Dry Events Research Articles

Vegetation response to Holocene hydroclimatic variability in the aseasonal forests of the north-western Amazon

Projected warming and intensification of the hydrological cycle across the Amazon threatens the functioning of some of the most biodiverse ecosystems on the planet. Interfluvial wetlands, or wetlands fed directly by precipitation or small streams, may be some of the most vulnerable to future hydroclimatic changes. In this study, we investigated a 7300-year-old sedimentary archive from an upland palm swamp in the Yasuní National Park (Ecuador) to reconstruct past vegetation dynamics, palaeo-hydroclimatic conditions and human history using pollen, charcoal and geochemical analysis. Pollen data revealed: i) a forest composition influenced by dry conditions 6000 years ago, ii) the development of a palm swamp 4500 years ago, and iii) the establishment of the modern closed-canopy Mauritia flexuosa dominated swamp (moretal) 400 years ago. X-ray fluorescence data indicated that changes in vegetation composition were related to fluctuations in relative moisture levels, which occurred coeval to identified regional climatic events, particularly the Mid Holocene Dry Event (MHDE). Analysis of charcoal revealed continuous presence of fire, albeit at very low levels, since 5000 cal yr BP, with increased values during the last millennium. Our results suggest a footprint of hydroclimatic transitions in the mid-to-late Holocene in the aseasonal forests of the northwest Amazon, highlighting the need to better understand the long-term ecology of these systems to better protect them in light of future climatic change.

Escalating hot-dry extremes in Southwest China Karst

Study regionSouthwestern China of Hubei, Hunan, Guangxi, Guangdong, Yunnan, Guizhou, Sichuan, and Chongqing. Study focusCompound hot-dry extreme events (CHDEs) are escalating disproportionately worldwide, posing significant challenges across various sectors. Yet, their driving mechanisms and characteristics at a regional scale remain largely uncertain. This study used a copula-based approach to construct the daily Standardized Compound Hot-Dry Index (SCHDI) to discern the intensifying trends of hot-dry extremes from 1963 to 2022, especially under different karst landscapes in Southwestern China. New hydrological insights for the regionSCHDI variations show an escalation of hot-dry conditions across most areas, with a notable increase in extreme hot, dry, and hot-dry events. There was a consistent increase in the frequency, duration, severity, and intensity of CHDEs, with larger magnitudes observed in non-karst areas. However, karst regions exhibited a higher escalation rate in intensity, especially over the most recent three decades. Land areas affected by less severe CHDEs (e.g., abnormal: −0.31%/year) show decreasing trends over 1993–2022, while the most extreme category (e.g., extreme: 0.34%/year) has increased. The areas affected by CHDEs showed a greater increase in trend slope compared to hot or dry events alone. Additionally, these trends are further influenced by large-scale circulation patterns. Our study highlights the role of karst landscapes in escalating hot-dry extremes in Southwestern China Karst.

Improved tomato development by biochar soil amendment and foliar application of potassium under different available soil water contents

The use of carbonaceous materials such as biochar has been considered an innovative solution in agriculture, especially to mitigate dry events caused by climate change. Biochar can improve water holding capacity, physical and chemical properties of soil, and increase the productivity of agricultural systems. However, underlying physiological mechanisms remain poorly understood. Mineral supplementation with potassium nitrate (KNO3) via foliar application is another promising strategy in agricultural management under irrigation deficit. Thus, we investigated the combined effects of biochar and foliar application of KNO3 on growth, yield, and physiology of tomato plants under different irrigation regimes. Results did not indicate a synergistic effect of biochar and foliar application of KNO3. Biochar application alleviated tomato plant stress under deficit irrigation, with plants showing better functioning of photosynthetic apparatus, higher yield, and better fruit quality, as well as increased water use efficiency. Coffee husk biochar (K-rich feedstock) fully met the tomato plant’s demand for K and partially met the demand for some other elements (P, Mg, Fe, Zn, Mn, and Cu). Although positive effects of KNO3 application was verified for some physiological and fruit quality components, overall, foliar application of KNO3 did not improve tomato yield. It is concluded that biochar soil amendment can be a promising practice to increase yield and quality of tomato fruits under deficit irrigation. Therefore, biochar-based fertilizer can be an alternative K source that also provides stable carbon to soil and helps to mitigate stress caused by prolonged drought.

