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Using Stable Isotopes in Water Vapor to Diagnose Relationships Between Lower‐Tropospheric Stability, Mixing, and Low‐Cloud Cover Near the Island of Hawaii
Author(s) -
Galewsky Joseph
Publication year - 2018
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2017gl075770
Subject(s) - mixing ratio , troposphere , water vapor , environmental science , atmospheric sciences , cloud cover , saturation (graph theory) , humidity , mixing (physics) , relative humidity , inversion (geology) , cloud computing , meteorology , geology , physics , mathematics , combinatorics , quantum mechanics , structural basin , computer science , operating system , paleontology
Abstract In situ measurements of water vapor isotopic composition from Mauna Loa, Hawaii, are merged with soundings from Hilo to show an inverse relationship between the estimated inversion strength (EIS) and isotopically derived measures of lower‐tropospheric mixing. Remote sensing estimates of cloud fraction, cloud liquid water path, and cloud top pressure were all found to be higher (lower) under low (high) EIS. Inverse modeling of the isotopic data corresponding to terciles of EIS conditions provide quantitative constraints on the last‐saturation temperatures and mixing fractions that govern the humidity above the trade inversion. The mixing fraction of water vapor transported from the boundary layer to Mauna Loa decreases with respect to EIS at a rate of about 3% K −1 , corresponding to a mixing ratio decrease of 0.6 g kg −1 K −1 . A last‐saturation temperature of 240 K can match all observations. This approach can be applied in other settings and may be used to test models of low‐cloud climate feedbacks.