Remote Sensing

Allie Marquardt Collow

Met Analysis – December 3, 2012

Met Analysis Fall 2012

Remote Sensing

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

Met Analysis Fall 2012

Remote Sensing

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.

Met Analysis Fall 2012

Remote Sensing

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

Met Analysis Fall 2012

Remote Sensing

Comparison of Different Orbits

Geostationary Orbit• Limited to its field of view• Gives a constant view of

a location, enabling diurnal studies

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

Met Analysis Fall 2012

Remote Sensing

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)

Nasa.govEsa.gov

Also has a sounder that can give us the temperature and moisture profile, surface and cloud top properties, and ozone distribution.

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.

Met Analysis Fall 2012

Remote Sensing

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

Met Analysis Fall 2012

Remote Sensing

A-Train, the afternoon constellation

Met Analysis Fall 2012

Remote Sensing

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

Met Analysis Fall 2012

Remote Sensing

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

Met Analysis Fall 2012

Remote Sensing

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

Met Analysis Fall 2012

Remote Sensing

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

Met Analysis Fall 2012

Remote Sensing

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/

Met Analysis Fall 2012

Remote Sensing

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 wildfireshttp://synoptic.envsci.rutgers.edu/site/sat/sat.php

Met Analysis Fall 2012

Remote Sensing

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

Met Analysis Fall 2012

Remote Sensing

What are the advantages and disadvantages of the visible

and infrared channels?