HR: 0830h
AN: A41E-0738    [PDF]
TI: Development of {\it in situ} Formaldehyde Sensors
AU: * Keutsch, F N
EM: frank@huarp.harvard.edu
AF: Department of Chemistry Harvard University, 12 Oxford Street, Cambridge, MA 02138 United States
AU: Hanisco, T F
EM:
AF: Department of Chemistry Harvard University, 12 Oxford Street, Cambridge, MA 02138 United States
AU: Anderson, J G
EM:
AF: Department of Chemistry Harvard University, 12 Oxford Street, Cambridge, MA 02138 United States
AB: {\it In situ} measurements of formaldehyde (CH$_{2}$O) are important for a better understanding of photochemistry and CH$_{2}$O can be used as a tracer, especially for large-scale convective events. In the latter case the measurement of CH$_{2}$O being entrained and detrained from the convective event at all altitudes with instruments optimized for these conditions is of particular interest. This requires {\it in situ} observations of CH$_{2}$O with high sensitivity ($<$10 pptv/sec.) and high vertical and temporal resolution, resulting from the large variation of CH$_{2}$O concentrations from the troposphere to the lower stratosphere and the short photochemical lifetime of CH$_{2}$O. In addition, such observations are of interest for validation of OMI, which is being deployed on the AURA satellite. We discuss the development of state-of-the-art CH$_{2}$O sensors based on both mid-infrared integrated cavity output spectroscopy (ICOS) and UV laser-induced-fluorescence (LIF) and cavity-ringdown spectroscopy (CRDS) employing novel laser technology. The sensitivities of these are expected to be 50 pptv/10sec., 25 pptv/10sec.,and 1 pptv/10sec. for ICOS, CRDS, and LIF, respectively. The compact and light-weight ICOS and CRDS instruments will be ideally suited for observations in the troposphere whereas the high sensitivity LIF instrument will be used in the upper troposphere and stratosphere, which will also allow a direct comparison of the two instruments. We have developed a calibration method that replaces permeation tubes, which require careful calibration themselves. Instead our CH$_{2}$O calibration utilizes a microinjector that introduces a highly repeatable and well-known amount of CH$_{2}$O into the detection axis. This method can also be employed during field deployments. The strategy of simultaneous ICOS and LIF detection tied into laboratory and field calibrations will bring the accuracy and quality of laboratory kinetics studies to {\it in situ} observations and will allow a detailed and fundamentally important analysis of systematic errors. Progress on the laboratory systems will be discussed.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0340 Middle atmosphere--composition and chemistry
DE: 0341 Middle atmosphere--constituent transport and chemistry (3334)
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting