Occurrence Of Extremes Research Articles

Recent High Missouri River Basin Runoff Was Unlikely Caused by Climate Change

Abstract October–September runoff increased 6% and 17% in the upper (UMRB) and lower (LMRB) Missouri River basins, respectively, in a recent (1990–2019) climate in comparison with a past (1960–89) climate. The runoff increases were unanticipated, given various projections for semipermanent drought and/or aridification in the North American Great Plains. Here, five transient coupled climate model ensembles are used to diagnose the effects of natural internal variability and anthropogenic climate change on the observed runoff increases and to project UMRB and LMRB runoff to the mid-twenty-first century. The runoff increases observed in the recent climate in comparison with the past climate were not due to anthropogenic climate change but rather resulted mostly from an extreme occurrence of internal multidecadal variability. High runoff resulted from large, mostly internally generated, precipitation increases (6% in the UMRB and 5% in the LMRB) that exceeded simulated increases attributable to climate change forcing alone (0%–2% intermodel range). The precipitation elasticity of runoff, which relates runoff sensitivity to precipitation differences in the recent climate in comparison with the past climate, led to one–threefold and two–fourfold amplifications of runoff versus precipitation in the UMRB and LMRB, respectively. Without the observed precipitation increases in the recent climate in comparison with the past climate, effects of human-induced warming of about 1°C would alone have most likely induced runoff declines of 7% and 13% in the UMRB and LMRB, respectively. Ensemble model simulations overwhelmingly project lower UMRB and LRMB runoff by 2050 when compared with 1990–2019, a change found to be insensitive to whether individual realizations experienced high flows in the recent climate. Significance Statement Declines in Missouri River basin runoff under climate change pose serious threats to communities that depend on riverine transport, irrigated agriculture, and aquatic recreation. Concerns arising from reports and projections of semipermanent drought in the basin have yet to be realized; observed runoff was greater in a recent climate (1990–2019) than in a past climate (1960–89). We found that the observed runoff increase from past to recent climates was due not to anthropogenic influences but rather to internal multidecadal variability that led to unlikely precipitation increases (<10% probability) that overwhelmed the drying effect of warming temperatures. Model simulations indicate that a modest reduction in runoff of ∼7%–15% was most likely from the past climate to the recent climate.

Joint extreme risk of energy prices-evidence from European energy markets

We investigate joint tail events behavior of prices risk in European energy markets and to explore its interlinkages with supply and demand, financial market panics, policy uncertainty, and environmental regulation. Results reveal that extreme occurrences have a short-term memory, and the occurrence of extreme high prices lowers the likelihood of extreme high prices the following year, in contrast to extreme low prices, indicating a negative seasonal impact. The influence of same extraordinary events on extreme highs and extreme lows is asymmetric. Additionally, different exogenous shocks have varying effects on extreme pricing, as shown through intervention analysis under several shock scenarios.

Disaster management and its importance: a review paper of Dakshina Kannada and Kodagu districts, Karnataka, India

An extreme occurrence within the earth’s system that causes human fatalities, injuries, and property destruction is referred to as a “disaster” from a social perspective. Disaster management is one of the most critical topics around the world. Many countries are getting affected because of its high magnitude impact on economy and loss of life. The Karnataka government must always be on guard and ready to meet problems due to the frequent natural disasters like landslides, floods, droughts, and human-induced dangers. In order to lessen the effect of disasters on the community, the Government of Karnataka has built enhanced institutional structures for disaster risk reduction. The main aim of the review paper of this, is to create awareness about the situations occurring due to any form of disasters and to develop preparedness in younger generation to face disaster situations.