Future changes in spatially compounding hot, wet or dry events and their implications for the world’s breadbasket regions

Recent years were characterized by an increase in spatially co-occurring hot, wet or dry extreme events around the globe. In this study we analyze data from multi-model climate projections to analyze the occurrence of spatially compounding events and area affected in future climates under scenarios at +1.5 ∘C, +2.0 ∘C, +3.0 ∘C and higher levels of global warming using Earth System Model simulations from the 6th Phase of the Coupled Model Intercomparison Project. Since spatially compounding extreme events can strongly amplify societal impacts as economic supply chains are increasingly interdependent, we want to highlight that the world’s breadbasket regions are projected to be particularly affected by an increase in spatially co-occurring hot, wet or dry extreme events, posing risks to the global food security. We show that the spatial extent of top-producing agricultural regions being potentially threatened by climate extremes will increase drastically if global mean temperatures shift from +1.5 ∘C to +2.0 ∘C. Further we identify a large increase in the projected global land area concurrently affected by hot, wet or dry extremes with increased global warming posing risk to other industries and sectors in addition to the agricultural sector.

Differences in desiccation tolerance of two Australian freshwater mussel species with different life history characteristics is temperature dependent

Mass die-offs, reduced species richness and local extinctions of freshwater mussels have resulted from river drying events, which often co-occur with high ambient temperatures. These events are predicted to increase in frequency and severity under the influence of climate change. We aimed to identify the desiccation tolerance of two freshwater mussel species (the river mussel Alathyria jacksoni and the floodplain mussel Velesunio ambiguus) across a range of temperatures by simulating river drying events in laboratory conditions. Freshwater mussels were buried in sediment heated to 29, 32, 35, 38 and 41°C. Lethal times and lethal temperatures at which 50% mortality occurred were used to infer species-specific tolerances. The lethal time for 50% of mussels to reach mortality at 29°C was shorter for A. jacksoni (14 days) than V. ambiguus (58 days) but did not differ markedly at higher temperatures. Lethal temperatures were also similar between species over short durations (e.g. 39–40°C at 1 day). Our results suggest that the difference in desiccation tolerance between species diminishes toward their upper thermal limit. Management interventions aimed at reducing sediment temperatures, such as providing shade via riparian vegetation and wetting from environmental flows, could help alleviate the impact of drying events and climate change on both freshwater mussel species.

Differential responses of vegetation phenology to climatic elements during extreme events on the Chinese loess plateau

Extreme, dry events have major impacts on vegetation phenology worldwide. However, the differential responses of vegetation phenology to climatic elements during these extreme events remain unclear. We investigated the response of vegetation phenology to climatic factors during extreme events in arid and semi-arid regions of the Chinese Loess Plateau, using the climate water deficit method, to identify extremely dry and wet events. The results revealed that extremely wet events extended the vegetation growth periods in addition to global warming, whereas extremely dry events did not completely counteract this effect. During different extreme events, phenological changes in vegetation on the Loess Plateau were primarily influenced by the interactive effects of climatic factors. During extremely dry events, a 100 mm increase in precipitation advanced the start of the season by 3.0, 9.2, and 16.7 days in forest, shrubland, and grassland, respectively. During extremely wet events, a 1 °C rise in temperature delayed the end of the season by 1.6, 0.6, and 3.8 days in forest, shrubland, and grassland, respectively. These findings provide crucial guidance for improving predictions of plant phenology changes under extreme climatic events and unraveling biosphere–atmosphere feedback cycles.

Assessment of meteorological, hydrological and groundwater drought in the Konya closed basin, Türkiye

