1. GEOS-Chem and AMOD Average 48-hr PM2.5, December 9th-11th, 2017
Modelled and measured fine-scale spatiotemporal variability in AOD and PM2.5 across the Colorado Front Range Michael Cheeseman1*, Jeffrey R. Pierce1, Bonne Ford1, John Volckens1, and the CEAMS project team
1Colorado State University, Fort Collins, CO, USA
1. Introduction
2. The CEAMS device and pilot campaign
3. GEOS-Chem simulations over Colorado
Background:
Atmospheric particulate matter smaller than 2.5 μm in diameter (PM2.5) can penetrate deeply into the human lung, which can result in respiratory and cardiovascular diseases.
The Global Burden of Disease (GBD) estimates that human exposure to PM2.5 is the fifth ranking mortality risk factor worldwide. [Cohen et al., 2017]
Currently, satellites are used to assess the global health burden of PM2.5 exposure. However, they cannot measure PM directly, instead relying on aerosol optical depth (AOD) measurements (a measure of light extinction through the column). A common method for deriving PM from satellite AOD measurements is multiplying the satellite AOD by PM:AOD ratios generated in chemical transport models like GEOS-Chem:
𝑷𝑴 𝟐.𝟓, 𝐬𝐚𝐭𝐞𝐥𝐥𝐢𝐭𝐞 = 𝑨𝑶𝑫 𝐬𝐚𝐭𝐞𝐥𝐥𝐢𝐭𝐞 𝑷𝑴 𝟐.𝟓, 𝐦𝐨𝐝𝐞𝐥 𝑨𝑶𝑫 𝐦𝐨𝐝𝐞𝐥 [Liu et al., 2004]
Limitations:
Modeled PM2.5:AOD ratios need validation from in-situ measurements!
Modeled PM2.5:AOD ratios do not capture small-scale variability.
PM and AOD reference instruments are expensive and sparsely distributed globally.
CEAMS Team Objectives:
Citizen Enabled Aerosol Measurements for Satellites (CEAMS) device
The CEAMS team created the Aerosol Mass and Optical Depth (AMOD) sensor, which includes:
Real-time light-based PM2.5 monitor (Plantower PMS5003)
Filter-based PM2.5 monitor
Photodiode-based AOD monitor at 4 wavelengths (440 nm, 520 nm, 680 nm, 870 nm).
The CEAMS Pilot Campaign
We recruited citizen scientists from Fort Collins, CO and the surrounding area to complete a pilot campaign using the AMOD devices.
December 2nd-4th, 9th-11th, 2017
150+ AOD measurements
25+ locations in CO
Analyzed PM2.5 and AOD
GEOS-Chem run specifications
Coarse Grid
Version: v12.0.3
Run type: Global - Aerosol Only
Resolution: 4ox5o
Run time: 10/01/ /01/2018
Output: hourly global
Nested Grid
Run type: North American - Aerosol Only
Resolution: 0.25ox0.3125o
Run time: 10/21/ /01/2018
Output: hourly, species-specific AOD and PM over Colorado
GEOS-Chem output from a nested grid
Nested 0.25ox0.3125o grid output
Denver, CO
GEOS-Chem shows high PM and AOD over the Front Range, CO
Modeling challenge: large gradients due to topography and urban centers
Instrumental design objectives
Develop lower-cost sensor to measure both PM2.5 and AOD.
Deploy a network of these sensors in a variety of environments in order to capture sub-grid scale variability of PM2.5:AOD.
Data objectives
Compare network measurements of AOD and PM2.5 to satellites and reference monitors.
Compare network PM2.5:AOD to GEOS-Chem model PM2.5:AOD.
Improve use of modeled PM2.5:AOD for deriving satellite estimates of PM2.5 using parameterizations
[Ford et al., 2019]
4. GEOS-Chem shows low correlation to the CEAMS network and is unable to capture high spatial variability
5. Future Work
The spatial patterns of AOD across the Front Range, CO
The spatial patterns of PM2.5 across the Front Range, CO
GEOS-Chem and AMOD Average 48-hr PM2.5, December 9th-11th, 2017
Improvements to the CEAMS Device (currently underway)
Average GEOS-Chem and AMOD midday AOD, December 9th, 2017
Install solar tracker for automated AOD measurements (higher temporal variability)
Wi-Fi capabilities (simple data upload)
Larger batteries (longer measurement times)
CEAMS network measured high spatial variability of AOD over Fort Collins.
GEOS-Chem is unable to capture the variability that occurs at sub-grid scale.
GEOS-Chem AOD consistently under predicts the CEAMS network AOD.
Low correlation between AMODs and GEOS-Chem AOD
No obvious relationship between aerosol source/size and the agreement of AMODs and GEOS-Chem
CEAMS network measured high spatial variability of PM2.5 over Fort Collins.
GEOS-Chem is unable to capture the variability that occurs at sub-grid scale.
Consistently low PM2.5 concentrations in GEOS-Chem and the CEAMS network during the wintertime in Fort Collins.
Low correlation between Plantower (on AMODs) and GEOS-Chem PM2.5
Fort Collins
Fort Collins
Future Deployments
We will recruit more citizen scientists in order to complete three major deployments over the next three years in the following areas:
Denver, CO (urban, mountainous, wildfires)
Los Angeles, CA (polluted urban and coastal)
Washington/Idaho (rural air mass with wildfires)
Greeley
Greeley
Loveland
Loveland
Evaluate PM2.5:AOD ratios
Evaluate GEOS-Chem representation of these values
Compare CEAMS data to other in situ measurements and satellite observations (MODIS, MISR, and eventually MAIA and TEMPO)
Developing Parameterizations
Is there agreement between GEOS-Chem and the CEAMS network AOD?
Is there agreement between GEOS-Chem and CEAMS surface PM2.5?
Identify regional or emission source specific drivers of spatial/temporal PM2.5:AOD variability
Parameterize variability using high-resolution emission fields, meteorology, and land surface features as inputs in order to improve model estimates of PM2.5:AOD and improve satellite-derived PM2.5 estimates
Acknowledgements and References
This work was supported by NASA grant NNX17AF94A and 80NSSC18M0120
[1] Cohen et al. (2017): Estimates and 25-year trends of the global burden of disease attributable to ambient air pollution: an analysis of data from the Global Burden of Diseases Study The Lancet, 389(10082), 1907–1918.
[2] Liu, Y., et al. ( 2004): Mapping annual mean ground‐level PM2.5 concentrations using Multiangle Imaging Spectroradiometer aerosol optical thickness over the contiguous United States, J. Geophys. Res., 109, D22206.
[3] Wendt, E., et al. (2019): A Low-Cost Monitor for Simultaneous Measurement of Fine Particulate Matter and Aerosol Optical Depth, Atmos. Meas. Tech. Discuss, in review.
[4] Ford, B., et al. (2019): A low-cost monitor for measurement of fine particulate matter and aerosol optical depth. Part 2: Citizen science pilot campaign in northern Colorado, Atmos. Meas. Tech. Discuss., in review.