Study of Droplet Activation in Thin Clouds Using Ground-Based Raman Lidar and Ancillary Remote Sensors

Marco Rosoldi,Gelsomina Pappalardo,Pilar Gumà Claramunt,Fabio Madonna,B Gross,F Moshary,M Arend

doi:10.1051/epjconf/201611916008

Marco Rosoldi, Gelsomina Pappalardo + Show 5 more

Open Access

https://doi.org/10.1051/epjconf/201611916008

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Abstract

A methodology for the study of cloud droplet activation based on the measurements performed with ground-based multi-wavelength Raman lidars and ancillary remote sensors collected at CNR-IMAA observatory, Potenza, South Italy, is presented. The study is focused on the observation of thin warm clouds. Thin clouds are often also optically thin: this allows the cloud top detection and the full profiling of cloud layers using ground-based Raman lidar. Moreover, broken clouds are inspected to take advantage of their discontinuous structure in order to study the variability of optical properties and water vapor content in the transition from cloudy regions to cloudless regions close to the cloud boundaries. A statistical study of this variability leads to identify threshold values for the optical properties, enabling the discrimination between clouds and cloudless regions. These values can be used to evaluate and improve parameterizations of droplet activation within numerical models. A statistical study of the co-located Doppler radar moments allows to retrieve droplet size and vertical velocities close to the cloud base. First evidences of a correlation between droplet vertical velocities measured at the cloud base and the aerosol effective radius observed in the cloud-free regions of the broken clouds are found.

Highlights

Studies on global climate change show that the effects of aerosol-cloud interactions (ACI) on the Earth’s climate and radiative balance, known as indirect aerosol effects, are the most uncertain among all the effects involving the atmospheric constituents and processes [1]
This work describes a methodology to improve the knowledge of the processes underlying the droplet activation. It is based on the observations performed with multi-wavelength (355, 532 and 1064 nm) Raman lidars, a Ka-band cloud Doppler radar and a microwave radiometer operative at CIAO (CNR-IMAA Atmospheric Observatory), located in Potenza, Southern Italy (40.60N, 15.72E, 760 m above sea level) and on the study of thin warm clouds
The discontinuous structure of broken clouds allows to study the variability of optical properties and water vapor content in the transition from cloudy regions to cloudless regions close to cloud boundaries

Summary

Introduction

Studies on global climate change show that the effects of aerosol-cloud interactions (ACI) on the Earth’s climate and radiative balance, known as indirect aerosol effects, are the most uncertain among all the effects involving the atmospheric constituents and processes [1]. This work describes a methodology to improve the knowledge of the processes underlying the droplet activation It is based on the observations performed with multi-wavelength (355, 532 and 1064 nm) Raman lidars, a Ka-band cloud Doppler radar and a microwave radiometer operative at CIAO (CNR-IMAA Atmospheric Observatory), located in Potenza, Southern Italy (40.60N, 15.72E, 760 m above sea level) and on the study of thin warm clouds. These clouds are low or midlevel super-cooled clouds characterized by a liquid water path (LWP) less than about 100 gm-2 [2]. The discontinuous structure of broken clouds allows to study the variability of optical properties and water vapor content in the transition from cloudy regions to cloudless regions close to cloud boundaries

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