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| 29 Jul 2025
Boundary layer structure and parameterization uncertainties affecting wind turbine hub-height predictions: A comparative assessment of New England and Florida
Abstract. As wind energy development expands to diverse geographical regions, understanding the complex atmospheric conditions that turbines encounter is essential for accurate resource assessment and operational forecasting. This study presents an analysis of boundary layer structure, thermodynamic forcing mechanisms, and model parameterization uncertainties affecting hub-height winds using North American Mesoscale Forecast System (NAM) data and one-dimensional RANS simulations. Our analysis reveals important regional and seasonal variations in atmospheric boundary layer characteristics between New England and Florida. In New England, hub-height to PBL ratios frequently exceed critical thresholds during summer convective conditions, indicating turbine operation above the shallow atmospheric boundary layer, while Florida maintains more consistent conditions with ratios well below these thresholds year-round. Thermodynamic forcing shows similarly distinct patterns, with New England experiencing strong seasonal CAPE variations between winter and summer compared to Florida's consistently elevated values. Systematic evaluation of NAM turbulence parameterization reveals moderate correlations with resolved turbulence but significant biases across the TKE spectrum. Controlled numerical experiments demonstrate that different turbulence closure schemes and vertical resolution configurations produce substantial variations in power density estimates, with the greatest deviations occurring under stable conditions.
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RC1: 'Comment on wes-2025-126', Anonymous Referee #1, 19 Aug 2025
The comment was uploaded in the form of a supplement: https://wes.copernicus.org/preprints/wes-2025-126/wes-2025-126-RC1-supplement.pdfCitation: https://doi.org/
10.5194/wes-2025-126-RC1 -
RC2: 'Comment on wes-2025-126', Anonymous Referee #2, 14 Sep 2025
Review: Ayouche et al.— Boundary layer structure and parameterization uncertainties affecting wind turbine hub-height predictions: A comparative assessment of New England and Florida
Overview
This manuscript presents, through a variety of modeling exercises, a comparative analysis of the boundary layer thermodynamic characteristics (with emphasis on the seasonal stability climatology) of two coastal regions: an area west of the Florida Gulf of Mexico coast, and a region southeast of New England now undergoing offshore wind energy development. The analysis uses the North American Mesoscale (NAM) reanalysis fields and 1D Reynolds-Averaged Navier-Stokes (RANS) model output. After reviewing the article, I recommend its rejection by the editors given 1) inconsistencies in the analysis; 2) incomplete citations of relevant published work (including prior field studies); 3) no discussion of the role of sea surface temperatures (SSTs) and air-SST differences affecting stability; 4) misapplication of land-based findings regarding stability, diurnal changes in vertical thermodynamic variables, and MO similarity theory; and 5) questionable application of certain derived thermodynamic variables such as Convective Available Potential Energy (CAPE) and Convective Inhibition (CIN).
Specific issues
Literature: Recent papers have investigated observational (stability) and modeling issues associated with offshore wind energy environments in the northeast U.S. These include (but are certainly not limited to):
Archer, C. L., Colle, B. A., Veron, D. L., Veron, F., & Sienkiewicz, M. J., 2016: On the predominance of unstable atmospheric conditions in the marine boundary layer offshore of the U.S. northeastern coast, Journal of Geophysical Research: Atmospheres, 121, 8869–8885, https://doi.org/10.1002/2016JD024896.
McCabe, E. J., & Freedman, J. M., 2025: Quantifying the uncertainty in the weather research and forecasting model under sea breeze and low-level jet conditions in the New York Bight: Importance to offshore wind energy. Weather and Forecasting, 40(3), https://doi.org/10.1175/WAF-D-22-0119.1
Optis, M., Monahan, A., & Bosveld, F. C., 2016: Limitations and breakdown of Monin–Obukhov similarity theory for wind profile extrapolation under stable stratification. Wind Energ., 19, 1053–1072, https://doi.org/10.1002/we.1883.
Page 1, line 21: “…10% error in wind speed translates to approximately a 30% error ion power estimation.” But this depends upon where you are on the power curve. Where wind speeds exceed certain thresholds, wind speed errors can be meaningless (you are at 100% capacity factors).
Page 2, lines 25 - 26: this is certainly not true over land, especially during convective conditions. And the “free atmosphere” is well above hub height over land (even in the evening);
Page 2, lines 27 - 29: “strong solar heating [does indeed induce] convective mixing during summer daytime conditions—it can also do this any time of year—but this is predominantly a land-based condition. Sea surface temperature (SST) and the SST-ambient air temperature difference is a main control for stability conditions over the ocean. In fact…
Page 2, line 31: this is the ONLY mention of SSTs in the entire paper!
