William T. Ball

William T. Ball
Delft University of Technology | TU · Department of Geoscience and Remote Sensing

MSci, PhD

About

58
Publications
8,812
Reads
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1,387
Citations
Introduction
Will is an Assistant Professor at the Department of Geoscience and Remote Sensing at TU Delft, and a visiting scientist at KNMI in De Bilt, both in the Netherlands. His work focuses primarily on air quality and air pollution with in a climate change context, using satellite observations and chemistry climate models. Will also works on the application of new statistical analysis techniques, and continues to work on solar irradiance and research in ozone variability and trends.
Additional affiliations
February 2020 - present
Delft University of Technology
Position
  • Professor (Assistant)
Description
  • Air pollution, atmospheric science, climate change
October 2016 - October 2016
ETH Zurich
Position
  • Lecturer
Description
  • Course name: Klimasysteme Role: Guest lecturer Lecture: Solar Radiation
January 2016 - present
ETH Zurich
Position
  • Lecturer
Description
  • Course name: Radiation and climate change Semester: Spring 2016, Spring 2017, Spring 2018
Education
September 2002 - June 2006
Durham University
Field of study
  • Mathematics and Physics

Publications

Publications (58)
Preprint
Full-text available
There is evidence that the ozone layer has begun to recover owing to the ban on the production of halogen-containing ozone-depleting substances (hODS) accomplished by the Montreal Protocol and its Amendments (MPA). However, recent studies, while reporting an increase in tropospheric ozone and confirming the ozone recovery in the upper stratosphere,...
Article
Full-text available
This paper features the new atmosphere–ocean–aerosol–chemistry–climate model, SOlar Climate Ozone Links (SOCOL) v4.0, and its validation. The new model was built by interactively coupling the Max Planck Institute Earth System Model version 1.2 (MPI-ESM1.2) (T63, L47) with the chemistry (99 species) and size-resolving (40 bins) sulfate aerosol micro...
Preprint
Full-text available
This paper features the new Atmosphere-Ocean-Aerosol-Chemistry-Climate Model SOCOLv4.0 and its validation. The new model was built by interactively coupling the MPI-ESM1.2 Earth System Model (T63, L47) with the chemistry (99 species) and size-resolving (40 bins) sulfate aerosol microphysics modules from the Aerosol-Chemistry-Climate Model SOCOL-AER...
Article
Full-text available
As part of the Model Intercomparison Project on the climatic response to Volcanic forcing (VolMIP), several climate modeling centers performed a coordinated pre-study experiment with interactive stratospheric aerosol models simulating the volcanic aerosol cloud from an eruption resembling the 1815 Mt. Tambora eruption (VolMIP-Tambora ISA ensemble)....
Article
Full-text available
Water vapor (H2O) is the source of reactive hydrogen radicals in the middle atmosphere, whereas carbon monoxide (CO), being formed by CO2 photolysis, is suitable as a dynamical tracer. In the mesosphere, both H2O and CO are sensitive to solar irradiance (SI) variability because of their destruction/production by solar radiation. This enables us to...
Preprint
Full-text available
As part of the Model Intercomparison Project on the climatic response to Volcanic forcing (VolMIP), several climate modeling centers performed a coordinated pre-study experiment with interactive stratospheric aerosol models simulating the volcanic aerosolcloud from an eruption resembling the 1815 Mt Tambora eruption (VolMIP-Tambora ISA ensemble). T...
Article
Full-text available
The stratospheric ozone layer shields surface life from harmful ultraviolet radiation. Following the Montreal Protocol ban on long-lived ozone-depleting substances (ODSs), rapid depletion of total column ozone (TCO) ceased in the late 1990s, and ozone above 32 km is now clearly recovering. However, there is still no confirmation of TCO recovery, an...
Article
Full-text available
Reliable ozone trends after 2000 are essential to detect early ozone recovery. However, the long-term ground-based and satellite ozone profile trends reported in the literature show a high variability. There are multiple reasons for variability in the reported long-term trends such as the measurement timing and the dataset quality. The Payerne Swit...
Preprint
Full-text available
Abstract. Multi-instrument comparison analyses are essential to assess the long-term stability of data records by estimating the drift and bias of instruments. The ozone profile dataset from the SOMORA microwave radiometer (MWR) in Payerne, Switzerland, was compared with profiles from the GROMOS MWR in Bern, Switzerland, satellite instruments (MLS,...
Article
Full-text available
The Montreal Protocol, and its subsequent amendments, has successfully prevented catastrophic losses of stratospheric ozone, and signs of recovery are now evident. Nevertheless, recent work has suggested that ozone in the lower stratosphere (95 %, 30∘ S–30∘ N) decreases dominate the quasi-global integrated decrease (99 % probability); the integrate...
Article
Full-text available
The stratospheric ozone layer shields surface life from harmful ultraviolet radiation. Following the Montreal Protocol ban of long-lived ozone depleting substances (ODSs), rapid depletion of total column ozone (TCO) ceased in the late 1990s and ozone above 32 km now enjoys a clear recovery. However, there is still no confirmation of TCO recovery, a...
