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S D Mayor - One of the best experts on this subject based on the ideXlab platform.
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a comparison of higher order Vertical Velocity moments in the convective boundary layer from lidar with in situ measurements and large eddy simulation
Boundary-Layer Meteorology, 2012Co-Authors: D. H. Lenschow, S D Mayor, Marie Lothon, Peter P Sullivan, Guylaine CanutAbstract:We have analyzed measurements of Vertical Velocity w statistics with the NOAA high resolution Doppler lidar (HRDL) from about 390 m above the surface to the top of the convective boundary layer (CBL) over a relatively flat and uniform agricultural surface during the Lidars-in-Flat-Terrain (LIFT) experiment in 1996. The temporal resolution of the zenith-pointing lidar was about 1 s, and the range-gate resolution about 30 m. Vertical cross-sections of w were used to calculate second- to fourth-moment statistics of w as a function of height throughout most of the CBL. We compare the results with large-eddy simulations (LES) of the CBL and with in situ aircraft measurements. A major cause of the observed case-to-case variability in the Vertical profiles of the higher moments is differences in stability. For example, for the most convective cases, the skewness from both LES and observations changes more with height than for cases with more shear, with the observations changing more with stability than the LES. We also found a decrease in skewness, particularly in the upper part of the CBL, with an increase in LES grid resolution.
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Doppler Lidar Measurements of Vertical Velocity Spectra in the Convective Planetary Boundary Layer
Boundary-Layer Meteorology, 2009Co-Authors: Marie Lothon, D. H. Lenschow, S D MayorAbstract:We utilized a Doppler lidar to measure spectra of Vertical Velocity w from 390m above the surface to the top of the daytime convective boundary layer (CBL). The high resolution 2μm wavelength Doppler lidar developed by the NOAA Environmental Technology Laboratory was used to detect the mean radial Velocity of aerosol particles. It operated continuously during the daytime in the zenith-pointing mode for several days in summer 1996 during the Lidars-in-Flat-Terrain experiment over level farmland in central Illinois, U.S.A. The temporal resolution of the lidar was about 1 s, and the range-gate resolution was about 30m. The Vertical cross-sections were used to calculate spectra as a function of height with unprecedented Vertical resolution throughout much of the CBL, and, in general, we find continuity of the spectral peaks throughout the depth of the CBL. We compare the observed spectra with previous formulations based on both measurements and numerical simulations, and discuss the considerable differences, both on an averaged and a case-by-case basis. We fit the observed spectra to a model that takes into account the wavelength of the spectral peak and the curvature of the spectra across the transition from low wavenumbers to the inertial subrange. The curvature generally is as large or larger than the von Kármán spectra. There is large case-to-case variability, some of which can be linked to the mean structure of the CBL, especially the mean wind and the convective instability. We also find a large case-to-case variability in our estimates of normalized turbulent kinetic energy dissipation deduced from the spectra, likely due for the most part to a varying ratio of entrainment flux to surface flux. Finally, we find a relatively larger contribution to the low wavenumber region of the spectra in cases with smaller shear across the capping inversion, and suggest that this may be due partly to gravity waves in the inversion and overlying free atmosphere.
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Coherence and scale of Vertical Velocity in the convective boundary layer from a Doppler lidar
Boundary-Layer Meteorology, 2006Co-Authors: Marie Lothon, D. H. Lenschow, S D MayorAbstract:We utilized a Doppler lidar to measure integral scale and coherence of Vertical Velocity w in the daytime convective boundary layer (CBL). The high resolution 2 ++m wavelength Doppler lidar developed by the NOAA Environmental Technology Laboratory was used to detect the mean radial Velocity of aerosol particles. It operated continuously in the zenith-pointing mode for several days in the summer 1996 during the “Lidars in Flat Terrain” experiment over level farmland in central Illinois. We calculated profiles of w integral scales in both the alongwind and Vertical directions from about 390 m height to the CBL top. In the middle of the mixed layer we found, from the ratio of the w integral scale in the Vertical to that in the horizontal direction, that the w eddies are squashed by a factor of about 0.65 as compared to what would be the case for isotropic turbulence. Furthermore, there is a significant decrease of the Vertical integral scale with height. The integral scale profiles and Vertical coherence show that Vertical Velocity fluctuations in the CBL have a predictable anisotropic structure. We found no significant tilt of the thermal structures with height in the middle part of the CBL
Marie Lothon - One of the best experts on this subject based on the ideXlab platform.
