Peak Precipitation Research Articles

Advanced growing-season precipitation peak promotes soil nitrogen mineralization in a semi-arid grassland

Soil nitrogen (N) mineralization is a key process of global N cycling and profoundly regulates plant productivity and soil nutrient pools in the terrestrial biosphere. However, its response to seasonal precipitation redistribution remains largely unexplored. As part of a nine-year (2013–2021) field experiment that simulated advanced and/or delayed growing-season precipitation peaks in a semi-arid grassland on the Mongolian Plateau, this study was conducted for two years (2020–2021) in situ to examine the effects of changing precipitation distributions in the growing seasons on soil mineralization processes. The results showed that advanced precipitation peak (AP) increased soil ammonification (Ramm), nitrification (Rnit), and net mineralization rates (Rmin) by 45.8 %, 26.0 %, and 84.4 %, respectively (all p < 0.001), whereas delayed precipitation peak (DP) enhanced Ramm by 55.7 % (p < 0.001) only, but did not change Rnit or Rmin. The elevated soil N mineralization under the AP treatment could be primarily attributed to the increased soil water availability and microbial biomass N in the early growing season, both of which play essential roles in meditating biological processes in the soil. In addition, the large consumption of soil inorganic N in the early and middle growing seasons may lead to an enhancement of ammonification in September. These observations suggest that advanced rather than delayed growing-season precipitation peak has a stronger influence on soil N dynamics in the growing seasons. Moreover, our findings highlight the positive contributions of altered N transformations to soil respiration and net ecosystem productivity under the AP treatment and imply the crucial roles of intra-annual redistribution of precipitation in regulating ecosystem nutrient and carbon cycling in semi-arid regions.

Advanced precipitation peak offsets middle growing-season drought in impacting grassland C sink.

Redistribution of precipitation across seasons is a widespread phenomenon affecting dryland ecosystems globally. However, the impacts of shifting seasonal precipitation patterns on carbon (C) cycling and sequestration in dryland ecosystems remain poorly understood. In this study, we conducted a 10-yr (2013-2022) field manipulative experiment that altered the timing of growing-season precipitation peaks in a semi-arid grassland. We found that the delayed precipitation peak suppressed plant growth and thus reduced gross ecosystem productivity, ecosystem respiration, and net ecosystem productivity due to middle growing-season water stress. Surprisingly, shifting more precipitation to the early growing season can advance plant development, increase the dominance of drought-tolerant forbs, and thus compensate for the negative impacts of middle growing-season water stress on ecosystem C cycling, leading to a neutral change in grassland C sink. Our findings indicate that greater precipitation and plant development in spring could act as a crucial mechanism, maintaining plant growth and stabilizing ecosystem C sink. This underscores the urgent need to incorporate precipitation seasonality into Earth system models, which is crucial for improving projections of terrestrial C cycling and sequestration under future climate change scenarios.

On the Importance of Precipitation‐Induced Surface Sensible Heat Flux for Diurnal Cycle of Precipitation in the Maritime Continent

AbstractThe Maritime Continent (MC) exhibits a pronounced diurnal cycle in precipitation, with many high‐resolution models overestimating the diurnal peak and predicting earlier precipitation over the islands than observed. We hypothesize that part of this model bias comes from ignoring precipitation‐induced surface sensible heat flux (QP). To test this conjecture, we performed simulations with and without QP for April 2009 and June 2006. The inclusion of QP reduced the bias in diurnal peak precipitation amplitude by 83% in April 2009 and 23% in June 2006. Similarly, the bias in precipitation peak timing decreased by 26% and 15%, respectively. This bias reduction was even more prominent during periods of heavier rainfall. This improvement in both the amplitude and phase of diurnal precipitation also led to a reduction in bias for total precipitation by ∼10%. These findings suggest that QP cannot be neglected over the MC, particularly during heavy precipitation.

