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Black carbon (BC) has importance regarding aerosol composition, radiative balance, and human exposure. This study adopted a backward-trajectory approach to quantify the origins of BC from anthropogenic emissions (B C An) and open biomass burning (B C BB) transported to Xishuangbanna in 2017. Haze months, between haze and clean months, and clean months in Xishuangbanna were defined according to daily PM 2.5 concentrations of >75, 35–75, and <35 µg/m3, respectively. Results showed that the transport efficiency density (TED) of BC transported to Xishuangbanna was controlled by the prevailing winds in different seasons. The yearly contributions to the effective emission intensity of B C An and B C BB transported to Xishuangbanna were 52% and 48%, respectively. However, when haze occurred in Xishuangbanna, the average B C An and B C BB contributions were 23% and 77%, respectively. This suggests that open biomass burning (BB) becomes the dominant source in haze months. Myanmar, India, and Laos were the dominant source regions of BC transported to Xishuangbanna during haze months, accounting for 59%, 18%, and 13% of the total, respectively. Furthermore, India was identified as the most important source regions of B C An transported to Xishuangbanna in haze months, accounting for 14%. The two countries making the greatest contributions to B C BB transported to Xishuangbanna were Myanmar and Laos in haze months, accounting for 55% and 13%, respectively. BC emissions from Xishuangbanna had minimal effects on the results of the present study. It is suggested that open BB in Myanmar and Laos, and anthropogenic emissions in India were responsible for poor air quality in Xishuangbanna. [Display omitted] [ABSTRACT FROM AUTHOR]

Based on the infrared TBB from 2010 to 2014 of the geostationary meteorological satellite FY-2E, the climatic characteristics of summer convection over the Tibetan Plateau and its surrounding areas r are analyzed. The analysis shows that in May, the main convection occurred in the eastern edge of the Tibetan Plateau, and then with the Asian summer monsoon, the strongest convection (severe convection) occurs in the southeast part of the plateau part in June. In late summer, the strong southwest wind brought abundant moisture to the eastern and central area of the plateau through the topographic gap and forms a belt of convection there. In the western part of the plateau, area with convection frequency greater than 6% reaches the southern plateau at about 37th pentad, and gradually moves northward until the end of July. In the middle part of the plateau, convection (severe convection) becomes active since the early (mid) June, and maintain the whole late summer with three northward movements until reaching 34°N. Convections in the eastern part of the Tibetan Plateau is relatively active since the beginning of May and the northward stretching time is slightly later than that over the central part of the plateau. Two high intra-seasonal variability centers are located in the middle branch of the Brahmaputra and the southeastern part of the plateau. Summer convective activities are very uneven in these regions and prone to drought and flood disasters. The first leading mode of the convection frequency is the reverse mode over the Indian monsoon region and the southeastern part of the plateau while the second leading mode reflects the variation over the western part of the plateau，the India continent west of 80°E and the South Asian continent east of 80°E. [ABSTRACT FROM AUTHOR]