6 July 2022
Science for Society
Studies of the Effect of Stratospheric Ozone Depletion on Tropospheric Oxidising Capacity over the Period 1979-2010 using the UKCA Chemistry-Climate Model
Paul Griffiths, NCAS Research Scientist, NCAS, Cambridge University
A grand challenge in the field of chemistry-climate modelling is to understand the connection between anthropogenic emissions, atmospheric composition and the radiative forcing of trace gases and aerosols.
We present an analysis of the trends in tropospheric oxidising capacity in the UM-UKCA from the recent forerunner to AerChemMIP, the Chemistry-Climate Model Intercomparison project, CCMI-1, focusing on the REFC1SD and REFC1 simulations over the recent historical period. We discuss these trends in terms of OH preconditions, such as photolysis rate and ozone concentration and the resulting impact on methane oxidation.
Fifteen years (2006-2021) of VOC Monitoring at the Cape Verde Atmospheric ObservatoryDr Shalini Punjabi, Research Technician, The University of York
Continuous and in situ hourly measurements of more than fifteen Volatile Organic Compounds (VOCs) have been made in the subtropical marine boundary layer at the Cape Verde Atmospheric Observatory (16° 51' N, 24° 52' W, 20m asl) in the east Atlantic Ocean. The observatory is operated as a global GAW station and analyses online air samples directly collected at the station tower. The observations began in October 2006 and continue today. Typical ambient mixing ratios range from as low a few parts per trillion for reactive VOCs such as butane and toluene to a few parts per billion for the longest-lived species ethane. A system and performance audit for VOCs was conducted at the station in December 2019 according to existing WMO/GAW guidelines and Standard Operating Procedures (SOPs) for the audit. The analysis of three travelling standards for whole air, NMHCs and oxygenates were compared with reference values and it showed excellent compatibility with the Data Quality Objectives (DQOs) for all reported compounds (GAW report No. 265).
Light alkanes have showed well-defined seasonal cycles with winter maximum and summer minimum, consistent with the seasonal variation of the OH radical. Detection limits for the Gas Chromatography – Flame Ionisation Detection (GC-FID) system are below 5 ppt for most VOCs except for ethane and propane (around 7 ppt). In addition to using a certified multicomponent laboratory standard, real air monthly target gas measurements are also used to support quality assurance. Oxygenates (methanol, acetone and acetaldehyde) and DMS quantitation is achieved by a permeation calibration set up. The system is being continuously improved to overcome the challenges associated with sampling and analysis of oxygenates and dimethyl sulphide. Measurement uncertainties are below 5% for ethane and propane. In addition to performing routine data and instrument checks, a set of additional post-analysis QA tools have been applied since 2012 to all VOC data before submission to data repositories.
Investigating the variation of benzene and 1,3-butadiene in the UK during 2000-2020
Rayne Holland, Postgraduate Research Student, University of Bristol
The concentrations of benzene and 1,3-butadiene in urban, suburban, and rural sites of the U.K. were investigated between 2000 and 2020 to assess the impact of pollution control strategies. Benzene concentrations in urban areas were found to be ~5-fold greater than those in rural areas whilst 1,3-butadiene concentrations were up to ~10-fold greater. The seasonal variation of pollutant concentration exhibited a maximum in the winter and a minimum in the summer with summer: winter ratios of 1:2.5 and 1:1.6 for benzene and 1,3-butadiene, respectively. Across the period investigated (2000-2020), the concentrations of benzene decreased by 85% and 1,3-butadiene concentrations by 91%. A notable difference could be seen between the two decades studied (2000-2010, 2010-2020) with a significantly greater drop evident in the first decade (76% and 75% for benzene and 1,3-butadiene, respectively) than in the second (32% and 64% for benzene and 1,3-butadiene, respectively). Whilst this indicates significant success of control strategies, it emphasizes the importance controlling previously unconsidered sources as they move towards a more dominant contribution to these pollutants. The health impact of these pollutants was considered utilizing recently developed cancer impact indices which allowed estimation of varying health impacts across different site types. Despite average rural concentrations of the pollutants meeting national air quality standards, lower limit cancer impact estimations of both benzene and 1,3-butadiene are notable. Considering upper limit cancer impact, an additional 3.0% and 4.0% of sites in the UK could surpass 800 annual cancer risks from benzene and 1,3-butadiene, respectively.
KlimaatHelpdesk.org: Connecting citizens with climate questions to experts with answers
Arthur Oldeman, PhD Candidate, Utrecht University
When faced with a question, scientists and scholars are trained to search academic and informal literature to find the answer. But where can the public find reliable answers to questions about the climate crisis? After all, the climate crisis is a topic about which our understanding rapidly evolves across a wide array of disciplines. The validity and reliability of offered information is difficult to assess for non-specialists, while scientific consensus is sometimes deliberately undermined in popular articles. Moreover, civil questions about the climate crisis can be very specific, pragmatic or locally applicable, so not all answers can be found on popular sources that commonly provide only the theoretical principles or general background. This raises the question how we can connect citizens with climate-related questions to understandable scientific expert knowledge.