Detecting the Vertical Structure of Extreme Precipitation in the Headwater Area of Yellow River Using the Dual‐Frequency Precipitation Radar Onboard the Global Precipitation Measurement Mission

ABSTRACTIn the context of global warming, the rise in extreme precipitation events in high‐altitude headwater areas has introduced greater hydrological uncertainty. However, the limited understanding of the physical mechanisms driving extreme precipitation in these areas hinders efforts to mitigate the potential rise in future precipitation risks. This study analysed the extreme precipitation events in the headwater area of the Yellow River (HAYR) from May to September each year from 2015 to 2020 using satellite‐based data from Dual‐frequency Precipitation Radar (DPR) on the Global Precipitation Measurement (GPM) Core Observatory and Integrated Multi‐satellite Retrievals for GPM (IMERG). The results show that stratiform precipitation (SP) determines the spatial extent of extreme precipitation events, while convective precipitation (CP) largely affects the rainfall intensity. Statistical analysis from different extreme precipitation events indicates that the rain rate of CP is 2 to 3 times higher than that of SP, thus zones of intense precipitation in the study area are normally dominated by CP. Vertically, the topographic lifting in complex mountainous regions exerts opposite effects on the precipitation rates of SP and CP, weakening the precipitation intensity of SP while enhancing that of CP. The peak precipitation rate in the midstream and downstream regions is observed at approximately 5 km, whereas the upstream region displays a distinctive double‐peaked distribution, with one peak at 8.5 km and another near the surface. This study provides a better understanding of the interior structure evolution process of plateau precipitation, as well as the associated microphysical properties, and highlights some insights to improve microphysical parameterization in the future model developments.

How Does Tropical Cyclone‐Induced Remote Moisture Transport Affect Precipitation Over East Asia

AbstractAnalyzing tropical cyclone‐induced remote moisture transport clusters (TRCs) and their effects on precipitation is crucial for understanding precipitation formation and enhancing forecast precision. Prior research, primarily case‐based, did not fully grasp the nature of TRCs. Utilizing an objective TRC identification method, we categorized 65 TRC tracks in East Asia into five types and examined their traits and precipitation links. The findings indicate that the moisture transport height of TRCs varies due to multiple factors, with higher transport linked to the warm conveyor belt and lower transport attributed to Taiwan’s mountain range influencing low‐level moisture. The precipitation peak altitudes of TRCs at higher latitudes are greater, and their precipitation intensity is positively correlated with terrain type, especially coastlines. This study underscores the diversity in TRC characteristics and related precipitation, suggesting that future research should consider the directionality of TRC tracks.

Two Types of Transitions to Relatively Fast Spinup in Tropical Cyclone Simulations with Weak-to-Moderate Environmental Vertical Wind Shear

Abstract Tropical cyclone intensification is simulated with a cloud-resolving model under idealized conditions of constant SST and unidirectional environmental vertical wind shear maximized in the middle troposphere. The intensification process commonly involves a sharp transition to relatively fast spinup before the surface vortex achieves hurricane-force winds in the azimuthal mean. The vast majority of transitions fall into one of two categories labeled S and A. Type S transitions initiate quasi-symmetric modes of fast spinup. They occur in tropical cyclones after a major reduction of tilt and substantial azimuthal spreading of inner-core convection. The lead-up also entails gradual contractions of the radii of maximum wind speed rm and maximum precipitation. Type A transitions begin before an asymmetric tropical cyclone becomes vertically aligned. Instead of enabling the transition, alignment is an essential part of the initially asymmetric mode of fast spinup that follows. On average, type S transitions occur well after and type A transitions occur once the cyclonically rotating tilt vector becomes perpendicular to the shear vector. Prominent temporal peaks of lower-tropospheric CAPE and low-to-midlevel relative humidity averaged over the entire inner core of the low-level vortex characteristically coincide with type S but not with type A transitions. Prominent temporal peaks of precipitation and midlevel vertical mass flux in the meso-β-scale vicinity of the convergence center characteristically coincide with type A but not with type S transitions. Despite such differences, in both cases, the transitions tend not to begin before the distance between the low-level convergence and vortex centers divided by rm reduces to unity.

