Reconciling different methods of high‐latitude blocking detection

Blocking is associated with outbreaks of easterlies induced by a continuum features including anticyclones, cyclones or both. identification methods disagree on the levels high-latitude blocking (HLB) activity. We investigate cause disagreement in HLB activity over Northern Hemisphere obtained two 2D methods: PV– θ index and Absolute Geopotential Height (AGH) reversal method. Although both classify as absolute field methods, former yields nearly twice winter latter show that this discrepancy caused addition poleward criterion AGH method requires strong westerlies. The additional shifts focus detection ridges thus other circulation patterns are under-represented. Both agree climatology midlatitude because has been tuned to capture blocking, but grows high latitudes. HLBs different they occur northern flank westerlies equatorward displacement jet. anticyclones weaker do not induce compared their counterparts. implementation strict designed identify blocks rejects many HLBs. use less cut-off threshold (CT) 0 m (°lat)−1 for latitudes higher than 60°N results convergence climatology, interannual variability trends between especially during winter. identified modified algorithm develop from cyclonic wave breaking typical oceanic blocking. can be useful detecting more robust climate model projections.