Environmental Limits of Needle Ice: A Global Survey

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Abstract
The global distribution of needle-ice incidence is examined through a detailed literature search which revealed more than 200 relevant studies. A comprehensive database of the 113 locatable needle-ice observations is presented, which includes details of observation site, longitude, latitude, and altitude, observation date, nature of needle-ice activity, and bibliographic source. The database enables definition of four research gaps. A world map shows that needle ice is fairly widespread, with concentrations around the Andes/Rockies mountain chain, eastern United States, northwest and central Europe East African high mountains, New Zealand, and Japan. The "existence domain" of the process is tentatively delimited by plotting observation latitudes against altitudes. An inverted U-shaped envelope distribution is obtained, with needle ice occurring at successively higher altitudes with decreasing latitude. The upper limit corresponds loosely with the lower limit of permaforst. Although needle ice is largely a winter phenomenon, it may occur at almost any time of the year in temperate zones. In high latitudes, needle ice mainly appears at either end of the winter freezeup. The distributions presented may help interpretations of other cryogenic distributions and provide an indication of needle-ice potential in fieldwork areas.