第二届未来大气科学论坛

The impact of vegetation on precipitation is complex, varying with spatial scale and synoptic forcing. Large-scale (~100–1000s km) vegetation impacts on precipitation are well documented, whereas evidence for local-scale (~1–100 km) effects remains limited. At local scales such as ecotones, surface heterogeneity can generate mesoscale circulations that, in turn, modulate rainfall. Previous studies indicate that mid-latitude vegetation asymmetrically regulates daytime and nighttime temperatures, yet the diurnal temperature gradients in many ecotones may be reshaped under widespread greening and rapid warming. Here, we investigated the combined effects of vegetation and synoptic forcing on warm-season (May–September) diurnal rainfall during 1981–2020 in the crop-forest ecotone of Liaoning Province, Northeast China, as a representative case of local scale vegetation–precipitation feedback under climate change. Using four decades of satellite and reanalysis data, we found a significant decline in midday-to-afternoon (11–17 local time) low-intensity rainfall amount (below the 50^th percentile, <0.6 mm h⁻¹), primarily driven by reduced event frequency rather than changes in intensity. No significant trends were observed in nocturnal rainfall. Synoptic classification revealed that one dominant weak-forcing pattern (T3) accounted for most of the midday and afternoon decline. Under this pattern, weak large-scale ascent, together with less effective mesoscale ascent linked to an enhanced crop–forest thermal contrast, weakened vertical motion and likely contributed to reduced rainfall. Given continued future warming and persistent vegetation greening, the mechanisms identified here may have broader relevance for understanding how vegetation modulates local precipitation under climate change.
The impact of vegetation on precipitation is complex, varying with spatial scale and synoptic forcing. Large-scale (~100–1000s km) vegetation impacts on precipitation are well documented, whereas evidence for local-scale (~1–100 km) effects remains limited. At local scales such as ecotones, surface heterogeneity can generate mesoscale circulations that, in turn, modulate rainfall. Previous studies indicate that mid-latitude vegetation asymmetrically regulates daytime and nighttime temperatures, yet the diurnal temperature gradients in many ecotones may be reshaped under widespread greening and rapid warming. Here, we investigated the combined effects of vegetation and synoptic forcing on warm-season (May–September) diurnal rainfall during 1981–2020 in the crop-forest ecotone of Liaoning Province, Northeast China, as a representative case of local scale vegetation–precipitation feedback under climate change. Using four decades of satellite and reanalysis data, we found a significant decline in midday-to-afternoon (11–17 local time) low-intensity rainfall amount (below the 50^th percentile, <0.6 mm h⁻¹), primarily driven by reduced event frequency rather than changes in intensity. No significant trends were observed in nocturnal rainfall. Synoptic classification revealed that one dominant weak-forcing pattern (T3) accounted for most of the midday and afternoon decline. Under this pattern, weak large-scale ascent, together with less effective mesoscale ascent linked to an enhanced crop–forest thermal contrast, weakened vertical motion and likely contributed to reduced rainfall. Given continued future warming and persistent vegetation greening, the mechanisms identified here may have broader relevance for understanding how vegetation modulates local precipitation under climate change.
 

Vegetation impact;,diurnal rainfall,local scale,synoptic forcing,Ecotones