대기의 강(Atmospheric River)이 남한의 스톰과 강수 특성에 미치는 영향

Atmospheric rivers (ARs) that are characterized by an elongated plume of intense vertically-integrated water-vapor transport (IVT) in the atmosphere, are critical in the occurrence of heavy precipitation and hydrologic extremes, especially in the mid-latitudes, in addition to the poleward water-vapor transport. Although ARs affect regional hydrology and can lead to natural disasters, few studies have examined the relationship between ARs and continuous precipitation events like storms. This study analyzes the climatology of AR-related precipitation in South Korea (SK) on the basis of storm events. In SK, AR storms undergo a well-defined annual cycle with a peak in July and outnumber non-AR storms in all months. AR (non-AR) storm duration exhibits an annual cycle with the peak in August (no systematic annual cycle). AR storms are related to larger (smaller) IVT over East Asian coastal regions (western North Pacific) compared to non-AR storms. The IVT difference appears to lead to precipitation differences such that AR storms dominate non-AR storms in monthly and annual-total precipitation, especially in summer. The effects of AR storms on monthly storm-total and storm-mean precipitation are strongest in the central (July) and southern (August) parts of SK and decrease gradually towards the north. Seasonal variations in the occurrence and intensity of AR storms and associated daily precipitation in SK are characterized by a small number of heavy-precipitating AR storms in June and September and a large number of heavy-precipitating AR storms in July and August.

Assessment of changes in return levels of historical and projected high and low flows of upper Euphrates basin in Turkey using nonstationary models.

Owning to climate changes and other anthropogenic interventions, the frequency and return levels of extreme flows cannot be treated as stationary. This study quantifies the changes in return levels by fitting the stationary and nonstationary frequency distribution models for annual and seasonal high and low flows of upper Euphrates basin during historical and two projection periods. The projected flows of three selected sub-basins in the upper Euphrates were obtained using HBV-light hydrological model forced by projected daily precipitation and temperaturedriven from and the most representative regional climate model (RCM) for the study area within the CORDEX-Euro domain. During the historical period, analyses suggest that half of the stations exhibited an increase in return levels (up to 13.5% with GEV), while the remaining four sub-basins experience a decrease in the return levels (up to 27% with GEV). With few exceptions, most of the sub-basins experience an increase (up to 80% with GEV) in return levels of yearly low flows. With few exceptions, the return level of low flows for all seasons generally increases; however, directional variability for high flows is observed. The changes in return levels of yearly projected flows are consistent with historical results in indicating the direction of impact for both near future and far future periods. A decrease in return levels (up to 35% and 22%) in yearly high flows and an increase (up to 100% and 40%) during the near future and far future, respectively. It is projected that the floods of a given return level in the selected sub-basins are becoming milder across all three periods. However, some directional inconsistencies are noted in nonstationarity impact at seasonal scale through projection periods. On yearly basis, the decreasing high flow along with increasing low flow quantiles suggests that the range of extreme occurrences is shrinking. The nonstationarities in high flows as well as low flows should be incorporated in design and development of water resources schemes in the study area.

Characterizing the Synoptic-Scale Precursors of Extreme Precipitation Events in the Southeastern Edge of the Tibetan Plateau: Anomalous Evolution of Atmospheric Dynamic-Thermal Structure

Extreme precipitation events frequently occur at the southeastern edge of the Tibetan Plateau (SETP), causing severe disasters. In this study, we selected the top 100 regional extreme precipitation events over the SETP region during the period of 2001–2020, and analyzed their evolutionary characteristics of large-scale thermodynamic anomalies prior to the extreme precipitation events occurring, with the aim of exploring their precursor signals. The results show that, accompanying the wave train propagating across the Eurasian continent and reaching East Asia, the extreme events over SETP during the summer season are dominated by the background large-scale atmospheric circulations characterized by the strengthened Southern Asia high (SAH), the westward-extended Western Pacific subtropical high (WPSH), and an intensified eastern Asia trough. Additionally, an analogue of low-level vortex embedded in the background large-scale circulations is developed at least 4 days prior to the occurrence of extreme events. Under the combined effects of these anomalies, the warm and cold air converge in the SETP area. Further analysis also suggests that the upper-troposphere divergence aloft combined with lower pressures at surface level lead to the upward vertical motion of circulations, along with the enhanced water-vapor transport conveyed both by the East Asian summer monsoon and the Indian summer monsoon. All anomalies mentioned above provide the favorable environment for the occurrence of precipitation extremes in the SETP region.

