Scatterometer

Dohlednostmereni

Scattometer principle

Soulik 2013 July 10 Scatterometer Ascending Pass

Illustration of ISS-RapidScat on ISS (20160909)

Scatterometer is a specialized radar or microwave instrument used to measure the reflection or scattering effect produced by the surface it is aimed at. The primary use of scatterometers is in meteorology and oceanography, particularly for measuring surface wind speeds and directions over the oceans. These measurements are crucial for understanding and predicting weather patterns, including the tracking and forecasting of storms and hurricanes.

Principles of Operation

A scatterometer operates by emitting a pulse of microwave energy towards the Earth's surface and then receiving the energy that is scattered back to the instrument. The amount and characteristics of the returned signal depend on the properties of the surface, such as roughness, moisture content, and others. Over the ocean, the surface roughness is influenced by the wind, which generates waves. By analyzing the characteristics of the backscattered signal, scientists can infer the speed and direction of the surface wind.

Types of Scatterometers

There are several types of scatterometers, each designed for specific applications. The most common types include:

- Real Aperture Scatterometers: These are the simplest form of scatterometers, using a fixed antenna to measure the backscatter from a single direction. - Synthetic Aperture Scatterometers: Utilizing the movement of the satellite or platform, these scatterometers create a larger "synthetic" aperture, allowing for higher resolution measurements. - Dual-Polarization Scatterometers: These instruments can transmit and receive pulses in both horizontal and vertical polarizations, providing additional information about the surface characteristics.

Applications

The primary application of scatterometers is in the field of meteorology and oceanography, where they are used to measure surface wind speeds and directions over the oceans. This information is vital for weather forecasting, climate research, and the study of ocean dynamics. Scatterometers also have applications in other fields, such as agriculture for soil moisture measurement, and in glaciology for monitoring ice and snow cover.

Satellite Scatterometers

Several satellites have been equipped with scatterometers to provide global coverage of wind measurements over the oceans. Notable examples include:

- European Remote-Sensing Satellite (ERS): Carried a scatterometer that provided valuable wind data until its mission ended. - Advanced Scatterometer (ASCAT): Onboard the Meteosat Second Generation satellites, ASCAT continues to provide wind data for weather forecasting. - QuikSCAT: Launched by NASA, QuikSCAT carried the SeaWinds scatterometer, which significantly improved the accuracy of ocean wind measurements until its mission ended.

Challenges and Limitations

While scatterometers are powerful tools for measuring surface winds, they have limitations. The accuracy of wind measurements can be affected by heavy rain, and the spatial resolution of the data may not be sufficient for certain applications. Additionally, scatterometers can only measure wind speed and direction at the ocean surface and are not effective over land for wind measurement due to the complex backscatter signals from the varied terrain.

Future Directions

Advancements in scatterometer technology and data processing techniques continue to improve the accuracy and resolution of wind measurements. Future missions may include more advanced scatterometers with higher resolution and dual-polarization capabilities, enhancing our understanding of atmospheric and oceanic processes.

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