ヒマラヤ周辺の降水量の定量評価 : 気候値の作成

Abstract

It is clear that quantified grid observation data at a reasonable resolution are indispensable for environmental monitoring as well as for predicting future change of mountain environment. However quantified datasets have not been available for the Himalayan region. Hence we quantitatively evaluate climatological precipitation data around the Himalayas. We compared the long-term averaged values of both Tropical Rainfall Measuring Mission (TRMM)/Precipitation Radar (PR) and rain gauge observations. To validate and adjust these patterns obtained from TRMM/PR, we used a dense network of rain gauges to measure daily precipitation over Nepal, Bangladesh, Bhutan, Pakistan, India, Myanmar, and China. Compared with the rain gauge observations, the PR systematically underestimated precipitation by 28-38% in summer (July-September). Significant correlation between TRMM/PR and rain-gauge data was found for all months, but the correlation is relatively low in winter. The relationship is investigated for different elevation zones, and it was found that the PR underestimated RG data in most zones, except for certain zones in February (250-1000m), March (0-1000m), and April (0-1500m). Monthly PR climatology was adjusted and depicted on the basis of monthly regressions between the two sets of data.