Statistical Modelling of Drought Indicators and Evaporation/Transpiration and Their Impact on Determining the Erosion Ability of Winds in Iraq

Geographical studies are concerned with analyzing and interpreting its most important phenomena, especially those related to climate, which in one way or another affect the provision of harsh environmental conditions such as drought, desertification, and others, as well as being one of its prominent manifestations. As these studies are interested in one way or another in determining the mechanism of action in life, as they are interested in determining the various human activities, and in this research, the researchers were interested in adopting (10) Iraqi climatic stations to find and calculate the values of the phenomena referred to from drought, evaporation/transpiration, wind erosion and the strength of wind pressure in Iraq, using an applied quantitative-statistical method to determine the monthly and annual ranges of wind erosion for the period (1986-2018), and by applying the correlation, regression and determination coefficients. As well as cartographic representation using Excel techniques and geographic information systems (GIS).

Quantifying the joint distribution of drought indicators in Borneo fire-prone area

Borneo island is prone to fire due to its large peat soil area. Fire activity in Borneo is associated with regional climate conditions, such as total precipitation, precipitation anomaly, and dry spells. Thus, knowing the relationship between drought indicators can provide preliminary knowledge in developing a fire risk model. Therefore, this study aims to quantify the copula-based joint distribution and to analyze the coincidence probability between drought indicators in Borneo fire-prone areas. From dependence analysis, we found that the average of 2 months of total precipitation (TP), monthly precipitation anomalies (PA), and the total of 3 months of dry spells (DS) provides a moderate correlation to hotspots in Borneo. The results show the probability of the dry-dry period is 26.63, 17.66, and 18.54 % for TP-DS, PA-DS, and TP-PA, respectively. All of these are higher than the probability of the wet-wet period, which is 25.01, 16.12, and 17.98 % for TP-DS, PA-DS, and TP-PA, respectively. Through the probability, the return period of TP-DS in the dry-dry situation 3.2 months/year, meaning the dry situation in total precipitation and dry spells that occur simultaneously could appear about 3 months in a year on average. Furthermore, the return period of PA-DS and TP-PA in the dry-dry situation is 2.12 and 2.22 months/year, respectively. Moreover, the probability of dry spells in dry conditions when given total precipitation in dry conditions is higher than given precipitation anomalies in dry conditions.

Temporal and Spatial Dynamics of Drought in Central Asia during 2002-2017 Based on Grace Data

With the influences of climate change and human activities, the resources and environment of “One Belt and One Road” are facing severe problems and challenges. This study aims to analyze the temporal and spatial dynamics of the drought environment and the response of vegetation cover to the drought by using drought indicators. Gravity Recovery and Climate Experiment (GRACE) drought severity index (GRACE-DSI) and GRACE water storage deficit index (GRACE-WSDI), were calculated to present hydrological drought. Moreover, based on GRACE, Water-Global Assessment and Prognosis (WaterGAP) model, and Global Land Data Assimilation System (GLDAS) data, the groundwater in Central Asia was retrieved to calculate the groundwater drought index called the GRACE Standardized Groundwater Level Index (GRACE-SGI). The results show that the annual precipitation in Central Asia increased slightly at a rate of 0.39 mm/year (p = 0.82) since 2000, while the temperature increased slightly at a rate of 0.05 ℃/year (p = 0.10). The water storage decreased significantly at -0.59 mm/year (p <0.01) and experienced a decrease-increase-decrease process. During the study period, the arid situation in Central Asia deteriorated, especially in the eastern coast of the Caspian Sea and the Aral Sea basin. From 2007 to 2015, the Central Asian environment was generally arid and suffered from different du-rations and degrees of hydrological and groundwater droughts. The drought indicators (i.e., GRACE-DSI, GRACE-WSDI) and the NDVI showed a significantly positive correlation during the growing season. However, the NDVI of cultivated land and grassland distribution areas in Central Asia showed a strong negative correlation with GRACE-SGI. It is concluded that the drought environment in Central Asia affected the growth of vegetation. The continued deterioration of the arid situation may further stress the ecological system in Central Asia.

Demystifying Drought: Strategies to Enhance the Communication of a Complex Hazard

Drought is a complex phenomenon that is difficult to characterize and monitor. Accurate and timely communication is necessary to ensure that affected sectors and the public can respond and manage associated risks and impacts. To that end, myriad drought indicators, indices, and other tools have been developed and made available, but understanding and using this information can challenge end users who are unfamiliar with the information or presentation, or for decision makers with expertise in areas outside of climate and drought. This article highlights a project that aimed to improve the usability and dissemination of drought information for North Carolina (NC) audiences by addressing specific needs for a better understanding of how drought is monitored, the climatic and environmental conditions that can cause or worsen drought, and the impacts occurring in NC’s different sectors and sub-regions. Conducted to support NC’s official, statewide drought monitoring process, the project’s methods and results have utility for other geographies and contexts. The project team designed an iterative process to engage users in the development, evaluation, refinement, and distribution of new resources. Featured products include the Weekly Drought Update infographic, which explains the factors used to determine NC’s drought status, and the Short-Range Outlook infographic, a synthesis of National Weather Service forecasts. Effective strategies included using stakeholders’ preferred and existing channels to disseminate products, emphasizing impacts relevant to different user groups (such as agriculture, forestry, water resources) rather than indices, and employing concise narratives and visualizations to translate technical and scientific information.

