Vertical Temperature Plot Information

1.        The type of plots are selected from the radio buttons located in the center below the plot by simply clicking on one of these selections:

·          Single station w/ multiple time plots

·          Multiple stations w/ same time plot

·          Single station 2D flat contour plot

·          Single station 3D surface plot

2.   The station/measurement types to be plotted are selected from the list below the radio buttons and are selected from the left list which contains the type of measurement such as “Profiler RASS” and “Mtp5”.  If a plot does not appear, it means that for the date-time range selected that no data exists in the database for that time period.  Some parameters are automatically loaded every hour into the database, while some are manually loaded by personnel every several days until the process can be automated.

3.    The “Profiler RASS” data comes from the ‘Seattle Profiler’, an instrument on the site of the Seattle office of the National Weather Service located at Sand Point.  The instrument has been providing temperature and wind data from the surface up to 1600 meters since 1993.  ‘RASS’ is an acronym for ‘Radio Acoustic Sounding System’.

Users should note that the output of the ‘RASS’ profiler is ‘Virtual Temperature’, which is a calculated temperature.  Instead of the actual temperature, virtual temperature in Kelvin (Tv) is defined in a way that allows us to use the gas constant for dry air.  Because moist air is lighter than dry air, and therefore less dense, the virtual temperature is always greater than the actual temperature for the same reason that warm air is less dense than cold air.  The use of ‘Virtual Temperature’ allows meteorologists to use the same temperature equation for dry air even though moisture is present.  A simple approximate formula for virtual temperature is Tv = T(1 + 0.61r) where T is the ambient temperature in Kelvin and r is the water vapor mixing ratio in grams water per kilogram of air (g/kg).

Below are some examples of the difference between actual temperature and virtual temperature:

The virtual temperature of air that is 10 deg C and saturated with a dewpoint of 10 deg C (8g/kg r =.008) would be 11.4 deg C (+1.4);  the virtual temperature of air that is 20 deg C with a dewpoint of 16 deg C (11g/kg r =.011) would be 22 deg C (+2);  and a parcel of air with a temperature of 30 deg C with a dewpoint of 22 deg C (16g/kg r =.016) would have a virtual temperature of 33 deg C (+3).

4.     The Mtp5 is a new microwave profiler technology whose technique for determining the air temperature profile is based on measuring the thermal radiation of the atmosphere at the center of the molecular oxygen absorption line.  The technique can also be referred to as microwave remote sensing.  Since the atmosphere is an extremely weak source, the measurement requires a very sensitive radiometer and a mechanically rotated mirror-reflector which captures the thermal radiation at different zenith angles from 0 up to 90 degrees. 

                The temperature resolution of the Mtp5-HE is largely determined by the signal-to-noise ratio of the received microwave radiation and therefore also decreases with altitude.  Because a change of direction in the temperature profile cannot be determined from a single point measurement, inversions may be shown shifted slightly upwards in altitude.

                The temperature resolution specified for an adiabatic atmosphere from 0 – 1000 meters is +/- 0.3 to 0.4 deg C.  The resolution specified for an inverted atmosphere from 0 – 1000 meters is +/- 0.8 to 1.2 deg C. 

5.     The starting and ending date and time values can be selected by clicking on the ‘calendar’  or  ‘clock’ icon or simply by typing the date - time values in the controls.  There are several button controls that are available to quickly adjust the dates or times by clicking on the appropriate button.

6.     A ‘View Grid of Plotted Data’ button is available to allow the user to view all of the actual values of the plots in a data grid.

7.     Two other buttons, ‘Create Data File’ and ‘Download File’ are available to save the plotted data values to a file on the user’s PC.