An airborne study of an atmospheric river over the subtropical Pacific during WISPAR: Dropsonde budget-box diagnostics and precipitation impacts in Hawaii

TitleAn airborne study of an atmospheric river over the subtropical Pacific during WISPAR: Dropsonde budget-box diagnostics and precipitation impacts in Hawaii
Publication TypeJournal Article
Year of Publication2014
AuthorsNeiman PJ, Wick GA, Moore BJ, Ralph FM, Spackman J.R, Ward B.
JournalMonthly Weather Review
Volume142
Pagination3199-3223
Date Published2014/09
Type of ArticleArticle
ISBN Number0027-0644
Accession NumberWOS:000341171100010
Keywordscalifornia; connection; cyclones; extreme precipitation; satellite; scale; Storm; variability; water; winter
Abstract

The Winter Storms and Pacific Atmospheric Rivers (WISPAR) experiment was carried out in January-March 2011 from the National Aeronautics and Space Administration (NASA) Dryden Flight Research Center as a demonstration for utilizing unmanned aerial systems in meteorological research and operations over data-sparse oceans. One of the campaign's three missions was coordinated with a manned National Oceanic and Atmospheric Administration Gulfstream-IV (G-IV) flight out of Honolulu, Hawaii, on 3-4 March 2011. The G-IV, which flew through a developing atmospheric river (AR) west of Hawaii, represents the cornerstone observing platform for this study and provided the southernmost dropsonde observations of an AR published to date in the subtropical Northern Hemisphere. The AR exhibited characteristics comparable to those observed in previous studies farther north in the subtropics and midlatitudes, save for larger integrated water vapor and weaker winds in the AR core and stronger equatorward vapor fluxes in the shallow post-cold-frontal northeasterly flow. Eight dropsondes released in a similar to 200-km-wide box formation provided a novel kinematic assessment of tropospheric vorticity, divergence (mass, water vapor, sensible heat), and vertical velocity in the AR region, as well as sea surface fluxes. The budget-box diagnostics were physically consistent with global-gridded reanalysis datasets, while also providing useful additional kinematic and thermodynamic information on the mesoscale. Meteorological impacts of the AR were assessed on Hawaii's island of Kauai, where the state's heaviest rainfall was observed for this case. Rainfall on Kauai was modulated significantly by its steep orography, including on the normally dry side of the island where heavy rains fell.

DOI10.1175/mwr-d-13-00383.1
Short TitleMon. Weather Rev.
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