Seasonal and regional features of long-term precipitation changes in Japan

Abstract

We documented precipitation changes in Japan from 1901 to 2009 using five climatological indices and daily data at 51 stations. Annual precipitation amount (PRCPTOT) decreased over the 109 years, and the number of days with precipitation (R1mm) decreased even more, causing their ratio (SDII), an indicator of precipitation intensity, to increase.The consecutive dry days index (CDD) increased, and the consecutive wet days index (CWD) decreased, as a result of fewer days of precipitation. Linear trends of the indices during each season show complicated regional features that are highly incoherent among the seasons, whereas trends of monthly and six-pentad (thirty-day) mean values show subseasonal variations, which implies heterogeneous climate changes on the sub-seasonal scale. Some of these results, such as the tendency for the Baiu period to shift to later in the summer over eastern and western Japan, agree with climate change projections, although more robust information on the regionality and seasonality of long-term precipitation trends will require further study on underlying changes in atmospheric circulation systems.

Drought Hardening Contributes to the Maintenance of Proportions of Non-Embolized Xylem and Cambium Status during Consecutive Dry Treatment in Container-Grown Seedling of Japanese Cedar (Cryptomeria japonica)

“…Oguchi and Fujibe [6] projected that consecutive dry days increase by around 1.0 day per year over the wide area of Japan. Moreover, the average length of consecutive dry days is around 20 days, with annual fluctuations [6]. These projections indicate that seedlings for afforestation are expected to be exposed to unexperienced severe drought in the future.…”

“…Because 85% of the afforestation costs for C. japonica is spent during years after planting [4], the high rate of drought-induced mortality results in huge economic losses. Furthermore, climate models in Japan predict that the annual mean air temperature will increase from 1 • C to 2.5 • C [5] and consecutive dry days have been on the increase since 1901 [6], further increasing the risk of seedling mortality. Maintaining high rates of survival in C. japonica seedlings is therefore important in terms of appropriate forest management under this changing climate.…”

Long-Term Precipitation Changes in the Baiu and Akisame Seasons in Japan over the Past 120 Years (1901–2020)

“…The analysis was based on daily and 10-day or 11-day accumulated data (e.g., 1-10 July, 11-20 July, and 21-31 July), which were compiled and digitalized by the JMA. Few precipitation records were missing for this period (e.g., Fujibe et al 2006;Oguchi and Fujibe 2012).…”

“…Based on precipitation estimates from satellite radar observations, Takahashi and Fujinami (2021) showed that the frequency of heavy precipitation events (>10 mm/h) during the Baiu season (mid-June-mid-July) increased by 24% between 1998-2008 and 2009-2019. In contrast to these insights into the Baiu precipitation, long-term precipitation variations during the Akisame season are poorly understood. The existing literature is limited to the studies of Oguchi and Fujibe (2012) and Duan et al (2015), who examined precipitation data from 1901 at seasonal and regional scales in Japan. They identified decreasing trends in precipitation amount during fall (September to November), with a statistical significance at some weather stations.…”

Trend Analysis of Hydroclimatic Variables in the Kamo River Basin, Japan

“…Hydroclimatic variations always vary among geographic locations [16]. Oguchi and Fujibe [17] concluded that features of precipitation changes in Japan have regional differences. Understanding long-term trends in hydroclimatic variables at each catchment is very important to the national and local water management.…”