Ecological Safety of Coastal and Shelf Zones of Sea Ecological Safety of Coastal and Shelf Zones of Sea 2413-5577 20260304 Original paper Diurnal Cycle of the Black Sea Waters Temperature in the Area of the Southern Coast of Crimea Based on High-Frequency Measurements of the Thermoprofilemeter Rubakina V. A.
Russian Federation
valenru93@mail.ru Kubryakov A. A.
Russian Federation
arskubr@yandex.ru Gaisky P. V.
Russian Federation
gaysky@inbox.ru Marine Hydrophysical Institute of RAS Sevastopol Russia 30 09 2026 2026 3 56 75 05 02 2026 30 06 2026 04 03 2026 Copyright © 2026, V. A. Rubakina, A. A. Kubryakov, P. V. Gaisky 2026 V. A. Rubakina, A. A. Kubryakov, P. V. Gaisky https://creativecommons.org/licenses/by-nc/4.0/ https://ecological-safety.ru/en/repository/issues/2026/03/04/

The aim of this article is to analyse the vertical variability of the diurnal temperature cycle in coastal waters off the Southern Coast of Crimea. The study is based on data from a thermoprofilemeter with a high temporal resolution of 0.5 s, installed on the oceanographic platform in Katsiveli, covering the period from August 24, 2021, to November 26, 2023. It was found that the diurnal temperature cycle is expressed at all measurement depths and is most pronounced at the uppermost level (0.75 m) from May to August. Maximum anomalies of the mean diurnal cycle are observed in May–July during the morning and afternoon hours. The strongest warming occurs from 11:00 to 16:00 in layers down to 6–8 m, and during the warm season it reaches depths of 14–16 m. Selected events of significant daytime warming in both cold and warm seasons are examined. The diurnal amplitude is 1.3°C in the cold season and 3.5°C in the warm season. Statistical analysis of daytime warming ΔT shows that ΔT is most often less than 0.3°C, while events with ΔT exceeding 2–3°C are rare. The highest temperatures are observed in June–August at the uppermost levels under wind speeds of 2–4 m/s, with warming penetrating down to 18 m. During the cold season (November–April), under strong winds, temperatures are low at all depths. The highest mean ΔT values occur in summer at wind speeds up to 6 m/s, decreasing with increasing wind speed. The lowest ΔT values are characteristic of the cold season. In layers down to 4–6 m, ΔT exceeds 0.8–1°C in summer, while in winter it is close to 0°C at all measurement levels. Thus, thermoprofilemeter data can be successfully used to analyse the diurnal variability of water temperature in the coastal zone. The results obtained in this study complement the existing understanding of diurnal temperature variability in the coastal Black Sea. In particular, it was determined that the vertical distribution of diurnal temperature fluctuations strongly depends on the season and wind conditions, and in summer daytime warming can penetrate to depths of 14–18 m.

 temperature diurnal cycle distributed temperature sensor thermoprofilemeter thermistor chain Black Sea Southern Coast of Crimea The study was performed under state assignment of MHI RAS on topics FNNN-2024-0012 “Analysis, diagnosis and real-time forecast of the state of hydrophysical and hydrochemical fields of marine water areas based on mathematical modelling using data from remote and in situ methods of measurements” and FNNN-2024-0001 “Fundamental studies of the processes that determine fluxes of matter and energy in the marine environment and at its boundaries, the state and evolution of the physical and biogeochemical structure of marine systems in modern conditions”.

About the authors:

Valentina A. Rubakina, Junior Researcher, Marine Hydrophysical Institute of RAS (2 Kapitanskaya St., Sevastopol, 299011, Russia), PhD (Phys.-Math.), ORCID ID: 0000-0001-5028-5911, ResearcherID: U-5746-2019, Scopus Author ID: 57209578281, valenru93@mail.ru

Arseniy A. Kubryakov, Deputy Director for Research, Marine Hydrophysical Institute of RAS (2 Kapitanskaya St., Sevastopol, 299011, Russia), DSc (Phys.-Math.), ORCID ID: 0000-0003-3561-5913, ResearcherID: F-8921-2014, Scopus Author ID: 37072750100, arskubr@yandex.ru

Pavel V. Gaisky, Leading Researcher, Head of Laboratory, Marine Hydrophysical Institute of RAS (2 Kapitanskaya St., Sevastopol, 299011, Russia), PhD (Techn.), ORCID ID: 0000-0003-3110-848X, ResearcherID: HQZ-3112-2023, Scopus Author ID: 57222760697, gaysky@inbox.ru

Contribution of the authors:

Valentina A. Rubakina – review of literature on the research problem, analysis of the data used, description of the research results, writing the text of the article, formulation of conclusions

Arseniy A. Kubryakov – formulation of the problem, analysis of the data used, description of the research results, formulation of conclusions

Pavel V. Gaisky – review of literature on the research problem, provision of data, analysis of the data used, preparation of article materials, formulation of conclusions

All authors have read and approved the final version of the manuscript.

Article text not included.

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