The effect of raindrop temperatures on runoff generation and erosion on clayey soil was investigated in sprinkling experiments with a laboratory rotating disk rain simulator. The experiments were applied to Rhodoxeralt (Terra Rossa) soil with two pre-prepared moisture contents: hygroscopic and field capacity. For each moisture content, three rainfall temperatures were applied: 2, 20, and 35 °C. Erosion was generally lower in the pre-wetted soil than in the dry soil (12.5 and 24.4 g m−2 per 40 mm of rain, respectively). Whereas there was no significant effect of raindrop temperature on the dry soil, the soil that was pre-moistened to field capacity was affected by rainwater temperature: runoff and erosion were high when the temperature difference between rainfall and soil surface was high, and sediment yields were 13·9, 5·2, and 18·3 g m−2 per 40 mm of rain, for rain temperature of 2, 20, and 35 °C, respectively. It is reasonable to conclude that thermophoresis caused by thermal gradients within the soil solution reduces the stability of aggregates and then increases the soil losses.
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- aggregate stability
- rain simulator
- rain temperature
- runoff and soil erosion