Seasonal And Interannual Variability Of The Zonal Structure Of Hadley Circulation Over Northern Pacific Ocean

As a key component of mean meridional circulation, Hadley circulation plays animportant role in maintaining heat and angle momentum banlance in the low latitude region, andaffecting extratropical climate change. Seasonal and interannual variability of zonal structure ofHadley Circulation over the northern Pacific Ocean is examined with reanalysis data for the periodof1979–2010from NCEP/NCAR. The seasonal upward flow shows a slope from northwest tosoutheast in the western Pacific Ocean, whose vertical maximum is located near the middle of thetroposphere and zonal maximum at about180°(150°E) in boreal winter (summer); while thepermanent upward flow dominates mid-eastern Pacific Ocean, whose vertical maximum lies in thelower layer of troposphere, with a zonal structure enhancing from west to east. The pattern of thecirculation in boreal winter could be divided into three areas based on the zonal structure. The areawest of155°E appears convergent in the lower layer and divergent in the higher layer, the area of155°E-125°W appears convergent in the higher layer, the area east of130°W appears convergentin the lower layer and divergent in the higher layer. Similarly, the pattern in boreal summer couldalso be divided into three areas as follows. The area west of155°E appears East Asia SummerMonsoon(EASM)-dominated, the area of155°E-145°W appears a transition zone, the area east of145°W appears dominated by Hadley circulation. In the interannual time scale, Hadley circulationshows a strong correlation with ENSO, which is in concord with what others described previously.