материалы конференции

Ru

CITES '2019: Труды Международной молодежной школы и конференции по вычислительно-информационным технологиям для наук об окружающей среде, Москва, 27 мая-06 июня 2019 г.

2019

Wind impact is an important factor determining the nature and intensity of currents in the Black Sea and affecting mixing in the upper layer of the sea. On average, over the year, the positive wind curl prevails over the Black Sea, which, along with the river flow, maintains the cyclonic nature of large-scale circulation in the sea. The purpose of this work is to identify trends in the long-term variability of the wind stress curl in the Black Sea and to analyze its response to changes in the direction of the wind flow prevailing over the sea. Data on wind at 10m height 4-times daily of NCEP/NCAR reanalysis (1948-2016), 1.905°-1.875° and ERA Interim reanalysis (1979-2016), 0,75°-0,75° were used. For each 6-hour interval, wind stress, wind stress curl, and the direction of the prevailing wind were calculated using wind data. The direction of the wind prevailing over the sea was determined by averaging the components of the wind vector from the data falling on the sea area, then the direction of the average vector was tied to one of 8 main geographical directions. The average wind stress curl at a particular wind direction was calculated by grouping all the curl fields with this wind direction and subsequent averaging. Seasonal and interannual variability of the basin-averaged wind stress curl, calculated from the wind data of reanalysis NCEPYNCAR and ERA Interim with different spatial resolution, have the same tendencies. High correlation coefficients were obtained between the time series (1979-2016) of the basin-averaged wind stress curl anomalies by the NCEPYNCAR and ERA Interim reanalyses (0.81 according to average annual data and 0.87 for January-February). But according to the ERA Interim reanalysis with a higher spatial resolution, the magnitude of the wind stress curl is higher towards the predominance of cyclonic curl. Seasonal variability of the basin average wind stress curl is such that cyclonic curl prevails in winter, weakens in spring, and can be replaced with anticyclonic in summer. According to two reanalysis on average per year, the maximum cyclonic basin-averaged wind stress curl is observed in synoptic situations with northeast and east winds, and anticyclonic - with southwest and westerly winds. These directions were chosen to further analyze the relationship between the interannual variability of the wind stress curl and the frequency of the prevailing wind over the sea. There are periods with predominant positive and negative anomalies in the long-term variations of the wind stress curl. According to the annual mean and winter data, cyclonic wind stress curl increased in the late 60s early 70s. At the same time an increase in the frequency of northeastern and easterly winds and a decrease in the frequency of westerly and southwesterly winds were observed. The weakening of cyclonic curl was at the end of the 90s, when the frequency of the westerly and southwesterly winds increased and the frequency of the northeastern and easterly winds decreased. The correlation coefficients of the time series of wind stress curl with the frequency of the northeastern and eastern winds are as follows: according to the average annual data 0.63, for January-February - 0.86. In the summer months, there is a weak positive trend in the variability of basin-averaged wind stress curl and the connection with the wind frequency is less significant.

2019-12-12 15:49:00