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Very long dry spell events occurring during winter are natural hazards to which the Mediterranean region is extremely vulnerable, because they can lead numerous impacts for environment and society. Four dry spell patterns have been identified in a previous work. Identifying the main associated atmospheric conditions controlling the dry spell patterns is key to better understand their dynamics and their evolution in a changing climate. Except for the Levant region, the dry spells are generally associated with anticyclonic blocking conditions located about 1000 km to the Northwest of the affected area. These anticyclonic conditions are favourable to dry spell occurrence as they are associated with subsidence of cold and dry air coming from boreal latitudes which bring low amount of water vapour and non saturated air masses, leading to clear sky and absence of precipitation. These extreme dry spells are also partly related to the classical four Euro-Atlantic weather regimes are: the two phases of the North Atlantic Oscillation, the Scandinavian “blocking” or “East-Atlantic”, and the “Atlantic ridge”. Only the The “East-Atlantic”, “Atlantic ridge” and the positive phase of the North Atlantic Oscillation are frequently associated with extremes dry spells over the Mediterranean basin but they do not impact the four dry spell patterns equally. Finally long sequences of those weather regimes are more favourable to extreme dry spells than short sequences. These long sequences are associated with the favourable prolonged and reinforced anticyclonic conditions

This article pioneers a unique approach to examining generic dry spells, shifting focus from traditional rain‐free period analysis to a crop‐centric perspective that integrates an anticipatory lens inspired by Impact‐based Forecasting (IbF). Moving beyond traditional analyses of rain‐free periods, the article evaluates these impactful within‐season large‐scale agrometeorologically relevant dry spells (LARDS) not by the number of days with minimal or no rainfall but by their impact—specifically, the adequacy of root‐zone soil moisture to meet the optimal requirements of maize crops, as quantified through the Water Requirement Satisfaction Index (WRSI). LARDS were identified in maize‐intensive growing regions of Zimbabwe under two maize planting date scenarios: meteorology‐guided and uninformed. The research characterizes impactful within‐season LARDS occurring at sub‐seasonal to seasonal timescales over 36 years (1983–2018). Findings show that meteorological guidance improves yields while neglecting it results in lower yields. During LARDS, a distinct northwest‐to‐southeast suppressed rainfall pattern emerges over Zimbabwe, extending into neighbouring countries. This pattern is associated with a southwestward or northeastward displacement of Tropical Temperate Troughs (the regional primary rainfall system) relative to the country's location. Furthermore, LARDS exhibit overarching anticyclonic conditions impeding vertical cloud development with notable changes in the key local large‐scale mean climatic features influencing Southern Africa's weather. Specifically, the Mozambique Channel Trough, Angola Tropical Low, Saint Helena High and Mascarene High weaken anomalously, while the Botswana High strengthens during LARDS. Additionally, we demonstrate that LARDS have a northeastward propagation and have atmospheric signatures indicative of being triggered by upstream Rossby waves originating from the south coast of South America. This study presents a crop‐centric approach to analysing dry spell impacts, using the Water Requirement Satisfaction Index (WRSI). Leveraging this metric, it further identifies and characterizes large‐scale agrometeorologically relevant dry spells (LARDS) in Zimbabwe. The study's findings demonstrate that meteorological guidance enhances yield and link LARDS to suppressed rainfall, weakened climatic systems (Mozambique Channel Trough, Angola Tropical Low, Saint Helena High and Mascarene High) and a strengthened Botswana High.

Availability of water resources is significantly affected by changes in seasonal rainfall, with water often in short supply when most needed. The majority of current research focuses on the impacts of multiyear drought, using monthly or annual average rainfall to investigate impacts to water resources. Here, we use daily rainfall to evaluate changes in dry spells lengths, defined as the continuous number of days without rain, and investigate how these changes may impart stresses on water resources in warmer summer seasons globally. We use over 100 years of precipitation and temperature data across the world, arranged into warm and cold groups of years on the basis of mean summer temperature. These warm and cold groups are then compared to demonstrate an overwhelming tendency for warmer summers to contain longer dry spells globally. This difference in dry spell length in warmer summer seasons is argued to have far reaching ramifications in warmer summers. For some of the largest cities in the world, vulnerability of water resources, which is a measure of the magnitude or severity of the water availability deficit, is shown to be on average 30% higher due to longer seasonal dry spells in warmer summers. Such an impact points to a need to reassess water resources plans and policies to include the impacts of seasonal dry spells, especially relating to large urban populations around the world. Plain Language Summary Lack of water is a serious threat to our environment, eco systems, and to human life. Availability of water is projected to get worse with decreases to average rainfall resulting from climate change. Here, we illustrate that periods of continuous days without rain, or dry spells, can also cause damage to the environment and can also result in water shortages for human consumption. This aspect of the length of seasonal dry spells is not usually captured in current projection and modeling. As an alternative to global circulation model results of rainfall, we use historic data classified by mean summer temperature to collect the hottest and coldest years and as an indicator of changes caused by a warming climate. We show that longer dry spells are associated with warmer years globally and that these dry spells do contribute to increasing on the stress on water resources around the world. Key Points Longer periods of continuous dry days in warmer summers, globally Increases stress on water resources due to longer dry spells all around the world Seasonal dry spells also should be considered along with long‐term droughts

