Abstract
Abstract. Convective clouds are common and play a major role in Earth's water cycle and energy balance; they may even develop into storms and cause severe rainfall events. To understand the convective cloud development process, this study investigates the impact of aerosols on convective clouds by considering the influence of both topography and diurnal variation in radiation. By combining texture analysis, clustering, and thresholding methods, we identify all convective clouds in two warm seasons (May–September, 2016/17) in eastern China based on Himawari-8 Level 1 data. Having large diurnally resolved cloud data together with surface meteorological and environmental measurements, we investigate convective cloud properties and their variation, stratified by elevation and diurnal change. We then analyze the potential impact of aerosol on convective clouds under different meteorological conditions and topographies. In general, convective clouds tend to occur preferentially under polluted conditions in the morning, which reverses in the afternoon. Convective cloud fraction first increases then decreases with aerosol loading, which may contribute to this phenomenon. Topography and diurnal meteorological variations may affect the strength of aerosol microphysical and radiative effects. Updraft is always stronger along the windward slopes of mountains and plateaus, especially in northern China. The prevailing southerly wind near the foothills of mountains and plateaus is likely to contribute to this windward strengthening of updraft and to bring more pollutant into the mountains, thereby strengthening the microphysical effect, invigorating convective clouds. By comparison, over plain, aerosols decrease surface heating and suppress convection by blocking solar radiation reaching the surface.
Highlights
Convective clouds are important for Earth’s energy balance and the water cycle
Similar results were found by previous studies (Guo et al, 2017; Jiang et al, 2018; Wang et al, 2018). Adding to these previous results, we find that the relationship of PM2.5 and convective cloud fraction (CCF) persists throughout the day, as we have used highresolution geostationary satellite data that provide us ample samples at different times
We find that the CCF difference between polluted and clean conditions generally agrees with Fig. 7 in that CCFP is higher in the morning and lower in the afternoon, and the differences are statistically greatest in early morning and late afternoon
Summary
Convective clouds are important for Earth’s energy balance and the water cycle. Changes in the distribution or triggering time of convective cloud can have a large impact on the climate system (IPCC, 2013). Previous studies have shown that aerosol particles in the atmosphere can affect the formation and development of convective clouds, through both radiative and microphysical effects (Ramanathan et al, 2001; Tao et al, 2012; Altaratz et al, 2014; Rosenfeld et al, 2014a, b; Li et al, 2016; Zhao et al, 2018a; Yang et al, 2019), which can dramatically affect the weather and climate (Zhao et al, 2020). T. Chen et al.: Potential impact of aerosol on convective clouds over different terrain types
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