Wintertime precipitation behavior in the western Canadian Arctic region

To investigate the precipitation formation process in the two major types o f weather systems ("Pacific origin" and "storm track" types) in the western Canadian Arctic region, an X-band vertical pointing Doppler radar, microwa ve radiometer were installed at Inuvik, Northwest Territories, Canada, duri ng the midwinter of 1995/1996. Precise precipitation observations specially for ice crystals with replicator, microscope, and closeup photos were also conducted at the same place, Precipitation formation mechanisms were quite different between these two major weather systems, For the Pacific-origin- type disturbance, warm and moist air was advected from the Pacific Ocean be tween 1.5 and 3.5 km msl. Convective echo patterns appeared by radar, and a large amount of precipitable water vapor and liquid water path were estima ted by a microwave radiometer. As the air temperature was below the freezin g point, the liquid water was identified as being in the supercooled state. Densely rimed dendrites and graupel particles were observed predominantly on the ground. Collision and coalescence processes of supercooled cloud dro plets wore dominant. On the contrary, for the storm track disturbance the m oisture came from the Arctic Ocean, and strong winds were observed on the g round. The air mass was colder than -20 degrees C throughout the layer. Str atiform echo patterns were observed by radar, a smaller amount of precipita ble water vapor, and only a small liquid water path were observed by a micr owave radiometer, It was suggested that the condensation growth was predomi nant. Snow crystal shapes of plates, columns, and bullet rosettes were obse rved predominantly on the ground.