Page 2, line 33: mention of sea breezes does not reference recent work of McCabe and Freedman (2023) and others.
Page 3, line 60-61: Florida may serve as a good comparative for a case study, but the region selected, in the Gulf of Mexico off the west coast of the state, has not been considered as a designated Wind Energy Area by the Bureau of Ocean Energy Management and is highly unlikely to ever see wind energy development. So I am puzzled as to why the authors chose this region.
Page 3, lines 65 70: “…marine ABL remains poorly observed for wind energy applications…” Which is precisely why the DOE/NOAA is overseeing the 3rd Wind Forecast Improvement project (WFIP3) in the very region off the New England coast the authors are focused on. WFIP3 is not mentioned at all in this paper.
Page 3, lines 94 - 95: questioning the choice of NAM analysis fields given its 6 hr temporal resolution—making diurnal analysis problematic. Why not use ERA5 (does have issues for ocean wind speeds at 100 m) or NASA’s MERRA2?
Pages 5-6, equations (2) - (10): are these really necessary for the narrative? Not really referenced much afterwords.
Page 6, line 120: there are other ways to estimate the marine ABL height (e.g., theta, q profiles) rather than just using TKE; authors do not even consider these.
Page 6, line 128: “The MYJ parameterization is…” The more favorable performance of the MYJ parameterization is shown in McCabe and Freedman (2025).
Page 6, line 131: “…varying terrain features….” Over the ocean? This is very troubling, almost as if the authors cut and paste language from elsewhere and never bothered to consider they are studying the marine ABL!
Page 6, line 133: “…at relatively coarse vertical resolution….” What does this mean?
Figure 2: I see no significant differences between New England and Florida here. Very troubling considering the authors’ assertions later on.
Page 7, line 155: “…different seasonal and local patterns…” Really? In Figure 2 (see above). How does this compare with other studies (e.g., Archer et al. 2016).
Page 8, line 161-162: “…in summer convection is stronger in Florida [than in New England] due to persistent surface heating….” Again, we are NOT over land! Most convection in Florida in Summer is due to sea breeze convergence (see e.g., Simpson 1994).
Page 8, Section 3.2: Using CAPE and CIN is really not meaningful when examining shallow marine ABLs in the context of wind energy. Again, why not use other more meaningful stability criteria, such as air-SST differences, thermodynamic profiles of heat and humidity, Bulk Richardson Number, etc. Stating that there is more CAPE over Florida than New England is stating the obvious.
Pages 9-10, Equations 19 - 24: Need to cite Paulson (1970) and Panofsky and Dutton (1984).
Page 12, lines 256-258: “According to Kim et al. (2021)…cause variations in power curves of up to 200 kW….” What power curves? For what turbine? Wind farm examined here was at a coastal site on a mountainous island. What’s the relevance?
Page 12, lines 259-260: “CBL conditions in New England produce the strongest wind shear…” How can this be? Under convective (unstable) well-mixed conditions, shear is low as the wind profile is well-mixed. I question the use of the shear methodology (U/u*) here. Why not just calculate the shear directly? You have the wind profile output from the model. Why not show a straight up wind profile (and not as in Figure 10–just show composites of the stability regimes). Higher shear is generally associated with strongly stable conditions.
Page 12, line 272: “…CBL heights extend to 2 km in summer [over New England].” Perhaps over land, but only if advected from land over water a short distance would you see this.
Page 14, line 318: “…00 UTC (nighttime) and 12 UTC (daytime) PBL heights.” In the summer, on the east coast of the U.S., 00 UTC (8 PM local time) is more representative of the daytime PBL, whereas 12 UTC (7 AM winter, 8 AM summer), is more relevant to the nocturnal PBL profile.
Page 15, lines 333 - 337: again, these words are not really relevant to what is going on over the coastal and offshore waters!
Pages 16 - 19: regarding CAPE and CIN—see my earlier comments.
Page 22, referencing Figure 9: Why two peaks in the wind speed? How is this evidence of a LLJ? And in Figure 9(b), why does the MYJ (Stable) temperature time series show no diurnal trend (just a decrease)?
Page 25, line 494-495: “Perhaps the easiest…” See McCabe and Freedman (2025).
Finally, I note that Marini et al. (2025), cited several times in the manuscript, was not accepted for publication. See https://wes.copernicus.org/preprints/wes-2025-9/.
