Keith Brewster | University of Oklahoma (original) (raw)
Papers by Keith Brewster
Geophysical Research Letters
Weather and Forecasting
The 2016–18 NOAA Hazardous Weather Testbed (HWT) Spring Forecasting Experiments (SFE) featured th... more The 2016–18 NOAA Hazardous Weather Testbed (HWT) Spring Forecasting Experiments (SFE) featured the Community Leveraged Unified Ensemble (CLUE), a coordinated convection-allowing model (CAM) ensemble framework designed to provide empirical guidance for development of operational CAM systems. The 2017 CLUE included 81 members that all used 3-km horizontal grid spacing over the CONUS, enabling direct comparison of forecasts generated using different dynamical cores, physics schemes, and initialization procedures. This study uses forecasts from several of the 2017 CLUE members and one operational model to evaluate and compare CAM representation and next-day prediction of thunderstorms. The analysis utilizes existing techniques and novel, object-based techniques that distill important information about modeled and observed storms from many cases. The National Severe Storms Laboratory Multi-Radar Multi-Sensor product suite is used to verify model forecasts and climatologies of observed va...
Weather and Forecasting
During the summers of 2016 and 2017, the Center for Analysis and Prediction of Storms (CAPS) ran ... more During the summers of 2016 and 2017, the Center for Analysis and Prediction of Storms (CAPS) ran real-time storm-scale ensemble forecasts (SSEF) in support of the Hydrometeorology Testbed (HMT) Flash Flood and Intense Rainfall (FFaIR) experiment. These forecasts, using WRF-ARW and NMMB in 2016, and WRF-ARW and FV3 in 2017, covered the contiguous United States at 3 km horizontal grid spacing, and supported the generation and evaluation of precipitation forecast products, including ensemble probabilistic products. Forecasts of 3 h precipitation accumulation are evaluated. Overall, the SSEF produces skillful 3 h accumulated precipitation forecasts, with ARW members generally out-performing NMMB members, and the single FV3 member run in 2017 outperforming ARW members; these differences are significant at some forecast hours. Statistically significant differences exist in the performance, in terms of bias and ETS, among sub-ensembles of members sharing common microphysics and PBL schemes. Year-to-year consistency is higher for PBL sub-ensembles than for microphysical sub-ensembles. Probability-matched (PM) ensemble mean forecasts outperform individual members, while the simple ensemble mean exhibits substantial bias. A newly-developed localized probability-matched (LPM) ensemble mean product was produced in 2017; compared to the simple ensemble mean and the conventional PM mean, LPM mean exhibits improved retention of small-scale structures, evident in both 2D forecast fields and variance spectra. Probabilistic forecasts of precipitation exceeding Flash Flood Guidance (FFG) or thresholds associated with return intervals (RI) ranging from 10 to 100 years show utility in predicting regions of flooding threat, but generally over-predict the occurrence of such events.
Sensors
The deployment of small unmanned aircraft systems (UAS) to collect routine in situ vertical profi... more The deployment of small unmanned aircraft systems (UAS) to collect routine in situ vertical profiles of the thermodynamic and kinematic state of the atmosphere in conjunction with other weather observations could significantly improve weather forecasting skill and resolution. High-resolution vertical measurements of pressure, temperature, humidity, wind speed and wind direction are critical to the understanding of atmospheric boundary layer processes integral to air–surface (land, ocean and sea ice) exchanges of energy, momentum, and moisture; how these are affected by climate variability; and how they impact weather forecasts and air quality simulations. We explore the potential value of collecting coordinated atmospheric profiles at fixed surface observing sites at designated times using instrumented UAS. We refer to such a network of autonomous weather UAS designed for atmospheric profiling and capable of operating in most weather conditions as a 3D Mesonet. We outline some of th...
