Author Archives: yeonjoolee

IAMAS Early Career Scientist Webinar Series #4 October 20th 2021

On the multi-decadal variability of the tropical stratosphere

Dr. Fernando Iglesias-Suarez
Research Associate 
Institute of Atmospheric Physics
German Aerospace Center

Wednesday, October 20th at 14:00-15:00 UTC
All attendees must register through the following link: https://univ-lille-fr.zoom.us/webinar/register/WN_YLiStgAqS5awrXINxMTsGw

Abstract

Natural variability is an important component of the climate system which can mask anthropogenically-induced changes. Observational estimates and modeling evidence suggest an acceleration of the stratospheric Brewer-Dobson circulation (BDC) over the recent past, driven by climate change and stratospheric ozone depletion. Yet, low-frequency natural variability can compromise the detection of such forced changes. Here, we explore the naturally varying strength of the BDC and how this has consequences for the composition of the stratosphere. We show, using observations and model simulations, that multi-decadal natural variability in the Pacific Ocean -namely the Interdecadal Pacific Oscillation, IPO- is linked to the BDC. This troposphere-stratosphere interaction helps us disentangle structural changes in the BDC associated with human interferences. Furthermore, naturally occurring slow changes in transport can help us understand recent low levels of ozone in the middle tropical stratosphere, which is in apparent disagreement with the expected ozone recovery. These findings have implications for both reconciling theory and observed changes in the circulation and composition of the tropical stratosphere.

Dr. Fernando Iglesias-Suarez is a climate scientist with a strong interest in developing and applying machine learning techniques (ML) to advance climate models and analysis, understanding links and interactions with other parts of the Earth system to address the scientific challenges of global change.
 
By training, he is an Environmental scientist and worked for few years as a consultant. He obtained MSc in Climate Change at the University of East Anglia (UEA) “Investigating geoengineering solutions to meet the 2ºC target.” His PhD focused on stratospheric ozone and climate interactions.
 
After graduation, he continued to explore the role of natural halogens in tropospheric ozone in a changing climate at the Spanish National Research Council (CSIC).
 
Finally, he joined the Earth System Model Evaluation and Analysis Department at the German Aerospace Center (DLR). Within the “Understanding and Modelling the Earth System with Machine Learning (USMILE)” project, he focused on developing new methods and approaches via ML means to eliminate long-standing systematic errors in climate models and to provide more robust climate projections.

IAMAS Early Career Scientist Webinar Series #3 September 21st 2021

Diverse Clouds and Hazes in Planetary Atmospheres

Dr. Xi Zhang
Associate Professor
Department of Earth and Planetary Sciences
University of California Santa Cruz

Tuesday September 21st at 15:00-16:00 UTC
All attendees must register through the following link: https://univ-lille-fr.zoom.us/webinar/register/WN_cASSNyX3T7mm1VqQKxabsQ

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Abstract

Clouds and hazes are ubiquitous in all substantial atmospheres in the Solar System. Abundant particles are also inferred from observations in hotter atmospheres of exoplanets and brown dwarfs. Exotic clouds in extraterrestrial atmospheres could result from condensation of water, ammonia, sulfuric acid, salts, silicates, metals, and/or nitriles and hydrocarbons produced by atmospheric chemistry upon UV radiation and high-energy particles. In this talk I plan to showcase several examples we have studied recently to elaborate significant roles of clouds and hazes on the energy budget, thermal structure, chemistry and dynamical circulation in planetary atmospheres. I will first start from our sister planet Venus and talk about sulfur chemistry and formation of sulfuric acid clouds. I will use a simple cloud model to demonstrate the critical role of binary condensation in the sulfur acid formation and its impact on gas species such as sulfuric oxides and water vapor. I will then talk about the thin, cold and hazy atmospheres in the outer Solar System. Using Titan, Triton and Pluto as examples, I will show how these atmospheres regulate themselves such that the chemically produced hydrocarbon haze/ice particles significantly dominate the radiative energy balance over the gas volatiles. In particular, the particles could explain the colder-than-expected temperature on Pluto observed by the New Horizons mission. Lastly, I would like to talk about clouds in hydrogen-dominated atmospheres such as Jupiter, hot Jupiters and brown dwarfs, highlighting the importance of clouds on the interpretation of the observed spectra and light curves and the impacts of cloud radiative feedback and moist convection on the atmospheric circulation on those bodies. Specifically, I will talk about how could clouds help us to understand some recent puzzles on Jupiter’s atmosphere observed from the Juno mission.

Dr. Xi Zhang is an associate professor in the Department of Earth and Planetary Sciences at University of California Santa Cruz. He got his bachelor degree in space science from Peking University in 2007 and received the Ph.D. degree in planetary sciences from California Institute of Technology in 2013. Then he spent two years in University of Arizona as a postdoc and started his faculty position since 2015 at UC Santa Cruz. Xi’s research covers many topics in planetary atmospheres within and out of the Solar System. He has been awarded by the AGU Ronald Greeley Early Career Award in 2019.

