Julie Lundquist | University of Colorado, Boulder (original) (raw)
Papers by Julie Lundquist
Geophysical Research Letters, 2012
When monitoring winds and atmospheric stability for wind energy applications, remote sensing inst... more When monitoring winds and atmospheric stability for wind energy applications, remote sensing instruments present some advantages to in-situ instrumentation such as larger vertical extent, in some cases easy installation and maintenance, measurements of vertical humidity profiles throughout the boundary layer, and no restrictions on prevailing wind directions. In this study, we compare remote sensing devices, Windcube lidar and microwave radiometer, to meteorological in-situ tower measurements to demonstrate the accuracy of these measurements and to assess the utility of the remote sensing instruments in overcoming tower limitations. We compare temperature and wind observations, as well as calculations of Brunt-Väisälä frequency and Richardson numbers for the instrument deployment period in May-June 2011 at the U.S.
Department of Energy (DOE) reports produced after 1991 and a growing number of pre-1991 documents... more Department of Energy (DOE) reports produced after 1991 and a growing number of pre-1991 documents are available free via www.OSTI.gov.
Monthly Weather Review, 2013
Large wind farms are expected to influence local and regional atmospheric circulations. Using a m... more Large wind farms are expected to influence local and regional atmospheric circulations. Using a mesoscale parameterization of the effects of wind farms that includes a momentum sink and a wind speed–dependent source of turbulent kinetic energy, simulations were carried out to quantify the impact of a wind farm on an atmospheric boundary layer throughout a diurnal cycle. The presence of a wind farm covering 10 km × 10 km is found to have a significant impact on the local atmospheric flow and on regions up to 60 km downwind at night. Daytime convective conditions show little impact of the wind farm on wind speeds, as the momentum deficits generated by the wind farm rapidly mix through the depth of the boundary layer. At night, the stable layer within the rotor area inhibits turbulent mixing of the momentum deficit, leading to a shallower wake and a greater reduction in the wind speed within the wake. Although a low-level jet forms at altitudes within the rotor area in the hours before...
ABSTRACT The CASES-97 dataset, supplemented by data from the surrounding area and from satellite,... more ABSTRACT The CASES-97 dataset, supplemented by data from the surrounding area and from satellite, will enable us to isolate the effects of soil moisture on boundary layer evolution.Our initial approach will be to use the integrated dataset to determine (a) the factors that contribute to PBL growth, and (b) the factors that determine the wind, temperature, and wind profiles in the growing PBL. This process will help us to consolidate the dataset and tease out remaining inconsistencies. As soon as reasonable, we want to use the dataset in mesoscale numerical models, to test and refine our conclusions. Further detail on the CASES-97 field program can be found at the World Wide Web site at: http://www.mmm.ucar.edu/cases/cases.html.
Bulletin of the American Meteorological Society, 2000
Page 1. 757 Bulletin of the American Meteorological Society 1. Introduction The Walnut River Wate... more Page 1. 757 Bulletin of the American Meteorological Society 1. Introduction The Walnut River Watershed east of Wichita, Kan-sas, has become the focus of investigations to study the interaction of the lower atmosphere with the land surface, subsurface, and vegetation. ...
Tall wind turbines, with hub heights at 80 m or above, can extract large amounts of energy from t... more Tall wind turbines, with hub heights at 80 m or above, can extract large amounts of energy from the atmosphere because they are likely to encounter higher wind speeds, but they face challenges given the complex nature of wind flow and turbulence at these heights in the boundary layer. Depending on whether the boundary layer is stable, neutral, or convective, the mean wind speed, direction, and turbulence properties may vary greatly across the tall turbine swept area (40 to 120 m AGL). This variability can cause tall turbines to produce difference amounts of power during time periods with identical hub height wind speeds. Using meteorological and power generation data from a West Coast North American wind farm over a one-year period, our study synthesizes standard wind park observations, such as wind speed from turbine nacelles and sparse meteorological tower observations, with high-resolution profiles of wind speed and turbulence from a remote sensing platform, to quantify the impact of atmospheric stability on power output. We first compare approaches to defining atmospheric stability. The standard, limited, wind farm operations enable the calculation only of a wind shear exponent (α) or turbulence intensity (I U ) from cup anemometers, while the presence at this wind farm of a SODAR enables the direct observation of turbulent kinetic energy (TKE) throughout the turbine rotor disk. Additionally, a nearby research meteorological station provided observations of the Obukhov length, L, a direct measure of atmospheric stability. In general, the stability parameters α, I U , and TKE are in high agreement with the more physically-robust L, with TKE exhibiting the best agreement with L. Using these metrics, data periods are segregated by stability class to investigate power performance dependencies. Power output at this wind farm is highly correlated with atmospheric stability during the spring and summer months, while atmospheric stability exerts little impact on power output during the winter and autumn periods.