Water scarcity, and drought in particular, is a major challenge worldwide, causing direct and indirect negative effects on ecological systems and water resources, as well as social and economic aspects of life. Climate change and increasing human pressure are contributing to increasing the likelihood of droughts, impacting regions which were not used to be dry. To address this challenge properly, studies should be performed at a multi-scale level, addressing hydrological and hydrogeological drought. Focusing on the Konya Closed Basin in Türkiye, data derived from nineteen stations were used to analyze drought conditions, looking at multiple meteorological—Standardized Precipitation Index (SPI), Z Score Index (ZSI), China Z Index (CZI), Modified China Z Index (MCZI)—hydrological—Streamflow Drought Index (SDI), Surface Water Supply Index (SWSI)—and hydrogeological—Standardized Groundwater Level Index (SGI)—assessment indices for different time scales (1, 3, 6,12, 24, 36 and 48 months). The results show that extreme drought (ED) conditions computed by SPI at 1 month (1.9–2.5%) were higher than that of all indices for all stations. Moderate drought occurred at least according to the ZSI-1. It was determined that the percentage of SPI and CZI had greater Extremely, Severely and Moderately Dry events (10.7–13.4% for CZI; 10.7–14.2% for SPI) than those of ZSI and MCZI. On the other part, MCZI has shown fewer total drought events (6.2–10%). Since 2008, extremely dry conditions in the Konya Closed Basin are generally caused by groundwater drought, which is higher than meteorological and hydrological droughts. The results reported in this work might help in better planning drought-resilient strategies in the basin, which will be paramount in light of climate change.

How extreme hydrological events correspond to climate extremes in the context of global warming: A case study in the Luanhe River Basin of North China

AbstractThe consensus on climate warming is well‐established, and extreme values inherently encapsulate more information than averages. Against the backdrop of frequent extreme climate events, studying extreme values holds profound significance. This study aims to reveal the characteristics of extreme climate events and their role in triggering extreme hydrological events in the typical North China basin, that is, the Luanhe River Basin. Trends of 25 extreme climate indices during 1960–2018 are analysed using the Sen's slope and MK significance test to study the changing characteristics of extreme climate. Characteristics of extreme flood and dry events are examined, encompassing trend analyses at different time scales (seasonal, interannual, decadal) and concentration analysis. Finally, and most significantly, correlation analysis is conducted on extreme climate indices and features of extreme hydrological events, followed by principal component analysis of extreme climate indices, to precisely quantify the impact of extreme climate on the occurrence of extreme hydrological events. The results indicate a warming trend in extreme temperature indices, with a more significant rise in minimum temperatures compared to maximum temperatures. There is a significant decrease in precipitation, but precipitation at higher magnitudes is less affected by the overall reduction in total precipitation. Extreme dry events have markedly increased, particularly concentrated in winter with delayed occurrences, primarily induced by extreme temperature events, that is, warming effects. Conversely, extreme flood events have significantly decreased, mainly concentrated in summer and early autumn, predominantly caused by extreme precipitation and extreme high‐temperature events. The climate and hydrological conditions in the study area have become more extreme and complex. Severe river droughts may occur more frequently in winter, while extreme flooding may happen in summer. Therefore, it is necessary to pay more attention to these developments.

Spatial and temporal distribution of palaeoclimatic records in the Maya Area

Palaeoclimatic research has been performed in the Maya Area (MA), using mainly lake sediment cores and speleothems. Most of the studies have been performed in the lowlands, leaving the highlands unexplored. Lake sediments records contain a diversity of proxies (e.g. Mineralogy, isotopes, pollen, charcoal, diatoms, chemicals, magnetic susceptibility, among others) and temporal resolution, making them frequently not easy to compare and leaving numerous gaps of information. Practically all stalagmites are focused on using δ18O as a proxy of effective rainfall during the Maya periods, having only some explored the role of palaeostorms and hurricanes as well as the paleoclimatology of the pre-Maya and modern periods. In this review paper, the location and temporal frame of palaeoenvironmental records of the MA and their proxies are presented, showing the zones and periods that possess environmental information and assessing their resolution. The comparison shows that more high-resolution records with a multi-proxy approach covering most of the Holocene are needed to understand the climate change in different zones of the MA. Finally, the geographic distribution of the diverse recorded hydroclimate responses based on the records is presented for three critical moments in the Maya History that have been associated with dry periods in the Great Maya Droughts hypothesis. This geographic perspective shows that dry events were not presented in all the MA during these moments although they were vastly recorded in both high- and lowlands. The geographic perspective also shows a negligible drought effect in the central lowlands for the Maya Hiatus period, where this cultural phenomenon was identified first. But signals of droughts are presented in other zones of the MA for this period. The distribution of the drought signal also shows that sites that thrived during the Maya Collapse period were in the regions that suffered the strongest droughts, whilst many sites that were abandoned were in regions rich in hydric resources. Explanations are reviewed for these contradictions. Finally, the works towards the development of mathematical models of the environmental variables are briefly reviewed, pointing out the lack of a proper computational model that has been fed by the palaeoclimatic data developed by the records in the MA.

