Propagation of radiosonde pressure sensor errors to ozonesonde measurements

摘要

Several previous studies highlight pressure (or equivalently, pressurealtitude) discrepancies between the radiosonde pressure sensor and thatderived from a GPS flown with the radiosonde. The offsets vary during theascent both in absolute and percent pressure differences. To investigatethis problem further, a total of 731 radiosonde/ozonesonde launches from theSouthern Hemisphere subtropics to northern mid-latitudes are considered,with launches between 2005 and 2013 from both longer term and campaign-basedintensive stations. Five series of radiosondes from two manufacturers(International Met Systems: iMet, iMet-P, iMet-S, and Vaisala: RS80-15N andRS92-SGP) are analyzed to determine the magnitude of the pressure offset.Additionally, electrochemical concentration cell (ECC) ozonesondes fromthree manufacturers (Science Pump Corporation; SPC and ENSCI/DropletMeasurement Technologies; DMT) are analyzed to quantify the effects theseoffsets have on the calculation of ECC ozone (O) mixing ratio profiles(O) from the ozonesonde-measured partial pressure. Approximatelyhalf of all offsets are > ±0.6 hPa in the freetroposphere, with nearly a third > ±1.0 hPa at 26 km,where the 1.0 hPa error represents ~ 5% of the totalatmospheric pressure. Pressure offsets have negligible effects on Obelow 20 km (96% of launches lie within ±5% O errorat 20 km). Ozone mixing ratio errors above 10 hPa (~ 30 km),can approach greater than ±10% (> 25% of launchesthat reach 30 km exceed this threshold). These errors cause disagreementbetween the integrated ozonesonde-only column O from the GPS andradiosonde pressure profile by an average of +6.5 DU. Comparisons of totalcolumn O between the GPS and radiosonde pressure profiles yieldaverage differences of +1.1 DU when the O is integrated to burstwith addition of the McPeters and Labow (2012) above-burst O columnclimatology. Total column differences are reduced to an average of −0.5 DUwhen the O profile is integrated to 10 hPa with subsequent addition ofthe O climatology above 10 hPa. The RS92 radiosondes are superior inperformance compared to other radiosondes, with average 26 km errors of−0.12 hPa or +0.61% O error. iMet-P radiosondes had average26 km errors of −1.95 hPa or +8.75 % O error. Based onour analysis, we suggest that ozonesondes always be coupled with aGPS-enabled radiosonde and that pressure-dependent variables, such asO, be recalculated/reprocessed using the GPS-measured altitude,especially when 26 km pressure offsets exceed ±1.0 hPa/±5%.