Modeling regional aerosol and aerosol precursor variability over California and its sensitivity to emissions and long-range transport during the 2010 CalNex and CARES campaigns
Modeling regional aerosol and aerosol precursor variability over California and its sensitivity to emissions and long-range transport during the 2010 CalNex and CARES campaigns
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DOI：
10.5194/acp-14-10013-2014
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发表时间：
2014-01-01
影响因子：
6.3
通讯作者：
Zhang, Q.
中科院分区：
文献类型：
--
作者：
Fast, J. D.;Allan, J.;Zhang, Q.
化学天气研究和预报区域模式的性能（WRF-Chem）在模拟加州上空气溶胶质量、成分和大小的时空变化时，在加州空气质量和气候实验（CalNex）和碳质气溶胶和辐射效应研究（CARES）的联系期间收集的气溶胶和气溶胶测量结果在2010年5月和6月进行。实地活动的总体目标是获得更好地了解影响气候和空气质量的过程所需的数据，包括排放评估、气溶胶的迁移和化学老化、气溶胶辐射效应。进行了模拟，审查了人为排放的气溶胶浓度的敏感性和气溶胶的远距离传输到从全球模式获得的域。在这项研究中使用的WRF-Chem的配置显示，再现整体天气条件，热驱动的环流，和边界层结构中观察到的区域，控制微量气体和气溶胶的运输和混合。将默认排放清单减少50%，导致大多数站点和沿着大多数飞机飞行路径的许多模拟痕量气体和炭黑气溶胶的总体改善;然而，当没有对主要有机气溶胶排放进行调整时，模拟有机气溶胶更接近于观察。我们发现，硫酸盐更好地模拟了北方加州，而硝酸盐更好地模拟了南加州。虽然气溶胶及其前体物的整体空间和时间变异性模拟得相当好，我们显示的情况下，一些气溶胶羽流的本地传输要么太慢或太快，这对统计数据的量化观测和模拟量之间的差异产生不利影响。与激光雷达和现场测量结果的比较表明，从全球模式的气溶胶的远程传输可能是太高的自由对流层，即使他们的浓度相对较低。这种偏差导致了气溶胶光学厚度的过度预测，高达2倍，抵消了主要由当地排放造成的边界层消光的预测不足。降低50%的气溶胶浓度的边界条件，大大减少了模拟气溶胶光学厚度的偏差为所有地区的加州。这项研究表明，量化区域尺度的气溶胶辐射强迫的变化，并确定从本地和远程源排放的相对作用是具有挑战性的“清洁”条件下，需要广泛的测量，以确保模型预测是正确的正确的原因。在这方面，结合CalNex和CARES数据集是一个理想的测试平台，可用于评估气溶胶模型非常详细，并开发改进的处理气溶胶过程。
The performance of the Weather Research and Forecasting regional model with chemistry (WRF-Chem) in simulating the spatial and temporal variations in aerosol mass, composition, and size over California is quantified using the extensive meteorological, trace gas, and aerosol measurements collected during the California Nexus of Air Quality and Climate Experiment (CalNex) and the Carbonaceous Aerosol and Radiative Effects Study (CARES) conducted during May and June of 2010. The overall objective of the field campaigns was to obtain data needed to better under-stand processes that affect both climate and air quality, including emission assessments, transport and chemical aging of aerosols, aerosol radiative effects. Simulations were performed that examined the sensitivity of aerosol concentrations to anthropogenic emissions and to long-range transport of aerosols into the domain obtained from a global model. The configuration of WRF-Chem used in this study is shown to reproduce the overall synoptic conditions, thermally driven circulations, and boundary layer structure observed in region that controls the transport and mixing of trace gases and aerosols. Reducing the default emissions inventory by 50% led to an overall improvement in many simulated trace gases and black carbon aerosol at most sites and along most aircraft flight paths; however, simulated organic aerosol was closer to observed when there were no adjustments to the primary organic aerosol emissions. We found that sulfate was better simulated over northern California whereas nitrate was better simulated over southern California. While the overall spatial and temporal variability of aerosols and their precursors were simulated reasonably well, we show cases where the local transport of some aerosol plumes were either too slow or too fast, which adversely affects the statistics quantifying the differences between observed and simulated quantities. Comparisons with lidar and in situ measurements indicate that long-range transport of aerosols from the global model was likely too high in the free troposphere even though their concentrations were relatively low. This bias led to an over-prediction in aerosol optical depth by as much as a factor of 2 that offset the under-predictions of boundary-layer extinction resulting primarily from local emissions. Lowering the boundary conditions of aerosol concentrations by 50% greatly reduced the bias in simulated aerosol optical depth for all regions of California. This study shows that quantifying regional-scale variations in aerosol radiative forcing and determining the relative role of emissions from local and distant sources is challenging during 'clean' conditions and that a wide array of measurements are needed to ensure model predictions are correct for the right reasons. In this regard, the combined CalNex and CARES data sets are an ideal test bed that can be used to evaluate aerosol models in great detail and develop improved treatments for aerosol processes.