Satellite measuring net radiation over a Brazilian river basin

Decoding the Weather: How Satellites Help Us Understand Net Radiation

Reese Marlowe in Climate & Environment June 2025 • 4 min read.

"Explore how MODIS satellite data transforms our understanding of regional climates in Brazil and beyond."

Net radiation (Rn) is fundamental in the processes of our environment, acting as the primary energy source for everything from physical changes to plant metabolism. It influences air and soil temperatures, dictates water transfer from ground to atmosphere, and drives photosynthesis. However, gathering accurate net radiation data can be challenging, especially in areas lacking traditional weather stations.

Remote sensing technologies offer a robust solution, providing extensive data coverage across vast regions. Satellites equipped with advanced sensors can fill data gaps, enabling scientists to estimate net radiation in previously unmonitored areas. This is particularly beneficial in regions where setting up conventional weather stations is impractical or cost-prohibitive.

A recent study focused on two sub-basins in the Paracatu region of Brazil, utilizing data from the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Terra satellite. This research sought to determine net radiation levels using the Surface Energy Balance Algorithm for Land (SEBAL), offering insights into local climate dynamics and demonstrating the capabilities of satellite-derived data.

How Satellites Measure Net Radiation

Satellite measuring net radiation over a Brazilian river basin

Satellites measure net radiation by assessing various components of the Earth's energy balance. This involves quantifying incoming solar radiation, reflected solar radiation, emitted longwave radiation from the Earth, and incoming longwave radiation from the atmosphere. Sensors like MODIS collect data across different spectral bands, which are then processed using algorithms like SEBAL to derive net radiation values.

The SEBAL algorithm calculates net radiation as the residual of the energy balance equation. It accounts for factors such as surface albedo (reflectivity), land surface temperature, and atmospheric conditions to estimate how much energy is available at the Earth's surface. This information is crucial for understanding regional climate patterns and environmental processes.

Surface Albedo: Measures the reflectivity of the surface, indicating how much solar radiation is reflected back into the atmosphere.
Land Surface Temperature: Determines the amount of longwave radiation emitted from the Earth's surface.
Atmospheric Conditions: Accounts for the absorption and scattering of radiation by atmospheric gases and aerosols.

In the Paracatu study, MODIS data were used to estimate these parameters over the Entre Ribeiros creek and Preto River sub-basins. The results provided a detailed spatial and temporal understanding of net radiation dynamics, highlighting the influence of land cover and seasonal changes. This approach not only filled data gaps but also offered a cost-effective method for continuous environmental monitoring.

The Future of Climate Monitoring

The research in the Paracatu region demonstrates the vast potential of using satellite data to understand and monitor net radiation, particularly in areas where traditional weather stations are scarce. By using data from sensors like MODIS and sophisticated algorithms like SEBAL, scientists can achieve high-resolution climate monitoring. This enhances agricultural planning, environmental management, and climate change mitigation efforts.

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Everything You Need To Know

What is net radiation (Rn) and why is it important?

Net radiation (Rn) represents the primary energy source for environmental processes. It influences air and soil temperatures, water transfer from the ground to the atmosphere, and drives photosynthesis. It's a critical component in understanding climate patterns, impacting everything from plant metabolism to regional weather conditions. Without accurate Rn data, understanding and predicting climate dynamics becomes significantly more challenging, making it essential for environmental management and climate change mitigation.

How do satellites measure net radiation?

Satellites measure net radiation by assessing the Earth's energy balance. This involves quantifying incoming solar radiation, reflected solar radiation, emitted longwave radiation, and incoming longwave radiation from the atmosphere. Instruments such as MODIS collect data across different spectral bands. This data is processed using algorithms like SEBAL to derive net radiation values. SEBAL calculates net radiation by accounting for factors such as surface albedo, land surface temperature, and atmospheric conditions to estimate the energy available at the Earth's surface.

What is the role of MODIS in measuring net radiation?

MODIS, aboard the Terra satellite, plays a crucial role in measuring net radiation by collecting data across various spectral bands. This data is used to estimate key parameters, including surface albedo, land surface temperature, and atmospheric conditions. The data collected by MODIS are processed using algorithms like SEBAL to calculate net radiation, providing detailed insights into spatial and temporal dynamics. In the Paracatu study, MODIS data enabled a comprehensive understanding of net radiation levels in two sub-basins, filling data gaps and offering a cost-effective way for continuous environmental monitoring.

How does the SEBAL algorithm work in determining net radiation?

The Surface Energy Balance Algorithm for Land (SEBAL) calculates net radiation as the residual of the energy balance equation. It considers multiple factors: surface albedo, which measures the reflectivity of the surface; land surface temperature, which determines emitted longwave radiation; and atmospheric conditions, accounting for radiation absorption and scattering. By integrating these parameters, SEBAL provides an estimate of the energy available at the Earth's surface, crucial for understanding regional climate patterns. This approach, applied in studies like the one in the Paracatu region, demonstrates the capabilities of satellite-derived data in providing high-resolution climate monitoring.

How can the use of satellite data enhance climate knowledge and benefit environmental efforts?

Using satellite data, especially from instruments like MODIS combined with algorithms like SEBAL, significantly enhances climate knowledge by filling data gaps, particularly in areas lacking traditional weather stations. This approach allows for high-resolution climate monitoring, improving our understanding of regional climate dynamics. In the Paracatu region of Brazil, this technology provided detailed insights into net radiation levels, benefiting agricultural planning, environmental management, and climate change mitigation efforts. This innovative use of technology offers a cost-effective and comprehensive method for continuous environmental monitoring, aiding in better resource management and climate change adaptation strategies.