The time lag is estimated in Räämet & Soomere (2010a) in that the transitional period between the stormy (from October to February) and calm (from April to August) half-years is identified. The clearest separation of these half-years in terms of high-quality marine winds measured on the island of Utö in the north-eastern Baltic Proper occurs when September is allocated to the windy season and March to the calm season. These seasons revealed quite different increase rates in wind speed at Uto¨: while an increase of about 2% is found for March–November, a much faster increase, about 3.5% annually, has occurred in December–February.

But a clear separation of rough and Z-VAD-FMK chemical structure calm seasons in terms of the monthly mean modelled wave height takes place when September is attached to the calm half-year. More detailed

estimates of the time lag between the overall patterns of seasonal variation of wind and wave conditions are found in Räämet & Soomere (2010a), who approximated the relevant variation with a sinusoidal function (cf. Launiainen & Laurila 1984). The time lag between the wind speed at Utö and the observed wave height at Vilsandi is about half a month. It is almost a month between the observed and modelled wave heights at Vilsandi and about two months between the observed and modelled wave heights at Pakri. Consistently with the relatively large increase in wind speed at Utö in December–February, a substantial increase in wave heights only occurs at Vilsandi in Selleckchem Galunisertib early winter, whereas during all other seasons there were almost no changes in the wave intensity. Interannual variations in observed and measured wave heights. The Baltic Sea wave

fields reveal a wide range of variations in different time scales. Interestingly, Phosphatidylethanolamine N-methyltransferase the appearance and spatial coherence of such variations has undergone major changes over the last 60 years. First of all, the years with relatively high or low wave activity compared to their adjacent years occurred simultaneously in the southern and northern sections of the eastern coast of the Baltic Proper for 1993–2005 (Kelpšaitė et al. 2008). For some years the high wave activity at Vilsandi is mirrored by relatively low wave heights at Almagrundet (Broman et al. 2006, Soomere & Zaitseva 2007, Soomere et al. 2011). This peculiarity is not surprising and is apparently caused by changes in the prevailing wind direction. Variations in the annual mean wave height at Pakri are the most similar to those at Vilsandi (Zaitseva-Pärnaste et al. 2009) except for the first three years of visual observations (1954–1956). The wave heights may have been overestimated at Vilsandi during the very first years of observations (Soomere & Zaitseva 2007); however, there is some evidence that storminess was quite high in the Baltic Proper during these years (Bergström et al. 2001). The similar variations at Narva-Jõesuu completely follow those at Pakri for 1954–1985 (Soomere et al. 2011).