Owing to the finite resolution of the wave model, there is always a certain difference between the location CHIR-99021 in vitro of an observation or measurement site and the nearest grid point for which the wave properties are calculated. This difference is an intrinsic source of deviations between modelled and measured/observed wave data.

The match of the basic statistics of numerically simulated wave conditions with those observed at different sites is, however, quite good except for some coastal locations (Räämet et al. 2009, 2010, Zaitseva-Pärnaste et al. 2009, Räämet & Soomere 2010a). Weekly variations in observed wave heights. The observed data sets contain several gaps for different reasons (Soomere & Zaitseva 2007, Soomere et al. 2011). These gaps are distributed unevenly over the years. Therefore, their presence may affect the estimated course of seasonal and even interannual variations in the wave properties. In order to suppress their influence,

Soomere et al. (2011) made an attempt to replace the missing observations by the relevant climatological mean values for wave heights for single calendar days1. These values, calculated for each calendar day over 55 years at Vilsandi and Narva-Jõesuu and over 31 years at Pakri, contain some noise, the level of which is the largest for the season with a check details relatively small number of measurements (Figure 3). The resulting values show several interesting variations in wave intensity in weekly scales, a part of which are synchronous at all three sites. The most impressive short-time feature in the wave activity is the relatively calm period at the end of December and the beginning of January. It is well pronounced in the Vilsandi and Pakri data, and somewhat less evident at Narva-Jõesuu. Shorter time periods with noticeably larger wave intensity occur at all sites during the first week PRKD3 of August, in the middle of September, at the end of October and at the beginning of December. Their presence suggests that there might exist quite a strong intraseasonal variability in weather conditions in the north-eastern Baltic Sea region.

The spatial extension of this variability is large enough to create a footprint in the wave intensity from the Baltic Proper to the south-eastern part of the Gulf of Finland. A minor feature, probably created by strong easterly winds specific to the Gulf of Finland (Soomere & Keevallik 2003), is the relatively large wave intensity at Pakri in some weeks of April/May and at the end of June. Seasonal variations in observed, measured and simulated wave heights. The presence of a strong seasonal course in the wave heights in the entire Baltic Sea region is a well-known feature that stems from the similar course in the wind speed (Rzheplinski 1965, Rzheplinski & Brekhovskikh 1967, Kahma et al. 1983, Launiainen & Laurila 1984, Mårtenson & Bergdahl 1987, Kahma & Pettersson 1993, Pettersson 1994, 2001, Mietus (ed.) 1998, Jönsson et al. 2002, Kahma et al. 2003).