Hidrologia 1 Evapotranspiração 3 Balanço de energia

Summary

This lesson explores the energy balance at Earth's surface, focusing on the interaction of solar radiation with the atmosphere and surface. It covers how energy is absorbed, reflected, and emitted in the form of longwave radiation. The script explains sensible and latent heat fluxes, how surface types like snow or forests impact albedo, and how these fluxes relate to evapotranspiration in hydrology. Additionally, daily and global energy balance averages are discussed, highlighting the role of water availability in determining the distribution of heat fluxes, ultimately maintaining Earth's energy equilibrium.

Takeaways

• 😀 The sun's energy reaches the Earth's surface after some losses due to reflection and absorption by the atmosphere.
• 😀 A portion of solar radiation is reflected by clouds and transmitted back to space as shortwave radiation.
• 😀 Absorbed solar radiation can be emitted back as longwave radiation or transferred to the ground and atmosphere as heat.
• 😀 Albedo, the reflectivity of a surface, plays a crucial role in determining how much energy is absorbed versus reflected.
• 😀 The albedo of different surfaces varies: deep water has low albedo, while snow and ice have high albedo.
• 😀 Vegetation type affects surface albedo, with forests typically having lower albedo than grasslands or pastures.
• 😀 Sensible heat flux refers to the transfer of heated air away from the surface, influenced by convection and wind speed.
• 😀 Latent heat flux involves the movement of water vapor away from the surface due to turbulence in the atmosphere.
• 😀 Energy balance at the surface includes the net radiation, heat flux to the ground, sensible heat flux, and latent heat flux.
• 😀 The latent heat flux is critical for evapotranspiration, a key process in hydrology, especially when water is readily available.
• 😀 The energy balance during the day shows that the surface absorbs much of the solar radiation, with different energy fluxes varying by time and moisture availability.

Q & A

What happens to solar radiation as it reaches the Earth's atmosphere?

When solar radiation reaches the Earth's atmosphere, part of it is reflected back into space by clouds, while some is absorbed by the atmosphere. The rest continues to the surface where it may be reflected or absorbed.

How does the albedo of different surfaces affect energy absorption?

The albedo, or reflectivity, of a surface determines how much solar radiation is reflected. For instance, snow has a high albedo, reflecting most radiation, while water and vegetation have lower albedos, absorbing more energy.

What is the role of latent heat flux in the energy balance?

Latent heat flux involves the evaporation of water from the surface, transferring energy to the atmosphere. It plays a key role in hydrological processes and represents the amount of water vapor leaving the surface, which is critical for understanding evapotranspiration.

How does the sensible heat flux differ from the latent heat flux?

Sensible heat flux involves the transfer of heat to the air near the surface, either by convection or wind. In contrast, latent heat flux involves the transfer of energy through the evaporation of water, moving moisture into the atmosphere.

What is the effect of surface vegetation on the energy balance?

Vegetation affects the energy balance by altering the surface's albedo. Forests typically have lower albedo and absorb more energy compared to pastures and grasslands, which have higher albedos and reflect more energy.

How do soil moisture levels influence the albedo?

Soil moisture levels directly impact the albedo. Wet soils have a lower albedo, meaning they absorb more energy, while dry soils have a higher albedo, reflecting more solar radiation.

Why is the heat flux to the soil often neglected in daily energy balance calculations?

The heat flux to the soil is relatively small compared to other energy fluxes like latent and sensible heat flux. As a result, it is sometimes neglected in daily energy balance calculations, especially over short time periods.

How is the energy balance maintained at the Earth's surface?

The energy balance is maintained through the interaction of solar radiation, absorbed and reflected radiation, long-wave radiation, and heat fluxes. Energy absorbed at the surface is either emitted as long-wave radiation or transferred as sensible and latent heat fluxes.

What factors influence the amount of latent heat flux in a given area?

The amount of latent heat flux depends on the availability of water and the intensity of atmospheric turbulence. Areas with more water availability, such as crops or moist environments, will experience higher latent heat flux.

What is the relationship between solar radiation and long-wave radiation in the energy balance?

Solar radiation is absorbed at the surface and is re-emitted as long-wave radiation. This long-wave radiation interacts with the atmosphere, and the net long-wave radiation flux is the difference between emitted and received long-wave radiation.