Bulletin of the American Meteorological Society
One primary goal of annual Spring Forecasting Experiments (SFEs), which are coorganized by NOAA’s... more One primary goal of annual Spring Forecasting Experiments (SFEs), which are coorganized by NOAA’s National Severe Storms Laboratory and Storm Prediction Center and conducted in the National Oceanic and Atmospheric Administration’s (NOAA) Hazardous Weather Testbed, is documenting performance characteristics of experimental, convection-allowing modeling systems (CAMs). Since 2007, the number of CAMs (including CAM ensembles) examined in the SFEs has increased dramatically, peaking at six different CAM ensembles in 2015. Meanwhile, major advances have been made in creating, importing, processing, verifying, and developing tools for analyzing and visualizing these large and complex datasets. However, progress toward identifying optimal CAM ensemble configurations has been inhibited because the different CAM systems have been independently designed, making it difficult to attribute differences in performance characteristics. Thus, for the 2016 SFE, a much more coordinated effort among ma...
Monthly Weather Review
The Nationwide Network of Networks (NNoN) concept was introduced by the National Research Council... more The Nationwide Network of Networks (NNoN) concept was introduced by the National Research Council to address the growing need for a national mesoscale observing system and the continued advancement toward accurate high-resolution numerical weather prediction. The research test bed known as the Dallas–Fort Worth (DFW) Urban Demonstration Network was created to experiment with many kinds of mesoscale observations that could be used in a data assimilation system. Many nonconventional observations, including Earth Networks and Citizen Weather Observer Program surface stations, are combined with conventional operational data to form the test bed network. A principal component of the NNoN effort is the quantification of observation impact from several different sources of information. In this study, the GSI-based EnKF system was used together with the WRF-ARW Model to examine impacts of observations assimilated for forecasting convection initiation (CI) in the 3 April 2014 hail storm case...
Monthly Weather Review
On 24 May 2011, Oklahoma experienced an outbreak of tornadoes, including one rated EF5 on the enh... more On 24 May 2011, Oklahoma experienced an outbreak of tornadoes, including one rated EF5 on the enhanced Fujita (EF) scale and two rated EF4. The extensive observation network in this area makes this an ideal case to examine the impact of using five different microphysics parameterization schemes, including single-, double-, and triple-moment microphysics, in an efficient high-resolution data assimilation system suitable for nowcasting and short-term forecasting with low latencies. Additionally, the real-time configuration of the 1-km ARPS, which assimilated increments produced by 3DVAR with cloud analysis using incremental analysis updating (IAU), had success providing a good baseline forecast. ARPS forecasts of 0–2 h are verified using observation-point, neighborhood, and object-based verification techniques. The object-based verification technique uses updraft helicity fields to represent mesocyclone centers, which are verified against tornado locations from three supercells of int...
Inthis study, the sensitivity of radio refractivity to temperature and moisture is analyzed and t... more Inthis study, the sensitivity of radio refractivity to temperature and moisture is analyzed and the effects of vertical gradients in temperature and moisture on the ,propagation ,paths of
Annales Geophysicae, 1994
The National Oceanic and Atmospheric Administration (NOAA) has completed the installation of a 30... more The National Oceanic and Atmospheric Administration (NOAA) has completed the installation of a 30-site demonstration network of wind-profiling radars in the central United States. The network is being used to demonstrate and assess the utility of wind profiler technology in a quasi-operational environment, and to help define operational requirements for possible future national networks. This paper describes two automated quality control methods designed to remove erroneous winds from the hourly network data. Case study examples and statistical evaluation of the performance of each method are also presented.
This project addresses tropical cyclone (TC) structure and intensity prediction improvement probl... more This project addresses tropical cyclone (TC) structure and intensity prediction improvement problem by (a) developing and testing advanced data assimilation (DA) capabilities for use by the Navy's COAMPS model and other community mesoscale prediction systems; and (b) by studying the effects of DA and initial condition and model errors at the convective scales on the predictability of TCs, which will in turn provide guidance to optimal ensemble prediction system design and DA improvement.
