[1] Moderate Resolution Imaging Spectroradiometer (MODIS) measurements (7 channels: 0.47-2.1 mm, 250-500 m resolutions) provide us with new insights into the characteristics of global aerosols. MODIS retrieves not only aerosol loading but also the fraction of fine mode particle. In this paper we demonstrate MODIS capability for use in monitoring global, regional, and local air pollution. Three case studies in northern Italy, Los Angeles, and Beijing showed the conclusive results of applying MODIS-derived aerosol optical depths (t a ) to regional and local air pollution in terms of accuracy (Át a = ±0.05 ± 0.2t a ) and spatial sensitivity of the retrievals. Under stagnant condition, accumulated aerosol abundance can reach t a > 1 (at 0.55 mm) before being removed by wind or precipitation. The correlation found between Aerosol Robotic Network (AERONET) daily averaged t a and 24-hour PM 10 (particulate matter with diameter <10 mm) concentration (mg/m 3 ) in northern Italy is encouraging with correlation coefficient $0.82. The derivation of PM concentration from satellite measurements may be possible once we know the detailed aerosol vertical distribution. To compare aerosol loading in different regions of the globe, we choose the two most populated regions (eastern China and India) and the two most industrialized regions (the eastern United States/Canada and western Europe). The time series of MODIS monthly mean t a from

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Background: Epidemiologic evidence for a causative association between black carbon (BC) and health outcomes is limited.Objectives: We estimated associations and exposure–response relationships between acute respiratory inflammation in schoolchildren and concentrations of BC and particulate matter with an aerodynamic diameter of ≤ 2.5 μm (PM2.5) in ambient air before and during the air pollution intervention for the 2008 Beijing Olympics.Methods: We measured exhaled nitric oxide (eNO) as an acute respiratory inflammation biomarker and hourly mean air pollutant concentrations to estimate BC and PM2.5 exposure. We used 1,581 valid observations of 36 subjects over five visits in 2 years to estimate associations of eNO with BC and PM2.5 according to generalized estimating equations with polynomial distributed-lag models, controlling for body mass index, asthma, temperature, and relative humidity. We also assessed the relative importance of BC and PM2.5 with two-pollutant models.Results: Air pollution concentrations and eNO were clearly lower during the 2008 Olympics. BC and PM2.5 concentrations averaged over 0–24 hr were strongly associated with eNO, which increased by 16.6% [95% confidence interval (CI), 14.1–19.2%] and 18.7% (95% CI, 15.0–22.5%) per interquartile range (IQR) increase in BC (4.0 μg/m3) and PM2.5 (149 μg/m3), respectively. In the two-pollutant model, estimated effects of BC were robust, but associations between PM2.5 and eNO decreased with adjustment for BC. We found that eNO was associated with IQR increases in hourly BC concentrations up to 10 hr after exposure, consistent with effects primarily in the first hours after exposure.Conclusions: Recent exposure to BC was associated with acute respiratory inflammation in schoolchildren in Beijing. Lower air pollution levels during the 2008 Olympics also were associated with reduced eNO.

[1] Aerosol vertical distribution is an important piece of information to improve aerosol retrieval from satellite remote sensing. Aerosol extinction coefficient profile and its integral form, aerosol optical depth (AOD), as well as atmospheric boundary layer (ABL) height and haze layer height can be derived using lidar measurements. In this paper, we used micropulse lidar measurements acquired from May 2003 to June 2004 to illustrate seasonal variations of AOD and ABL height in Hong Kong. On average, about 64% of monthly mean aerosol optical depths were contributed by aerosols within the mixing layer (with a maximum ($76%) in November and a minimum ($55%) in September) revealing the existence of large abundance of aerosols above ABL due to regional transport. The characteristics of seasonal averaged aerosol profiles over Hong Kong in the study period are presented to illustrate seasonal phenomena of aerosol transport and associated meteorological conditions. The correlation between AOD and surface extinction coefficient, as found, is generally poor (r 2 $0.42) since elevated aerosol layers increase columnar aerosol abundance but not extinction at surface. The typical aerosol extinction profile in the ABL can be characterized by a low value near the surface and values increased with altitude reaching the top of ABL. When aerosol vertical profile is assumed, surface extinction coefficient can be derived from AOD using two algorithms, which are discussed in detail in this paper. Preliminary analysis showed that better estimates of the extinction coefficient at the ground level could be obtained using two-layer aerosol extinction profiles (r 2 $0.78, slope $0.82, and intercept $0.15) than uniform profiles of extinction with height within the ABL (r 2 $0.65, slope $0.27, and intercept $0.03). The improvement in correlation is promising on mapping satellite retrieved AOD to surface aerosol extinction coefficient for urban and regional environmental studies on air quality related issues.Citation: He, Q

The planetary boundary layer height (PBLH) is a very important parameter in the atmosphere, because it determines the range where the most effective dispersion processes take place, and serves as a constraint on the vertical transport of heat, moisture, and pollutants. As the only space‐borne lidar, Cloud‐Aerosol Lidar with Orthogonal Polarization onboard Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) measures the vertical distribution of aerosol signals and thus offers the potential to retrieve large‐scale PBLH climatology. In this study, we explore different techniques for retrieving PBLH from CALIPSO measurements and validate the results against those obtained from ground‐based micropulse lidar (MPL) and radiosonde (RS) data over Hong Kong, where long‐term MPL and RS measurements are available. Two methods, namely maximum standard deviation (MSD) and wavelet covariance transform (WCT), are used to retrieve PBLH from CALIPSO. Results show that the RS‐ and MPL‐derived PBLHs share similar interannual variation and seasonality and can complement each other. Both MSD and WCT perform reasonably well compared with MPL/RS products, especially under sufficient aerosol loading. Uncertainties increase when aerosol loading is low and the CALIPSO signal consequently becomes noisier. Overall, CALIPSO captures the general PBLH seasonal variability over Hong Kong, despite a high bias in spring and a low bias in summer. The spring high bias is likely associated with elevated aerosol layers due to transport, while the summer low bias can be attributed to higher noise level associated with weaker aerosol signal.