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Assessing the aerosol radiative impact employing advanced methods to reduce uncertainties in the aerosol optical properties

Periodic Reporting for period 1 - REDRAF (Assessing the aerosol radiative impact employing advanced methods to reduce uncertainties in the aerosol optical properties)

Reporting period: 2016-10-01 to 2018-09-30

Understanding how anthropogenic aerosols impact the Earth’s climate system is a daunting challenge. According to the recently published report of the Intergovernmental Panel on Climate Change , aerosols result in a net cooling of the Earth’s climate by an amount that remains difficult to quantify accurately through their interaction with radiation and clouds, and which could be comparable in magnitude to the net warming effect of greenhouse gases. Not only does hydration cause an increase in size, but it also alters the complex refractive index (RI) of the particle ; Thus, quantifying the relationships of chemical composition, relative humidity (RH) and particle phase with complex RI is critical for predicting the radiative forcing of aerosol and in interpreting atmospheric measurements. Using a new technique to accurately determine the extinction cross-sections of single particles developed in the Bristol laboratory, we provided a rigorous assessment of treatments used to characterise the optical properties of aerosol. This work will also provide crucial information to improve our understanding of field and remote sensing instruments.
We have prepared and assayed different types of chemical compounds into the lab as established in the proposal and developed new technicals to manipulate and levitate single aerosol particles.
Two techniques were used to manipulate individual particles: The first technic (Bessel beam (BB)) was used to trap optically weakly absorbing particles. The second technnic (Lineal electrodynamic quadrupole) was developed and implemented during workpack 2. As result of this work, we have provided a precise data set of refractive indices for nonabsorbing aerosol. We demonstrated that it is possible to provide more accurate Radiative Forcing Efficiency (RFE) values using refined optical properties from BB-CRDS measurements.

As for the experienced researcher training objectives, they were as follows:

1 Provide a supportive environment for knowledge-exchange in the multidisciplinary and intersectorial field of aerosol single levitated particles.
2 Establish a tailored mentoring and training plan for career development in both academia and industry.

Work carried out during the fellowship towards the achievement of each listed objective: a training plan for career development was establish as the beginning of the fellowship. Dr. Antonio Valenzuela Gutierrez has improved his research skills by the completion of research activities.

1.2 Explanation of the work carried per WP

WP1: For the retrieval of accurate measurements of the real part of refractive index (RI) we examined RH and wavelength dependencies for scattering aerosol of a range of compositions. These data provided sufficient resolution to benchmark mixing rules. From the composition dependence, the pure component RIs were used to refine predictive tools for RIs. To achieve these goals single particle CRD measurements of light extinction by complex compositions as a function of RH were made with high accuracy.

WP2: This Workpack was focused to achive three objectives:
-Initial Benchmarking of the New Instrument Development for Absorbing Aerosol Measurements.
-Establishing the Accuracy of Imaginary Refractive Index Measurements.
-Examining the Optical Properties of Mixed-Component Aerosol and the Influence of Chemical Aging of Organic Aerosol on Light Absorption.

The list of comunication and dissemination activities are as follows:
1. Publications:
a. Valenzuela, A., Reid, J. P., Bzdek, B. R., &Orr-Ewing, A. J. (2018). Accuracy required in measurements of refractive index and hygroscopic response to reduce uncertainties in estimates of aerosol radiative forcing efficiency. Journal of Geophysical Research: Atmospheres, 123.
b. Second publication almost prepared for submission to journal.
c. Third still is in preparation.

2. Conferences:
a. Talk by Dr. Antonio Valenzuela Gutierrez at the 36th American Association for
Aerosol Research (AAAR) in Raleigh, North Caroline, USA, 2017.
b. Poster by Dr. Antonio Valenzuela Gutierrez at the 10th International Aerosol
Conference (IAC) in St. Louis, Missouri, USA, 2018.
3. Outreach/public engagement activities:
a. Bristol Bright Night, September 2017 (the H2020 Researcher’s Night).
b. Open Doors activities organized for secondary students in the University of
c. Seminars were regularly presented to the Bristol aerosol research centre (one each two months) as well as to the Bristol University community in general.
d. Regular meeting (one each two weeks) were held with the research team to
communicate results and the progress of the experiments.
e. Frequently companies visited our laboratory and experimental demonstrations (dissemination activities) were undertaken with the objective of exporting the technology and knowledge to the industry.
f. I supervised a postdoctoral visitor from Shanghai University of
Electric Power (Dr. Fenghong Chu) and a PhD student (Rose E. Willoughby) from
University of Bristol.
g. A webpage was prepared to show results of the REDRAF project
1.1. Impact on science and society: A quantitative understanding of the fundamental chemistry governing atmospheric phenomena are provided as results of this Project which may be used as inputs in models and also serves to verify and explain unusual field observations. The well-rounded, diverse set of skills Dr. Valenzuela have developed during this fellowship enable him become as a faculty member at a research university to devise and carry out innovative experiments to understand the fundamental chemistry underlying key problems in the field of atmospheric chemistry. Additionally, the developed skill set are transferable to other systems where particulate matter is important but not as well understood, such as the release of engineered nanomaterial to the environment. As a result of the postdoctoral experience gained on this fellowship, Dr. Valenzuela improved significantly his competences, enabling him to develop an innovative and relevant research program focused on understanding the fundamental chemistry of important environmental problems using several orthogonal approaches. The results of the postdoctoral research have important societal impacts, as this work permit more precise determination of aerosol effects on climate.

1.2. Impact on the experienced research career: this project has definitely increased the skills of Dr. Antonio Valenzuela Gutierrez to pursue a career in advanced research. He has acquired new knowledge and laboratory skills on a cutting-edge field of research and has allowed his to publish a paper in a top ranked journal. He has benefited from mobility to a foreign country and from the environment of the international group of Prof. Jonathan Reid and have met young researchers from all over the world. By doing so, he has expanded his network of future collaborators. Finally, the activities listed in last sections have been very useful for the development of his career. Indeed, he has already got a position in the group of Prof. Lucas Alados-Arboledas at University of Granada (Spain).