Reproducibility of Surface Wind and Tracer Transport Simulations over Complex Terrain Using 5-, 3-, and 1-km-Grid Models

Abstract

The reproducibility of surface wind and tracer transport simulations from high-resolution weather and transport models was studied over complex terrain in wintertime in Japan. The horizontal grid spacing was varied (5-, 3-, and 1-km grids), and radioactive cesium (Cs-137) from the Fukushima nuclear power plant was used as a tracer. Fukushima has complex terrain, such as mountains and valleys. The model results were validated by observations collected from the national networks of the automated meteorological data acquisition system and the hourly air pollution sampling system. The reproducibility depended on the model resolution, topographic complexity, and synoptic weather conditions. Higher model resolution led to higher reproducibility of surface winds, especially in mountainous areas when the Siberian winter monsoon was disturbed. In contrast, the model improvement was negligible or nonexistent over plain/coastal areas when the synoptic field was steady. The statistical scores of the tracer transport simulations often deteriorated as a result of small errors in the plume locations. However, the higher-resolution models advantageously performed better transport simulations in the mountainous areas because of the lower numerical diffusion and higher reproducibility of the mass flux. The reproducibility of the tracer distribution in the valley of the Fukushima mountainous region was dramatically improved with increasing model resolution. In the range of mesoscale model resolutions (commonly 1-10 km), it was concluded that a higher-resolution model is definitely recommended for tracer transport simulations over mountainous terrain.

Comparison of three aerosol representations of NHM-Chem (v1.0) for the simulations of air quality and climate-relevant variables

“…The AD-Net sites are equipped with a two-wavelength (1064 and 532 nm) polarization-sensitive (532 nm) Mie-scattering lidar system. We used the extinction coefficients for non-spherical (referred to as dust) and spherical aerosols for the model evalua-tion, derived using the attenuated backscattering coefficients and the volume depolarization ratio (Sugimoto et al, 2003;Shimizu et al, 2004). The yellow star indicates the Hedo site, which belongs to both EANET and SKYNET, an air quality measurement supersite called CHAAMS (Cape Hedo Atmosphere and Aerosol Monitoring Station).…”

“…S1-1 in the Supplement. The offline coupled version has been used for various purposes, such as the simulation of dust vortices in the Taklimakan Desert (Yumimoto et al, 2019), the simulation of the dispersion and deposition of radionuclides due to the Fukushima nuclear accident (Kajino et al, 2019b(Kajino et al, , 2021Sekiyama and Kajino, 2020), simulation of lower-tropospheric ozone in East Asia (Kajino et al, 2019c), and the simulation of transition metals in East Asia (Kajino et al, 2020). Other meteorological models, such as the Weather Research and Forecast model (WRF; Skamarock et al, 2008), ASUCA (JMA, 2014;Aranami et al, 2015), and Scalable Computing for Advanced Library and Environment (SCALE; Nishizawa et al, 2015, can be used for offline coupled simulations (Fig.…”

Reassessment of the radiocesium resuspension flux from contaminated ground surfaces in eastern Japan

“…These two powerful spatiotemporal measurement datasets together with comprehensive emission scenarios provided by the Japan Atomic Energy Agency (e.g., Katata et al, 2015;Terada et al, 2020) enable us to identify transport and deposition events over the land surface in Japan (e.g., Tsuruta et al, 2014;Nakajima et al, 2017;Sekiyama and Iwasaki, 2018). These data were also useful to validate the numerical simulation results provided by various regional-scale atmospheric models (Draxler et al, 2015;Leadbetter et al, 2015;Kitayama et al, 2018;Sato et al, 2018Sato et al, , 2020Kajino et al, 2019;Goto et al, 2020) and were applied for other advanced numerical techniques, such as inverse modeling (Yumimoto et al, 2016;Li et al, 2019), ensemble forecasting (Sekiyama et al, 2021), and data assimilation (Sekiyama and Kajino, 2020).…”

Reassessment of the radiocesium resuspension flux from contaminated ground surfaces in East Japan

“…These two powerful spatiotemporal measurement datasets together with comprehensive emission scenarios provided by the Japan Atomic Energy Agency (e.g., Katata et al, 2015;Terada et al, 2020) enable us to identify transport and deposition events over the land surface in Japan (e.g., Tsuruta et al, 2014;Nakajima et al, 2017;Sekiyama and Iwasaki, 2018). These data were also useful to validate the numerical simulation results provided by various regional-scale atmospheric models (Draxler et al, 2015;Leadbetter et al, 2015;Kitayama et al, 2018;Sato et al, 2018;Kajino et al, 2019;Goto et al, 2020) and were applied for other advanced numerical techniques, such as inverse modeling (Yumimoto et al, 2016;Li et al, 2019), ensemble forecasting (Sekiyama et al, 2021), and data assimilation (Sekiyama and Kajino, 2020).…”