KlimaatHelpdesk.org is meant to become the go-to place in the Netherlands for citizens with climate-related questions. It is a unique, independent, and accessible communications platform that connects the public with scientists and experts, run by a volunteer group of students and academics. People who ask a question on this platform will receive a peer-reviewed answer to their question from a network of affiliated scholars and experts. KlimaatHelpdesk archives the question and corresponding answer on the website and thereby provides an expanding, easily accessible source of reliable and evidence-based information. Since the official launch in November 2020, more than 250 enthusiastic experts have answered and/or reviewed over 130 questions in a variety of disciplines: from meteorology, oceanography and biology to psychology, law, and philosophy.
KlimaatHelpdesk also serves as a platform for students and young academics to get involved in science outreach and public engagement, and for scientists to explain their research to a targeted audience. While KlimaatHelpdesk is further expanding its reach in the Netherlands, we also work to make the platform portable to other countries and disciplines. We are eager and ready to share our gained experience with the wider Science Communication, Engagement & Outreach community.
Characteristic Wintertime Atmospheric Circulation in the Grenoble Basin and Impact on Air Pollution
Charles Chemel, Senior Research Scientist, NCAS
The Grenoble metropolitan area is located in a basin surrounded by the alpine massifs of Vercors, Chartreuse and Belledonne. This setting makes the Grenoble basin particularly subject to air pollution. The basin is found to present a characteristic local atmospheric circulation for a large-scale flow regime associated with wintertime anticyclonic blocking. A set of high-resolution numerical simulations of atmospheric dynamics in the basin for episodes representative of this regime is analysed to characterise the dispersion of tracers with emissions taken as those of fine particulate matter. Air pollution hot spots are identified and their locations are discussed in light of the underlying local atmospheric dynamics.
The Predictability and Representation of Indian Monsoon LowPpressure Systems in Subseasonal-to-Seasonal Prediction Models
Akshay Deoras, PhD Student, University of Reading
Indian monsoon low-pressure systems (LPSs) are cyclonic vortices that typically develop over the head of the Bay of Bengal and produce substantial summer monsoon precipitation over India. Despite their ability to trigger catastrophic floods in the Indian subcontinent, there has been insufficient exploration of their predictability and representation in models. In this study, we use a feature-tracking algorithm to identify LPSs in all ensemble members of eleven models of the Subseasonal-to-Seasonal (S2S) prediction project during a common reforecast period of June–September 1999–2010. Forecast verification statistics for LPSs are produced, and composite horizontal as well as vertical structures of many dynamic and thermodynamic fields are generated. The results are then verified against ERA-Interim and MERRA-2 reanalyses.
We find that S2S models simulate tracks and structure of LPSs reasonably well; however, they underestimate their frequency, and BoM, CMA and HMCR models have large biases in their simulation. Most S2S models correctly simulate the modulation of LPS genesis by the Madden-Julian Oscillation, and subseasonal probabilistic frequency predictions by BoM, CMA, CNRM and ECMWF models are the most accurate. We also find that large-scale conditions, such as the position of the tropical easterly jet and mid-tropospheric relative humidity, play a role in modulating LPS lifespan.
These results demonstrate the potential for S2S models at forecasting LPSs, envisaging improved disaster preparedness and water resources planning in the Indian subcontinent.
Seasonal Forecast Skill for the Southern Annular Mode
Amelia Adcroft, Student, University of Oxford
Seasonal forecasts successfully predict various characteristics of the atmosphere and oceans, but their predictive skill in the Southern Hemisphere (SH) has been studied in less detail than in the Northern Hemisphere. To help address this gap, we examine the skill of seasonal forecast models in predicting the Southern Annular Mode (SAM), the dominant mode of SH extratropical atmospheric variability. Using hindcasts from three seasonal forecasting models, initialised in November, we quantify the predictive skill of the models for austral summer, identify sources of this skill, and search for decadal variations in skill. During the period common to the three hindcasts, two models show statistically significant skill whilst the skill in the third does not rise to the level of significance. The primary source of SAM predictive skill is found to be a teleconnection with tropical Pacific sea surface temperatures, with additional possible sources of skill suggested in the best-performing model. The identification of the sources of present skill can contribute to improvements in future seasonal forecasting models.
Atmospheric Gravity Waves in Aeolus Wind Lidar Observations
Timothy Banyard, PhD Student, University of Bath
As the first Doppler wind lidar in space, ESA’s flagship Aeolus satellite provides us with a unique opportunity to study the propagation of gravity waves (GWs) from near the surface to the tropopause and UTLS. Existing space-based measurements of GWs in this altitude range are spatially limited and, where available, use temperature as a proxy for wind perturbations. Recent research confirms Aeolus’ ability to measure GWs, and so this and future spaceborne wind lidars have the potential to transform our understanding of these critically-important dynamical processes.
Here, we present results from a special campaign onboard Aeolus, involving a change to the satellite’s range-bin settings designed to allow better observations of orographic GWs over the Southern Andes during winter 2021. We expect to see GW wind structures extending down to near the wave sources, enabling detailed measurements of vertical and horizontal wavelength, pseudo-momentum flux and wave intermittency. Such parameters will feed into the next generation of numerical weather prediction and global circulation models, which will resolve waves at higher resolutions and employ more advanced parameterisation schemes.
