This article focuses on the interaction between the Ob‐ and Yenisei‐dominated parts of the large Ob‐Yenisei buoyant plume formed in the southern part of the Kara Sea during ice‐free periods. It was shown that certain wind forcing and river discharge conditions cause the formation of a specific structure of the Ob‐Yenisei plume with significantly different properties of the Ob‐ and Yenisei‐dominated water masses. Under these conditions, the Yenisei runoff generates a narrow coastal current propagating northward from the Yenisei Gulf along the Taymyr Peninsula, which is isolated by the Ob‐dominated water mass from ambient sea water. As a result, the low‐salinity Yenisei‐dominated water mass occupies a relatively small area, while more saline Ob‐dominated water mass spreads over a wide area between the Gulf of Ob and the Taymyr Peninsula. The formation of the “isolation” configuration of the Ob‐Yenisei plume described above is presumed to be caused by the eastward Ekman transport and the resulting downwelling flow of the Ob‐dominated waters under the low‐saline and warm Yenisei‐dominated waters along the Taymyr Peninsula. Based on satellite imagery, wind reanalysis, and river discharge data collected and derived for the period of 2005–2011, it was estimated that the “isolation” configuration is regularly formed during late summer and autumn when the Ob discharge to the Kara Sea exceeds the Yenisei discharge and the local atmospheric circulation is dominated by the northerly wind regime. Assessment of the frequency and duration of the occurrence of the “isolation” configuration showed their synoptic time scale and significant interannual variability.
Despite longstanding contributions to oceanography, similar use of fluorescence light detection and ranging (LiDAR) in lake settings is not routine. The potential for ship-mounted, multispectral Ultraviolet Fluorescence LiDAR (UFL) to provide rapid, high-resolution data in variably turbid and productive lake conditions are investigated here through a series of laboratory tank and field measurements carried out on Lake Balaton, Hungary. UFL data, calibrated empirically to a set of coinciding conventionally-analyzed samples, provide simultaneous estimates of three important parameters-chlorophyll a(chla), total suspended matter (TSM) and colored dissolved organic matter (CDOM). Successful UFL retrievals from both laboratory and field measurements were achieved for chla (0.01-378 mg·m
4406Cylindrospermopsis raciborskii, and chlorophyta, Scenedesmus armatus). The ratio between fluorescence emissions measured at 650 nm, related to the phycocyanin fluorescence maximum, to that at 685 nm is demonstrated to effectively distinguish these two species. Validation through both laboratory measurements and field measurements confirmed that site specific calibration is necessary. This study presents the first known assessment and application of ship-mounted fluorescence LiDAR in freshwater lake conditions and demonstrates the use of UFL in measuring important water quality parameters despite the more complicated hydro-optic conditions of inland waters.
This article is based on field measurements on the lake Balaton (Hungary) during the three days: 10, 11, and 12 September 2008. The expedition was performed with the aim to test recently developed ultraviolet (UV) fluorescent portable lidar UFL-8 in natural lake waters and to validate it by contact conventional measurements. We had opportunity to compare our results with the Moderate Resolution Imaging Spectroradiometer (MODIS)/Terra spectroradiometer satellite images received at the satellite monitoring station of the Eötvös Loránd University (Budapest, Hungary) to make an attempt of lidar calibration of satellite medium-resolution bands data. Water quality parameters were surveyed with the help of UFL lidar in a time interval very close to the satellite overpass. High resolution maps of the chlorophyll-a, chromophoric dissolved organic matter and total suspended sediments spatial distributions were obtained.
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