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A moisture budget perspective of the amount effect
Author(s) -
Moore M.,
Kuang Z.,
Blossey P. N.
Publication year - 2014
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 - 10.1002/2013gl058302
Subject(s) - moisture , evaporation , atmospheric sciences , water vapor , precipitation , environmental science , convection , meteorology , geology , physics
A stable water isotopologue‐enabled cloud‐resolving model was used to investigate the cause of the amount effect on the seasonal (or longer) time scales. When the total water (vapor and condensed phase) budget of the precipitating column of air is considered, our results indicate that as convection becomes stronger and the precipitation rate increases, the δ D of precipitation ( δ D p ) depends on the isotopic composition of the converged vapor more than that of surface evaporation. Tests with disabled fractionation from rain evaporation demonstrate that this mechanism does not account for the amount effect as has been previously suggested. If the isotopic content of converged vapor is made uniform with height with a value characteristic of surface evaporation, the amount effect largely disappears, further supporting the dominance of converged vapor in changes to the δ D p signal with increasing precipitation. δ D p values were compared to the water budget termE P , where P is precipitation and E is evaporation. Results from this comparison support the overall conclusion that moisture convergence is central in determining the value of δ D p and the strength of the amount effect in steady state.