Study on the Characteristics of Cold Clouds and Snow Particles in the Yeongdong Region of Korea
Yoo-Jun Kim, Senior Researcher / PhD, National Institute of Meteorological Sciences, Korea Meteorological Administration (KMA)
The Yeongdong region of Korea has sometimes meteorological disasters such as breakdown accidents due to heavy weight of accumulated snow, and traffic accidents due to slippery road condition in winter. Determining the occurrence and phase of precipitation is a major challenge in winter weather forecasting over the complex terrain. This study investigates the characteristics of cold clouds and snow particles in both the Yeongdong coastal and mountainous regions based on the integration of numerical modeling and intensive observations for a snowfall event that occurred on 29-30 January 2016. As a result, we found that rimed particles predominantly observed turned into dendrite particles in the latter period of the episode when the 850 hPa temperature decreased at the coastal site, whereas the snow particles at the mountainous site were largely needle or rimed needle. Rawinsonde sounding showed a well-defined, two-layered cloud structure along with distinctive wind-directional shear, and an inversion in the equivalent potential temperature above the low-level cloud layer. The first experiment with a decrease in low-level temperature showed that the upslope winds and vertical development of clouds were weakened compared to the control experiment. Secondly, the difference in precipitation between the single-layered experiment and control experiment was not significant to attribute it to the effect of the seeder-feeder mechanism. The precipitation in the last experiment by weakening wind directional shear was increased by 1.4 times greater than the control experiment significantly at the coastal site, with graupel particles accounting for the highest proportion (62%). The current results would improve snowfall forecasts in complicated geographical environments such as Yeongdong in terms of snow particle as well as snowfall amount in both time and space domains.
Extreme Dust Weather over East Asia: Insights from the CAMS reanalysis and high-resolution modeling
Dhirendra Kumar, Research Scientist, NCAS, University of Reading
Mineral dust is an important constituent of the total atmospheric aerosol load and impacts the earth system in different ways from regional to global scales. With frequent dust storms, East Asian deserts are one of the hotspots of mineral dust emission and impacts. We investigate the characteristics and key meteorological drivers of the extreme spring dust storms over East Asia using the ECMWF Copernicus Atmospheric Monitoring Service (CAMS) global reanalysis and high-resolution global climate model (GCM) simulations at 14 km horizontal resolution with parameterized and explicit convection. We identify the dust extremes based on the impact (in terms of peak Dust Aerosol Optical Depth at 550nm, DOD) over Beijing and Gobi as well as the extreme dust emission over the Gobi Desert. We find that extreme dust events in the CAMS affecting Beijing are predominantly driven by the surface north-westerlies associated with the eastward traveling mid-latitude cyclones (MLCs) traversing the Gobi region. Contrastingly, dust extremes affecting the Gobi region are dominated by southeasterlies accompanying a slow-moving low-pressure system pushing the emitted dust westwards. Using the extreme emission over the Gobi Desert as a metric, the modeled extremes agree well with the CAMS Beijing DOD extremes, especially in the parameterized convection simulation. Despite differences in the modeled emission, strengths of surface wind, the location, and track of MLCs associated with the dust extremes are well captured in this simulation. However, the explicit convection simulation fails to correctly resolve the location and track of the driving MLCs, and thus weaker dust extremes are noticed in them.
Gridded 1 km × 1 km emission inventory for paddy stubble burning emissions over north-west India constrained by measured emission factors of 77 VOCs and district-wise crop yield data
Paddy stubble burning is a major environmental issue that plagues the ambient air quality of the Indo-Gangetic Plain. Every year, during the post-monsoon season (October and November), approximately 17 million tons of paddy stubble are burnt openly in the fields of Punjab and Haryana. Over two months, this large-scale biomass burning results in persistent smog and severely perturbs the regional air quality. The emission of reactive gaseous pollutants like volatile organic compounds (VOCs) from this source drive the surface ozone and aerosol formation. However, there is a considerable knowledge gap regarding their identification, amounts and spatial distribution over North India. Widely used top-down global fire emission inventories like GFED, GFAS and FINN rely on the high-resolution MODIS and VIIRS satellite fire products. However, they are severely constrained by the missed fires, limited VOC speciation and uncertain biomass burnt calculations due to non-region-specific emission and land use parametrization factors. The current bottom-up emission estimates also have high uncertainties because of non-region-specific emission factors and burning practices. This work presents a new “hybrid” gridded emission inventory for paddy stubble burning over Punjab and Haryana in 2017 at 1 km × 1 km spatial resolution. First, the emission factors (EFs) of 77 VOCs were measured in smoke samples collected from the on-field paddy fires of Punjab. These were then combined with 1 km × 1 km stubble burning activity, constrained by annual crop production yields, regional rice cultivars, burning practices and satellite-detected fire radiative power. The results revealed that paddy stubble burning is a significant source of oxygenated VOCs like acetaldehyde (37.5±9.6 Ggy-1), 2-furaldehyde (37.1±12.5 Ggy-1), acetone (34.7±13.6 Ggy-1), and toxic VOCs like benzene (9.9±2.8 Ggy-1) and isocyanic acid (0.4±0.2 Ggy-1). These compounds are also significantly underestimated and unaccounted for by existing top-down and bottom-up emission inventories. Additionally, it was found that the emissions of NMVOC (346±65 Ggy-1), NOx (38±8 Ggy-1), NH3 (16±4 Ggy-1), PM2.5 (129±9 Ggy-1), GHG CO2 equivalents (22.1±3.7 Tgy-1) from paddy stubble were up to 20 times higher than the corresponding emissions from traffic and municipal waste burning over north-west India during October and November 2017. Mitigation of this source alone can yield massive air-quality climate co-benefits for more than 500 million people.
