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Oceanography and Atmospheric Sciences and Meteorology
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- Atmospheric models (4)
- Atmospheric aerosols (2)
- Climatic changes (2)
- Climatic changes -- Mathematical models (2)
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- Evapotranspiration (2)
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- Cluster analysis (1)
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- Earth temperature -- Effect of soil moisture on (1)
- Earth temperature -- Mathematical models (1)
- Forest fires -- Environmental aspects -- Oregon (1)
- Global temperature changes (1)
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- Global warming -- South America (1)
- Greenhouse gases -- Environmental aspects -- South America (1)
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- Ice nuclei -- Effect on precipitation (Meteorology) (1)
Articles 1 - 18 of 18
Full-Text Articles in Physical Sciences and Mathematics
Dropsonde Observations Of The Ageostrophy Within The Pre-Cold-Frontal Low-Level Jet Associated With Atmospheric Rivers, Rueben Demirdgian, Joel R. Norris, Andrew Martin, F. Martin Ralph
Dropsonde Observations Of The Ageostrophy Within The Pre-Cold-Frontal Low-Level Jet Associated With Atmospheric Rivers, Rueben Demirdgian, Joel R. Norris, Andrew Martin, F. Martin Ralph
Geography Faculty Publications and Presentations
The pre-cold-frontal low-level jet (LLJ) is an important contributor for water vapor transport within atmospheric rivers, though its dynamics are not completely understood. The present study investigates the LLJ using dropsonde observations from 24 cross-atmospheric river transects taken during the CalWater-2014, 2015 and the AR-Recon 2016, 2018 field campaigns. It is found that the LLJ, located at ;1-km elevation ahead of the cold front, has an average maximum wind speed of 30ms21 and is strongly supergeostrophic with an average ageostrophic component of 6ms21. The alongfront ageostrophy occurs within the atmospheric layer (750–1250 m) known to strongly control orographic precipitation associated …
Contrasting Local And Long-Range-Transported Warm Ice-Nucleating Particles During An Atmospheric River In Coastal California, Usa, Andrew C. Martin, Gavin Cornwell, Charlotte M. Beall, Forest Cannon, Sean Reilly, Bas Schapp, Dolan Lucero, Jessie Creamean, F. Martin Ralph, Hari T. Mix, Kimberly Prather
Contrasting Local And Long-Range-Transported Warm Ice-Nucleating Particles During An Atmospheric River In Coastal California, Usa, Andrew C. Martin, Gavin Cornwell, Charlotte M. Beall, Forest Cannon, Sean Reilly, Bas Schapp, Dolan Lucero, Jessie Creamean, F. Martin Ralph, Hari T. Mix, Kimberly Prather
Geography Faculty Publications and Presentations
Ice-nucleating particles (INPs) have been found to influence the amount, phase and efficiency of precipitation from winter storms, including atmospheric rivers. Warm INPs, those that initiate freezing at temperatures warmer than −10ºC, are thought to be particularly impactful because they can create primary ice in mixed-phase clouds, enhancing precipitation efficiency. The dominant sources of warm INPs during atmospheric rivers, the role of meteorology in modulating transport and injection of warm INPs into atmospheric river clouds, and the impact of warm INPs on mixed-phase cloud properties are not well-understood. In this case study, time-resolved precipitation samples were collected during an atmospheric …
Classification Of Aerosol Population Type And Cloud Condensation Nuclei Properties In A Coastal California Littoral Environment Using An Unsupervised Cluster Model, Samuel A. Atwood, Sonia M. Kreidenweis, Paul J. Demott, Markus D. Petters, Gavin Cornwell, Andrew C. Martin, Kathryn A. Moore
Classification Of Aerosol Population Type And Cloud Condensation Nuclei Properties In A Coastal California Littoral Environment Using An Unsupervised Cluster Model, Samuel A. Atwood, Sonia M. Kreidenweis, Paul J. Demott, Markus D. Petters, Gavin Cornwell, Andrew C. Martin, Kathryn A. Moore
Geography Faculty Publications and Presentations
Aerosol particle and cloud condensation nuclei (CCN) measurements from a littoral location on the northern coast of California at Bodega Bay Marine Laboratory (BML) are presented for approximately six weeks of observations during the boreal winter–spring as part of the CalWater-2015 field campaign. The nature and variability of surface (marine boundary layer, MBL) aerosol populations were evaluated by classifying observations into periods of similar aerosol and meteorological characteristics using an unsupervised cluster model to derive distinct littoral aerosol population types and link them to source regions. Such classifications support efforts to understand the impact of changing aerosol properties on precipitation …
