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首页> 外文期刊>Atmospheric chemistry and physics >Measurements of aerosol absorption and scattering in the Mexico City Metropolitan Area during the MILAGRO field campaign: a comparison of results from the T0 and T1 sites
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Measurements of aerosol absorption and scattering in the Mexico City Metropolitan Area during the MILAGRO field campaign: a comparison of results from the T0 and T1 sites

机译：在MILAGRO野战期间在墨西哥城都会区测量气溶胶吸收和散射：比较T0和T1站点的结果

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In March 2006, a multiagency field campaign was undertaken in Mexico Citycalled the Megacities Initiative: Local and Global Research Observations(MILAGRO). Two of the five field components of the MILAGRO study focused amajor part of their efforts on atmospheric particulate emissions from theMexico City basin and their effects on radiative balance as a function oftime, location and processing conditions. As part of these two MILAGROcomponents, measurements of aerosol optical properties were obtained at asite located in the northern part of Mexico City (T0) and also at a sitelocated 29 km northwest (T1) to estimate the regional effects ofaerosol emissions from the basin.Measurements of aerosol absorption and scattering for fine mode aerosolswere obtained at both sites. Aerosol absorption at 550 nm was similar atboth sites, ranging from 7–107 Mm−1 at T0 and from 3–147 Mm−1 at T1. Aerosol scattering measured at 550 nm at T0 ranged from16–344 Mm−1 while the aerosol scattering values at T1 were much lowerthan at T0 ranging from 2–136 Mm−1. Aerosol single scattering albedos(SSAs) were calculated at 550 nm for the fine mode aerosols at both sitesusing these data. The SSAs at T0 ranged from 0.47–0.92 while SSAs at T1ranged from 0.35–0.86. The presence of these highly absorbing fine aerosolsin the lower atmosphere of the Mexico City area will result in a positiveclimate forcing and a local warming of the boundary layer in the region.Broadband UVB intensity was found to be higher at site T0, with an averageof 64 μW/cm2 at solar noon, than at site T1, which had an averageof 54 μW/cm2 at solar noon. Comparisons of clear-sky modeled UVBintensities with the simultaneous UVB measurements obtained at sites T0 andT1 for cloudless days indicate a larger diffuse radiation field at site T0than at site T1. The determination of aerosol ?ngstrom scatteringcoefficients at T0 suggests that this is due to the predominance of aerosolsin the size range of 0.3 micron, which leads to scattering of UVB radiationpeaked in the forward direction and to an enhanced UVB radiation observed atground level. This enhancement of the UVB diffuse radiation field wouldexplain the enhanced photochemistry observed in the Mexico City area despitethe reduction in UVB anticipated from light absorbing species.
机译：2006年3月，在墨西哥城开展了一次跨机构的野外运动，称为“大城市倡议：本地和全球研究观察”（MILAGRO）。 MILAGRO研究的五个现场组成部分中有两个集中了大部分工作，重点是墨西哥城盆地的大气颗粒物排放以及它们对辐射平衡的影响，这些影响是时间，位置和加工条件的函数。作为这两种MILAGRO组件的一部分，在位于墨西哥城北部（T0）的地点和位于西北29公里（T1）的地点进行了气溶胶光学特性的测量，以估算盆地中气溶胶排放的区域效应。在两个位置均获得了精细模式气溶胶的气溶胶吸收和散射测量。 550 nm处的气溶胶吸收相似，在T0处为7–107 Mm -1 ，在T1处为3–147 Mm -1 。在T0在550 nm处测量的气溶胶散射范围为16–344 Mm -1 ，而在T1处的气溶胶散射值远低于在T0处的2–136 Mm -1 。使用这些数据，在两个位置上针对精细模式气溶胶在550 nm处计算了气溶胶单散射反照率（SSA）。 T0时的SSA范围为0.47-0.92，而T1时的SSA范围为0.35-0.86。在墨西哥城地区较低的大气层中，这些高吸收性细小气溶胶的存在将导致正气候强迫和该区域边界层的局部变暖。 发现宽带UVB强度在现场较高T0在太阳正午时的平均值为64μW/ cm 2 ，而在太阳正午时的站点T1的平均值为54μW/ cm 2 。晴空建模的UVB强度与在地点T0和T1获得的同时无云天的同时测量UVB的比较表明，地点T0处的散射辐射场比地点T1更大。在T0时确定的气溶胶纤度散射系数表明，这是由于气溶胶占主导地位，尺寸范围为0.3微米，这导致了正向传播的UVB辐射发生散射，并导致地面上观察到的UVB辐射增强。 UVB漫射场的这种增强将解释在墨西哥城地区观察到的光化学增强，尽管预计吸光物种会降低UVB。

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