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Sensitivity of quantitative precipitation forecast to height dependent changes in humidity
Author(s) -
Keil Christian,
Röpnack Andreas,
Craig George C.,
Schumann Ulrich
Publication year - 2008
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 - 10.1029/2008gl033657
Subject(s) - humidity , precipitation , environmental science , atmospheric sciences , boundary layer , convective boundary layer , troposphere , convection , relative humidity , climatology , planetary boundary layer , meteorology , geology , mechanics , geography , physics
The impact of humidity variations on QPF is studied performing a series of sensitivity experiments with the COSMO model at a horizontal mesh size of 7 km. Generally, variations of humidity in the boundary layer have the largest impact on precipitation, and the sensitivity decreases with height. An increase of humidity by 10% in the boundary layer is equivalent to an increase of 20% in the mid‐troposphere. While the impact of humidity variation on stratiform precipitation persists throughout the 36‐h forecast period, the impact diminishes after 24 h in the convective rainfall area. Increasing the boundary layer humidity by 30% leads to a 6 h earlier initiation of convection and a five times larger precipitation amount in the convective area, whereas it is doubled in the stratiform region. These results indicate that accurate measurements of humidity in the boundary layer are most important for QPF.