Using GoAmazon observations over the central Amazon, we investigate double‐pulse events of afternoon precipitation for the first time. Relative humidity is the dominant factor in determining the ...onset timing and the number of pulses of precipitation. A moister free troposphere on single‐pulse days features heavy precipitation in the early afternoon, which stabilizes the atmosphere and prohibits further convection. On early–onset double‐pulse days, weaker precipitation from shallower convection in the first pulse leads to less consumption of atmospheric instability, making the environment favorable for a second pulse of stronger precipitation. A cluster tracking algorithm using the scanning radar reflectivity is developed to examine the relationship between precipitation pulses. Through explicitly tracking convective clusters that exist from the first to the second pulse, convective aggregation plays a more dominant role to the survival of clusters with larger final size, and on average around 20% of cluster survivals are due to natural growth.
Plain Language Summary
We use observations to investigate the factors that control the timing and the number of pulses in precipitation over the central Amazon. We develop a cluster tracking algorithm to understand the mechanism of the relationship between different pulses. Free troposphere relative humidity (RH) is important in determining both precipitation onset timing and the number of pulses of precipitation. Natural selection of more favorable convective clusters and the interactions among convective clusters contribute to a second precipitation pulse.
Key Points
Double pulses of afternoon precipitation are observed over the Amazon rainforest and associated with locally generated deep convective systems
On the days with double pulses, the early–morning free troposphere is drier than that on days with a single pulse, which retards the development of convection and rain intensity
The second precipitation pulse is connected to the first primarily through the natural selection of favorable convective clusters and the interaction between clusters
We report on a large-scale study of the distribution of globular clusters (GCs) throughout the Virgo cluster, based on photometry from the Next Generation Virgo Cluster Survey (NGVS), a large imaging ...survey covering Virgo's primary subclusters (Virgo A = M87 and Virgo B = M49) out to their virial radii. We present the clearest evidence to date showing the difference in concentration between red and blue GCs over the full extent of the cluster, where the red (more metal-rich) GCs are largely located around the massive early-type galaxies in Virgo, while the blue (metal-poor) GCs have a much more extended spatial distribution with significant populations still present beyond 83' (~215 kpc) along the major axes of both M49 and M87. Taken as a whole, our results show that the production of the complex structures in the unrelaxed Virgo cluster core (including the production of the diffuse intracluster light) is an ongoing and continuing process.
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•A summary of structural evolution and gas-phase reactivity of coinage metal clusters.•Advances in metal nanoclusters (NCs) with emphasis on catalysis and photochemistry.•The ...correlation between the NCs and corresponding naked metal clusters is emphasized.
Building metal materials with well-defined components and the monomer-genetic property is one of the foremost challenges in chemistry and materials science. In recent years, metal nanoclusters especially those of coinage groups (i.e., Cu, Ag, and Au) have received reasonable research interest due to the availability of atomic-level precision via joint experimental and theoretical methods, enabling to unveil the mechanisms in diverse nano-catalysts and functional materials. A variety of ligand-protected metal nanoclusters (NCs) and solid-supported metal clusters have found high catalytic activity and unique selectivity in many catalytic reactions, shedding light on the size effect and active-sites mechanism, providing rational and quantitative information of surface charge state and metal-support interactions. Some ligand-protected metal NCs have been illustrated to exhibit superatom characteristics of the metallic core. This review aims to fully unveil the chemistry of coinage metal clusters. To begin with structural evolution and reactivity, we introduce the catalysis and photochemistry of coinage metal clusters from the point of view of charge-transfer redox and frontier orbitals, and bring forth a proposal to establish superatom chemistry and to connect cluster science and new materials of “cluster genes” as named cluster-genetic materials.
Forest and land fires are national and international problems. The frequency of fires in one of Indonesia's provinces, Riau, is a significant problem. Knowing where to repair the burn is essential to ...prevent more massive fires. Fires occur because of a fire triangle, namely fuel, oxygen, and heat. The third factor can be seen through remote sensing. Using the Landsat-8 satellite, named the Enhanced Vegetation Index (EVI) variable, Normalized Burn Area (NBR), Normal Difference Humidity Index (NDMI), Normal Difference Difference Vegetation Index (NDVI), Soil Adapted Vegetation Index (SAVI), and Soil Surface Temperature (LST). DBSCAN, as a grouping algorithm that can group the data into several groups based on data density. This is used because of the density of existing fire data, according to the character of this algorithm. The selected cluster is the best cluster that uses Silhouette Coefficients, eps, and minutes value extracted from each variable, so there is no noise in the resulting cluster. The result is more than 0, and the highest is the best cluster result. There are 5 clusters formed by clustering, each of which has its members. This cluster is formed enough to represent the real conditions, cluster which has a high LST value or has an NBR value. A high LST value indicates an increase in the area's temperature; a high NBR value indicates a fire has occurred in the area. The combination of LST and NBR values indicates the area has experienced forest and land fires. This study shows that DBSCAN clustered fire and surface temperature data following data from the Central Statistics Agency of Riau Province. Proven DBSCAN can cluster satellite imagery data in Riau province into several clusters that have a high incidence of land fires.
The formation of high‐nuclearity silver(I) clusters remains elusive and their potential applications are still underdeveloped. Herein, we firstly prepared a chain‐like thiolated AgI complex ...{Ag18(StBu)10(NO3)8(CH3CN)2(H2O)2 ⋅ Ag18(StBu)10(NO3)8(CH3CN)6}n (abbreviated as Ag18) in which two similar Ag18 clusters are assembled by NO3− anions. The solution containing Ag18 reacted with hydrogen sulfide with controlled concentration, promptly producing another identifiable and bright red‐emitting high‐nuclearity silver(I) cluster, Ag62(S)13(StBu)32(NO3)4 (abbreviated as Ag62). We tracked the transformation using time‐dependent electrospray ionization mass spectrometry (ESI‐MS), UV/Vis absorption and photoluminescence spectra. Based on this cluster transformation, we further developed an ultra‐sensitive turn‐on sensor detecting H2S gas with an ultrafast response time (30 s) at a low detection limit (0.13 ppm). This work opens a new way of understanding the growth of metal clusters and developing their luminescent sensing applications.
Two similar Ag18 clusters are assembled via NO3− anions to form a chain‐like thiolated AgI complex (abbreviated as Ag18). The solution containing Ag18 reacted with H2S with controlled concentration, promptly producing another identifiable and bright red‐emitting high‐nuclearity silver(I) cluster Ag62. Based on this cluster transformation, an ultra‐sensitive turn‐on sensor was developed to the detection of H2S gas with an ultrafast response time (30 s) at a low concentration (0.13 ppm).
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