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Class 4 Current Weather
Intro to Satellites
There are two main types of weather satellites… Polar orbi5ng • Orbit longitudinally • Pass over the poles • Al;tude ~ 850km
• Great detail of meteorological and non-‐met. features
• Only capture a few images of a par;cular loca;on per day
Geosta5onary • Orbit directly over equator; sta;onary w.r.t. Earth • More images/day
• 36,000 km al;tude – less detail • US has two: GOES-‐E and GEOS-‐W
There are two main types of weather satellites… Polar orbi5ng • Orbit longitudinally • Pass directly over the poles • Al;tude ~ 850km
• Great detail of meteorological and non-‐met. Features
• Only capture a few images of a par;cular loca;on per day
Geosta5onary • Orbit directly over equator; sta;onary w.r.t. Earth • More images/day
• 36,000 km al;tude – less detail • US has two: GOES-‐E and GOES-‐W
(Polar-‐orbi;ng) (Geosta;onary)
In meteorology, the 3 channels of GOES we use the most are:
1. Visible (VIS)
2. Infrared (IR)
3. Water vapor (WV)
Visible satellite imagery… …senses reflected solar radia;on (visible light) …approximates the albedo (reflec;vity) of objects • shiny things " bright white (thick clouds, ice sheets)
• less shiny things " not as white/light grays (wispy clouds)
• not shiny things " dark grays (land, water)
…can’t be used at night
Blowing desert sand: link Smoke from forest fires: link Fog: link Developing thunderstorms: link Clouds or snow?: link
Cool things to see on visible satellite imagery…
Infrared Satellite Imagery
• Senses infrared energy emibed upward by ground, clouds, etc.
• Objects emit infrared energy according to their temperature – Higher in the atmosphere = colder – Closer to the surface = warmer
• Brightest whites = high clouds • White or light gray = clouds, snow • Dark gray or black = land, water
Images may be colorized to show more detail
Things to see on IR satellite imagery…
Thunderstorm development: link Arc;c airmass moving over snow-‐covered ground: link Hurricanes vs. midla;tude cyclones: link In this class, we’ll mostly just use this to look for clouds: link " Feb. 2013 Nor’easter
Remnants of subtropical storm Andrea (May 11, 2007)
Visible Infrared
22 November, 2011
Water Vapor Satellite Imagery
• Water vapor absorbs and reradiates preferen;ally at a par;cular infrared band (6-‐7 microns) – WV imagery shows this band
• Detects WV in the middle and upper levels of the troposphere – Why not LL? Because ML/UL usually have enough moisture to obscure LL moisture signal
Water vapor satellite imagery can help us see dry slots.
Water vapor satellite imagery can help visualize moisture advec5on.
July 2-‐6, 2013: This plume of deep moisture contributed to heavy flooding in the FL panhandle and southeast AL!
Water vapor satellite imagery can even help us see turbulence.
Most importantly for us, water vapor satellite imagery allows us to visualize the large-‐scale flow (even when there are few/no clouds).
12.310 homepage Home " Remote obs " Satellite " USA " WV " L-‐12
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