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PM2.5 over North China based on MODIS AOD and effect of meteorological elements during 2003‒2015

Youfang Chen, Yimin Zhou, Xinyi Zhao

《环境科学与工程前沿(英文)》 2020年 第14卷 第2期 doi: 10.1007/s11783-019-1202-8

摘要: The Taihang Mountains was the boundary between high and low pollution areas. There were one high value center for PM2.5 pollution and two low value centers. In 2004, 2009 and after 2013, PM2.5 concentration was relatively low. Over the past 40 years, PM2.5 pollution in North China has become increasingly serious and progressively exposes the densely populated areas to pollutants. However, due to limited ground data, it is challenging to estimate accurate PM2.5 exposure levels, further making it unfavorable for the prediction and prevention of PM2.5 pollutions. This paper therefore uses the mixed effect model to estimate daily PM2.5 concentrations of North China between 2003 and 2015 with ground observation data and MODIS AOD satellite data. The tempo-spatial characteristics of PM2.5 and the influence of meteorological elements on PM2.5 is discussed with EOF and canonical correlation analysis respectively. Results show that overall R2 is 0.36 and the root mean squared predicted error was 30.1 μg/m3 for the model prediction. Our time series analysis showed that, the Taihang Mountains acted as a boundary between the high and low pollution areas in North China; while the northern part of Henan Province, the southern part of Hebei Province and the western part of Shandong Province were the most polluted areas. Although, in 2004, 2009 and dates after 2013, PM2.5 concentrations were relatively low. Meteorological/topography conditions, that include high surface humidity of area in the range of 34°‒40°N and 119°‒124°E, relatively low boundary layer heights, and southerly and easterly winds from the east and north area were common factors attributed to haze in the most polluted area. Overall, the spatial distribution of increasingly concentrated PM2.5 pollution in North China are consistent with the local emission level, unfavorable meteorological conditions and topographic changes.

关键词: Aerosol optical depth     PM2.5     MODIS     Mixed effect model     Canonical correlation analysis    

Integrating space and time: a case for phenological context in grazing studies and management

Dawn M. BROWNING, Sheri SPIEGAL, Richard E. ESTELL, Andres F. CIBILS, Raul H. PEINETTI

《农业科学与工程前沿(英文)》 2018年 第5卷 第1期   页码 44-56 doi: 10.15302/J-FASE-2017193

摘要: In water-limited landscapes, patterns in primary production are highly variable across space and time. Livestock grazing is a common agricultural practice worldwide and a concern is localized overuse of specific pasture resources that can exacerbate grass losses and soil erosion. On a research ranch in New Mexico with average annual rainfall of 217 mm, we demonstrate with a quantitative approach that annual seasons vary greatly and examine foraging patterns in Angus-Hereford ( ) cows. We define five seasonal stages based on MODIS NDVI: pre-greenup, greenup, peak green, drydown and dormant, and examine livestock movements in 2008. Daily distance traveled by cows was greater and foraging area expanded during periods with higher precipitation. A regression model including minimum NDVI, rainfall and their interaction explained 81% of the seasonal variation in distance traveled by cows ( <0.01). Cows explored about 81 ha·d while foraging, but tended to explore smaller areas as the pasture became greener (greenup and peak green stages). Cows foraged an average of 9.7 h daily and spent more time foraging with more concentrated search patterns as pastures became greener. Our findings suggest that phenological context can expand the capacity to compare and integrate findings, and facilitate meta-analyses of grazing studies conducted at different locations and times of year.

关键词: GPS collars     Jornada Experimental Range     land-surface phenology     livestock movement     LTAR     MODIS NDVI     rangeland    

标题 作者 时间 类型 操作

PM2.5 over North China based on MODIS AOD and effect of meteorological elements during 2003‒2015

Youfang Chen, Yimin Zhou, Xinyi Zhao

期刊论文

Integrating space and time: a case for phenological context in grazing studies and management

Dawn M. BROWNING, Sheri SPIEGAL, Richard E. ESTELL, Andres F. CIBILS, Raul H. PEINETTI

期刊论文