Drought in a changing climate – a pan-European view

<p>Hydro-climatic extremes occur on different spatial and temporal scales, ranging from local, short term events, such as heavy storms and flash floods, to large-scale (regional to continental scale), long duration (weeks to years) events, such as drought and heat waves. Extremes affect every aspect of our society and to meet the societal need for preparedness and hazard management, the research community is challenged by underlying, critical science questions, including the need for improved knowledge on governing processes in a changing climate. In 2018, northern and parts of central Europe experienced a severe summer drought and record-breaking, persistent high temperatures led to severe impacts across a wide range of sectors. Wild fires destroyed vast areas in northern Europe, and the drought led to significant impacts on agricultural production and terrestrial ecosystems. Record low river levels disrupted inland waterways and low groundwater levels led to regional water restrictions. As illustrated by the 2018 event, drought effects all components of the hydrological cycle as it propagates from its origin as a meteorological anomaly, to a deficit in soil moisture and finally - if sustained - to below normal streamflow and groundwater levels (hydrological drought). Furthermore, a drying soil affects the partitioning of latent and sensible heat at the land surface, leading to higher air temperatures and thus, a reinforcement of the warming signal (positive feedback). Due to the diverse nature of drought, a large number of drought indicators exists, representing different time scales and type of drought. Simple indices may not be sufficient when applied to the complex and cumulative nature of drought. Often it is a combination of variables or events that leads to extreme drought impacts (compound event). A better understanding of the links between physical drought indicators and key drivers of drought is vital for drought prediction, whereas a better understanding of the links between physical indicators and drought impacts is critical to improve drought preparedness and support drought mitigation. This presentation highlights key achievements in drought research with a special emphasis on the identification of drought events, detection of recent changes, and our ability to model drought, including their spatial and temporal footprint. Focus is on Europe, and it will start introducing some recent extreme drought events – their main drivers, key characteristics, and wider environmental and societal impacts, and will close with an assessment of what the future may bring.</p>

Drought impact links to meteorological drought indicators and predictability in Spain

Drought affects many regions worldwide and future climate projections imply that drought severity and frequency will increase. Hence, the impacts of drought on the environment and society will also increase considerably. Monitoring and early warning systems for drought rely on several indicators; however, assessments on how these indicators are linked to impacts are still lacking. Here, we explore the links between different drought indicators and drought impacts within six sub- regions in Spain. We used impact data from the European Drought Impact Report Inventory database, and provide a new case study to evaluate these links. We provide evidence that a region with a small sample size of impact data can still provide useful insights regarding indicator-impact links. As meteorological drought indicators, we use the Standardised Precipitation Index and the Standardised Precipitation-Evapotranspiration Index, as agricultural and hydrological drought indicators we use a Standardised Soil Water Index and, a Standardised Streamflow Index and a Standardised Reservoir Storage Index. We also explore the links between drought impacts and teleconnection patterns and surface temperature by conducting a correlation analysis and then test the predictability of drought impacts using a Random Forest model. Our results show meteorological indices are best linked to impact occurrences overall, and at long time scales between 15 and 33 months. However, we also find robust links for agricultural and hydrological drought indices, depending on the sub-region. The Arctic Oscillation, Western Mediterranean Oscillation and the North Atlantic Oscillation at long accumulation periods (15 to 48 months), are top predictors of impacts in the northwest and northeast regions, the Community of Madrid, and the south regions of Spain respectively. We also find links between temperature and drought impacts. The Random Forest model produces skilful models for most sub- regions. When assessed using a cross-validation analysis, the models in all regions show precision, recall, or R2 values higher than 0.97, 0.62 and 0.68 respectively. Since we find the models to be skilful, we encourage other types of impact data to be used to investigate these links and to predict drought impacts.

Evaluation of the Perspective of ERA-Interim and ERA5 Reanalyses for Calculation of Drought Indicators for Uzbekistan

The arid and semiarid regions of Uzbekistan are sensitive and vulnerable to climate change. However, the sparse and very unevenly distributed meteorological stations within the region provide limited data for studying the region’s climate variation. The aim of this work was to evaluate the performance of the European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA)-Interim and ERA5 products for the fields of near-surface temperature, humidity, and precipitation over Uzbekistan from 1981 to 2018 using observations from 74 meteorological stations. Major results suggested that the reanalysis datasets match well with most of the observed climate records, especially in the plain areas. While ERA5, with a high spatial resolution of 0.1°, is able more accurately reproduce mountain ranges and valleys. Compared to ERA-Interim, the climatological biases in temperature, humidity, and total precipitation from ERA5 are clearly reduced, and the representation of inter-annual variability is improved over most regions of Uzbekistan. Both reanalyses show a high level of agreement with observations on the standardized precipitation evaporation index (SPEI) with a correlation coefficient of 0.7–0.8.Although both of these ECMWF products can be successfully implemented for the calculation of atmospheric drought indicators for Uzbekistan and adjacent regions of Central Asia, the newer and advanced ERA5 is preferred.

Uncertainties in the variation of compound dry and hot events due to differences in drought indices

<p>Compound dry and hot events (CDHEs) are commonly defined as the concurrent or consecutive occurrences of the two events, which could lead to larger negative impacts than do individual extremes. The variation of CDHEs has gained increased attention in the past decades. Previous studies have detected changes in the frequency, duration, and spatial extent at regional and global scales based on observations and model simulations. However, these studies mainly focus on a single drought indicator. In the past decades, different drought indicators have been applied to characterize drought conditions, such as Standardized Precipitation Index (SPI), and Standardized Precipitation-Evapotranspiration Index (SPEI), and Palmer Drought Severity Index (PDSI). Due to the difference in these drought indicators in characterizing droughts, evaluation of CDHEs based on different drought indices may lead to a different magnitude of changes (or even opposite direction of changes). However, quantitative analysis of the uncertainties in the variation of CDHEs is still lacking. In this study, we quantitatively evaluate the uncertainties of CDHEs variations ove global areas due to differences in drought indices. Results from this study could further our understanding of changes in CDHEs under global warming.</p>