LAUSR

25 A novel automated scheme for identifying occluded mid-latitude cyclones from 26 gridded data sets is described and employed to construct a limited climatology of such 27 storms as well as composites of their thermodynamic and kinematic structures. The 28 climatology (2006-2017) is derived from the MERRA-2 reanalysis and reveals differences 29 in the distribution of occlusions between the hemispheres. Northern Hemisphere 30 occlusions are most frequent in winter (DJF) and are found poleward of the mean 31 tropopause-level jets in both the Atlantic and Pacific basins. In the Southern Hemisphere, 32 however, occlusions are most frequent during autumn (MAM) and are almost never found 33 equatorward of 40∘S. 34 Using the identification scheme, wintertime occlusions are stratified based upon the 35 value of 700 hPa θ" in their characteristic thickness ridges. Composites of six groups of 36 occlusions, based upon this distinction, are constructed for each hemisphere. The 37 composites reveal notable differences in the thermodynamic structures among these six 38 groups with more poleward (lower θ" or "colder") storms exhibiting shallower, less 39 developed thermal structures as compared to their lower latitude (higher θ" or "warmer") 40 counterparts. These differences are attended by contrasts in the intensity of upward 41 vertical motions in the occluded sectors of the various composite storms implying that 42 "warm" storms are associated with greater latent heat release than "colder" storms. It is 43 suggested that these coincident differences between "cold" and "warm" storms provides 44 further evidence of the fundamental importance of latent heat release to the development 45 of occluded thermal structures. 46