Global trends in the occurrence and characteristics of blocking anticyclones using Şen innovative trend analysis

Atmospheric blocking plays an important role in modulating mid-latitude weather, particularly for the Northern Hemisphere (NH). Trend analysis of atmospheric blocking for both hemispheres using Şen’s innovative trend analysis (ITA) is performed here. The blocking data archived at the University of Missouri which covers the period of 1968–2019 for NH and 1970–2019 for the Southern Hemisphere (SH) is used in this study. Block occurrence (BO), duration (BD), and blocking intensity (BI) are analyzed by classifying the NH (SH) into three groups according to the preferred block formation locations: Atlantic, Pacific, and Continental (Atlantic, Pacific, and Indian). In the NH, BI showed mixed results. There was a decreasing trend for the entire hemisphere and Atlantic Region while different trends were observed elsewhere. For BO and BD, the entire hemisphere and all regions showed increasing trends, which were statistically significant. In SH, BI shows a decreasing trend for weaker blocking events while medium and high clusters for the entire hemisphere. The BD exhibited an increasing trend for the entire SH. The BO also showed an increasing trend except one point in less active years. Blocking characteristics show different trends for different preferred blocking locations. Increasing trends of SH BO for the overall sample and Pacific Region are statistically significant at 95% level. Increasing trends for SH BD overall and in the Atlantic and Pacific regions are statistically significant at 90%, 95%, and 95% levels, respectively.