Satellite Imagery

Geostationary Satellites (GOES) Geostationary satellites orbit high (approximately 36,000 km) above the equator and orbit around the Earth at the same rate as the Earth rotates on its axis. Above Equator moving eastwardAbove Equator moving eastward approx 7000 mph approx 7000 mph Thus, geostationary satellites appear to remain above the same location on the Earth at all times.

Geostationary Satellites (Cont.) Advantage: always located above the same region of the Earth, providing continuous images of that region. Disadvantage: The great distance from the surface of the Earth limits the resolution of the images (i.e. it is harder to see smaller weather features).

Low Earth Orbiting (POES) Polar orbiting satellites orbit at a lower distance (around 850 km) above the Earth’s surface and the orbit takes the satellite near the north and south poles. These satellites are generally in a sun- synchronous orbit in which they cross the equator at the same time on each orbital pass. Full rotation 1.5 hrs Full rotation 1.5 hrs Pass single location 2x daily Pass single location 2x daily

Low Earth Orbiting (Cont.) Advantage: the low orbit allows for the generation of higher resolution imagery. Disadvantage: polar orbit results in gaps in coverage and many places are often observed twice a day or less.

Other Low Orbiters Moderate Resolution Imaging Spectrometer (MODIS) Terra: Passes Equator in morning Terra: Passes Equator in morning Aqua: Passes Equator in evening Aqua: Passes Equator in evening Sample images Sample images Sample images Sample images Advantage:.25 km resolution Advantage:.25 km resolution Disadvantage: Long time to receive Disadvantage: Long time to receive

Active versus Passive Sensors A passive sensor is an instrument that measures the incoming amount of energy in the form of electromagnetic radiation in a band of wavelengths. More info More infoMore info An active sensor is an instrument that transmits electromagnetic radiation in a given wavelength and measures the amount of energy reflected/backscattered to the sensor.

Active vs. Passive Sensors (Cont.) A passive sensor weighs less but it is dependent on the energy naturally occurring in the environment. An active sensor is heavier, but it is able to transmit energy at a specific wavelength. This enables the sensor to be designed for specific purposes (e.g. to sense surface characteristics through clouds and rain.).

Geostationary Operational Environmental Satellites Geostationary Operational Environmental Satellites GOES-E (GOES-13) – longitude 75°W GOES-14 backup - longitude (105°W) GOES-W (GOES-15) – longitude 135°W Meteosat-10Meteosat-10 – longitude 0° Meteosat-10 Meteosat-7Meteosat-7 – longitude 57°E Meteosat-7 MTSAT-2 – longitude 140°E

Operational Geostationary Satellites (Cont.) GOES-E and GOES-W are operated by NOAA Meteosats are operated by EUMETSAT MTSAT-2 is operated by the Japanese Meteorological Agency

GOES East

GOES West

Meteosat 7

Meteosat 10

MTSAT-2

Geostationary Operational Environmental Satellite (GOES) GOES contain two main instrument systems. 1. The GOES imager. imager 2. The GOES sounder. sounder

The GOES Imager The GOES imager is a multichannel instrument that senses radiant energy emitted in the terrestrial (longwave) and reflected in the solar (shortwave) wavelengths.

GOES Imager Bands Visible ( µm) is useful for cloud and severe storm identification. Shortwave infrared ( µm) is useful for discriminating between snow and low clouds.

GOES Imager Bands (Cont.) Upper level water vapor ( µm) is useful for estimating the water vapor content of the upper troposphere. Longwave infrared 1 ( µm) is useful for identification of clouds and severe storms.

GOES Imager Bands (Cont.) Longwave infrared 2 ( µm) is useful for determination of sea surface temperatures.

Types of GOES Images 1. Visible images 2. Infrared images 3. Water vapor images

Visible Satellite Imagery Visible satellite imagery is constructed from the solar radiation reflected by an object to the sensor on the satellite. Objects that reflects a lot of visible light (i.e. have a high albedo) appear bright. These objects include fresh snow on the ground and thick clouds like cumuli and cumulonimbi. Some low level defense satellites carry low light sensors Some low level defense satellites carry low light sensors

Snow Cumuliform Cloud High Albedo Bare soil (low albedo) High Albedo

Visible Imagery GOES 1 km resolution in N America GOES 1 km resolution in N America Polar Orbiters 1 km resolution Polar Orbiters 1 km resolution Terra/Aqua 0.25 km resolution Terra/Aqua 0.25 km resolution Useful for detecting cloud types, frontal boundaries, etc. Useful for detecting cloud types, frontal boundaries, etc.

Infrared Satellite Imagery Infrared satellite imagery is constructed from the terrestrial radiation in the longwave band 1. Cold objects, such as the tops of cumulonimbi or cirrus clouds, emit less radiation. Generally, cold objects, are depicted as bright regions on infrared images. Warm objects, such as the Earth’s surface or low clouds, emit more radiation and are generally depicted as darker areas on infrared satellite images.

