Spatial features of rain frequency change and pollution and associated aerosols (original) (raw)
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Asia-Pacific Journal of Atmospheric Sciences, 2010
We investigated the regional-scale relationships between columnar aerosol loads and summer monsoon circulation, and also the precipitation over northeast Asia using aerosol optical depth (AOD) data obtained from the 8-year MODIS, AERONET Sun/sky radiometer, and precipitation data acquired under the Global Precipitation Climatology Project (GPCP). These high-quality data revealed the regional-scale link between AOD and summer monsoon circulation, precipitation in July over northeast Asian countries, and their distinct spatial and annual variabilities. Compared to the mean AOD for the entire period of 2001-2008, the increase of almost 40-50% in the AOD value in July 2005 and July 2007 was found over the downwind regions of China (Yellow Sea, Korean peninsula, and East Sea), with negative precipitation anomalies. This can be attributable to the strong westerly confluent flows, between cyclone flows by continental thermal low centered over the northern China and anticyclonic flows by the western North Pacific High, which transport anthropogenic pollution aerosols emitted from east China to aforementioned downwind high AOD regions along the rim of the Pacific marine airmass. In July 2002, however, the easterly flows transported anthropogenic aerosols from east China to the southwestern part of China in July 2002. As a result, the AOD off the coast of China was dramatically reduced in spite of decreasing rainfall. From the calculation of the cross-correlation coefficient between MODIS-derived AOD anomalies and GPCP precipitation anomalies in July over the period 2001-2008, we found negative correlations over the areas encompassed by 105-115 o E and 30-35 o N and by 120-140 o E and 35-40 o N (Yellow Sea, Korean peninsula, and East Sea). This suggests that aerosol loads over these regions are easily influenced by the Asian monsoon flow system and associated precipitation.
Seasonal and Regional Characteristics of Aerosol Pollution in East and Southeast Asia
Frontiers in Environmental Science
The atmospheric aerosol distribution in Asia is complex because it is influenced by both natural phenomena and human activities. In this article, multifaceted approach using satellite observations and numerical model simulation shows seasonal and regional variations of the aerosol distribution over Asia. Asia covers a large area; however, this article is limited to East and Southeast Asia. The aerosol optical thickness (AOT) in the inland desert area is normally high in spring and dusty aerosols are widely spread with the wind. The AOT values are high in summer over East Asia. A high AOT caused by biomass burning plumes is observed in autumn over Southeast Asia and in spring over Siberia and heavy air pollution occurs in Beijing in winter, a very well-known phenomenon. These phenomena caused by heavy aerosol concentration were determined based on Aqua/MODIS data and aerosol characteristics retrievals and estimated the aerosol characteristics. Furthermore, the impact of aerosols on the climate assessed by numerical model simulations suggest that aerosols reduce solar radiation and therefore the Earth's surface temperature. In addition to these influences on the radiation budget, aerosols have a significant potential to change the circulation fields.
Environmental Pollution, 2019
Satellite observations for regional air quality assessment rely on comprehensive spatial coverage, and daily monitoring with reliable, cloud-free data quality. We investigated spatiotemporal variation and data quality of two global satellite Aerosol Optical Depth (AOD) products derived from MODIS and VIIRS imagery. AOD is considered an essential atmospheric parameter strongly related to ground Particulate Matter (PM) in Southeast Asia (SEA). We analyze seasonal variation, urban/rural area influence, and biomass burning effects on atmospheric pollution. Validation indicated a strong relationship between AERONET ground AOD and both MODIS AOD (R 2 ¼ 0.81) and VIIRS AOD (R 2 ¼ 0.68). The monthly variation of satellite AOD and AERONET AOD reflects two seasonal trends of air quality separately for mainland countries including Myanmar,
A six year satellite-based assessment of the regional variations in aerosol indirect effects
Atmospheric Chemistry and Physics - ATMOS CHEM PHYS, 2009
Since aerosols act as cloud condensation nuclei (CCN) for cloud water droplets, changes in aerosol concentrations having significant impacts on the corresponding cloud properties. An increase in aerosol concentration leads to an increase in CCN, with an associated decrease in cloud droplet size for a given cloud liquid water con-5 tent. Smaller droplet sizes may then lead to a reduction in precipitation efficiency and an increase in cloud lifetimes, which induces more reflection of solar radiation back into space, cooling the atmosphere below the cloud layer. In reality, this relationship is much more complex and is interrelated between aerosol, cloud, and atmospheric conditions present at any one time. MODIS aerosol and cloud properties are com-10 bined with NCEP Reanalysis data for eight different regions around the globe between March 2000 and December 2005 to study the effects of different aerosol, cloud, and atmospheric conditions on the aerosol indirect effect (AIE). The first AIE for both anthropogenic and dust aerosols is calculated so that the importance of each can be compared. The unique aspect of this research is that it combines multiple satellite data 15 sets over a six year period to provide a comprehensive analysis of indirect effects for different aerosol regimes around the globe.
