Texas Air Quality Study 2000
Airborne Lidar Aerosol data

Data Description

Aerosol backscatter data were measured with the NOAA/ETL airborne, nadir-looking ozone lidar using its aerosol channel at a wavelength of 359 nm. The 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 aerosol backscatter profiles extending from about 2500 m MSL to the surface. The vertical resolution of the aerosol data is 15 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 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, followed by the aerosol backscatter data in m-1 sr-1 for each range gate. Note that the aerosol 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.

The accuracy of the lidar aerosol backscatter data is difficult to assess because the airborne lidar aerosol channel is not calibrated and independent aerosol backscatter measurements were not available for comparison with the lidar data. We typically calibrate the aerosol retrieval by guessing the aerosol backscatter at a specific altitude and then tie the backscatter profile to this reference value. In addition, the profile of extinction-to-backscatter ratio is needed for the aerosol backscatter retrieval. Again, we assume reasonable values based on model calculations for various aerosol types. For these reasons the airborne lidar backscatter data provide information about the aerosol distribution in a qualitative rather than quantitative sense. This is especially true for the TexAQS 2000 study, because the aerosol distribution in the Houston area tended to be inhomogeneous both horizontally and vertically, making it more difficult to find suitable calibration regions for the lidar aerosol backscatter retrieval. However, the lidar aerosol data provide an excellent overview of the 2-dimensional distribution of aerosols, showing where regions of high and low aerosol loading are. The lidar aerosol data have also been used to retrieve mixing depths.


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