Why extreme heat and air pollution matters?
Every year, more than 7 million people die from air pollution and another five million from extreme heat around the world. As the frequency and severity of extreme events are on rise, occcurence of heatwaves and air pollution episodes are also increasing, with direct impact on human health and economy.
Air pollution and extreme heat are closely related not only through physical and chemical pathways but also through policies and their impacts on human health. While extreme heat impacts air pollution mainly through circulation changes, increased energy demand, formation of secondary pollutants, pollution transport, increased potential for wildfires, radiation changes and cloud formation, it also shares policy implications with air pollution. Aerosols are generally known to cool down the Earth’s surface by blocking the solar radiation but they also heat up the atmosphere by absorption of solar and thermal radiation. For example, air pollution in the US has been declining after the implementation of clean air act in 1970s but the resulting reduction in atmospheric aerosols might have paradoxically contributed to the recent rise in extreme heat occurences by allowing more radiation to reach the ground. Extreme heat and air pollution also have several common health impacts, on respiratory and cardiovascular diseases as well as mental, reproductive and immune system health, which get amplified through their combined exposure especially on residents with existing health conditions and marginalized societies and vulnerable populations.
Existing research gaps
Many of the global and regional models currently in use for weather prediction have biases in their output fields such as aerosol concentrations, temperature and humidity, partly due to their coarse spatial resolution and partly because they do not account for the local factors that affect air quality and weather, for example irrigation. The coupling of land-atmosphere and lake-land processes is also poorly represented in traditional models typically allowing only one-way interaction and feedback. Even more importantly, aerosol-radiation and aerosol-cloud-precipitation interactions are highly simplified, which lead to over- or under-estimation of relevant atmospheric and near-surface fields.
What is the solution?
The above interactions are just a few examples. Our Earth’s environment is much more complex than you can imagine. Today’s Earth System Models try to simulate such interactions so that we can make better or more accurate forecasts. Our conventional climate and weather forecast models lack many such interactions, partly for computational reasons and partly due to the difficulty of modeling such interactions. Open source, community-developed regional weather models such as WRF and WRF-Chem allow researchers to customize the model to a local region and produce high-resolution, more accurate forecast of air pollution and extreme heat. I employ WRF and WRF-Chem to investigate research questions such as:
How do atmospheric aerosols impact Earth’s radiation budget and surface temperature?
How do aerosols influence extreme events such as extreme rainfall, air pollution episodes, and heatwaves?
What factors influence heat exposure on vulnerable populations such as seniors, farmworkers, and other outdoor workers?
What are the compounding impacts of extreme heat and air pollution on human health?
How can we improve the forecasting of dust storms, which can cause fatal motor vehicle accidents, worsen asthma, and damage crops and critical infrastructure?