Objective To explore the driving mechanism of meteorological anomalies on the alternate bearing phenomenon in mid-late maturing litchi in Guangdong Province, and provide a theoretical basis for stable yield and efficiency improvement of litchi production in Guangdong Province.

Method Based on the fifth-generation global atmospheric reanalysis dataset of the European Centre for Medium-Range Weather Forecasts (ERA5), meteorological observation data and litchi production data, this study selected 2025 and 2018 as the high-yield years, and 2024 and 2019 as the low-yield years for mid-late maturing litchi in Guangdong Province. Taking four typical phenological stages, namely flower bud physiological differentiation stage, flower bud morphological differentiation stage, flowering and fruit-setting stage, and fruit development stage, as the research objects, we analyzed the differences in four meteorological factors including air temperature, precipitation, relative humidity and sunshine duration, and revealed the effects of temporal and spatial distribution differences of meteorological factors on litchi yield fluctuation.

Result The alternate bearing of mid-late maturing litchi in Guangdong Province is closely correlated with four meteorological factors: air temperature, precipitation, relative humidity and sunshine duration. Compared with low-yield years, high-yield years presented a relative humidity difference of -21% to -1% across the entire phenological period, and sunshine duration increased by 3 to 76 h/month. The temperature difference ranged from -1.6℃ to -0.1℃ during flower bud differentiation, and from -2.5℃ to -0.5℃ at the flowering and fruit-setting stage. Precipitation exerted distinct stage-specific effects on litchi yield. There was no significant difference in precipitation during flower bud differentiation between high-yield and low-yield years. However, the precipitation difference reached -410 mm to -20 mm/monthduring the flowering and fruit-setting stage and fruit development stage, indicating that a relatively dry environment is conducive to increasing litchi yield. The La Niña sea surface temperature pattern significantly intensifies the East Asian winter monsoon by modulating regional atmospheric circulation, thereby forming climatic conditions favorable for litchi yield improvement in Guangdong Province.

Conclusion The alternate bearing of mid-late maturing litchi in Guangdong Province is closely associated with fluctuations in meteorological factors throughout the whole phenological period and regional atmospheric circulation. Against the background of global warming, great importance should be attached to preventing and addressing climate risks in the litchi industry.