Seasonal and vertical patterns of water availability and variability determine plant reproductive phenology.

Changing precipitation regimes can influence terrestrial plants and ecosystems. However, plant phenological responses to changing precipitation temporal patterns and the underlying mechanisms are largely unclear. This study was conducted to explore the effects of seasonal precipitation redistribution on plant reproductive phenology in a temperate steppe. A field experiment with control (C), advanced (AP) and delayed (DP) growing-season precipitation peaks, and the combination of AP and DP (ADP) were employed. Seven dominant plant species were selected and divided into two functional groups (early- vs. middle-flowering species, shallow- vs. deep-rooted species) to monitor reproductive phenology including budding, flowering, and fruiting date, as well as reproductive duration for four growing seasons from 2015 to 2017, and 2022. The AP, but not DP treatment advanced the phenological (i.e., budding, flowering, and fruiting) dates and lengthened the reproductive duration across the 4 growing seasons and 7 monitored species. In addition, the phenological responses showed divergent patterns among different plant functional groups, which could be attributed to shifts in soil moisture and its variability in different months and soil depths. Moreover, species with lengthened reproductive duration increased phenological overlap with other species, which could have a negative impact on their dominance under the AP treatment. Our findings reveal that changing precipitation seasonality could have considerable impacts on plant phenology by affecting soil water availability and variability. Incorporating these two factors simultaneously in the phenology models will help us understand the response of plant phenology under intensified changing precipitation scenarios. In addition, the observations of decreased dominance for the species with lengthened reproductive duration suggest that changing reproductive phenology can have a potential to affect community composition in grasslands under global change.

Impact of Atmospheric River and Local Topography on “21·7” Extremely Heavy Rainfall in Henan Province, China

An extremely heavy rainfall occurred in Henan Province, China, from July 19th to 21st in 2021, with large precipitation, long duration and wide precipitation area. Impact of water vapor transportation from atmospheric river (AR) on the rainfall was studied through reanalysis data and weather research and forecasting (WRF) model. Precipitation reached over 600 mm around Mount Song, which lasted for 48 h. The AR provided sufficient water vapor condition for the long-lasting rainfall. Regional averaged hourly precipitation was positively correlated with the amplitude of Integrated Horizontal Water Vapor Transport (IVT) and negatively correlated with IVT divergence (IVTD). Maximum precipitation regions were consistent with large IVT and IVTD regions. Peaks of IVT and IVTD were advancing of precipitation peak. Precipitation was affected by Mount Song through influencing spatial distribution and vertical structure of ARs and vertical velocity. Orographic lifting and wind converging around Mount Song caused the heavy rainfall in Zhengzhou City on July 20th. Precipitation, large IVT, IVTD and updrafts region located northwesterly of Mount Song in half mountain and without mountain tests. Comparing sensitivity tests with control simulation, air mass transporting by the AR and convective systems slowed down (or stagnated) when met the mountain, resulting in long lasting duration and large precipitation.

Impact of paleohydrological conditions on wetland organic carbon accumulation in the monsoon-arid transition zone of North China during the Holocene

Wetlands rich in carbon are important ecosystems for storing organic carbon, with their carbon storage capacity closely linked to water levels. Therefore, it is valuable to explore the relation between paleohydrological conditions and the organic carbon accumulation in carbon-rich deposits. This study examined the total organic carbon concentration and the molecular and carbon isotope compositions of n-alkanes in Ganhai, a dried up lake located in a region transitioning from a monsoon to an arid climate in north China. The results showed that the apparent carbon accumulation rates (CAR) increased as the East Asian summer monsoon intensified (averaged at 26.5 g C m−2 yr−1, 1 σ = 8.6), but decreased when precipitation levels peaked (averaged at 15.8 g C m−2 yr−1, 1 σ = 2.2). The above relation between precipitation and CAR in Ganhai is supported by the correlation analysis (r = −0.35, p = 0.003). This suggests a threshold relation between wetland carbon accumulation and precipitation in this region. The output of a Bayesian multi-source mixing model, based on the molecular and carbon isotope compositions of long-chain n-alkanes, underscores the significant role of aquatic plants in influencing carbon accumulation in Ganhai during the mid-Holocene, with submersed plants dominating during high CAR periods and floating plants being more prevalent during peak precipitation. The study emphasizes the importance of understanding the hydrological threshold for carbon sequestration and vegetation restoration in carbon-rich wetlands.

