Monthly maximum number of consecutive dry days in Japan and its reproducibility by a 5-km-mesh cloud-system resolving regional climate model

概要

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The geographical distribution of the Monthly maximum number of Consecutive Dry Days (MCDD) over Japan during June–October in 2002–2006 is investigated from observed raingauge data. In June and July, areas with low MCDD (< 6 days) are analyzed associated with the climatological location of the Baiu front. In August, low MCDD [high MCDD (> 10 days)] is found in inland areas [coastal areas of the Seto Inland Sea, southern Kanto, and parts of Hokkaido]. In September and October, low MCDD [high MCDD] is found on the Japan Sea side of Honshu [in Kyushu and coastal areas of the Seto Inland Sea]. The reproducibility of the MCDD by a 5-km-mesh cloud-system resolving regional climate model (NHM-5km) is statistically examined in numerical experiments with regional objective analysis data of the Japan Meteorological Agency. NHM-5km performs well in reproducing the features of the local geographical distribution and seasonal march of MCDD, although MCDD is slightly overestimated. The MCDD values averaged for 11 sub-regions of Japan are compared with observations, revealing a good agreement (correlation coefficient, 0.755; root mean square error, 1.49; mean error, 1.10). Moreover, annual variations in MCDD averaged over Japan are well reproduced by the model.