Active typhoon season and monsoons split Asia’s November irradiance

A stronger-than-usual end to the typhoon season has shaped solar irradiance outcomes across Asia in November, delivering a mix of results for the region. Lowlying regions of China have experienced up to 30% more irradiance than normal in November, whilst the Korean Peninsula, Philippines and Northern Japan saw 10-20% more solar production than normal.

In the Philippines, irradiance was up to 20% above climatology for November, marking a strong month for most of the region. However, northern Luzon faced a notable exception due to an active tropical season, with typhoons Usagi and Man-yi occurring concurrently in the South China sea. Historical weather patterns show this November as unusually intense, with multiple tropical systems forming at the same time.

The clustering of these systems, Usagi, Man-yi, and Toraji, continued to suppress irradiance levels in northern Luzon through extensive cloud cover and precipitation while much of the archipelago remained largely unaffected.

Across Southeast Asia, the onset of the monsoon season led to heavy rainfall and flash flooding, particularly in Java, Malaysia, and western Thailand. Warmer-than-usual conditions and positive sea surface temperature anomalies amplified rainfall intensity, driving irradiance well below average for these regions. Sumatra, however, presented a split pattern. The west coast saw higher-than-average irradiance due to clearer skies, while the eastern side experienced below-average conditions, likely linked to persistent cloud cover and moisture transport from the adjacent seas.

In stark contrast, Cambodia, South Vietnam and southern China experienced higher than normal irradiance as a result of Madden-Julian Oscillation (MJO) phase. Cambodia recorded irradiance levels up by 15% compared to climatology, while southern China saw even stronger anomalies, with irradiance reaching up to 30% above average. This clear-sky dominance resulted from stable weather patterns brought by the MJO, which inhibited cloud formation and delivered sustained clear conditions across the region.

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