ILRC Lidar tutorials

Sunday, 25 June 2017

  • Time: 09:00 – 17:30
  • Location: Amphitheater, AN building, “Politehnica” University of Bucharest, 313 Splaiul Independentei, sector 6, Bucharest

ICLAS extends a warm welcome to young scientists and other newcomers who wish to attend the Lidar Tutorials at ILRC28 on Sunday, 25 June 2017. These free tutorials, presented before the technical sessions, provide a quick, basic introduction to the lidar technique for atmospheric researchers, software developers, and lidar program staff. The Lidar Tutorials are very popular: at ILRC26 in Greece and ILRC27 in New York, the venues were filled and the lectures received enthusiastic reviews. Any ILRC participant is welcome to attend, and there is no extra fee for participating.

This year’s tutorials have a special technical theme: lidar as a polarization instrument. After an introductory overview, an international team of outstanding lidar researchers will present
lectures starting with the basics of polarization lidar and its uncertainty budget followed by several applications to atmospheric aerosol studies. The tutorials will conclude with a talk on the current status and future plans for lidar as an essential global atmospheric monitoring tool.

Those who plan to attend the Lidar Tutorials are kindly asked to indicate this when registering for ILRC28 through the online registration tool.


Moderator:

Gary Gimmestad, Principal Research Scientist Emeritus, Georgia Tech Research Institute, USA


Lectures:
Short overview of the lidar technique and its main applications – Prof. Alex Papayannis, National Technical University of Athens, ICLAS President, ILRC28 Co-Chair

In this short introduction we will review the basic lidar fundamental physical principles (emission-atmospheric interaction-detection of laser radiation) and the various lidar applications in atmospheric physics. Main focus will be given to the applications of elastic, Raman, HSRL, DIAL and Doppler lidars, as vertical profilers for molecular/atomic air pollutants/substances, temperature, winds and atmospheric structure from the lower troposphere to the mesosphere. A main list of the basic lidar literature will be provided.

Polarizing lidars and the instrument function – Dr. Volker Freudenthaler, Institute for Meteorology, Ludwig-Maximilians University, Germany

Although the determination of the linear depolarization ratio with lidar seems to be a simple task at first sight, systematic errors can skew the results a great deal. Different unknown systematic errors in different instruments make it difficult to compare the results and to compile a consistent picture of the aerosol properties from measurements around the globe. For the correction of known systematic errors and for the estimation of the uncertainty of the correction we first need a model of the lidars with a mathematical description of the measurements which contribute to the determination of the linear depolarization ratio. This lecture will introduce the model that has recently been published for this purpose [1]. An important part deals with the relative calibration of the signal channels which contribute to the linear depolarization ratio. A basic understanding of the Mueller-Stokes formalism [2,3] will facilitate to follow the lecture.
1. Freudenthaler, V., About the effects of polarising optics on lidar signals and the Δ90-calibration, Atmos. Meas. Tech., 2016, 9, 4181-4255, doi:
10.5194/amt-9-4181-2016
2. Hauge, P., Muller, R. and Smith, C., Conventions and formulas for using the Mueller-Stokes calculus in ellipsometry, Fourth International
Conference on Ellipsometry, Berkeley, CA, August 20-22, 1979, Retrieved from: https://escholarship.org/uc/item/13t0c9d0, 2012
3. Chipman, R. A., in Bass, M. (Eds.) Handbook of Optics, Volume I (3rd Edition), Chap. 14, Mueller matrices, McGraw-Hill, 2009

Retrieval of the aerosol optical parameters, associated assumptions and uncertainties – Dr. Ioannis Binietoglou, National Institute of R&D for Optoelectronics, Romania

This talk will give a birds-eye view of aerosol optical property retrievals from typical aerosol lidar systems. First, we will briefly  discuss pre-processing routines required to correct instrumental effects on lidar signals. Then, we will go through the algorithms to obtain aerosol optical properties from different lidar systems: elastic, multi-angle, Raman, high spectral resolution, and depolarization lidar. For each of these techniques we will examine the benefits, limitations, and underline assumptions needed for a successful aerosol retrieval. Finally, we will discuss strategies to determine the error of the resulting products. At the end of the lecture, the students will be able to understand the benefits and pitfalls of aerosol lidar products.

Depolarization – an important parameter in aerosol typing – Dr. Silke Gross,  German Aerospace Center, Germany

The particle depolarization ratio is an intensive aerosol property only dependent on the aerosol type and not on its amount. Different aerosol types show quite different values of the particle depolarization ratio. Together with other intensive aerosol properties, e.g. the lidar ratio or the color ratio, it is an important parameter to distinguish between different aerosol types. This lecture will give an overview of the intensive optical properties of different aerosol types and how they can be used for aerosol typing. Furthermore we will discuss how these intensive optical properties, in particular the particle depolarization ratio, can be used to separate different contributing aerosols to aerosol mixtures.

Depolarization – an important parameter in aerosol-cloud interaction – Dr. Albert Ansmann, Leibniz Institute for Tropospheric Research, Germany

During the last five years new ways to use polarization lidars in atmospheric research were explored. Besides the separation of the three main aerosol components (marine aerosol, desert dust, and continental aerosol pollution such as urban haze and biomass burning smoke) in terms of extinction coefficient and mass concentration, robust and comparably simple methods have been developed to estimate height profiles of cloud condensation nucleus (CCN)  and ice-nucleating particle INP) concentrations. CCN and INP concentrations, measured  in the cloudy environments,  are the most important aerosol parameters in   aerosol-cloud interaction studies. The lidar technique is the only method that permits observations of aerosol and cloud parameters with cloud-process-resolving vertical and temporal resolution.

The methodology applied to retrieve CCN and INP profiles will be outlined in the seminar  and measurement examples obtained during field campaigns in the Eastern Mediterranean will be discussed and will demonstrate the potential of the new polarization lidar method in the field of atmospheric and climate research.

Global observations: lidar networks and space lidar missions – Dr. Ulla Wandinger, Leibniz Institute for Tropospheric Research, Germany

Polarization lidar is applied in global observations of aerosols, clouds and their interactions. The technique contributes to a better understanding of direct and indirect radiative forcing effects and has the potential to monitor atmospheric trends in a changing global climate. Both space-borne missions and ground-based networks contribute to the four-dimensional picture of the distribution of aerosols and clouds in the Earth’s atmosphere. The lecture will give an overview on existing lidar networks as well as current and planned space lidar missions, their observing strategies, measurement products and scientific achievements.