On tropospheric rivers

• Main Author: Hu, Yuanlong, 1964-
• Other Authors: Reginald E. Newell., Massachusetts Institute of Technology. Dept. of Earth, Atmospheric, and Planetary Sciences.
• Format: Thesis
• Language: English
• Published: Massachusetts Institute of Technology 2002
• Subjects: Earth; Atmospheric; and Planetary Sciences; Gulf of Alaska; Greenland; Pacific; Indian; Alaska
• Online Access: http://hdl.handle.net/1721.1/8058

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2002. Page 231 blank. Includes bibliographical references (p. 221-230). In this thesis, we investigate atmospheric water vapor transport through a distinct synoptic phenomenon, namely, the Tropospheric River (TR), which is a local filamentary structure on a daily map of vertically integrated moisture flux. Firstly, an automated procedure for identifying and tracking these rivers (named TRICKS, i.e., the Tropospheric River Identifying and traCKing Scheme) is described and its performance is evaluated. This procedure enables the maxima of moisture flux (so-called TR cores) to be detected and accurately located. The relationships among the adjacent TR cores are then evaluated to construct the axes of rivers. A river is tracked from birth to termination and its life cycle properties are recorded, thus allowing various statistics of TR distributions and movements to be estimated. All these stages of the scheme are performed without intervention once a number of governing constants have been decided upon. We then apply the scheme to the vertically integrated moisture flux calculated from 43 years of 6-hourly NCEP/NCAR reanalyses and present a climatology of mean TR behavior. On average, there are 4 - 5 rivers per analysis in the Northern Hemisphere and 5 in the Southern Hemisphere. Northern Hemisphere TRs form and intensify near the eastern seaboards of Asia and North America. They move eastward and poleward during their lives before weakening in the two principal graveyards: over the Gulf of Alaska and the region to the southeast of Greenland. In comparison, Southern Hemisphere TRs are more evenly distributed and tend to form in a band extending from the southeast coast of South America into the Atlantic, across the Indian Ocean, and throughout much of middle latitudes of the Pacific sector. (cont.) The corresponding genesis regions are also found to be adjacent to (or slightly equatorward to) the ...