Article
Full-text available
The Montreal Protocol has successfully prevented catastrophic losses of stratospheric ozone, and signs of recovery are now evident. Nevertheless, recent work suggests that ozone in the lower stratosphere (SG ozone composite. We find that the observed 2017 resurgence was only around half that modelled by the CTM, was of comparable magnitude to other...
Article
Full-text available
Plain Language Summary Changes in the output of the Sun are thought to influence surface weather and climate through a set of processes initiated by the enhancement of upper stratosphere (32–48 km) ozone. In order to understand and assess the solar impact on the climate system, it is important that models reproduce the observed solar signal. Howeve...
Chapter
The ultimate goal of LOTUS is to improve confidence in calculated ozone trend values via an improved under-standing of the uncertainties. Chapter 3 highlighted many of the challenges facing analyses of long-term ozone time series, and despite the fact that many of those challenges still need to be addressed, it is worthwhile to assess the trend res...
Chapter
Full-text available
One of the primary motivations of the LOTUS effort is to attempt to reconcile the discrepancies in ozone trend results from the wealth of literature on the subject. Doing so requires investigating the various methodolo-gies employed to derive long-term trends in ozone as well as to examine the large array of possible variables that feed into those...
Article
Full-text available
An accurate quantification of the stratospheric ozone feedback in climate change simulations requires knowledge of the ozone response to increased greenhouse gases. Here, we present an analysis of the ozone layer response to an abrupt quadrupling of CO2 concentrations in four chemistry-climate models. We show that increased CO2 levels lead to a dec...
Article
Full-text available
Ozone forms in the Earth's atmosphere from the photodissociation of molecular oxygen, primarily in the tropical stratosphere. It is then transported to the extratropics by the Brewer–Dobson circulation (BDC), forming a protective ozone layer around the globe. Human emissions of halogen-containing ozone-depleting substances (hODSs) led to a decline...
Article
Full-text available
Observations of stratospheric ozone from multiple instruments now span three decades; combining these into composite datasets allows long-term ozone trends to be estimated. Recently, several ozone composites have been published, but trends disagree by latitude and altitude, even between composites built upon the same instrument data. We confirm tha...
Article
Full-text available
Ozone forms in the Earth's atmosphere from the photodissociation of molecular oxygen, primarily in the tropical stratosphere. It is then transported to the extratropics by the Brewer-Dobson circulation (BDC), forming a protective ozone layer around the globe. Human emissions of halogen-containing ozone-depleting substances (hODSs) led to a decline...
Article
Full-text available
The eruption of Mt. Tambora in 1815 was the largest volcanic eruption of the past 500 years. The eruption had significant climatic impacts, leading to the 1816 year without a summer, and remains a valuable event from which to understand the climatic effects of large stratospheric volcanic sulfur dioxide injections. The eruption also resulted in one...
Article
The double-peaked response of the tropical stratospheric temperature profile to the 11-year solar cycle (SC) has been well documented. However, there are concerns about the origin of the lower peak due to potential aliasing with volcanic eruptions or the El Niño Southern Oscillation (ENSO) detected using multiple linear regression (MLR) analysis. W...
Article
Full-text available
Sporadic solar energetic particle (SEP) events affect the Earth’s atmosphere and environment, in particular leading to depletion of the protective ozone layer in the Earth’s atmosphere, and pose potential technological and even life hazards. The greatest SEP storm known for the last 11 millennia (the Holocene) occurred in 774–775 AD, serving as a l...
Article
Full-text available
To accurately estimate decadal trends in stratospheric ozone requires stable long-term observations. Recently, several ozone composites have been published that combine observations from multiple instruments to span more than three decades. Despite this, trends disagree by latitude and altitude, even between composites built upon the same instrumen...
Article
Full-text available
We compare simulations from three high-top (with upper lid above 120 km) and five medium-top (with upper lid around 80 km) atmospheric models with observations of odd nitrogen (NOx = NO + NO2), temperature, and carbon monoxide from seven satellite instruments (ACE-FTS on SciSat, GOMOS, MIPAS, and SCIAMACHY on Envisat, MLS on Aura, SABER on TIMED, a...
Conference Paper
There is growing evidence that variability associated with the 11-year solar cycle has an impact at the Earth’s surface and influences its weather and climate. Although the direct response to the Sun’s variability is extremely small, a number of different mechanisms have been suggested that could amplify the signal, resulting in regional signals th...
Article
Full-text available
