**Lidar Mapping of Near-Surface Aerosol Fields**

Lidar Mapping of Near-Surface Aerosol Fields

Tanja Dreischuh, Ivan Grigorov, Zahary Peshev, Atanaska Deleva, Georgi Kolarov and Dimitar Stoyanov Tanja Dreischuh, Ivan Grigorov, Zahary Peshev, Atanaska Deleva, Georgi Kolarov and Dimitar Stoyanov

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/65274

#### Abstract

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Near-surface atmospheric measurements over urban or industrial areas aimed at assisting the air-quality monitoring attain increasing societal significance due to the strong and direct impact of aerosol pollutions in the low troposphere on the human health. In this chapter, we present experimental results on lidar mapping of aerosol fields over the city of Sofia (Bulgaria), its suburbs and adjacent towns and villages, obtained during an extensive 7-month experimental campaign in 2015. The measurements are conducted by scanning observation zones in horizontal and vertical directions using lidar systems developed at the Institute of Electronics, Bulgarian Academy of Sciences. Based on the aerosol backscattering profiles retrieved at different azimuth or elevation angles, two-dimensional color-coded sector maps of the near-surface aerosol density are obtained, overlaid on the topological map of the Sofia region. The analysis of the lidar maps shows good correlation between the aerosol density distribution and the locations of important sources of aerosol pollutions in the zones of observation, such as city streets with intense traffic, industrial facilities, densely populated residential districts, etc. The results reported demonstrate that aerosol lidar mapping could be regarded as an effective approach for accurate and reliable determination of the density, spatial distribution, and temporal dynamics of close-to-ground aerosols, covering broad urban areas. Possibilities of incorporating synergistically lidar mapping technologies into municipal air-quality monitoring systems are also discussed.

Keywords: aerosol, lidar, scanning lidar, near-surface aerosol lidar mapping, air-quality monitoring

#### 1. Introduction

The poor ecological state of the environment is a serious global problem which arose as a result of the rapid development of industry, agriculture, urbanization, and transport. Significant

© The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and eproduction in any medium, provided the original work is properly cited.

factors affecting the state of the environment are both natural (hydrometeors, volcanic ash, desert dust, smoke aerosols, etc.) and anthropogenic (industrial, fuel combustion, fires, heating, etc.) atmospheric aerosols or particulate matter (PM) [1]. The aerosols are fine solid or liquid particles, determining largely the climate, temperature, and dynamic structure of the atmosphere, the functioning of ecosystems, the microphysical properties of clouds and various chemical and photochemical processes in air [2]. The concentration of aerosols in the atmosphere determines the air quality, and in turn affects the human health [[3] and references therein]. The fine and ultrafine aerosol particles are particularly harmful for human health, as they more easily penetrate and accumulate in the human body and lead to an increase in cardiovascular and respiratory diseases and even to lung cancer [4, 5]. Because of the above facts and considerations, atmospheric aerosols have been the subject of more intensive research in recent decades [6, 7]. Particularly, near-surface atmospheric measurements over densely populated or industrial areas, purposed to help monitor air quality, have attained increasing societal significance.

Laser radars (lidars) are recognized to be a reliable and powerful instrument for investigating atmospheric objects and air parameters [7–9]. As compared to other measurement approaches, the lidar technique exhibits advantages such as possibilities for performing fast, highly sensitive and accurate monitoring of vast atmospheric domains with high spatial and temporal resolution. Lidar systems are mainly used to assess the vertical structure of the aerosol layers and determine the optical and microphysical properties of the vertical profiles of the aerosols. Scanning ground-based and airborne lidars are applied to produce threedimensional (3D) maps of earth's surface and man-made features [10], as well as for characterization of tropospheric wind profiles [11, 12] and temperature fields [13]. Along with the above applications, scanning elastic-scattering lidars are used to obtain maps of important atmospheric pollutants, particularly, of near-surface aerosol fields [14–17]. The aerosol lidar mapping represents a fast and effective approach to detect polluting aerosol loads over broad areas, as well as to characterize them in terms of local density, spatial distribution, and temporal dynamics [18–20].

In this chapter, we present experimental results on lidar mapping of near-surface atmospheric aerosol fields over the city of Sofia, its suburbs and surrounding villages, obtained during an extensive 7-month experimental campaign in 2015 [19]. It was carried out in the framework of a common project with Sofia Municipality aimed to help the local authorities to improve the regional air-quality monitoring. Possibilities are also discussed to incorporate lidar mapping technologies synergistically into municipal air-quality monitoring systems. Aerosol lidar maps are considered to become basic components of such monitoring systems. Their advantages result from the high efficiency of the laser light interaction with the atmospheric particles, thus, providing better visualization of atmospheric motions in comparison with other remote sensing techniques, such as the microwave or acoustic probing.

The analysis of the lidar mapping experiments performed was focused on the following issues:


iii. Estimating effects of the city structure and terrain topography on the aerosol distribution obtained.

The chapter is organized as follows: In Section 2, we describe the experimental instrumentation, data processing/visualization approaches, and the area investigated. Then, in Section 3, series of experimental data on lidar aerosol mapping over the Sofia region are presented. Results are reported and analyzed of horizontal and vertical lidar scanning of the aerosol density distribution, as well as its temporal dynamics. Special attention is paid in Section 4 to the synergistic effects of mutual use of lidar aerosol mapping and in-situ measurement sites of the air pollution. The main results and conclusions are summarized in Section 5.
