Precipitation Identification from Radar Wind Profiler Spectral Moment Data: Vertical Velocity Histograms, Velocity Variance, and Signal Power–Vertical Velocity Correlations

Abstract Observations made at the Atmospheric Radiation Measurement (ARM) Program’s Southern Great Plains (SGP) site during uniform nonprecipitating stratocumulus cloud conditions for a 14-h period are used to examine cloud-top entrainment processes and parameterizations. The observations from a vertically pointing Doppler cloud radar provide estimates of vertical velocity variance and energy dissipation rate (EDR) terms in the parameterized turbulent kinetic energy (TKE) budget of the entrainment zone. Hourly averages of the vertical velocity variance term in the TKE entrainment formulation correlated strongly (r = 0.72) with the dissipation rate term in the entrainment zone, with an increased correlation (r = 0.92) when accounting for the nighttime decoupling of the boundary layer. Independent estimates of entrainment rates were obtained from an inversion-height budget using the local time derivative and horizontal advection of cloud-top height together with large-scale vertical velocity at the boundary layer inversion from the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis model. The mean entrainment rate from the inversion-height budget during the 14-h period was 0.74 ± 0.15 cm s−1 and was used to calculate bulk coefficients for entrainment parameterizations based on convective velocity scale w* and TKE budgets of the entrainment zone. The hourly values of entrainment rates calculated using these coefficients exhibited good agreement with those calculated from the inversion-height budget associated with substantial changes in surface buoyancy production and cloud-top radiative cooling. The results indicate a strong potential for making entrainment rate estimates directly from radar vertical velocity variance and the EDR measurements.

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Evaluation of Wind Profiler Vertical Velocity Variances

10.5194/amt-2016-299-rc2 ◽

2016 ◽

Author(s):

Stefan Emeis

Keyword(s):

Vertical Velocity ◽

Wind Profiler ◽

Velocity Variances

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How weather events modify aerosol particle size distributions in the Amazon boundary layer

10.5194/acp-2021-314 ◽

2021 ◽

Author(s):

Luiz Augusto Toledo Machado ◽

Marco A. Franco ◽

Leslie A. Kremper ◽

Florian Ditas ◽

Meinrat O. Andreae ◽

...

Keyword(s):

Particle Size ◽

Vertical Velocity ◽

Ultrafine Particles ◽

Rain Rate ◽

Early Morning ◽

Lightning Activity ◽

Wind Profiler ◽

Cloud Liquid Water ◽

Weather Events ◽

Aerosol Particle Size

Abstract. This study evaluates the effect of weather events on the aerosol particle size distribution (PSD) at the Amazon Tall Tower Observatory (ATTO). This research combines in-situ measurements of PSD and remote sensing data of lightning density, brightness temperature, cloud top height, cloud liquid water, and rain rate and vertical velocity. Measurements were obtained by a scanning mobility particle sizers (SMPS), the new generation of GOES satellites (GOES-16), the SIPAM S-band radar, and the LAP 3000 radar wind profiler recently installed at the ATTO-Campina site. The combined data allow exploring changes in PSD due to different meteorological processes. The average diurnal cycle shows a higher abundance of ultrafine particles (NUFP) in the early morning, which is coupled with lower concentrations in Aitken (NAIT) and accumulation (NACC) mode particles. From the early morning to the middle of the afternoon, an inverse behavior is observed, where NUFP decreases and NAIT and NACC increase, reflecting a typical particle growth process. Composite figures show an increase of NUFP before, during, and after lightning was detected by the satellite above ATTO. These findings strongly indicate a close relationship between vertical transport and deep convective clouds. Lightning density is connected with a large increase in NUFP, beginning approximately 100 minutes before the maximum lightning density and reaching peak values around 200 minutes later. In addition, the removal of NACC by convective transport was found. Both the increase in NUFP and the decrease in NACC appear in parallel with the increasing intensity of lightning activity. The NUFP increases exponentially with the thunderstorm intensity. In contrast, NAIT and NACC show a different behavior, decreasing from approximately 100 minutes before the maximum lightning activity and reaching a minimum at the time of maximum lightning activity. The effect of cloud top height, cloud liquid water, and rain rate shows the same behavior, but with different patterns among seasons. The convective processes do not occur continually but are modulated by gravity waves in the range of 1 to 5 hours, creating a complex mechanism of interaction with a succession of updrafts and downdrafts, clouds and clear sky situations. The radar wind profiler measured the vertical distribution of the vertical velocity. These profiles show that downdrafts are mainly located below 10 km, while aircraft observations during the ACRIDICON-CHUVA campaign had shown maximum concentrations of ultrafine particles mainly above 10 km. Our study opens new scientific questions to be evaluated in order to understand the intricate physical and chemical mechanisms involved in the production of new particles in Amazonia.

