Connections between the Madden–Julian Oscillation and surface temperatures in winter 2018 over eastern North America

• Published in: Atmospheric science letters 2019-01, Vol.20 (1), p.e869-n/a
• Main Author: Barrett, Bradford S.
• Format: Article
• Language: English
• Subjects: Anomalies; Atmospheric sciences; Convection; Convection cooling; Cyclones; Eastern Hemisphere; Equator; Heating; Madden-Julian oscillation; Oceans; Planetary waves; Ridging; Rossby wave train; Rossby waves; surface air temperature variability; Surface temperature; Temperature anomalies; Tropical environments; tropical–extratropical teleconnections; Troposphere; Tropospheric temperatures; Wave packets; Wave trains; Western Hemisphere
• ISSN: 1530-261X; 1530-261X
• DOI: 10.1002/asl.869

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. Surface temperatures in the northeastern United States exhibited significant intra‐seasonal variability in winter 2018, concurrent with a record‐breaking MJO event. Very warm temperatures in early January were followed by slightly below‐normal temperatures in early February, only to be followed by very warm temperatures again in mid‐February. These temperature anomalies were connected to a train of Rossby waves emanating from the Tropics.