Isotope ratios of precipitation and water vapor observed in Typhoon Shanshan

Abstract

[1] Isotope ratios of precipitation and water vapor were observed during the passage of Typhoon Shanshan at Ishigaki Island, southwestern Japan, on 15-16 September 2006. Such high-resolution isotopic observations allow for qualitative understanding of atmospheric moisture cycling; they revealed that isotope ratios of both the precipitation and water vapor decreased radially inward in the cyclone's outer region; anomalously high isotope ratios appeared in the cyclone's inner region; and d-excess tended to decrease in the cyclone's inner region. In the cyclone's outer region, the water vapor was isotopically depleted due to the rainout effect which involves both condensation efficiency as reflected in inwardly increasing cloud thickness and isotopic exchange between falling droplets and the ambient water vapor. In contrast, water vapor in the cyclone's inner region was isotopically enriched due to weak rainout effect in conjunction with intensive isotopic recharge from the sea spray and sea surface with heavy isotope ratios. Since water vapor mainly acts as a source of precipitation, the isotope ratios of precipitation also had systematic variation. A unique circumstance is the intensity of isotopic exchange with almost saturated surface air and high winds, causing anomalously high isotope ratios and low d-excess values in the cyclone's inner region.

Effects of Large-scale Moisture Transport and Mesoscale Processes on Precipitation Isotope Ratios Observed at Sumatera, Indonesia

“…Sugimoto and Higuchi (1988) reported large (small) decreases in precipitation isotope ratios when the precipitation intensity was high (low). Fudeyasu et al (2008) found increases in the isotope ratios of precipitation accompanying a tropical cyclone eyewall. Dansgaard (1953) observed that isotopic ratios in precipitation did not vary with time throughout a rain shower.…”

An estimation of water origins in the vicinity of a tropical cyclone’s center and associated dynamic processes

“…Another serious problem is that the inner structure of the TC is not resolved because, in K2014, the ICM incorporates an external meteorological data set derived from a global atmospheric reanalysis with a horizontal grid of 1.25° longitude by 1.25° latitude. If we also consider the results of Fudeyasu et al (2008), who observed the isotope ratios of precipitation and water vapor during the passage of a typhoon, we may, thus, underestimate the proportion of underlying ocean vapor to total precipitable water in the vicinity of the TC's center.…”

Isotopic Variations Associated with North-South Displacement of the Baiu Front

“…This is because the strong southerly flow of typhoons brings heavy rainfall, which has extremely low isotopic contents (e.g., Fudeyasu et al 2008). Thus, we ignored typhoon years (1963, 1965, 1966 and 1974) from the analysis (shaded in blue in Fig.…”