Observed responses of mesospheric water vapor to solar cycle and dynamical forcings.

This study focuses on responses of mesospheric water vapor (H2O) to the solar cycle flux at Lyman-α wavelength and to wave forcings according to the multivariate ENSO index (MEI). The zonal-averaged responses are for latitudes from 60°S to 60°N and pressure-altitudes from 0.01 to 1.0 hPa, as obtained by multiple linear regression (MLR) analyses of time series of H2O from the Halogen Occultation Experiment (HALOE) for July 1992 to November 2005. The solar responses change from strong negative H2O values in the upper mesosphere to very weak, positive values in the tropical lower mesosphere. Those response profiles at the low latitudes agree reasonably with published results for H2O from the Microwave Limb Sounder (MLS). The distribution of seasonal H2O amplitudes corresponds well with that for temperature and is in accord with the seasonal net circulation. In general, the responses of H2O to MEI are anti-correlated with those of temperature. H2O responses to MEI are negative in the upper mesosphere and largest in the northern hemisphere; responses in the lower mesosphere are more symmetric with latitude. The H2O trends from MLR for the lower mesosphere agree with those reported from time series of microwave observations at two ground-based network stations.

The impact of nonuniform sampling on stratospheric ozone trends derived from occultation instruments.

This paper applies a recently developed technique for deriving long-term trends in ozone from sparsely sampled data sets to multiple occultation instruments simultaneously without the need for homogenization. The technique can compensate for the nonuniform temporal, spatial, and diurnal sampling of the different instruments and can also be used to account for biases and drifts between instruments. These problems have been noted in recent international assessments as being a primary source of uncertainty that clouds the significance of derived trends. Results show potential "recovery" trends of ∼2-3 % decade-1 in the upper stratosphere at midlatitudes, which are similar to other studies, and also how sampling biases present in these data sets can create differences in derived recovery trends of up to ∼1 % decade-1 if not properly accounted for. Limitations inherent to all techniques (e.g., relative instrument drifts) and their impacts (e.g., trend differences up to ∼2 % decade-1) are also described and a potential path forward towards resolution is presented.

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

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 publicly available at doi:10.7289/V5TD9VBX.