Metrics of the Hadley circulation strength and associated circulation trends

Abstract. This study compares trends in the Hadley cell (HC) strength using different metrics applied to ECMWF ERA5 and ERA-Interim reanalyses for period 1979–2018. The HC is commonly evaluated by derived from mass-weighted zonal-mean stream function isobaric coordinates. Other include upper tropospheric velocity potential, vertical mid-troposphere, water vapour transport lower troposphere. Seven known of are complemented here a metric spatially averaged strength, obtained averaging latitude–pressure (?–p) plane, total energy unbalanced circulation normal-mode decomposition. It shown that metrics, which rely on single-point values ?–p produce unreliable 40-year both northern southern HCs, especially ERA-Interim; magnitudes even signs depend choice metric. two new alleviate meridional inhomogeneities strength. suggests positive trend reanalyses, whereas based finds significant only ERA5.