Effects of Changing Climate Extremes on Maize Grain Yield in Northeast China

The increased frequency of climate extremes associated with ongoing climate change has the potential for significant impacts on maize grain yield in maize-producing regions worldwide. In this study, we used a modeling approach to investigate the effects of different types of climatic extremes on maize grain yield in Northeast China. We combined annual mean air temperature and accumulated precipitation data and divided the climate years into 9 categories, using the 10th and 90th percentiles as extreme thresholds. The climate data were represented by 1 normal climate type, 4 individual climate extremes, and 4 combined climate extremes. Changes in the frequencies of climate extremes and their impacts on maize grain yields were analyzed for two 30-year periods (period I: 1960–1989; period II: 1990–2019) using the Agricultural Production Systems sIMulator (APSIM-Maize). Compared with period I, the occurrences of the normal climate and all 3 cold-related climate extremes (i.e., cold-normal, cold-humid, and cold-dry) decreased during period II, while occurrences of the other climate extremes increased. Moreover, according to the APSIM-Maize model, the estimated yield in the years with a normal climate decreased by 4.01%; the 3 cold-related climate extremes increased yields by 26.56%, 12.10%, and 6.68%, respectively; the 2 warm-related climate extremes (warm-normal and warm-dry) and normal-humid years decreased estimated yields by 6.39%, 24.12%, and 5.10%, respectively. The increase in the occurrence of warm-humid years increased the estimated yield by 11.69%. This work confirms the adverse effects of warmer temperatures in the absence of excess rainfall on grain yield and highlights the importance of extremely dry or wet conditions under normal temperature conditions.

Anthropogenic Forcing Decreased Concurrent Soil Drought and Atmospheric Aridity in the Historical Period 1850–2013

AbstractAs awareness of the importance of anthropogenic climate change has increased, attention is being focused on “compound extremes,” such as co‐occurring soil drought (low amounts of soil moisture, SM) and atmospheric aridity (high vapor‐pressure deficits, VPD), because of the disproportionate impacts of such extreme conditions on natural and societal systems. Few advances, however, have been made in isolating the net effect of anthropogenic forcing on the occurrence of such compound extremes. Nine Earth System models (ESMs) under natural‐only and fully‐forced simulations from Phase 6 of the Coupled Model Intercomparison Project (CMIP6) indicated that the presence of anthropogenic forcing in the historical period 1850–2013 weakened the coupling between SM and VPD and thus decreased the frequency of compound drought and aridity globally. The anthropogenically induced decrease in the strength of land–atmospheric feedbacks, which offset the drying trend effects of global warming by countering the expected natural correlation between SM and VPD, appears to have been responsible for the relative rarity of concurrent drought and aridity in the historical period. We also modeled independently the anthropogenic forcings of aerosols and greenhouse gases (GHGs) to further highlight that the widespread weakening of land–atmospheric feedbacks may have been associated primarily with the cooling effects induced by increases in anthropogenic emissions of aerosols, because the increase in intensity and frequency of compound drought and aridity that might have been expected from rising GHG concentrations was widely counter‐balanced until very recently by an aerosol‐driven cooling, particularly for the middle and high latitudes of the Northern Hemisphere. This finding indicates that the trade‐off between these two main anthropogenic forcings may determine future patterns of concurrent drought and aridity in a changing climate. If global emissions of anthropogenic aerosols decrease in the future, as expected, our results imply a renewed strengthening of land–atmospheric feedbacks, and thus an intensification of concurrent drought and aridity.

Increasing interannual climate variability during crop flowering in Europe

Climate change has increasingly adverse effects on global crop yields through the occurrence of heat waves, water stress, and other weather-related extremes. Besides losses of average yields, a decrease in yield stability—i.e. an increase in variability of yields from year to year—poses economic risks and threatens food security. Here we investigate a number of climate indices related to adverse weather events during the flowering of wheat, maize and rapeseed, in the current cultivation areas as well as the main European producer countries. In 52 projections from regional climate models, we identify robust increases in the interannual variability of temperature, precipitation and soil moisture by ∼+20% in standard deviation in the model median. We find that winter wheat is most exposed to variability increases, whereas rapeseed flowering escapes the largest increases due to the early flowering time and the northern locations of cultivation areas, while the opposite (escape due to southern locations and late flowering) is true for maize to some extent. Considering the timing of crop development stages, we also find a robust increase in the variability of the temporal occurrence of flowering, which suggests a decreased reliability in the timing of crop stages, hampering management steps like fertilization, irrigation or harvesting. Our study raises concerns for European crop yield stability in a warmer climate and highlights the need for risk diversification strategies in agricultural adaptation.

