Wind Speed Profile Statistics from Acoustic Soundings at a Black Sea Coastal Site

Round 1

Reviewer 1 Report

The study of the planetary and internal boundary layers is an important problem of modern atmosphere research. Significant results of planetary and internal boundary layer study are obtained by means of newly developed instruments for atmosphere remote sensing from the ground. In this context, the analyzes, based on sodar measurements of the wind profiles and Weibull distribution parameters of atmosphere near Black Sea coast yield valuable information about climatic research of the vertical structure of the coastal boundary layer. So, I recommend to accept the paper with some small corrections of the text:

1. The small figures, used in Table 1 need to be properly described in the text.
2. The items “Summer seasons” and “Winter seasons” in Table 2 are needless, because their analyzes is not included in the paper. The item “Total period” may be formulated in a single sentence of type “The wind speed distribution in height and weibull scale and shape parameters are determined for marine air masses, land air masses and all air masses, while the average diurnal variations of wind speed are determined for all air masses only.” The Table 2 should be deleted.
3. Line 178 should be deleted.
4. Not all variable in equations (1) – (3) are explained. The text after the formulae should be in the form:

where k is …, c - …, k^ - …, c^ - …, N - …, u - …

5. Line 394: Table 3 stands Table 2.
6. In conclusions it  is necessary to add short explicit explanation of the results yielded by the analyses of wind speed distribution in height and diurnal variations of wind speed.

Author Response

Response to Reviewer 1 of atmosphere-1342888

We are thankful to the reviewer for pointing out items that will improve our paper. We elaborated the text as shown below.

1. The small figures, used in Table 1 need to be properly described in the text.

The introduction of Table 1 in the text is given in more details and the text of Table 1 is elaborated as follows:

The data availability during the different months of the study period is presented in Table 1 where the range of availability above 70% is given with circles in green, between 40 and 70% in yellow, and below 40% in red. The exact availability is given with the number in %.

The maximum of the actual (effective) sodar range in Table 1 is also presented as height [m] and graphically in Table 1 with small charts of 4 bars, where one filled bar filled denotesat a height range of 450 m, 2 filled bars – a range over 540 m, 3 filled bars – a range over 640 m and 4 filled bars – a range over 740 m.

Table 1. Monthly data availability [%] and maximum effective height [m] reached by the sodar for the study period. Circles show availability above 70% when green, between 40 and 70% when yellow, and below 40% when red. The range is presented graphically with small charts of 4 bars, where one filled bar denotes a range of 450 m, 2 filled bars – a range over 540 m, 3 filled bars – a range over 640 m and 4 filled bars – a range over 740 m.

1. The items “Summer seasons” and “Winter seasons” in Table 2 are needless, because their analyzes is not included in the paper. The item “Total period” may be formulated in a single sentence of type “The wind speed distribution in height and weibull scale and shape parameters are determined for marine air masses, land air masses and all air masses, while the average diurnal variations of wind speed are determined for all air masses only.” The Table 2 should be deleted.

Thanks, we followed your advice – we deleted table 2 and replaced it with the text:

The conditions set for the data selection have limited the analysis to 2 357 days and aim to avoid the accumulation of a large number of short profiles that have not exceeded 110 m in height, while allowing profiles that have not started from the lowest sodar vertical range to be involved in the analyzes (profiles beginning from 30 to 40 m above the ground are often seen). The statistical analyzes of wind speed profiles comprise: Analysis I - Wind speed distribution in height; Analysis II - Weibull scale and shape parameters profiles; Analysis III – Average diurnal variation of wind speed at different heights. These three types of analysis are performed for all air masses and separately for marine and land air masses.

1. Line 178 should be deleted.

Deleted

1. Not all variable in equations (1) – (3) are explained. The text after the formulae should be in the form:

where k is …, c - …, k^ - …, c^ - …, N - …, u - …

The recommendation was fulfilled.

