SWAAMI (South West Asian Aerosol Monsoon Interactions)

来自印度次大陆的污染源的气溶胶颗粒在印度和孟加拉湾形成了密集而广泛的雾霾，在季风到来之前，雾霾的范围和强度都在增加。由于气溶胶（其中很大一部分来自燃烧木柴和木炭的炉灶）吸收和散射太阳辐射，它们会影响低层大气的热平衡。据推测，这种气溶胶可以通过其在季风前地区热量再分配中的作用来影响季风，模式研究表明，这种影响可能很重要。然而，目前的比较表明，与观测相比，模式间的变率和预测不足，这强烈表明，目前的模式对气溶胶特性的详细描述不足。在这些模型中缺乏气溶胶的准确表示，由于缺乏足够精度和灵敏度的测量来阐明组分质量、混合状态和光学特性等基本特性，这些特性需要很好地表征以提高模型性能，这使问题更加复杂。这限制了目前的预测能力，因此无法量化气溶胶对印度季风的影响。除了重现气溶胶的详细特性外，模式还需要能够准确地表示不同气溶胶的水平和垂直分布，以预测其影响。随着季风的发展，污染气溶胶被降水去除，但也被对流提升。从沙漠向西平流到潮湿季风气流上方的沙尘在整个季节变得非常重要。重要的是，这些气溶胶层在模型中得到准确的表示，并且有可靠的测量数据来严格挑战模型的预测。SWAAMI将通过使用英国和印度的研究飞机，在印度季风之前和期间详细确定印度各地的气溶胶物理和化学特性，为NERC-MoES联合项目“亚洲季风变化的驱动因素”做出贡献。这些测量将提供气溶胶的化学和物理特征，比以往任何测量都要详细得多，并将能够评估气溶胶的成分和混合状态，提供源特征，并提供气溶胶光学特性的量化，如消光、吸收和单散射反照率。这种详细的特征将使我们能够在区域和全球气候模式中测试气溶胶特性的表征。我们计划中的飞机测量将与来自整个大陆的长期数据和以前的实地研究相结合，以提供一个数据集，可以挑战模型如何很好地代表整个地区的气溶胶。改进模型对气溶胶特性的表示，并根据数据测试这在多大程度上提高了模型的性能，将为确保模型气溶胶方案的改进提供一个框架，这样做将使我们能够对气溶胶对该地区热预算的影响做出更可靠的预测，从而提高我们对气溶胶如何影响印度季风的认识。

Aerosol particles from pollution sources across the Indian subcontinent form a dense and extensive haze across India and the Bay of Bengal that increases in extent and magnitude in advance of the monsoon. As the aerosols, a large fraction of which arises from wood and charcoal fired cookstoves, absorb solar radiation as well as scatter it they can affect the heat balance of the lower atmosphere. It has been hypothesised that this aerosol can influence the monsoon through its role in redistribution of heat across the region in the pre-monsoon, and model studies have demonstrated that such effects can be important. However, current comparisons show model to model variability and under-prediction compared to observations, a strong indication that detailed aerosol properties are poorly represented in current models. The lack of accurate representation of aerosol in these models is compounded by a lack of measurements of sufficient accuracy and sensitivity to elucidate fundamental properties such as component mass, mixing state and optical properties, which need to be well characterised to improve model performance. This is limiting predictive capability at the present time and hence preventing the influence of aerosol in the Indian monsoon to be quantified. In addition to reproducing detailed properties of aerosol, models need to be able to accurately represent the horizontal and vertical distribution of different aerosols to predict their effects. As the monsoon progresses, pollution aerosol are removed by precipitation, but also lofted by convection. Dust advected from deserts to the west above the moist monsoonal flow become significant through the season. It is important that these aerosol layers are accurately represented in models and that robust measurements are available to rigorously challenge model predictions.SWAAMI will contribute to the joint NERC-MoES programme "Drivers of Variability in the Asian Monsoon" through a detailed determination of aerosol physical and chemical properties across India in the advance of, and during, the Indian monsoon using UK and Indian research aircraft. The measurements will deliver a chemical and physical characterisation of the aerosol that is considerably more detailed than any previous and will enable assessment of aerosol composition and mixing state, provide source characterisation and deliver quantification of aerosol optical properties such as extinction, absorption and single scattering albedo. Such detailed characterisation will allow us to test representations of aerosol properties in regional and global climate models. Our planned aircraft measurements will be combined with syntheses of long term data from across the continent and previous field studies to provide a data set that can challenge how well models represent aerosol across the region. Improving model representations of aerosol properties and testing the extent to which this improves model performance against data will provide a framework for ensuring model aerosol schemes improve and in doing so will allow us to make more reliable predictions of aerosols effects on the heat budget of the region and hence improve our knowledge of how aerosols may influence the Indian monsoon.