The study looked at a pattern called the Tropospheric Biennial Oscillation (TBO) in the Western Pacific region and how it relates to sea surface temperatures and weather patterns. They found that the TBO of the Western Pacific subtropical high has become stronger since the late 1970s. During the TBO cycle, El Niño-like conditions in winter are linked to a weaker East Asian winter monsoon, while La Niña-like conditions are linked to a stronger monsoon. The TBO signal is more pronounced during El Niño-like conditions, making it important for short-term climate predictions.