Surface T = 20°C Cloud top T = -45°C Cumulo- nimbus Cirrus T = -50°C

Infrared Imagery GOES 4 km resolution at 11 µm GOES 4 km resolution at 11 µm Polar orbiter 1 km resolution Polar orbiter 1 km resolution Low clouds and fog hard to detect as it has same temp as ground Low clouds and fog hard to detect as it has same temp as ground

Water Vapor Imagery Water vapor imagery is constructed from emitted radiation in the upper level water vapor band (about 6.7 µm). Regions of the upper troposphere with higher concentrations of water vapor emit more infrared (longwave) radiation in this band. Regions of the upper troposphere with higher concentrations of water vapor emit more infrared (longwave) radiation in this band.

Water Vapor Imagery (Cont.) Generally, more humid areas in the upper troposphere appear as bright regions (or green/blue/purple) on water vapor images and drier areas appear as darker regions (or orange). Looping of water vapor images provides an indication of the flow of air in the upper levels of the troposphere.

Water Vapor Imagery GOES 8 km resolution GOES 8 km resolution Clouds do not have to be present Clouds do not have to be present Only shows mid-level moisture Only shows mid-level moisture

GOES Special Rapid Scan Imaging Rapid Scan Operations (RSO) – imagery is collected over a reduced area at 7.5 minute intervals. Super Rapid Scan Operations (SRSO) – imagery is collected over a greatly reduced sector at 1 minute or 30 second intervals. The 1 minute interval produces 22 images in an hour in 2 segments of 11.

GOES Imaging Normal operation (times are past the hour) 0-15 minutes – full disk scan full disk scanfull disk scan minutes – full disk scan minutes – full disk scan minutes – full disk scan Total of 4 full disk scans per hour.

GOES Imaging (Cont.) Rapid Scan Operations Rapid Scan Operations (times are past the top of the hour). Rapid Scan Operations 0-15 minutes – normal full disk scan minutes – Rapid Scan minutes – Rapid Scan minutes – normal full disk scan minutes – Rapid Scan minutes – Rapid Scan

GOES Imaging (Cont.) Super Rapid Scan Operations (times are minutes past the top of the hour) minutes – normal full disk scan minutes – 1 Super Rapid Scan minutes – 10 Super Rapid Scans minutes – normal full disk scan minutes – 1 Super Rapid Scan minutes – 10 Super Rapid Scans Superstorm Sandy Video

The GOES Sounder The GOES sounder measures emitted radiation in 18 infrared bands and reflected solar radiation in one visible band. The energy in the bands is affected by the temperature, moisture and ozone content of the air. Scans every 30 min Scans every 30 min Resolution 8 km by 10 km Resolution 8 km by 10 km Uses GFS to create sounding Uses GFS to create sounding

The GOES Sounder (Cont.) The measurements are used to determine the vertical profiles of temperature and moisture, the surface and cloud top temperatures, and the ozone distribution.

GOES Sounder Channels

Sounder imagery

GOES Sounder Products Total Precipitable Water (PW) Lifted Index/CAPE Cloud Top Pressure Ozone

Sounder Derived Products

Polar-orbiting Operational Environmental Satellites (POES) POES are currently operated by NOAA and the Defense Meteorological Satellite Program (DMSP). These two programs are merged into the National Polar-orbiting Operational Environmental Satellite System (NPOESS).

Polar-orbiting Research Meteorological Satellites Agencies such as NASA launch research satellites to demonstrate technology, but operational meteorologists will use some of the products of these satellites. Examples of this include the TRMM (Tropical Rainfall Monitoring Mission) and the SeaWinds or QuikSCAT satellite.

Operating POES Future of POES

POES Examples HERE

Some Sources of Real Time Satellite Imagery ml ml tc_home.html tc_home.html

Some Other Satellite Links isit/satellite_links.html isit/satellite_links.html

Forecasting Tips Fog and Stratus Visible: bright, very little texture Visible: bright, very little texture IR: gray, dull- can be invisible IR: gray, dull- can be invisible Might need to look over what it passes overMight need to look over what it passes over

Cumulus Clouds Visible: small dotted clouds Visible: small dotted clouds IR: Hard to pick up because of 4 km resolution IR: Hard to pick up because of 4 km resolution

Cumulonimbus Visible: very bright, elliptical Visible: very bright, elliptical IR: very cold (bright) elliptical IR: very cold (bright) elliptical

Stratiform Layers Include: Include: StratusStratus NimbostratusNimbostratus AltostratusAltostratus CirrostratusCirrostratus Visible: Extensive bright white sheet Visible: Extensive bright white sheet IR: Gray or white sheet IR: Gray or white sheet

Cirriform Layers Visible: thin fibrous pattern (like you observe from ground), but can be undetectable Visible: thin fibrous pattern (like you observe from ground), but can be undetectable IR: appear cold but terrain below may appear cold IR: appear cold but terrain below may appear cold

The Future! GOES-R scheduled to launch early 2016