Day 5:  Blacksburg, VA

Equipment:  Pen, pencil, and notebook.

Schedule:

8:30        Meet in hotel conference room and discuss plans for the busy day.
9:30        Arrive at the National Weather Service Office in Blacksburg.
11:30       Break for lunch at local restaurant.
1:00        Arrive at Virginia Tech Seismology Lab.
3:00        Return to hotel and review days activities.
4:00        Break for rest.
6:00        Dinner
8:30        Arrive at Virginia Tech Astronomy Observatory to view nighttime sky.
 
 

Above is a picture of the National Weather Service office in Blacksburg, Virginia.  They are located at 1750 Forecast Drive.

Scientific Significance:  The National Weather Service (NWS) is a perfect stop for students studying the Geosciences.  It allows students to see first hand the hard work, detail, and technology that is needed to forecast the weather.  The responsibilities of the NWS is to assign warnings and watches (that's their #1 mission), make short-term forecasts (0-6 hour), seven day forecasts, provide outlooks such as drought statements, fire weather forecasts, airport forecasts, and river forecasts (Keighton, 2002).  A tour of the NWS office allows students to grasp an understanding of the instruments used in forecasting weather.  A few of these instruments include satellite (infrared, visible, and water vapor), radar, and weather balloons.
 

• Satellite Products:

Above are examples of visible (A), infrared (B), and water vapor (C) satellite images.  Each product is  unique and provides meteorologist with information.  Visible satellite imagery (A) represents the amount of sunlight that is scattered back into space.  This scattering is due to clouds, aerosols, atmospheric gases, and the Earth's surface.  Thicker clouds have a higher albedo, that is they scatter more light, and thus appear brighter than thin clouds on a visible image.  A disadvantage of visible imagery is that it is hard to distinguish among the elevation of clouds since they can all have similar albedos; this distinction can be made using infrared images (B).

Infrared satellite images are based upon temperature and brightness.  With infrared imagery, warm objects appear darker than colder objects.  Therefore, warmer low clouds appear darker than cooler high clouds.  Color enhanced infrared images, such as that shown above (B), specify levels of infrared energy with a certain color.  For example, shades of yellow and orange indicate infrared emissions consistent with thunderstorms.  This is due to infrared energy being proportional to brightness temperature, and higher cloud tops being cooler than those at low altitudes; higher cloud tops are typically associated with strong thunderstorms.

Finally, water vapor images (C) are useful for locating areas of moist and dry air.  Darker colors indicate dry air while brighter colors/white indicate moist air.  This information is useful in understanding middle tropospheric wind patterns and jet streams. (Chaston, 1999)
 

• Doppler Radar (WSR-88D; NEXRAD):  Doppler radar is technology that has proven invaluable to meteorology.  The highly sensitive active remote sensor not only picks up particles (such as raindrops, hail, snow, virga, even insects) moving away from the radar, but also particles moving towards the radar.  This has proven very helpful in determining the location, intensity, and movement of precipitation, as well as rotation within clouds.  By studying the velocity patterns of wind picked up by doppler, meteorologists can issue tornado warnings before one ever makes landfall.  Rotation is detected by assigning one set of colors to air moving away from radar and another set of colors to air moving towards the radar.  Warm colors such as red,  yellow, and orange are assigned to air moving away from doppler, whereas cool colors such as green, blue and violet are assigned to air coming towards radar.   If red and green also indicate high wind speeds and a meteorologist sees an area with red and green beside one another, then he/she knows that rotation is occurring there and  a warning should be issued (Funk, 2002).

        Doppler Radar in Blacksburg, VA
 
 

    Products generated by NEXRAD include base reflectivity, composite reflectivity, layer maximum reflectivity, base velocity,
    storm-relativie velocity, and vertically integrated liquid.  To learn more about these products and doppler radar visit
    http://www.crh.noaa.gov/lmk/soo/88d/doppler.htm.
 

• Weather Balloons/Skew -t Diagrams:

    Once the information is obtained from the balloon, it is plotted to create an upper air sounding of the atmosphere.  The temperature,
    dewpoint, and winds are plotted versus pressure and height within Earth's atmosphere.  This plot is known as a skew T plot or
    diagram.  On a skewt plot, pressure lines are plotted horizontally in blue and are on an inverse log scale.  Temperature lines are also
    in blue, however, they angle 45 degrees to the right.  The green lines are dry adiabats, while the dashed light-blue lines are saturation
    adiabats.  The yellow lines are constant mixing ratio.  Finally, the sounding is plotted as two white lines:  the right line is the
    temperature, the left line is the dewpoint profile.  Wind speeds and height information is also found on the plots.  Below is a sample
    of a skew T plot. (Vietor, 1998).  To learn more on how to interpret skew T diagrams visit:
    http://weather.unisys.com/upper_air/skew/details.html

