The Stratospheric Water and Ozone Satellite Homogenized (SWOOSH) database: a long-term database for climate studies

Abstract

Abstract. In this paper, we describe the construction of the Stratospheric Water and Ozone Satellite Homogenized (SWOOSH) database, which includes vertically resolved ozone and water vapor data from a subset of the limb profiling satellite instruments operating since the 1980s. The primary SWOOSH products are zonal-mean monthly-mean time series of water vapor and ozone mixing ratio on pressure levels (12 levels per decade from 316 to 1 hPa). The SWOOSH pressure level products are provided on several independent zonal-mean grids (2.5, 5, and 10 • ), and additional products include two coarse 3-D griddings (30 • long × 10 • lat, 20 • × 5 • ) as well as a zonal-mean isentropic product. SWOOSH includes both individual satellite source data as well as a merged data product. A key aspect of the merged product is that the source records are homogenized to account for inter-satellite biases and to minimize artificial jumps in the record. We describe the SWOOSH homogenization process, which involves adjusting the satellite data records to a "reference" satellite using coincident observations during time periods of instrument overlap. The reference satellite is chosen based on the best agreement with independent balloon-based sounding measurements, with the goal of producing a long-term data record that is both homogeneous (i.e., with minimal artificial jumps in time) and accurate (i.e., unbiased). This paper details the choice of reference measurements, homogenization, and gridding process involved in the construction of the combined SWOOSH product and also presents the ancillary information stored in SWOOSH that can be used in future studies of water vapor and ozone variability. Furthermore, a discussion of uncertainties in the combined SWOOSH record is presented, and examples of the SWOOSH record are provided to illustrate its use for studies of ozone and water vapor variability on interannual to decadal timescales. The version 2.5 SWOOSH data are

An updated version of a gap-free monthly mean zonal mean ozone database

“…Although having a somewhat broader vertical resolution than the other data sources used in the BDBP v1.1.0.6 database, the large data quantity and high data quality of the Microwave Limb Sounder makes it an attractive target data source for incorporation into the BSVertOzone database. The usefulness of MLS ozone data has already been shown through its use in several other combined ozone databases, e.g., GOZCARDS (Global OZone Chemistry And Related trace gas Data records for the Stratosphere; Froidevaux et al, 2008) and SWOOSH (Stratospheric Water and OzOne Satellite Homogenized data set; Davis et al, 2016). Given this pedigree, MLS measurements were included in the creation of the BSVertOzone database.…”

“…Recognizing the higher data quality of the ozonesonde measurements below 15 km, as each ozonesonde is individually calibrated, ozonesonde data are used at 15 km and below as the standard. Once the standard has been selected, it is then necessary to either (i) find coincident measurements from the standard data set and from the measurement system to be adjusted, as done, for example, in Davis et al (2016), or (ii) use an independent and gap-free data set that can be used as a transfer standard for adjusting measurements to the standard. The first approach is problematic if a measurement from the chosen standard is not available for every measurement from the data set to be adjusted.…”

“…Preferably, this initial standard is sufficient in its global and temporal coverage to allow robust estimates of bi-ases and drifts of all other measurement sets. Here we follow the quality assessment from Hubert et al (2016) and the suggested ozone standard from Davis et al (2016) and, for levels above 15 km (about 118 hPa), chose measurements from SAGE II as the standard. Recognizing the higher data quality of the ozonesonde measurements below 15 km, as each ozonesonde is individually calibrated, ozonesonde data are used at 15 km and below as the standard.…”

“…Problems related to this extrapolation could cause the slightly increased ozone depletion in the early part of the BSVertOzone Tier 1.4 time series compared to BDBP. Davis et al (2016) developed one of the more recent vertically resolved ozone data sets: SWOOSH. This data set has already been used in a number of studies for a wide variety of analyses Steinbrecht et al, 2017;Ball et al, 2017).…”

“…Several ozone databases were created that combine (merge) measurements from (i) the same type of instruments that were flown on different satellites Wild and Long, 2018), (ii) two different satellite instruments Bourassa et al, 2014), or (iii) several different satellite instruments Davis et al, 2016). All of these databases cover the stratosphere, but only parts of the troposphere, if at all.…”