During the summer nighttime, the warming effect shows an increasing trend of 0.040 K/decade ( p = 0.01), but the magnitude is only about one-fifth of the daytime ΔLST s negative trend (−0.188 K/decade, p = 0.01) (Fig. 1c ).
This decrease in the daily mean ΔLST w is dominated by a negative trend of the daytime ΔLST w (−0.142 K/decade, p = 0.04), while the nighttime ΔLST w demonstrates only interannual variability with a negligible temporal trend (0.002 K/decade, p = 0.97) (Fig. 1a ).
However, Δα w shows a positive trend (0.018 unitless/decade, p = 0.04) (Fig. 2a ), indicating that the albedo contrast between forests and openlands has been diminishing.
In the context of global warming, the snow cover in winter or spring is projected to maintain a decreasing trend, which may significantly reduce the biophysical radiative forcings of forests.