I obtained my PhD at Imperial College London's Space & Atmospheric Physics Group with NCEO and the Grantham Institute.
My primary research focuses on atmospheric radiative transfer modelling and satellite retrievals. In particular, I am interested in exploring how we can generate and model spectrally resolved irradiance based from satellite earth observations so that the global availability of solar energy resources can be better understood.
on Solar Energy Resources & Satellite Observations
Recorded at EGU 2019, Vienna. Session ESSI1.16 Earth Observations for Sustainable Development (Tuesday 9th April (08:30–12:30))
Recorded at the Joint DTP Conference (Sep 2018) Session 4B: Novel Measurements & Solar.
Recorded at Imperial's Space & Atmospheric Physics Group
Recorded at the NCEO Conference (Sep 2018) Session 6A: Satellite ECV data asset and climate services.
Choi et al. (2020). Developing Automated Methods to Estimate Spectrally Resolved Direct Normal Irradiance for Solar Energy Applications. Renewable Energy. https://doi.org/10.1016/j.renene.2021.03.127
on COVID-19 Lockdown & Solar Energy Resources
Presented at the NCEO Virtual Conference 2020. Using satellite observations of nitrogen dioxide (NO2) and aerosol optical depth during the COVID-19 lockdown, this study illustrates one of the potential hidden benefits of a cleaner atmosphere is more efficient large scale solar energy generation.
We estimate the change in broadband and spectrally resolved solar direct normal irradiance (DNI) at the surface over China from 15 February to 15 March 2019, and the same period in 2020. The latter period was chosen to coincide with the lockdown enforced due to the COVID-19 pandemic. Between the two periods, satellite observations show a widespread reduction in atmospheric NO2 concentrations and some notable changes to aerosol optical depth. Focusing on Wuhan, the first city to be placed under lockdown due to the pandemic, the combined changes in atmospheric species lead to a 19.8% increase in broadband surface DNI, along with a shift in the DNI spectral distribution towards bluer wavelengths. Feeding these changes into a solar cell simulator results in a 29.7% increase in the power output for a typical triple-junction concentrator photovoltaic cell (3J CPV). Around one-third of the increase in power output arises from the improved spectral matching between the input DNI spectrum and the solar cell, which in turn improved the 3J CPV operating efficiency by 2.6%. Similar spectral effects were also observed over Beijing and Shenzhen. Based on satellite observations, we estimate there was up to a 14% increase in 3J CPV efficiency over parts of China during the lockdown.
Choi et. al. (2020). COVID-19 lockdown air quality change implications for solar energy generation over China. Environ. Res. Lett. https://doi.org/10.1088/1748-9326/abd42f
Spatial & temporal Representativeness of AERONET sites
A collection of simple tools and results for quantitatively investigating the spatial and temporal representativeness of select AERONET sites.
Other work
An interactive visualisation developed as part of my on-going PhD work shows the effects of how atmospheric constituents and viewing geometry affect the spectral circumsolar normal irradiance. For more, please refer to one of the presentation videos above.
An interactive playground that allows you to explore the effects of aerosols on the solar direct normal irradiance at ground level.
Authored articles on earth observations and climate change:
Choi, K. T. (2019). The role of climate services in handling climate change risks: Contributions of UKCP18. Weather, 74(7), 255-256. doi:10.1002/wea.3526
Choi, K. T. (2018). Space, satellite and solutions: Essential climate variables and the future of climate monitoring from space. Weather,73(12), 390-391. doi:10.1002/wea.3306
Outreach Work: RAISING AWAIRNESS: THE BOARD GAME
Raising awAIRness is a simple board game designed to educate young kids about the potential exposure to air pollution as one commute across London. Designed and presented at the Imperial Festival 2018.
How to Play This Game
This game introduces some of the potential exposures to air pollution that a Londoner could encounter.
Requirements
Designed for 2 to 4 players, this game requires a die with only 1, 2 and 3 on its faces. If you are playing with a normal 6-sided die, move 1, 2 and 3 steps if you throw a 4, 5 and 6 respectively. You will also need 50 to 100 tokens, depending on the number of players. The game should take no more than 3 to 4 minutes for 4 people.
Goals of the Game
All players start at the Home station with 15 tokens, which represent air pollution exposure level. Put the remaining tokens in a central repository next to the board. Your goal is to traverse across London to the School station as quickly as possible whilst maintaining the lowest air pollution exposure possible.
Navigating Across the Board
To navigate across London, players take turn to roll the die. After rolling, step through the corresponding number of stations.
You can go both forward and backward, and you can even loop back onto yourself if you desire to do so. Ignore whether a station has already been occupied by another player. Whenever you encounter an interchange, feel free to switch between lines. If you land on an interchange, do nothing.
Using the Tokens
Stations that you stop at en route increase or decrease the number of tokens by varying amounts. Stations with a red badge and an up arrow increase your exposure level, whereas stations with a green badge and a down arrow decrease your exposure level. Accrue or remove the corresponding amount of tokens when you land on a station. Only do so for the station that you have landed on, and not the stations that you are simply travelling through.
Special Stations
There are 3 types of special station, denoted by the dark blue badges. You will neither gain nor lose any token on these stations. Instead, depending on the specific station, you will:
Lose the next round;
Roll again immediately or;
Be immune to any token accruement on the next and only the next round.
Ending the Game
Once you have arrived at the School station, you have completed your journey. When players arrive at the School and complete the game, they accrue or lose tokens, depending on their order of arrival, and the number of players:
If there are four players:
First arrival: -5 tokens
Second arrival: -2 tokens
Third arrival: +2 tokens
Last arrival: +5 tokens
If there are only three players, follow these instead:
First arrival: -3 tokens
Second arrival: Do nothing
Last arrival: +3 tokens
If there are only two players, follow these instead:
First arrival: -2 tokens
Second arrival: +2 tokens
Tally up the number of tokens each player has once everyone has finished their journey. The person with the lowest number of token wins the game. If you have 0 tokens but have yet to reach School, you must continue playing. If you step on a reduction station, do nothing. However, you can still accrue new tokens.
Game Strategy
While the player can switch between lines and paths through the game, there are three main lines that connect Home to School:
Red Line: This is the fastest line between Home and School, but this convenience comes with a trade off, as almost all the stations along the route are heavily polluting. They significantly increase your air pollution exposure levels.
Green Line: This is the healthy, environmentally friendly option. Almost all the stations along this route reduce your exposure level. However, this route is long and windy, which is inconvenient and slow compared to the red line.
Yellow Line: This is the cautious, middle-ground option, with varying polluting and environmentally friendly stations. This route has a moderate number of stops, and a moderate air pollution footprint and exposure.
