Surface Microphysical Observations within East Coast Winter Storms on Long Island, New York

Abstract

Surface observations of ice habit and degree of riming were measured for 12 cyclone events over 3 winter seasons at Stony Brook, New York, on the northeast coast of the United States. A total of 205.6 cm of snow accumulated during these storms, with an average degree of riming of 1.25 (out of 5) and snow-to-liquid ratio ranging from 3:1 to 17:1. There were consistent spatial patterns of habit and riming intensity relative to the cyclone structure. Cold-type habits (side planes and bullets) commonly occurred within the outer comma head to the north and northeast of the cyclone center. In the middle of the comma head, moderately rimed dendrites, plates, and needles were observed. Close to the cyclone center, heavy riming was observed with needles and graupel. The western quadrant of the comma head had primarily plates and dendrites with little to no riming. Periods of light riming and high snow–liquid ratios (≥13:1) are dominated by cold-type habits, dendrites, and plates and have similar vertical motion and synoptic characteristics inferred from 13-km Rapid Update Cycle analyses. Maximum vertical motion occurred in a region of favored ice growth and less supercooled water (from −15° to −25°C). During heavy riming periods, needles and graupel are dominant and the vertical motion maximum occurs at temperatures from 0° to −5°C. Vertically pointing Micro Rain Radar indicates stronger vertical motions and turbulence for heavy riming as opposed to light rimming periods. Periods with low snow-to-liquid ratio (≤7:1) were observed to occur either as heavy rimed particles or as light riming of compact habits such as sideplanes, bullets, and needles.