We find that wintertime temperature anomalies near 4g hPa and 50°g N/S are related, through dynamics, to anomalies in ozone and temperature, particularly in the tropical stratosphere but also throughout the upper stratosphere and mesosphere. These mid-latitude anomalies occur on timescales of up to a month, and are related to changes in wave forcin...
Article
Full-text available
We compare simulations from three high-top (with upper lid above 120 km) and five medium-top (with upper lid around 80km) atmospheric models with observations of odd nitrogen (NOx = NO + NO2), temperature, and carbon monoxide from seven satellite instruments (ACE-FTS on SciSat, GOMOS, MIPAS, and SCIAMACHY on Envisat, MLS on Aura, SABER on TIMED, an...
Article
The solar rotational variability (27-day) signal in the Earth's middle atmosphere has been studied for several decades, as it was believed to help in the understanding of the Sun's influence on climate at longer timescales. However, all previous studies have found that this signal is very uncertain, likely due to the influence of the internal varia...
Article
Full-text available
Stratospheric water vapour (SWV) is an important component of the Earth's atmosphere as it affects both radiative balance and the chemistry of the atmosphere. Key processes driving changes in SWV include dehydration of air masses transiting the cold-point tropopause (CPT) and methane oxidation. We use a chemistry–climate model to simulate changes i...
Article
Full-text available
The enhancement of the stratospheric aerosol layer by volcanic eruptions induces a complex set of responses causing global and regional climate effects on a broad range of timescales. Uncertainties exist regarding the climatic re- sponse to strong volcanic forcing identified in coupled cli- mate simulations that contributed to the fifth phase of th...
Article
Full-text available
The switching of the total solar irradiance (TSI) backup radiometer (PREMOS-B) to a primary role for 2 weeks at the end of the PICARD mission provides a unique opportunity to test the fundamental hypothesis of radiometer experiments in space, which is that the sensitivity change of instruments due to the space environment is identical for the same...
Article
Full-text available
Science, in our case the climate and geosciences, is increasingly interdisciplinary. Scientists must therefore communicate across disciplinary boundaries. For this communication to be successful, scientists must write clearly and concisely, yet the historically poor standard of scientific writing does not seem to be improving. Scientific writing mu...
Article
Full-text available
We find that wintertime temperature anomalies near 4 hPa and 50° N/S are related, through dynamics, to anomalies in ozone and temperature, particularly in the tropical stratosphere, but also throughout the upper stratosphere and mesosphere. These mid-latitude anomalies occur on timescales of up to a month, and are related to changes in wave-forcing...
Article
Full-text available
Stratospheric water vapour (SWV) is an important component of the Earth's atmosphere as it affects both radiative balance and the chemistry of the atmosphere. Key processes driving changes in SWV through the 21st century include dehydration of air masses transiting the cold-point tropopause (CPT) and methane oxidation. Increasing surface temperatur...
Article
Full-text available
Up to now our understanding of the 11-year ozone solar cycle signal (SCS) in the upper stratosphere has been largely based on the SAGE II (v6.2) data record which indicated a large positive signal which could not be reproduced by models, calling into question our understanding of the chemistry of the upper stratosphere. Here we present an analysis...
Article
Full-text available
The state of the stratospheric ozone layer and the temperature structure of the atmosphere are largely controlled by the solar spectral irradiance (SSI) through its influence on heating and photolysis rates. This study focuses on the uncertainties in the photolysis rate response to solar irradiance variability related to the choice of SSI data set...
Article
Full-text available
The state of the stratospheric ozone layer and the temperature structure of the atmosphere are largely controlled by the solar spectral irradiance (SSI) through its influence on heating and photolysis rates. This study focuses on the uncertainties in the photolysis rate response to solar irradiance variability related to the choice of SSI data set...
Article
Full-text available
The enhancement of the stratospheric aerosol layer by volcanic eruptions induces a complex set of responses causing global and regional climate effects on a broad range of timescales. Uncertainties exist regarding the climatic response to strong volcanic forcing identified in coupled climate simulations that contributed to the fifth phase of the Cl...
Article
Some of the natural variability in climate is understood to come from changes in the Sun. A key route whereby the Sun may influence surface climate is initiated in the tropical stratosphere by the absorption of solar ultraviolet (UV) radiation by ozone, leading to a modification of the temperature and wind structures and consequently to the surface...
Article
Solar variability can influence surface climate, for example by affecting the mid-to-high-latitude surface pressure gradient associated with the North Atlantic Oscillation. One key mechanism behind such an influence is the absorption of solar ultraviolet (UV) radiation by ozone in the tropical stratosphere, a process that modifies temperature and w...
