List of Variables Recorded or Routinely Computed from T-28 Observations

Each different variable in the data stream is indexed with a unique tag number. These may vary from project-to-project. Those used for 1999 deployments are listed here.
  
Tag Variable Remarks
     
100 Time The T-28 data system is always set to universal time, and recorded in a 24-hour format. It is maintained daily within a second of WWV unless otherwise noted.
     
101 Dynamic Pressure 1  
     
102 Dynamic Pressure 2 Both dynamic pressures are read from the same pitot tube line (with the inlet out on the right wing) using two different but nearly identical sensors. [hPa]
     
103 Static Pressure 1  
     
104 Static Pressure 2 Both static pressures are read from the same static pressure line (inlet on the rear fuselage) using two different but nearly identical sensors. [hPa]
     
105 Rate of Climb The instantaneous rate of change of aircraft altitude, read from a standard aircraft variometer. The recorded data are unfiltered and much noisier than the damped cockpit display. [m s-1]
     
106 Rosemount Temperature This is static temperature computed from the reading of a standard, deiced, Rosemount aircraft total air temperature probe. It commonly suffers from wetting and reads low in clouds. [°C]
     
107 Reverse Flow Temperature This is static temperature computed from the reading of a platinum resistance element placed inside a custom-design "reverse-flow" housing.It normallydoes not get wetincold clouds or in regions of high precipitation water concentration. Apparently, ice may sometimes build up to such an extent on the housing that temperature readings are affected even though the sensor is not wetted. Its response to changes in angle of attack is greater than that of the Rosemount probe. [°C]
108 Manifold Pressure Pressure inside the engine manifold (an indicator of power being developed by the engine) is recorded from a standard aircraft engine presssure sensor. [inches of mercury]
     
109 Acceleration Vertical acceleration is determined by a Humphrey gyro-stabilized accelerometer. [g’s]
     
110 Pitch The accelerometer also gives angle of the fuselage relative to horizontal (positive for nose up). [deg]
     
111 Roll Finally, the accelerometer gives angle of the wings relative to horizontal. Angle is positive for a left bank (left wing down). [deg]
     
113 VOR The VOR gives the direction to the VORTAC (a radio direction-finding beacon used by aircraft) to which it is tuned. [deg]
     
114 DME1 This is distance to the VORTAC to which the DME is tuned. [n mi]
     
116 Voltage Regulator Voltage of power source for some instruments. [volts]
     
117 Heading Indicates direction (from magnetic north) towards which the aircraft is heading. [deg]
118 NCAR True Airspeed Airspeed computed by an analog circuit; can be used to clock PMS OAP-2D probes. Less accurate than "Calculated TAS", Tag 211
     
119 PMS End Element 1 Voltage readings of PMS OAP-2D probe end diodes. Used to monitor for fogging and icing of probe.
     
120 PMS End Element 2  
     
121 Interior Temperature Temperature inside the data acquisition system computer in the baggage bay. [°C]
     
124 Heater Current Total current consumed by de-icing circuits (A).
     
130 Event Bits Bits corresponding to various events recognized by the data system, including an indication that the system is running, that the in-cloud switch is activated by the pilot (when visually entering cloud), that the foil impactor is running, and that the cockpit voice recorder is activated.
     
131 GPS Warning Codes Bits corresponding to various status messages from the GPS system.
     
140 FSSP size counts This tag contains information concerning the number of counts in each of the 15 available FSSP size channels. [number per channel per second]
     
141 FSSP total counts The total number of droplets counted by the FSSP during a second.
     
142 FSSP average diameter The arithmetic average diameter of all droplets recorded during a second. [m m]
     
143 FSSP concentration The actual concentration of droplets computed from FSSP counts divided by the volume sampled in 1 s ("Standard method"). A rudimentary correction for probe activity is made. [# cm-3]
     
144 FSSP Water The liquid water concentration computed from the FSSP data for a second ("Standard method"). [g m-3]
     
145 FSSP Activity The fraction of time the FSSP is active during the current second.
     
147 PMS 2DC Shadow Or Count The number of times the 2D probe was triggered out of its wait state by the passage of a new particle. [# s-1]
     
148 FSSP Equivalent Diameter  
at one second intervals, using "standard method" counts and sizes.
     
149 Variance in FSSP Equivalent Diameter Variance around the equivalent diameter, computed as 

using "standard method" counts and sizes.
     
