Aerosols and Climate

Aerosols and Climate
Copyright
Symbols
Contributors
Acknowledgments
Acronyms and abbreviations
Introduction
	What is aerosol and why is it important for climate?
	Aims and scope of the book
	Terminology, symbols, and units
	References
Aerosol in the climate system
	The historical development of our understanding of aerosol effects on climate
	Evidence for the effects of aerosol on climate
	Energy balance of the climate system
		Energy flows and the effects of aerosol
		Perturbation of energy flows
		Radiative forcing and subsequent atmospheric adjustments
		Radiative forcing agents
		Radiative forcing and climate response
	Aerosol radiative forcing
		Effects of aerosol on atmospheric radiation
		Definition of aerosol radiative forcing and its components
		The magnitude and distribution of aerosol radiative forcing
			The magnitude of aerosol radiative forcing
			The distribution of aerosol radiative forcing
	Climate response to changes in aerosol
		Aerosol forcing efficacy
		Spatial patterns of climate response
		Effects on the hydrological cycle and precipitation
	References
Aerosol in the Earth system
	Introduction to land and ocean productivity and biogeochemistry
		Land productivity and biogeochemistry
		Human impacts on land productivity and biogeochemistry
		Ocean productivity and biogeochemistry
		Controls on ocean productivity
		Human impacts on ocean productivity
	Aerosol effects on land and ocean biogeochemistry
		Aerosol deposition effects on terrestrial ecosystems
		Aerosol deposition effects on ocean ecosystems
		Aerosol deposition effects on freshwater aquatic ecosystems
		Effects of aerosol physical climate changes on land and ocean biogeochemistry
	Aerosol sources and deposition to the land and oceans
		Reactive nitrogen sources and deposition to the land and oceans
		Iron sources and deposition to the oceans
		Phosphorus sources and deposition to the land and ocean
		Other aerosols and their sources and deposition
	Effects of climate change and land use on natural aerosol emissions
		Dimethyl sulfide emissions under climate change (CLAW hypothesis)
		Desert dust changes across the anthropocene
		Wildfire and open fire changes across the anthropocene
		Soil nitrogen precursor emissions
		Biogenic volatile organic compounds and particulate emissions from vegetation
		Sea spray responses to climate change
	Modeling
		Status of aerosol-biogeochemistry-climate feedbacks in Earth system models
		Magnitude of aerosol biogeochemistry feedbacks on the carbon cycle
		Magnitude of climate-driven natural aerosol feedbacks
	Acknowledgment
	References
Global aerosol properties
	The aerosol particle size distribution
		Definition of particle size distributions
		Climate-relevant particles
	The global distribution of aerosol particles
		Aerosol transport pathways
		Spatial distribution of particle mass and number
		Particle chemical composition
		Spatial variations in the particle size distribution
	Small-scale aerosol variability
	Global distribution of aerosol precursor gases
	Aerosol in the preindustrial atmosphere
	References
Aerosol processes
	Particle sources, sinks, and lifetime
	In-air processes
		Emission and formation of aerosol precursor gases
			Gas-phase formation of precursor gases
			Formation of secondary material within particles
		New particle formation (nucleation)
		Particle growth by vapor condensation
		Coagulation
		Dissolution
		Water uptake (hygroscopicity)
		Particle ageing
		Ice-nucleating particles
		The behavior of charged particles
	Removal of particles by sedimentation and dry deposition
	In-cloud processes and aerosol wet removal
		Cloud droplet formation
		Cloud processing and aqueous-phase chemistry
		Vertical transport of gases and aerosol particles in clouds (venting)
		Wet removal of particles and gases
	Summary of timescales
	Knowledge gaps, future challenges, and research directions
	References
Aerosol-climate modeling
	Historical development of aerosol-climate modeling
		Pre-IPCC research contributions to aerosol-climate modeling
		Modeling for climate assessments: The IPCC period
	The range of models used in aerosol-climate research
	The anatomy of an atmospheric model
		Processes and parameterizations
		Parameterization essentials
		The concept of splitting to make calculations tractable and efficient
	Representation of clouds and precipitation
		Clouds as subgrid components of atmospheric models
		Representations of cloud particles
		Warm cloud bulk microphysics
		Microphysical extensions for ice treatment
	Representation of aerosol
		The aerosol particle size distribution
		Aerosol microphysical processes
	Representation of cloud-aerosol interactions
		Aerosol activation
		Aerosol removal and processing by clouds
		Ice- and mixed-phase cloud processes
	Representation of radiation interactions with clouds and aerosol
		Modeling considerations
	Model applications and evaluation