Comparison and evaluation of the performance of reanalysis datasets for compound extreme temperature and precipitation events in the Qilian Mountains

Due to potential powerful destruction, the compound extreme temperature and precipitation events have continuously captured the interest of scientists. However, the lack of in-situ datasets limits the knowledge of compound extreme events in the alpine mountains. We selected the Qilian Mountains and analyzed the change trends of four types of compound extreme weather events, and further evaluated the performances of five reanalysis datasets for compound extreme weather events based on the observed daily datasets from 33 meteorological stations from 1980 to 2020. The results showed that (1) The frequency of four compound extreme weather events from highest to lowest is cold-dry events, high temperature-dry events, cold-heavy precipitation events, and high temperature-heavy precipitation events. High temperature-heavy precipitation events and high temperature-dry events showed increasing trends, while cold-dry events and cold-heavy precipitation events showed decreasing trends. (2) All five reanalysis datasets underestimated temperature and overestimated precipitation. In terms of extreme temperature and extreme precipitation events, ERA5-Land performed best, followed by ERA5, Har v2 and Merra2, and JRA55 performed worst. (3) For the four types of compound weather events, the reanalysis datasets performed better for high-temperature or dry events than cold or heavy precipitation events in the Qilian Mountains. The reanalysis datasets performed best for compound high temperature-dry events and worst for compound extreme temperature-heavy precipitation events. According to the results, we recommend ERA5-Land and ERA5 for the research on the compound extreme events. The research results provide theoretical support for the study of compound extreme temperature-precipitation events in alpine regions with sparse in-situ datasets.

Impacts of Compound Hot–Dry Events on Vegetation Productivity over Northern East Asia

Climate extremes, such as heatwaves and droughts, significantly impact terrestrial ecosystems. This study investigates the influence of compound hot–dry (CHD) events on vegetation productivity in northern East Asia. Four of the most widespread CHD events occurring during the summer from 2003 to 2019 were selected as the focus of this research. We first verified the performance of the Community Land Model version 5 (CLM5) in the region and then conducted factor-controlled experiments using CLM5 to assess the effects of different climate factors on gross primary productivity (GPP) changes during CHD events. Our results show that vegetation productivity exhibits greater sensitivity to CHD events within the transitional climatic zone (TCZ) than in other affected areas. In grassland areas within the TCZ, precipitation deficit is the primary factor leading to the decrease in GPP (explaining 56%–90% of GPP anomalies), while high temperatures serve as a secondary detrimental factor (explaining 13%–32% of GPP anomalies). In high-latitude forests outside the TCZ, high temperature has a more significant impact on suppressing GPP, while the decrease in soil moisture has a synchronously negligible impact on GPP. There are differences in the effects of high solar radiation on grasslands and woodlands during CHD events. It was observed that high radiation benefits trees by increasing the maximum carboxylation rate (Vcmax) and maximum electron transport rate (Jmax), as well as enhancing photosynthesis, but has a negligible impact on grasses. Furthermore, this study highlights the potential for compound events to impact vegetation productivity more than expected from individual events due to confounding nonlinear effects between meteorological factors. More than 10% of the negative anomalies in GPP during two CHD events in 2017 and 2010 were attributed to these nonlinear effects. These research findings are significant for understanding ecosystem responses to climate extremes and their influence on carbon cycling in terrestrial ecosystems. They can also contribute to more precisely evaluating and predicting carbon dynamics in these regions.

Wet events increase tree growth recovery after different drought intensities

Understanding the dynamics of tree recovery after drought is critical for predicting the state of tree growth in the context of future climate change. While there has been a great deal of researches showing that drought events can cause numerous significant negative effects on tree growth, the positive effects of post-drought wetting events on tree growth remain unclear. Therefore, we analyzed the effect of wet and dry events on the radial growth of trees in Central Asia using data on the width of tree rings. The results showed that 1) Drought is the main limiting factor for radial growth of trees in Central Asia, and that as the intensity and sensitivity of drought increases, tree resistance decreases and recovery rises, and more frequent droughts reduce tree resistance. 2) Tree radial growth varied significantly with wet and dry conditions, with wet events before and after drought events significantly enhancing tree radial growth. 3) When drought is followed by a wetting event, the relationship between tree resistance and recovery is closer to the “line of full resilience”, with a significant increase in recovery, and compensatory growth is more likely to occur. Thus, wetting events have a significant positive effect on tree radial growth and are a key factor in rapid tree growth recovery after drought.

