Selected Characteristics of Atmospheric Precipitation on the Polish Coast of the Baltic Sea

Abstract

The characteristics of extreme precipitation, including dominant trends, were analyzed for eight stations located on the Polish coast of the Baltic Sea for the period 1951-2010. Maximum 1-day and 5-day precipitation totals, events exceeding the 90th and 95th percentile calculated for the period 1961-1990 applied as indices enabling the assessment of the frequency of wet conditions. Annual trends were calculated using the standard linear regression method, while the fit of the model was assessed with the t-test at the 95% confidence level. Annual precipitation reaches values from 775 mm on the east coast to 683 mm on the central coast and shows positive trends on six out of eight analyzed stations, from 0.8 mm·year-1 in Swibno to 2.5 mm·year−1 in Dziwnow. The maximum 1-day precipitation totals range between 58.7 mm on the western coast to 105.0 mm on the central coast and show statistically significant trends (0.1 - 0.2 mm·year−1) in this area. There are, on average, six to seven 5-day rainfall periods recorded annually in the investigated area. The annual number of 5-day precipitation periods shows positive statistically significant trends in the central and eastern part of the South Baltic coast (0.2-0.3 per 10 years). The median of the maximum 5-day precipitation totals ranges from 21.6 mm in Swinoujscie to 78.6 mm in Ustka. Trends in changes in maximum 5-day rainfall totals reach the level of 0.1-0.2 mm·year−1 and are statistically significant in stations from Swinoujscie to Ustka and in Gdynia. The values of the 90th percentile of 1-day precipitation total are equal to 8-10 mm. Annually, there are about 16-18 days with such precipitation recorded in the area under investigation. The trends are positive (0.1-1.0 day per 10 years) on the central coast. The values of the 95th percentile of 1-day precipitation totals reach 11.5-14.0 mm. Annually, there are about 8-9 days with such precipitation recorded in the area under investigation. The trends are positive (0.3-0.4 days·10 years−1) on the western and central coast.