Variability in the occurrence of rain and snow at Hornsund over the period July 1978 - December 2002

Abstract

In the polar regions, the sums of precipitation of the accumulation period is of great importance, because they are an component one of the most valid processes connected with glacier mass balance - accumulation. From glaciological point of view, to determine which part of annual sums of precipitation appears in the form liquid and mixed and solid precipitation is the crucial problem. In this connection, the main aim of this paper is analyse variability of the precipitation with respect of their form in the annual course as well as their long-term variability in Hornsund in the period of 1978-2002. The data used in this article are mainly derived from meteorological yearbook Hornsund (2000, 2001) that was published by Institute of Meteorology and Water Management - maritime department in Gdynia and from yearbook Meteorological Conditions Hornsund, Spitsbergen (2001) that was published by Polish Academy of Science in Warsaw. Collected numerical data are not complete. There is a lack of data concerned precipitation sums and meteorological phenomenon for the period from 01sth to 26sth of July 1981. Moreover the data describing precipitation sums does not exist for the days: 04, 07, 09, 19 July 1979. In this article three main form of precipitation (liquid, mixed and solid) were considered. The form of precipitation was determined on the base of meteorological phenomenon that was recorded as current and last weather. The average, maximum and minimum daily air temperatures were additional criterions. In this connection that the notation of meteorological data prevented to consider each event of appearance of precipitation, the days with individual form of precipitation were subjected to analysis. The day with mixed precipitation means that during all 24 hour period (from 6 given to 6 next day) appeared one time snow and second time rain or snow and rain in the same time. The annual course of individual form of precipitation and their probability of appearance in each month, long term variability of sums of individual form of precipitation and the number of days with this form of precipitation in the accumulation and annual periods were discussed. The linear trends and variability coefficients were calculated for long term characteristics of precipitation. It was stated that in Hornsund long-term average sum of annual precipitation amounted at about 424 mm The greatest part of this appear in the liquid (37%) and the lowest in a mixed form. On average in Hornsund there is noted at about 239 days with precipitation in year from what 63% falls on days with snow and 13% on days with snow and rain. In the accumulation period the solid precipitation were characterized by greatest sums as well as greatest number of days with this one. Long-term course of individual form of precipitation shows similar tendencies. In the annual period as well as in the accumulation this one liquid precipitation are characterized by the highest variability coefficient and range of change. Their lowest sums occur in the middle of 80ies and from mid-80ies they show increasing tendency. Mixed precipitation shows the smallest range of change, their highest sums occur in the middle of 80ies and in the case of annual period also in the second half of 90ies. From the second half of 90ies mixed precipitation show decreasing tendency. Statistically significant increasing tendencies of liquid and mixed precipitation during all considered period accompany decreasing tendency of solid precipitation. The highest sums of solid precipitation occur in the first half of 80ies and the lowest one in the second half of the same decade. From the beginning of 90ies there is a decreasing tendency in the course of solid precipitation. During all considered period the solid precipitation dominate as regards number of days with precipitation. The number of days with solid precipitation until the end of 80ies was greater and in the 90ies was lower than long-term average