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Combined vertical-velocity observations with Doppler lidar, cloud radar and wind profiler

Atmospheric Measurement Techniques ◽

10.5194/amt-8-3527-2015 ◽

2015 ◽

Vol 8 (8) ◽

pp. 3527-3536 ◽

Cited By ~ 9

Author(s):

J. Bühl ◽

R. Leinweber ◽

U. Görsdorf ◽

M. Radenz ◽

A. Ansmann ◽

...

Keyword(s):

Vertical Velocity ◽

Wind Profiler ◽

Doppler Lidar ◽

Velocity Measurements ◽

Fall Velocity ◽

Cloud Radar ◽

Meteorological Observatory ◽

Comprehensive Classification ◽

Single Instrument ◽

Simultaneous Sensing

Abstract. Case studies of combined vertical-velocity measurements of Doppler lidar, cloud radar and wind profiler are presented. The measurements were taken at the Meteorological Observatory, Lindenberg, Germany. Synergistic products are presented that are derived from the vertical-velocity measurements of the three instruments: a comprehensive classification mask of vertically moving atmospheric targets and the terminal fall velocity of water droplets and ice crystals corrected for vertical air motion. It is shown that this combination of instruments can up-value the measurement values of each single instrument and may allow the simultaneous sensing of atmospheric targets and the motion of clear air.

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Turbulence Process Domination under the Combined Forcings of Wind Stress, the Langmuir Vortex Force, and Surface Cooling

Journal of Physical Oceanography ◽

10.1175/jpo-d-13-021.1 ◽

2014 ◽

Vol 44 (1) ◽

pp. 44-67 ◽

Cited By ~ 21

Author(s):

A. E. Gargett ◽

C. E. Grosch

Keyword(s):

Boundary Layer ◽

Wind Stress ◽

Vertical Velocity ◽

Ocean Surface ◽

The Other ◽

Surface Boundary ◽

Langmuir Circulation ◽

Surface Cooling ◽

Wide Range ◽

Velocity Variance

Abstract Turbulence in the ocean surface layer is generated by time-varying combinations of destabilizing surface buoyancy flux, wind stress forcing, and wave forcing through a vortex force associated with the surface wave field. Observations of time- and depth-averaged vertical velocity variance of full-depth turbulence in shallow unstratified water columns under destabilizing buoyancy forcing are used to determine when process domination can be assigned over a wide range of mixed forcings. The properties of two turbulence archetypes, one representing full-depth Langmuir circulations and the other representing full-depth convection, are described in detail. It is demonstrated that these archetypes lie in distinct regions of the plane of , where and are Langmuir and Rayleigh numbers, respectively, derived from scaling with surface stress velocity and a time scale characteristic of the growth of Langmuir circulation , where and are mean and Stokes velocities, respectively. Situations in which neither process dominates lie between the two end members, with relative dominance given by proximity to one or the other. Cases dominated by direct stress forcing are conspicuous by their absence. In cases of Langmuir domination, surface Stokes velocity is linearly related to , making it impossible to differentiate between scaling depth-averaged vertical velocity variance with , and any other scaling involving both and . A third nondimensional parameter is introduced and used to assess the importance of bottom boundary layer turbulence in a depth-limited system. Questions of time dependence and applicability of results to the open ocean surface boundary layer are considered.

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Wind-profiler observations of gravity waves produced by convection at mid-latitudes

Atmospheric Chemistry and Physics ◽

10.5194/acp-6-2825-2006 ◽

2006 ◽

Vol 6 (10) ◽

pp. 2825-2836 ◽

Cited By ~ 8

Author(s):

Y. G. Choi ◽

S. C. Lee ◽

A. J. McDonald ◽

D. A. Hooper

Keyword(s):

Gravity Waves ◽

Vertical Velocity ◽

Small Scale ◽

Wind Profiler ◽

Convective Activity ◽

Velocity Fluctuations ◽

Short Period ◽

Horizontal Momentum ◽

Scale Inhomogeneity

Abstract. This work presents a case study which includes regions of large rapidly varying vertical velocities observed by a VHF wind-profiler at Aberystwyth (52.4° N, 4.1° W). Analysis indicates that this region is associated with gravity waves above the tropopause level and simultaneous regions of convective activity below the tropopause level. This case study also suggests that convective activity can be identified effectively by finding periods of large uncertainties on the derived velocities. These regions are hypothesized to be related to regions of small-scale inhomogeneity in the wind field. Examination suggests that the large vertical velocity fluctuations above these convective regions are short period gravity wave packets as expected from theory. In addition the vertical flux of the horizontal momentum associated with the gravity waves also displays the pattern of reversal observed in previous studies.