Mixture Probability Models with Covariates: Applications in Estimating Risk of Hydroclimatic Extremes

Modeling of extreme events is important in many scientific fields, including environmental and civil engineering, and impacts and risk assessments. Among available methods, statistical models that allow estimating extremes’ frequency and intensity are regularly used in procedures to anticipate potential changes in extreme events. Extreme value theory provides a theoretical basis for statistical estimation of extreme events using frequency analysis. The challenge in modeling is knowing when to use the block maxima method or the peaks-over-threshold (POT) method. Each has its drawbacks. POT describes the main characteristics of the observed extreme series; the threshold selection is always challenging and might affect the accuracy of the simulated results and the credibility of changes in extreme values. To encompass this challenge, mixture models offer more flexibility to represent samples with nonhomogeneous data. This study presents the gamma generalized Pareto (GGP) mixture model for estimating risk occurrence of hydroclimatic extremes. The model was developed in its general form, whereas the observed hydrometeorological extreme events depend on multidimensional covariates. A maximum likelihood algorithm is proposed to estimate the parameters with a constraint on the shape parameter of the generalized Pareto (GP) distribution. A Monte Carlo (MC) simulation compared the proposed model with the classical POT approach, with a fixed threshold, and the annual maximum series of streamflow. The approach was applied using a daily hydrological data set from an observed station located in the Saint John River at Fort Kent (01AD002), New Brunswick, Canada. The results show a flexibility to model extremes for dependent or nonstationary time series and adequately describes the central part of the observed frequencies, as well as the tails.

On the Systematic Occurrence of Compound Cold Spells in North America and Wet or Windy Extremes in Europe

AbstractThe repeated co‐occurrence of cold spells over Eastern North America and wet or windy extremes over Western Continental Europe during recent winters, has led to hypothesize a link between the two. Here, we analyze the interplay between the large‐scale atmospheric circulation and co‐occurring cold spells in North America and wet or windy extremes in Europe. We collectively term these occurrences compound cold–wet–windy extremes. We leverage a recent approach grounded in dynamical systems theory, which provides an analytically and computationally efficient analysis of spatially resolved, multivariate climate extremes. We find that there are specific, recurrent large‐scale atmospheric circulation patterns systematically associated with both the individual extremes and co‐occurring cold–wet–windy anomalies. Evidence for this is also found when focusing on compound cold–wet–windy extremes, although with a weaker signal. This motivates further analyses focusing specifically on the statistics and drivers of these compound extreme occurrences.

Simulating hydrological extremes for different warming levels–combining large scale climate ensembles with local observation based machine learning models

Climate change has a large influence on the occurrence of extreme hydrological events. However, reliable estimates of future extreme event probabilities, especially when needed locally, require very long time series with hydrological models, which is often not possible due to computational constraints. In this study we take advantage of two recent developments that allow for more detailed and local estimates of future hydrological extremes. New large climate ensembles (LE) now provide more insight on the occurrence of hydrological extremes as they offer order of magnitude more realizations of future weather. At the same time recent developments in Machine Learning (ML) in hydrology create great opportunities to study current and upcoming problems in a new way, including and combining large amounts of data. In this study, we combined LE together with a local, observation based ML model framework with the goal to see if and how these aspects can be combined and to simulate, assess and produce estimates of hydrological extremes under different warming levels for local scales. For this, first a new post-processing approach was developed that allowed us to use LE simulation data for local applications. The simulation results of discharge extreme events under different warming levels were assessed in terms of frequency, duration and intensity and number of events at national, regional and local scales. Clear seasonal cycles with increased low flow frequency were observed for summer and autumn months as well as increased high flow periods for early spring. For both extreme events, the 3C warmer climate scenario showed the highest percentages. Regional differences were seen in terms of shifts and range. These trends were further refined into location specific results. The shifts and trends observed between the different scenarios were due to a change in climate variability. In this study we show that by combining the wealth of information from LE and the speed and local relevance of ML models we can advance the state-of-the-art when it comes to modeling hydrological extremes under different climate change scenarios for national, regional and local scale assessments providing relevant information for water management in terms of long term planning.

