Movement and Development of the Clouds over Khumbu Himal in Winter : Glaciological Expedition to Nepal, Contribution No. 19

概要

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Photographs of the clouds over Khumbu Himal were taken by 8 mm time-lapse camera in the winter season. Two cases are analyzed here, namely, the one is for the afternoon on a clear day and the other is for a day when weather condition is changing from clear to cloudy. In the former case for alto-cumulus clouds moving with the valley wind of 4 m/s, in speed, the base was about 3500 m and the thickness was about 100-200 m. But these clouds sometimes developed upward and were moved in the downstream direction along the valley by the upper westerly current in this region. So, it is estimated that the thickness of the valley wind is 200-300 m. In the latter case, the weather condition changed from clear in the morning to cloudy in the evening due to the developed trough in the upper westerly current. In this case, the cloud base was about 4200 m, and the thickness of the clouds increased from about 200 m near noon to 500-100 m in the evening. These analyses indicate that the cloud base is nearly uniform and the thickness of the clouds is not so large in the winter season in this region even in relatively bad weather conditions.