Flow intermittence prediction using a hybrid hydrological modelling approach: influence of observed intermittence data on the training of a random forest model

Abstract. Rivers are rich in biodiversity and act as ecological corridors for plant and animal species. With climate change and increasing anthropogenic water demand, more frequent and prolonged periods of drying in river systems are expected, endangering biodiversity and river ecosystems. However, understanding and predicting the hydrological mechanisms that control periodic drying and rewetting in rivers is challenging due to a lack of studies and hydrological observations, particularly in non-perennial rivers. Within the framework of the Horizon 2020 DRYvER (Drying River Networks and Climate Change) project, a hydrological modelling study of flow intermittence in rivers is being carried out in three European catchments (Spain, Finland, France) characterised by different climate, geology, and anthropogenic use. The objective of this study is to represent the spatio-temporal dynamics of flow intermittence at the reach level in mesoscale river networks (between 120 and 350 km2). The daily and spatially distributed flow condition (flowing or dry) is predicted using the J2000 distributed hydrological model coupled with a random forest classification model. Observed flow condition data from different sources (water level measurements, photo traps, citizen science applications) are used to build the predictive model. This study aims to evaluate the impact of the observed flow condition dataset (sample size, spatial and temporal representativity) on the performance of the predictive model. Results show that the hybrid modelling approach developed in this study allows the spatio-temporal patterns of drying to be accurately predicted in the three catchments, with a sensitivity criterion above 0.9 for the prediction of dry events in the Finnish and French case studies and 0.65 in the Spanish case study. This study shows the value of combining different data sources of observed flow condition to reduce the uncertainty in predicting flow intermittence.

Millennial-scale variability of vegetation and fire activity in a northern Cerrado driven by an east-west rainfall gradient during the Holocene

This paleoecological study investigates vegetation variability and fire regimes in Northeastern Brazil (NEB)’s Cerrado. We present high-resolution pollen and charcoal records from a palm swamp located in a Cerrado in Chapada das Mesas National Park, in the southwest of Maranhão State. The Vereda do Dodó sedimentary core is 187 cm deep and covers the past 6000 years. Our results show first the presence of an open cerrado between 6000 and 5200 cal yr BP with no fire activity and a gradual expansion of the palm Mauritia and woody cerrado after 5000 cal yr BP. This is synchronous with other studies of northeastern and central Brazil. At c. 4300 cal yr BP, sterile samples suggest a strong dry event, also recorded in other eastern NEB records. Frequent burnings lasted until 2600 cal yr BP, when fires stopped and Mauritia, arboreal cerrado, and gallery forest taxa expanded under increased moisture rates. The increase of southern hemisphere summer insolation and the warmer tropical Atlantic Ocean enhanced the monsoon system over eastern Amazonia and western NEB in agreement with speleothem records. Our study reveals that northern Cerrado biodiversity was very sensitive to SASM dynamics, a different pattern from eastern NEB vegetation and climate.

Evaluation of Drought Using Meteorological Drought Indices, a Case Study: Alanya (Türkiye)

Drought is one of the most important challenges that many countries, especially countries in the Middle East region, are struggling with. Based on this, the study and monitoring of hydrological and drought factors is an important issue that can have a significant impact on management decisions in the field of water resources, especially in crisis management. Therefore, investigating the drought parameters is very important to understand the drought situation of a region. In this study, Alanya region, which is located on the southern coast of Turkey, was selected as a case study for drought analysis. Four drought indices for the selected region including: China Z-Index (CZI), Standardized Precipitation Index (SPI), Modified China Z-Index (MCZI) and Z-Score Index (ZSI) have been investigated. All these indicators have been investigated and evaluated using time scales of 1, 6, 12 and 24 months, the coefficient of determination (R2) has been calculated for each drought index with a different time scale and their results have been compared. The findings of the research showed that SPI and CZI drought indices performed better than other selected drought indices in identifying and effectively tracking drought severity. In addition to the study of dry events, wet events were also investigated, which indicates the presence of consecutive floods in the last years of the studied period in the region. The results indicated similar very dry events for the selected indicators in the 6-month period. Also, the rainfall trend for the period of 2015-2022 was taken into consideration to examine the rainfall of the last eight years. The results show that precipitation has decreased in recent years and has a downward trend in most months of the period in question, and the possibility of flood events due to sudden showers in the region has increased due to the continuation of droughts experienced in the years before 2015. Investigating soil moisture and vegetation for the selected period in the study area is also important for the evaluation of the drought level. Evaluation of the available land (vegetation) cover maps of the years 1975, 1985, 2000, 2010, 2020 and 2022 show that the vegetation cover has weakened over the years, and it has been evaluated as an indicator that the danger of drought in the region has increased.

