Methodology for deriving the telescope focus function and its uncertainty for a heterodyne pulsed Doppler lidar Pentikäinen, Pyry Ortiz-Amezcua, Pablo The Doppler lidar and ceilometer data used in this study were obtained from the Atmospheric Radiation Measurement (ARM) user facility, managed by the Office of Biological and Environmental Research for the U.S. Department of Energy Office of Science. Doppler lidars provide two measured parameters, radial velocity and signal-to-noise ratio, from which winds and turbulent properties are routinely derived. Attenuated backscatter, which gives quantitative information on aerosols, clouds, and precipitation in the atmosphere, can be used in conjunction with the winds and turbulent properties to create a sophisticated classification of the state of the atmospheric boundary layer. Calculating attenuated backscatter from the signal-to-noise ratio requires accurate knowledge of the telescope focus function, which is usually unavailable. Inaccurate assumptions of the telescope focus function can significantly deform attenuated backscatter profiles, even if the instrument is focused at infinity. Here, we present a methodology for deriving the telescope focus function using a co-located ceilometer for pulsed heterodyne Doppler lidars. The method was tested with Halo Photonics StreamLine and StreamLine XR Doppler lidars but should also be applicable to other pulsed heterodyne Doppler lidar systems. The method derives two parameters of the telescope focus function, the effective beam diameter and the effective focal length of the telescope. Additionally, the method provides uncertainty estimates for the retrieved attenuated backscatter profile arising from uncertainties in deriving the telescope function, together with standard measurement uncertainties from the signal-to-noise ratio. The method is best suited for locations where the absolute difference in aerosol extinction at the ceilometer and Doppler lidar wavelengths is small. 2020-06-25T11:46:03Z 2020-06-25T11:46:03Z 2020-05 info:eu-repo/semantics/article Pentikäinen, P., O'Connor, E. J., Manninen, A. J., & Ortiz-Amezcua, P. (2020). Methodology for deriving the telescope focus function and its uncertainty for a heterodyne pulsed Doppler lidar. Atmospheric Measurement Techniques, 13(5). [https://doi.org/10.5194/amt-13-2849-2020] http://hdl.handle.net/10481/62730 10.5194/amt-13-2849-2020 eng http://creativecommons.org/licenses/by/3.0/es/ info:eu-repo/semantics/openAccess Atribución 3.0 España European Geosciences Union