Trends in Chinese global radiation, direct horizontal radiation, diffuse radiation, clearness index, diffuse fraction and percentage of possible sunshine duration for the period 1961–2000 were evaluated based on data for daily surface solar radiation and monthly sunshine duration. Annual means for all six variables were calculated for each station and for China as a whole. Linear regression analysis was used to characterize long‐term annual trends in these variables. Over the latter half of the 20th century, there have been significant decreases in global radiation (−4.5 W/m2 per decade), direct radiation (−6.6 W/m2 per decade), clearness index (−1.1% per decade), and the percentage of possible sunshine duration (−1.28% per decade), but diffuse fraction has increased (1.73% per decade). Although there is some evidence that conditions have improved in the last decade, the consistent spatial and temporal variations of these variables support the theory that increased aerosol loadings were at least partially responsible for the observed decreases in global radiation and direct radiation, the clearness index, and the monthly percentage of possible sunshine duration over much of China.

Abstract. In order to investigate the impact of different treatments for the contact angle (α) in heterogeneous ice nucleating properties of natural dust and black carbon (BC) particles, we implement the classical-nucleation-theory-based parameterization of heterogeneous ice nucleation (Hoose et al., 2010) in the Community Atmospheric Model version 5 (CAM5) and then improve it by replacing the original singlecontact-angle model with the probability-density-functionof-α (α-PDF) model to better represent the ice nucleation behavior of natural dust found in observations. We refit the classical nucleation theory (CNT) to constrain the uncertain parameters (i.e., onset α and activation energy in the single-α model; mean contact angle and standard deviation in the α-PDF model) using recent observation data sets for Saharan natural dust and BC (soot). We investigate the impact of the time dependence of droplet freezing on mixed-phase clouds and climate in CAM5 as well as the roles of natural dust and soot in different nucleation mechanisms. Our results show that, when compared with observations, the potential ice nuclei (IN) calculated by the α-PDF model show better agreement than those calculated by the single-α model at warm temperatures (T ; T > −20 • C). More ice crystals can form at low altitudes (with warm temperatures) simulated by the α-PDF model than compared to the single-α model in CAM5. All of these can be attributed to different ice nucleation efficiencies among aerosol particles, with some particles having smaller contact angles (higher efficiencies) in the α-PDF model. In the sensitivity tests with the α-PDF model, we find that the change in mean contact angle has a larger impact on the active fraction at a given temperature than a change in standard deviation, even though the change in standard deviation can lead to a change in freezing behavior. Both the single-α and the α-PDF model indicate that the immersion freezing of natural dust plays a more important role in the heterogeneous nucleation than that of soot in mixed-phase clouds. The new parameterizations implemented in CAM5 induce more significant aerosol indirect effects than the default parameterization.

The structures of the various phases endow In 2 Se 3 unique properties as well as a broad range of potential applications. However, the controversy on the structures of In 2 Se 3 strongly hinders the exploitation of its properties and potentially gives rise to misdirection of its applications. Here, taking advantage of state-of-the-art aberration-corrected scanning transmission electron microscopy, we demonstrate the atomic-scale structures of lab-created and purchased In 2 Se 3 compounds. Six phases in three polymorphs at room temperature have been observed among all the samples, which include 2H and 3R α-In 2 Se 3 , 1T, 2H, and 3R β-In 2 Se 3 , and none-layered γ-In 2 Se 3 . Raman spectra are directly correlated to individual In 2 Se 3 phases, providing fingerprints for identifying various phases of In 2 Se 3 . In addition, obvious out-of-plane ferroelectricity of 2H α-In 2 Se 3 was also observed by piezoresponse force microscopy, enabling its potential application in ferroelectric devices.