	Knowledge gaps, future challenges, and research directions
	References
Historical changes in aerosol
	Timescales
		Glacial-interglacial cycles
		From medieval to preindustrial times
		Preindustrial to present day
		Recent decades: The aerosol instrumental period
	Measurements of historical changes
		Ice core proxy records
			Formation of ice archives
			Sampling and analyzing ice archives
			Ice core chronologies
			Interpreting aerosol ice core records
		Peat bog, lake and ocean sediment proxy records
			Peat bog records
			Lake and ocean sediments
		Deposition and surface in situ aerosol measurements
		Visibility, radiation, and optical properties
		Other methods
	Historical changes in aerosol
		Volcanoes (1000-present day)
		Natural and anthropogenic aerosols over the industrial period (1750-present day)
		Surface radiation and visibility at the Earths surface (1940-present day)
		The aerosol instrumental record (1990-present-day)
	Modeling
		Set-up of historical model simulations
		Model-simulated radiative forcing
	Knowledge gaps, challenges, and research directions
	References
Aerosol and precursor gas emissions
	Developing emission inventories
	Emissions from industrial activity
		History of development
		Activity data
		Emission processes and emitted sizes of primary particles
		Emission factors
		Types of industrial sources
		Global industrial emission totals
	Emissions from the natural world
		Terrestrial sources
			Forests and vegetation
			Fires
			Arid environments: Dust from deserts and soils
			Volcanoes
		Marine sources
	Estimating past emissions
		Past industrial emissions
		Past natural emissions
	Future projections of emissions
		Economic and social scenarios
		Future projections of industrial emissions
		Future projections of natural emissions
	Modeling
		Assumptions
		Observational evaluation of emissions
	Knowledge gaps, future challenges, and research directions
	References
Measurements of ambient aerosol properties
	Measurement principles and instruments
		Units and particle diameter definitions
			Concentration units
			Definitions of particle diameter
			Size distributions
			Uncertainties, limits of detection, and time resolution
		Measuring the mass, number, and size of particles
			Gravimetric and equivalents
			Optical particle detection
			Condensation particle counters
			Particle size classifiers
		Measuring chemical composition
			Soluble ions
			Mineral dust
			Carbonaceous components
			Bio-particles
			Aerosol mass spectrometry
		Measuring new particle formation
		Measuring aerosol particle optical properties
		Measuring water interactions
	Conducting ambient measurements
		Sampling points and inlets
		Sampling lines and losses
		Measurement platforms
	Data from in situ measurements
		Processing, file formats, and metadata
		Aerosol databases
			GAW World Data Centre for Aerosols
			NOAA ESRL Federated Aerosol Network
			IMPROVE
			EMEP
			ACTRIS
			IAGOS
			GASSP
	Modeling
		Sources of error when comparing models and measurements
			Sub-grid-scale variability
			Measurement data sparsity in space and time
		Case studies
			Evaluation of global simulations of CCN and implications for cloud droplet formation (Fanourgakis et al. 2019)
			Aerosol mass spectrometer constraint on the global secondary organic aerosol budget (Spracklen et al., 2011)
			In situ constraints on the vertical distribution of global aerosol (Watson-Parris et al., 2019)
			The vertical profile of organic aerosol (Heald et al., 2011)
	References
Remote sensing measurements of aerosol properties
	Introduction to ultraviolet, visible, and near-infrared aerosol measurements from satellite
	Historical development of space-based aerosol remote sensing
		Early history
		The 1990s
		The EOS era
	Uses, strengths, and limitations of space-based aerosol remote sensing
		The uses of space-based aerosol remote sensing
		What remote sensing can and cannot tell us about aerosol
		Spatial and temporal coverage: Orbits and swaths
	Retrieval techniques
		Broad-swath, VNIR imager aerosol retrievals
		Visible-near-infrared (VNIR) multi-angle imager aerosol retrievals
		VNIR limb sounding aerosol retrievals
		UV imager aerosol retrievals
		Thermal infrared (TIR) sounder aerosol retrievals
		Active sensor aerosol retrievals
		Optimal estimation aerosol retrievals
	Remote sensing product uncertainty estimates and validation
		Statistical and case-study validation approaches
		Formal uncertainty estimates
	Modeling
		Remote sensing information commonly used to constrain models
		Challenges with comparing model output to remote sensing products
		Remote sensing in reanalyses
	References
Aerosol-radiation interactions
	Fundamental aspects of aerosol interactions with radiation
		Radiation
		Scattering
			Scattering regimes
			Scattering cross section and efficiency factor
			Phase function, asymmetry factor, and upscatter fraction