IAMAS Early Career Scientist Webinar Series #2 August 25th 2021

Quantifying the Human Impact on Climate by Doing “Experiments” on Clouds

Dr. Edward Gryspeerdt
Royal Society University Research Fellow
Department of Physics
Imperial College London

Wednesday August 25th at 15:00-16:00 UTC
All attendees must register through the following link:https://univ-lille-fr.zoom.us/webinar/register/WN_47jo-glETPuz0p-v0AHq1g

Abstract
Almost all cloud droplets and many ice crystals form on small (nanometre to micron sized) particles known as aerosols. Increases in aerosols from human activity have increased the concentration of droplets in clouds since the industrial revolution, making clouds more reflective and cooling the climate offsetting a significant fraction of the warming from greenhouse gases. Unfortunately, clouds are highly variable which makes the impact of aerosols difficult to isolate. This means that the impact of aerosols on clouds remains one the most uncertain anthropogenic forcing of the climate system.

Here we provide a way around this problem, by using isolated sources of aerosol as natural experiments into cloud behaviour. By matching satellite observations of clouds to new datasets on ship positions and emissions, we can characterise the aerosol-cloud system in hundreds of thousands of cases. This allows us to measure not only which clouds are sensitive to aerosols, but how sensitive they are and how quickly they respond to changes in their environment. As well as providing new insights into cloud processes useful for constraining models, it also demonstrates a way to monitor shipping pollution in the open ocean.

Dr. Edward Gryspeerdt is a Royal Society University Research Fellow in the Department of Physics at Imperial College London. He previously worked at the Universities of Leipzig and and Oxford, looking at aerosol-cloud interactions and cloud physics in observations and models.

IAMAS Early Career Scientist Webinar Series #1 June 22nd 2021

Tuesday June 22nd at 20:00-21:00 UTC

All attendees must register through the following link:https://univ-lille-fr.zoom.us/webinar/register/WN_RGclPVVCRWifn6NhS3lVJQ

An Introduction to IAMAS

Prof. Joyce Penner
President, International Association of Meteorology and Atmospheric Science
Distinguished Professor of Atmospheric Science, University of Michigan, USA

Professor Joyce Penner, the President of IAMAS, will first give an introductory talk about the IAMAS organization.

South Pacific Ocean Climate Dynamics and Predictability

Dr. Jiale Lou
CIRES, University of Colorado Boulder
NOAA Physical Science Laboratory

Abstract
The mechanisms and predictability of Pacific decadal climate variability (PDV) is an active area of research in climate science and is one of high societal importance. To date, most research into PDV has been focused on mechanisms and responses in the North Pacific. Dr Lou’s PhD thesis presents a comprehensive investigation, based on the development and application of a family of hierarchical stochastically forced models, of the mechanisms underpinning PDV climate predictability and that focuses on the role of the South Pacific Ocean and coupling to the tropics.

First, a simple one-dimensional first-order autoregressive (AR1) model was used to understand the space and time variations of the South Pacific decadal oscillation (SPDO) – which represents the leading sea surface temperature (SST) mode in the South Pacific. The analysis revealed that the first Pacific-South American (PSA1) pattern is the key atmospheric driver of the SPDO. Further, the leading mode of integrated subsurface upper ocean temperature variability was shown to match expectations from the propagation of oceanic Rossby waves across the extratropical South Pacific, with the atmospheric PSA variability providing the high-frequency ‘noise’ source of the observed low-frequency (‘reddened’) SST SPDO response.

Second, the stochastically forced AR1 model was generalised to higher-dimensional fields with the inclusion of spatial features using a linear inverse model (LIM) approach. The deterministic dynamics underpinning the combined tropical and South Pacific system was investigated, with the seasonal predictive skill of the SPDO and El Niño–Southern Oscillation (ENSO) quantified under the LIM framework. It was found that, although the oscillatory periods of ENSO and the SPDO are distinct – the former oscillating on interannual timescales and the latter oscillating on (inter-)decadal timescales – their damping time scales were very similar, and their predictive skill comparable. With the inclusion of subsurface processes in the extratropical South Pacific, the linear predictive skill of both ENSO and the SPDO was found to be enhanced. Overall, the study showed that Pacific SST variability forecast skill from the computationally cheap LIMs was competitive with state-of-the-art operational seasonal forecast systems that employ sophisticated initialisation schemes and general circulation models, thus providing a useful benchmark for these operational systems.

Third, the LIM framework was applied to gain a deeper understanding of the role of stochastic forcing from the atmospheric PSA variability and to determine the optimal structures for initialised forecasts of the tropical and South Pacific climate system and its variability. This analysis revealed the spatial imprint of atmospheric PSA variability combined with temporal stochastic forcing that acts to drive the low frequency oceanic SST variability across the tropical and South Pacific, and excites optimal initial perturbations for the prediction of ENSO and the SPDO.

Finally, informed by the aforementioned hierarchy of stochastically forced linear reduced space models, Jiale’s PhD thesis culminates with an overarching framework that links the atmosphere to the surface and subsurface oceans across a range of time scales from (intra-)seasonal to (inter-)decadal. Hence, the thesis provides, for the first time, a mechanistic framework and integrated understanding of the drivers of large-scale South Pacific climate variability and predictability.

Dr Jiale Lou is now a postdoctoral researcher at the CIRES, University of Colorado Boulder and the NOAA Physical Science Laboratory. He is working on seasonal to decadal climate predictions and predictability of some environmental conditions by using a series of empirical climate models. His research interests include large-scale climate variability, climate dynamics, and climate predictions and predictability studies. Prior to working with NOAA, he obtained his PhD degree in quantitative marine science at University of Tasmania, Australia. His PhD thesis is about the South Pacific Ocean climate dynamics and predictability.