Global variable-resolution simulations of extreme precipitation over Henan, China, in 2021 with MPAS-Atmosphere v7.3

Abstract. A historic rainstorm occurred over Henan, China, in July 2021 (“7.20” extreme precipitation event), resulting in significant human casualties and socioeconomic losses. A global variable-resolution model (MPAS-Atmosphere v7.3) was employed to simulate this extreme precipitation event. A series of simulations have been done at both quasi-uniform (60 and 15 km) and variable-resolution (60–15 and 60–3 km) meshes from hydrostatic to nonhydrostatic scale with two parameterization scheme suites. For the 48 h peak precipitation duration (20–22 July), the 60–3 km variable-resolution simulation coupled with the scale-aware convection-permitting parameterization scheme suite stands out predominantly among other simulation experiments as it reproduces this extreme precipitation event most accurately. At 15 km resolution, the 60–15 km variable-resolution simulation achieves comparable forecasting skills to the 15 km quasi-uniform simulation but at a much reduced computing cost. In addition, we found that the default mesoscale suite generally outperforms the convection-permitting suite at 15 km resolution as simulations coupled with the convection-permitting suite missed the third peak of this extreme precipitation event, while the mesoscale suite did not. Furthermore, it is found that the large-scale circulation plays a critical role in the peak precipitation simulations at 15 km resolution, via influencing the simulated low-level wind. During the second peak precipitation period, simulations with the convection-permitting parameterization scheme suite at 15 km resolution generate a prominent low-level easterly wind component bias, which is largely attributed to the excessively evaporative cooling in the lower troposphere. This study further reveals that at 15 km resolution the diabatic heating from the grid-scale precipitation accounts more for the low-level wind bias than the convective-scale precipitation. Given that two different cloud microphysics schemes, namely Thompson and WSM6 schemes, are used in the convection-permitting and default mesoscale parameterization scheme suites, respectively, these microphysics schemes are found to be the primary contributor to the low-level wind simulation bias.

Precipitation of secondary Laves phases and its effect on notch sensitivity

AbstractThe precipitation of secondary Laves phases and its effect on notch sensitivity are systematically studied in Thermo-Span alloy. The results show that the precipitation peak temperature of secondary Laves phases is 925 °C. Below 925 °C, the volume fraction of secondary Laves phases increases with the rise of the temperature, and its morphology changes from granular to thin-film; above 925 °C, the volume fraction of secondary Laves phases shows an opposite trend to temperature, and its morphology changes from thin-film to granular. A detailed explanation through linear density (ρ) is provided that the influence of secondary Laves phases at the grain boundaries (GBs) on notch sensitivity depends on the coupling competition effect of their size, quantity, and morphology. Notably, the granular Laves phases are more beneficial to improving the notch sensitivity of the alloy compared with thin-film Laves phases. Granular secondary Laves phases can promote the formation of γ′ phases depletion zone to improve the ability of GBs to accommodate high strain localization, and effectively inhibit the crack initiation and propagation.