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a comparison of higher order Vertical Velocity moments in the convective boundary layer from lidar with in situ measurements and large eddy simulation
Boundary-Layer Meteorology, 2012Co-Authors: D. H. Lenschow, S D Mayor, Marie Lothon, Peter P Sullivan, Guylaine CanutAbstract:We have analyzed measurements of Vertical Velocity w statistics with the NOAA high resolution Doppler lidar (HRDL) from about 390 m above the surface to the top of the convective boundary layer (CBL) over a relatively flat and uniform agricultural surface during the Lidars-in-Flat-Terrain (LIFT) experiment in 1996. The temporal resolution of the zenith-pointing lidar was about 1 s, and the range-gate resolution about 30 m. Vertical cross-sections of w were used to calculate second- to fourth-moment statistics of w as a function of height throughout most of the CBL. We compare the results with large-eddy simulations (LES) of the CBL and with in situ aircraft measurements. A major cause of the observed case-to-case variability in the Vertical profiles of the higher moments is differences in stability. For example, for the most convective cases, the skewness from both LES and observations changes more with height than for cases with more shear, with the observations changing more with stability than the LES. We also found a decrease in skewness, particularly in the upper part of the CBL, with an increase in LES grid resolution.
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Doppler Lidar Measurements of Vertical Velocity Spectra in the Convective Planetary Boundary Layer
Boundary-Layer Meteorology, 2009Co-Authors: Marie Lothon, D. H. Lenschow, S D MayorAbstract:We utilized a Doppler lidar to measure spectra of Vertical Velocity w from 390m above the surface to the top of the daytime convective boundary layer (CBL). The high resolution 2μm wavelength Doppler lidar developed by the NOAA Environmental Technology Laboratory was used to detect the mean radial Velocity of aerosol particles. It operated continuously during the daytime in the zenith-pointing mode for several days in summer 1996 during the Lidars-in-Flat-Terrain experiment over level farmland in central Illinois, U.S.A. The temporal resolution of the lidar was about 1 s, and the range-gate resolution was about 30m. The Vertical cross-sections were used to calculate spectra as a function of height with unprecedented Vertical resolution throughout much of the CBL, and, in general, we find continuity of the spectral peaks throughout the depth of the CBL. We compare the observed spectra with previous formulations based on both measurements and numerical simulations, and discuss the considerable differences, both on an averaged and a case-by-case basis. We fit the observed spectra to a model that takes into account the wavelength of the spectral peak and the curvature of the spectra across the transition from low wavenumbers to the inertial subrange. The curvature generally is as large or larger than the von Kármán spectra. There is large case-to-case variability, some of which can be linked to the mean structure of the CBL, especially the mean wind and the convective instability. We also find a large case-to-case variability in our estimates of normalized turbulent kinetic energy dissipation deduced from the spectra, likely due for the most part to a varying ratio of entrainment flux to surface flux. Finally, we find a relatively larger contribution to the low wavenumber region of the spectra in cases with smaller shear across the capping inversion, and suggest that this may be due partly to gravity waves in the inversion and overlying free atmosphere.