This study examines the spatiotemporal variability and trends of rainfall in the central highlands of Abbay Basin using the Integrated Multi-satellite Retrievals for GPM (IMERG-06) dataset. Parameters on onset and cessation dates, dry spells, Coefficient of Variation (CV%), and Standardized Rainfall Anomalies were utilized to evaluate rainfall variability and seasonality. Trend analysis was carried out using Mann-Kendall test and Sen’s slope estimator. The results highlighted a consistent pattern of late onset and early cessation of rainfall. The CV values for annual (10.7%), kiremt (11.7%), and belg (10.6%) seasons rainfall indicate moderate variability, while bega (22.6%) rainfall showed higher variability. SRA findings reveal episodic fluctuations between wet and dry years. The trend analysis demonstrates a statistically significant increasing trend in annual (9.14 mm/year) and belg seasons (6.94 mm/year) rainfall. However, kiremt season exhibited statistically non-significant (p > 0.05) decreasing trend. The temporal variability in rainfall onset, cessation dates and duration significantly impacts agricultural processes such as tillage and planting operations, affecting crop production. While the study area holds potential for agricultural activities, climate variability may reduce productivity. Therefore, the study findings are valuable for agricultural developers, planners and water resource managers. Including additional weather elements is crucial to enhance the precision and reliability of these findings for practical applications.

The intermittent dry spells during growing season of winter or sali rice, cultivated in NBPZ of Assam located in the foothills of Eastern Himalayan region, is a major weather risk causing widespread damage to the crop. Herein, variability of rainfall in Lakhimpur district situated in NBPZ was studied. A significant decreasing trend of annual and seasonal rainfall was observed. Significant decrease in monsoon rainfall and increase in monthly rainfall variability clearly explains the recent rainfall fluctuations with increasing frequency of intermittent dry spells and flash floods. A participatory evaluation trial was conducted in Chamua village of Lakhimpur district having different land situations to identify climate resilient technologies to cope with seasonal drought in sali rice. High-yielding short-duration varieties, viz., Dishang, Luit, Lachit and Kolong, and medium-duration varieties, viz., Basundhara, Mohan, Mulagabhoru and TTB-404 performed consistently better than the long-duration HYV or the traditional varieties under upland and medium land situations, respectively. Though the effect of dry spells on long-duration varieties cultivated on low lands was least, yield of these varieties reduced up to 43.07% when sowing was delayed beyond 23rd of June. Performance of the delayed sown varieties was further declined, when exposed to dry spells at later growth stages. However, adverse impact of dry spells can be managed effectively by replacing farmers’ varieties with short and medium-duration high-yielding varieties in upland and medium lands, respectively, and manipulating sowing time of long-duration varieties for low lands.

