Data Dictionary | Earth Observing Laboratory

Data Dictionary

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 6^th 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	q_e	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. [cm^2/3 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.

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