Texas Air Quality Study 2000
Airborne Lidar Ozone data

Data Description

Ozone mixing ratio data were measured with the NOAA/ETL airborne, nadir-looking ozone lidar. Ozone data are from 11 flights covering the time period from 8/25/2000 to 09/12/2000. The lidar was typically flown at an altitude of about 3500 m MSL, with the ozone profiles extending from about 2500 m MSL to the surface. The vertical resolution of the ozone data is 90 m and the time resolution is 10 s. At a typical aircraft speed of 60 m/s this corresponds to a horizontal resolution of approx. 600 m.

The data files are in ASCII format. Each file contains a short header followed by the data. The data are arranged in 50 columns: time in decimal hours UTC, aircraft altitude in m MSL, latitude (positive=north of equator), longitude (negative = west of Greenwich), lidar beam elevation angle in deg, lidar beam azimuth angle in deg, and ozone mixing ratio in ppbv for each range gate. Note that the ozone data are arranged by range away from the aircraft not altitude. To convert to altitude MSL the range to gate has to be subtracted from the aircraft altitude. The bad data value is -999.0.

RMS errors are range or altitude dependent as lidar SNR gets smaller with increasing range (decreasing altitude). Ozone RMS errors are typically a few ppbv above 1500 m MSL and increase to 10 - 15 ppbv near the surface, but may be as high as 30 to 40 ppbv in high ozone plumes. These values are for individual 10-s records. When N records are averaged together the RMS error decreases by approx. a factor of sqrt(N).

Lidar ozone has to be corrected for differential aerosol backscatter and extinction effects. The magnitude of this correction term can be significant under certain circumstances and is dependent on aerosol properties, such as extinction to backscatter ratio as well as backscatter and extinction wavelength dependence. These aerosol properties cannot be directly measured with the airborne lidar, so we assume reasonable values based on model calculations for various aerosol types. Discrepancies between the assumed and actual aerosol properties may result in biases in the ozone data for some flight segments and certain altitudes. These biases can be on the order of 10 - 15 ppbv. In the data QC process we made sure that the amount of data potentially affected by this aerosol bias is minimized.


Data Policy

We request that a proper acknowledgment to the "NOAA Earth System Research Laboratory / Chemical Sciences Divison" accompany the use of this data in any publications and presentations. If the use of the data in a publication constitutes a major or reasonably significant aspect of an article, co-authorship by an ESRL/CSD scientist is appropriate; please discuss any such planned use with the scientists listed below. We welcome collaborations and will lend our scientific expertise in interpretation and evaluation of the data.

Contact scientist:



Link to:
Airborne Ozone Lidar
ETL TexAQS page
Division Home Page
Last updated: 4 October 2007