Quantitative estimation of orographic precipitation over the Himalayas by using APHRODITE's dense network of rain gauges and TRMM/PR

Precipitation Radar (PR) data acquired by the Tropical Rainfall Measuring Mission (TRMM) over 10 years of observation were used to show the monthly rainfall patterns over the Himalayas. To validate and adjust these patterns, we used a dense network of rain gauges to measure daily precipitation over Nepal, Bangladesh, Bhutan, Pakistan, India, Myanmar, and China that were used for Asian Precipitation—Highly Resolved Observational Data Integration Towards Evaluation of Water Resources (APHRODITE) daily precipitation data (Yatagai et al., 2009, 2012). We then compared TRMM/PR and rain gauge data in 0.05-degree grid cells (an approximately 5.5-km mesh)　according to season and elevation. Compared with the rain gauge observations, the PR systematically underestimated precipitation by 28–38% in summer (July–September). Monthly PR climatology was adjusted on the basis of monthly regressions between the two sets of data and depicted. To use this climatology as a basis of daily/monthly precipitation estimates, a combining use of WorldClim (Hijmans et al., 2005) was performed. APHRODITE project released daily temperature analysis and rain/snow discrimination over the monsoon Asia (Yasutomi et al., 2011, http://www.chikyu.ac.jp/precip/). Discussions on the above mentioned validation results and rainfall type (rain/snow) will be made.