Time series of satellite-based fine particulate matter (PM2.5) concentrations

over China: 2004-2012

Guannan Geng, Qiang Zhang, Aaron van Donkelaar, Randall V. Martin, and Kebin He

2013-12-11, San Francisco

Sources and negative effects of fine particles (PM2.5)

ClimateBrown CloudAcid rainHazeHealth

Increased morbidity and mortality from bothacute and chronic exposure to ambient fineparticulate matter (PM2.5)

fine particulate matters in the (ambient) air with 2.5 micrometers or less in size

Regional haze is a major concern in China

Beijing haze

Primary pollutants in 74 cities (2013.1-10)

PM2.5 concentration

(2013.1-10)

Heavy PM2.5 pollution occurs in China, especially in the North China Plain

How has PM2.5 evolved over the past decade over China?

• Long-term variation of PM2.5 concentrations is important for epidemiological studies.

• China has developed control strategies for the precursors of PM2.5, e.g. SO2 and NOx.

• But ground measurements are limited in China– Only several research groups have monitored the ground level

PM2.5 concentration before the year 2013.– National network of PM2.5 monitoring is built up since 2013.

Satellite Remote sensing approach can be used to enhance our ability to estimate PM2.5 concentration

• Many works have used aerosol optical depth (AOD) to retrieve PM2.5 concentration

• In this study, ground-level PM2.5 concentrations for the period 2004-2012 over China are estimated using CTM to provide the conversion factor between PM2.5 and AOD.

𝑷𝑴𝟐 .𝟓= 𝒇 (𝑨𝑶𝑫 )Multiple linear regression

Chemical transport model

Satellite-derived surface PM2.5

van Donkelaar et al, EHP, 2010van Donkelaar et al, JGR, 2013

𝑨𝑶𝑫 𝒔𝒂𝒕𝒆𝒍𝒍𝒊𝒕𝒆×𝑷𝑴𝟐 .𝟓𝒎𝒐𝒅𝒆𝒍𝒆𝒅

𝑨𝑶𝑫𝒎𝒐𝒅𝒆𝒍𝒆𝒅

GEOS-Chem (GC)

𝑷𝑴𝟐 .𝟓𝒔𝒂𝒕𝒆𝒍𝒍𝒊𝒕𝒆

PM2.5 AOD

MISR CALIPSO

AOD Vertical Profile

emissionsMEIC

Emission trends of the precursors in China

• The MEIC inventory, 2004-2012

Evaluation of model simulationsSNA simulation in the year of 2006

Modeled AOD trend compared with MISR

Slope = 0.28, R = 0.32Slope = 0.26, R = 0.33Slope = 0.19, R = 0.17Slope = 0.85, R = 0.39

Slope = 0.44, R = 0.81Slope = 0.52, R = 0.78Slope = 0.68, R = 0.71Slope = 0.86, R = 0.88

Slope = 0.58, R = 0.66Slope = 0.79, R = 0.82Slope = 0.64, R = 0.49Slope = 0.93, R = 0.74

Satellite-based PM2.5 retrieved from MISR AOD

Trends of the conversion factor and MISR AOD

Modeled PM2.5 Modeled PM2.5/AOD

MISR AOD

Modeled AOD

The population weighted national annual mean PM2.5 trends over China during 2004-2012

104

PM2.5 trends of some cities in China

The effect of the correlation slope between modeled and satellite AOD on PM2.5 trend

Conclusions

• National scale surface PM2.5 concentration derived from MISR increased from 2004 to 2006 and started to decrease around 2006-2007, and had a second small peak in 2011. The trend between 2004 and 2012 was +0.5 ug·m-3·yr-1.

• In the Northern China, there are mostly increasing trends, even above 4 ug·m-3·yr-1 in some regions. While in the Southern China, PM2.5 decreased in 2012 compared to 2004.

• PM2.5 concentrations in some megacities have started to decrease slightly.

Thank you!