Note:  Along with forecasting weather, the NWS plays an important role in hydrologic and climate forecasts.  Precipitation is such a key
factor in the hydrologic cycle that it only makes sense that the NWS would report on drought conditions, flood warnings, and any daily
hydrologic data.  Likewise, the amount of precipitation in an area contributes to the climate of that region.  Therefore, the NWS also constructs climate reports and long term outlooks.  To learn more about hydrologic and climate reports put out by the NWS visit:
http://www.erh.noaa.gov/er/rnk/
 
 

Location:  The seismology observatory is located in Derring Hall on the campus of Virginia Tech in Blacksburg, VA.

Earthquakes are caused by the breaking of rock within Earth's crust.  So, what causes the rock to break?  There are three forces that can act on rock to force it beyond its elastic limit, thus causing it to break and produce vibrations.  These forces are tension, compression, and shear.  Typically, these forces are found at plate boundaries.  Divergent plate boundaries are locations where the plates of Earth's crust are moving away from one another; this type of motion produces tension forces.  Convergent plate boundaries are areas where Earth's crust are "coming together" resulting in "compression" of the rock.  Finally, if plates are moving past one another with little or no vertical movement, shear forces are at work in locations called transform boundaries.   Virginia, however, is not located at any of these plate boundaries.  Rather, Virginia is located in the middle of North American plate.  So, can Virginia have earthquakes?  Absolutely!  In fact, the seismology observatory has recorded over 160 earthquakes since 1977 with about 25 of these being felt.  Below is a diagram of earthquakes recorded in Virginia; the different sizes of the circles indicate different magnitudes (VTSO, 2001).

The seismology observatory has been recording Virginia earthquakes since the first world-wide seismic network was established in 1963, with one of its stations being set up in Blacksburg.  Since then, the stations have upgraded to an analog seismic network in 1977, to a digital network in 1985.  In 1991, VA Tech combined with North Carolina and Tennessee to form the Southern Appalachian Cooperative Seismic Network.  This network allows for earthquake monitoring and data exchange (VTSO, 2001)  Within their present network, the observatory is using a S-13 seismometer.  A seismometer is an instrument that records the seismic waves, or energy waves, produced by an earthquakes. A picture of this instrument is shown below (Geotech, 2002).

There are three types of seismic waves that radiate from the focus of an earthquake.  Primary waves, or P waves, are compressional waves that travel through bedrock carrying rock material in the same direction as wave motion.  P-waves are the fastest traveling waves, and thus are picked up by a seismograph first.  Secondary waves, or S-waves, are longitudinal waves that travel through bedrock carrying rock material at a right angle to wave direction.  S-waves are the second fastest seismic wave, and thus are picked up by a seismograph second.  Finally, surface waves are the last type of seismic wave.  Surface waves are long waves that travel across Earth's surface.  It is the slow surface waves that are picked up last by a seismograph and are the most destructive of the seismic waves.  Below is a seismogram of the January 17, 1994 Northridge, VA earthquake, which registered a magnitude of 6.8 (A) and the January 22, 1995 Pulaski earthquake, magnitude 2.9.  Both of these earthquakes were recorded in Blacksburg (VTSO, 2001).

A tour of the seismology observatory allows students to see the equipment needed to record earthquakes, as well as the opportunity to review seismograph readings.  By studying P and S wave arrival times from three different stations, students could also try their hand at determining the epicenter of an earthquake.  The VT observatory is an important stop on our trip because it reinforces the fact that earthquakes can occur at locations far from plate boundaries.  It also offers a view into Virginia's own earthquake history.
 
 

Location:  Prices Fork Road, Christiansburg.

Scientific Significance:  What better way to end our busy day in Blacksburg than to look out into the beautiful nighttime sky and view the stars and planets beyond our Earth? The Physics Department at Virginia Tech offers the use of their Astronomy Observatory to the public.  To obtain the key, you must  contact the Physics Department and go through a brief training session on how to use their expensive telescopes and equipment.  For a field trip such as this, I am sure a member of the Physics Club will be happy to assist.

Assuming a trip in the fall, below is a representation of what constellations and planets would be in the sky in the Blacksburg area around 9:45 P.M. in late September.  Some common constellations visible late September include Cassiopeia, Ursa Major, Ursa Minor, and Bootes.  Planets visible September 2002 include Venus and Pluto in the southwestern sky and Uranus and Neptune in the southeastern sky.  Study the sky dome below for more detail (Walker, 1998).
 
 

                                                                               
Mars                Mercury                   Neptune                Pluto                           Uranus                    Venus