2011). This site provides inadequate data for easterly winds. Waves were observed from the coast or a small pier at a distance of 200–300 m from the coast in an area, which was about 3–5 m deep. Pakri in the western part of the Gulf of Finland (59°23′37″N, 24°02′40″E) is the only wave observation site that is largely open to waves generated in the northern Baltic Proper (Zaitseva-Pärnaste et al. 2009). The observation conditions were particularly good: the observer was located on

the top of a 20 m high cliff and the water depth of the area over which the waves were observed was 8–11 m. Data from the Narva-Jõesuu meteorological station in Narva Bay (59°28′06″N, 28°02′42″E) characterize check details wave properties PF-562271 in the eastern part of the Gulf of Finland (Räämet & Soomere 2010a, Räämet et al. 2010, Soomere et al. 2011). The site is open to waves approaching from west to north. Waves are observed from a 12.8 m high platform in an area 3–4 m deep and located about 200–250 m from the coast. All the listed coastal sites only conditionally represent open sea conditions. The sheltering effect of the shoreline and the relatively small water depth may at times significantly alter the local wave properties compared to those in the open sea due to

the shoaling, breaking and refraction of the waves. The potential distortions obviously affect the results of single observations (for example, they generally lead to a certain underestimation of wave heights) but apparently do not significantly alter the qualitative features of the overall wave statistics

and evidently do not impact on the nature of long-term variations and trends in wave Thymidylate synthase properties. The routine and technology for the observations were identical at all visual observation sites. They are presented in several of the above-cited sources and we just describe the key features of the routine here. The entire procedure relies on the classical zero-crossing method. The observer noted the five highest waves during a 5-min time interval. Both the mean height H of these five waves and the highest single wave Hmax were filed until about 1990. The mean wave height is normally used in the analysis; when it was missing, it was substituted by the maximum wave height. As the latter was, on average, only 6% higher than the mean wave height at Vilsandi ( Soomere & Zaitseva 2007), the potential difference is much smaller than the accuracy of the determination of the wave height. The wave period was determined as a mean period of 30 waves from three consecutive observations of sections of 10 waves (not necessarily the highest ones).