Contributions of Foehn and Urban Heat Island to the Extreme High-Temperature Event in Niigata City during the Night of 23-24 August 2018

Abstract

We quantitatively evaluated the contributions of foehn winds and the urban heat island (UHI) effect to an extreme high-temperature nocturnal event at Niigata city on 23−24 August 2018. During this event, southeasterly winds blew continually across the Niigata Plain and temperatures on the plain were higher than those in the windward region of the mountain range. Back-trajectory analysis and numerical simulations with and without topography showed that the southeasterly winds were foehn winds that caused precipitation and latent heating on the windward slope of the mountain range. The foehn winds and UHI contributed about 2.8°C and 1.9°C, respectively, to the extreme high-temperature of 31.0°C at 2100 JST in Niigata city. The combined impact of the foehn winds and the UHI at Niigata was about 4.0°C during the night. The contribution of the foehn winds was greater at around midnight, whereas that of the UHI was greater during the early night.

Future changes of the extreme high‐temperature events influenced by foehn winds in Niigata, Japan

“…In recent years, numerous reports have suggested that foehn wind‐induced warming plays an important role in the collapse of Antarctic ice shelves (Cape et al, 2015; Elvidge et al, 2020; Speirs et al, 2013; Vüllers et al, 2018). In Japan, many studies on the relationship between ETEs and foehn winds also have been conducted in the last decade (Mori & Sato, 2014; Nishi et al, 2019, 2022; Nishi & Kusaka, 2019; Takane et al, 2014, 2015; Takane et al, 2017; Takane & Kusaka, 2011; Watarai et al, 2009). Takane and Kusaka (2011) and Nishi and Kusaka (2019) showed that foehn winds were predominant during the historical ETEs (inferred from maximum temperature records) that occurred in the Kanto Plain, located on the Pacific side of Japan (Figure 1).…”

Japan's south foehn on the Toyama Plain: Dynamical or thermodynamical mechanisms?

“…In 2018, the record was broken again due to foehn warming (Nishi and Kusaka, 2019). Extremely high‐temperature, nocturnal events in Niigata Prefecture in 2018 were also caused by foehn warming (Nishi et al ., 2019). In Japan, dry, strong, nocturnal foehn winds cause rice crops to suffer from lower the grain quality and yield (e.g., Muramatsu, 1976; Wada et al ., 2011).…”

“…The south foehn blows across the Sea of Japan side of Honshu (main island of Japan) (Arakawa et al ., 1982; Nishi et al ., 2019), Hokkaido (Mori and Sato, 2014), and Shikoku (Saito and Ikawa, 1993; Saito, 1994). The south foehn on the Hokuriku region in Honshu is the representative foehn in Japan.…”

“…South foehn warming may be explained by two types of warming mechanisms—those governed by dynamical and thermodynamical mechanisms (Arakawa et al ., 1982). However, which is the primary type is unknown, and only a few studies have been conducted on the path of Japan's south foehn (e.g., Arakawa et al ., 1982; Ishizaki and Takayabu, 2009; Nishi et al ., 2019). Arakawa et al .…”

Numerical simulation study of the effects of foehn winds on white head incidences in Yamagata Prefecture, Japan

“…Foehn has been observed worldwide, including the European Alps (Hoinka, 1985; Mayr et al, 2007; Seibert, 1990; Würsch & Sprenger, 2015), the Rocky Mountains (Baren, 1967; Durran, 1986; Klemp & Lilly, 1975), Antarctica (Elvidge et al, 2015; Elvidge et al, 2016; Elvidge & Renfrew, 2016), the Andes (Norte, 2015; Puliafito et al, 2015; Seluchi et al, 2003) and the South Island of New Zealand (McGowan et al, 2002; McGowan & Sturman, 1996). In the Hokuriku region of Japan, foehn is observed when cyclones or typhoons pass the Sea of Japan (Arakawa et al, 1982; Koyanagi & Kusaka, 2020; Kusaka et al, 2021; Nishi et al, 2019).…”