Public Access to the Network for the Detection of Stratospheric Change Database

Martin P. Chipperfield, School of the Environment, University of Leeds, Leeds, UK (martyn@env.leeds.ac.uk)
Paul A. Newman, NASA Goddard, Greenbelt, USA (newman@notus.gsfc.nasa.gov)

 

Introduction

The Network for the Detection of Stratospheric Change (NDSC) is a set of research stations extending from 80°N to 90°S) for observing and understanding the physical and chemical state of the middle atmosphere. Since 1991 ozone and key ozone-related chemical species and parameters have been measured at this network in order to detect and understand stratospheric changes and to assess the impact of these changes on the troposphere and on global climate. In particular the NDSC aims to provide data for:

• Making the earliest, possible identification of changes in the ozone layer and to discern their causes.
• Establishing links between changes in stratospheric ozone, UV radiation at the ground, tropospheric chemistry and climate.
• Testing and improving multi-dimensional stratospheric chemical-dynamical models.
• Providing an independent calibration of satellite sensors of the atmosphere.

These aims require high quality data and, accordingly, since the inception of the NDSC, much effort has been invested into instrument inter-comparison, calibration, and software validation. The result is a self-consistent data set suitable for addressing the above aims. In order to permit the widest possible usage, all data over two years old is made publicly available. This article briefly describes the NDSC database and how to access it.

 

Example Data

The NDSC data base consists of ground-based and sonde observations of ozone and other key species in stratospheric chemistry and climate. Ground-based column observations are obtained with Dobson, UV-visible, microwave, and Fourier Transform infrared (FTIR) spectrometers. The list of species observed includes O₃, HCl, ClONO₂, ClO, NO, NO₂, HNO₃, HF and other tracers. Ozone, aerosols and temperature vertical profiles are also obtained using lidar and sondes. The NDSC database also includes UV flux at the ground and supporting meteorological data.

Examples of NDSC data are given in Figures 1 and 2. Figure 1 shows observations of column HCl and HF at the NDSC Primary station of Jungfraujoch (47ºN, 8ºE). These observations, which include those obtained before the start of the NDSC but which have been subjected to the same NDSC validation, clearly show the increase in the stratospheric loading of halogens due to the use of CFCs which has led to stratospheric ozone depletion in both the polar regions and at mid-latitudes. Following the Montreal Protocol, and its amendments, the increase in HCl slowed and now appears to have levelled off. In the future we expect the stratospheric loading of chlorine and fluorine to decline. Continued observations are an essential component of monitoring the rate of this recovery.

 

Fig. 1. Evolution of the daily mean total column abundance of hydrogen chloride and hydrogen fluoride measured above the Jungfraujoch station (47ºN, 8ºE) since 1977, as part of the University of Liege commitment to the NDSC. For details see European Research in the Stratosphere (1997), and Mahieu et al., (2000). Figure courtesy of R. Zander.

 

Figure 2 shows column sunset and sunrise observations of NO₂ at Lauder (45ºS, 170ºE). On top of the diurnal and annual variations, this data set shows long-term variations. Relatively low NO₂ was observed around 1992, following the eruption of Mt. Pinatubo. However, after allowing for these aerosol-induced variations and the expected increase in NO₂ from increasing N₂O, the clear upward trend throughout the 1990's may be larger than current models predict. These NDSC data are therefore essential for comparison to models that test our understanding of atmospheric chemistry and transport.

 

Fig. 2. Monthly means of sunset (pm, blue) and sunrise (am, red) NO₂ slant column measurements at Lauder (45ºS, 170ºE) as part of NIWA's commitment to the NDSC. The right-hand scale shows approximate values for vertical column NO₂ based on an air mass factor of 17.5. For details see Liley et al., (2000). Figure courtesy of P. Johnston.

Accessing the Data

NDSC data over two years old is now publicly available. Access to this data is available through anonymous ftp access to the ozone.wwb.noaa.gov server. It is expected that users of these NDSC data will consult the on-line documentation and reference articles to fully understand the scope and limitations of the instruments and resulting data. Scientific users of the data are encouraged to contact directly the appropriate NDSC Principal Investigator (listed in the data documentation on the web page) to ensure the proper use of specific data sets. The PI can also be contacted if you wish to use data less than two years old.

Further information on the NDSC can be obtained from the NDSC home page (www.ndsc.ws). This web site principally provides a link to the public ftp database, but also includes maps of the NDSC sites, instrument information, available data sets, and contact information.

 

Acknowledgements

Because of its world-wide dimension, the NDSC has been recognised as one of major components of the international upper atmosphere research program. As such, it has been endorsed by national and international scientific agencies, including UNEP and the International Ozone Commission (IOC) of IAMAP. It has also been recognised by WMO as a major contributor to WMO's Global Ozone Observing System (GO3OS) within the frame of its Global Atmosphere Watch (GAW) Programme.

 

References

European Research in the Stratosphere, ISBN 92-827-9719-8, EC-DG XII, 1997.

Liley, J.B., et al., Stratospheric NO2 variations from a long time series at Lauder, New Zealand, J. Geophys. Res, 11633-11640, 105, 2000.

Mahieu, E., et al., Proc. of Stratospheric Ozone 1999, 27/9 to 1/10/1999, St. Jean de Luz, France, Air pollution research Report 73, EUR 19340, pp. 99-102, 2000.