Howell fills one of the last holes on the roster as the situational lefty out of a bullpen that is potentially as loaded as the overflowing starting rotation.
The Dodgers wanted a veteran lefty because Scott Elbert is returning from elbow surgery and Paco Rodriguez has only one month of Major League experience. Those are the only other lefty relievers on the 40-man roster.
The soft-tossing Howell joins a bullpen of predominantly right-handers, most of them hard throwers -- Brandon League, Kenley Jansen, Ronald Belisario, Matt Guerrier, Javy Guerra and Shawn Tolleson.
But Jansen is coming off heart surgery, Guerrier a strained forearm tendon and Guerra shoulder surgery.
Howell, 29, went 1-0 with a 3.04 ERA in 55 games for the Rays in 2012, with 42 strikeouts and 22 walks in 50 1/3 innings. He missed the entire 2010 season with a shoulder injury that required surgery for a torn labrum.
Howell, who attended USC and the University of Texas at Austin, was a first-round pick of the Royals in 2004 and was traded to the Rays in '06. He was 6-1 with a 2.22 ERA in 64 games in '08 and followed that with a 2.84 ERA in 69 games in '09 before the injury.
Ken Gurnick is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.