Other references
McCabe, E. J., & Freedman, J. M., 2023: Development of an Objective Methodology for Identifying the Sea Breeze Circulation and Associated Low-Level Jet in the New York Bight. Weather and Forecasting, https://doi.org/10.1175/WAF-D-22-0119.1.
Panofsky, H. A., and J. A. Dutton, 1984: Atmospheric Turbulence. John Wiley & Sons, 397 pp.
Paulson, C. A., 1970: The mathematical representation of wind speed and temperature in the unstable atmospheric surface layer. J. Appl. Meteor.,9, 857–861.
Citation: https://doi.org/10.5194/wes-2025-126-RC2
Status: closed
-
RC1: 'Comment on wes-2025-126', Anonymous Referee #1, 19 Aug 2025
The comment was uploaded in the form of a supplement: https://wes.copernicus.org/preprints/wes-2025-126/wes-2025-126-RC1-supplement.pdf
-
RC2: 'Comment on wes-2025-126', Anonymous Referee #2, 14 Sep 2025
Review: Ayouche et al.— Boundary layer structure and parameterization uncertainties affecting wind turbine hub-height predictions: A comparative assessment of New England and Florida
Overview
This manuscript presents, through a variety of modeling exercises, a comparative analysis of the boundary layer thermodynamic characteristics (with emphasis on the seasonal stability climatology) of two coastal regions: an area west of the Florida Gulf of Mexico coast, and a region southeast of New England now undergoing offshore wind energy development. The analysis uses the North American Mesoscale (NAM) reanalysis fields and 1D Reynolds-Averaged Navier-Stokes (RANS) model output. After reviewing the article, I recommend its rejection by the editors given 1) inconsistencies in the analysis; 2) incomplete citations of relevant published work (including prior field studies); 3) no discussion of the role of sea surface temperatures (SSTs) and air-SST differences affecting stability; 4) misapplication of land-based findings regarding stability, diurnal changes in vertical thermodynamic variables, and MO similarity theory; and 5) questionable application of certain derived thermodynamic variables such as Convective Available Potential Energy (CAPE) and Convective Inhibition (CIN).
Specific issues
Literature: Recent papers have investigated observational (stability) and modeling issues associated with offshore wind energy environments in the northeast U.S. These include (but are certainly not limited to):
Archer, C. L., Colle, B. A., Veron, D. L., Veron, F., & Sienkiewicz, M. J., 2016: On the predominance of unstable atmospheric conditions in the marine boundary layer offshore of the U.S. northeastern coast, Journal of Geophysical Research: Atmospheres, 121, 8869–8885, https://doi.org/10.1002/2016JD024896.
McCabe, E. J., & Freedman, J. M., 2025: Quantifying the uncertainty in the weather research and forecasting model under sea breeze and low-level jet conditions in the New York Bight: Importance to offshore wind energy. Weather and Forecasting, 40(3), https://doi.org/10.1175/WAF-D-22-0119.1
Optis, M., Monahan, A., & Bosveld, F. C., 2016: Limitations and breakdown of Monin–Obukhov similarity theory for wind profile extrapolation under stable stratification. Wind Energ., 19, 1053–1072, https://doi.org/10.1002/we.1883.
Page 1, line 21: “…10% error in wind speed translates to approximately a 30% error ion power estimation.” But this depends upon where you are on the power curve. Where wind speeds exceed certain thresholds, wind speed errors can be meaningless (you are at 100% capacity factors).
Page 2, lines 25 - 26: this is certainly not true over land, especially during convective conditions. And the “free atmosphere” is well above hub height over land (even in the evening);
Page 2, lines 27 - 29: “strong solar heating [does indeed induce] convective mixing during summer daytime conditions—it can also do this any time of year—but this is predominantly a land-based condition. Sea surface temperature (SST) and the SST-ambient air temperature difference is a main control for stability conditions over the ocean. In fact…
Page 2, line 31: this is the ONLY mention of SSTs in the entire paper!
Page 2, line 33: mention of sea breezes does not reference recent work of McCabe and Freedman (2023) and others.
Page 3, line 60-61: Florida may serve as a good comparative for a case study, but the region selected, in the Gulf of Mexico off the west coast of the state, has not been considered as a designated Wind Energy Area by the Bureau of Ocean Energy Management and is highly unlikely to ever see wind energy development. So I am puzzled as to why the authors chose this region.