An Investigation of the Spatial and Temporal Characteristics of Extreme Dry and Wet Events across NLDAS-2 Models

Abstract Extreme hydrological events (including droughts and floods) produce severe social and economic impacts. Monitoring hydrological processes from remote sensing is necessary to improve understanding and preparedness for these events, with current missions focusing on a range of hydrological variables (i.e., SWOT, SMAP, and GRACE). This study uses output from three state-of-the-art land surface assimilation models and an event clustering algorithm to identify the characteristic spatial and temporal scales of large-scale extreme dry and wet events in the contiguous United States for three major hydrological processes: precipitation, runoff, and soil moisture. We also examine the sensitivity of extreme event characteristics to model resolution and assess intermodel differences. We find that models generally agree in terms of the mean characteristics of events: precipitation dry events are of shorter duration in comparison with soil moisture and runoff events, and more intense events tend to be smaller in area. We also find that mean spatial and temporal characteristics are highly dependent on model resolution—important in the context of detecting and monitoring these events. Results from this study can be used to inform land surface model development, extreme hydrology event detection, and sampling requirements of upcoming remote sensing missions in hydrology. Significance Statement Understanding the fundamental characteristics of dry and wet extreme events (droughts and floods) is of importance for improving our preparedness and response to events, as well as for designing satellite observing systems that can adequately monitor them. Here we use output from land surface models to determine the average size and duration of large-scale extreme events for the contiguous United States using fine temporal data. We find that events that are most extreme—the most severe floods and droughts—tend to be shorter in duration and smaller in size. We also present an assessment of how three commonly used land surface models detect extreme hydrological events, which is important for assessments based on models. These findings are important for understanding the proportion of events that may be not adequately resolved by current hydrology remote sensing missions.

Navigating the drought: upstream migration of a small-sized Cypriniformes (Telestes muticellus) in response to drying in a partially intermittent mountain stream

River flow intermittence is a natural phenomenon intensified by human activities, such as water abstraction and the effects of climate change. A growing number of rivers are predicted to experience intermittent flows, which may impact the diversity and abundance of freshwater species. Dry riverbeds directly diminish the availability of habitats for freshwater organisms, and suitable environments can turn into ecological traps with reduced survival rates, posing a significant threat to population persistence. Even though fish movements can enable drought-affected populations to persist, little is known about individual fish movement between intermittent and perennial reaches. Here, we study the movement of individual PIT-tagged Italian riffle dace (Telestes muticellus) in an intermittent and perennial river reach before, during and after two severe drying events. A high proportion of fish from the intermittent reach survived the drying riverbed through directed upstream migration. This was manifested in fish living in the intermittent reach of the river displaying significantly higher linear ranges, and net travelled distances during the monitoring period than fish in the perennial reach, which remained resident with limited linear range and net distances travelled. This finding underscores the importance of conserving longitudinal river connectivity in the face of increased water scarcity and intermittent flow patterns.

