The Value of Homogenized Ozonesonde Networks: Twenty Years in the SHADOZ

The SHADOZ (Southern Hemisphere ADditional OZonesondes) network has evolved from augmenting tropical southern hemisphere ozone soundings at nine foundational sites to twenty years of process studies and satellite/model validation and evaluation at 14 stations spread across the tropics and subtropics in both hemispheres. As the "golden age" of limb sounding spaceborne observations has matured in capability and application, the need for global ozonesonde observations for on-going validation and assessment has grown. With a potential future gap in limb sounding observations, the SHADOZ database, that has been archiving ozonesonde profiles publicly since 1998 (http:/tropo.gsfc.nasa.gov/shadoz), will become more essential than ever. An important component of SHADOZ is ensuring that the data records are homogeneous as instrumentation and station practices change. Here, we summarize reprocessing methods applied to SHADOZ datasets and provide the first estimates of ozone uncertainty in profile and total column. The latter will be a critical element for evaluating existing and future satellite ozone profile and column measurements. Profile uncertainties are 15% or less and peak around the tropopause (15±3km) where the ozone current can approach the detection limit of the sensor. Reprocessing has led to reduced profile bias when compared to MLS satellite overpass profiles. When sonde-derived total columns of ozone are compared to EP/TOMS, OMI and OMPS overpasses, the sonde-satellite offsets are less than ±5%, well within the uncertainty of both satellite and sonde. This agreement is much improved over previous SHADOZ evaluations.