Experimental selection of rolling contact length to the average thickness (L\\have) ratio for producing fine-grain Incoloy 907 superalloy sheet by hot-rolling

The current study investigates the effects of L\\have values on the microstructure and tensile properties of the superalloy Incoloy 907. These effects are studied using hot-rolling at 84 % and 96 % thickness reductions. Microstructural examination of the received sample revealed a non-uniform coarse grain structure with precipitates of oxide phases rich in niobium and Laves. These precipitates are shredded and randomly distributed in the microstructure with elongated grains after hot-rolling under 84 % reduction. Following the solution-treatment, this sample's simultaneous static recrystallization and precipitation of secondary-phase particles has formed a banded structure of grain-size and secondary-phase particle bands. The particles of the secondary-phases are locally accumulated on the material's surface in the 96 % hot-rolled sample, creating a duplex grain and non-random microstructures with different cross-sectional conditions. The secondary-phase particle bands caused by the previous solution-treatment are retained in the pre-hot-rolled sample under 84 % reduction after aging. Furthermore, XRD analysis results show that the precipitation peak of γ'/γ phase was more visible and intense in this sample. Tensile tests conducted at room temperature and 649 °C indicate that the pre-hot-rolled sample with an 84 % reduction exhibited a 1 % improvement in cold ductility and an 8 % enhancement in hot ductility compared to the sample with a 96 % reduction.

Anti-phase variation of long eccentricity and precipitation in inland Asia during the Middle Miocene Climatic Optimum

The mechanisms and pace of orbital forcing on precipitation in inland Asia during the Cenozoic remain poorly understood. Many previous studies using magnetic proxies for precipitation have shown a consistent signal of long eccentricity (405 kyr) in hydrological records of central China that are younger than ca. 11 Ma. Most studies suggest that variations in rainfall amount were controlled by Northern Hemisphere summer insolation, and the peak of precipitation is associated with eccentricity maxima. Here, we report multiple magnetic records dating back to the Middle Miocene Climatic Optimum (MMCO, ∼14−17 m.y. ago), including a detailed record from a new section in the Qaidam Basin, which was dated using magnetostratigraphy, U-Pb geochronology, and apatite low-temperature thermochronology. Our records show the exact opposite: 405 kyr wet-dry cycles dominated, but the wetter intervals correspond to eccentricity minima and ice-volume maxima during the MMCO. Taken at face value, these results question the origin—monsoonal or westerly-derived—of the precipitation that reached central China during the middle Miocene and the mechanisms that enhanced monsoonal penetration of inland Asia. We also suggest that this anti-phase relationship could also reflect biases in magnetic proxies for precipitation during the wettest climatic phases, which can result in the dissolution of magnetic minerals and a significant underestimation of past rainfall.

Characteristics of precipitation changes during tropical cyclone processes in China from 1980 to 2019

Tropical cyclones (TCs) and their associated intense rainfall are among the most significant natural disasters. Exploring the characteristics of tropical cyclone precipitation (TCP) has always been a challenging issue in TC research. This study utilized the TC track data from the International Best Track Archive for Climate Stewardship and precipitation data from the multi-source weighted-ensemble precipitation covering the years 1980–2019, to examine shifts in precipitation rates and peak precipitation levels before and after TC landfall. The results highlight several key findings: (1) Precipitation during the TC landfall process is relatively stable beforehand but tends to decrease slightly after landfall. Generally, the maximum precipitation occurs during the landfall. (2) From 1980 to 2019, the rate of precipitation changes before landfall has significantly increased. Conversely, after the year 2000, the rate of precipitation changes after landfall has significantly decreased. (3) Over the past 40 years, while peak precipitation levels of landfalling TCs have remained relatively constant, the total precipitation has shown an increasing trend, particularly in regions like the main island of Hainan, southern Zhejiang, and Shanghai, which are characterized by high peak precipitation. The results help clarify the TC processes and provide reference points for parameter selection in regional TCP modeling.

