《Role of Ferrel cell in daily variability of Northern Hemisphere Annular Mode》.pdf

Chin．Sci．Bul1．(2014)59(27)：3457—3464 csb．scichina．com D0Il0．1007／slJ434—014—0477—1 www．springer．com／scp RoleofFerrelcellindailyvariabilityofNorthernHemisphere AnnularM ode Xiao-FengLiJ‘ianpingLi· XiangdongZhang。ChengSun Received：12February2014／Accepted：4M fdy2014／Publishedonline：12June2014 ◎ ScienceChinaPressandSpringer—VerlagBerlinHeidelberg2014 Abstract The Northern Hemisphere Annular Mode CellandtheNAM ，andmayprovideskillfulinformation (NAM1rer’resentsthezonally symmetricplanetary—scale ofr improving NAM as well as daily scale weather atmospheric massfluctuationsbetween middle and high prediction． 1atitudes．whosevariationshaveshownalargeimpacton othercomponentsoftheclimatesystem．Previousstudies Keywords Northern HemisphereAnnulra Mode haveindicatedthattheNAM iscorrelatedwiththeFerrel Ferrelcel1．Zonalmeancirculations．MaSS cell in their monthly or longer timescale variability． transportation ·Surfacepressuretendency · However，therehavebeenfew studiesinvestigatingtheir Prediction ·Dailyvariability connectionsatdailytimescale，thoughdailyvariabilityof NAM hasbeen suggestedtobean importantcomponent andhassignificantimplicationforweatherforecast．The 1 Intr0ducti0n resultsfrom thisstudydemonstratethatvariabilityofthe FerrelcellleadsthatoftheNAM byabout1-2days．This The Northern Hemisphere Annular Mode fNAM) is statistically identifiedtemporalphasedifferencebetween definedastheleadingempiricalorthogonalfunction(E0F) NAM and Ferrelcellvariability can be elucidated by mode oftheextratropica1wintertime monthly sea level meridionalmassredistribution．Intensified (weakened) pressure (SLP)anomaliesin theNorthernHemisphere Ferrelcellcausesanomalouslysmaller(1rager)poleward (NH)[1，2]．TheNAM ischraacterizedbyitszonalsym— mass transportrfo