Total and solid precipitation in the Canadian Arctic and their variability from 1950 to 1995

The main aims of this paper are i) to establish the trends in solid and total precipitation as well as in solid to total precipitation ratio (hereinafter SIC ratio) in the Canadian Arctic in recent decades. and ii) to investigate the influence of air temperature and circulation factors (atmospheric and oceanic) on the above-mentioned precipitation characteristics, Recently updated and adjusted data (see Mekis and Hogg 1999) from 16 stations located in the Canadian Arctic (fig. I) were used for the investigation. The southern boundary of the study area was taken after Atlas Arktiki (1985). In addition, the data from two sub-Arctic stations were also used. The majority of the data cover the period from 1950 to 1995. The relationship between air temperature and precipitation in the Canadian Arctic was investigated using i) the sets of 10 individual warmest and 10 individual coldest years chosen from the areally averaged annual Canadian Arctic temperature series, ii) the warmest and coldest l C-year blocks from the same Canadian Arctic series, and iii) the sets of years defined in points i) and ii) but chosen from the individual station temperature series. Next, in the case of the two first approaches, for each station the differences of solid and total precipitation as well as the S/C ratio were calculated between sets of warmest and coldest years. In the third approach, the differences were only computed for the station which was the basis for choosing the warmest and coldest years. The same method was used to investigate the relationships between circulation factors and precipitation in the Canadian Arctic. The precipitation and the SIC ratio differences were calculated here between the sets of years with high and low values of the best known indices (North Atlantic Oscillation (NAO) and Southern Oscillation) characterizing atmospheric circulation or, in the case of the oceanic circulation, between the years with the opposite Arctic Ocean circulation regimes (cyclonic and anticyclonic, see e.g. Proshutinsky and Johnson 1997). The main results of the investigation were as follows: The corrected annual precipitation sums (after the influence of measured errors are deleted ) arc higher than uncorrected values by 26% to 58% depending on the analyzing station (see tab. 2). A statistically significant increase in all kinds of areally averaged seasonal and annual precipitation for the Canadian Arctic occurred over the period 1950 1995 (figs :2 and 3). On the other hand, the S/C ratio did not change significantly, except for summer values (fig. 5) and its behavior was also in accord with small variations noted in air temperature (fig. 4). Solid precipitation occurs usually in all seasons , but the S/C ratio maximum was observed in winter (98.7%) and the minimum in summer (12.5%). The areally averaged annual S/C ratio was 57,3%. An increase in air temperature in the Canadian Arctic most often led to the rise of all kinds of annual precipitation sums, but only when the warmest and coldest years were chosen based on the individual stations. The pattern of the relationship is significantly more complicated and can be even opposite to that presented above, when the sets of the warmest and coldest years are chosen based on the areally averaged annual temperature for the Canadian Arctic (see fig. 6). Significantly more stable results of changes occurred for the S/C ratio, which in warmer periods was usually lower (fig. 7). However, more detailed and reliable investigations of temperature-precipitation relations conducted for individual stations showed that the last statement is true, but only for the southern (warmer) part of the Canadian Arctic (