A Recent Systematic Increase In Vapor Pressure Deficit Over Tropical South America, Armineh Barkhordarian, Bahareh Saatchi, Ali Behrangi, Paul C. Loikith, Carlos R. Mechoso
A Recent Systematic Increase In Vapor Pressure Deficit Over Tropical South America, Armineh Barkhordarian, Bahareh Saatchi, Ali Behrangi, Paul C. Loikith, Carlos R. Mechoso
Geography Faculty Publications and Presentations
We show a recent increasing trend in Vapor Pressure Deficit (VPD) over tropical South America in dry months with values well beyond the range of trends due to natural variability of the climate system defined in both the undisturbed Preindustrial climate and the climate over 850–1850 perturbed with natural external forcing. This trend is systematic in the southeast Amazon but driven by episodic droughts (2005, 2010, 2015) in the northwest, with the highest recoded VPD since 1979 for the 2015 drought. The univariant detection analysis shows that the observed increase in VPD cannot be explained by greenhouse-gas-induced (GHG) radiative warming …
The Influence Of Recurrent Modes Of Climate Variability On The Occurrence Of Monthly Temperature Extremes Over South America, Paul C. Loikith, Judah Detzer, Carlos R. Mechoso, Huikyo Lee, Armineh Barkhordarian
The Influence Of Recurrent Modes Of Climate Variability On The Occurrence Of Monthly Temperature Extremes Over South America, Paul C. Loikith, Judah Detzer, Carlos R. Mechoso, Huikyo Lee, Armineh Barkhordarian
Geography Faculty Publications and Presentations
The associations between extreme temperature months and four prominent modes of recurrent climate variability are examined over South America. Associations are computed as the percent of extreme temperature months concurrent with the upper and lower quartiles of the El Niño–Southern Oscillation (ENSO), the Atlantic Niño, the Pacific Decadal Oscillation (PDO), and the Southern Annular Mode (SAM) index distributions, stratified by season. The relationship is strongest for ENSO, with nearly every extreme temperature month concurrent with the upper or lower quartiles of its distribution in portions of northwestern South America during some seasons. The likelihood of extreme warm temperatures is enhanced …
Sensitivity Of Conus Summer Rainfall To The Selection Of Cumulus Parameterization Schemes In Nu-Wrf Seasonal Simulations, Takamichi Iguchi, Wei-Kuo Tao, Di Wu, Christa D. Peters-Lidard, Joseph A. Santanello, Eric Kemp, Yudong Tian, Jonathan Case, Weile Wang, Robert Ferraro, Duane E. Waliser, Jinwon Kim, Huikyo Lee, Bin Guan, Baijun Tian, Paul C. Loikith
Sensitivity Of Conus Summer Rainfall To The Selection Of Cumulus Parameterization Schemes In Nu-Wrf Seasonal Simulations, Takamichi Iguchi, Wei-Kuo Tao, Di Wu, Christa D. Peters-Lidard, Joseph A. Santanello, Eric Kemp, Yudong Tian, Jonathan Case, Weile Wang, Robert Ferraro, Duane E. Waliser, Jinwon Kim, Huikyo Lee, Bin Guan, Baijun Tian, Paul C. Loikith
Geography Faculty Publications and Presentations
This study investigates the sensitivity of daily rainfall rates in regional seasonal simulations over the contiguous United States (CONUS) to different cumulus parameterization schemes. Daily rainfall fields were simulated at 24-km resolution using the NASA-Unified Weather Research and Forecasting (NU-WRF) Model for June–August 2000. Four cumulus parameterization schemes and two options for shallow cumulus components in a specific scheme were tested. The spread in the domain-mean rainfall rates across the parameterization schemes was generally consistent between the entire CONUS and most subregions. The selection of the shallow cumulus component in a specific scheme had more impact than that of the …
Watershed Response To Climate Change And Fire-Burns In The Upper Umatilla River Basin, Usa, Kimberly Crystal Yazzie, Heejun Chang
Watershed Response To Climate Change And Fire-Burns In The Upper Umatilla River Basin, Usa, Kimberly Crystal Yazzie, Heejun Chang
Geography Faculty Publications and Presentations
This study analyzed watershed response to climate change and forest fire impacts in the upper Umatilla River Basin (URB), Oregon, using the precipitation runoff modeling system. Ten global climate models using Coupled Intercomparison Project Phase 5 experiments with Representative Concentration Pathways (RCP) 4.5 and 8.5 were used to simulate the effects of climate and fire-burns on runoff behavior throughout the 21st century. We observed the center timing (CT) of flow, seasonal flows, snow water equivalent (SWE) and basin recharge. In the upper URB, hydrologic regime shifts from a snow-rain-dominated to rain-dominated basin. Ensemble mean CT occurs 27 days earlier in …
Evaluating Hourly Rainfall Characteristics Over The U.S. Great Plains In Dynamically Downscaled Climate Model Simulations Using Nasa-Unified Wrf, Huikyo Lee, Duane E. Waliser, Robert Ferraro, Takamichi Iguchi, Christa D. Peters-Lidard, Baijun Tian, Paul C. Loikith, Daniel B. Wright