Characterizing extreme drought and wetness in Guangdong, China using global navigation satellite system and precipitation data

As global temperature rises, the frequency of extreme climate events, e.g., severe droughts and floods, has increased significantly and caused severe damage over the past years. To this regard, precipitation efficiency, a crucial meteorological parameter, could provide valuable insights for a better understanding of the patterns and characteristics of these extreme events. In this study, taking Guangdong province as an exemplary region, we first obtained long-term and high-resolution historical records of precipitation efficiency by integrating the observations from a dense network of Global Navigation Satellite System (GNSS) stations with precipitation data, and then characterized the extreme drought and wetness through climate indices. We found a distinct seasonal trend in precipitation efficiency in Guangdong, with annual fluctuations ranging from 10 to 25%. Notably, precipitation efficiency is higher in proximity to the Pearl River Delta Plain and gradually decreases towards the east and west. The occurrence of anomalous peaks and valleys in precipitation efficiency generally corresponds to dry and wet conditions, respectively. A total of 9 extreme wet events and 6 dry events occurred from January 2007 to May 2022, with durations from 3 to 6 months. Our results also demonstrated that both wet and dry frequencies exhibit an increasing trend with the expansion of the time scale, and the frequency of extreme events near the Pearl River Delta Plain surpasses that of other regions. Furthermore, the propagation time from meteorological anomalies to agricultural and hydrological anomalies is about 3 months. The periodic characteristics of meteorological anomalies are identified as the primary driver for other anomalous periodic patterns. Our work unveils the long-term dynamic behavior of precipitation efficiency, as well as the characteristics of extreme drought and wetness events in the regions characterized by intricate land–atmosphere interactions.

Sedimentology and chronostratigraphy of the Apt Basin, Southeastern France: lacustrine response to late Paleogene cooling and regional rifting

The Apt Basin, sub-basin of the wider Manosque Basin of southeastern France, contains deposits of Eocene-Oligocene lake systems that were part of a broader network of evaporative lakes and lagoons spread across the European Cenozoic rift system. The onset and mechanisms of subsidence in the rift system, the interconnectivity of these lakes, and their response to the transition into the Oligocene icehouse are poorly understood. This study aims to clarify these points by examining the stratigraphy and depositional environments in the Apt Basin. We correlate and date Eocene to lowermost Oligocene geological units using a basin-wide facies model combined with sedimentological and geochronological approaches. We show the existence of three lacustrine phases, each separated by complete lake drying events: (1) an Ypresian (?) − Lutetian lake-marsh system dominated by palustrine carbonates; (2) a Bartonian (?) − Priabonian siliciclastic fluvio-deltaic and saline lake system; and (3) a lower Rupelian saline carbonate lake system. The presence of a lake system during the Ypresian (?) − Lutetian suggests an onset of basin subsidence before most other basins of the rift system in southeastern France, and is associated with the late Pyrenean deformation phase. The initiation of the second lacustrine phase marks the beginning of E-W extension and the formation of the Apt Basin as an individual horst & graben system. Based on facies distribution, we demonstrate the hydrological isolation of the Apt Basin from other basins and the improbability of any marine connection during the first two phases. This isolation is less certain for the third phase. We show a close synchronicity between the second lake drying event and the Eocene-Oligocene Transition. The third lacustrine phase, dominated by carbonate production and low siliciclastic input, is interpreted as reflecting a long-term decrease in surface runoff associated with the fall into the Oligocene icehouse.

Future projections of extreme rainfall events in Indonesia

AbstractPrevious evaluations of coupled climate models have indicated that under the influence of global warming precipitation extremes, including those over Indonesia, are expected to intensify. Here, we examine the most recent future projections of extreme rainfall in Indonesia using 24 global climate models from the Coupled Model Intercomparison Project Phase 6, consisting of 11 low resolution (LR) and 13 medium resolution (MR) models. The performance of these models is evaluated against Climate Hazards Group InfraRed Precipitation with Station data observations and realistically reproduce Indonesia's mean climatology over the period assessed (1987–2014). Overall, both LR and MR multi‐model ensemble means (MMEM) outperform individual models. Interestingly, extreme rainfall projections vary across different seasons, time periods, spatial resolutions and climate change scenarios. The LR and MR MMEMs project a continuous increase in wet extremes (R95p and Rx5d) during the wet season across most of Indonesia over the 21st century. Conversely, dry extremes (consecutive dry days [CDD]) are projected to increase (decrease) over the south (north) during the wet season but increase countrywide during the dry season. We show that future extreme wet and dry events are projected to be more frequent and intense, with upper extreme values surpassing historical records. The MR models project smaller changes in extreme wet indices than the LR models but simulate a more prolonged extreme dry index. Key findings here indicate that forthcoming instances of extreme rainfall present substantial hazards, necessitating the implementation of adequate preventative measures by policymakers, particularly within densely inhabited regions, such as Java.