The NERC Field Spectroscopy Facility Spectral Atmospheric Suite (SAS) -- A portable trace gas and aerosol optical properties measurement network
Robbie Ramsay, Earth Observation Equipment Specialist, NERC Field Spectroscopy Facility
Ground based networks of trace gases (in particular, the greenhouses gases) are critical for the understanding of biosphere-atmosphere trace gas exchange, and when paired with satellite observations, provide critical validation for satellite trace gas measurements. When paired with concurrent and coincident measurements of aerosol optical properties and local meteorology, satellite retrievals are further enhanced.
However, there has previously existed a gap in the provision of such ground based networks, due to expense, infrastructure concerns, and the ability to provide autonomously acquired, high resolution data. This issue is exacerbated in areas of restricted or minimal site infrastructure, such as in city centres or remote site locations of interest e.g. peatlands, or tropical forests. To fill this gap, the NERC Field Spectroscopy Facility (FSF) has developed the Spectral Atmospheric Suite (SAS), a suite of high resolution, portable and autonomous spectroscopic instruments which can be deployed by FSF as a cluster network, available for research communities in the UK and internationally.
The SAS consists of three discrete instrument “nodes”, which can be deployed individually or as part of a network cluster. Each instrument node consists of a Fourier Transform Infrared (FTIR) spectrometer (the EM27/SUN (Bruker GmbH, Germany), spectral range: 5,000 – 14,500 cm-1), measuring the column abundances of CO2, CH4 and CO; a 2D MAX-DOAS (the 2D SkySpec (AirYX GmbH, Germany), spectral range: 300 – 565 nm), measuring the slant column densities of a range of trace gases including NO2 and SO2; an automatic weather station (Vaisala, Finland) measuring meteorological parameters required for the retrievals of GHGs and trace gases; and a sun-sky-lunar sunphotometer (CIMEL Electronic, France), measuring aerosol optical thickness. Combined, each node represents an autonomous “miniature supersite”, capable of providing long term measurements as a ground based validation site for satellite measurements of GHGs and other trace gases. Each node is portable and has a low spatial footprint, allowing for easy deployment in areas of minimal or restricted infrastructure, such as city centres or remote wetland regions.
We present here an overview of the NERC FSF Spectral Atmospheric Suite, a selection of data collected from the network as part of its current deployment with the University of Leicester’s London Carbon Emissions Experiment, and how it can be provided to UK and international researchers for future research.
First light from a new advanced aerosol lidar profiling system provided by AMOF
Hugo Ricketts, NCAS
A new lidar (LIght Detection And Ranging) System began operation in June 2022. The Cimel CE376-GPN lidar is designed to provide advanced vertical profiles of various aerosol parameters. By using two lasers at different wavelengths (green and infrared), it provides information on the size distribution of the aerosol in the atmosphere based on the amount of light returned to the lidar. Additionally, the lidar can distinguish between spherical and non-spherical particles using depolarisation, as non-spherical particles lead to changes in the polarisation of the laser light.
The new lidar system is currently being evaluated at the University of Manchester. After this evaluation period, it will be made available to the research community through the Atmospheric Measurement and Observation facility (AMOF).
New model experiments to explore climate stabilisation at various global warming levels
Andrea Dittus, NCAS
In recent years, there has been increasing interest in how possible future climates at different stabilised, policy relevant global warming levels above pre-industrial might look like. Modelling groups are designing novel climate model simulations to investigate these questions and help answer important questions on the linearity of future climate change across warming levels, tipping points, and climate extremes, among others.
Here, we present the results of six new "quasi-stable" climate model simulations with UKESM1.0 that have been run under constant forcings, branching-off from ScenarioMIP simulations of the same model. These simulations explore a range of global warming levels, from approximately 1.5 to 5°C above pre-industrial. In addition, they also explore the role of different balances of forcings for achieving the same target warming level, in particular different combinations of greenhouse gas concentrations and anthropogenic aerosols. In this presentation, we describe how the climate evolves in each of these simulations. We focus on two key aspects: 1) differences between a more stable climate vs. transient climate change at the same warming level and 2) importance of scenario differences, in particular differences in anthropogenic aerosol emissions at the same warming level.
