Historical regional climate changes in Japan in winter as assessed by a 5-km regional climate model with a land surface process

Progress in Earth and Planetary Science

Table 1 Specifications of the numerical model

	20 km NHRCM	5 km NHRCM
Grid number	281 × 281 × 50	527 × 804 × 50
Time interval	60 s	20 s
Initial and lateral boundary condition	JRA-55 (Kobayashi et al. 2015)	20 km NHRCM
Initial date	July 20	July 21
Target years	From September 1958 to August 2020 First 40 days (July 21–August 31) are spin-up durations for NHRCM with 5 km grid spacing
Topography	GTOPO30 (grid mean)
Microphysics	Prognostic variables: mixing ratio (water vapor, cloud water, cloud ice, snow, and graupel) and number concentration (cloud ice, snow, graupel) (Ikawa and Saito 1991)
Boundary layer	MYNN level 2.5 (Nakanishi and Niino 2004)
Cumulus convection	KF scheme (Kain and Fritsch 1990; Kain 2004; Nakano et al. 2012)
Radiation	Clear sky (Yabu et al. 2005) and cloud (Kitagawa 2000)
Land surface	Improved MJ-SiB (Hirai et al. 2007)
Wave number boundary of spectral nudging	Wave length: longer than 800 km Height: over 2 km above sea level	Wave length: longer than 500 km Height: over 7 km above sea level
Wave number boundary of spectral nudging	(von Storch et al. 2000; Nakano et al. 2021)