The Copula Application for Analysis of the Flood Threat at the River Confluences in the Danube River Basin in Slovakia

In hydrological practice, individual elements of the hydrological cycle are most often estimated and evaluated separately. Uncertainty in the size estimation of extrema discharges and their return period can affect the statistical assessment of the significance of floods. One example is the simultaneous occurrence and joining of extremes at the confluence of rivers. The paper dealt with the statistical evaluation of the occurrence of two independent variables and their joint probabilities of occurrence. Bivariate joint analysis is a statistical approach for the assessment of flood threats at the confluence of rivers. In our study, the annual maximum discharges monitored on four selected Slovak rivers and their tributaries represent the analyzed variables. The Archimedean class of copula functions was used as a set of mathematical tools for the determination and evaluation of the joint probability of annual maximal discharges at river confluences. The results of such analysis can contribute to a more reliable assessment of flood threats, especially in cases where extreme discharges occur simultaneously, increasing the risk of devastating effects. Finally, the designed discharges of the different return periods calculated by using the univariate approach and the bivariate approach for the gauging station below the confluence of the rivers was evaluated and compared.

Observing the recent floods and drought in the Lake Victoria Basin using Earth observations and hydrological anomalies

The Lake Victoria Basin, home of Africa’s largest freshwater lake, experienced extensive floods in 2019–2020 and anomalous drought conditions in early 2022. Both antithetical hydrological events raised concerns for an estimated 35 million people within the basin who are vulnerable to these continually recurrent hydrometeorological extremes. While there is a need for high-resolution spatial and temporal hydrological monitoring, in-situ observations are limited and insufficient within the basin. This study assesses the capability of publicly available Earth observations and models to capture the occurrence of recent hydrological extremes within the Lake Victoria Basin. Spatial and temporal comparisons of the following hydrological variables are conducted within the Lake Victoria Basin from June 2002 – June 2022: precipitation, evapotranspiration, runoff, soil moisture, lake height, and total water storage anomaly (TWSA). Results from the time series and spatial analyses confirm that the anomalous wet and dry events respectively occurred from October 2019 – March 2020 and November 2021 – March 2021. The observations also indicated a quick recovery from the drought event by June 2022. Additionally, a comparison of 9-km soil moisture and 1-km downscaled near-surface soil moisture products improves understanding of wetness spatial variability within the basin. These results were validated using in-situ soil moisture data available through the International Soil Moisture Network, making this the first study to validate the downscaled 1-km soil moil moisture product within the African continent. Methods from this study demonstrate the utility of a diverse array of publicly available Earth observation and model data to improve understanding of recent hydrological anomalies and extreme events within the Lake Victoria Basin. This can be applied to water resources management, particularly in regions lacking sufficient in-situ hydrological data.

Dynamic correlation and risk resonance among industries of Chinese stock market: New evidence from time–frequency domain and complex network perspectives

To sustain market stability, it is crucial to research the impact of risk resonance across industries. In this paper, we demonstrate the dynamic risk resonance between various sectors in the Chinese market. To do so, by using a recently developed method that divides spillover measures based on variance decompositions into their components at different frequency ranges, a set of frequency spillover matrices is obtained to show the overall risk resonance within sectors. Second, we use a complex network to investigate the risk contagion path among different industries. The research results show that: (1) the risk resonance effect varies significantly over time; (2) during our sample period, the transportation and utilities industries are net transmitters; (3) the risk resonance mechanism is frequency dependent. Spillovers generated at low-frequency, extreme occurrences have a long-lasting effect on the industry’s risk resonance; and (4) extreme events such as the financial crisis and the COVID-19 will enhance the risk resonance effect. The results of our research can provide a reference for market participants to formulate corresponding regulatory and investment strategies.

