Multi-year average intra-annual cycle of hydrooptical characteristics, chlorophyll a and surface temperature of the Black Sea from satellite data

Abstract

On the basis of monthly means of sea surface temperature, concentration of chlorophyll a, diffuse attenuation coefficient at the wavelength of 490 nm and remote sensing reflectance at the wavelength of 555 nm according to the array of satellite measurements COPERNICUS (1998–2017) spatial and temporal characteristics of climatic intra-annual variability of these parameters were analyzed. The regions of the highest intra-annual variability of these characteristics are identified. It is shown that a decrease in the level of seasonal variability of temperature, chlorophyll a concentration and diffuse attenuation coefficient is observed at the northern coasts of the sea, while in the southern coasts, a decrease in the level of seasonal temperature variability is accompanied by an increase in the level of variability of the chlorophyll a concentration and the diffuse attenuation coefficient. It was shown that in the intra-annual cycle, the main maximum of the chlorophyll a concentration and the diffuse attenuation coefficient in the northwestern shelf is observed in May, at the time of the highest rate of warming up of water and about a month after the maximum of the Danube runoff, in the southern part of the western shelf and in the deep sea — in November, when the maximum cooling rate of the waters is observed. The correlation between the sea surface temperature, concentration of chlorophyll a, diffuse attenuation coefficient and remote sensing reflectance is estimated. It is revealed that seasonal changes in biooptical parameters are in better agreement with the intensity of the temperature changes from month to month.