Validation and Trend Analysis of Stratospheric Ozone Data from Ground-Based Observations at Lauder, New Zealand

Leonie Bernet,Gerald Nedoluha,Ian Boyd,Klemens Hocke,Daan Swart,Richard Querel

doi:10.3390/rs13010109

Abstract

Changes in stratospheric ozone have to be assessed continuously to evaluate the effectiveness of the Montreal Protocol. In the southern hemisphere, few ground-based observational datasets exist, making measurements at the Network for the Detection of Atmospheric Composition Change (NDACC) station at Lauder, New Zealand invaluable. Investigating these datasets in detail is essential to derive realistic ozone trends. We compared lidar data and microwave radiometer data with collocated Aura Microwave Limb sounder (MLS) satellite data and ERA5 reanalysis data. The detailed comparison makes it possible to assess inhomogeneities in the data. We find good agreement between the datasets but also some possible biases, especially in the ERA5 data. The data uncertainties and the inhomogeneities were then considered when deriving trends. Using two regression models from the Long-term Ozone Trends and Uncertainties in the Stratosphere (LOTUS) project and from the Karlsruhe Institute of Technology (KIT), we estimated resulting ozone trends. Further, we assessed how trends are affected by data uncertainties and inhomogeneities. We find positive ozone trends throughout the stratosphere between 0% and 5% per decade and show that considering data uncertainties and inhomogeneities in the regression affects the resulting trends.

Highlights

Stratospheric ozone protects life on earth from harmful solar UV radiation and is involved in multiple radiative, chemical, and dynamic processes (e.g., [1,2,3,4,5,6,7])
An additional feature of the Karlsruhe Institute of Technology (KIT) model is the possibility of accounting for biases within the trend estimation. This is helpful if the data shows some jumps or inhomogeneities, for example after instrumental changes. We apply this approach to account for the jumps that we identified in the lidar and ERA5 data (Section 3) when estimating trends
We presented stratospheric ozone time series from a microwave radiometer (MWR), a lidar, Aura Microwave Limb sounder (MLS) satellite data, and ERA5 reanalysis data from Lauder, New Zealand

Summary

Introduction

Stratospheric ozone protects life on earth from harmful solar UV radiation and is involved in multiple radiative, chemical, and dynamic processes (e.g., [1,2,3,4,5,6,7]). Anthropogenic ODS emissions caused a strong decrease in stratospheric ozone observed from the 1960s. Concentrations of stratospheric chlorine have been decreasing since 1997 [8]. Recent studies report that stratospheric ozone over Antarctica is responding to these changes and starting to recover [9,10,11,12,13,14,15]. Even though consensus exists that stratospheric ozone has stopped declining in the late 1990s [7,19,20,21,22,23,24], a general increase in stratospheric ozone has proved difficult to detect, and positive ozone trends at midlatitudes have recently been recorded only in the upper stratosphere (e.g., [7,17,18])

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Conclusion