Journal Highlights

Wet Soils Elevate Nighttime Temperatures

Editors' Highlight—

Soil moisture can elevate overnight temperatures, offsetting daytime cooling, especially over areas of strong land-atmosphere interactions.

Using a conceptual model of the surface energy budget, Cheruy et al. [2017] demonstrate a noteworthy negative nocturnal feedback between soil moisture and temperature that is particularly strong in so-called “hot-spot” regions of land-atmosphere coupling. The negative feedback operates through the effect of water on the thermal inertia of the soil: dry soils can fluctuate in temperature much more readily than wet soils. Monsoon regions and transition zones between arid and humid climates have large day-to-day variability of the thermal inertia, which mainly affects variability of nighttime minimum temperatures. Here, positive soil-moisture anomalies induce cooler daytime temperatures through increased evaporative cooling, a well-known phenomenon. However, at night the higher heat capacity and thermal inertia of the wetter soil strongly prevents nocturnal cooling. The opposite situation arises for anomalously dry soils: increased daytime maximum temperatures but lower nighttime minimum temperatures....more

-- Paul A. Dirmeyer, Editor, JAMES,