Poster 15 - Poster Withdrawn
Linking Equatorial African Precipitation to Kelvin Wave Processes in the CP4-Africa Convection-Permitting Regional Climate Simulation
Godwin Ayesiga, Early Career Scientist, University of Reading & Uganda National Meteorological Authority
Observational studies have shown the link between Convectively Coupled Kelvin Waves (CCKWs) and eastward propagating rainfall anomalies. We explore the mechanisms in which CCKWs modulate the propagation of precipitation from west to east over Equatorial Africa. We examine a multi-year state-of-the-art Africa-wide climate simulation from a convection permitting model (CP4A) along with a parameterised global driving-model simulation (G25) and evaluate both against observations (TRMM) and ERA-Interim (ERA-I), with a focus on precipitation and Kelvin wave activity. We show that the two important related processes through which CCKWs influence the propagation of convection and precipitation from west to east across Equatorial Africa are: 1) low-level westerly anomalies that lead to increased low-level convergence, and 2) westerly moisture flux anomalies that amplify the lower-to-mid-tropospheric specific humidity.
Improving our Understanding of Orographic Rainfall Processes in India and their Impacts - Results from the WCSSP-India IMPROVE project
Andy Turner, Professor of Monsoon Systems, NCAS, University of Reading
Regional orography around India exerts a profound control on weather and climate, both in summer and winter as part of the diurnal cycle of convection, as well as in extreme events that lead to large infrastructure damage and loss of life. This poster summarizes the key results of the Indo-UK IMPROVE project (Indian Monsoon Precipitation over Orography: Verification and Enhancement of understanding) under the Newton Fund Weather and Climate Science for Services Partnership (WCSSP).
IMPROVE considers two focal regions. The Western Ghats intercept the monsoon flow across the Arabian Sea and receive some of the most frequent and heaviest summer rainfall, including being subject to extremes such as the 2018 Kerala floods. Meanwhile, the Himalayas play a vital role in separating dry midlatitude flows from tropical airmasses in summer, while suffering extremes in winter due to western disturbances - cyclonic storms propagating on the subtropical westerly jet.
We examine the impact of orography on the observed convective diurnal cycle and assess its simulation in models at a range of resolutions including convection-permitting scales. MetUM and WRF model experiments, in addition to DWR retrievals, are used to identify key mechanisms between forcing at the large scale from the BSISO and newly identified regimes of on- and offshore convection near the Western Ghats. An additional aspect to this work is consideration of a novel Froude number approach for understanding the convective regimes. Secondly, the role of orography in extreme events is considered, including its interactions with passing tropical depressions or western disturbances emanating from the midlatitudes. IMPROVE works towards a deeper understanding of orographic rainfall and its extremes over India and uncovering why such mechanisms may be poorly represented in models.
Adaptation and testing of the Air Pollution Assessment and Action manual for humanitarian settings
Sumaiya Noor, Researcher
The Rohingya influx in Cox’s Bazar has presented new challenges to air pollution. The addition of approximately one million new residents to the region have led to widespread clearcutting of forests for fuel and the burning of trash, including plastics and other inorganic waste. As a result, the ambient ai quality in the region is roughly twice as poor as the rest of Bangladesh and is creating a health crisis in an already complex humanitarian emergency. Levels of PM2.5 in Cox’s Bazar varies from 312.25 to 300.00 ug/m3 for PM2.3, for higher than WHO recommended levels. Ambient Air Pollution (AAP) is a health threat globally in humanitarian settings, and burning of solid waste and vegetation are major sources.
AAP and Household Air Pollution (HAP) have a wide range of health effects. Reduction in HAP has been demonstrated to improve asthma and other respiratory conditions in humanitarian settings. Beyond the respiratory tract, fine particular matter (PM2.5) can pass through the alveoli into the bloodstream, leading to effects in distant organs such as the brain and liver. AAP and HAP, through effects on the placenta, are major contributions to stillbirth and low birthweight. Effects on the pancreas are estimated to contribute to a large population of incident diabetes mellitus globally. While water-borne infections are often a focus in humanitarian settings, attention is also needed to reduce disease burden from AAP.
Recent Decadal Weakening of the Summer Eurasian Westerly Jet Attributable to Anthropogenic Aerosol Emissions
Buwen Dong, Principal Research Fellow, NCAS, University of Reading
The Eurasian subtropical westerly jet (ESWJ) is a major feature of the summertime atmospheric circulation in the Northern Hemisphere. Here, we demonstrate a robust weakening trend in the summer ESWJ over the last four decades, linked to significant impacts on extreme weather. Analysis of climate model simulations from the Coupled Model Intercomparison Project Phase 6 (CMIP6) suggests that anthropogenic aerosols were likely the primary driver of the weakening ESWJ. Warming over mid-high latitudes due to aerosol reductions in Europe, and cooling in the tropics and subtropics due to aerosol increases over South and East Asia acted to reduce the meridional temperature gradient at the surface and in the lower and middle troposphere, leading to reduced vertical shear of the zonal wind and a weaker ESWJ in the upper troposphere. If, as expected, Asian anthropogenic aerosol precursor emissions decline in future, our results imply a renewed strengthening of the summer ESWJ.
Counterfactual Weather Forecasts forAattribution and Projection of Extremes
Nicholas J. Leach, PhD Student, University of Oxford
The recent 2021 Pacific Northwest heatwave was a truly unprecedented extreme weather event, shattering previous temperature records. However, its unprecedented nature has made quantifying the influence of anthropogenic global warming on the heatwave using conventional approaches to attribution challenging due to deficiencies in the numerical dynamic or statistical models applied. Here we show, using counterfactual weather forecasts, that the heatwave was made at least 8 times more likely, and 1.3 °C more intense due to human influence on the climate. The value of using successful operational weather forecasts lies in their unequivocal ability to simulate the specific extreme event in question. Although here we use such forecasts for attribution of extreme weather events, such counterfactual forecasts have wide-ranging potential applications, especially for informing adaptation to climate change through projection of such events at specified global warming levels.