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Coherence and scale of Vertical Velocity in the convective boundary layer from a Doppler lidar
Boundary-Layer Meteorology, 2006Co-Authors: Marie Lothon, D. H. Lenschow, S D MayorAbstract:We utilized a Doppler lidar to measure integral scale and coherence of Vertical Velocity w in the daytime convective boundary layer (CBL). The high resolution 2 ++m wavelength Doppler lidar developed by the NOAA Environmental Technology Laboratory was used to detect the mean radial Velocity of aerosol particles. It operated continuously in the zenith-pointing mode for several days in the summer 1996 during the “Lidars in Flat Terrain” experiment over level farmland in central Illinois. We calculated profiles of w integral scales in both the alongwind and Vertical directions from about 390 m height to the CBL top. In the middle of the mixed layer we found, from the ratio of the w integral scale in the Vertical to that in the horizontal direction, that the w eddies are squashed by a factor of about 0.65 as compared to what would be the case for isotropic turbulence. Furthermore, there is a significant decrease of the Vertical integral scale with height. The integral scale profiles and Vertical coherence show that Vertical Velocity fluctuations in the CBL have a predictable anisotropic structure. We found no significant tilt of the thermal structures with height in the middle part of the CBL
D. H. Lenschow - One of the best experts on this subject based on the ideXlab platform.
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a comparison of higher order Vertical Velocity moments in the convective boundary layer from lidar with in situ measurements and large eddy simulation
Boundary-Layer Meteorology, 2012Co-Authors: D. H. Lenschow, S D Mayor, Marie Lothon, Peter P Sullivan, Guylaine CanutAbstract:We have analyzed measurements of Vertical Velocity w statistics with the NOAA high resolution Doppler lidar (HRDL) from about 390 m above the surface to the top of the convective boundary layer (CBL) over a relatively flat and uniform agricultural surface during the Lidars-in-Flat-Terrain (LIFT) experiment in 1996. The temporal resolution of the zenith-pointing lidar was about 1 s, and the range-gate resolution about 30 m. Vertical cross-sections of w were used to calculate second- to fourth-moment statistics of w as a function of height throughout most of the CBL. We compare the results with large-eddy simulations (LES) of the CBL and with in situ aircraft measurements. A major cause of the observed case-to-case variability in the Vertical profiles of the higher moments is differences in stability. For example, for the most convective cases, the skewness from both LES and observations changes more with height than for cases with more shear, with the observations changing more with stability than the LES. We also found a decrease in skewness, particularly in the upper part of the CBL, with an increase in LES grid resolution.
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Doppler Lidar Measurements of Vertical Velocity Spectra in the Convective Planetary Boundary Layer
Boundary-Layer Meteorology, 2009Co-Authors: Marie Lothon, D. H. Lenschow, S D MayorAbstract:We utilized a Doppler lidar to measure spectra of Vertical Velocity w from 390m above the surface to the top of the daytime convective boundary layer (CBL). The high resolution 2μm wavelength Doppler lidar developed by the NOAA Environmental Technology Laboratory was used to detect the mean radial Velocity of aerosol particles. It operated continuously during the daytime in the zenith-pointing mode for several days in summer 1996 during the Lidars-in-Flat-Terrain experiment over level farmland in central Illinois, U.S.A. The temporal resolution of the lidar was about 1 s, and the range-gate resolution was about 30m. The Vertical cross-sections were used to calculate spectra as a function of height with unprecedented Vertical resolution throughout much of the CBL, and, in general, we find continuity of the spectral peaks throughout the depth of the CBL. We compare the observed spectra with previous formulations based on both measurements and numerical simulations, and discuss the considerable differences, both on an averaged and a case-by-case basis. We fit the observed spectra to a model that takes into account the wavelength of the spectral peak and the curvature of the spectra across the transition from low wavenumbers to the inertial subrange. The curvature generally is as large or larger than the von Kármán spectra. There is large case-to-case variability, some of which can be linked to the mean structure of the CBL, especially the mean wind and the convective instability. We also find a large case-to-case variability in our estimates of normalized turbulent kinetic energy dissipation deduced from the spectra, likely due for the most part to a varying ratio of entrainment flux to surface flux. Finally, we find a relatively larger contribution to the low wavenumber region of the spectra in cases with smaller shear across the capping inversion, and suggest that this may be due partly to gravity waves in the inversion and overlying free atmosphere.
