A topic in the Open Knowledge Graph — a free, open map of 15,290 topics and the order to learn them in.
The surface energy budget partitions incoming solar radiation into reflected shortwave radiation, latent heat flux, sensible heat flux, and ground heat storage. This balance varies regionally and temporally, determining surface temperature and driving local climate. Changes in surface properties or atmospheric composition alter the balance, making this a critical link between atmospheric forcing and climate response.
From your work on energy balance models, you know that the Earth system must balance incoming solar energy against outgoing energy to maintain a stable temperature. The surface energy balance zooms in on exactly what happens to that energy once it reaches the ground. Think of the surface as an accountant: every watt of energy arriving must be accounted for — reflected, radiated back, used to evaporate water, conducted into the ground, or used to warm the air above. The balance sheet at any location and time determines the local surface temperature.
The incoming side is dominated by net radiation — the difference between absorbed solar (shortwave) radiation and emitted terrestrial (longwave) radiation. A fresh snow surface might reflect 80-90% of incoming sunlight, leaving little energy to warm anything, while a dark ocean surface absorbs over 90%. This is why albedo matters so much. The net radiation that remains after reflection and longwave emission is called the available energy, and it must be partitioned among three main outgoing terms: sensible heat flux, latent heat flux, and ground heat flux.
Sensible heat flux is the direct warming of the air above the surface through conduction and convection — you can feel this as the shimmer of hot air rising from sun-baked pavement. Latent heat flux is energy consumed by evaporation or transpiration from plants; the energy is not lost but stored in water vapor and released later when the vapor condenses (this is why humid tropical forests stay cooler than dry deserts at the same latitude, even with similar solar input). Ground heat flux is energy conducted downward into the soil or rock, warming the subsurface. The ratio between sensible and latent heat flux is captured by the Bowen ratio — a desert might have a Bowen ratio above 5 (almost all sensible heat), while a well-watered cropland might be below 0.5 (latent heat dominates).
This partitioning has profound consequences for climate. Deforestation replaces transpiring trees with bare soil, shifting energy from latent to sensible heat flux — the surface warms, the boundary layer dries, and local rainfall patterns can change. Urbanization replaces vegetated surfaces with concrete and asphalt, dramatically increasing sensible heat flux and creating urban heat islands. Changes in atmospheric greenhouse gas concentrations alter the longwave radiation terms, increasing the net radiation available at the surface. Understanding these feedbacks — how surface changes propagate through the energy budget into temperature and circulation changes — is why the surface energy balance sits at the heart of climate science, connecting radiative forcing to the climate response you will study next.