Rainfall is a major driver of food production in rainfed smallholder farming systems. This study was conducted to assess linear trends in (i) diferent daily rainfall amounts (40 mm∙day -1), and (ii) ...monthly and seasonal rainfall amounts. Drought was determined using the rainfall variability index. Daily rainfall data were derived from 18 meteorological stations in southern Africa. Daily rainfall was dominated by 40 mm day-1 category. Semi-arid location experienced increasing trends in <5 and 5-10 mm∙day-1 events. A significant linear trend in seasonal rainfall occurred at two locations with decreasing rainfall (1.24 and 3 mm∙season-1). A 3 mm∙season-1 decrease in seasonal rainfall was experienced under semi-arid conditions. There were no apparent linear trends in monthly and seasonal rainfall at 15 of the 18 locations studied. Drought frequencies varied with location and were 50% or higher during the November-March growing season. Rainfall trends were location and agro-ecology specific, but most of the locations studied did not experience significant changes between the 1900s and 2000s.
Variations in the rainfall distribution during the growing season are a major limiting factor restricting the spring maize yield on the semiarid Loess Plateau of China. Conservation tillage can ...improve yield and water use efficiency but the specific effects of conservation tillage with differing rainfall distributions during the growing season remain unclear. Therefore, a 12-year experiment was conducted and the data were divided into two categories based on rainfall distribution type. If poor rainfall occurred during the jointing-tasseling stage of the maize growing season and adequate rainfall occurred in the filling-maturity stage, the rainfall was named type-A. In contrast, if adequate rainfall occurred in the jointing-tasseling stage and poor rainfall occurred in the filling-maturity stage during the maize growing season, the rainfall distribution was categorized as type-B. This research used conventional tillage (CT) as a control to study the productivity of no-tillage (NT) and subsoiling (ST) under the selected rainfall distributions. The results showed that the type-B rainfall distribution increased dry matter accumulation, yield, soil water use efficiency (WUE) and precipitation use efficiency (PUE) by 18.9%, 32.0%, 21.7% and 45.1%, respectively, when compared with the type-A rainfall distribution. However, under type-A rainfall distribution, NT increased soil water storage by 3.7% and 4.4% and ST increased the soil water storage by 6.0% and 7.0% in the tasseling and grain filling stages, respectively, compared with CT. Moreover, NT and ST increased the dry matter accumulation, yield, WUE and PUE. The relationships among the yield, soil water storage and precipitation showed that the water storage in the sowing stage indirectly affected the maize yield through soil water storage at the tasseling stage, and the increase in precipitation from the jointing to tasseling stages had a directly positive effect on the increase in yield. Based on soil water storage with a value of 202.3 mm in the 0–200 cm soil depth during the tasseling stage, the yield increased by 47.8 kg ha−1 as the soil water storage improved by 1 mm. In conclusion, no-tillage and subsoiling improved the soil water conditions, mitigated the soil drought stress caused by variable rainfall distribution and improved the yield. Therefore, no-tillage and subsoiling practices are recommended for agricultural production in semiarid areas.
•Rainfall distribution in the growing season affects maize yield more than the rainfall quantity.•Rainfall and water storage in tasseling stage dominate maize yield.•No-tillage and subsoiling increase yield and WUE in unbalanced rainfall distribution.
Water scarcity is a major constraint limiting grain legume production particularly in the arid and semi‐arid tropics. Different climate models have predicted changes in rainfall distribution and ...frequent drought spells for the future. Although drought impedes the productivity of grain legumes at all growth stages, its occurrence during reproductive and grain development stages (terminal drought) is more critical and usually results in significant loss in grain yield. However, the extent of yield loss depends on the duration and intensity of the stress. A reduction in the rate of net photosynthesis, and poor grain set and grain development are the principal reasons for terminal drought‐induced loss in grain yield. Insight into the impact and resistance mechanism of terminal drought is required for effective crop improvement programmes aiming to improve resistance to terminal drought in grain legumes. In this article, the impact of terminal drought on leaf development and senescence, light harvesting and carbon fixation, and grain development and grain composition is discussed. The mechanisms of resistance, management options, and innovative breeding and functional genomics strategies to improve resistance to terminal drought in grain legumes are also discussed.
This study employed 15 CMIP6 GCMs and evaluated their ability to simulate rainfall over Uganda during 1981–2014. The models and the ensemble mean were assessed based on the ability to reproduce the ...annual climatology, seasonal rainfall distribution and trend. Statistical metrics used include mean bias error, normalized root mean square error, and pattern correlation coefficient. The Taylor diagram and Taylor skill score (TSS) were used in ranking the models. The models' performance varies greatly from one season to the other. The models reproduced the observed bimodal rainfall pattern of March to May (MAM) and September to November (SON) occurring over the region. Some models slightly overestimated, while some slightly underestimated, the MAM rainfall. However, there was a high rainfall overestimation during SON by most models. The models showed a positive spatial correlation with observed dataset, whereas a low correlation was shown inter‐annually. Some models could not capture the rainfall patterns around local‐scale features, for example, around the Lake Victoria basin and mountainous areas. The best performing models identified in the study include GFDL‐ESM4, CanESM5, CESM2‐WACCM, MRI‐ESM2‐0, NorESM2‐LM, UKESM1‐0‐LL, and CNRM‐CM6‐1. The models CNRM‐CM6‐1, and CNRM‐ESM2 underestimated rainfall throughout the annual cycle and mean climatology. However, these two models better reproduced the spatial trends of rainfall during both MAM and SON. Caution should be taken when employing the models in seasonal climate change studies as their performance varies from one season to another. The model spread in CMIP6 over the study area also calls for further investigation on the attributions and possible implementation of robust approaches of machine learning to minimize the biases.
