scholarly journals Convective Boundary Layer Depth Estimation from S-Band Dual-Polarization Radar

2018 ◽  
Vol 35 (8) ◽  
pp. 1723-1733 ◽  
Author(s):  
John R. Banghoff ◽  
David J. Stensrud ◽  
Matthew R. Kumjian
Keyword(s):  
Boundary Layer ◽  
New York ◽  
Convective Boundary Layer ◽  
Depth Estimation ◽  
Dual Polarization ◽  
Layer Depth ◽  
Reasonable Estimate ◽  
Convective Boundary ◽  
Using Data ◽  
Differential Reflectivity

AbstractThis study investigates Bragg scatter signatures in dual-polarization radar observations, which are defined by low differential reflectivity values, as a proxy for convective boundary layer (CBL) depth. Using data from the WSR-88D in Twin Lakes, Oklahoma (KTLX), local minima in quasi-vertical profiles of are found to provide a reasonable estimate of CBL depth when compared with depth estimates from upper-air soundings from Norman, Oklahoma (KOUN), during 2014. The 243 Bragg scatter and upper-air sounding CBL depth estimates have a correlation of 0.90 and an RMSE of 254 m. Using Bragg scatter as a proxy for CBL depth was expanded to other seasons and locations—performing well in Wilmington, Ohio; Fairbanks, Alaska; Tucson, Arizona; Minneapolis, Minnesota; Albany, New York; Portland, Oregon; and Tampa, Florida—showing its potential usefulness in monitoring CBL depth throughout the year in a variety of geographic locations and meteorological conditions.

Marginal Stability of the Convective Boundary Layer

2020 ◽  
Vol 77 (2) ◽  
pp. 435-442
Author(s):  
John Thuburn ◽  
Georgios A. Efstathiou
Keyword(s):  
Boundary Layer ◽  
Stability Analysis ◽  
Linear Stability Analysis ◽  
Convective Boundary Layer ◽  
Eddy Viscosity ◽  
Potential Temperature ◽  
Marginal Stability ◽  
Layer Depth ◽  
Convective Boundary ◽  
Layer Potential

Abstract We hypothesize that the convective atmospheric boundary layer is marginally stable when the damping effects of turbulence are taken into account. If the effects of turbulence are modeled as an eddy viscosity and diffusivity, then an idealized analysis based on the hypothesis predicts a well-known scaling for the magnitude of the eddy viscosity and diffusivity. It also predicts that the marginally stable modes should have vertical and horizontal scales comparable to the boundary layer depth. A more quantitative numerical linear stability analysis is presented for a realistic convective boundary layer potential temperature profile and is found to support the hypothesis.

scholarly journals Bragg Scatter Detection by the WSR-88D. Part I: Algorithm Development

2017 ◽  
Vol 34 (3) ◽  
pp. 465-478 ◽  
Author(s):  
Lindsey M. Richardson ◽  
Jeffrey G. Cunningham ◽  
W. David Zittel ◽  
Robert R. Lee ◽  
Richard L. Ice ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Relative Humidity ◽  
Richardson Number ◽  
Automated Detection ◽  
Dual Polarization ◽  
Convective Boundary ◽  
Ground Clutter ◽  
Radar Calibration ◽  
Visual Confirmation ◽  
Differential Reflectivity

AbstractStudies have shown that echo returns from clear-air Bragg scatter (CABS) can be used to detect the height of the convective boundary layer and to assess the systematic differential reflectivity (ZDR) bias for a radar site. However, these studies did not use data from operational Weather Surveillance Radar-1988 Doppler (WSR-88D) or data from a large variety of sites. A new algorithm to automatically detect CABS from any operational WSR-88D with dual-polarization capability while excluding contamination from precipitation, biota, and ground clutter is presented here. Visual confirmation and tests related to the sounding parameters’ relative humidity slope, refractivity gradient, and gradient Richardson number are used to assess the algorithm. Results show that automated detection of CABS in operational WSR-88D data gives useful ZDR bias information while omitting the majority of contaminated cases. Such an algorithm holds potential for radar calibration efforts and Bragg scatter studies in general.

scholarly journals Structures of Bragg Scatter Observed with the Polarimetric WSR-88D

2013 ◽  
Vol 30 (7) ◽  
pp. 1253-1258 ◽  
Author(s):  
Valery M. Melnikov ◽  
Richard J. Doviak ◽  
Dusan S. Zrnić ◽  
David J. Stensrud
Keyword(s):  
Boundary Layer ◽  
Signal Processing ◽  
Data Collection ◽  
Convective Boundary Layer ◽  
Dual Polarization ◽  
Detection Capability ◽  
Convective Boundary ◽  
Boundary Layer Turbulence ◽  
Fine Structures

Abstract Enhancements to signal processing and data collection in the dual-polarization Weather Surveillance Radar-1988 Doppler (WSR-88D) to increase its detection capability yield observations of “fine” structures from Bragg scatterers. Several types of the fine structures observed in and above the boundary layer are discussed. These Bragg scatter structures include the top of the convective boundary layer, nonprecipitating clouds, strong convective plumes above the boundary layer, and a layer of weak reflections associated with decaying boundary layer turbulence. A conclusion that data from polarimetric WSR-88Ds can be used to obtain the depth of the convective boundary layer is made.

