Remote Sensing Allie Marquardt Collow Met Analysis – December 3, 2012
Homework #6 • Be sure to kink the isobars around fronts! • Don’t forget to complete the COMET Module on Weather Radar for next week! You may hand in your hurricane tracking charts today or next week
Types of Radiation Shortwave Radiation: Energy that is emitted by the Sun, which enters Earth’s atmosphere. Can be reflected by clouds and aerosols. Longwave Radiation: Energy that is emitted by the Earth proportional to the temperature4. Can be absorbed by greenhouse gases.
Satellites • Can be used to measure radiation in different wavelengths • Can also be used for soundings, measuring emissions in different wavelengths, and interpreting them as layer temperatures or humidity • Active Sensor – Emits radiation that is reflected by a target, such as a cloud, which is then detected by the satellite. Examples are radar and lidar. • Passive Sensor – Detects radiation that is reflected or emitted from Earth
Comparison of Different Orbits Geostationary Orbit Polar Orbit Can see the entire globe twice in one day, including the poles Will give you temporal gaps between successive data points for a location • Limited to its field of view • Gives a constant view of a location, enabling diurnal studies
Geostationary Satellites • Orbits with same period as Earth (located at the equator) • Gives you a constant view over its field of view • One geostationary satellite cannot give you information for the whole globe • Examples: GOES GERB (Meteosat-8) GOES uses an imager to give us a picture of the atmosphere using visible, shortwave, and infrared radiation. GERB uses a scanning radiometer to give us the amount of shortwave radiation reflected and longwave radiation emitted from Earth. Nasa.gov Esa.gov Also has a sounder that can give us the temperature and moisture profile, surface and cloud top properties, and ozone distribution.
The A-Train • Polar orbiting satellites that are referred to as the afternoon constellation because they pass over the equator at 1:30 pm local time, within minutes of each other • Consists of 8 satellites that contain numerous instruments including MODIS, CERES, and a cloud camera • CloudSat = a cloud radar on a satellite • CALIPSO = a lidar on a satellite Atrain.nasa.gov
A-Train, the afternoon constellation
Sun-Synchronous Satellites • http://earthobservatory.nasa.gov/Features/OrbitsCatalog/images/sun-synchronous_orbit.h264.mov • Pass over at the same local time each day Nasa.gov
GPS • http://www.nasa.gov/mov/255363main_134_GPS_Work.mov • GPS satellites give you a signal with the exact time and location of the satellite Gps.gov
GRACE • GRACE uses GPS to determine gravity by measuring how the distance between two satellites changes • When the first satellite encounters a region with stronger gravity, it starts to move faster, increasing its distance from the other satellite Csr.utexas.edu/grace
COSMIC • http://www.cosmic.ucar.edu/index.html • Stands for Constellation Observing System for Meteorology Ionosphere and Climate • Contains 6 satellites, 5 of which are operational, in a low Earth orbit that use GPS signals to get temperature and moisture profiles of the atmosphere Cosmic.ucar.edu
MODIS • MODIS stands for Moderate Resolution Imaging Spectroradiometer • Aboard Aqua (passes over the equator in the afternoon) and Terra (passes over the equator in the morning) • Views the entire Earth every 1 to 2 days • The optical system aboard MODIS contains a two-mirror off-axis afocal telescope that directs energy to four different refractive assemblies (Visible, Near IR, SW/MW IR, LW IR) • http://modis.gsfc.nasa.gov/about/media/modis_sm.mov • http://modis.gsfc.nasa.gov/gallery/
Visible Satellite • A visible satellite image shows reflected shortwave radiation at a wavelength of 0.52 to 0.75 micrometers • Only available during daytime hours • Clouds appear white, while the land and ocean appears gray or black • Can distinguish between land and ocean • Loops can show snow cover Smoke from wildfires http://synoptic.envsci.rutgers.edu/site/sat/sat.php
Infrared Satellite • An infrared satellite image shows radiation emitted from the surface and atmosphere at a wavelength of 10.2 to 11.2 micrometers • Can be used during the night, unlike the visible channel • Lighter colors (white) represent colder temperatures, such as a cloud top • Darker colors (black) represent warmer temperatures, such as the surface • Can give you land and sea surface temperatures
What are the advantages and disadvantages of the visible and infrared channels?
