g. Keevallik et al. (2007), problems may appear as a result of the change from wind vanes (weathercocks) to automatic anemorhumbometers in November 1976. Back then, some parallel measurements were performed for a few years. It turned out that the new anemorhumbometers were systematically underestimating

strong (> 10 m s− 1) winds in comparison to the previous visual readings from the weathercocks. Therefore, during data pre-treatment, we adjusted the strong wind data from 1966–1976 with corrections provided by a professional handbook (Scientific-practical Handbook of the Climate of the USSR 1990). This procedure, which slightly reduces wind speeds over 10 m s− 1, was also briefly described in Suursaar & Kullas (2009). For example, a wind speed of 11 m s− 1 corresponds to the previous 12 m s− 1, and 20 m s− 1 is equivalent to the previous 23 m s− 1. In the case of both currents and winds, the positive GKT137831 cost direction is east for u and north for v when velocity components are used. The same wind forcing was also used in two locally calibrated wave hindcasts http://www.selleckchem.com/products/pifithrin-alpha.html in 1966–2011. The semi-empirical model version for shallow and intermediate-water waves used, also known as the significant wave method, is based on the fetch-limited equations of Sverdrup, Munk and Bretschneider. Currently such models are better known as the SPM method (after a series of Shore

Protection Manuals, e.g. USACE 2002). The model version that we used is the same as the one used by Huttula (1994) and Suursaar & Kullas (2009): equation(7) Hs=0.283U2gtanh0.53ghU20.75×tanh0.0125gFU20.42tanh0.53ghU20.75, where the significant wave height Hs is a function of wind speed U, effective fetch length F and depth h; U is in m s− 1, F and h are in m, and g is the acceleration due to gravity in m s− 2. No wave periods or lengths were calculated, because it is not possible to calibrate the model simultaneously with respect to Hs and wave periods. The RDCP, with a cut-off period of about 4 seconds for our mooring depth, PLEKHM2 could not provide proper calibration data for wave periods, as the RDCP and wave models represent

somewhat different aspects of the wave spectrum. This relatively simple method can deliver reasonably good and quick results for semi-enclosed medium-sized water bodies, such as big lakes (Seymour, 1977 and Huttula, 1994). Also, in the sub-basins of the Baltic Sea the role of remotely generated waves is small and the memory time of the wave fields is relatively short (Soomere, 2003 and Leppäranta and Myrberg, 2009). In practical applications, the main problem for such models seems to be the choice of effective fetch lengths, given the irregular coastline and bathymetry of this water body. Traditionally, fetches are prescribed as the headwind distances from the nearest shores for different wind directions, and an algorithm is applied that tries to take into account basin properties in a wider wind sector (e.g. Massel 1996).