Several of the nation's best-known top cops left their big-city police chief positions in 2009 amid a year of budget turmoil, a spike in officer deaths, and shifting law enforcement priorities.

Next year, 10 of the nation's most populous cities will have new chiefs — Atlanta, Dallas, Detroit, Houston, Los Angeles, Miami, Oakland, San Francisco, Seattle and Tampa.

The number of departures isn't as unusual as the names of the chiefs leaving, a leading police union official tells POLICE Magazine.

"It's somewhat cyclical," said Jim Pasco, executive director with the national Fraternal Order of Police. "The real high-profile chiefs with a track record of accomplishment seem to be doing so on their own volition and at an appropriate time for them."

Pasco estimated that most big-city chiefs serve for just over two years before leaving.

Chiefs entering jobs in Detroit and Oakland are taking on challenging turnaround assignments in higher crime areas. They'll have a lower bar for success, yet also will be under closer scrutiny.

"Generally, in those cities there's a high level of frustration," Pasco added. "Their [city leaders and community members] expectations are going to be high and they're going to be impatient."

To help officers follow the changes at the top, POLICE Magazine has prepared a handy guide to all the moves. View them on the next two pages.[PAGEBREAK]

Atlanta

Out:Richard Pennington

In: George Turner (interim)

Why: Pennington had battled with the city's police union, who questioned his absence during several high-profile crimes, including the killing of a 92-year-old during a botched drug raid.

Dallas

Out: David Kunkle

In: Pending

Why: In November, Kunkle announced he would retire by April after more than five years as chief. Kunkle said it was the "right time to go," after 38 years with a department where he started as a patrol officer.

Detroit

Out: James Barren

In:Warren Evans

Why: In August, Evans took over a city that was at the top of the nation in homicides and violent crimes. A former sheriff, he promised to tame the "wild wild West" climate.

Houston

Out:Harold Hurtt

In: Pending

Why: Houston's mayor-elect Annise Parker called for new police leadership in December after criticizing the command staff for a 40 percent budget increase over six years without hiring additional officers.

Los Angeles

Out:William Bratton

In:Charlie Beck

Why: Bratton left in October, following the lifting of the consent decree imposed after the Rampart scandal. He took a job at a private security firm in New York, where he had previously served as police commissioner.[PAGEBREAK]

Miami

Out:John Timoney

In: Miguel Exposito

Why: Timoney resigned in November after the election of Mayor Tomas Regalado. The new mayor campaigned for new leadership, siding with the police union who cited low patrol morale. Timoney had been criticized for using an SUV from a local car dealer.

Oakland

Out: Wayne Tucker

In:Tony Batts

Why: Batts takes over a department reeling from the deaths of four officers ambushed by a parolee, threatened budget cuts, and a technologically outdated crime mapping system. He oversaw a reduction  in crime as the chief of the Long Beach (Calif.) Police Department.

San Francisco

Out:Heather Fong

In:George Gascon

Why: Mayor Gavin Newsom hired Gascon, a former LAPD deputy chief, from the Mesa (Ariz.) Police Department to modernize the department.

Seattle

Out: Gil Kerlikowske

In: Pending

Why: Kerlikowske left in March to become the federal drug czar in the Obama Administration. Mayor-elect Mike McGinn is restarting a stalled search process put on hold by the former mayor's loss in a primary election.

Tampa

Out: Steve Hogue

In:Jane Castor

Why: Hogue retired after six years as chief. Castor became the first female (and openly gay) chief in Tampa, and downplayed her trailblazing.