RESUMO
The Antarctic Peninsula (AP) has displayed a propensity for persistent blocking ridges and anticyclonic conditions, particularly during recent summertime extreme weather events. This study investigates atmospheric blocking patterns over the AP through historical (1981-2010) and future (2071-2100, SSP5-8.5) periods using ERA5 reanalysis and six CMIP6 models, including multi-member realizations from two models totaling ten simulations. We focus particularly on 500 hPa geopotential height (Z500) and near-surface air temperature (T2m) anomalies. The historical analysis highlights significant differences between the CMIP6 models and ERA5 reanalysis, especially in the austral winter, with EC-Earth3 and INM-CM4 models matching closest with the ERA5. Future projections show that while the northern AP and the Drake Passage largely do not exhibit a clear trend towards increased blocking, there are exceptions. The EC-Earth3 model predicts more blocking-like conditions northwest of the AP in summer and a pronounced ridge over the Bellingshausen Sea in winter, indicating a potential increase in blocking events. The INM-CM4 model projects a minor increase in summer Z500 heights off the western and southern AP, without clear blocking patterns over the AP, and negligible winter changes. Localized intensification is noted in the northern parts of the blocking domain and southern AP during extreme blocking conditions. These variations are mirrored in T2m anomalies, suggesting warming in the northern and southern sections of AP but little change elsewhere. The results of this study underscore the need to more accurately capture complex blocking mechanisms and their impacts on regional climate patterns around the AP. We also suggest employing refined blocking definitions and incorporating a broader range of climate models to enhance our understanding of blocking patterns and their impacts in a changing climate.
RESUMO
From January to March 2018, one of the strongest Madden-Julian Oscillation (MJO) events of the last 45 years progressed eastward along the equator from the Indian Ocean to the Pacific Ocean then back to the Indian Ocean. In response to strong tropospheric heating in the MJO's active convective envelope, several pronounced Rossby wave trains developed and extended from the equatorial tropics, across the extratropical Pacific and North America, and into the extratropical Atlantic. The origins of these Rossby wave trains evolved eastward with time, generally following the eastward progression of the MJO, but preferentially clustered in subtropical India and Southeast Asia and in two locations in the subtropical Pacific Ocean: along 160°E and 170°W. Over eastern North America, surface and lower-tropospheric temperatures rose to more than 12 °C above normal when the MJO convective envelope was over the Indian Ocean (in mid-January) and Western Hemisphere (in late February). In between those warm periods, temperatures cooled to below normal while the MJO convection was over the western Pacific. These temperature anomalies evolved in time with the pronounced Rossby wave trains that linked eastern North America with the Tropics in the Eastern Hemisphere: warm temperatures occurred when ridging was present over eastern North America and cooler temperatures occurred when troughing was present. This variability is discussed and placed in context of recent work showing the MJO's role in modulating temperature and circulation.