Urban air pollution is rapidly becoming an environmental problem of public concern worldwide. It can influence public health and local/regional weather and climate. In the present study, the washout effect of rain on surface air pollutants (PM 2.5 , O 3 , NO x , NO 2 , NO ,SO 2 , and CO) has been investigated over three ambient air quality monitoring stations (Gurugram, Rohtak and Panchkula) in Haryana state in Northern India. The airborne particulate pollutants data were collected by the Haryana State Pollution Control Board (HSPCB) for a period of one year (January 01, 2016 to December 31, 2016) at Vikash Sadan location in Gurugram, MDU location in Rohtak and HSPCB Sector 6 location in Panchkula.. The rainfall data for the study period has been taken from rainfall Statistics in India-2016, India Meteorological Department. The regression correlation analysis has been performed to investigate the effect of rainfall on surface air pollutants. The concentration of air pollutants are found to decrease with increase of rainfall. It has been observed that, PM 2.5 is most effected and O 3 is least effected by rainfall. Most of the pollutants under study show statistically significant negative correlations between their concentrations and rainfall due to washout and convection but their sensitivity towards rain significantly varies. O 3 shows either positive correlation or weak negative correlation with rainfall depending on the meteorological season and observing site.
Proceedings of the ICA
Precipitation is one of the main stages of the water cycle, and it is required for the organisms to survive on the planet. In contrast, air pollution is a phenomenon that has greatly affected the human life nowadays. Population growth, development of factories and increasing number of fossil fuel vehicles are the most influencing factors on air pollution. In addition to understand nature of precipitation and air pollution, finding relationship between these two phenomena is necessary to make appropriate policies for reducing air pollution. Furthermore, studying trends of precipitation and air pollution in the past, is helpful to forecast the times and places with less precipitation and more air pollution for a better urban management. In this study, we tried to extract any probable relationship between these two parameters by investigating their monthly measured amounts in 22 municipal districts of Tehran in three epochs of time (2009, 2013 and 2017). Carbon Monoxide (CO) was considered as the indicator of air pollution. Results of the study show that the parameters have a significant relationship with each other. By using Pearson Correlation Coefficient and One-Way Variance (ANOVA) test, relationship between the data for each month and for each district of Tehran were studied separately. As the time has passed and the air pollution has increased, the correlation between the parameters in districts has decreased. In addition, during the cold months of the year, the correlations decrease since the fact that precipitation is not the only influencing factor on the air pollution due to the rise of air "Inversion". Finally, the polynomial regression model of carbon monoxide based on precipitation was extracted for each of the three years. The model suggests a degree three polynomial equation. The obtained coefficients from the regression model show that the relationship between parameters was stronger in the years with more rainfalls. This can be due to the more significant impact of other influencing factors on air pollution, such as population density, wind direction, vehicles and factories in the areas or conditions with a less rainfall.
Research on atmospheric aerosols has become an important component in atmospheric studies due to its tremendous implications to radiation budget, climate change, hydrological and carbon cycles. Several recent studies have analysed the spatio-temporal patterns of aerosols and their relationship with meteorological conditions which is essential to quantify regional and global climate changes. However, such analysis have been lacking in Malaysia although this region receives considerable amount of air pollutants from local sources and neighbouring countries. Therefore, an attempt has been undertaken in this study to analyse the spatial and temporal patterns of aerosols in Peninsular Malaysia and explore the link between aerosols and meteorological variables. More specifically the monthly periodicities in atmospheric aerosols have been analysed using aerosol optical depth (AOD) product (level 2 data) from Moderate Resolution Imaging Spectro-radiometer (MODIS) satellite data covering yea...
