On the variation of ice pellet characteristics

Abstract

Ice pellets are an important yet little‐studied type of winter precipitation. To better document and understand this type of precipitation, ice pellet particles were imaged with a high‐resolution digital camera during three winter storms in the Montréal area. Particle characteristics, size distributions, precipitation rates, and parameterizations of the particle size distributions were determined from the analysis of the images and compared between events. There were many similarities between the events, and these include the following: The same particle classes were present, the overall size distributions were very similar, and the most common particle diameter (0.6 mm) was the same. The relative lengths of spicules with respect to their base particles were also found to be similar among the three events, with the following relationship being determined: spicule length = 0.45 · particle size. In addition, substantial temporal variability (down to 5 min) was observed in both the particle sizes and the precipitation rate. Also, a range of particle sizes was observed even at low precipitation rates (0.5 mm/h). Differences between the events included the relative numbers of the different classes and the degree of temporal variability. This study confirmed that ice pellet characteristics illustrate many common features in at least three events, although important differences exist as well.