First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment

Soil temperature sensors are in situ ground-based sensors used to measure and monitor soil temperature. They measure soil temperature by using thermistors or thermocouples to detect changes in resistance to calculate the temperature. Soil temperature sensors are used for agricultural purposes, environmental monitoring, and ecological research.

Sunphotometers are passive optical sensors that measure the amount of sunlight. They are pointed directly at the sun to measure direct sunlight and not sunlight scatter from aerosols. These measurements can be used to determine the aerosol optical depth by following Beer’s Law. Sunphotometers have been deployed on aircraft, research vessels, and field sites for aerosol research and monitoring.

The Sound Detection and Ranging (SODAR) is an active ground-based acoustic sensor that measures atmospheric winds and turbulence. It sends acoustic energy into the atmosphere and detects the strength and frequency of the backscattered energy. The backscattered signal can be used to determine the horizontal wind field, assuming the scattered energy moves with the mean wind. SODARs are frequently used in boundary layer studies to measure turbulence and wind profiles.

The Volume Imaging Lidar (VIL) is a ground-based lidar system operated by the University of Wisconsin. It is an elastic backscatter lidar that operates at the 1064 nm wavelength. It provides aerosol backscatter profiles with a range resolution of 7.5 m or 15 m. VIL has a maximum range of 18 km and a repetition rate of 30 Hz. The Naval Research Laboratory (NRL) also operates its own VIL with similar specifications.

Generic-Atmospheric State (Gen-AtmsState) refers to non-specific instruments on a platform used for measurements of atmospheric state parameters. These are typically in situ sensors that measure temperature, pressure, humidity, and wind speed/direction. Types of atmospheric state instruments include thermometers, hygrometers, barometers, and anemometers.

Generic-Radiometers refer to non-specific radiometers on a platform. These are typically passive microwave radiometers that measure brightness temperature. Radiometers can be used to retrieve temperature and water vapor profiles, soil moisture content, ocean salinity, precipitation and cloud properties, and vegetation.

The LI-COR Plant Canopy Analyzer is an in situ analyzer manufactured by LI-COR for leaf area index (LAI) measurements. It measures diffuse sky radiation that passes through the canopy across five zenith angels to determine LAI and other canopy characteristics. It can be used for most sky conditions and canopy types, such as row crops, grasslands, isolated trees, and forests. The optical sensor within the Plant Canopy Analyzer has a wavelength range of 320-490 nm. It has a field of view of 148 degrees and an operating temperature range of -20 to 50 degrees Celsius.

Digital cameras are used to provide imagery for research applications. Cameras are used on aircraft to collect aerial imagery for mapping and surveying, environmental monitoring, cloud observations, agriculture, geological studies, and other Earth science applications. They are also used at field sites to capture visual observations to monitor changes in land cover, vegetation, clouds, air quality, glaciers, and other phenomena.

The LI-COR Quantum Sensor is a ground-based, in situ radiation sensor manufactured by LI-COR. It collects precise photosynthetically active radiation (PAR) measurements beneath vegetation or under artificial light sources. The sensor detects radiation within the same light spectrum (400 - 700 nm) that plants use for photosynthesis. While primarily used for ground-based measurements, the LI-COR Quantum Sensor can also be mounted on aircraft. It is suitable for long-term deployments and remains durable in high temperatures and humidity conditions.

The Spectron Engineering-590 (SE-590) Spectroradiometer is a portable spectroradiometer manufactured by Spectron Engineering. It can be used on both airborne and ground-based platforms. SE-590 uses a charge-coupled device (CCD) area array detector to measure reflectance. It operates across the visible to short-wave infrared spectral range (350-2500 nm). The SE-590 has a ground resolution of 4.5 meters when flown at an altitude of 300 meters.

The Lyman-alpha Hygrometer is an in situ hygrometer designed for deployment on airborne or ground-based platforms. It measures water vapor absorption at the Lyman-alpha wavelength (121.6 nm) of atomic hydrogen to determine the total water content in the atmosphere. It has a detection limit of 0.1 ppmv and a typical data acquisition rate of 1 second. The Lyman-alpha hygrometer provides water vapor measurements with an accuracy of 6% and a precision of 5%.

This data will be added in future versions

Stream gauges are ground-based sensors that measure the water level or stage of rivers and streams at specific locations. The flow or discharge of a river can then be calculated from these stage measurements. These gauges can provide continuous data, making them useful for monitoring flood risk and water supply. The United States Geological Survey (USGS) operates a network of over 10,000 stream gauges across the United States to assist with flood prediction and water resource management.

Soil moisture probes are in situ ground-based sensors that measure soil water content. The most common type of soil moisture probes used for scientific research use dielectric permittivity techniques, such as capacitance or time-domain reflectometry sensors. These types of probes measure the charge-storage capacity of the soil to determine the soil moisture content. They typically operate at frequencies around 50 MHz and above to reduce sensitivity to salinity. Soil moisture probes provide continuous measurements and are relatively easy to deploy.

Rain gauges are ground-based instruments that measure liquid precipitation amounts directly over a specified period. Different rain gauges, such as tipping buckets and weighing gauges, collect and record data in various ways. Because of their small size and easy setup, rain gauges can be placed in different locations and are often used alongside other precipitation instruments like disdrometers to gather more details, such as precipitation rate and size distribution.

The Modular Multiband Radiometer (MMR) is an airborne multispectral radiometer manufactured by Barnes Engineering Company. MMR measures radiance across 8 spectral bands in the infrared and visible wavelengths (0.4-12.5 μm) to produce images of vegetation and other surface features. At an altitude of 300 meters, the MMR has an instantaneous field of view (IFOV) of about 79 meters and a 15-degree field of view (FOV). It is typically deployed on small aircraft like helicopters but can also be used on ground-based platforms.

The NOAA/WPL Pulsed Coherent Doppler Lidar is a ground-based lidar system developed by the NOAA Wave Propagation Laboratory (WPL). It measures radial velocity as a function of range using light-scattering particles in the air as tracers to derive wind profiles and momentum fluxes. It operates at a wavelength of 10.59 μm and has a pulse repetition rate from 1 to 20 Hz. It provides velocity azimuth display (VAD) scans, range height indication (RHI), and volume or roster scans at a range resolution of 150 meters.

The Portable Apparatus for Rapid Acquisition of Bidirectional Observations of the Land and Atmosphere (PARABOLA) is a passive ground-based sphere scanning radiometer. It measures surface reflectance across eight spectral channels. The first four channels (444, 551, 650, and 860 nm) coincide with spectral bands from the Multi-angle Imaging SpectroRadiometer (MISR) on the Terra satellite for validation purposes. The last four channels are used for the characterization of water vapor (944 nm), aerosol optical depth at longer wavelengths (1028 and 1650 nm), and measurements of photosynthetically active radiation (400-700 nm). The measurements from PARABOLA can be used to derive the surface bidirectional reflectance factor and sky and surface radiances. A complete scan of both sky and ground hemispheres takes approximately 3 minutes.