The Mountain Weather and Climate of Denali, Alaska-An Overview

摘要

An overview of climatological and meteorological conditions and their seasonal variability in the Denali summit region is presented, based on the NCEP-NCAR reanalysis 1 dataset for the 1948-2018 period. At the Denali grid cell, a warming trend of +0.02 degrees C significant at the 95% level is found-equivalent to a temperature increase of 1.4 degrees C over the time period. The number of very cold days (<-35 degrees C) during the climbing season (April-July) has decreased by approximately a day per decade. The number of very windy days (>= 20 m s(-1)) during the climbing season also shows a decreasing trend for the majority of the time series. To assess synoptic patterns that affect the Denali region, a self-organizing map algorithm was applied to the geopotential height (GPH) field extracted from the reanalysis data. In winter, the synoptic situation in the Denali region is dominated by frequent zonal flow and negative GPH anomalies associated with the polar front. As the polar front moves north during the seasonal cycle, patterns shift to largely positive GPH anomalies and more meridional flow. Extreme wind speeds unfavorable for climbing occur in all seasons and are associated mainly with the polar jet passing directly over Denali, or cyclogenesis in the Bering Sea. The frequency of occurrence of strongly zonal, low GPH patterns during the main climbing season (April-July) shows a slight decrease in recent years.