Impact of the Planetary Boundary Layer Height on the Surface Aerosol Optical and Microphysical Properties

Salvatore Romano,Maria Rita Perrone

doi:10.1051/epjconf/202023702015

Abstract

Lidar, nephelometer, and aethalometer measurements at the surface, co-located in time and space with Particulate Matter (PM) measurements, have been performed to investigate the impact of the daily evolution of the Planetary Boundary Layer (PBL) height on the aerosol optical and microphysical properties. Measurements were performed at a coastal site of southeastern Italy characterized by a shallow (<1000 m) PBL height. The Standard Deviation technique applied to the vertical profiles of both the lidar range corrected signal (RCS) and the linear volume depolarization ratio (δr) has been used to determine the daily evolution of the PBL height and highlight benefits and limits of using RCS and δr vertical profiles. It is shown that the PBL height, which drives the particle dispersion at the surface, significantly affects the optical and microphysical properties of the surface particles since the particle dispersion varies with their size and, consequently, the mean optical and microphysical properties of the surface particles are affected. The impact of meteorological conditions on the daily trend of the PBL height and the surface particle properties has also been highlighted.

Highlights

The characterization of the Planetary Boundary Layer (PBL) is of primary importance for climate, meteorological forecasts, pollutant dispersion, and air quality studies
The PBL tends to be lower in depth at night, while during the day it tends to have a higher depth because of the wind speed and the air thickness, which vary as a function of temperature
The Standard Deviation (SD) technique applied to the vertical profiles of the lidar range corrected signal (RCS) and the linear volume depolarization ratio ( r) has been used to determine the daily evolution of the PBL height and investigate its relationship with local meteorological parameters and aerosol properties at the surface

Summary

INTRODUCTION

The characterization of the Planetary Boundary Layer (PBL) is of primary importance for climate, meteorological forecasts, pollutant dispersion, and air quality studies. The PBL tends to be lower in depth at night, while during the day it tends to have a higher depth because of the wind speed and the air thickness, which vary as a function of temperature. The PBL height can be estimated from measurements of the mechanical turbulence, the temperature enabling convection, or the concentration of the atmospheric constituents. Several techniques have been applied to trace the daily trend of the PBL height [3]. The Standard Deviation (SD) technique applied to the vertical profiles of the lidar range corrected signal (RCS) and the linear volume depolarization ratio ( r) has been used to determine the daily evolution of the PBL height and investigate its relationship with local meteorological parameters and aerosol properties at the surface. Main results will be presented and discussed by means of case studies

Site description and UNILE lidar system

PBL height identification

RESULTS

PBL heights and surface aerosol optical and microphysical properties