150 Hail size counts This tag contains information on the number of particles in each of the 14 hail spectrometer size channels. [number per channel per second]
     
151 Slow Particle The number of particles rejected because they passed through the hail spectrometer too slowly (indicating they were probably water or ice shed from the probe structure rather than airborne hydrometeors). [number per second] 
     
152 Hail total counts of (150) Total number of particles accepted by the hail spectrometer. [number per second]
     
153 Hail average diameter The average diameter of all particles accepted by the hail spectrometer in the last second. [cm]
     
154 Hail concentration The computed concentration corresponding to all particles accepted by the hail spectrometer in the last second. [number per cubic meter]
     
155 Hail Water The mass concentration computed from the observed particle spectrum assuming spherical particles and a bulk particle density of 0.9 grams per cubic centimeter. [grams per cubic meter]
     
160 Top Field Mill  The electric field indicated by the low sensitivity channel on the field mill mounted in the aircraft canopy looking up. Field mill data are recorded at 20 Hz. [kV m-1]
     
161 Bottom Field Mill  The electric field indicated by the low sensitivity channel on the field mill located in the baggage bay door looking down. [kV m-1]
     
162 Left Field Mill  The electric field indicated by the low sensitivity channel on the field mill mounted in the left wing tip facing outward. [kV m-1]
     
163 Right Field Mill  The electric field indicated by the low sensitivity channel on the field mill mounted in the right wing tip facing outward. [kV m-1]
     
168 Fifth Field Mill  The electric field indicated by the low sensitivity channel on the fifth field mill, located forward in one of the hail spectrometer pylons under the left wing. [kV m-1]
169 Sixth Field Mill  The electric field indicated by the low sensitivity channel on the 6th field mill, located aft in the hail spectrometer pylon under the left wing (kC m-1)
     
172 Latitude Computed internally in the GPS receiver. [deg]
     
173 Longitude Also computed internally in the GPS receiver. [deg]
     
174 Groundspeed Computed internally in the GPS receiver (by differentiating the position data with respect to time). [m/s]
     
175 Ground Track Angle The direction towards which the aircraft is moving relative to the ground, with respect to magnetic north. [deg]
     
176 Magnetic Deviation The difference between magnetic north and true north as indicated automatically by the GPS receiver based on the current position. [deg]
     
177 Time Since Solution The time since the GPS was last able to compute an accurate position solution based on a sufficient number of satellites. The GPS updates position based on dead reckoning if it does not have a sufficient number of satellites in view. [s]
     
178 GPS Altitude Geometric aircraft altitude. [m MSL]]
     
190 FSSP Gated Strobes Number of accepted droplet counts. [s-1]
     
191 FSSP Total Strobes Total number of droplet counts. [s-1]
     
192 FSSP Reference Voltage Reference voltage for FSSP opto-electronics.
     
200 Date As indicated by the data acquisition system computer clock. [yymmdd]
     
201 Month mm [integer number]
     
202 Day dd [integer number]
     
203 Year yy [integer number]
     
204 Flight A serial number assigned to each T-28 flight beginning with the "first" research flight. (Flight #1 occurred in 1972.)
     
205 Altitude The altitude in a standard atmosphere corresponding to the recorded static pressure. [m]
     
206 qe The equivalent potential temperature corresponding to the recorded temperature and assuming saturation with respect to liquid water (should be valid in-cloud). [K]
     
207 Saturation Mixing Ratio The mixing ratio of water vapor corresponding to saturation with respect to liquid water at the recorded temperature. [g kg-1]
     
208 Point dz/dt The rate of change of altitude of the aircraft computed by differentiating the pressure altitude with respect to time. This represents an independent estimate of the rate of climb to be compared to tag 105. [m s-1]
     
209 Indicated Air Speed What the airspeed would be if the aircraft were flying at sea level and indicating the observed dynamic presure. [m s-1]
     
210 Updraft (uncorrected) The estimated upward speed of the air relative to the ground computed from changes in the aircraft altitude and other factors, but not corrected for horizontal aircraft acceleration. [m s-1]
     
211 Calculated TAS The true speed of the aircraft relative to the air computed from the observed dynamic and static pressures, and temperature. [m s-1]
     
212 Updraft Correction Factor A correction to tag 210, the simple (uncorrected) updraft calculation, that accounts for horizontal accelerations of the aircraft. [m s-1]
     
213 Cooper Updraft The sum of the uncorrected updraft and the correction factor. [m s-1]
     
214 Kopp Updraft An updraft calculated somewhat differently than the Cooper updraft [Kopp, 1985]. In most situations, it yields a less noisy and more physically plausible updraft result for the T-28 than the Cooper method. [m s-1]
     
215 Geopotential Altitude Altitude computed from changes since takeoff in static pressure and temperature, using the hydrostatic equation. [Not routinely computed, but can be computed upon request.] [m]
     
