On the influence of hydrophysical conditions on representation of hydro-optical measurements using the data of the Middle Caspian coastal water exploration
V.V. Rostovtseva, A.S. Izhitskiy, I.V. Goncharenko, B.V. Konovalov, P.O. Zavialov
Southern Branch of the P.P. Shirshov Institute of Oceanology, Gelendjik, Russia
Keywords: optical passive remote sensing, natural components of seawater, suspended matter, phytoplankton and colored organic matter, Secchi disk depth of visibility, vertical profiles of water temperature, salinity and turbidity, water sampling
Abstract
Remote passive optical measurements of the state of waters from a ship, air carrier, or satellite are the most informative due to the coverage of a large area and high frequency of measurements. At the same time, for a correct assessment of the data obtained it is usually necessary to carry out in situ measurements of the water state, which means the analysis of water samples taken at a limited number of points. Using the studies carried out in coastal regions of the Middle Caspian, the conditions for the suitability of such point measurements for calibrating the results of remote hydro-optical measurements by the EMMA complex (Ecological Monitoring of Marine Waters) from board of a moving vessel have been identified. The explanation for the identified limitations was given by analysis of the structure of coastal waters obtained by water vertical sounding at the stations and operation of a flow-through system for determination of surface water temperature and salinity. An algorithm is proposed for selecting water samples suitable for calibration of remote sensing data by correlating them with the Secchi disk depth. The efficiency of this method is demonstrated. It is shown what kind of hydrophysical conditions should be taken into account for the preliminary selection of water sampling sites for calibration of optical remote measurements.
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