BADC Help File: NDACC Data

This file contains a summary of the instrument documentation to help you use the NDACC data held at the BADC.
Much of the information in this help file is condensed from the NDACC documentation which was supplied to the BADC by the NDACC team at NOAA.

Contents

1. Introduction
2. The Measurement Stations and Instruments
   • 2.1 Measurement sites
   • 2.2 The Instruments
   • 2.3 Data Protocols

1. Introduction.

The main focus of the NDACC project is to make global measurements in the altitude region from the tropopause to about 50km. The following measurements have been identified as being of the highest priority to the NDACC:

• Column ozone
• Vertical profile of ozone (0-70km)
• Temperature (0-70km)
• Vertical profile of ClO
• Vertical profile of H2O
• Vertical distribution of aerosols
• Vertical profile or column of NO2
• Stratospheric column of HCL
• Vertical profiles of long-lived tracers: CH4 and N2O
• Other species (HNO3, ClONO2 and OH)

These priorities are based on the assumption that existing and planned satellite measurements activities will continue, as will the ground-level monitoring of ozone and long-lived gases by existing networks.

2. The Measurement Stations and Instruments

2.1 Measurement Sites

2.1.1 Primary Stations

The NDACC has 5 Primary Stations which make up the core of its activities. All except the New Zealand station are composites i.e. they are composed of more than one measurements site.

2.1.2 Complementary Stations

There are also over 20 Complementary Stations which make measurements under the complementary measurements protocol of the NDACC. These measurements are selected to provide specific benefit to the NDACC primary activities, for example through their geographic location, measurement technique or addition scientific value.

2.1.3 Global view

A map provided by NDACC also displays the distribution of the NDACC sites around the world.

2.2 Instruments

Instruments were selected on the basis of being remote sensors, capable of continuous, long-term field operation, potentially in remote locations. Depending on specific site characteristics such as geography, meteorology and complementary existing programs, each of the primary NDACC stations are equipped with most or all of the set of instruments listed below, in order to make the following measurements:

Species	Altitude Range	Instrument
O3 column	total column	Dobson, Brewer, UV/visible spectrometers
O3 profile	0-20km 15-45km 25-75km	YAG Lidar excimer lidar microwave
Temperature	0-45km	lidar
ClO	25-45km	microwave
H2O	0-30km > 20km	balloon hygrometer microwave
Aerosols	0-30km	lidar
NO2	stratospheric column	UV/visible spectrometer
HCl	stratospheric column	Fourier transform infrared spectrometer (FTIR)
CH4	stratospheric column	FTIR
N2O	20-50km	microwave, FTIR
HNO3	stratospheric column	FTIR
ClONO2	stratospheric column	FTIR
OH	40-60km	UV fluorescence excimer lidar
HO2	30-60km	microwave

More information on instruments can be found in the documentation and in the metadata files produced by the NDACC.

For nearly all of the instruments, it is desirable to locate the monitoring station at high elevation (>2000 meters) in order to minimize the tropospheric water and aerosol columns. The goal of understanding the cause of changes, rather than merely detecting them, requires that the instruments be co-located to an extent consistent with the temporal and spatial requirements of the measurements and the realities of site availability. Where it is not feasible to co-locate all the instruments on the same site, a composite station may be formed with individual instruments or groups of instruments at different sites.

2.3 Data Protocols

The network's data lie at the heart of its contribution to understanding stratospheric change. The nature of long-term trends measurement requires these data to be fully verified before they can be used for comparison with models or to deduce trends. It is the spirit and purpose of the NDACC to foster the broadest possible collaboration among all interested scientists as quickly as possible. However, as with any good research, the Principal Investigators (PIs) bear the ultimate responsibility for data quality. In order to achieve a verifiable data set, sufficient time is needed to collect, reduce, test, analyse and intercompare the anticipated streams of continuous preliminary data from each of as many as five sites.
The NDACC data protocol is aimed at achieving the dual goals of excellent data quality and ready data access. The main features are:

• Any NDACC PI may establish the scientific collaborations necessary for the optimum testing and verification of their own measurements.
• All PIs shall place their preliminary analyses of measurements in the NDACC archive as rapidly as possible and no later than one year after measurement.
• Given the nature of small trends detection, it is recognised that multiple seasonal analyses may be required. It is expected that such a procedure will yield the verifiable product referred to as "NDACC data" within a two-year period after acquisition.
• After the above verification, NDACC data will be available to anyone through a centralised scientific archiving and distribution facility and will be accessible by electronic transfer.

The NDACC protocols are available from the BADC archive.