Evaluating Hourly Rainfall Characteristics Over The U.S. Great Plains In Dynamically Downscaled Climate Model Simulations Using Nasa-Unified Wrf, Huikyo Lee, Duane E. Waliser, Robert Ferraro, Takamichi Iguchi, Christa D. Peters-Lidard, Baijun Tian, Paul C. Loikith, Daniel B. Wright
Geography Faculty Publications and Presentations
Accurate simulation of extreme precipitation events remains a challenge in climate models. This study utilizes hourly precipitation data from ground stations and satellite instruments to evaluate rainfall characteristics simulated by the NASA-Unified Weather Research and Forecasting (NU-WRF) regional climate model at horizontal resolutions of 4, 12, and 24 km over the Great Plains of the United States. We also examined the sensitivity of the simulated precipitation to different spectral nudging approaches and the cumulus parameterizations. The rainfall characteristics in the observations and simulations were defined as an hourly diurnal cycle of precipitation and a joint probability distribution function (JPDF) between …
The Conflict Resolution Case Study In Urban Life: Bull Run Watershed Case, Chang-Yu Hong
The Conflict Resolution Case Study In Urban Life: Bull Run Watershed Case, Chang-Yu Hong
Geography Faculty Publications and Presentations
The City of Portland and the United States Department of Agriculture (USDA) Forest Service are working together, along with citizens, to formulate a comprehensive new policy to guide joint management of the Bull Run watershed at Mt. Hood National Forest. This process has brought about four decades of conflict, resulting from differences between the federal view of multiple use and the local view of exclusive use for producing high quality water. The new policy is being formulated by the City of Portland and the Forest Service through negotiation of a comprehensive Memorandum of Understanding that structures the parties’ roles, responsibilities, …
Evaluation Of Large‑Scale Meteorological Patterns Associated With Temperature Extremes In The Narccap Regional Climate Model Simulations, Paul C. Loikith, Duane E. Waliser, Huikyo Lee, J. David Neelin, Benjamin Lintner, Seth Mcginnis, Linda Mears, Jinwon Kim
Evaluation Of Large‑Scale Meteorological Patterns Associated With Temperature Extremes In The Narccap Regional Climate Model Simulations, Paul C. Loikith, Duane E. Waliser, Huikyo Lee, J. David Neelin, Benjamin Lintner, Seth Mcginnis, Linda Mears, Jinwon Kim
Geography Faculty Publications and Presentations
Large-scale meteorological patterns (LSMPs) associated with temperature extremes are evaluated in a suite of regional climate model (RCM) simulations contributing to the North American Regional Climate Change Assessment Program. LSMPs are characterized through composites of surface air temperature, sea level pressure, and 500 hPa geopotential height anomalies concurrent with extreme temperature days. Six of the seventeen RCM simulations are driven by boundary conditions from reanalysis while the other eleven are driven by one of four global climate models (GCMs). Four illustrative case studies are analyzed in detail. Model fidelity in LSMP spatial representation is high for cold winter extremes near …
Utilizing Humidity And Temperature Data To Advance Monitoring And Prediction Of Meteorological Drought, Ali Behrangi, Paul C. Loikith, Eric J. Fetzer, Hai M. Nguyen, Stephanie L. Granger
Utilizing Humidity And Temperature Data To Advance Monitoring And Prediction Of Meteorological Drought, Ali Behrangi, Paul C. Loikith, Eric J. Fetzer, Hai M. Nguyen, Stephanie L. Granger
Geography Faculty Publications and Presentations
The fraction of land area over the Continental United States experiencing extreme hot and dry conditions has been increasing over the past several decades, consistent with expectation from anthropogenic climate change. A clear concurrent change in precipitation, however, has not been confirmed. Vapor pressure deficit (VPD), combining temperature and humidity, is utilized here as an indicator of the background atmospheric conditions associated with meteorological drought. Furthermore, atmospheric conditions associated with warm season drought events are assessed by partitioning associated VPD anomalies into the temperature and humidity components. This approach suggests that the concurrence of anomalously high temperature and low humidity …
Short-Tailed Temperature Distributions Over North America And Implications For Future Changes In Extremes, Paul C. Loikith, J. David Neelin
Short-Tailed Temperature Distributions Over North America And Implications For Future Changes In Extremes, Paul C. Loikith, J. David Neelin
Geography Faculty Publications and Presentations
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 …
Comparison Between Observed And Model-Simulated Atmospheric Circulationpatterns Associated With Extreme Temperature Days Over North Americausing Cmip5 Historical Simulations, Paul C. Loikith, Anthony J. Broccoli