		Absorption
			Absorption cross section and efficiency factor
		Extinction
			Optical depth
			Single-scattering albedo
		Emission
		Aerosol and radiative transfer
	Factors determining the radiative effect of aerosol-radiation interactions
		Optical properties of aerosol particle types
		Solar zenith angle
		Underlying surfaces
		Influence of clouds
		Atmospheric temperature and humidity profiles
		Rapid adjustments to radiative effects
	Radiative effect of aerosol-radiation interactions
		Radiative effect efficiency of aerosol types
		Aerosol radiative effect in cloud-free conditions
		Aerosol radiative effect in cloudy conditions
		Aerosol-radiative effect in all-sky conditions
	Radiative forcing and effective radiative forcing of aerosol-radiation interactions
		Simplified expressions for radiative forcing
		Industrial-period changes in aerosol radiative properties
		Industrial-period aerosol radiative forcing
		Effective radiative forcing
	Uncertainty in aerosol-radiation interactions
		Aerosol radiative effect
		Aerosol radiative forcing
	Modeling
		Dependence on aerosol representations
		Dependence on approximations used in radiative transfer
		Model evaluation
	References
Aerosol-cloud interactions in liquid clouds
	Fundamental aspects of clouds and radiation
		The global distribution and bulk properties of clouds
			Cloud regimes
			Cloud bulk properties
		Effect of clouds on solar radiation
			Cloud reflectivity
			The dependence of solar radiation on cloud properties
			Planetary albedo
		Effect of clouds on terrestrial radiation
			The dependence of longwave radiation on cloud properties
		Cloud adjustments
	Fundamental aspects of aerosol interactions with clouds
		Cloud sources
			Turbulence, vertical motion, and adiabatic cooling
			Droplet activation
			Condensational growth and supersaturation
		Cloud sinks
			Precipitation formation via warm-rain processes
			Cloud evaporation
	Observations of aerosol-cloud interactions
		In situ observations of cloud properties
		Remote sensing of cloud properties
		Challenges in observing aerosol-cloud interactions
		Determining causality
	Assessments of radiative forcing
		Approaches for quantifying radiative forcing
		Quantifying the anthropogenic aerosol perturbation
		Radiative forcing, DeltaFaci
		Adjustments and effective radiative forcing, DeltaFacieff
		Overall assessment
	Modeling
		Clouds
			Cloud fraction and condensation
			Bulk and spectral microphysical schemes
		Aerosol-cloud interactions
			Droplet activation
			Precipitation and evaporation processes
		Model evaluation
	Research directions
	References
Atmospheric and oceanic dynamical responses to changes in aerosol
	Fundamental aspects of how aerosol affects climate dynamics
		Aerosol radiative forcing
		Interactions between different regions and timescales
	Responses of global mean temperature and precipitation
	Atmospheric responses on regional scales
		Tropics
			Global monsoon
			Asian monsoons
			Africa: Sahel drought and recovery
			Australia
			Tropical storms
		Mid-high latitudes
	Oceanic responses
		Atlantic: Atlantic multi-decadal variability and Atlantic meridional overturning circulation
		Pacific: Pacific decadal oscillation
		Tropical Pacific: El Niño Southern Oscillation
		Indian Ocean
	Modeling
	Knowledge gaps, future challenges, and research directions
	Acknowledgments
	References
Aerosol interactions with deep convective clouds
	Fundamental aspects of deep convective clouds
		Deep convective cloud dynamics
			Convective environment, buoyancy, and vertical motions
			Entrainment and detrainment
			Pressure perturbation fields
		Deep convective cloud microphysics
			Warm-phase microphysics
			Mixed-phase and ice-phase microphysics
	Aerosol effects on deep convective clouds
		Effects on cloud microphysics
		Effects on cloud dynamics
		Effects on precipitation
		Effects on cloud macrophysical properties and radiation
	Aerosol effects on severe storms
		Effects on tropical cyclones and mid-latitude cyclones
		Effects on mesoscale convective systems (MCSs)
		Effects on hail and tornadoes
		Effects on lightning
	Effects of deep convective clouds on aerosol particles and precursor gases
		Vertical transport and scavenging
		Cloud processing and aerosol regeneration
	Modeling
		Modeling aerosol interactions with deep convection at cloud-resolving scales
			Features of models at cloud-resolving scales
			Bulk and bin microphysics schemes
			Significant findings
		Modeling aerosol interactions with deep convection using coarse model grids
			Features of coarse-resolution models
			Significant findings
	Knowledge gaps, future challenges, and research directions
		Knowledge gaps and challenges
		Research directions
	Acknowledgments
	References
Ice-nucleating particles and their effects on clouds and radiation
	The role of heterogeneous ice formation in defining cloud microphysics and radiative properties
