Factors and Mechanisms Affecting the Air Temperature Distribution on a Clear Winter Night in a Snow-Covered Mesoscale Plain

Abstract

There is an increasing need for accurate winter agrometeorological forecasts, which is facilitated by a better understanding of the evolution process of nighttime airtemperature distribution. However, studies on how air temperature distributions evolve in mesoscale plains have been limited. To clarify how the low temperatures in winter nights form, we analyzed the effects of topography and boundarylayer wind on the temperature distribu tion of the Tokachi region for a winter night using numerical simulations by the Japan Meteorological Agency Nonhydrostatic Model (JMA-NHM) with horizontal grid spacing of 2 and 5 km. We also analyzed vertical pro files of boundary-layer atmospheric conditions. The results show that although boundarylayer wind is expected to affect the temperature distribution over the entire Tokachi region, the effects were generally confined to the northwestern part. Widespread effects over the Tokachi region were found only under strong wind conditions. We found that the mountain pass in the northwestern part of the Tokachi region is an important wind path, and the downslope winds as well as the sensible

Bias correction for spatially interpolated daily mean air temperature during winter in eastern Hokkaido using multimodal machine learning

“…The regions where the drainage flow reaches earlier night had lower daily minimum air temperatures Fukushima et al, 2019 . Since katabatic drainage flow was predicted to exist in the Tokachi and Okhotsk regions Kimura, 1986 and was observed at several sites in the Tokachi Plain Kimura, 1986;Fukushima et al, 2019 , it could cause the greater RMSE values in the present dataset. Snowpack might also be related to the formation of heterogeneous air temperature distributions.…”

“…In a clear night, near-surface wind might also affect the temperature distribution Yazaki et al, 2017 . In regions where the near-surface wind is strong, sensible heat could be supplied to the surface, compensating for longwave radiative losses. Since the wind condition should be influenced by the geography and topography around the site Fukushima et al, 2019 , the formation of the patchy low-temperature zones would be either mitigated or emphasized depending on these local features.…”

“…Yazaki et al 2017 reported that the winter air temperature in the Tokachi Plain, which is situated in the eastern part of Hokkaido Island in northern Japan, was not spatially uniform. They measured air temperatures at several sites and found that the difference in the daily minimum values at two close sites ~5 km apart was sometimes greater than 10 C. By applying a nonhydrostatic model to the region and modifying the boundary layer wind conditions, further analysis suggested that the wind and topography caused the air temperature to form a heterogeneous spatial distribution Fukushima et al, 2019 . Although several earlier studies that considered downscaling quantified the effect of local topographical features on the daily mean air temperature by applying stepwise multiple regression models e.g., Kanno, 1997;Sameshima et al, 2008;Ueyama, 2008;JMA, 2011 , interactions among the boundary layer wind, topography, and air temperature were not incorporated.…”

Molecular detection of Borrelia burgdorferi (sensu lato) and Rickettsia spp. in hard ticks distributed in Tokachi District, eastern Hokkaido, Japan

“…1 ). Detailed geographical and climate features of the Tokachi District are described by Yazaki et al (2013) and Fukushima et al (2019) . Between May and November 2017, field expeditions were performed once per month to collect questing ticks by the flagging method ( Dantas-Torres et al, 2013 ).…”

Effects of snow compaction ‘yuki-fumi’ on soil frost depth and volunteer potato control in potato–wheat rotation system in Hokkaido

“…Even the southern part (STO) of the Tokachi region often experiences a large amount of snowfall during early winter due to the strengthening of low pressure along the southern coast (Hirota et al, 2006). The northern part (NTO) experiences higher temperatures due to the warmer west wind during winter (Fukushima et al, 2019;Yazaki et al, 2017). Furthermore, farmers in other regions hope to establish a method to control soil frost depth under various meteorological conditions.…”