Polar Orbits Ht 850 Km Swath Twice in

Polar Orbits Ht ~850 Km Swath; Twice in 24 Hrs, 14 Orbits per Day; Resolution An orbit with a inclination of 90 degrees, or close to it, is called a "polar orbit. " Because the Earth is rotating as the satellite follows a polar orbit, the satellite can survey the whole of the Earth's surface, including the poles, in a few days. Many observation satellites that need to cover the entire Earth are in polar or near-polar orbits.

Sun-synchronous orbit: the satellite's orbital plane and the Sun's direction are always the same

Geostationary Orbit A satellite that appears to remain in the same position above the Earth is called a "geostationary satellite. " Revolves with same angular velocity of earth Spatial Resol. –Less; polar regions not covered.

A satellite in a geosynchronous orbit goes around the Earth once a day returning to its original position

Resolution (Geostationary satellite)

Types of Meteorological Satellite Sensors Sounders Microwave Imagers/Scanners Visible/Infrared 10^3 to 10^6 Micron 0. 4 -0. 7 Micron, 1 -100 Micron Passive Active (Radiometers/ Spectrometers) Radar LIDAR

Visible/Infrared Imaging and Sounding

Solar and Terrestrial Radiances Absorption Lines

Sensors

GMS 5 and METEOSAT sensors GMS 5

Satellite imagery • VIS - imagery derived from reflected sunlight at visible • IR - imagery derived from emissions by the Earth and its atmosphere at thermal-infrared wavelengths • WV - imagery derived from water vapor emissions • 3. 7μm - (channel 3) imagery from this specific wavelengths, which is in the overlap region between solar and terrestrial radiation

IMAGERY INSAT-3 A GMS 5 • • VIS IR WV CCD (VIS, NIR, SWIR) (split window) VIS IR WV IR 1 -IR 2 (split window) METEOSAT • • VIS IR WV 3. 7μm • 3. 7μm-IR 1 (split window)

NOAA-AVHRR • Polar orbiting Satellite • Resolution : 1. 1 km (Nadir), 6 km Off Nadir) • Channels : Application – 0. 55 -0. 68 – 0. 75 -1. 1 – 3. 55 -3. 93 – 10. 3 -11. 3 – 11. 5 -12. 5 Cloud Mapping Surface Water boundaries Thermal Mapping, Cloud distribution Fire detection Cloud distribution, SST, WV -do-

VIS image 05 UTC 17 Nov 1999 NOAA • Available only during daytime • Intensities vary depending upon locations among the earth, the sun and the satellite. • Reflection intensities differ depending upon cloud thickness. • Lower clouds can be seen well.

TYPICAL ALBEDO VALUES • • • OCEAN / LAKES LAND SURFACE ICE SNOW CU CLOUD CI CLOUD (THICK) ST CLOUD AC , AS & SC CLOUDS TCU CLOUD CB CLOUD 8 % 14 - 27 % 35 % 80 % 35 % 50 - 60 % 68 % 75 % 90 %

CHARACTERISTIC FEATURES X BRIGHTNESS ( WHITE, GREY ) X PATTERN ( LINE, BANDS, WAVES) X STRUCTURE ( SHADOW, HIGHLIGHT ) X TEXTURE ( SMOOTHNESS ) X SHAPE ( ROUND, STRAIGHT ) X SIZE (Patterns, useful indicators of Weather System

IR image • Always available • Shades of levels differ depending upon cloud heights (IR 1, IR 2). • Upper clouds can be seen well. 05 UTC 17 Nov 1999 NOAA

WV image • Always available • Shades of levels differ depending upon humidity in upper to midlevel (WV). • Upper clouds can be seen well. • Levels may vary depending upon absorption by clouds and atmosphere on the way. 05 UTC 17 Nov 1999 GMS

Comparison Meteosat data IR and WV 19. 01. 2001

Meteosat 7

Meteosat 5

GMS 5 1200 UTC 22 Oct 2000

Representation Imagery White Gray Black VIS High Albedo Low IR Low Temperature High WV Wet Humidity Dry 3. 7 m Day time Low Albedo High 3. 7 m Night time Low Temperature High

CLOUD MATRIX I N F R A R E D DEEP CONV WHITE (COLD) THIN CIRRUS DARK (WARM) NO CLOUDS CB / TCU LOW CLOUDS DARK WHITE VISIBLE

GREY SCALE MATRIX I N F R A R E D WARM SEA BLACK DARK GREY ST FAIR WX CU GREY ST, SC AC, AS THIN CI THICK CB, TCU CB WHITE CI AS ANVIL WHITE GREY DARK BLACK GREY VISIBLE

IR 1 -IR 2 • thin Ci • low cloud • volcanic ash, 05 UTC 17 Nov 1999 NOAA

Split Window Channel (IR 1 -IR 2)

3. 7μm image Day time (reflected sunlight) • snow • sea ice • Ci Night time (emmited radiation) • low cloud 05 UTC 17 Nov 1999 NOAA

3. 7μm-IR 1 • Usage in night time • thin Ci • low cloud (Fog) 18 UTC 9 Aug 1999 NOAA

. 0 Some of the GOES Imagery Applications: Channel Name Central Wavelength Resolution km E/W x N/S 1 visible 0. 65 µm 0. 57 x 1. 00 Produces high resolution black and white photographs of earth and clouds. 2. 30 x 4. 00 At night, can be used to track low-level cloud fields and thus infer near-surface wind circulation. 2 shortwave infrared 3. 90 µm Example Meteorological Applications 3 water vapor channel 6. 70 µm 2. 30 x 8. 00 1. Detects mid- and upper-level water vapor and clouds. 2. Locates and defines synoptic features such as shortwave troughs, ridges, jet streams, etc. via mesoscale regions of moistening/drying at the 300 -500 mb height. 3. Can derive upper-level wind vectors (wind barbs) with the winds plotted on the image valid at the time of the winds. 4 window channel 10. 70 µm 2. 30 x 4. 00 Cloud top temperatures, nighttime tracking of storm systems. 5 dirty window/ split window IR 12. 00 µm 2. 30 x 4. 00 Sensitive to low level water vapor.

Goes Imager Applications: Channel 2, Short-wave Infrared Channel (3. 9 µm) • Emissivity of water droplets at 3. 9 µm is less than that for longer wavelengths, • Easier to identify fog and Stratiform cloudiness • Discriminate between water and ice clouds. • The 3. 9 µm channel is different - emitted terrestrial radiation, and reflected solar radiation. • Fog, and cold ground. Combining this imagery with other channels resolves most of these problems. Using Channel 2 (3. 9 µm) Imagery at Night. • 3. 9 µm imagery at night offers a good substitution for visible channel imagery • . It can be used to track low-level cloud fields and thus infer near-surface wind circulation. • useful in the tropics, where freezing levels are relatively high (~5 km) and conventional low-level wind data are sparse. Channel 3, Water Vapor Channel (6. 7 µm) • The 6. 7 µm channel responds to mid- and upper-level water vapor and clouds. • large regions of upward (or downward) motion and consequent moistening (or drying), the water vapor data • used to locate short wave troughs, ridges, jet streams, etc. • Meso-scale regions of moistening/drying at the 300 -500 mb height (such as subsidence associated with thunderstorms' anvils) have also recently come under close scrutiny using this channel's imagery Using Channel 3 (water vapor) Imagery to Derive Winds