		Shallow mixed-phase clouds
		Convective clouds
		Upper tropospheric ice clouds that form in situ
	Role of ice-nucleating particles in cloud feedbacks and climate sensitivity
		Shallow mixed-phase cloud feedbacks
		Deep convection and anvil cirrus cloud feedbacks
		In situ cirrus cloud feedbacks
	Our physical understanding of heterogeneous ice nucleation
		The stochastic nature of nucleation
		Site-specific nucleation
		Active site requirements in the mixed-phase versus cirrus regimes
	The different types of ice-nucleating particles
		INP types important in mixed-phase clouds
		INP types important for in situ cirrus clouds
	Modeling
		Modeling ice-nucleating particles
			Heterogeneous nucleation in mixed-phase clouds
			Ice nucleation in cirrus
		Global model simulations of INP effects on mixed-phase clouds
		Global model simulations of INP effects on cirrus
		Cloud-resolving simulations of INP effects
	Knowledge gaps, future challenges, and research directions
	Acknowledgments
	References
Aerosol processes in high-latitude environments and the effects on climate
	Climatic features of the high-latitude regions
		Physical characteristics of high-latitude environments
		Atmospheric features of high-latitude environments
			The mean general circulation
			The Arctic dome
			Clouds
	High-latitude aerosol sources and processes
		High-latitude aerosol emissions
			Arctic
			Antarctica
		Long-range transport of aerosol to high latitudes
			Arctic
			Antarctica
		Aerosol processes at high latitudes
			New particle formation, growth, and secondary aerosol components
			Chemical aging and cloud processing
			Aerosol deposition processes
	High-latitude aerosol properties and trends
		The availability of measurements to define aerosol properties
		Aerosol microphysical and chemical properties at the surface-Seasonal cycles
			Arctic
			Antarctic
		Vertical profile of aerosol properties
			Arctic
			Antarctica
		Decadal aerosol trends at high latitudes
			Arctic
			Antarctica
	Aerosol effects on the climate of polar and subpolar regions
		Light-absorbing particles on ice and snow
		Local atmospheric aerosol-radiation interactions
		Local aerosol-cloud interactions
	Modeling
		Remote aerosol effects
		Local aerosol emissions
		Long-distance transport of aerosol
		Local aerosol-radiation interactions
		Local aerosol-cloud interactions
	Knowledge gaps, future challenges, and research directions
	References
Volcanic emissions, aerosol processes, and climatic effects
	Volcanic gas and particle emissions
		Passive volcanic emissions
		Eruptive volcanic emissions
	Volcanic effects on climate
		Volcanic aerosol processes, properties, and mechanisms
			Aerosol processes and distribution
			Aerosol optical depth
			Radiative effects and forcing
			Climatic response
		Forensic volcanology: Records of eruptions and their climatic effects
			Eruption chronologies: When, where, and how big
			Records of the climatic effects of volcanic eruptions
	Modeling
		Model simulations of volcanic effects on climate
		Model evaluation and confidence in estimated radiative forcings and climate responses
	Knowledge gaps, future challenges, and research directions
	References
Climate engineering
	Background
	Stratospheric aerosol climate engineering
		Natural stratospheric aerosol processes
		Stratospheric aerosol radiative properties
		The mechanisms of stratospheric aerosol climate engineering
		Sources of evidence
			Analogs
			Field and laboratory experiments
		Effects of stratospheric aerosol climate engineering on climate
		Uncertainties and open research questions
	Marine cloud brightening
		Natural marine aerosol-cloud processes
		The mechanisms of marine cloud brightening
		Sources of evidence
			Analogs
			Field experiments
		Effects of marine cloud brightening on climate
		Uncertainties and open research questions
	Practical aspects of climate engineering
	Modeling
		Representing climate engineering in models
		Different ways models can be used
	References
Aerosols in climate and air quality policy
	Introduction: Why we need to link climate and air quality policies
		Historical background
	Aerosol particles as pollutants
		Particulate matter (PM) air quality guidelines
		Effects on human health
		Effects on vegetation and crops: Acid deposition and eutrophication
		Measurements of PM
	Aerosol pollutants and climate change
		Comparing short-lived climate forcers (SLCFs) and CO2-Climate metrics
		Climate-air quality interaction
	Effects of policies related to air quality and climate
		Co-benefits and trade-offs
	Modeling
		Regional and global emission scenarios
		Integrated assessment models
	References
Index
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	F
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	H
	I
	J
	K
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	M
	N
	O
	P
	Q
	R
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	T
	U
	V
	W