|Title||Climatological characteristics of atmospheric rivers and their inland penetration over the Western United States|
|Publication Type||Journal Article|
|Year of Publication||2014|
|Authors||Rutz J.J, Steenburgh W.J, Ralph FM|
|Journal||Monthly Weather Review|
|Type of Article||Article|
|Keywords||Climatology; connection; cool season; cyclones; Flood events; Hydrometeorology; moisture; mountains; northern california; Orographic effects; precipitation; rainfall; satellite; tropospheric rivers; winter|
Narrow corridors of water vapor transport known as atmospheric rivers (ARs) contribute to extreme precipitation and flooding along the West Coast of the United States, but knowledge of their influence over the interior is limited. Here, the authors use Interim European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-Interim) data, Climate Prediction Center (CPC) precipitation analyses, and Snowpack Telemetry (SNOTEL) observations to describe the characteristics of cool-season (November-April) ARs over the western United States. It is shown that AR frequency and duration exhibit a maximum along the Oregon-Washington coast, a strong transition zone upwind (west) of and over the Cascade-Sierra ranges, and a broad minimum that extends from the high Sierra south of Lake Tahoe eastward across the central Great Basin and into the deep interior. East of the Cascade-Sierra ranges, AR frequency and duration are largest over the interior northwest, while AR duration is large compared to AR frequency over the interior southwest. The fractions of cool-season precipitation and top-decile 24-h precipitation events attributable to ARs are largest over and west of the Cascade-Sierra ranges. Farther east, these fractions are largest over the northwest and southwest interior, with distinctly different large-scale patterns and AR orientations enabling AR penetration into each of these regions. In contrast, AR-related precipitation over the Great Basin east of the high Sierra is rare. These results indicate that water vapor depletion over major topographic barriers is a key contributor to AR decay, with ARs playing a more prominent role in the inland precipitation climatology where lower or less continuous topography facilitates the inland penetration of ARs.
|Short Title||Mon. Weather Rev.|
This paper uses gridded atmospheric analyses and daily precipitation datasets to expand our knowledge of cool-season atmospheric rivers over the western United States. Results indicate that water vapor depletion over major topographic barriers is a key contributor to atmospheric river decay, with ARs playing a more prominent role in the inland precipitation climatology where lower or less continuous topography facilitates the inland penetration of ARs.