the Moderate Resolution Imaging Spectroradiometer (MODIS), which is installed on both the Terra and Aqua satellites of the Earth ...

  Citation × Citation Citation Abstract Copy Title: Variability of clouds and water vapor in low latitudes: view from Moderate Resolution Imaging Spectroradiometer (MODIS) Author: Mote, Philip W., Frey, Richard This paper shows a small sampling of the atmospheric fields provided by the Moderate Resolution Imaging Spectroradiometer (MODIS), which is installed on both the Terra and Aqua satellites of the Earth Observing System. These fields include macroscale fields like cloud fraction, cloud top pressure, cloud optical depth, and column water vapor, and microscale fields like cloud particle effective radius. Most of the atmospheric fields resemble, in spatial pattern and temporal evolution, the cloud top temperature field; several, however, including effective radius and clear-sky water vapor, have markedly different spatial patterns and temporal evolution, suggesting that large-scale controls on tropical water vapor are more complicated than a simple connection with large-scale convergence and convection would suggest. As with several previous studies, the cloud top temperature or pressure has a bimodal distribution with peaks in both the lower and upper troposphere. Our analysis also reveals a dependence of cloud effective particle size on sea surface temperature. Title: Variability of clouds and water vapor in low latitudes: view from Moderate Resolution Imaging Spectroradiometer (MODIS) Author: Mote, Philip W., Frey, Richard This paper shows a small sampling of the atmospheric fields provided by the Moderate Resolution Imaging Spectroradiometer (MODIS), which is installed on both the Terra and Aqua satellites of the Earth Observing System. These fields include macroscale fields like cloud fraction, cloud top pressure, cloud optical depth, and column water vapor, and microscale fields like cloud particle effective radius. Most of the atmospheric fields resemble, in spatial pattern and temporal evolution, the cloud top temperature field; several, however, including effective radius and clear-sky water vapor, have markedly different spatial patterns and temporal evolution, suggesting that large-scale controls on tropical water vapor are more complicated than a simple connection with large-scale convergence and convection would suggest. As with several previous studies, the cloud top temperature or pressure has a bimodal distribution with peaks in both the lower and upper troposphere. Our analysis also reveals a dependence of cloud effective particle size on sea surface temperature. Close

• 9. [Article] Anthropogenic influence on the changing likelihood of an exceptionally warm summer in Texas, 2011

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

  Citation × Citation Citation Abstract Copy Title: Anthropogenic influence on the changing likelihood of an exceptionally warm summer in Texas, 2011 Author: Massey, Neil, Rupp, David E., Allen, Myles, Mote, Philip W., Li, Sihan, Sparrow, Sarah N. This is the publisher’s final pdf. The published article is copyrighted by the American Geophysical Union and can be found at: http://agupubs.onlinelibrary.wiley.com/agu/journal/10.1002/%28ISSN%291944-8007/ Title: Anthropogenic influence on the changing likelihood of an exceptionally warm summer in Texas, 2011 Author: Massey, Neil, Rupp, David E., Allen, Myles, Mote, Philip W., Li, Sihan, Sparrow, Sarah N. This is the publisher’s final pdf. The published article is copyrighted by the American Geophysical Union and can be found at: http://agupubs.onlinelibrary.wiley.com/agu/journal/10.1002/%28ISSN%291944-8007/ Close

• 10. [Article] Kelvin waves in stratospheric temperature observed by the Microwave Limb Sounder

  The three-dimensional (3-D) structure of stratospheric Kelvin waves is revealed using data from the Microwave Limb Sounder for the period July 1992 to April 1993. Four Kelvin wave modes are identified, ...

  Citation × Citation Citation Abstract Copy Title: Kelvin waves in stratospheric temperature observed by the Microwave Limb Sounder Author: Dunkerton, Timothy J., Wu, Dong, Mote, Philip W. The three-dimensional (3-D) structure of stratospheric Kelvin waves is revealed using data from the Microwave Limb Sounder for the period July 1992 to April 1993. Four Kelvin wave modes are identified, two for zonal wave number 1 (k = 1) and two for k = 2, using extended empirical orthogonal functions. The 3-D structures of the modes agree with linear theory and satisfy the dispersion relation for Kelvin waves, and with periods ranging from 4.5 to 10 days the modes mostly fall near the boundary between ‘‘fast’’ and ‘‘slow’’ Kelvin waves [Canziani et al., 1998]. The analysis also identifies a feature that may correspond with the ‘‘pancake structures’’ associated with inertial instability. Title: Kelvin waves in stratospheric temperature observed by the Microwave Limb Sounder Author: Dunkerton, Timothy J., Wu, Dong, Mote, Philip W. The three-dimensional (3-D) structure of stratospheric Kelvin waves is revealed using data from the Microwave Limb Sounder for the period July 1992 to April 1993. Four Kelvin wave modes are identified, two for zonal wave number 1 (k = 1) and two for k = 2, using extended empirical orthogonal functions. The 3-D structures of the modes agree with linear theory and satisfy the dispersion relation for Kelvin waves, and with periods ranging from 4.5 to 10 days the modes mostly fall near the boundary between ‘‘fast’’ and ‘‘slow’’ Kelvin waves [Canziani et al., 1998]. The analysis also identifies a feature that may correspond with the ‘‘pancake structures’’ associated with inertial instability. Close