scholarly journals Using WSR-88D Data and Insolation Estimates to Determine Convective Boundary Layer Depth

2012 ◽  
Vol 29 (4) ◽  
pp. 581-588 ◽  
Author(s):  
Kimberly L. Elmore ◽  
Pamela L. Heinselman ◽  
David J. Stensrud
Keyword(s):  
Boundary Layer ◽  
Convective Boundary Layer ◽  
Radar Reflectivity ◽  
Layer Depth ◽  
Convective Boundary ◽  
Clear Sky ◽  
Testing Dataset ◽  
Human Interpretation ◽  
The One ◽  
Linear Regressions

Abstract Prior work shows that Weather Surveillance Radar-1988 Doppler (WSR-88D) clear-air reflectivity can be used to determine convective boundary layer (CBL) depth. Based on that work, two simple linear regressions are developed that provide CBL depth. One requires only clear-air radar reflectivity from a single 4.5° elevation scan, whereas the other additionally requires the total, clear-sky insolation at the radar site, derived from the radar location and local time. Because only the most recent radar scan is used, the CBL depth can, in principle, be computed for every scan. The “true” CBL depth used to develop the models is based on human interpretation of the 915-MHz profiler data. The regressions presented in this work are developed using 17 summer days near Norman, Oklahoma, that have been previously investigated. The resulting equations and algorithms are applied to a testing dataset consisting of 7 days not previously analyzed. Though the regression using insolation estimates performs best, errors from both models are on the order of the expected error of the profiler-estimated CBL depth values. Of the two regressions, the one that uses insolation yields CBL depth estimates with an RMSE of 208 m, while the regression with only clear-air radar reflectivity yields CBL depth estimates with an RMSE of 330 m.

scholarly journals Convective Boundary Layer Depth Estimation from Wind Profilers: Statistical Comparison between an Automated Algorithm and Expert Estimations

2008 ◽  
Vol 25 (8) ◽  
pp. 1397-1413 ◽  
Author(s):  
Laura Bianco ◽  
James M. Wilczak ◽  
Allen B. White
Keyword(s):  
Boundary Layer ◽  
Fuzzy Logic ◽  
Vertical Velocity ◽  
Convective Boundary Layer ◽  
Index Structure ◽  
Small Scale ◽  
Vertical Profiles ◽  
Improved Method ◽  
Layer Depth ◽  
Convective Boundary

Abstract A previous study showed success in determining the convective boundary layer depth with radar wind-profiling radars using fuzzy logic methods, and improvements to the earlier work are discussed. The improved method uses the Vaisala multipeak picking (MPP) procedure to identify the atmospheric signal in radar spectra in place of a fuzzy logic peak picking procedure that was previously used. The method then applies fuzzy logic techniques to calculate the depth of the convective boundary layer. The planetary boundary layer depth algorithm is improved with respect to the one used in the previous study in that it adds information obtained from the small-scale turbulence (vertical profiles of the spectral width of the vertical velocity), while also still using vertical profiles of the radar-derived refractive index structure parameter C2n and the variance of vertical velocity. Modifications to the fuzzy logic rules (especially to those using vertical velocity data) that improve the algorithm’s accuracy in cloudy boundary layers are incorporated. In addition, a reliability threshold value to the fuzzy logic–derived score is applied to eliminate PBL depth data values with low score values. These low score values correspond to periods when the PBL structure does not match the conceptual model of the convective PBL built into the algorithm. Also, as a final step, an optional temporal continuity test on boundary layer depth has been developed that helps improve the algorithm’s skill. A comparison with independent boundary layer depth estimations made “by eye” by meteorologists at two radar wind-profiler sites, significantly different in their characteristics, shows that the new improved method gives significantly more accurate estimates of the boundary layer depth than does the previous method, and also much better estimates than the simpler “standard” method of selecting the peak of C2n. The new method produces an absolute error of the mixing-depth estimates comparable to the vertical range resolution of the profilers.

scholarly journals Analysis of the simulation of the PALM model for the Convective Boundary Layer in the Amazon (GOAMAZON 2014/5)

2020 ◽  
Vol 42 ◽  
pp. e38
Author(s):  
Rayonil Gomes Carneiro ◽  
Camilla Kassar Borges ◽  
Alice Henkes ◽  
Gilberto Fisch
Keyword(s):  
Boundary Layer ◽  
Convective Boundary Layer ◽  
Amazon Region ◽  
Convective Boundary ◽  
Large Eddy Simulation Model ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Flux Profile ◽  
Using Data ◽  
Convective Layer

The present work had the objective to evaluate the development of the convective boundary layer in the Amazon region simulated by a high resolution Large Eddy Simulation model (named PALM model), for days representative for rainy and dry seasons. The study used data from the GOAmazon Project 2014/2015 (Green Ocean Amazon). Using data from radiosondes and Ceilometer as truth values, they were compared with the simulations performed through the PALM model. The results showed that, in general, the convective boundary layer cycle for the Amazon region was well represented by PALM model. It´s outputs has showed an overestimation of ≈ 35 m in a rainy day and an underestimation of ≈ 20 m in a dry day, both in development phase of the convective layer at late morning. It was also observed that the latent heat flux profile was higher than the sensible heat in the atmosphere, because it is a region with a lot of humidity, with the boundary layer responding rapidly to the maximum surface forcing.

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