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Coherence and scale of Vertical Velocity in the convective boundary layer from a Doppler lidar
Boundary-Layer Meteorology, 2006Co-Authors: Marie Lothon, D. H. Lenschow, S D MayorAbstract:We utilized a Doppler lidar to measure integral scale and coherence of Vertical Velocity w in the daytime convective boundary layer (CBL). The high resolution 2 ++m wavelength Doppler lidar developed by the NOAA Environmental Technology Laboratory was used to detect the mean radial Velocity of aerosol particles. It operated continuously in the zenith-pointing mode for several days in the summer 1996 during the “Lidars in Flat Terrain” experiment over level farmland in central Illinois. We calculated profiles of w integral scales in both the alongwind and Vertical directions from about 390 m height to the CBL top. In the middle of the mixed layer we found, from the ratio of the w integral scale in the Vertical to that in the horizontal direction, that the w eddies are squashed by a factor of about 0.65 as compared to what would be the case for isotropic turbulence. Furthermore, there is a significant decrease of the Vertical integral scale with height. The integral scale profiles and Vertical coherence show that Vertical Velocity fluctuations in the CBL have a predictable anisotropic structure. We found no significant tilt of the thermal structures with height in the middle part of the CBL
R. Müller - One of the best experts on this subject based on the ideXlab platform.
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Kinematic and diabatic Vertical Velocity climatologies from a chemistry climate model
Atmospheric Chemistry and Physics Discussions, 2015Co-Authors: C. M. Hoppe, F. Ploeger, P. Konopka, R. MüllerAbstract:Abstract. The representation of Vertical Velocity in chemistry climate models is a key element for the representation of the large scale Brewer–Dobson-Circulation in the stratosphere. Here, we diagnose and compare the kinematic and diabatic Vertical velocities in the ECHAM/Messy Atmospheric Chemistry (EMAC) model. The calculation of kinematic Vertical Velocity is based on the continuity equation, whereas diabatic Vertical Velocity is computed using diabatic heating rates. Annual and monthly zonal mean climatologies of Vertical Velocity from a 10 year simulation are provided for both, kinematic and diabatic Vertical Velocity representations. In general, both Vertical Velocity patterns show the main features of the stratospheric circulation, namely upwelling at low latitudes and downwelling at high latitudes. The main difference in the Vertical Velocity pattern is a more uniform structure for diabatic and a noisier structure for kinematic Vertical Velocity. Diabatic Vertical velocities show higher absolute values both in the upwelling branch in the inner tropics and in the downwelling regions in the polar vortices. Further, there is a latitudinal shift of the tropical upwelling branch in boreal summer between the two Vertical Velocity representations with the tropical upwelling region in the diabatic representation shifted southward compared to the kinematic case. Furthermore, we present mean age of air climatologies from two transport schemes in EMAC using these different Vertical velocities. The age of air distributions show a hemispheric difference pattern in the stratosphere with younger air in the Southern Hemisphere and older air in the Northern Hemisphere using the transport scheme with diabatic Vertical velocities. Further, the age of air climatology from the transport scheme using diabatic Vertical velocities shows younger mean age of air in the inner tropical upwelling branch and older mean age in the extratopical tropopause region.
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Kinematic and diabatic Vertical Velocity climatologies from a chemistry climate model
Atmospheric Chemistry and Physics, 2015Co-Authors: Charlotte Hoppe, F. Ploeger, P. Konopka, R. MüllerAbstract:Abstract. The representation of Vertical Velocity in chemistry climate models is a key element for the representation of the large-scale Brewer–Dobson circulation in the stratosphere. Here, we diagnose and compare the kinematic and diabatic Vertical velocities in the ECHAM/Modular Earth Submodel System (MESSy) Atmospheric Chemistry (EMAC) model. The calculation of kinematic Vertical Velocity is based on the continuity equation, whereas diabatic Vertical Velocity is computed using diabatic heating rates. Annual and monthly zonal mean climatologies of Vertical Velocity from a 10-year simulation are provided for both kinematic and diabatic Vertical Velocity representations. In general, both Vertical Velocity patterns show the main features of the stratospheric circulation, namely, upwelling at low latitudes and downwelling at high latitudes. The main difference in the Vertical Velocity pattern is a more uniform structure for diabatic and a noisier structure for kinematic Vertical Velocity. Diabatic Vertical velocities show higher absolute values both in the upwelling branch in the inner tropics and in the downwelling regions in the polar vortices. Further, there is a latitudinal shift of the tropical upwelling branch in boreal summer between the two Vertical Velocity representations with the tropical upwelling region in the diabatic representation shifted southward compared to the kinematic case. Furthermore, we present mean age of air climatologies from two transport schemes in EMAC using these different Vertical velocities and analyze the impact of residual circulation and mixing processes on the age of air. The age of air distributions show a hemispheric difference pattern in the stratosphere with younger air in the Southern Hemisphere and older air in the Northern Hemisphere using the transport scheme with diabatic Vertical velocities. Further, the age of air climatology from the transport scheme using diabatic Vertical velocities shows a younger mean age of air in the inner tropical upwelling branch and an older mean age in the extratropical tropopause region.