Experimental Study of Chinese Agricultural Residues Burning Emissions
Yanan Liu, PhD Student, King's College London
Although policy attempts to restrict agricultural residue burning, it appears to exist on a large scale in China, especially before sowing or after harvest. A large amount of smoke pollution is generated during these burning activities, which impacts atmospheric conditions. To accurately measure these atmospheric substances, we combined the in-suit and laboratory work to measure the gas mixing ratio and aerosol concentration from wheat, straw, corn, millet and soybean planted in China. Here we applied a multi-gas data logger to measure CO2 and CO concentrations in the field and simulate a similar burning scenario in the combustion chamber. In the lab, except for carbon-related gases, we measured the concentrations of NOx, NO, and NO2, PM2.5, and black carbon particulates with different moisture contents and burning methods. Our data showed the various emission factors for different agricultural residues. For example, we calculated the CO2 and CO emission factors for a millet bonfire under completely dry conditions (CO2:1631±30 g/kg; CO:129±19 g/kg), and for wheat in the same condition (CO2:1718±32 g/kg; CO:73±21 g/kg). The results also showed that the same agricultural residue with various moisture contents can have different emission factors. For example, we calculated the CO2 and CO emission factors for a straw bonfire under completely dry conditions (CO2:1690±10 g/kg; CO:91±7 g/kg), while for a straw bonfire with 20% moisture content (CO2:1657±44 g/kg; CO:112±28 g/kg). In addition, we also captured the whole burning process to know the flaming and smouldering phases. The study helped us understand the exact gaseous and aerosol compounds of smoke from different types of agricultural residues burning, which will better quantify their contribution to emission inventories.
Newly Built Combustion-Observation System for Biomass Burning Aerosols Using a Commercial Wood-Burning Stove Connected to the Existing Manchester Aerosol Chamber Facility
Sara Aisyah Syafira, PhD Student, University of Manchester, NCAS, University of York
Biomass burning aerosols, including those resulting from wildfires, are widely thought to significantly impact on air quality, health, and climate through both direct radiative effects and aerosol-cloud interactions. Therefore, their optical and physiochemical properties have received substantial recent attention. These properties can change with time as they age through exposure to light and existing oxidants. Some research has shown significant correlation between the changes of the properties and the initial gases emitted from the burning, which mostly depends on the fuel types and the burning conditions, e.g. flaming versus smouldering. Connection between a commercial wood-burning stove and the Manchester Aerosol Chamber (MAC) facility at University of Manchester enables the laboratory study of biomass burning aerosols with various type of fuel and various burning conditions, as indicated by their range in modified combustion efficiency (MCE) values. A range of instruments and tools connected to the MAC enable this newly constructed infrastructure to capture the real time observations of either dark or photo-aging effects on biomass burning particles across a range of MCE values. Relative humidity and oxidant conditions can be controlled during the aging experiments and both chemical to physical properties including hygroscopicity, CCN activity, and optical properties can be measured in real-time.
A Combined Modelling and Experimental Approach into Understanding the Effect of Changing Ozone Concentration on α/β-pinene Oxidation Products: a Box Model Study
Emilia Bushrod, PhD Candidate, University of Cambridge, British Antarctic Survey
The abundance of oxidants, such as ozone (O3) and the hydroxyl radical (OH), within the troposphere is termed; the oxidative capacity. Through control of the atmospheric lifetime of trace gases, the oxidative capacity of our atmosphere is partially responsible for global climate drive. An understanding of how the oxidative capacity of past atmospheres changed with differing climate conditions will allow predictions to be drawn as to how future atmospheres will react to changing climates. The aim of this project is to construct a combined modelling experimental approach to study the oxidative capacity of past atmospheres. Though the oxidants themselves are not preserved within ice cores, this project proposes that the interpretation of ratios between different terrestrially sourced secondary organic aerosol markers (SOA-markers), found in ice cores, will allow an understanding of the oxidative capacity of past atmospheres. The physical ratios of SOA-markers found in ice cores will be compared to the ratios of the same SOA-markers, studied through atmospheric box modelling.
The modelling study will involve observing the change in the SOA-marker ratio with varying oxidant (O3 and OH) exposure. As this is a novel method and the concentrations of SOA markers are likely to be greatest in northern ice cores, this project will focus on the northern hemisphere. The modelling data will be compared to the physical ratios found from northern ice cores (Mt. Elbrus and Svalbard) to establish the concentration of O3 and OH present in past atmospheres. The likely major emission source in this area is from the Boreal Forest. The biogenically emitted volatile organic compounds (BVOCs) of interest within this project are isoprene, α-pinene, and β-pinene. It is the oxidised products of these BVOCs that make up the SOA-markers of interest.
