Climatology of Banded Precipitation over the Contiguous United States

• Published in: Monthly weather review 2016-12, Vol.144 (12), p.4553-4568
• Main Authors: Fairman, Jonathan G, Schultz, David M, Kirshbaum, Daniel J, Gray, Suzanne L, Barrett, Andrew I
• Format: Article
• Language: English
• Subjects: Algorithms; Annual precipitation; Aspect ratio; Atmospheric sciences; Automation; Climate; Climatology; Detection; Environmental science; Freshwater; Gradients; Image detection; Lakes; Mathematical models; Maxima; Meteorology; Precipitation; Precipitation (meteorology); Precipitation bands; Radar; Radar detection; Radar imagery; Radar imaging; Radar signatures; River valleys; Rivers; Storm development; Storms; Warm seasons; Winter
• ISSN: 0027-0644; 1520-0493
• DOI: 10.1175/MWR-D-16-0015.1

A climatology of banded-precipitation features over the contiguous United States from 2003 to 2014 is constructed. A band is defined as a precipitation feature with a major axis of 100 km or greater and a ratio of major axis length to minor axis length (hereafter, aspect ratio) of 3:1 or greater. By applying an automated feature-based detection algorithm to composite radar imagery, a database of 48 916 844 precipitation features is created, of which 7 213 505 (14.8%) are bands. This algorithm produces the first climatology of precipitation bands over the contiguous United States. Banded-precipitation occurrence is broadly similar to total precipitation occurrence, with a maximum of 175 h of banded precipitation annually over the Ohio River valley. In the warm season, there is a strong diurnal signature associated with convective storm development for both the precipitation feature area and total area covered by precipitation, but little diurnal signature in aspect ratio. Strong west-east gradients in both precipitation occurrence and banded-precipitation occurrence exist, as areas west of the Rockies receive less frequent precipitation, which is much less likely to be banded. East of the Rockies, precipitation features are banded 30% of the time, versus 10%-15% west of the Rockies. Areas downwind of the Great Lakes show prominent late autumn and winter maxima in banded precipitation associated with lake-effect snowbands. Local maxima of banded-precipitation percentage occur in the Dakotas and east of the Colorado Rockies during winter. Although banded-precipitation features compose only 14.8% of all precipitation features, they contribute 21.9% of the annual precipitation occurrence over the contiguous United States.