Ground-based atmospheric trace gases measurements by tunable laser heterodyne spectrometry in the mid-infrared

Objective

This proposal aims to develop a novel ground based high resolution tunable diode laser heterodyne spectrometer (TDLHS). This instrument will be portable and operate in the mid-infrared spectral region where most of the important atmospheric trace molecules have conveniently accessible vibration-rotation transitions. It will be capable of measuring, by remote sensing of solar radiation, the key target species chlorine nitrate (CIONO2) and nitric acid (HNO3).


The complementary technical expertise available within the participating groups in diode laser technology, heterodyne spectrometry, field measurements, and laser spectroscopy is matched to undertake the construction of the new TDLHS which will be specifically designed to:

- have the high sensitivity to measure the target gases chlorine nitrate and nitric acid with high accuracy in a short measurement time;
- have very high resolution to enable altitude resolved information to be obtained on the target species, and to distinguish between possible interfering trace substances;
- be sufficiently robust and compact for easy deployment at various remote ground measurement locations.

In the first instance the instrument will be employed to record high quality spectra of ClONO2 and HNO3 which are important reservoir gases. The work will be particularly focused at improving the understanding of their role in heterogeneous chemical processes and their impact on stratospheric ozone. In practice this will be undertaken in two phases; phase one will consist of monitoring from the Reims University Laboratory (a mid-latitude site) to validate the instrument, while phase two will require measurements by NPL at a suitable northern site for testing the TDLHS under field conditions.

It is recognised that the scope for accumulating substantial data on ClONO2 and HNO3 will be limited since measurement opportunities will largely be focused on testing the performance of the TDLHS. Nevertheless the final spectrometer will be able to record spectra that will enable the importance of reactions which convert stable chlorine reservoirs, such as ClONO2, into active species, to be assessed.

Programme(s)

• FP3-ENV 1C - Specific research and technological development programme (EEC) in the field of the environment, 1990-1994

Topic(s)

• 0201 - Assessment of environmental quality and monitoring

Funding Scheme

Coordinator

Participants (2)