Differences in Sea-Effect Clouds and Precipitation between the Sea of Japan and Japanese Mountains

Prolific winter (DJF) snowfall occurs over the mountains of northwest Japan due largely to sea-effect precipitation that develops during cold-air outbreaks over the Sea of Japan (SOJ). Knowledge of the sea-effect transition from the SOJ to the complex terrain along the length of the Japanese coast has historically been constrained, however, by a lack of offshore surface and radar observations and the limitations of passive space-borne remote sensing. This work uses active space-borne sensors from NASA’s A-Train Constellation to examine sea-effect cloud and precipitation properties across the SOJ region during seven winters. The analysis shows that these properties vary across the region, with cloud occurrence and heights comparatively low near the Asian coast, higher over the SOJ (especially in areas of frequent flow convergence), and highest along complex terrain of the western Japanese coast. Precipitation characteristics follow a similar overall trend, but further analysis reveals differences in the precipitation maxima location with respect to the Japanese orography. The maxima are upstream of the coast of southern Honshu, along the coast and over complex terrain at central Honshu, and range from near the coast to over complex terrain at Hokkaido. Precipitation tends to decline with inland extent, but most abruptly downstream of larger and steeper mountain barriers. These results illustrate that despite prevalent sea-effect clouds and precipitation throughout the region, the impact of mesoscale circulations over the SOJ combined with downstream coastal and orographic effects produce variations in the location of enhanced sea-effect clouds and precipitation.