1. Line 394: Table 3 stands Table 2.

Done

1. In conclusions it  is necessary to add short explicit explanation of the results yielded by the analyses of wind speed distribution in height and diurnal variations of wind speed.

The abstract, introduction, discussion and conclusions were elaborated to show more explicit the importance of the reversal height or maximum in the profile of Weibull shape parameter – namely this is a height were no diurnal changes of wind speed are observed and this is important for wind energy and tall constructions.

Reviewer 2 Report

This paper performs the study of the vertical structure of the wind  by 7-years measurements of winds from Doppler lidar. The measurements results are in high resolution (10-min temporal and 10 m vertical). They found that the wind in the nighttime was stronger, while the wind in the daytime is weaker. From the wind measurements, they are also able to estimate the height of the internal boundary layer height. The paper is well written and well organized. These results are at least crucial for meteorology in a country that may be lack of the similar studies before. In all, I recommend this paper to be published in present form.

Author Response

Response to Reviewer 2 of atmosphere-1342888

We are thankful to the reviewer for his judgement for the value and importance of our work.

Reviewer 3 Report

This manuscript conducted the statistical analysis via Weibull distribution, which offers the unique information on the vertical wind structure of coastal areas. The detailed results were also displayed with the summary of the features of data samples. Overall, the topic of this study is interesting, and the manuscript was well organised and written. I suggest it can be considered to be published in Atmosphere if the authors can well address the following comments.

1. The contribution and innovation of the manuscript should be clarified clearly in abstract and introduction.
2. Broaden and update the literature review to better connect to the current effort in the field of acoustic sounding.
3. Some practical applications of the finding in this research can be listed in discussions.
4. More future research should be included in conclusion part.

Author Response

Response to Reviewer 3 of atmosphere-1342888

We are thankful to the reviewer for praising our study and pointing out topics that need to be emphasized in order to improve the paper.

1. The contribution and innovation of the manuscript should be clarified clearly in abstract and introduction.

The last sentence of the Abstract is elaborated as follows:

The obtained information forms the basis for climatological insights on the vertical structure of the coastal boundary layer and is unique long-term data set important not only for Bulgaria but for coastal meteorology in general.

the last paragraph of the Introduction is elaborated as follows:

In summary, it can be noted that in the literature there are many short-term studies dedicated to the coastal boundary layer using acoustic remote sounding in different places around the world for short periods [25-31] and they have proved the great capabilities of the sodar measurements for the study the wind structure of the PBL. The novelty and the contribution to science of this paper consist in the statistical analyzes of sodar long-term wind speed data, which brings new information for the vertical structure of the atmosphere in coastal regions, and particularly for the Bulgarian Black Sea coast. Except for theoretical research, the created database can be used for wind and turbulence regime studies, such as extreme wind events, numerical models evaluation, air pollution, assessment of the wind resource, etc.

1. Broaden and update the literature review to better connect to the current effort in the field of acoustic sounding.

The introduction and discussions and the list of references has been broadened and updated including the following papers:

