Abstract:The Weather Research and Forecasting model coupled to Chemistry(WRF-Chem model), coupled with an online BC source-tagging method, was used to study on the distribution, regional sources and diurnal variation of black carbon(BC) in autumn of October 2015 of Hunan and Hubei(Hunan-Hubei) basin in the middle reaches of the Yangtze river. The results show that, the contribution of local source and outside sources to BC at "Hunan-Hubei" varied greatly under different wind field conditions. In this study, there are three main BC source episodes in autumn in "Hunan-Hubei":(1)The type of import mainly controlled by north wind, with high wind speed and low BC concentration. The contribution to surface BC in "Hunan-Hubei" from upwind regions via transport was approximately 30.6%, and 61.7% from local source regions; (2)The type of stable under the condition of low surface wind speed and stable weather. The contribution of local BC was high, accounting for 79.6%; (3)The type of import mainly controlled by northeasterly wind. A high concentration of BC in "Hunan-Hubei" was maintained by the contributions from local and outside sources together, and the contribution of local sources was 64.1%. The contribution of outside sources mainly included the transport from Anhui, Shanxi-Shaanxi-Henan and Yangtze river delta. In the vertical direction, in the type of import, the local contribution to BC were mainly dominant under 300 m. Under the type of stable, the dominant contribution from local sources can be keep to more than 1 500 m(local source accounts for about 75% on surface and 50% at 1 500 m). In terms of diurnal variation, the change of contribution proportions of local and outside sources to BC in "Hunan-Hubei" was opposite. The proportion of local contribution remained high in the morning and night, while the contribution of external transport was low. In the afternoon, the local contribution decreased, while the contributions from outside was significantly enhanced. In the type of import, this feature of diurnal variation is more obvious.