The radar ray path and beam broadening equations are important for assimilation of radar data int... more The radar ray path and beam broadening equations are important for assimilation of radar data into Numerical Weather Prediction (NWP) models. They can be used to determine the physical location of each radar measurement, and for properly mapping the atmospheric state variables from the model grid to the radar measurement space as part of the forward observation operators. Historically, different degrees of approximations have been made with these equations but no systematic evaluation of their impact exists, at least in the context of variational data assimilation. This study examines the effects of simplifying ray path and ray broadening
Geophysical Research Letters
Weather and Forecasting
The 2016–18 NOAA Hazardous Weather Testbed (HWT) Spring Forecasting Experiments (SFE) featured th... more The 2016–18 NOAA Hazardous Weather Testbed (HWT) Spring Forecasting Experiments (SFE) featured the Community Leveraged Unified Ensemble (CLUE), a coordinated convection-allowing model (CAM) ensemble framework designed to provide empirical guidance for development of operational CAM systems. The 2017 CLUE included 81 members that all used 3-km horizontal grid spacing over the CONUS, enabling direct comparison of forecasts generated using different dynamical cores, physics schemes, and initialization procedures. This study uses forecasts from several of the 2017 CLUE members and one operational model to evaluate and compare CAM representation and next-day prediction of thunderstorms. The analysis utilizes existing techniques and novel, object-based techniques that distill important information about modeled and observed storms from many cases. The National Severe Storms Laboratory Multi-Radar Multi-Sensor product suite is used to verify model forecasts and climatologies of observed va...
Weather and Forecasting
During the summers of 2016 and 2017, the Center for Analysis and Prediction of Storms (CAPS) ran ... more During the summers of 2016 and 2017, the Center for Analysis and Prediction of Storms (CAPS) ran real-time storm-scale ensemble forecasts (SSEF) in support of the Hydrometeorology Testbed (HMT) Flash Flood and Intense Rainfall (FFaIR) experiment. These forecasts, using WRF-ARW and NMMB in 2016, and WRF-ARW and FV3 in 2017, covered the contiguous United States at 3 km horizontal grid spacing, and supported the generation and evaluation of precipitation forecast products, including ensemble probabilistic products. Forecasts of 3 h precipitation accumulation are evaluated. Overall, the SSEF produces skillful 3 h accumulated precipitation forecasts, with ARW members generally out-performing NMMB members, and the single FV3 member run in 2017 outperforming ARW members; these differences are significant at some forecast hours. Statistically significant differences exist in the performance, in terms of bias and ETS, among sub-ensembles of members sharing common microphysics and PBL schemes. Year-to-year consistency is higher for PBL sub-ensembles than for microphysical sub-ensembles. Probability-matched (PM) ensemble mean forecasts outperform individual members, while the simple ensemble mean exhibits substantial bias. A newly-developed localized probability-matched (LPM) ensemble mean product was produced in 2017; compared to the simple ensemble mean and the conventional PM mean, LPM mean exhibits improved retention of small-scale structures, evident in both 2D forecast fields and variance spectra. Probabilistic forecasts of precipitation exceeding Flash Flood Guidance (FFG) or thresholds associated with return intervals (RI) ranging from 10 to 100 years show utility in predicting regions of flooding threat, but generally over-predict the occurrence of such events.
Sensors
The deployment of small unmanned aircraft systems (UAS) to collect routine in situ vertical profi... more The deployment of small unmanned aircraft systems (UAS) to collect routine in situ vertical profiles of the thermodynamic and kinematic state of the atmosphere in conjunction with other weather observations could significantly improve weather forecasting skill and resolution. High-resolution vertical measurements of pressure, temperature, humidity, wind speed and wind direction are critical to the understanding of atmospheric boundary layer processes integral to air–surface (land, ocean and sea ice) exchanges of energy, momentum, and moisture; how these are affected by climate variability; and how they impact weather forecasts and air quality simulations. We explore the potential value of collecting coordinated atmospheric profiles at fixed surface observing sites at designated times using instrumented UAS. We refer to such a network of autonomous weather UAS designed for atmospheric profiling and capable of operating in most weather conditions as a 3D Mesonet. We outline some of th...
