Operational sea level forecasting in Estonia

Lagemaa, Priidik; Elken, Jüri; Kõuts, Tarmo

doi:10.3176/eng.2011.4.03

Cited by 30 publications

(14 citation statements)

References 20 publications

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“…Accordingly, the inflow of open Baltic waters at this longitude takes place over the deepest part of the gulf. A similar result was also obtained using the same model for years 2010-2011 (Lagemaa, 2012, Fig. 7).…”

Section: Long-term Mean Flowsupporting

confidence: 85%

“…In the Estonian coastal sea, an eastward flow of the northern Baltic Proper saltier water is commonly expected. In addition, in the upper layer, pronounced gyre-like currents related to different sub-basins of the gulf are found (Elken et al, 2011;Lagemaa, 2012). At shorter time-scales, the current system is often more complicated and evidently depends on wind variations.…”

Section: Introductionmentioning

confidence: 96%

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Variability of currents over the southern slope of the Gulf of Finland

2015

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Please cite this article in press as: Suhhova, I., et al., Variability of currents over the southern slope of the Gulf of Finland. Oceanologia (2015), http://dx.Summary In our intraseasonal variability studies of currents in the coastal sea of the Gulf of Finland northeast of Pakri Peninsula, we compared the observation data from a bottom-mounted ADCP (March-June of 2009, 50 m depth) with the simulation data from High Resolution Operational Model of the Baltic (HIROMB). The structure of the current pattern appeared strongly dependent on the stratification conditions. The flow was quasi-barotropic during the periods of weak inverse thermal stratification at the end of winter season and at transition from the inverse thermal stratification to summer type stratification when the sea was thermally unstratified, but mostly twolayered (baroclinic) when the summer type thermal stratification had developed. The alternation of strong westward (eastward) currents (up to 30 cm s À1 ) in the upper layer is explained in terms of coastal upwelling (downwelling) due to favourable background winds. The measured and the modelled upper layers along isobath currents showed a noticeable correlation with the correlation coefficient of 0.52 and 0.82 during the periods of winter type and summer type stratifications, respectively, and the absence of a significant correlation during the transition period. The eastward (upwind) current episodes with speeds reaching 18 cm s À1 below the seasonal thermocline are likely to reflect the specific circulation response in the elongated basin caused by the easterly wind. The long-term mean (over 3.5 months) current vector (À2.0 cm s À1 , À2.9 cm s À1 ) was westward in the upper sea and eastward, nearly along isobaths (1.1 cm s À1 , À0.3 cm s À1 ) in the deeper layers.

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Section: Long-term Mean Flowsupporting

confidence: 85%

Section: Introductionmentioning

confidence: 96%

Variability of currents over the southern slope of the Gulf of Finland

2015

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“…Since 2009-2010, the measurements in the abovelisted stations have been carried out by means of automatic measuring complexes. In addition, different ports and Tallinn University of Technology have carried out measurements at 6-12 port locations during the last decade (Lagemaa et al 2011). These relatively short data sets have so far not been merged with those of the EMHI.…”

Section: Sea Level Datamentioning

confidence: 98%

Long-term storminess and sea level variations on the Estonian coast of the Baltic Sea in relation to large-scale atmospheric circulation

Jaagus¹,

Suursaar²

2013

Estonian Journal of Earth Sciences

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Variations and trends in storminess (number of storm days), and mean and maximum sea levels were analysed along the Estonian coast during the last century. An increase in storminess was detected at the Vilsandi and Sõrve stations, although inhomogeneities in the wind data make the trends less reliable. Mean sea level trends depend on the post-glacial isostatic land uplift, which is different in different parts of Estonia. After eliminating the influence of the uplift, the estimated sea level rise was 2.2–3.2 mm yr–1 during 1950–2011, which was higher than the global mean (1.9 mm yr–1). The majority of increases in storminess and sea level have been observed during the cold half-year (November–March). An increase in annual maximum sea level has been much higher than in mean values, which indicates a strong increase in the flooding risk. Atmospheric circulation is closely related to the frequencies of storms and high sea level events, especially during the cold season. Variables describing the intensity of zonal circulation (westerlies), such as the Arctic oscillation and North Atlantic oscillation indices, and the frequency of the circulation form W according to the Vangengeim–Girs classification are highly correlated with storminess and sea level on the Estonian coast during 1950–2011. Negative correlations appeared in case of the circulation form E and the SCAND index

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“…We used the HBM model (Berg and Poulsen, 2012) with subregional 0.5 NM (nautical mile, 926 m) setup (Lagemaa, 2012;Zujev and Elken, 2018) in the geographical bounds shown in Figure 1 to produce the SST and SSS data. This HBM-EST model domain contains 529 × 455 horizontal grid points.…”

Section: Regional Setting Of Experimentsmentioning

confidence: 99%

Reconstruction of Large-Scale Sea Surface Temperature and Salinity Fields Using Sub-Regional EOF Patterns From Models

et al. 2019

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A method for reconstruction of gridded fields of sea surface variables from timedependent observations, using sub-regional EOF (Empirical Orthogonal Functions) patterns from models, is presented and tested. Covariance fields, calculated from the model results over long enough time span, are used to find EOF modes. The gravest "observational" amplitudes and their first temporal derivatives are determined from the least-square minimization of fitting errors in relation to the observed values. The field is reconstructed by superposition of continuous model-based mode patterns multiplied by observational amplitudes that meet adopted statistical limits. If the observational amplitude exceeds the limits, gridded fields for this and higher modes are not produced. We applied the method in the northeastern Baltic over the model time series 2010-2015. Daily averages of sea surface temperature (SST) and salinity (SSS) from the highresolution (grid step 0.5 nautical miles) sub-regional HBM model were spatially averaged over bins of 5 × 5 nautical miles. Three first modes cover 99% of variance of temperature and 61.4% of salinity. As shown by experiments with pseudo-observations (model values at these points reconstructed to the model grid and then compared with the original model data), reconstruction performance depends on the configuration of the observation points in the model domain. Still, a few first modes usually produce acceptable results. When removing the SST seasonal cycle prior to EOF analysis, spatial patterns of leading modes remained practically unchanged, share of variance of the three first modes was reduced to 88.6% and reconstruction errors were reduced by about 25%. Sufficient spatial data coverage of the larger basin with ship-born observations usually takes quite long time-of the order of month; therefore, time correction of the amplitudes using the found temporal derivatives improves the accuracy of reconstruction. The method is compared with the Optimal Interpolation (OI) by using the pseudo-observations. Results show that, for SST reconstruction, the OI method is significantly worse than the EOF method. For SSS, OI is slightly better than EOF. The superiority of EOF is that the remote correlation patterns can be used in the reconstruction, which is important when the observations are sparse.

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Operational sea level forecasting in Estonia

Cited by 30 publications

References 20 publications

Variability of currents over the southern slope of the Gulf of Finland

Variability of currents over the southern slope of the Gulf of Finland

Long-term storminess and sea level variations on the Estonian coast of the Baltic Sea in relation to large-scale atmospheric circulation

Reconstruction of Large-Scale Sea Surface Temperature and Salinity Fields Using Sub-Regional EOF Patterns From Models

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