Remote sensing (weather and climate)

Polar orbiting

Orbit over the poles, low-altitude orbit (850)km, higher resolution.

Geostationary

Orbit over a fixed location on Earth’s surface, high-altitude orbit (35,000)km,

Satelittes

Defined by the wavelengths that they detect

Most meterological applications of satellite images rely on:

Visible images, infrared images, and water vapor images.

Satellites are operated by:

National Oceanic and Atmospheric Administration (NOAA)

Visible light

Objects with higher albedo appear brightest

Infrared

Colder objects appear brighter

Water vapor

areas with higher moisture content appear brighter

Visible images detect:

Visible sunlight reflected off the Earth.

Bright features of visible images include:

Clouds, snow/ice cover, ground with high albedo

Visible image advantages:

Images appear like what they look like on Earth and in the clouds

Visible image disadvantages:

No nighttime detection, sometimes difficult to determine cloud altitude, snow/ice on te surface can look like clouds.

Infrared images detect:

Infrared radiation emitted by the Earth. Warm surfaces appear dark, cold surfaces appear light

Infrared image advantages:

cloud height, ground temp images available night and day.

Infrared image disadvantages:

Difficult to determine low clouds from cold ground, lower resolution than visible images.

Water vapor images detect:

Infrared radiation emitted by the water vapor, humid air appears white, dry air appears dark.

Water vapor image advantages:

Water vapor acts as a tracer for air motion.

Water vapor image disadvantages:

Detects mid/upper-tropospheric water vapor only, not seen at lower levels

Radar

Radio detection and ranging

Radar transmits:

Microwave radiation

Radar works by:

Sending short pulses of radar waves that are reflected off objects in the atmosphere such as raindrops and ice crystals

Power that is returned to radar is dependent on:

Size of the target, composition of the target and number of targets

Radar can differentiate between

Types of precipitation and determine the location and movement of these objects

Radar is used in

Short term forecasting

Radar reflectivity measures:

The power returned to the radar. Higher return = heavier precipitation

Doppler radar

Can also detect wind speed and direction

Radar velocity

Can only detect radial velocities, toward or away from the radar.

Limitations of radar

1. Limited range- curvature of the Earth

2. Beam spreading with range