Bulletin of the American Meteorological Society
One primary goal of annual Spring Forecasting Experiments (SFEs), which are coorganized by NOAA’s... more One primary goal of annual Spring Forecasting Experiments (SFEs), which are coorganized by NOAA’s National Severe Storms Laboratory and Storm Prediction Center and conducted in the National Oceanic and Atmospheric Administration’s (NOAA) Hazardous Weather Testbed, is documenting performance characteristics of experimental, convection-allowing modeling systems (CAMs). Since 2007, the number of CAMs (including CAM ensembles) examined in the SFEs has increased dramatically, peaking at six different CAM ensembles in 2015. Meanwhile, major advances have been made in creating, importing, processing, verifying, and developing tools for analyzing and visualizing these large and complex datasets. However, progress toward identifying optimal CAM ensemble configurations has been inhibited because the different CAM systems have been independently designed, making it difficult to attribute differences in performance characteristics. Thus, for the 2016 SFE, a much more coordinated effort among ma...
Monthly Weather Review
The Nationwide Network of Networks (NNoN) concept was introduced by the National Research Council... more The Nationwide Network of Networks (NNoN) concept was introduced by the National Research Council to address the growing need for a national mesoscale observing system and the continued advancement toward accurate high-resolution numerical weather prediction. The research test bed known as the Dallas–Fort Worth (DFW) Urban Demonstration Network was created to experiment with many kinds of mesoscale observations that could be used in a data assimilation system. Many nonconventional observations, including Earth Networks and Citizen Weather Observer Program surface stations, are combined with conventional operational data to form the test bed network. A principal component of the NNoN effort is the quantification of observation impact from several different sources of information. In this study, the GSI-based EnKF system was used together with the WRF-ARW Model to examine impacts of observations assimilated for forecasting convection initiation (CI) in the 3 April 2014 hail storm case...
Monthly Weather Review
On 24 May 2011, Oklahoma experienced an outbreak of tornadoes, including one rated EF5 on the enh... more On 24 May 2011, Oklahoma experienced an outbreak of tornadoes, including one rated EF5 on the enhanced Fujita (EF) scale and two rated EF4. The extensive observation network in this area makes this an ideal case to examine the impact of using five different microphysics parameterization schemes, including single-, double-, and triple-moment microphysics, in an efficient high-resolution data assimilation system suitable for nowcasting and short-term forecasting with low latencies. Additionally, the real-time configuration of the 1-km ARPS, which assimilated increments produced by 3DVAR with cloud analysis using incremental analysis updating (IAU), had success providing a good baseline forecast. ARPS forecasts of 0–2 h are verified using observation-point, neighborhood, and object-based verification techniques. The object-based verification technique uses updraft helicity fields to represent mesocyclone centers, which are verified against tornado locations from three supercells of int...
Inthis study, the sensitivity of radio refractivity to temperature and moisture is analyzed and t... more Inthis study, the sensitivity of radio refractivity to temperature and moisture is analyzed and the effects of vertical gradients in temperature and moisture on the ,propagation ,paths of
Annales Geophysicae, 1994
The National Oceanic and Atmospheric Administration (NOAA) has completed the installation of a 30... more The National Oceanic and Atmospheric Administration (NOAA) has completed the installation of a 30-site demonstration network of wind-profiling radars in the central United States. The network is being used to demonstrate and assess the utility of wind profiler technology in a quasi-operational environment, and to help define operational requirements for possible future national networks. This paper describes two automated quality control methods designed to remove erroneous winds from the hourly network data. Case study examples and statistical evaluation of the performance of each method are also presented.
This project addresses tropical cyclone (TC) structure and intensity prediction improvement probl... more This project addresses tropical cyclone (TC) structure and intensity prediction improvement problem by (a) developing and testing advanced data assimilation (DA) capabilities for use by the Navy's COAMPS model and other community mesoscale prediction systems; and (b) by studying the effects of DA and initial condition and model errors at the convective scales on the predictability of TCs, which will in turn provide guidance to optimal ensemble prediction system design and DA improvement.
The radar ray path and beam broadening equations are important for assimilation of radar data int... more The radar ray path and beam broadening equations are important for assimilation of radar data into Numerical Weather Prediction (NWP) models. They can be used to determine the physical location of each radar measurement, and for properly mapping the atmospheric state variables from the model grid to the radar measurement space as part of the forward observation operators. Historically, different degrees of approximations have been made with these equations but no systematic evaluation of their impact exists, at least in the context of variational data assimilation. This study examines the effects of simplifying ray path and ray broadening