Aerosol Pollution Impact on Precipitation
2009
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The impact of observed precipitation upon the transport of aerosols from South Asia
Tellus B, 2004
A B S T R A C T Deposition of atmospheric aerosols by precipitation is investigated by assimilating near-global 3-hourly precipitation estimates from satellites at 0.25 • resolution into a global chemical transport model. Simulations of 21 d duration during February 2002 are performed where satellite observations of surface rain rate are incorporated into the computation of the aerosol removal rate. A steady source of a tracer simulating a soluble aerosol species is imposed on the bottom layer of the model over the Indian Subcontinent at a rate of 0.08 µg m −2 s −1 . The impacts of wet deposition by observed precipitation patterns upon regional-scale and global-scale transport of aerosols are examined. The results are compared with a model simulation where wet deposition has been turned off and a simulation which uses modelsimulated precipitation to compute wet deposition. Observed precipitation patterns are responsible for reducing aerosol amounts over the Indian Ocean basin by about 25% compared with a case with no wet deposition. Over the remainder of the Northern Hemisphere the aerosol amounts are reduced by nearly 80%. Precipitation in the region of the intertropical convergence zone (ITCZ) acts as an effective barrier to the transport of aerosol to the Southern Hemisphere. Virtually all of the wet deposition over the Indian Ocean occurs in grid cells experiencing rain rates of less than 1 mm h −1 , even though these events account for only 20% of the total precipitation observed in the region. Light-rain events to the north of the ITCZ occur frequently enough, and scavenge aerosol efficiently enough, to remove much of the aerosol before southward-moving air masses reach the ITCZ. Model-simulated precipitation over the Indian Ocean occurs more frequently than observed by satellite, by as much as 50%, and is characterized by more drizzle events and fewer heavyrain events than observed. The differences in simulated and observed rain rate distributions result in only a 6% difference in aerosol amount over the Indian Ocean, and an 8% difference over the remainder of the Northern Hemisphere. Satellite observations also reveal that rain events covering more than 80% of the horizontal area of a model grid cell occur up to an order of magnitude more frequently than predicted by a common parametrization of precipitation scavenging. A test of wet deposition based on the observed spatial coverage of surface precipitation suggests that incorrect assumptions about the physical sizes of rain events may result in as much as a factor of 2 over-estimate of the amount of aerosol transported out of the South Asia region to the remainder of the Northern Hemisphere in global atmospheric transport models.
Atmospheric Chemistry and Physics, 2008
In this study, the spatio-temporal and seasonal distributions of EOS/Terra Moderate Resolution Imaging Spectroradiometer (MODIS)-derived aerosol optical depth (AOD) over East Asia were analyzed in conjunction with US EPA Models-3/CMAQ v4.3 modeling. In this study, two MODIS AOD products (τ MODIS : τ M−BAER and τ NASA ) retrieved through a modified Bremen Aerosol Retrieval (M-BAER) algorithm and NASA collection 5 (C005) algorithm were compared with the AOD (τ CMAQ ) that was calculated from the US EPA Models-3/CMAQ model simulations. In general, the CMAQ-predicted AOD values captured the spatial and temporal variations of the two MODIS AOD products over East Asia reasonably well. Since τ MODIS cannot provide information on the aerosol chemical composition in the atmosphere, different aerosol formation characteristics in different regions and different seasons in East Asia cannot be described or identified by τ MODIS itself. Therefore, the seasonally and regionally varying aerosol formation and distribution characteristics were investigated by the US EPA Models-3/CMAQ v4.3 model simulations. The contribution of each particulate chemical species to τ MODIS and τ CMAQ showed strong spatial, temporal and seasonal vari-Correspondence to: C. H. Song (chsong@gist.ac.kr) ations. For example, during the summer episode, τ MODIS and τ CMAQ were mainly raised due to high concentrations of (NH 4 ) 2 SO 4 over Chinese urban and industrial centers and secondary organic aerosols (SOAs) over the southern parts of China, whereas during the late fall and winter episodes, τ MODIS and τ CMAQ were higher due largely to high levels of NH 4 NO 3 formed over the urban and industrial centers, as well as in areas with high NH 3 emissions. τ CMAQ was in general larger than τ MODIS during the year, except for spring. The high biases (τ CMAQ >τ MODIS ) may be due to the excessive formation of both (NH 4 ) 2 SO 4 (summer episode) and NH 4 NO 3 (fall and winter episodes) over China, possibly from the use of overestimated values for NH 3 emissions in the CMAQ modeling. According to CMAQ modeling, particulate NH 4 NO 3 made a 14% (summer) to 54% (winter) contribution to σ ext and τ CMAQ . Therefore, the importance of NH 4 NO 3 in estimating τ should not be ignored, particularly in studies of the East Asian air quality. In addition, the accuracy of τ M−BAER and τ NASA was evaluated by a comparison with the AOD (τ AERONET ) from the AERONET sites in East Asia. Both τ M−BAER and τ NASA showed a strong correlation with τ AERONET around the 1:1 line (R=0.79), indicating promising potential for the application of both the M-BAER and NASA aerosol retrieval algorithms to satellite-based air quality monitoring studies in East Asia.