Exposure of Portuguese viticulture to weather extremes under climate change

Grape berry quality and yield are notably influenced by complex multi-scale interactions between grapevines and local environmental conditions. In established wine-growing regions, bestowing to local climatic conditions, yield and quality are mostly optimized, planting the best wine variety and applying specific cultural practices. Thus, the sustainability of the winemaking sector worldwide is being challenged by ongoing climate change, requiring adaptation at different levels. Climate change will inflict progressively dry and warm conditions on Portuguese vineyards, with changes in frequency and intensity of weather extremes. However, the future projections of these extreme events and their potential impacts on viticulture are less understood. For this purpose, in this study, seventeen climate extreme indices were calculated for the Portuguese wine denomination of origin regions/subregions, in the historical period (1981–2010) and future periods (2041–2070 and 2071–2100), under the Representative Concentration Pathway 8.5, and based on a five-member ensemble of Regional Climate Model-Global Climate Model chain simulations. Furthermore, a principal component analysis was undertaken for both precipitation and temperature extreme indices independently. We found an increase in temperature extremes in all wine regions in Portugal, particularly in the westernmost regions. Regarding the precipitation extremes, they reveal a lessening effect for future periods, accompanied by a generalized decrease of precipitation, but will remain an important threat in the northeastern regions. Conversely, the dry extremes, potentiating severe droughts, will be significantly strengthened. Lastly, it was possible to identify the most exposed and vulnerable wine regions to weather extremes in future climates. This information is critical for supporting decision-making in the sector, namely for long-term planning, climate change adaptation and risk reduction. Practical ImplicationsIn the winemaking sector, resorting to climate information is an effective way of mitigating climate-related risks to attain specific terroirs. To effectively deliver this information to winemakers, climatic vulnerability needs to be identified regionally, in order to promote suitable and locally adjusted measures and policies. In this study, Wine Protected Denomination of Origin (PDO) in Portugal are the key target of the climate (temperature and precipitation) extreme variability between present and future periods. The results provided and synthesized in this study should be able to inform winemakers by identifying potential areas of risk concerning the ongoing climate change and acting accordingly based on the potential occurrence of these climate extremes in each PDO area. Furthermore, some short-term and long-term strategies are presented to mitigate the general increase in temperature and decrease in precipitation.

Analysis of Flooding Vulnerability in Informal Settlements Literature: Mapping and Research Agenda

The United Nations (UN) emphasizes the necessity of reducing the social and material losses imposed by water disasters, with an emphasis on protecting the most vulnerable social groups to achieve sustainable development goals (SDGs). Several objectives outlined under the SDGs including Goals 1, 11, and 13 concentrate on minimizing vulnerability to disasters and boosting resilience to extreme occurrences. Flooding is an increasingly challenging problem facing cities today, with consequences mostly felt in marginalized communities. Residents of informal settlements are particularly susceptible to the effects of flooding given that they are compelled to live in the most unsafe locations, such as floodplains. This study reviews the current status of flooding research from empirical perspectives globally and in South Africa through systematic literature and bibliometric analysis of 249 peer-reviewed articles on flooding, with a focus on informal settlements. We detect groups of keywords and major research themes. Our analysis shows that studies on flood modeling in informal settlements are inadequate. We synthesized the research to present a body of knowledge on floods in informal settlements. Future research prospects are identified in areas of upgrading housing and infrastructures, policies, integrating indigenous knowledge, and local participation.

Access to special COVID-19 relief from distress grant and livelihood outcome of livestock farming households in Eastern Cape Province, South Africa

