An Intercomparison between Reanalysis and Dropsonde Observations of the Total Water Vapor Transport in Individual Atmospheric Rivers

A recent study presented nearly two decades of airborne atmospheric river (AR) observations and concluded that, on average, an individual AR transports ∼5 × 10⁸ kg s−1 of water vapor. The study here compares those cases to ARs independently identified in reanalyses based on a refined algorithm that...

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Bibliographic Details
Published in:Journal of hydrometeorology 2018-02, Vol.19 (2), p.321-337
Main Authors: Guan, Bin, Waliser, Duane E., Ralph, F. Martin
Format: Article
Language:English
Subjects:
Aircraft
Algorithms
Atmospheric models
Climate
Coasts
Detection
Dropsonde
Dropsonde observations
Geographical variations
Humidity
Hydrologic cycle
Identification
Intercomparison
Laboratories
Modelling
Precipitation
SPECIAL MERRA-2 COLLECTION
Studies
Transport
Water vapor
Water vapor transport
Water vapour
Width
Wind
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Summary:A recent study presented nearly two decades of airborne atmospheric river (AR) observations and concluded that, on average, an individual AR transports ∼5 × 10⁸ kg s−1 of water vapor. The study here compares those cases to ARs independently identified in reanalyses based on a refined algorithm that can detect less well-structured ARs, with the dual-purpose of validating reanalysis ARs against observations and evaluating dropsonde representativeness relative to reanalyses. The first comparison is based on 21 dropsonde-observed ARs in the northeastern Pacific and those closely matched, but not required to be exactly collocated, in ERA-Interim (MERRA-2), which indicates a mean error of −22% (−8%) in AR width and +3% (−1%) in total integrated water vapor transport (TIVT) and supports the effectiveness of the AR detection algorithm applied to the reanalyses. The second comparison is between the 21 dropsonde ARs and ∼6000 ARs detected in ERA-Interim (MERRA-2) over the same domain, which indicates a mean difference of 5% (20%) in AR width and 5% (14%) in TIVT and suggests the limited number of dropsonde observations is a highly (reasonably) representative sampling of ARs in the northeastern Pacific. Sensitivities of the comparison to seasonal and geographical variations in AR width/TIVT are also examined. The results provide a case where dedicated observational efforts in specific regions corroborate with global reanalyses in better characterizing the geometry and strength of ARs regionally and globally. The results also illustrate that the reanalysis depiction of ARs can help inform the selection of locations for future observational and modeling efforts.
ISSN:1525-755X
1525-7541
DOI:10.1175/jhm-d-17-0114.1