Article
Full-text available
Science, in our case climate- and geo-science, is increasingly interdisciplinary. Scientists must therefore communicate across disciplinary boundaries. For this communication to be successful, scientists must write clearly and concisely, yet, the historically poor standard of scientific writing does not seem to be improving. Scientific writing must...
Conference Paper
Full-text available
Considering the diurnal cycle of stratospheric ozone is essential for a correct estimation of the ozone trends. At northern hemispheric mid-latitudes, the diurnal ozone content varies with altitude from +4% at 25 km to-25% at 60 km with respect to midnight values. The diurnal variation is attributed to dynamical or chemical causes depending on the...
Article
Total solar irradiance and UV spectral solar irradiance have been monitored since 1978 through a succession of space missions. This is accompanied by the development of models aimed at replicating solar irradiance by relating the variability to solar magnetic activity. The NRLSSI and SATIRE-S models provide the most comprehensive reconstructions of...
Article
Full-text available
We investigate the relationship between spectral solar irradiance (SSI) and ozone in the tropical upper stratosphere. We find that solar cycle (SC) changes in ozone can be well approximated by considering the ozone response to SSI changes in a small number individual wavelength bands between 176 and 310 nm, operating independently of each other. Ad...
Article
Full-text available
We present a revised and extended total and spectral solar irradiance (SSI) reconstruction, which includes a wavelength-dependent uncertainty estimate, spanning the last three solar cycles using the SATIRE-S model. The SSI reconstruction covers wavelengths between 115 and 160,000 nm and all dates between August 1974 and October 2009. This represent...
Article
Full-text available
The Sun and stars with low magnetic activity levels, become photometrically brighter when their activity increases. Magnetically more active stars display the opposite behaviour and get fainter when their activity increases. We reproduce the observed photometric trends in stellar variations with a model that treats stars as hypothetical Suns with c...
Article
Full-text available
Solar spectral fluxes (or irradiance) measured by the SOlar Radiation and Climate Experiment (SORCE) show different variability at ultraviolet (UV) wavelengths compared to other irradiance measurements and models (e.g. NRL-SSI, SATIRE-S). Some modelling studies have suggested that stratospheric/lower mesospheric O3 changes during solar cycle 23 (19...
Article
Full-text available
Solar spectral fluxes (or irradiance) measured by the SOlar Radiation and Climate Experiment (SORCE) show different variability at ultraviolet (UV) wavelengths compared to other irradiance measurements and models (e.g. NRL-SSI, SATIRE-S). Some modelling studies have suggested that stratospheric/lower mesospheric O3 changes during solar cycle 23 (19...
Article
Measurements of the changes in the solar spectral irradiance are available for three solar cycles and there is a good understanding of the irradiance changes on time scales ranging from a day to a few years. Observing longer-term changes (tens of years and longer) is more difficult, and there is much uncertainty regarding the Sun's long-term behavi...
Article
The magnitude and the phase of the solar irradiance variations are strongly wavelength dependent. Strongest changes occur in the UV range, which is of prime interest for climate studies. The variability is much weaker in the visible and infrared ranges, and in some intervals it is in anti-phase with the solar cycle and the TSI changes. The magnitud...
Article
Full-text available
Context: The study of variations in total solar irradiance (TSI) is important for understanding how the Sun affects the Earth's climate. Aims: Full-disk continuum images and magnetograms are now available for three full solar cycles. We investigate how modelled TSI compares with direct observations by building a consistent modelled TSI dataset. The...
Article
Full-text available
Solar irradiance models that assume solar irradiance variations to be due to changes in the solar surface magnetic flux have been successfully used to reconstruct total solar irradiance on rotational as well as cyclical and secular time scales. Modelling spectral solar irradiance is not yet as advanced, and also suffers from a lack of comparison da...
Article
Full-text available
Aims: We investigate how well modeled solar irradiances agree with measurements from the SORCE satellite, both for total solar irradiance and broken down into spectral regions on timescales of several years. Methods: We use the SATIRE model and compare modeled total solar irradiance (TSI) with TSI measurements between 2003 and 2009. Spectral solar...
Article
Climate models rely on accurate total and spectral solar irradiance inputs, but until 2003 con-tinuous spectral irradiance information across a large portion of the solar spectrum was lacking. Since the launch of the Solar Radiation and Climate Experiment (SORCE), with the Spectral Irradiance Monitor (SIM) observing the UV, visible and IR, data hav...

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