Atmospheric Measurement Techniques Discussions, 2014
Tall onshore wind turbines, with hub heights between 80 m and 100 m, can extract large amounts of... more Tall onshore wind turbines, with hub heights between 80 m and 100 m, can extract large amounts of energy from the atmosphere since they generally encounter higher wind speeds, but they face challenges given the complexity of boundary layer flows. This complexity of the lowest layers of the atmosphere, where wind turbines reside, has made conventional modeling efforts less than ideal. To meet the nation's goal of increasing wind power into the U.S. electrical grid, the accuracy of wind power forecasts must be improved.
33rd Wind Energy Symposium, 2015
ABSTRACT
The nocturnal low-level jet (LLJ) is a well-documented phenomenon around the world. The LLJ has b... more The nocturnal low-level jet (LLJ) is a well-documented phenomenon around the world. The LLJ has been studied in great detail in the southern Great Plains of the United States (Bonner 1968, Whiteman et al. 1997, Banta et al., 2002, Song et al. 2005), where it efficiently ...
... Robert Banta, W. Alan Brewer, R. Michael Hardesty. National Oceanic and Atmospheric Administr... more ... Robert Banta, W. Alan Brewer, R. Michael Hardesty. National Oceanic and Atmospheric Administration (NOAA) Earth System Research Laboratory ... References: 1. RJ Barthelmie, O. Rathmann, ST Frandsen, KS Hansen, E. Politis, J. Prospathopoulos, K. Rados, Modelling and ...
Boundary layer flows are greatly complicated by the presence of complex terrain which redirects m... more Boundary layer flows are greatly complicated by the presence of complex terrain which redirects mean flow and alters the structure of turbulence. Surface fluxes of heat and moisture provide addi-tional forcing which induce secondary flows, or can dominate flow dynamics in ...
A major objective of CASES-99 was to relate surface fluxes to features of the evolving stable bou... more A major objective of CASES-99 was to relate surface fluxes to features of the evolving stable boundary layer, such as the low-level jet (LLJ). In a recently completed study we used a combination of high-resolution Doppler lidar (HRDL: see Grund et al., 1999), a 60-m instrumented ...
Accurate numerical prediction of airflow and tracer dispersion in urban areas depends, to a great... more Accurate numerical prediction of airflow and tracer dispersion in urban areas depends, to a great extent, on the use of appropriate stability conditions. Due to the lack of relevant field measurements or sufficiently sophisticated turbulence models, modelers often assume that nearly neutral ...
Geophysical Research Letters, 2012
When monitoring winds and atmospheric stability for wind energy applications, remote sensing inst... more When monitoring winds and atmospheric stability for wind energy applications, remote sensing instruments present some advantages to in-situ instrumentation such as larger vertical extent, in some cases easy installation and maintenance, measurements of vertical humidity profiles throughout the boundary layer, and no restrictions on prevailing wind directions. In this study, we compare remote sensing devices, Windcube lidar and microwave radiometer, to meteorological in-situ tower measurements to demonstrate the accuracy of these measurements and to assess the utility of the remote sensing instruments in overcoming tower limitations. We compare temperature and wind observations, as well as calculations of Brunt-Väisälä frequency and Richardson numbers for the instrument deployment period in May-June 2011 at the U.S.
Department of Energy (DOE) reports produced after 1991 and a growing number of pre-1991 documents... more Department of Energy (DOE) reports produced after 1991 and a growing number of pre-1991 documents are available free via www.OSTI.gov.
Monthly Weather Review, 2013
Large wind farms are expected to influence local and regional atmospheric circulations. Using a m... more Large wind farms are expected to influence local and regional atmospheric circulations. Using a mesoscale parameterization of the effects of wind farms that includes a momentum sink and a wind speed–dependent source of turbulent kinetic energy, simulations were carried out to quantify the impact of a wind farm on an atmospheric boundary layer throughout a diurnal cycle. The presence of a wind farm covering 10 km × 10 km is found to have a significant impact on the local atmospheric flow and on regions up to 60 km downwind at night. Daytime convective conditions show little impact of the wind farm on wind speeds, as the momentum deficits generated by the wind farm rapidly mix through the depth of the boundary layer. At night, the stable layer within the rotor area inhibits turbulent mixing of the momentum deficit, leading to a shallower wake and a greater reduction in the wind speed within the wake. Although a low-level jet forms at altitudes within the rotor area in the hours before...
ABSTRACT The CASES-97 dataset, supplemented by data from the surrounding area and from satellite,... more ABSTRACT The CASES-97 dataset, supplemented by data from the surrounding area and from satellite, will enable us to isolate the effects of soil moisture on boundary layer evolution.Our initial approach will be to use the integrated dataset to determine (a) the factors that contribute to PBL growth, and (b) the factors that determine the wind, temperature, and wind profiles in the growing PBL. This process will help us to consolidate the dataset and tease out remaining inconsistencies. As soon as reasonable, we want to use the dataset in mesoscale numerical models, to test and refine our conclusions. Further detail on the CASES-97 field program can be found at the World Wide Web site at: http://www.mmm.ucar.edu/cases/cases.html.
