抄録
The present study investigates the statistical features of a 110-year annual mean total water storage index (ATWSI) in a 3-layer tank model in Japan. The total water storage index, which is the summation of water storage in the three tanks, was obtained by running the 3-layer tank model forced with gridded daily precipitation data for a 110-year period from 1900 to 2009. The climatological ATWSI is 23 mm, and the maximum and minimum values are 41 and 3 mm, respectively. The climatological ATWSI resembles the climatological annual mean precipitation spatially, and features of the climatological ATWSI are also seen in the climatological annual mean water storage of each tank. The Japan-area-mean ATWSI decreases by 0.8 mm/100 year without statistical significance. The 5-year mean ATWSI shows one to two decadal variations, but has different spatial patterns even when the same sign phase occurs. This suggests that the decadal variations of the ATWSI could be caused by different climatic conditions.