The Southern Ocean Clouds Project
Floortje van den Heuvel, Cloud Physicist, British Antarctic Survey
The Southern Ocean is an area where the biases in climate model representations of surface radiation and sea surface temperature are larger than anywhere else - and this has a fundamental impact on the ability of these models to predict global climate. It is thought that this is due to the poor representation of the mixed phase clouds (MPCs) which are typically found over these high latitudes. The aim of the Southern Ocean Clouds project (SOC) is to identify the compositions and sources of the aerosols that act as cloud forming nuclei, to improve understanding of aerosol and cloud microphysics as well as the representation of clouds in numerical models.
This year, as part of SOC, instrumentation has been installed at the Rothera research station in Antarctica to start making long-term measurements of the number, size and composition of aerosol as well as their cloud condensation and ice nucleating ability. We've also installed a LiDAR to measure cloud properties. An overview of the SOC project objectives, current and future activities as well as preliminary results will be presented.
Arctic Summertime Cyclones project and field campaign
John Methven, Professor
Arctic cyclones are the dominant type of hazardous weather system affecting the Arctic environment in summer. In late summer the marginal ice zone is extensive and wind forcing can move the ice readily; in turn, the dynamic sea ice distribution is expected to feedback on the developing weather systems. The interaction presents a major challenge to coupled forecasts of the Arctic environment from days out to a season ahead.
In summer 2022, in concert with ONR-THINICE, we aim to fly two research aircraft from Svalbard into Arctic cyclones passing over the marginal ice zone. We will measure the turbulent exchange fluxes, flying low above the interface between atmosphere and ice, at the same time as measuring the wind and cloud structure of the cyclones above and the properties of the ice below. Combining the observations with numerical modelling experiments using the Met Office NWP model, we aim to deduce the dominant physical processes acting and test theoretical mechanisms for the influence of sea ice on Arctic cyclone dynamics. Prior to the campaign, Met Office and ECMWF forecasts that are coupled, or uncoupled, with a dynamic sea ice distribution have been investigated for systematic differences in the representation of boundary layer and surface fluxes, composited relative to the warm and cold sectors of Arctic cyclones and conditional on the surface beneath (ice, ocean, land). These findings inform the flight plans for the field experiment and focus of the observations.
Understanding the Sulfur Cycle and MSA Formation over the Ocean
Lorrie S.D. Jacob, PhD Student, University of Cambridge
Dimethyl sulfide (DMS), which originates from phytoplankton, is the major natural source of sulfur compounds in the atmosphere. The oxidation products of DMS can form aerosols, which contribute to the formation of clouds, making them important for rain and the radiative balance of the planet. Additionally, due to DMS naturally occurring above oceans, an oxidation product of DMS, methanesulfonic acid (MSA), has been used to determine sea ice extent in ice cores up to 300 years in the past. However, due to gaps in the oxidation pathway of DMS, there are large uncertainties in the modelling of MSA formation. The addition of aqueous phase and halogen reactions have led to an improvement in the modelling of MSA concentration, but cloud formation of MSA is still lacking from atmospheric models. Understanding the reactions of DMS in the atmosphere is essential to both accurately modelling cloud formation processes and assessing the reliability of ice core measurements. As part of this project, BOXMOX, the KPP box model wrapper, has been used with the CRI-Strat and MCM mechanisms to compare to gas-phase experiments.
Atmospheric Gravity Waves Over the Southern Andes and Antarctic Peninsula
Phoebe Noble, PhD Student, University of Bath and British Antarctic Survey
The mesosphere at heights of ~50-90km above the surface of the earth, has dynamics that are dominantly driven by gravity waves. Gravity waves generated at lower heights propagate upwards into the mesosphere, growing in amplitude before breaking and depositing their momentum and changing the flow of the winds. Secondary gravity waves can also be formed where a gravity wave breaks. Despite the large influence of these waves, the physics governing their breaking and the generation of secondary gravity waves is not well understood. Gravity waves are small-scale processes and are therefore parametrised in General Circulation Models (GCMs), holding back the ability of GCMs to simulate the whole atmosphere well. A better understanding of gravity wave processes is needed to improve climate modelling.
One of the largest sources of gravity waves is the Andes mountain range. Here, strong surface winds are forced upwards due to the topography, generating orographic gravity waves that propagate upwards. This work tests the theory that intermittency of the orographic gravity waves acts as a source mechanism of secondary gravity waves. We first validate ERA5 temperatures for this region using observations from AIRS (Atmospheric Infrared Sounder on NASA's Aqua satellite) and the CORAL lidar at Tierra del Fuego. We explore correlations between stratospheric gravity wave activity in ERA5 (e.g. gravity wave momentum fluxes and intermittency) and the wind field in the mesosphere and lower thermosphere (MLT) measured using the meteor radar at Rio Grande.
This observational study brings together three different instruments and ERA5 re-analysis to examine gravity wave activity across the atmosphere.
Can the Offshore Wind Industry Weather the Climate Change Storm? Climate Models and AI aid in Studying the Risks.
