[Spatial and Temporal Characteristics of Air Quality and Cause Analysis of Heavy Pollution in Northeast China].

Northeastern China experiences severe atmospheric pollution, with an increasing occurrence of heavy haze episodes. Based on ground monitoring data, satellite products and meteorological products of atmospheric pollutants in northeast China from 2013 to 2017, the characteristics of spatial and temporal distribution of air quality and the causes of heavy haze events in northeast China were discussed. It was found that the "Shenyang-Changchun-Harbin" city belt was the most polluted area in the region on an annual scale. The spatial distribution of air quality index (AQI) values had a clear seasonality, with the worst pollution occurring in winter, an approximately oval-shaped polluted area around western Jilin Province in spring, and the best air quality occurring in summer and most of autumn. The three periods that typically experienced intense haze events were Period I from late-October to early-November (i. e., late autumn and early winter), Period Ⅱ from late-December to January (i. e., the coldest time in winter), and Period Ⅲ from April to mid-May (i. e., spring). During Period I, strong PM2.5 emissions from seasonal crop residue burning and coal burning for winter heating were the dominant reasons for the occurrence of extreme haze events (AQI>300). Period Ⅱ had frequent heavy haze events (200 < AQI < 300) in the coldest months of January and February(200 < AQI < 300), which were due to high PM2.5 emissions from coal burning and vehicle fuel consumption, a lower atmospheric boundary layer, and stagnant atmospheric conditions. Haze events in Period Ⅲ, with high PM10 concentrations, were primarily caused by the regional transportation of windblown dust from degraded grassland in central Inner Mongolia and bare soil in western Jilin Province. Local agricultural tilling could also release PM10 and enhance the levels of windblown dust from tilled soil.

Assessing Spatial and Temporal Patterns of Observed Ground-level Ozone in China.

Elevated ground-level ozone (O3), which is an important aspect of air quality related to public health, has been causing increasing concern. This study investigated the spatiotemporal distribution of ground-level O3 concentrations in China using a dataset from the Chinese national air quality monitoring network during 2013-2015. This research analyzed the diurnal, monthly and yearly variation of O3 concentrations in both sparsely and densely populated regions. In particular, 6 major Chinese cities were selected to allow a discussion of variations in O3 levels in detail, Beijing, Chengdu, Guangzhou, Lanzhou, Shanghai, and Urumchi, located on both sides of the Heihe-Tengchong line. Data showed that the nationwide 3-year MDA8 of ground-level O3 was 80.26 µg/m3. Ground-level O3 concentrations exhibited monthly variability peaking in summer and reaching the lowest levels in winter. The diurnal cycle reached a minimum in morning and peaked in the afternoon. Yearly average O3 MDA8 concentrations in Beijing, Chengdu, Lanzhou, and Shanghai in 2015 increased 12%, 25%, 34%, 22%, respectively, when compared with those in 2013. Compared with World Health Organization O3 guidelines, Beijing, Chengdu, Guangzhou, and Shanghai suffered O3 pollution in excess of the 8-hour O3 standard for more than 30% of the days in 2013 to 2015.

[The research on remote sensing dust aerosol by using split window emissivity].

Dust aerosol can cause the change in the land surface emissivity in split window by radiative forcing (RF). Firstly, the present paper explained from the microscopic point of view the extinction properties of dust aerosols in the 11 and 12 microm channels, and their influence on the land surface emissivity. Secondly, on April 29, 2011, in the northern region of Inner Mongolia a strong sandstorm outbroke, and based on the analysis of the changes in land surface emissivity, this paper proposed a dust identification method by using the variation of emissivity. At last, the dust identification result was evaluated by the dust monitoring product provided by the National Satellite Meteorological Center. The result shows that under the assumption that the 12 microm emissivity equals to 1, using 11 microm relative emissivity could identify dust cover region effectively, and the 11 microm relative emissivity to a certain extent represented the intensity information of dust aerosol.

[Simulation and analysis of polarization characteristics for real sea surface sunglint].

The sea surface sunglint is caused by specular reflectance. Water is a kind of dark target with a very low reflectance, so sunglint becomes a big noise in the aerial or aerospace remote sensing images; sunglint is strongly polarized, and can be a natural standard light source for polarized sensor in-flight calibration; sunglint also can be utilized to retrieve gaseous constituents and aerosol properties. For both de-noising and being standard light source, the radiative physic parameters should be calculated accurately. First, A 3-D sea surface model was constituted according to the Cox & Munk model; Second, the polarized radiative model of sunglint was deduced based on the 3-D sea surface model and polarized Fresnel reflectance law; Third, the sensitivities of solar-viewing relative azimuth, zenith, wind speed and wind direction were analyzed utilizing the polarized radiative model. The polarization characteristics analysis of sunglint provides a theoretical basis for the quantitative remote sensing retrievals which uses sunglint.