Abstract. Brown carbon (BrC), a certain group of organic carbon (OC) with strong absorption from the visible (VIS) to ultraviolet (UV) wavelengths, makes a considerable contribution to light absorption on both global and regional scales. A high concentration and proportion of OC has been reported in China, but studies of BrC absorption based on long-term observations are rather limited in this region. In this study, we reported 3-year results of light absorption of BrC based on continuous measurement at the Station for Observing Regional Processes of the Earth System (SORPES) in the Yangtze River Delta, China, combined with Mie theory calculation. Light absorption of BrC was obtained using an improved absorption Ångström exponent (AAE) segregation method. The AAE of non-absorbing coated black carbon (BC) at each time step is calculated based on Mie theory simulation, together with single particle soot photometer (SP2) and aethalometer observations. By using this improved method, the variation of the AAE over time is taken into consideration, making it applicable for long-term analysis. The annual average light absorption coefficient of BrC (b abs_BrC ) at 370 nm was 6.3 Mm −1 at the SORPES station. The contribution of BrC to total aerosol absorption (P BrC ) at 370 nm ranged from 10.4 to 23.9 % (10th and 90th percentiles, respectively), and reached up to ∼ 33 % in the openbiomass-burning-dominant season and winter. Both b abs_BrC and P BrC exhibited clear seasonal cycles with two peaks in later spring/early summer (May-June, b abs_BrC ∼ 6 Mm −1 , P BrC ∼ 17 %) and winter (December, b abs_BrC ∼ 15 Mm −1 , P BrC ∼ 22 %), respectively. Lagrangian modeling and the chemical signature observed at the site suggested that open biomass burning and residential coal/biofuel burning were the dominant sources influencing BrC in the two seasons, respectively.

No abstract

The water circulation among atmosphere, land, surface, and ground water, that is, hydrological cycle, is crucial for life on Earth (Gleick, 1989;Levin & Cotton, 2009). Precipitation is one of the most important links in the hydrologic cycle, which determines the global water balance and the total amount of water resources in a region (Betts, 2007;Loaiciga et al., 1996;Morrissey & Graham, 1996). Given the manifested role of rainfall in the hydrologic cycle, the spatiotemporal redistribution of surface precipitation caused by the small changes in precipitating-related processes in clouds may largely affect climate and human society (

Black carbon (BC) plays an important role in the climate system because of its strong warming effect, yet the magnitude of this effect is highly uncertain owing to the complex mixing state of aerosols. Here we build a unified theoretical framework to describe BC’s mixing states, linking dynamic processes to BC coating thickness distribution, and show its self-similarity for sites in diverse environments. The size distribution of BC-containing particles is found to follow a universal law and is independent of BC core size. A new mixing state module is established based on this finding and successfully applied in global and regional models, which increases the accuracy of aerosol climate effect estimations. Our theoretical framework links observations with model simulations in both mixing state description and light absorption quantification.