Response of thunderstorm activity to ENSO events in East Asia and the Western Pacific region

This study utilized the Thunderstorm Feature Dataset (TFD), combined with the sea surface temperature (SST) anomalies over the NINO3.4 region (ENSO index) from the NOAA/ERSSTv5 dataset and ERA5 reanalysis data, to investigate the response of thunderstorm activity in East Asia and the Western Pacific region to ENSO events, an aspect that has been seldom addressed in previous studies. Results indicate ENSO events as the primary factors influencing the interannual variation of thunderstorm activity in the study area, with thunderstorm activity anomalies negatively correlated with the ENSO index, lagging by approximately 3 months. Regionally, thunderstorm activity anomalies and the ENSO index show a strong positive correlation in areas north of 20°N, encompassing Southeastern China land and adjacent sea area, but a negative correlation in areas south of 20°N, including the South China Sea, the Philippine Islands, and parts of the Western Pacific. Thunderstorm activity anomalies in these areas all lag the ENSO index by 1–3 months. The response of thunderstorm activity to ENSO events demonstrates a strong correlation with anomalies in convective parameters such as convective available potential energy (CAPE), K index, the mid-level (700–400 hPa) averaged relative humidity, and 500 hPa vertical velocity. During El Niño, warm SST in the central and eastern equatorial Pacific, along with enhanced upward motion, leads to anomalous downward motion and anticyclonic circulation in the Western Pacific region within the study area, resulting in a decrease in thunderstorm activity. Concurrently, the anomalous anticyclonic circulation in the Western Pacific region enhances the warm, moist southwest winds, which transport more water vapor to Southeastern China, thereby increasing thunderstorm activity. Conversely, during La Niña, the anomalous cyclonic circulation and moisture convergence in the Western Pacific region result in an increase in thunderstorm activity in the Western Pacific region within the study area. Additionally, the anomalous cyclonic circulation leads to a weakening of the warm and moist southwest winds and upward motion in the Southeastern China land area, consequently reducing thunderstorm activity.