216 Turbulence The turbulent energy dissipation rate estimated from the spectrum of observed fluctuations in true airspeed following a method developed by McCready. [cm2/3 s-1]
     
217 Air Density Computed from the recorded temperature and static pressure. 

[kg m-3]
     
218 J-W Mixing Ratio The mixing ratio of cloud water per unit mass of dry air based on the J-W reading and computed air density. [g kg-1]
     
219 FSSP Mixing Ratio The mixing ratio of cloud water per unit mass of dry air calculated from the FSSP water concentration. [g kg-1] 
     
220 Hail Mixing Ratio The mixing ratio of hail mass per unit mass of dry air based on the computed hail water and air density. [g kg-1] 
     
244 FSSP equivalent J-W Liquid Water An estimate of the liquid water

concentration the J-W probe should record, based on the observed FSSP droplet spectrum and the assumption that the J-W responds incompletely to droplets larger than 30 mm diameter. [g m-3]
     
260 Ambient Vert Electric Field The component of the ambient electric field that is vertical in the aircraft frame of reference. Positive means a positive test charge would drift upward relative to the aircraft in the field. [kV m-1]
     
261 Vert Electric Field due to aircraft charge The field due to charge on the aircraft, computed by summing the readings of the top and bottom mill and normalizing based on self-charging tests. Positive means a positive test charge would be repelled away from the aircraft due to its charge. [kV m-1] 
     
262 Ambient Hor Electric Field The ambient field oriented perpendicular to the aircraft along the wings, positive meaning a positive test charge would drift to the right in the field. [kV m-1] 
     
263 Hor Electric Field due to aircraft charge The field due to charge on the aircraft, computed by summing the wingtip mill readings and normalizing. Positive means a positive charge would be repelled away from the aircraft due to its charge. [kV m-1] 
     
264 Ambient Vert Field (roll cor) The component of the ambient field that is truly vertical with respect to earth coordinates. [kV m-1] 
     
265 Ambient Hor Field (roll cor) The component of the ambient field perpendicular to the aircraft path and truly horizontal with respect to earth coordinates. [kV m-1] 
266 Ex X-component of ambient horizontal electric field, based on Mo et al (1999). Positive means a positive test charge would drift in the direction of the aircraft under the influence of the field. [kV m-1]
     
267 Ey Y-component of ambient horizontal electric field, based on Mo et al (1999). Positive means a positive test charge would drift to the right of the direction of the aircraft under the influence of the field. [kV m-1]
     
268 Ez Z-component of ambient electric filed, based on Mo et al (1999). Positive means a positive test charge would drift upward under the influence of the field. [kV m-1]
     
272 Latitude (deg) GPS coordinates broken into separate degree and minute components.
     
273 Latitude (min) GPS coordinates broken into separate degree and minute components.
     
274 Longitude (deg) GPS coordinates broken into separate degree and minute components.
     
275 Longitude (min) GPS coordinates broken into separate degree and minute components.
     
276 Ground Track Angle (True N) The direction of motion relative to the ground with respect to true north, derived from the GPS ground track angle with respect to magnetic north.
     
290 X-acceleration Acceleration in the direction of aircraft motion. Acceleration backward (deceleration) yields a positive value. [g]
     
291 Y-acceleration Acceleration perpendicular to the direction of aircraft motion, along the direction of the wings. Acceleration toward the left yields a positive value. [g]
     
292 Z-acceleration Vertical acceleration. Upward acceleration produces a positive value. [g]
     
[Tags 341 – 349 can be computed for upon request.]
     
341 Calculated FSSP Total Count Observed FSSP total counts with minor 

corrections made in an attempt to correct for the effects of ice particles on FSSP droplet spectra. Not fully proven. [s-1]
     
342 Calculated FSSP Average Diameter FSSP average droplet diameter estimated from spectra calculated using the Baumgardner FSSP data reduction procedure. [m m]
     
343 Calculated FSSP Concentration Droplet concentration estimated using the Baumgardner FSSP data reduction procedure. [# cm-3]
     
344 Calculated FSSP Water Liquid water concentration estimated using the Baumgardner FSSP data reduction procedure. [g m-3]
     
345 Calculated FSSP Mixing Ratio Computed from "calculated FSSP water" (tag 344) and "air density" (tag 217). [g kg-1]
     
348 Calculated FSSP Equivalent Diameter Computed as for tag 144, but using FSSP spectra derived using the Baumgardner FSSP data reduction procedure. [mm]
     
349 Variance of the Calculated FSSP Equivalent Diameter Computed as for tag 149, but using FSSP spectra derived using the Baumgardner FSSP data reduction procedure.