Projected changes in heat, extreme precipitation, and their spatially compound events over China’s coastal lands and seas through a high-resolution climate models ensemble

China’s coastal lands and seas are highly susceptible to the changing environment due to their dense population and frequent economic activities. These areas experience more significant impacts from climate change-induced extreme events than elsewhere. The most noticeable effects of climate change are extreme high temperatures and extreme precipitation. We employ an ensemble of RCMs (Regional Climate Models) to investigate and project changes in temperature, precipitation, and Compound Heat-Precipitation Extreme events (CHPEs) over selected China’s coastal lands and seas for both historical (1985–2004) and future periods (2080–2099). The multi-model ensemble projects that daily temperature extremes will increase by 2.9 °C to 5.4 °C across China’s coastal lands and seas, with land areas showing a higher temperature increase than marine areas. Extreme precipitation shows a high geographical heterogeneity with a 2.8–3.9 mm d−1 reduction over the 15–25°N marine areas while a 2.2–5.4 mm d−1 increment over the 25°N-35°N land areas. We use the Clausius–Clapeyron relationship to reveal that the peak of daily extreme precipitation will increase by 2–7 mm d−1 and the temperature at which extreme precipitation peaks will increase by 2 °C to 6 °C by warming. The land area of 25–30°N has the highest peak precipitation increase of 9.87 mm d−1 and a peak temperature increase of 6 °C. As precipitation extremes intensify with daily temperature extremes increase, CHPEs are projected to occur more frequently over both land and marine areas. Compared with the historical period, the frequency of CHPEs will increase by 40.9%-161.2% over marine areas, and by 36.2%-163.6% over land areas in the future. The 15–20°N area has the highest frequency increase of CHPE events, and the 25–30°N area has the largest difference in frequency increase under two different scenarios. It indicated that the 25–30°N area will be more easily affected by climate change.

When, Where and to What Extent Do Temperature Perturbations Near Tropical Deep Convection Follow Convective Quasi Equilibrium?

AbstractConvective Quasi‐Equilibrium (CQE) is often adopted as a useful closure assumption to summarize the effects of unresolved convection on large‐scale thermodynamics, while existing efforts to observationally validate CQE largely rely on specific spatial domains or sites rather than the source of CQE constraints—deep convection. This study employs a Lagrangian framework to investigate leading temperature perturbation patterns near deep convection, of which the centers are located by use of an ensemble of satellite measurements. Temperature perturbations near deep convection with high peak precipitation are rapidly adjusted toward the CQE structure within the [−2, 1] hours centered on peak precipitation. The top 1% precipitating deep convection constrains neighboring free‐tropospheric leading perturbations up to 9°. Notable CQE validity beyond a 1° radius is observed when peak precipitation exceeds the 93rd percentile. These findings suggest that only a small fraction of deep convection with extreme precipitation shapes tropical free‐tropospheric temperature patterns dominantly.

Changes in Convective Precipitation Reflectivity over the CONUS Revealed by High-Resolution Radar Observations from 2015 to 2021

The change in extreme precipitation events in the conterminous United States (CONUS) has been of interest to the research communities in recent years for its intensification under environmental and climate change. Previous studies have not yet used sub-hourly precipitation observations to examine convective precipitation change over the CONUS. This study aims to fill the gap by examining convective precipitation, identified by radar reflectivity, in the CONUS using the state-of-the-art Multi-radar Multi-sensor data, operated at the NOAA/National Severe Storms Laboratory, with an unprecedentedly high spatial (1 km) and temporal (2 min) resolutions. These high-resolution data are expected to better capture the precipitation peak and the precipitation pattern. The results showed that in CONUS, precipitation reflectivity increased both in magnitude and the number of convective days from 2015 to 2021. For example, in 2019, 60% of areas showed an increase in the magnitude of precipitation, and the average number of convective days over CONUS has increased by 19%. Changes in precipitation also vary by season and region. This study highlights the need for continued monitoring and understanding of the evolving pattern of extreme precipitation in the CONUS, especially at sub-hourly frequency, as it exposes significant impacts on various sectors, including agriculture, infrastructure, and human health.