• Emeis S., M.unkel C., Vogt S., Mueller W. J., Schaefer K. - Atmospheric boundary-layer structure from simultaneous SODAR, RASS, and ceilometer measurements. Atmospheric Environment 2004, 38, 273–286, doi:10.1016/j.atmosenv.2003.09.054
• Lo Feudo, C. R. Calidonna, Avolio E., Sempreviva A. M. - Study of the Vertical Structure of the Coastal Boundary Layer Integrating Surface Measurements and Ground-Based Remote Sensing. Sensors 2020, 20(22), 6516; https://doi.org/10.3390/s20226516
• Kallistratova, M.A.; Petenko, I.V.; Kouznetsov, R.D.; Kulichkov, S.N.; Chkhetiani, O.G.; Chunchusov, I.P.; Lyulyukin, V.S.; Zaitseva, D.V.; Vazaeva, N.V.; Kuznetsov, D.D. Sodar Sounding of the Atmospheric Boundary Layer: Review of Studies at the Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences. Izv. Atmos. Ocean. Phys. 2018, 54, 242–256.
• Wandinger, U.; Freudenthaler, V.; Baars, H.; Amodeo, A.; Engelmann, R.; Mattis, I.; Groß, S.; Pappalardo, G.; Giunta, A.; D’Amico, G.; et al. EARLINET instrument intercomparison campaigns: Overview on strategy and results. Atmos. Meas. Tech. 2016, 9, 1001–1023.
• Lang S.and McKeogh E. - LIDAR and SODAR Measurements of Wind Speed and Direction in Upland Terrain for Wind Energy Purposes. Remote Sens. 2011, 3, 1871-1901; doi:10.3390/rs3091871
• Lyulyukin V., Kallistratova M., Zaitseva D., Kuznetsov D., Artamonov A., Repina I., Petenko I., Kouznetsov R. and Pashkin A. - Sodar Observation of the ABL Structure and Waves over the Black Sea Offshore Site. Atmosphere 2019, 10, 811; doi:10.3390/atmos10120811
• Batchvarova, E, Spassova, T, Marinski, J. Air Pollution and Specific Meteorological Conditions at the Adjacent Areas of Sea Ports. IFAC PAPERSONLINE, 51, 30, ELSEVIER SCIENCE BV, PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS, 2018, ISSN:ISSN: 2405-8963, DOI:10.1016/j.ifacol.2018.11.336, 378-383.
• Batchvarova, E.; Cai, X.; Gryning, S.-E.; Steyn, D. Modelling internal boundary-layer development in a region with a complex coastline. Boundary-Layer Meteorology 1999, 90, 1-20, doi:10.1023/A:1001751219627.
• Batchvarova, E.; Gryning, S.-E. Wind climatology, atmospheric turbulence and internal boundary-layer development in Athens during the MEDCAPHOT-TRACE experiment. Atmospheric Environment 1998, 32, 2055–2069, doi:https://doi.org/10.1016/S1352-2310(97)00422-6.

1. Some practical applications of the finding in this research can be listed in discussions.

The discussion part is elaborated as follows:

5. Discussion

The study reveals for a first time details in the vertical structure of the wind field within the PBL in a Black Sea coastal area. The period of 8 years is among the long-term remote sensing data sets in Europe. The results show reversal height of 40 m for all and for land air masses and about 100 m for marine air masses. At the reversal height the wind speed is characterized with small diurnal changes, which is important for wind energy and other tall constructions sensitive to the variability and strength of the wind. It can be noted that the analysis shows that the wind speed at the reversal height within marine air masses is about 7 ms^-1, within land air masses is about 5 ms^-1 and for all wind directions is about 4 ms^-1.

The height of the IBL at 400 m inland from the coast is assessed to be 50-80 m, a range defined by the definition of marine air masses as those from 0-120 degrees and consequently different fetch over land for air from these directions. As discussed in [13,42], the IBL height is important for air pollution assessments and forecast, as it defines much smaller volume for dilution compared to that at homogeneous areas. When building industry near the coast the IBL height defines whether the emissions may lead to fumigation and across which area. The IBL characteristics determine the climate and weather comfort for recreation and tourism at coastal sites. The peak in the profiles of the Weibull distribution scale parameter of marine air masses at about 260-300 m is related to the height of maximal wind speed in sea breeze situations. The profiles of the scale and shape parameters of the Weibull distribution  for the marine and land air masses are in agreement with the findings of [16,17] investigating this important for wind energy applications topic over land and sea.

1. More future research should be included in conclusion part.

We introduced

7. Future work

The rich sodar data set will be used in future for various mesometeorological model evaluation studies, such as closed sea breeze cells, other specific cases of different interaction of local and synoptic driving forces, wind energy and air pollution assessments. The experience and ideas born from sodar measurements analysis will be explored with different types of ground-based remote sensing instruments at coastal and urban sites within international collaboration.