Evaluation of the general climate models in CMIP6 over Uganda.
Rewilding abandoned farmlands provides a nature-based climate solution via carbon (C) offsetting; however, the C-cycle–climate feedback in such restored ecosystems is poorly understood. Therefore, we ...conducted a 2-year field experiment in Loess Plateau, China, to determine the impacts of warming (∼1.4 °C) and altered precipitation (±25 %, ±50 %, and ambient), alone or in concert on soil C pools and associated C fluxes. Experimental warming significantly enhanced soil respiration without affecting the ecosystem net C uptake and soil C storage; these variables tended to increase along the manipulated precipitation gradient. Their interactions increased ecosystem net C uptake (synergism) but decreased soil respiration and soil C accumulation (antagonism) compared with a single warming or altered precipitation. Additionally, most variables related to the C cycle tended to be more responsive to increased precipitation, but the ecosystem net C uptake responded intensely to warming and decreased precipitation. Overall, ecosystem net C uptake and soil C storage increased by 94.4 % and 8.2 %, respectively, under the warmer-wetter scenario; however, phosphorus deficiency restricted soil C accumulation under these climatic conditions. By contrast, ecosystem net C uptake and soil C storage decreased by 56.6 % and 13.6 %, respectively, when exposed to the warmer-drier climate, intensifying its tendency toward a C source. Therefore, the C sink function of semiarid abandoned farmland was unsustainable. Our findings emphasize the need for management of post-abandonment regeneration to sustain ecosystem C sequestration in the context of climate change, aiding policymakers in the development of C-neutral routes in abandoned regions.
Display omitted
•Warmer-drier climate enhances a tendency of abandoned farmland toward a C source.•Soil C accumulation is limited by phosphorus deficiency under warmer-wetter climate.•Ecosystem C-cycle variables except NEE were susceptible to increased precipitation.•Including intra-annual rainfall improves short-term ecosystem C cycling predictions.•Intervening post-abandonment ecosystem to sustain C offsetting under climate change.
Rainfall during the monsoon in northwest Australia has increased since the 1950s. Previous studies have explored possible causes of the rainfall increase; however, the trend has not been fully ...explained. Understanding the cause of this trend is important for interpreting climate projections and local water‐sensitive services. We explore the role of the Madden‐Julian Oscillation (MJO) in explaining the rainfall increase. The MJO, since 1974, has had a longer duration in phases associated with enhanced rainfall in northwest Australia (Phases 5 and 6) during the monsoon. We show that the rainfall trend in northwest Australia is identified only during MJO phases associated with enhanced rainfall, with a large change in daily rainfall distribution in these phases. The increasing occurrence of these MJO phases explains most of the rainfall increase, as opposed to an increase in daily rainfall independent of MJO phase, albeit with some sensitivity to MJO definition.
Plain Language Summary
Rainfall during the monsoon in northwest Australia has been increasing since the 1950s. In this study, we explore if a semi‐periodic pulse of rainfall and clouds near the equator, known as the Madden‐Julian Oscillation (MJO), may be related to the increased rainfall in the northwest. This pulse of clouds has been found, since 1974, to be spending longer periods of time over northwest Australia. We observed that the increase in MJO duration over northern Australia leads to increasing rainfall in northwest Australia.
