Krzysztof Jarzyna

Knowledge of prevailing winds and ocean currents was one of the crucial factors deciding the success of European sailors during the Age of Discovery. Its role has not been fully appreciated in Polish geography yet. The role of prevailing winds and ocean currents in the determination of sea lanes in the Atlantic Ocean and the Indian Ocean is described in this paper. It has been shown that winds and ocean currents can both make easier or more difficult navigation to a given destination. Some navigational techniques were developed to overcome such obstacles. The volta do mar technique was used to avoid beating trade winds during return voyages from the West Africa coast. The use of this technique in the South Atlantic Gyre demanded to drift southwest after passing by the Guinea coast and use the Brazilian Current and next prevailing westerlies to reach the Cape of Good Hope. Monsoon circulation is the main navigational challenge in the Indian Ocean. Good timing is essential for the fastest voyage there. The Brouwer Route resolved the problem of the seasonality of navigation to the Malay Archipelago to some degree. It was shown too that using the sea lanes mentioned above enabled many important discoveries, particularly those of the Brazilian and Western Australian coasts.

Thermal extremes in the Świętokrzyskie Mts ( central Poland ) at the turn of the 21st century

The aim of this study was to determine the number of hot days, very hot days and very frosty days as well as heat waves and cold spells in the Świętokrzyskie Mts ( central Poland ) during the 1981 – 2013 period. Datasets of minimum and maximum daily air temperatures from the IMGW-PIB stations : Kielce-Suków, Bodzentyn and Święty Krzyż were used in the study. During the last 35 years 17 heat waves and 12 cold spells occurred in the study area. The number of hot and very hot days and heat waves on the summits of the Świętokrzyskie Mts ( Święty Krzyż weather station ) was 2 – 5 times lower than at the valley stations. There was an evident increase in the occurrence frequency of hot weather extremes in the 2001 – 2010 period as compared to the end of the past century. There is no clear tendency to change in the number of very frosty days and cold spells. Two indices : WSNC and WSNZ were proposed as tools for the assessment of the intensity of heat waves and cold spells.