8 research outputs found
A thermodynamic description for the hygroscopic growth of atmospheric aerosol particles
The phase state of atmospheric particulate is important to atmospheric
processes, and aerosol radiative forcing remains a large uncertainty in
climate predictions. That said, precise atmospheric phase behavior is
difficult to quantify and observations have shown that precondensation of
water below predicted saturation values can occur. We propose a revised
approach to understanding the transition from solid soluble particles to
liquid droplets, typically described as cloud condensation nucleation – a
process that is traditionally captured by Köhler theory, which describes
a modified equilibrium saturation vapor pressure due to (i) mixing entropy
(Raoult's law) and (ii) droplet geometry (Kelvin effect). Given that
observations of precondensation are not predicted by Köhler theory, we
devise a more complete model that includes interfacial forces giving rise to
predeliquescence, i.e., the formation of a brine layer wetting a salt
particle at relative humidities well below the deliquescence point.</p
Development and characterization of the Portable Ice Nucleation Chamber 2 (PINCii)
The Portable Ice Nucleation Chamber 2 (PINCii) is a newly developed continuous flow diffusion chamber (CFDC) for measuring ice nucleating particles (INPs). PINCii is a vertically oriented parallel-plate CFDC that has been engineered to improve upon the limitations of previous generations of CFDCs. This work presents a detailed description of the PINCii instrument and the upgrades that make it unique compared with other operational CFDCs.
The PINCii design offers several possibilities for improved INP measurements. Notably, a specific icing procedure results in low background particle counts, which demonstrates the potential for PINCii to measure INPs at low concentrations (<10 L−1). High-spatial-resolution wall-temperature mapping enables the identification of temperature inhomogeneities on the chamber walls. This feature is used to introduce and discuss a new method for analyzing CFDC data based on the most extreme lamina conditions present within the chamber, which represent conditions most likely to trigger ice nucleation. A temperature gradient can be maintained throughout the evaporation section in addition to the main chamber, which enables PINCii to be used to study droplet activation processes or to extend ice crystal growth.
A series of both liquid droplet activation and ice nucleation experiments were conducted at temperature and saturation conditions that span the spectrum of PINCii's operational conditions (-50≤ temperature ≤-15 ∘C and 100 ≤ relative humidity with respect to ice ≤160 %) to demonstrate the instrument's capabilities.
In addition, typical sources of uncertainty in CFDCs, including particle background, particle loss, and variations in aerosol lamina temperature and relative humidity, are quantified and discussed for PINCii.</p
Measurement report: Introduction to the HyICE-2018 campaign for measurements of ice-nucleating particles and instrument inter-comparison in the Hyytiälä boreal forest
The formation of ice particles in Earth's atmosphere strongly influences the dynamics and optical properties of clouds and their impacts on the climate system. Ice formation in clouds is often triggered heterogeneously by ice-nucleating particles (INPs) that represent a very low number of particles in the atmosphere. To date, many sources of INPs, such as mineral and soil dust, have been investigated and identified in the low and mid latitudes. Although less is known about the sources of ice nucleation at high latitudes, efforts have been made to identify the sources of INPs in the Arctic and boreal environments. In this study, we investigate the INP emission potential from high-latitude boreal forests in the mixed-phase cloud regime. We introduce the HyICE-2018 measurement campaign conducted in the boreal forest of Hyytiälä, Finland, between February and June 2018. The campaign utilized the infrastructure of the Station for Measuring Ecosystem-Atmosphere Relations (SMEAR) II, with additional INP instruments, including the Portable Ice Nucleation Chamber I and II (PINC and PINCii), the SPectrometer for Ice Nuclei (SPIN), the Portable Ice Nucleation Experiment (PINE), the Ice Nucleation SpEctrometer of the Karlsruhe Institute of Technology (INSEKT) and the Microlitre Nucleation by Immersed Particle Instrument (µL-NIPI), used to quantify the INP concentrations and sources in the boreal environment. In this contribution, we describe the measurement infrastructure and operating procedures during HyICE-2018, and we report results from specific time periods where INP instruments were run in parallel for inter-comparison purposes. Our results show that the suite of instruments deployed during HyICE-2018 reports consistent results and therefore lays the foundation for forthcoming results to be considered holistically. In addition, we compare measured INP concentrations to INP parameterizations, and we observe good agreement with the Tobo et al. (2013) parameterization developed from measurements conducted in a ponderosa pine forest ecosystem in Colorado, USA
Interactions between the atmosphere, cryosphere, and ecosystems at northern high latitudes
The Nordic Centre of Excellence CRAICC (Cryosphere–Atmosphere Interactions
in a Changing Arctic Climate), funded by NordForsk in the years 2011–2016,
is the largest joint Nordic research and innovation initiative to date,
aiming to strengthen research and innovation regarding climate change issues
in the Nordic region. CRAICC gathered more than 100 scientists from all
Nordic countries in a virtual centre with the objectives of identifying and
quantifying the major processes controlling Arctic warming and related feedback
mechanisms, outlining strategies to mitigate Arctic warming, and developing
Nordic Earth system modelling with a focus on short-lived climate
forcers (SLCFs), including natural and anthropogenic aerosols.
The outcome of CRAICC is reflected in more than 150 peer-reviewed scientific
publications, most of which are in the CRAICC special issue of the journal
Atmospheric Chemistry and Physics. This paper presents an overview
of the main scientific topics investigated in the centre and provides the
reader with a state-of-the-art comprehensive summary of what has been achieved in
CRAICC with links to the particular publications for further detail. Faced
with a vast amount of scientific discovery, we do not claim to completely
summarize the results from CRAICC within this paper, but rather
concentrate here on the main results which are related to feedback loops in
climate change–cryosphere interactions that affect Arctic amplification.</p
Datasets to: Measurement report: Introduction to the HyICE-2018 campaign for the measurements of ice nucleating particles in the boreal forest of Hyytiälä
<p>This repository contains the datasets used in the study 'Measurement report: Introduction to the HyICE-2018 campaign for the measurements of ice nucleating particles in the boreal forest of Hyytiälä'. Detailed information and technical aspects of the data can be found in the publication.</p>
<p>Update (version 2 - January 2024): The repository was updated and now contains the complete HyICE-2018 datasets for the instruments uL-NIPI and PINE. </p>
<p> </p>
Interactions between the atmosphere, cryosphere, and ecosystems at northern high latitudes
The Nordic Centre of Excellence CRAICC (Cryosphere-Atmosphere Interactions in a Changing Arctic Climate), funded by NordForsk in the years 2011-2016, is the largest joint Nordic research and innovation initiative to date, aiming to strengthen research and innovation regarding climate change issues in the Nordic region. CRAICC gathered more than 100 scientists from all Nordic countries in a virtual centre with the objectives of identifying and quantifying the major processes controlling Arctic warming and related feedback mechanisms, outlining strategies to mitigate Arctic warming, and developing Nordic Earth system modelling with a focus on short-lived climate forcers (SLCFs), including natural and anthropogenic aerosols. The outcome of CRAICC is reflected in more than 150 peer-reviewed scientific publications, most of which are in the CRAICC special issue of the journal Atmospheric Chemistry and Physics. This paper presents an overview of the main scientific topics investigated in the centre and provides the reader with a state-of-the-art comprehensive summary of what has been achieved in CRAICC with links to the particular publications for further detail. Faced with a vast amount of scientific discovery, we do not claim to completely summarize the results from CRAICC within this paper, but rather concentrate here on the main results which are related to feedback loops in climate change-cryosphere interactions that affect Arctic amplification