Upwelling Parameters From Bias-Corrected Composite Satellite SST Maps in the Gulf of Finland (Baltic Sea)

Abstract

This letter proposes a method for using the operational ship of opportunity temperature data at a fixed depth for bias correction of satellite sea surface temperature (SST) images. The bias-corrected SST imagery from MODerate Resolution Imaging Spectroradiometer (MODIS) and Advanced Along-Track Scanning Radiometer (AATSR) sensors were used to calculate mean upwelling characteristics in the Gulf of Finland (GoF, Baltic Sea). First, we determined that the operational flow through temperature data at a 4-m depth can be used for validation and bias correction of satellite SST images in cases of wind speed over 5 m · s −1 . The composite sea temperature maps were calculated from bias-corrected images collected during upwelling events in the GoF, in 2000-2009. Mean upwelling characteristics were estimated from composite maps for both the northern and southern coasts of the gulf.

Data assimilation of sea surface temperature and salinity using basin-scale EOF reconstruction: a feasibility study in the NE Baltic Sea

“…For remote sensing versus in situ reference, Kozlov et al (2014) have found RMSD 1.31 °C in the Curonian Lagoon. Uiboupin and Laanemets (2015) have estimated RMSD of various satellite products to FerryBox in the Gulf of Finland 465 from 0.29 to 0.98 °C. Our control run gave RMSD 0.72 °C.…”

“…While satellites measure SST of a thin surface layer, then FerryBox and models acquire 325 temperature over much thicker layer. It is known that in the Gulf of Finland satellite and FerryBox can have similar SST values in case of winds stronger than 5 m/s (Uiboupin and Laanemets, 2015); at smaller wind speeds the SST bias can be 1-3 °C in reference to FerryBox observations. Within these accuracy limitations, satellite observations presented in Fig.…”

Upwelling characteristics in the Gulf of Finland (Baltic Sea) as revealed by Ferrybox measurements in 2007–2013

“…mean upwelling area detected on the basis of 147 maps during the period of 2000-2009 was 5642 km 2 (19 % of the GoF surface area) along the northern coast and 3917 km 2 (13 % of the GoF surface area) along the southern coast (Uiboupin and Laanemets, 2015), while the largest area covered by the upwelling water was identified as 12140 km 2 (data from 2000 to 2006; Uiboupin and ; the authors' estimate of the mean cross-shore extent of the upwelling area was 20-30 km off the northern coast and varied between 7 and 20 km off the southern coast;…”

Data assimilation of sea surface temperature and salinity using basin-scale reconstruction from empirical orthogonal functions: a feasibility study in the northeastern Baltic Sea

“…The region covers the Gulf of Finland, the Gulf of Riga and part of the Baltic Proper adjacent to these gulfs. The region is rather shallow: the mean and maximum depths are 26 and 62 m in the Gulf of Riga (Yurkovskis et al, 1993) and 37 and 123 m in the Gulf of Finland (Alenius et al, 1998), respectively.…”

“…The region is impacted by large rivers: the Gulf of Finland and the Gulf of Riga together receive 34 % of the total freshwater discharge to the Baltic Sea as can be calculated from the data by Johansson (2017). As a result, there is an estuarine increase in SSS from east to west (Alenius et al, 1998;Yurkovskis et al, 1993), reaching 7-8 g kg −1 in the Baltic Proper (Kõuts and Omstedt, 1993). The Gulf of Finland has a free connection to the Baltic Proper without a sill or any other topographic restriction; therefore deeper more saline waters of the Baltic Proper penetrate into the Gulf of Finland and form an estuarine halocline (Liblik et al, 2013).…”