Modification of Convective Snow-Clouds in Landing the Japan Sea Coastal Region

Abstract

The modification process of convective snow-clouds in landing the Japan Sea coastal region was observed quantitatively by a RHI radar which was set at Wajima in the Noto Peninsula. The analysis of observational data-was made mainly for snow-clouds in two cases of A and D-in case A the outbreak of cold air became intensive with time after the passage of a low pressure and in case D it was predominant persistently. In both cases most of convective radar-echoes which travelled from the sea showed two stages of variation of echo structure in their landing. In the first stage the echo becomes intensive in its center before landing. Its most intensive part descends several kilometers offshore and the other part found out in its frontal side extends upward with time. The latter part descends inland rapidly after having crossed over the seashore. In the second stage seen after landing the intensity of the echo increases gradually again as a diffused broad echo. In the first stage graupels were observed on the ground predominantly and in the second stage snowflakes were observed as predominant particles. It was suggested from the comparison of echo intensity over the sea with that over the land that the amount of snowfall seen in the seaside of the peninsula was larger than that in the land side in case D, while it was smaller than that in the land side in case A.