Microwave Remote Sensing Basics

A technique using microwaves to sense the Earth's surface and atmosphere.

Sensors that emit microwaves and measure the reflected energy.

Sensors that detect naturally emitted microwaves from the environment.

Specific wavelengths of radiation used for different sensing applications.

A type of active microwave sensing.

The level of detail in a microwave image.

The direction of the electric field in the electromagnetic wave.

Collecting images of the environment using microwaves.

The orientation of the electric field in microwave radiation.

Radars transmit and receive horizontally (H) or vertically (V) polarized microwave radiation.

Advantages include penetration through clouds and large field of view compared to other sensors.

Passive microwave sensors generally have lower spatial resolution due to the low energy compared to optical wavelengths and variable emissivity.

A technique that uses the platform's forward motion to simulate a very long antenna, resulting in high azimuth resolution.

Adjusting the radar beam width and illumination time compensates for varying distances, ensuring consistent resolution across the entire swath.

Measuring the ocean's surface height to understand its topography, circulation, and variability.

The time it takes for a microwave pulse to travel from the satellite to the ocean surface and back.

Changes in ocean volume, seasonal heating/cooling, tides.

Passive microwave sensors measure various Earth surface properties, including soil moisture, snow water equivalent, sea/lake ice characteristics, sea surface temperature, atmospheric water vapor (over oceans), surface wind speed, and cloud liquid water.

The temperature calculated from emitted radiation; often lower than the true, kinetic temperature (Tkin).

The true temperature of an object, measurable with a contact thermometer.

A measure of how well an object radiates relative to a perfect blackbody.

An approximation that describes the spectral radiance of blackbody radiation at longer wavelengths.

The power emitted per unit emitting area per steradian per unit wavelength.

Satellites used for remote sensing, providing high stability, global coverage, and discontinuous temporal coverage over low latitudes.

A technology that uses quantum physics to measure land surface temperatures and calculate "spectral radiance" at specific wavelengths.

The temperature of the ocean's surface, typically measured using satellite remote sensing.

A technique that measures naturally emitted microwave radiation from the Earth's surface, like the ocean.

SST images provide valuable information for fisheries management, climate monitoring, validating atmospheric models, evaluating coral bleaching, studying ocean heat storage and currents, and understanding temperature-sensitive biological activity.

Satellite instruments used for SST measurement include the Advanced Very High Resolution Radiometer (AVHRR), Moderate Resolution Imaging Spectroradiometer (MODIS), and Visible Infrared Imaging Radiometer Suite (VIIRS).

Adjusting SST data to account for the absorption of infrared radiation by water vapor in the atmosphere.

Two bands are used to correct for water vapor absorption: one band is more sensitive to WV than the other. The difference in radiance between these bands provides a measure of WV, which is then used to correct the SST.

Specific infrared wavelengths used by AVHRR and MODIS to measure the thermal radiation emitted by the ocean's surface.

Adjusting infrared measurements for the effects of the atmosphere, such as water vapor and scattering.

MCSST stands for Multi-channel Sea Surface Temperature. It is a technique used to derive sea surface temperature (SST) from satellite data. It involves combining measurements from multiple infrared channels to compensate for atmospheric effects.

MCSST uses a specific mathematical equation incorporating measurements from multiple infrared channels, including the brightness temperature in those channels. This equation accounts for atmospheric effects and other factors that can influence the temperature reading, resulting in a more accurate SST measurement.

Scatterometers are satellite sensors used to measure wind speed and direction over water. They have various applications, including weather forecasting, marine safety, fishing, and long-term climate studies.

Scatterometers are unique among satellite remote sensors as they are the only ones capable of determining wind velocity and direction over water.

Scatterometers emit pulses of microwave radiation towards the ocean surface. The backscattered signal is then measured and used to determine the wind speed and direction.

The 'scan characteristics' refer to how a Scatterometer collects data. It can use a conical scan or a double swath scan, impacting the coverage and resolution of the data.

The background period of service' refers to the timeframe during which a specific Scatterometer was operational, providing data about the wind conditions.

Scatterometers operate at different frequencies, either C-band or Ku-band, which impacts their data quality and applications. C-band is better for stronger winds while Ku-band is better for calmer conditions.