Victoria Bessonova, PhD Student, University of Hull, Aura CDT
The UK has the ambition to supply 30% of its electricity from offshore wind farms. This makes it a part of the country’s critical infrastructure which means that the industry needs to ensure its safety and reliability. The industry will be affected by climate change, however, these impacts are not well understood. Offshore wind farms operate in very harsh environments and changes in that environment caused by climate change can pose a significant risk if these changes are not considered at every stage of a wind farm. Wind speeds and ocean wave heights are the main determinants of the wind turbine design, installation and maintenance planning, vessel design and the resulting electricity production. While wind speeds from climate models can be used to analyse some of the climate change impacts, ocean waves are not yet considered in climate models. This project uses the hindcast wind data from climate models and ocean wave data from ERA5 reanalysis to train a machine learning model. This model is then applied to the projected wind data from climate models to predict the ocean wave climate under different emission scenarios. The resulting dataset will be used to estimate the impacts of the projected ocean wave climate on the various aspects of the offshore wind industry.
Poster 28 - Withdrawn
Specifying States’ Mitigation Obligations: The Limits of Political Discretion
The term ‘deep uncertainty’ is permeating public discourse in particular with respect to the occurrence of tipping points due to anthropogenic climate change. In pointing at the scientific uncertainty in Earth System Models, states around the world claim wide political discretion in devising their mitigation policy. This claim is further buttressed by the argument that choosing a specific level of greenhouse gas emissions reduction is an inherently normative decision and therefore ‘belongs to the political domain’ for reasons of democratic legitimization. The present article engages in a detailed analysis of this claim and its underlying premises from a political and legal theory perspective as well as through the lens of the philosophy of science. The main argument put forward is that the law does not automatically grant wide political discretion for normative decisions, even in the context of ‘deep uncertainty’. Rather, in the case at hand, the scope for political discretion is tightly circumscribed, inter alia, by the equity principle and the obligation to protect inviolable fundamental rights. Indeed, a strong legal argument can be made that state conduct not aligned with keeping the global temperature rise below 1.5°C at an 83% likelihood not only classifies as an internationally wrongful act but, ultimately, is also deeply undemocratic.
A Review of Marine Cloud Brightening Considering Practical Implications
William Smith, PhD Student, University of Cambridge
Geoengineering is the name given to a collection of climate intervention strategies that aim to cool the Earth’s climate on a large enough scale to counteract anthropogenic warming. One such strategy is marine cloud brightening (MCB), wherein the albedo of stratocumulus clouds is modified to increase the amount of sunlight they reflect with the aim to produce a net negative change in effective radiative forcing. This is achieved by increasing the number of cloud condensation nuclei in existing clouds, causing the water droplets to be spread over a larger number of nuclei and hence be smaller, increasing the albedo of the cloud. Understanding whether MCB is an effective geoengineering strategy requires many different levels of investigation. There are the global climate models; these are used to study the global effects of MCB, such as if it has the desired cooling effect and if there are any unintended side effects. Meteorological models are used to resolve aerosol-cloud interactions, these model areas on the order of 10s-100s of kilometres and are useful for determining the meteorological conditions under which MCB can be most effective. Micro-scale models can be used to understand the micro-physical processes that determine the macro-scale properties of clouds, this is useful for determining the salt particle radii that are most effective for MCB. On top of understanding the climate science questions around MCB, another important step is solving the engineering problems. These involve developing an effective way of spraying sea salt of the right size at the right rates and developing autonomous boats to deploy MCB around the world.
Inter-Annual Variability in Fine Particulate Matter Pollution over China during 2013-2018: Role of Meteorology
Xuewei Hou, Researcher, Lancaster Environment Centre
Inter-annual variability in fine particulate matter pollution over China during 2013-2018: Role of meteorology
Impact of Chlorine from Very Short-Lived Substances on Stratospheric Ozone
Zihao Wang, PhD Student, University of Leeds
Although the Montreal Protocol has been successful in reducing the emissions of long-lived ozone-depleting substances (ODSs), some chlorinated very short-lived substances (VSLS, lifetimes < 6 months), which have not been regulated by the Protocol, are believed to be having an increasing impact on stratospheric ozone depletion. Emissions of VSLS have been reported to be increasing both from bottom-up estimates and observations. For example, stratospheric chlorine source gas injection of VSLS was estimated increase by around 70% from 2000 to 2007. We have used the TOMCAT/SLIMCAT 3-D offline chemical transport model (CTM) to investigate the impact of these increasing VSLS emissions.
TOMCAT/SLIMCAT contains a detailed description of stratospheric chemistry and is driven by meteorology from the European Centre for Medium-Range Weather Forecasts (ECMWF). We use surface mixing ratios of VSLS given by recent WMO Ozone Assessment Reports, including CH2Cl2, CHCl3, CH2ClCH2Cl, and C2Cl4. We present results from two sensitivity experiments from 1994 to 2020 (years before 2001 as spin-up) with and without the impacts of the above VSLS.The results show that if these main VSLS are removed from the atmosphere, the monthly averaged Antarctic ozone column could be up to 8 Dobson Unit (4.5%) larger, and the impacts become more significant with time as the VSLS mixing ratios increase. We also find that the patterns of the additional depletion remain similar regardless of the meteorological conditions throughout different years, showing how the VSLS chlorine enhances the standard halogen ozone loss processes. We show that although the extra depletion of stratospheric ozone by VSLS is currently small, it can be considered an increasing threat to the recovery of the ozone layer.