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Turbulence and Radiation in Stratocumulus-Topped Marine Boundary Layers: A Case Study from VOCALS-REx

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-12-0225.1 ◽

2014 ◽

Vol 53 (1) ◽

pp. 117-135 ◽

Cited By ~ 20

Author(s):

Virendra P. Ghate ◽

Bruce A. Albrecht ◽

Mark A. Miller ◽

Alan Brewer ◽

Christopher W. Fairall

Keyword(s):

Vertical Velocity ◽

Marine Boundary Layer ◽

Velocity Structure ◽

Radiative Flux ◽

Radiative Cooling ◽

Flux Divergence ◽

A Value ◽

Velocity Variance ◽

Velocity Scale ◽

Surface Buoyancy

AbstractObservations made during a 24-h period as part of the Variability of the American Monsoon Systems (VAMOS) Ocean–Cloud–Atmosphere–Land Study Regional Experiment (VOCALS-REx) are analyzed to study the radiation and turbulence associated with the stratocumulus-topped marine boundary layer (BL). The first 14 h exhibited a well-mixed (coupled) BL with an average cloud-top radiative flux divergence of ~130 W m−2; the BL was decoupled during the last 10 h with negligible radiative flux divergence. The averaged radiative cooling very close to the cloud top was −9.04 K h−1 in coupled conditions and −3.85 K h−1 in decoupled conditions. This is the first study that combined data from a vertically pointing Doppler cloud radar and a Doppler lidar to yield the vertical velocity structure of the entire BL. The averaged vertical velocity variance and updraft mass flux during coupled conditions were higher than those during decoupled conditions at all levels by a factor of 2 or more. The vertical velocity skewness was negative in the entire BL during coupled conditions, whereas it was weakly positive in the lower third of the BL and negative above during decoupled conditions. A formulation of velocity scale is proposed that includes the effect of cloud-top radiative cooling in addition to the surface buoyancy flux. When scaled by the velocity scale, the vertical velocity variance and coherent downdrafts had similar magnitude during the coupled and decoupled conditions. The coherent updrafts that exhibited a constant profile in the entire BL during both the coupled and decoupled conditions scaled well with the convective velocity scale to a value of ~0.5.

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Vertical Velocity Variance Measurements from Wind Profiling Radars

10.5194/amt-2016-299 ◽

2016 ◽

Cited By ~ 1

Author(s):

Katherine McCaffrey ◽

Laura Bianco ◽

Paul Johnston ◽

James M. Wilczak

Keyword(s):

Boundary Layer ◽

Time Series ◽

Planetary Boundary Layer ◽

Vertical Velocity ◽

Prediction Models ◽

Weather Prediction ◽

Small Scale ◽

Stable Conditions ◽

Sonic Anemometers ◽

Velocity Variance

Abstract. Observations of turbulence in the planetary boundary layer are critical for developing and evaluating boundary layer parameterizations in mesoscale numerical weather prediction models. These observations, however, are expensive, and rarely profile the entire boundary layer. Using optimized configurations for 449 MHz and 915 MHz wind profiling radars during the eXperimental Planetary boundary layer Instrumentation Assessment, improvements have been made to the historical methods of measuring vertical velocity variance through the time series of vertical velocity, as well as the Doppler spectral width. Using six heights of sonic anemometers mounted on a 300-m tower, correlations of up to R2 = 0.74 are seen in measurements of the large-scale variances from the radar time series, and R2 = 0.79 in measurements of small-scale variance from radar spectral widths. The total variance, measured as the sum of the small- and large-scales agrees well with sonic anemometers, with R2 = 0.79. Correlation is higher in daytime, convective boundary layers than nighttime, stable conditions when turbulence levels are smaller. With the good agreement with the in situ measurements, highly-resolved profiles up to 2 km can be accurately observed from the 449 MHz radar, and 1 km from the 915 MHz radar. This optimized configuration will provide unique observations for the verification and improvement to boundary layer parameterizations in mesoscale models.

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