atmPrf_format_2012-02-10: file format Name template: 2010.215_predict/exphs/2010.DDD_RFXX/atmPrf.PUXX.2010.DDD.HH.MM.GGG.KKK.RFXX.VVUU.txt PUXX Receiver ID DDD day of year GGG GPS occulting satellite pr KKK GPS high elevation prn used for differencing HH Hour of starting time of occultation (using start of file) MM Minute of starting time of occultation RFXX Flight ID VVUU Version identifier, e.g. version 1 is 0101 for the 2010-01-17 release VV refers to the version of the atmPrf file forma UU refers to the version of the processing procedure. Global Data: start_time: Starting time for the occultation. (using start of file) units: GPS second of week. stop_time: Ending time for the occultation.(using end of file) units: GPS second of week. fileStamp: Complete ID. atmPrf.PUXX.2010.DDD.HH.MM.GGG.KKK.RFXX.VVVV.txt curv: X, Y, and Z offset of the center of sphericity from the ECEF center of Earth at the occultation point (derived from oblate_correct). The occultation point is the point at the surface of the WGS84 ellipsoid where the straight line tangent point is closest. Currently the last point in the file at the lowest perigee hgt is the occultation point because the straight line tangent point does not usually descend lo enough in the conventional receiver recordings to intersect the ellipsoid surface The center of sphericity chosen corresponds to the radius of curvature, rfict, calculated a the ellipsoid surface. The geodetic location on the ellipsoid surface at the occultation point is defined to be the occultation point lat and longitude. units: km occpt_offset: Time from start of occultation (start of file) to time point when radius of curvature rfict and curv are calculated. This time point where rfict and curv are calculated is the occultation point. units: sec rgeoid: The height of the geoid above the reference ellipsoid at the lat/lon position of the occultation point. rgeoid can vary by +- 40 m over a typical 200 km tangent point drift. MSL_alt = ht WGS84 - rgeoid. units: km rfict: Local curvature radius of the reference ellipsoid at the occultation point. From oblate_correct, where the straight line tangent point in the occultation plane is closest to the ellipsoid. lat: Latitude of the occultation point. Using the last point in the file (at smallest perigee height). units: decimal deg lon: Longitude of the occultation point. Using the last point in the file.(at smallest perigee height). units: decimal deg azim: Azimuth angle of the occultation plane at occultation point, clockwise with respect to North direction. Using azimuth of occulting satellite relative to receiver at last point in file. units: d levels: Number of vertical levels in profile. bad: Badness flag. 1 = profile flunked quality control, 0 = Profile passed QC errstr: Error string, If bad = 1, contains the description of the problem found, else contains the null string, 'null'. Profile Data: values = -999 if missing time: GPS second of week units: sec time_hr_decimal: UTC time in decimal hours since the beginning of day. units: hr Pres: Dry pressure. units: hPa Ref: Refractivity units: N Lon: Longitude of perigee point. units: decimal deg Opt_bend_ang: Optimized partial bending angle. At high altitudes, the retrieved bending angle is too noisy to be useful. To reduce the propagation of this noise into retrieved refractivity at lower altitudes in the inverse abel calculation the retrieved bending angle is replaced for the section of profile around the maximum impact parameter. The noisy section of the bending angle profile is replaced with smoother values of bending calculated using a smooth curve fitted to the first (noisy) bending angle profile. A new refractivity profile is then calculated from this optimized bending angle profile. This version will have the entire positive elevation section, which should have very little variation in bending angle, also replaced with a smooth fit of original profile. units: rad Temp: Dry temperature units: C MSL_alt Mean sea level altitude of perigee point. MSL_alt = Hperi(height above the WGS84 ellipsoid) - Rgeoid_local. units: km Impact_parm: Impact parameter in the shifted geometry with origin offset by curv and using rfict radius of curvature. units: km Lat: Latitude of perigee point units: decimal deg Azim: Azimuth angle of the occultation plane at perigee point clockwise with respect to North direction. Using azimuth of occulting satellite relative to receiver. units: deg Bend_ang: Partial bending angle calculated in shifted geometry. Partial bending angle = negative elevation bending angle - positive elevation bending angle units: rad Neg_bend_ang: Negative elevation bending angle (ray path below the local horizon). units: rad Pos_Bend_ang: Positive elevation bending angle (ray path above the local horizon). units: rad Rgeoid_local: Height of geoid above the WGS84 ellipsoid at the perigee point. Hperi: Geometric height of the perigee point above the WGS84 ellipsoid. The refractivity profile is calculated using the inverse abel transform for each perigee height and corresponding impact parameter Because of interpolation ofimpact parameter during this process, an individual refractivity point is not related to a specific time. However, the positions of the transmitter and receiver, the original bending angle, impact parameter, and azimuth are all know as a function of time. With the known geometry and the refractivity profile, a ray-tracing program can be used to simulate the bending angles at a specific time for a specific perigee height within the refractivity profile, so that the correspondenc between refractivity at a specific height with time, location(lat,lon), bending angle and azimuth can be constructed. With this perigee height-time correspondence from the ray-tracing calculation, times can be interpolated for the perigee heights from th retrieved refractivity. All other parameters of interest are available through the correspondence with time: they can be interpolated with respect to the newly interpolated times for the retrieved refractivity perigee heights.