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Nepal is highly vulnerable to severe soil erosion driven by monsoonal rainfall and rugged terrains. Limitations in ground observation networks have hindered comprehensive, high-resolution national assessment of precipitation and rainfall-runoff erosivity (R-factor) across Nepal. This study systematically evaluated eight global gridded precipitation datasets (GPDs) against data from 152 weather stations, identifying the optimal precipitation dataset (TPHiPr) representing Nepal’s complex topography. Based on this high-quality dataset, we provided the first independent, long-term (1979–2020), high-resolution national-scale assessment of precipitation and the R-factor for Nepal. Our analysis reveals that 1996 marked a turning point in nationwide precipitation trends: annual precipitation shifted from a decreasing to an increasing one in the humid eastern and central regions, while the drier western region transitioned from an increasing to a decreasing trend, particularly during the dry season. A clear spatial divergence was observed between total precipitation and the R-factor, highlighting the dominant role of precipitation frequency and intensity. Extreme precipitation events intensified significantly (e.g., days with ≥25 mm rainfall increased by 0.2 days yr−1, and the 95th percentile precipitation threshold increased by 0.4 mm yr−1, p < 0.01), driving a nationwide increase in the R-factor (6.3 MJ mm ha−1 h−1 yr−2, p < 0.01), with high-altitude areas experiencing the most pronounced effects. We conclude that soil erosion risk has intensified nationwide due to increasing precipitation extremes. Watershed management must develop elevation-specific adaptation strategies that integrate climate science with practical solutions to address the dual challenges of intensified monsoon-driven erosion and growing dry-season water scarcity. 

The photodissociation dynamics of jet-cooled HCO radical was investigated in the region of 490 nm to 715 nm using the H-atom high-n Rydberg time-of-flight (HRTOF) technique. The CO product rovibrational state populations are well resolved in the H + CO product translational energy distributions, and an accurate H–C bond dissociation energy D0(H–CO) = 5086 ± 5 cm−1 is obtained. 

The ultraviolet (UV) photodissociation dynamics of the 1-methylallyl (1-MA) radical were studied using the high-n Rydberg atom time-of-flight (HRTOF) technique in the wavelength region of 226–244 nm. The 1-MA radicals were produced by 193 nm photodissociation of the 3-chloro-1-butene and 1-chloro-2-butene precursor. The 1 + 1 REMPI spectrum of 1-MA agrees with the previous UV absorption spectrum in this wavelength region. Quantum chemistry calculations show that the UV absorption is mainly attributed to the 3pz Rydberg state (perpendicular to the allyl plane). The H atom photofragment yield (PFY) spectrum of 1-MA from 3-chloro-1-butene displays a broad peak around 230 nm, while that from 1-chloro-2-butene peaks at ∼236 nm. The translational energy distributions of the H atom loss product channel, P (ET)’s, show a bimodal distribution indicating two dissociation pathways in 1-MA. The major pathway is isotropic in product angular distribution with β ∼ 0 and has a low fraction of average translational energy in the total excess energy, ⟨fT⟩, in the range of 0.13–0.17; this pathway corresponds to unimolecular dissociation of 1-MA after internal conversion to form 1,3-butadiene + H. The minor pathway is anisotropic with β ∼ −0.23 and has a large ⟨fT⟩ of ∼0.62–0.72. This fast pathway suggests a direct dissociation of the methyl H atom on a repulsive excited state surface or the repulsive part of the ground state surface to form 1,3-butadiene + H. The fast/slow pathway branching ratio is in the range of 0.03–0.08. 

Complex changes in land use, land cover, climate, and demographics are combining to stress water security for millions of people in the region. 

Abstract There are twenty experimental forest and range sites (EFRs) across the southeastern United States that are currently maintained by the USDA Forest Service (Forest Service) to conduct forest ecosystem research for addressing ecosystem management challenges. The overall objective of this study was to use multiple gridded datasets to assess the extent to which the twenty EFRs represent the climate, ecosystem structure, and ecosystem functions of southeastern forests. The EFRs represent the large variability of climate conditions across the region relatively well, but we identified small representation gaps. The representativeness of ecosystem structure by these EFRs can be improved by establishing EFRs in forests with relatively low tree cover, leaf area index, or tree canopy height. The current EFRs also represent the forest ecosystem functions of the region relatively well, although areas with intermediate and low aboveground biomass and water yield are not well represented. The trends in climate, ecosystem structure, and ecosystem functions were generally consistent between the region and the EFRs. Our study indicates that the current EFRs represent the region relatively well, but establishing additional EFRs in specific areas within the region could help more completely assess how southeastern forests respond to climate change, disturbance, and management practices. Study Implications: This study across the experimental forests and ranges (EFRs) and the southeastern forest region fills the knowledge gap regarding climate, ecosystem structure, and ecosystem functions of EFRs in the context of the broader southeastern forest region. Understanding ecosystem functions and structures across the EFR network can help the Southern Research Station to address new research questions. Our study indicates that the current EFRs represent the climate, ecosystem structure, and ecosystem functions of southeastern forests well. However, establishing additional EFRs in certain regions could help more completely assess how southeastern forests respond to climate change, disturbance, and management practices. 

Ultraviolet photodissociation dynamics of 2-methylallyl radical from the 3p Rydberg state were investigated in the wavelength region of 226–244 nm using the high-n Rydberg atom time-of-flight (HRTOF) technique. The 2-methylallyl radicals were generated by 193 nm photolysis of 3-chloro-2-methyl-1-propene precursors. The photofragment yield spectrum of H-atom products increases in intensity with decreasing wavelengths in 226–244 nm. The TOF spectra of H-atom products show a bimodal structure. The predominant product channel (with ∼98% branching ratio) has a kinetic energy release peaking at ∼7 kcal/mol, with an average ratio of ET in the total available energy, (fT), of ∼0.18 in 226–244 nm and an isotropic product angular distribution. At the low ET, isotropic component is from statistical unimolecular decomposition of highly vibrationally excited hot 2-methylallyl to the methylenecyclopropane+H products, following internal conversion from the excited electronic state. The minor product channel (with ∼2% branching ratio) has a large kinetic energy peaking at ∼50 kcal/mol, with (fT)≈0.63 and an anisotropic angular distribution (β≈−0.2). At the high ET, anisotropic component is non-statistical and is postulated to be from direct loss of H atom via the 3p Rydberg state or repulsive part of the ground state to the 1,3-butadiene+H products.