Meteorological and synoptic aspects of the formation and evolution of the Novorossiysk Bora

Semenov, E. K.; Sokolikhina, N. N.; Sokolikhina, E. V.

doi:10.3103/s1068373913100026

Cited by 5 publications

(3 citation statements)

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“…The average annual number of days with bora for the studied 117-year time series is 30. This value is close to the following source estimates: 32 days [1], 45 days [2,3] and from 30 to 40 days [11]. It should be noted that the actual picture of the bora cases distribution in some years significantly differs from the average one.…”

Section: Analysis Resultssupporting

confidence: 86%

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2019

PhO

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Bora in Novorossiysk is the strong, cold, gusting northeast wind directed to the sea on a ridge slope. As the dangerous phenomenon of weather it happens in winter at the wind speed more than 30 m/s, therefore, bora cases with maximum speed and minimum subzero temperature are of practical and all-physical interest. Methods and Results. According to long-term daily data from the archives at the station Novorossiysk and observations from the Russian Hydrometeorological Institute (https://rp5.ru/) for the period 1901-2017 statistics on the number of days with bora for cold and warm periods and the number of bora cases with different duration of the day and their repeatability by month for the period 1901-2017 are obtained. Modern regional numerical models developed in the Marine Hydrophysical Institute permit to take into account the role of orography in generation of the Novorossiysk bora, to define its localization and to study evolution of thermodynamic fields of a strong bora during its development and attenuation. The estimation of the repeatability of extreme wind speeds at true bora by the method of approximation of the cumulative function of the series by the Weibull distribution is given. In the analysis of sinoptic features of bora formation, the data of RegCM regional reanalysis for the period 1979-2013, as well as data of ERA Interim reanalysis at model levels were used. Roses of winds for points at windward and leeward slopes are constructed. Conclusions. It was found that the average annual number of days with bora for the study time series is 30. The greatest duration of cases with bora falls on the winter months and can be up to 7 days. From the arrays of reanalysis data, the fields of pressure and wind speed corresponding to a strong bora are selected and classified by the cluster analysis method. Composites of pressure and wind fields are constructed. It is shown that the condition for the development of a strong bora is the formation of two pressure centersthe northern cyclonic and southern anticyclonic. Vertical profiles of temperature, wind speed and buoyancy frequency for 2 main clusters are presented. According to the measurements on the Novorossiysk HMS, the time characteristics of the bora were estimated. It is shown that the main features necessary for the formation of a true bora is an intense lowatmospheric air flow with velocities of about 10-15 m/c, accompanied by temperature inversion at an altitude of about 1 km and the formation of the underlying layer of stably stratified air.

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Section: Analysis Resultssupporting

confidence: 86%

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2019

PhO

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“…An extreme manifestation of the complex air circulation system in this area is known as the Novorossiysk bora [18]. During these events, local winds can exceed 40 m/s with wind gusts up to 100 m/s [41].…”

Section: Study Area General Descriptionmentioning

confidence: 99%

Wave Buoy Measurements at Short Fetches in the Black Sea Nearshore: Mixed Sea and Energy Fluxes

Rybalko¹,

Myslenkov²,

Badulin³

2023

Preprint

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Wave buoy measurements were carried out near the north-eastern Black Sea coast at the natural reserve Utrish in 2020-2021. Totally about 11 months of data records were collected during two stages of the experiment at 600 and 1500 meters offshore and depths of 18 and 42 meters. The measured waves propagate almost exclusively from the seaward directions. Generally, the waves do not follow the local wind directions, thus, implying a mixed sea state. Nevertheless, dependencies of dimensionless wave heights on periods based on the wind speed scaling appear to be close to previously established empirical laws for the wind-driven seas. The results of the wave turbulence theory are applied for estimates of spectral energy fluxes and their correspondence to the energy flux from the turbulent wind pulsations. These estimates are consistent with today’s understanding of wind-wave interaction. It is shown that the main fraction of the wind energy flux goes to the direct Kolmogorov-Zakharov cascade to high wave frequencies and then to dissipation in small scales. Less than 1% of the wind energy flux is directed to low frequency band (the so-called inverse Kolmogorov-Zakharov cascade), thus, providing wave energy growth.

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“…An extreme manifestation of the complex air circulation system in this area is known as the Novorossiysk bora [17]. During these events, local winds can exceed 40 m/s with wind gusts up to 100 m/s [45].…”

Section: Study Area General Descriptionmentioning

confidence: 99%

Wave Buoy Measurements at Short Fetches in the Black Sea Nearshore: Mixed Sea and Energy Fluxes

Rybalko

Myslenkov

Badulin

2023

Water

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Wave buoy measurements were carried out near the northeastern Black Sea coast at the natural reserve Utrish in 2020–2021. In total, about 11 months of data records were collected during two stages of the experiment at 600 and 1500 m offshore and depths of 18 and 42 m. The measured waves propagate almost exclusively from the seaward directions. Generally, the waves do not follow the local wind directions, thus, implying a mixed sea state. Nevertheless, dimensionless wave heights and periods appears to be quite close to the previously established empirical laws for the wind-driven seas. The results of the wave turbulence theory are applied for estimates of spectral energy fluxes and their correspondence to the energy flux from the turbulent wind pulsations. These estimates are consistent with today’s understanding of wind–wave interaction. It is shown that the main fraction of the wind energy flux is sent to the direct Kolmogorov–Zakharov cascade to high wave frequencies and then dissipates in small amounts. Less than 1% of the wind energy flux is directed to the low frequency band (the so-called inverse Kolmogorov–Zakharov cascade), thus, providing wave energy growth.

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Meteorological and synoptic aspects of the formation and evolution of the Novorossiysk Bora

Cited by 5 publications

References 0 publications

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Wave Buoy Measurements at Short Fetches in the Black Sea Nearshore: Mixed Sea and Energy Fluxes

Wave Buoy Measurements at Short Fetches in the Black Sea Nearshore: Mixed Sea and Energy Fluxes

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