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impact of the Vertical Velocity scheme on modeling transport in the tropical tropopause layer
Journal of Geophysical Research, 2010Co-Authors: F. Ploeger, P Konopka, G Gunther, J U Groos, R. MüllerAbstract:[1] To assess the impact of the Vertical Velocity scheme on modeling transport in the tropical tropopause layer (TTL), 3 month backward trajectories are initialized in the TTL for boreal winter and summer 2002. The calculations are done in either a kinematic scenario with pressure tendency as the Vertical Velocity or in a diabatic scenario with cross-isentropic Velocity deduced from various diabatic heating rates due to radiation (clear sky, all sky) and latent, diffusive and turbulent heating. This work provides a guideline for assessing the sensitivity of trajectory and chemical transport model (CTM) results on the choice of the Vertical Velocity scheme. We find that many transport characteristics, such as time scales, pathways and dispersion, crucially depend on the Vertical Velocity scheme. The strongest tropical upwelling results from the operational European Centre for Medium-Range Weather Forecasts kinematic scenario with the time scale for ascending from 340 to 400 K of 1 month. For the ERA-Interim kinematic and total diabatic scenarios, this time scale is about 2 months, and for the all-sky scenario it is as long as 2.5 months. In a diabatic scenario, the whole TTL exhibits mean upward motion, whereas in a kinematic scenario, regions of subsidence occur in the upper TTL. However, some transport characteristics robustly emerge from the different scenarios, such as an enhancement of residence times between 350 and 380 K and a strong impact of meridional in-mixing from the extratropics on the composition of the TTL. Moreover, an increase of meridionally transported air from the summer hemisphere into the TTL (maximum for boreal summer) is found as an invariant feature among all the scenarios.
David M Romps - One of the best experts on this subject based on the ideXlab platform.
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reconciling differences between large eddy simulations and doppler lidar observations of continental shallow cumulus cloud base Vertical Velocity
Geophysical Research Letters, 2019Co-Authors: Satoshi Endo, Andrew M. Vogelmann, Damao Zhang, Pavlos Kollias, Katia Lamer, Heng Xiao, William I Gustafson, David M RompsAbstract:Author(s): Endo, S; Zhang, D; Vogelmann, AM; Kollias, P; Lamer, K; Oue, M; Xiao, H; Gustafson, WI; Romps, DM | Abstract: ©2019. American Geophysical Union. All Rights Reserved. We investigate a significant model-observation difference found between cloud-base Vertical Velocity for continental shallow cumulus simulated using large-eddy simulations (LES) and observed by Doppler lidar measurements over the U.S. Southern Great Plains Atmospheric Radiation Measurement Facility. The LES cloud-base Vertical Velocity is dominated by updrafts that are consistent with a general picture for convective clouds but is inconsistent with Doppler lidar observations that also show the presence of considerable downdrafts. The underestimation of simulated downdrafts is found to be a robust feature, being insensitive to various numerical, physical, or dynamical choices. We find that simulations can more closely reproduce observations only after improving the model physics to use size-resolved microphysics and horizontal longwave radiation, both of which modify the cloud buoyancy and Velocity structure near cloud side edges. The results suggest that treatments that capture these structures are needed for the proper simulation and subsequent parameterization development of shallow cumulus Vertical transport.
