A peer-reviewed modeling study links the unusually warm Sea of Japan to stronger rainfall during Japan’s September 2024 Noto disaster. With atmospheric conditions held fixed, simulations using historical sea temperatures produced substantially less rain at Wajima. Stronger winds carrying moisture into the rain front accounted for more of the difference than added water vapor alone.
A peer-reviewed atmospheric modeling study reconstructed the rain that struck Noto, a region of Japan, on 20–22 September 2024. At Wajima, the simulation using that year’s sea temperatures produced 382 mm over 72 hours. Experiments replacing Sea of Japan temperatures with historical values averaged 210 mm. Atmospheric conditions remained fixed, allowing the comparison to isolate sensitivity to the specified ocean conditions.[1]
A small low-pressure system appeared across the experiments, taking broadly the same route. Under the warmer 2024 conditions, however, it intensified and strengthened southwesterly winds carrying moisture toward the rainfall front. Wind changes contributed more to the moisture-transport difference than increased water vapor alone. For that September, the sea temperature anomaly relative to 1991–2020 averaged 2.9 degrees Celsius; temperatures from those 30 historical years supplied the comparison experiments.[1]
The control reproduced the geographical rainfall pattern but gave a rainfall onset about 3–4 hours late at Wajima, with a total roughly 80 per cent of observations. Ocean analysis also found a stronger Tsushima Warm Current in 2024. Its separate contribution to the heat extreme was not quantified. Because mean sea temperature, spatial gradients and their evolution changed together, the experiments could not separate their individual contributions.[1]
