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Satellite Help

Overview

The satellite page contains links to National-scale and regional-scale satellite images from the GOES-17 (West) and GOES-16 (East) satellites. There are also links to satellite images with the LIFR/IFR/VFR/MVFR icons overlaid. Images are provided for three of the different wavelength sensors on the satellite:

Visible

The visible images display the Earth similarly to how humans see it with their eyes or how typical cameras view it. Clouds and snow appear bright white (high albedo/reflectance) but oceans and trees are much dimmer.

IR

The infrared images display the Earth in a manner that correlates with temperature. Generally speaking, the warmer an object, the more infrared energy it emits (gives off). The satellite sensor measures this energy and calibrates it to temperature using a very simple physical relationship (Planck's Law). In the real world, clouds that are very high in the atmosphere are generally quite cold (perhaps -50 °C) whereas clouds that are very near the earth's surface can be quite warm (perhaps +5 °C). Likewise, the land may be even warmer than the lower clouds (perhaps +20 °C). Those colder clouds emit much less infrared energy than the warmer clouds and the land emits more than those warm clouds. The data measured by the satellite are calibrated and colorized according to the temperature with red shades representing higher (warmer) temperatures and blue shades representing lower (cooler) temperatures. If the temperature of the atmosphere decreases with height (which is typical), a user can get an idea of which clouds are high-level and which are low-level based on the cloud top temperature.

Water vapor

The water vapor images display the Earth in a manner that correlates to quantity of water vapor in the upper portions of the atmosphere (25,000 feet and higher in general). The actual numbers displayed on the water vapor images correspond to temperature but there is no direct relationship between these values and the temperatures of clouds (as is the case for infrared images) since this channel doesn't really "see" clouds but "sees" high-level water vapor instead. The most useful information to be gained from the water vapor images is the locations of storm systems and the jet stream. The color scale on the images can be helpful in interpreting the water vapor images. In general, regions displayed in shades of red are VERY dry in the upper atmosphere and MAY correlate to crisp blue skies from a ground perspective. On the contrary, regions displayed in shades of blue or green are indicative of a significant amount of high-level moisture and may also indicate cloudiness. This cloudiness could be high-level cirrus types or serious storms. That determination can only be made when this image is used in conjunction with the other channels.

Vis/Fog

The visible images are very good at depicting the location of low clouds that won't show up on infrared imagery. So if clouds show up in the visible and not the IR, they are likely low clouds or snow cover. But the visible image is not useful at night and thus can't be used.

As mentioned, the basic IR image won't depict low clouds. To resolve this problem, it's best to look at multiple channels. The best solution is to difference the 3.9 and 11 micron channels. This highlights emissivity differences rather than temperature. Smaller droplets like those in fog will emit less whereas hogher clouds will emit more. Then by using the proper gray shading, the low clouds can be detected.

In the images on the Vis/Fog page, low clouds show up bright and higher clouds show up as dark. The ground shows up as gray. In addition, flight categories for various airports are plotted over the imagery as a secondary verification.

URL Options

Here is a list of the URL options:

  • date=yyyymmddhhnn - This selects a specific date and time to display.
  • time=hr - This selects the initial time on the time slider (def: 0).
  • timelabform={full|simple} - This selects time slider labels. Full shows -/+ hours from current. Simple shows just the time and "Forecast for" if it's a future time.
  • refresh=min - This sets the auto-refresh time interval (def: 5 min).
  • tz=tz - This sets the time zone to show in the date header. This can be "local" which is the browser time zone or "label,offset" which is the zone name and offset in hours. For example "CDT,-5". (def: UTC).
  • region=reg - This will center the map to a specific region. Options include: "conus", "us", "northeast", "ne", "southeast", "se", "northcentral", "nc", "southcentral", "sc", "northwest", "nw", "southwest", "sw", "alaska", "ak", "hawaii", "hi", "gulfmexico", "gmx", "caribbean", "car", "europe", "eur", "southamerica", "sam", "easia", "eas", "australia", "aus", "zab", "zau", "zbw", "zdc", "zdv", "zhu", "zfw", "zid", "zjx", "zkc", "zla", "zlc", "zma", "zme", "zmp", "zny", "zoa", "zob", "zse", "ztl" (def: none).
  • center=lat,lon - This will center the map at a specific latitude and longitude. The default is 39,-97.
  • zoom=level - This sets the zoom level. The default is 4. A higher number zooms in. A lower number zooms out.
  • fullmode=(screen|window) - This sets the full screen mode. "screen" sets it to full screen. "window" sets it to fill the current browser window. The default is screen.
  • fullscreen=(on|off) - This sets the display to go into full window if fullmode=window.
  • basemap=(light|dark|simple) - This selects the type of basemap. The default is light.
  • sat={on|off} - This turns the satellite layer on or off. The default is on.
  • satprod={ir|vis|wv} - Specifies the type of satellite image. The default is ir.
  • satopacity=# - Specifies the satellite image opacity (0=transparent to 1=opaque). The default is .5.
  • satloop={on|off} - Specifies whether the satellite is looping on page load. Default is on.
  • satimages=# - Specifies the number of images in satellite loop. The default is 5.
  • satlabform={on|simple|off} - Specifies the satellite label format. The choices are "on" which shows type of image and time, "simple" which shows only image type and "off" which shows no label. The default is "full".
  • highways={on|off} - Turns highway layer on or off. These are primarily interstates. The default is off.
  • roads={on|off} - Turns roads layer on or off. These are primarily US and state highways plus some city streets. The default is off.
  • counties={on|off} - Turns county layer on or off. The default is off.
  • jetroutes={on|off} - Turns the jetroutes layer on or off. The default is off.
  • firs={on|off} - Turns the ARTCC/FIR layer on or off. The default is off.
  • metric={on|off} - Specifies to display data in metric units. The default is off.
  • mouseformat={deg|dm|dms} - Specifies to format for the mouse location: degrees, degree/frac. minute, degree/minute/second. The default is deg.
  • level=## - Specifies value of the level in the level slider. The default is none.
  • hover={on|off} - Turns on hover for features. The popups will come up when mouse hovers. Default is off.