A suite of weather satellites in geosynchronous (also called geostationa=
ry)
orbit provides a constant view of the Earth with their visible, infrared and
water vapor sensors. Each satellite remains over a fixed spot on Earth's
equator so their views of Earth remain the same. These satellites are cruci=
al
to storm surveillance, particularly over data-sparse areas. The Applicat=
ions
portion of Investigation 3B in the Weather Studies Investigations Manual=
displays visible views from the U.S. Geostationary Operational Environmental
Satellite (GOES) East when sunset was occurring =
on the
equator directly under the satellite (subsatellite
point) for those astronomically important days of equinoxes and solstices.
These geosynchronous satellites provide monitoring of the Earth with full d=
isk
views available on the Internet at 6-hour intervals.
The
1= . Figure 7 in the Applications section of Investigation 3B is the full-disk visible view from GOES East for a September 23 autumnal equinox. The terminator or sunset line is shown as a dashed line f= rom pole to pole through the subsatellite point abo= ve the equator at 75° W longitude. The left half of the Earth is illuminated <= b>[(more in the Northern Hemisphere)(equall= y in both hemispheres)(more in the Southern Hemisphere)]. Compare this satellite image to Figure 3 of the introductory portion of Investigation 3B. At this time the sun's rays are oriented perpendicular to Earth's axis.
2=
. While
a satellite view for the vernal or spring equinox is not shown, the
illumination pattern and solar ray orientations [(would
3= . The winter solstice view as seen by the GOES East geosynchronous satellite woul= d be that of [(Figure 8)(Figur= e 9)] of the Applications portion of the investigation. The date at the ti= me this investigation is being written is 23 September 2009, less than twenty-= four hours following the autumnal equinox this year. As shown in Investigation 3B Figure 2 the Earth view is essentially the Autumnal Equinox. Thus, over the next months, the sun's rays will become increasingly more inclined to the Earth's axis.
The continuing orbital movement shown in Investigation 3B Figure 2 causes the sun's subsolar point to move southward on the Earth until reaching the Tropic of Capricorn (23.5° S latitude) on the winter solstice view as in the December figur= e. This continually changing position of the sun's rays relative to Earth's ax= is provides the primary astronomical foundation for the measured energy inputs plotted in the Figure 1 graph of solar radiation in the beginning of this Investigation 3B. The satellite views of Figures 7, 8 and 9, as well as oth= er images of the Investigations Manual, can be also obtained from the webpage = = http://www.ametsoc.org/amsedu/dstreme/olws_images/invmanimgs.html.
4= . Full disk views of Earth are available online in near real time. Image 1 is the full-disk visible view from the European METEOSAT geosynchrono= us satellite at 0600Z 23 September 2009. Because the METE= OSAT's subsatellite point is over the equator at 0°= ; longitude and Z time (UTC) is the local standard time at 0° longitude (called the Prime Meridian), the image coincides with local sunrise along the Prime Meridian at this time.
At sunrise along the Prime Meridian, the Eart= h in Image 1 is illuminated [(only in the eastern half)(fully over the whole disk)(only = in the western half)]. One-half of the global Earth is always illumina= ted by the sun.
5=
. A
bright area can be seen along Africa's east coast just south of the
"horn" jutting into the
You can verify this position by going to the = U.S. Naval Observatory website listed in the Monday Current Weather Studies (http://www.usno.navy.mil/USNO/astronomical-applications/data-= services/earthview) and entering the data -Year: 2009, Month: September, Day: = 23, Hour: 6, and Minute: 00, then click Show Earth Views. The map model shows the position of the sun defining the angle for the sun glint of the satellite image.
6= . The polar views on the Naval Observatory website below the Mercator map also sh= ow that, at this time of year the autumnal equinox, the Earth is illuminated <= b>[(more in the Northern Hemisphere)(equally in both hemispheres)(more in the Southern Hemisphere)].
7= . Image 2 is a full-disk visible view from METEOSAT geosynchronous satellite at 1200Z 23 September 2009, six hours following the Image 1 view. The sun was shining directly down on the Prime Meridian in this METEOSAT view. Note that the sunlight has moved toward the west, the result of Earth actually rotati= ng toward the east (with the satellite synchronously rotating with it)!
In the METEOSAT Image 2 satellite view, the E= arth is illuminated [(only in the eastern half)(fully over the whole disk)(only in the western half)].<= /p>
8=
. Clouds
stand out as bright white blotches that reflect some of the sun's visible
light. The broad expanse of the Sahara desert of northern Africa and the de=
sert
area of the
Full disk visible and infrared satellite images similar to those used in this investigation can be found via the course website Satellite sec= tion link, "GOES Satellite Server", then GOES Full Disk, METEOSAT, MTS= AT (Japanese satellite) or Indian Ocean Images in the left menu list. In this = way you can track Earth's rotation through its sunrises and sunsets and keep ta= bs on storm systems around the world.
Record your responses to items in CWS Activities 3A and 3B on the Investigations
3A_Answers and Investigations
3B_Answers for transmission to your course mentor.
Instructions for Communications with Mentor:
After completing this week's applications, transmit the following work to y=
our
LIT mentor by Monday, 28 September 2009, or as coordinated with your mentor=
: .
Return to <=
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