AATS-14 measurements during COAST

1. AATS-14 measurements during COAST J. Livingston R. Johnson M. Kacenelenbogen C. Chang P. Russell

2. Data acquisition and analysis • 14 data channels centered at wavelengths (l) 354 – 2139 nm • Data sampled at 10 Hz and averaged over 2 sec during flights • 2-sec voltage means and stds written to raw data file • September MLO sunrise calibration results used to calculate aerosol optical depth (AOD) at 13 l (using OMI columnar ozone data) and columnar water vapor (CWV) at 941 nm • AODs at 12 l, CWVs, estimated uncertainties archived with a/c latitude, longitude, GPS and P altitudes, static P, and spectral AOD fitting parameters in modified Gaines-Hipskind formatted files for 10/26, 10/27, and 10/28 flights

3. System performance issues • Tracking changes caused by reflection off wing during aircraft turns • Reflection of the sun off the higher wing occasionally led to a small deviation in AATS-14 tracking that yielded slightly elevated or depressed signals in some science channels. • These reflections occurred when the relative azimuth of the AATS-to-sun vector coincided with the azimuth of the vector defined by the Twin Otter fuselage/higher wing intersection and the higher wing tip. • All affected data have NOT been removed from the archived files. • Computer clock timing uncertainties • Twin Otter computer, AATS can computer, AATS laptop • Anomalously high AODs in 1558-nm channel • These were observed during the MLO calibration and during COAST flights. The source of this problem may have been a light leak in the 1558-nm filter. AODs in this channel have been excluded from the archived files.

4. System performance issues • Tracking changes caused by reflection off wing during aircraft turns • Reflection of the sun off the higher wing occasionally led to a small deviation in AATS-14 tracking that yielded slightly elevated or depressed signals in some science channels. • These reflections occurred when the relative azimuth of the AATS-to-sun vector coincided with the azimuth of the vector defined by the Twin Otter fuselage/higher wing intersection and the higher wing tip. • All affected data have NOT been removed from the archived files. • Computer clock timing uncertainties • Twin Otter computer, AATS can computer, AATS laptop • Anomalously high AODs in 1558-nm channel • These were observed during the MLO calibration and during COAST flights. The source of this problem may have been a light leak in the 1558-nm filter. AODs in this channel have been excluded from the archived files.

5. Data Examples 28 Oct

9. Bottom altitude late early Top altitude

10. AOD latitudinal traces and spectra

11. Profiles

12. Comparison of AOD spectra on 10/26 and 10/28 Bottom altitude Top altitude late early

13. 26 Oct Columnar water vapor increased with time 28 Oct Columnar water vapor decreased with time