The data from 1978–1995 reliably describes the wave properties in this region, while in the data gathered using another device in 1993–2003 the overall behaviour of ZD1839 ic50 the wave height is more or less adequate but the periods are not usable ( Broman et al. 2006). In general, the data constitute

one of the most valuable data sets for the Baltic Sea because of the long temporal coverage and good resolution (1 h when available). Historically, the majority of wave information was obtained by means of visual observations. Ship-based observations of open sea wave properties are consistent with those shown by the instrumental records and have been extensively used for estimates of wave climate changes in the open ocean (Gulev & Hasse 1998, 1999, Gulev et al. 2003). Visual wave observations from coastal sites have been less frequently used for wave climate studies. Such data pose intrinsic quality and interpretation problems (Soomere & Zaitseva 2007, Zaitseva-Pärnaste et al. 2009): they contain a large fraction of subjectivity, properly represent only wave properties in the immediate nearshore and for a limited range of directions, and frequently miss long-wave systems (Orlenko et al. (eds.) 1984). They have a poor temporal

resolution, often contain extensive gaps caused by inappropriate weather or ice conditions and fail to adequately Alectinib MYO10 represent extreme wave conditions. Their basic advantage is the large temporal coverage: regular observations started in the mid-1950s at many locations on the eastern coast of the Baltic Sea and have been carried out using a unified procedure until today (Soomere & Zaitseva 2007). Thus, historical visual wave data from the eastern and north-eastern (downwind) parts of the Baltic Proper and the Gulf of Finland do indeed form an extremely valuable

data set for the identification of changes in the local wave climate. Wave observations at three Lithuanian coastal sites started more than half a century ago but only a small fraction of the diaries for 1992–2008 have been analysed in the international literature (Kelpšaitė et al. 2008, 2011). The Palanga (55°55′N, 21°03′E) and Klaipėda (55°42′N, 21°07′E) observation sites are open to predominant wind directions from south-west to N-NW. At both sites, the water depth in the observation area (about 400–500 m from the coast) was 6–7 m and the observer was standing about 3 m above sea level. The observation site at Nida (55°18′N, 21°00′E) was fully open to waves approaching only from west to N-NW. The observer stood on a turret located 7 m above sea level and observed waves about 700 m from the coastline where the water depth was 6–7 m. Visual observation sites on the coast of Estonia are located on the island of Vilsandi, on the Pakri Peninsula and at Narva-Jõesuu.