<abstract> <p>Unexpected events and shocks constitute greater threats to the attainment of zero hunger targets in Africa and the world over, and in the extreme case, lead to total collapse of the global food system and food supply chain. Consequently, this causes significant loss of critical income sources, renders individuals vulnerable, and further deteriorates households' livelihood outcome and welfare state. Therefore, the need for social protection programs to mitigate the impact of distress and unexpected events, as well as extreme occurrences cannot be over emphasized. This research used dataset from the 1499 households captured in the 2021 South African General Household Survey to investigate whether access to a special relief from distress grant has effect on the livestock farming households' food security status in Eastern Cape Province of South Africa. Descriptive statistics, cross-tabulation, a two-sample t-test, a food insecurity experience-based scale technique, and a fractional outcome model were used to analyze the datasets. Based on access to the grant, households in the non-beneficiary group are significantly distinguishable from the beneficiary counterparts, such that the beneficiary households out-performed the non-beneficiary households in the food break-even and food surplus categories. The findings further indicated the possibility of transition of the beneficiary households' population under the transitory food insecurity category to either the chronic food insecurity status or food break-even status, subject to the effectiveness of the food security policy to which they are exposed. The fractional outcome model also indicated that non-metropolitan resident households (<italic>p</italic> < 0.05), access to the special grant (<italic>p</italic> < 0.01), access to health facilities (<italic>p</italic> < 0.01), age of households' heads (<italic>p</italic> < 0.01), colored, indian and white population groups (both at <italic>p</italic> < 0.01), as well as access to remittance (<italic>p</italic> < 0.01) made significant contributions to the households' food security status. The Wald test indicated that access to the special relief grant had a significant effect on the households' food security status in the study area. The study therefore recommends accelerated investments in various social investment programs as sustained responses to expected and unexpected shocks and occurrences to be able to induce progress and realize more resilient food systems.</p> </abstract>

Understanding heatwave-drought compound hazards and impacts on socio-ecosystems

<p>As the Earth warms, the frequency and severity of weather and climate-related extremes are steadily increasing in most regions worldwide. A critical concern is the simultaneous occurrence of climatic extremes in the same location, referred to as compound events. Among these, Heatwave-Drought Compound Events (HDCEs) are one of the most destructive hazards, exacerbating impacts on human societies and ecosystems more than individual extremes. Therefore, it is necessary to understand the physical mechanisms behind HDCEs and to project their future changes and implications for socio-ecosystems. In this Perspective, we explain the motivation for understanding HDCE dynamics, describe new protocols to explore the water-heat-carbon coupling processes driving HDCEs, and finally outline future changes in HDCEs as well as their impacts on economic development and the carbon cycle.</p>

Linkages between Amplified Quasi-Stationary Waves and Humid Heat Extremes in Northern Hemisphere Midlatitudes

Abstract Humid heat extremes, taking account of both temperature and humidity, have adverse impacts on society, particularly on human health. It has been suggested that quasi-stationary waves (QSWs) with anomalously high amplitudes contribute to the occurrence of near-surface precipitation extremes and temperature extremes in the midlatitudes of the Northern Hemisphere. However, little attention has been paid to the linkages between amplified QSWs and humid heat extremes. Using the ERA5 dataset, we identify amplified QSWs of zonal wavenumbers 5–7 (Wave 5–7) in summer months from 1979 to 2020. These amplified QSWs show clear circumglobal wave patterns horizontally and nearly barotropic structure vertically. Linking amplified Wave 5–7 to wet-bulb temperature (WBT) extremes, we find that amplified QSWs preferentially induce prominently prolonged WBT extremes in specific regions: north-central North America for amplified Wave 5; western United States, south-central Asia, and eastern Asia for amplified Wave 6; and western Europe and the Caspian Sea region for amplified Wave 7. Analyses of physical processes indicate that, accompanied by the amplification of Wave 5–7, the changes in horizontal temperature advection, adiabatic heating associated with descending motion, downward solar radiation, moisture transport and moisture flux convergence, and surface latent heat fluxes largely account for the increase in persistence of WBT extremes. Significance Statement In the context of climate change, humid heat extremes exhibit different changes and impacts from high-temperature extremes, but the physical processes that may cause them remain unclear. This study aims to explore the atmospheric dynamic processes leading to the concurrence of humid heat extremes, which may exacerbate the risk from heat stress in today’s interconnected world. In specific regions over the Northern Hemisphere midlatitudes, durations of humid heat extremes are found to be elevated simultaneously by amplified quasi-stationary waves. We further identify the physical connections between amplified quasi-stationary waves and humid heat extremes over targeted regions. This would help in better understanding the role of changing atmospheric circulations in the humid heat extremes.