Comparison Between Observed And Model-Simulated Atmospheric Circulationpatterns Associated With Extreme Temperature Days Over North Americausing Cmip5 Historical Simulations, Paul C. Loikith, Anthony J. Broccoli
Geography Faculty Publications and Presentations
Circulation patterns associated with extreme temperature days over North America, as simulated by a suite of climate models, are compared with those obtained from observations. The authors analyze 17 coupled atmosphere–ocean general circulation models contributing to the fifth phase of the Coupled Model Intercomparison Project. Circulation patterns are defined as composites of anomalies in sea level pressure and 500-hPa geopotential height concurrent with days in the tails of temperature distribution. Several metrics used to systematically describe circulation patterns associated with extreme temperature days are applied to both the observed and model-simulated data. Additionally, self-organizing maps are employed as a means …
Surface Temperature Probability Distributions In The Narccap Hindcast Experiment: Evaluation Methodology, Metrics, And Results, Paul C. Loikith, Duane E. Waliser, Huikyo Lee, Jinwon Kim, J. David Neelin, Benjamin R. Lintner, Seth Mcginnis, Chris A. Mattmann, Linda O. Mears
Surface Temperature Probability Distributions In The Narccap Hindcast Experiment: Evaluation Methodology, Metrics, And Results, Paul C. Loikith, Duane E. Waliser, Huikyo Lee, Jinwon Kim, J. David Neelin, Benjamin R. Lintner, Seth Mcginnis, Chris A. Mattmann, Linda O. Mears
Geography Faculty Publications and Presentations
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 …
Impact Of Soil Moisture–Atmosphere Interactions On Surface Temperature Distribution, Alexis Berg, Benjamin R. Lintner, Kirsten L. Findell, Sergey Malyshev, Paul C. Loikith, Pierre Gentine
Impact Of Soil Moisture–Atmosphere Interactions On Surface Temperature Distribution, Alexis Berg, Benjamin R. Lintner, Kirsten L. Findell, Sergey Malyshev, Paul C. Loikith, Pierre Gentine
Geography Faculty Publications and Presentations
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, …
The Influence Of Recurrent Modes Of Climate Variability On The Occurrence Of Winter And Summer Extreme Temperatures Over North America, Paul C. Loikith, Anthony J. Broccoli
The Influence Of Recurrent Modes Of Climate Variability On The Occurrence Of Winter And Summer Extreme Temperatures Over North America, Paul C. Loikith, Anthony J. Broccoli
Geography Faculty Publications and Presentations
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 …
Effects Of Runoff Sensitivity And Catchment Characteristics On Regional Actual Evapotranspiration Trends In The Conterminous Us, Il-Won Jung, Heejun Chang, John Risley
Effects Of Runoff Sensitivity And Catchment Characteristics On Regional Actual Evapotranspiration Trends In The Conterminous Us, Il-Won Jung, Heejun Chang, John Risley
Geography Faculty Publications and Presentations
An understanding of the role of hydro-climatic and geographic regimes on regional actual evapotranspiration (AET) change is essential to improving our knowledge on predicting water availability in a changing climate. This study investigates the relationship between AET change for a 60 year period (1951–2010) and the runoff sensitivity in 255 undisturbed catchments over the US. The runoff sensitivity to climate change is simply defined as the relative magnitude between runoff and precipitation changes with time. Runoff sensitivity can readily explain the conflicting directions of AET changes under similar precipitation change. Under increasing precipitation, AET decreases when runoff is increasing more …
Classifying Reanalysis Surface Temperature Probability Density Functions (Pdfs) Over North America With Cluster Analysis, Paul C. Loikith, Benjamin R. Lintner, Jinwon Kim, Huikyo Lee
Classifying Reanalysis Surface Temperature Probability Density Functions (Pdfs) Over North America With Cluster Analysis, Paul C. Loikith, Benjamin R. Lintner, Jinwon Kim, Huikyo Lee
Geography Faculty Publications and Presentations
An important step in projecting future climate change impacts on extremes involves quantifying the underlying probability distribution functions (PDFs) of climate variables. However, doing so can prove challenging when multiple models and large domains are considered. Here an approach to PDF quantification using k-means clustering is considered. A standard clustering algorithm (with k = 5 clusters) is applied to 33 years of daily January surface temperature from two state-of-the-art reanalysis products, the North American Regional Reanalysis and the Modern Era Retrospective Analysis for Research and Applications. The resulting cluster assignments yield spatially coherent patterns that can be broadly related to …