Key Points
Rainfall in northwest Australia has been increasing since the 1950s, and the cause of this trend has so far remained unexplained
The Madden‐Julian Oscillation (MJO) has also been increasingly occurring in phases associated with increased rainfall over northern Australia
The increase in MJO convective phases over northern Australia explains most of the increase in rainfall since 1974 in northwest Australia
Different rainfall evolutions associated with landfalling tropical cyclones (TCs) SOULIK (1307) and MARIA (1808) are analyzed before and after they made landfalls in Fujian province based on ...reanalysis data of the ERA5 and CMORPH data. The two TCs shared similar tracks, motion speed as well as landing points, but showed different asymmetric features of rainfall intensities and locations relative to routes. The results primarily exhibited the discrepancy of the inland rainfall distributions between the two TCs and the related influence factors. The constant torrential rain over land with the maximum on the left of the storm track associated with SOULIK was attributed to favorable dynamical conditions. The northeasterly outflow of SOULIK was reinforced by the easterly wave in upper-level, which induced strong divergence along with the distinct ascending motions by suction effect. The strong ambient VWS broke the warm core structure of SOULIK, which pointed to south-southwest direction relevant to the strong northeasterly wind at 200 hPa, and further caused a more asymmetric rainfall pattern on the left of TC track. Besides, a cold intrusion was observed south of SOULIK in mid-levels, enhancing convective instability coincident with the alternating circumstance of cold and warm advections from the lower layer to the upper layer over south of SOULIK, which further intensify the precipitation on the left of TC track. Simultaneously, the meridional moisture convergence owing to the enhanced southerly wind at lower level played a key role in the maintenance of severe rainfall south of SOULIK. Comparatively, the 48-h accumulated rainfall over land associated with MARIA was much weaker than that associated with SOULIK, and the maximum is on the northern side. The strong convergence in the lower level induced by the predominant easterly winds interacting with coastal terrains, as well as the distinct divergence coincident with the upper level jet in the southern part of the South Asia High (SAH), provide favorable dynamical conditions for the maximum rainfall north of MARIA. Simultaneously, the strong westerlies over the South China Sea, together with the eastern cyclonic system over the Northwest Pacific, create favorable moisture conditions for the rainfall on the northern side of MARIA. Results presented in this study provides an improved predictive understanding of physical mechanism dictating storm rainfall evolution from landfalling TCs, especially those with similar tracks
•The landfalling TCs SOULIK (2013) and MARIA (2018) made landfall over China with similar tracks and landing points but caused distinct rainfall evolution, thus it is necessary to investigate the primary factors modulating precipitation distributions to provide a comprehensive understanding for the TC rainfall forecasting, especially when the prediction was carried out using empirical speculation and subjective experience on the part of the forecaster.•According to the comparative analysis, both of the water vapor flux and the VWS are significant factors responsible for the distinct rainfall distribution.•Results presented in this study provide an improved predictive understanding of physical mechanism dictating storm rainfall evolution from landfalling TCs, especially those with similar tracks.
Main conclusion
Environmental-friendly techniques based on plant stress memory, cross-stress tolerance, and seed priming help sustainable agriculture by mitigating negative effects of dehydration ...stress.
The frequently uneven rainfall distribution caused by global warming will lead to more irregular and multiple abiotic stresses, such as heat stress, dehydration stress, cold stress or the combination of these stresses. Dehydration stress is one of the major environmental factors affecting the survival rate and productivity of plants. Hence, there is an urgent need to develop improved resilient varieties. Presently, technologies based on plant stress memory, cross-stress tolerance and priming of seeds represent fruitful and promising areas of future research and applied agricultural science. In this review, we will provide an overview of plant drought stress memory from physiological, biochemical, molecular and epigenetic perspectives. Drought priming-induced cross-stress tolerance to cold and heat stress will be discussed and the application of seed priming will be illustrated for different species.
The temporal variation and trends of annual rainfall distribution in Benin were examined using data from 1940 to 2015 at six meteorological stations and three raingauges stationed throughout the ...country. The nonparametric modified Mann-Kendal (MK) and Levene tests were applied to detect trends and heteroscedasticity, respectively. For six of the time series, no significant trends were detected. A Bayesian multiple change points detection approach was applied to the rainfall time series, and most (six of nine) exhibited abrupt change points, corresponding to the alternation between wet (before 1968 and after 1990) and dry (1969-1990) periods. No significant trends or breakpoints and changes in the variance were observed for the spatial average rainfall time series. Seven modified MK trend tests were applied; the trends are affected by the selected MK method and rainfall statistics. Oceanic and/or atmospheric influences on the rainfall in Benin were examined by investigating the correlation between the precipitation time series and several indices. Negative seasonal correlations were determined for the North Atlantic Oscillation, Pacific Decadal Oscillation and Niño3, while positive seasonal correlations were observed for the Southern Oscillation, Antarctic Oscillation and Dipole Mode Index.
Understanding the occurrence of natural disasters in regions where the occurrence is high is very important, and it is known that the occurrence of disasters associated with intense rains is a source ...of research in different locations around the globe, being important not only for increasing accuracy of weather forecasting models, but important information for civil defense, where lives can be saved. The increase in the occurrence of natural disasters related to extreme rainfalls has become a problem of large urban centers, such as the city of Rio de Janeiro (CRJ). Thus, the identification of homogeneous regions for rainfall distribution (HRRD) becomes essential to identify regions at risks of floods and mass movements. The aim of this research was to identify HRRD in CRJ associated with the risk of natural disasters. The identification of homogeneous regions was carried out with the use of monthly rainfall data from 14 pluviometric stations spatially distributed in the study area between 1997 and 2018. Data derived from the MOD13A3 product were also used to identify the monthly temporal behavior of the vegetation areas in the CRJ during the period 2001 to 2020. Rainfall data were submitted to descriptive statistical analysis, and subsequently to Cluster Analysis. Cluster analysis identified 4 homogeneous groups regarding annual rainfall distribution. The nonparametric test analysis identified vegetation growth during the dry season and decay during the rainy season. These vegetation results found by the nonparametric Mann–Kendall test evidence the reduction in rainfall in the CRJ. The result showed relevance regarding physiographic aspects that characterize the rainfall dynamics in CRJ, highlighting areas favorable to the occurrence of natural disasters.
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