Analyzing vegetation health dynamics across seasons and regions through NDVI and climatic variables

This study assesses the relationships between vegetation dynamics and climatic variations in Pakistan from 2000 to 2023. Employing high-resolution Landsat data for Normalized Difference Vegetation Index (NDVI) assessments, integrated with climate variables from CHIRPS and ERA5 datasets, our approach leverages Google Earth Engine (GEE) for efficient processing. It combines statistical methodologies, including linear regression, Mann–Kendall trend tests, Sen's slope estimator, partial correlation, and cross wavelet transform analyses. The findings highlight significant spatial and temporal variations in NDVI, with an annual increase averaging 0.00197 per year (p < 0.0001). This positive trend is coupled with an increase in precipitation by 0.4801 mm/year (p = 0.0016). In contrast, our analysis recorded a slight decrease in temperature (− 0.01011 °C/year, p < 0.05) and a reduction in solar radiation (− 0.27526 W/m2/year, p < 0.05). Notably, cross-wavelet transform analysis underscored significant coherence between NDVI and climatic factors, revealing periods of synchronized fluctuations and distinct lagged relationships. This analysis particularly highlighted precipitation as a primary driver of vegetation growth, illustrating its crucial impact across various Pakistani regions. Moreover, the analysis revealed distinct seasonal patterns, indicating that vegetation health is most responsive during the monsoon season, correlating strongly with peaks in seasonal precipitation. Our investigation has revealed Pakistan's complex association between vegetation health and climatic factors, which varies across different regions. Through cross-wavelet analysis, we have identified distinct coherence and phase relationships that highlight the critical influence of climatic drivers on vegetation patterns. These insights are crucial for developing regional climate adaptation strategies and informing sustainable agricultural and environmental management practices in the face of ongoing climatic changes.

The Effect of Hot Forming–Quenching and Heat Treatment Processes on the Mechanical Properties of AA6016 Aluminum Alloy Sheets

This study explored the impact of Hot Forming–Quenching (HFQ) and heat treatment processes on the mechanical properties of AA6016 sheets. The experimental findings demonstrated that at high-temperature pre-straining (HT-PS) of 15%, the strength performance of the AA6016 sheet exhibited enhancement, with a progressive increase in both the heat treatment temperature and duration. Conversely, under HT-PS conditions of 3% and 7%, the heat treatment process exhibited a relatively modest impact on the mechanical properties of the AA6016 sheet. Differential scanning calorimetry (DSC) was employed to understand the influence of different process conditions on the precipitated phases. By comparing the precipitation peaks of the β″ phase at HT-PS of 3% and 15%, it was observed that the precipitation peak of the β″ phase decreased with an increase in HT-PS. This indicated that HT-PS promoted the precipitation of the β″ phase. In order to forecast the mechanical performance of the AA6016 sheets after applying various pre-straining and heat treatment parameters, two models were used: a backpropagation (BP) neural network and a genetic algorithm (GA)-BP neural network. These models were evaluated for their fitting and predictive capabilities. The research findings demonstrated that the GA-BP neural network model exhibited superior fitting and predictive accuracy compared to the BP neural network model.

Recent trends in agriculturally relevant climate in Central America

AbstractThis study examines the climatology and trends in climate in Guatemala, Honduras, and El Salvador over the past four decades, against the background of potential impacts on rainfed agriculture, livelihoods, and migration. The results show that there has been a significant warming of surface temperatures, an earlier start to the monsoon, a drier and longer mid‐summer drought, and a delay in the second peak of precipitation from September to October. These changes have led to an increase in vapour pressure deficit (VPD) in northern Guatemala and along the Pacific coast in winter. High VPD can stress plants and lead to reduced yields. The study also finds that the thresholds that cause a decline in coffee yield have already been reached in El Salvador, but the average VPD has also risen in Guatemala and Honduras over the past 42 years. Maize yields have also been negatively affected with an inverse relationship with daily maximum temperatures during the summer flowering season. Observed changes and trends in these climate factors are believed to have direct implications for crop yields and livelihoods, potentially driving shifts in migration patterns.