Page 3, lines 65 70: “…marine ABL remains poorly observed for wind energy applications…” Which is precisely why the DOE/NOAA is overseeing the 3rd Wind Forecast Improvement project (WFIP3) in the very region off the New England coast the authors are focused on. WFIP3 is not mentioned at all in this paper.
Page 3, lines 94 - 95: questioning the choice of NAM analysis fields given its 6 hr temporal resolution—making diurnal analysis problematic. Why not use ERA5 (does have issues for ocean wind speeds at 100 m) or NASA’s MERRA2?
Pages 5-6, equations (2) - (10): are these really necessary for the narrative? Not really referenced much afterwords.
Page 6, line 120: there are other ways to estimate the marine ABL height (e.g., theta, q profiles) rather than just using TKE; authors do not even consider these.
Page 6, line 128: “The MYJ parameterization is…” The more favorable performance of the MYJ parameterization is shown in McCabe and Freedman (2025).
Page 6, line 131: “…varying terrain features….” Over the ocean? This is very troubling, almost as if the authors cut and paste language from elsewhere and never bothered to consider they are studying the marine ABL!
Page 6, line 133: “…at relatively coarse vertical resolution….” What does this mean?
Figure 2: I see no significant differences between New England and Florida here. Very troubling considering the authors’ assertions later on.
Page 7, line 155: “…different seasonal and local patterns…” Really? In Figure 2 (see above). How does this compare with other studies (e.g., Archer et al. 2016).
Page 8, line 161-162: “…in summer convection is stronger in Florida [than in New England] due to persistent surface heating….” Again, we are NOT over land! Most convection in Florida in Summer is due to sea breeze convergence (see e.g., Simpson 1994).
Page 8, Section 3.2: Using CAPE and CIN is really not meaningful when examining shallow marine ABLs in the context of wind energy. Again, why not use other more meaningful stability criteria, such as air-SST differences, thermodynamic profiles of heat and humidity, Bulk Richardson Number, etc. Stating that there is more CAPE over Florida than New England is stating the obvious.
Pages 9-10, Equations 19 - 24: Need to cite Paulson (1970) and Panofsky and Dutton (1984).
Page 12, lines 256-258: “According to Kim et al. (2021)…cause variations in power curves of up to 200 kW….” What power curves? For what turbine? Wind farm examined here was at a coastal site on a mountainous island. What’s the relevance?
Page 12, lines 259-260: “CBL conditions in New England produce the strongest wind shear…” How can this be? Under convective (unstable) well-mixed conditions, shear is low as the wind profile is well-mixed. I question the use of the shear methodology (U/u*) here. Why not just calculate the shear directly? You have the wind profile output from the model. Why not show a straight up wind profile (and not as in Figure 10–just show composites of the stability regimes). Higher shear is generally associated with strongly stable conditions.
Page 12, line 272: “…CBL heights extend to 2 km in summer [over New England].” Perhaps over land, but only if advected from land over water a short distance would you see this.
Page 14, line 318: “…00 UTC (nighttime) and 12 UTC (daytime) PBL heights.” In the summer, on the east coast of the U.S., 00 UTC (8 PM local time) is more representative of the daytime PBL, whereas 12 UTC (7 AM winter, 8 AM summer), is more relevant to the nocturnal PBL profile.
Page 15, lines 333 - 337: again, these words are not really relevant to what is going on over the coastal and offshore waters!
Pages 16 - 19: regarding CAPE and CIN—see my earlier comments.
Page 22, referencing Figure 9: Why two peaks in the wind speed? How is this evidence of a LLJ? And in Figure 9(b), why does the MYJ (Stable) temperature time series show no diurnal trend (just a decrease)?
Page 25, line 494-495: “Perhaps the easiest…” See McCabe and Freedman (2025).
Finally, I note that Marini et al. (2025), cited several times in the manuscript, was not accepted for publication. See https://wes.copernicus.org/preprints/wes-2025-9/.
Other references
McCabe, E. J., & Freedman, J. M., 2023: Development of an Objective Methodology for Identifying the Sea Breeze Circulation and Associated Low-Level Jet in the New York Bight. Weather and Forecasting, https://doi.org/10.1175/WAF-D-22-0119.1.
Panofsky, H. A., and J. A. Dutton, 1984: Atmospheric Turbulence. John Wiley & Sons, 397 pp.
Paulson, C. A., 1970: The mathematical representation of wind speed and temperature in the unstable atmospheric surface layer. J. Appl. Meteor.,9, 857–861.
Citation: https://doi.org/10.5194/wes-2025-126-RC2
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