Bulletin of the American Meteorological Society, 2000
Page 1. 757 Bulletin of the American Meteorological Society 1. Introduction The Walnut River Wate... more Page 1. 757 Bulletin of the American Meteorological Society 1. Introduction The Walnut River Watershed east of Wichita, Kan-sas, has become the focus of investigations to study the interaction of the lower atmosphere with the land surface, subsurface, and vegetation. ...
Tall wind turbines, with hub heights at 80 m or above, can extract large amounts of energy from t... more Tall wind turbines, with hub heights at 80 m or above, can extract large amounts of energy from the atmosphere because they are likely to encounter higher wind speeds, but they face challenges given the complex nature of wind flow and turbulence at these heights in the boundary layer. Depending on whether the boundary layer is stable, neutral, or convective, the mean wind speed, direction, and turbulence properties may vary greatly across the tall turbine swept area (40 to 120 m AGL). This variability can cause tall turbines to produce difference amounts of power during time periods with identical hub height wind speeds. Using meteorological and power generation data from a West Coast North American wind farm over a one-year period, our study synthesizes standard wind park observations, such as wind speed from turbine nacelles and sparse meteorological tower observations, with high-resolution profiles of wind speed and turbulence from a remote sensing platform, to quantify the impact of atmospheric stability on power output. We first compare approaches to defining atmospheric stability. The standard, limited, wind farm operations enable the calculation only of a wind shear exponent (α) or turbulence intensity (I U ) from cup anemometers, while the presence at this wind farm of a SODAR enables the direct observation of turbulent kinetic energy (TKE) throughout the turbine rotor disk. Additionally, a nearby research meteorological station provided observations of the Obukhov length, L, a direct measure of atmospheric stability. In general, the stability parameters α, I U , and TKE are in high agreement with the more physically-robust L, with TKE exhibiting the best agreement with L. Using these metrics, data periods are segregated by stability class to investigate power performance dependencies. Power output at this wind farm is highly correlated with atmospheric stability during the spring and summer months, while atmospheric stability exerts little impact on power output during the winter and autumn periods.
Atmospheric Measurement Techniques Discussions, 2014
Tall onshore wind turbines, with hub heights between 80 m and 100 m, can extract large amounts of... more Tall onshore wind turbines, with hub heights between 80 m and 100 m, can extract large amounts of energy from the atmosphere since they generally encounter higher wind speeds, but they face challenges given the complexity of boundary layer flows. This complexity of the lowest layers of the atmosphere, where wind turbines reside, has made conventional modeling efforts less than ideal. To meet the nation's goal of increasing wind power into the U.S. electrical grid, the accuracy of wind power forecasts must be improved.
33rd Wind Energy Symposium, 2015
ABSTRACT
The nocturnal low-level jet (LLJ) is a well-documented phenomenon around the world. The LLJ has b... more The nocturnal low-level jet (LLJ) is a well-documented phenomenon around the world. The LLJ has been studied in great detail in the southern Great Plains of the United States (Bonner 1968, Whiteman et al. 1997, Banta et al., 2002, Song et al. 2005), where it efficiently ...
... Robert Banta, W. Alan Brewer, R. Michael Hardesty. National Oceanic and Atmospheric Administr... more ... Robert Banta, W. Alan Brewer, R. Michael Hardesty. National Oceanic and Atmospheric Administration (NOAA) Earth System Research Laboratory ... References: 1. RJ Barthelmie, O. Rathmann, ST Frandsen, KS Hansen, E. Politis, J. Prospathopoulos, K. Rados, Modelling and ...
Boundary layer flows are greatly complicated by the presence of complex terrain which redirects m... more Boundary layer flows are greatly complicated by the presence of complex terrain which redirects mean flow and alters the structure of turbulence. Surface fluxes of heat and moisture provide addi-tional forcing which induce secondary flows, or can dominate flow dynamics in ...
A major objective of CASES-99 was to relate surface fluxes to features of the evolving stable bou... more A major objective of CASES-99 was to relate surface fluxes to features of the evolving stable boundary layer, such as the low-level jet (LLJ). In a recently completed study we used a combination of high-resolution Doppler lidar (HRDL: see Grund et al., 1999), a 60-m instrumented ...
Accurate numerical prediction of airflow and tracer dispersion in urban areas depends, to a great... more Accurate numerical prediction of airflow and tracer dispersion in urban areas depends, to a great extent, on the use of appropriate stability conditions. Due to the lack of relevant field measurements or sufficiently sophisticated turbulence models, modelers often assume that nearly neutral ...