South Africa is frequently subjected to severe droughts and dry spells during the rainy season. As such, rainfall is one of the most significant factors limiting dryland crop production in South Africa. The mid-summer period is particularly important for agriculture since a lack of rain during this period negatively afects crop yields. Dry spell frequency analyses are used to investigate the impacts of sub-seasonal rainfall variability on crop yield, since seasonal rainfall totals alone do not explain the relationship between rainfall and crop yields. This study investigated the spatial and temporal occurrences of the mid-summer dry spells based on magnitude, length and time of occurrence in the major maize growing areas of the summer rainfall region of South Africa. Three thresholds of 5 mm, 10 mm, and 15 mm total rainfall for a pentad were used for the analysis of dry spells. Dry spell analysis showed that dry pentads occur during mid-summer with difering intensity, duration and frequency across the summer rainfall region. Annual frequency of dry pentads for the mid-summer period ranged between 0 and 4 pentads for the 5 mm threshold and 1 to 7 for the 10 mm and 15 mm thresholds. The non-parametric Mann-Kendall trend analysis of the dry pentads indicates that there is no significant trend in the frequency of dry spells at a 95% confidence level. The initial and conditional probabilities of getting a dry spell using the Markov chain model also showed that there is a 32% to 80% probability that a single pentad will be dry using the 15 mm threshold. There is a 5% to 48% probability of experiencing two consecutive dry pentads and 1% to 29% probability of getting three consecutive dry pentads. The duration and intensity of dry spells, as well as the Markov chain probabilities, showed a decrease in dry spells from west to east of the maize-growing areas of the summer rainfall region of South Africa.

Daily rainfall at Bagan in the central dry zone of Myanmar was analyzed to identify the occurrence of wet and dry spells of rainfall during the farming period. A wet season was identified from May to October and a dry season from November to April. The wet season can be divided into an early (May–June) and late (August–October) monsoon, separated by an inter-monsoon (July). The bimodal distribution of rainfall makes rainfed agriculture even more challenging in this dry area. A rainy season was defined as a duration that started from the first 5 days with at least 2 wet days (total of at least 10 mm of rainfall) without a maximum dry spell of 10, 15, or 20 days at least for 90 days. A period that satisfies only the onset condition but that is interrupted by a dry spell was classified as a false rainy season. Under the maximum dry spell conditions of 10, 15, and 20 days, rainy seasons were identified 5, 12, and 16 times, respectively. Dry spells up to 20 days long often occur during the farming period in Bagan and should be accounted for farm planning.

Dry spells are one of the climate change hazards that continue to exert pressure on the agriculture sector, hence affecting food security. Understanding dry spell characteristics of an area helps in coming up with interventions and adaptive measures among other advantages. This study aimed at understanding characteristics of dry spells for Malawi by using climate hazards group infrared precipitation with stations precipitation data from 1981 to 2019. The study focused on the spatial distribution, maximum number of dry days, trend of maximum dry days and time of occurrence of dry spells. Data was analysed using Mann–Kendal trend analysis in R software. The results indicate a high number of occurrences of dry spells in the southern region than the other two regions of Malawi. In addition, the southern region experienced the highest maximum number of dry days. However, there is an upward trend for maximum days of dry spells in central region than all other regions. Local scale topographic influences on dry spell occurrence were also apparent. The study further established that the number of dry spell occurrence in the rainfall season starts to increase towards end of March. In this regard, although rainfall season in the study area is considered to be from November to April, the study recommends that growing season should be considered to be November to March so that crops are not affected by end of season dry spells which are common. Farmers should ensure that they plant crops that will mature with this growing period. Article highlights Analysis of dry spells over Malawi from 1981 to 2019 using CHIRPS identified areas prone to dry spells. There is an increase in trend of dry spells in centre with high number of occurrence in the south and that the spatial distribution and trends are influenced by topography, rainfall onset and cessation. Characteristics of dry spells informs optimal crop growing periods.

An analysis of spatial and temporal variations of dry spells was carried out for western Turkey using daily precipitation data of 28 stations from 1966 to 2011. Three indices and four levels of precipitation-per-day threshold were considered. Indices are number (NDS), mean length (MDS) and maximum length (MxDS) of dry spells, and the thresholds are 0.1, 1, 5 and 10 mm/day. The results showed that a general decreasing gradient from north-east to south-west is evident for NDS with exceptionally higher values at south-west at 10 mm/day threshold. Mean MDS depicts an opposite pattern to that of NDS particularly for 0.1 and 1 mm/day. Longer mean MDS values are observed at western and eastern parts for 5 and 10 mm/day. For all threshold levels, there is a clear increasing gradient from north-east to south-west for mean MxDS. Trend analysis showed that the majority of trends of the indices at all thresholds are statistically non-significant at 95% level. It can be concluded that the study area as a whole has experienced a general and slight (statistically non-significant) decreasing tendency for NDS but a general and slight (statistically non-significant) increasing tendency for MDS and MxDS. Over the same period, total annual precipitation has shown statistically non-significant decline at almost all stations. It can be concluded that the slightly decreasing tendency in total annual precipitation has been accompanied by slightly decreasing NDS and by slightly increasing MDS and MxDS. This suggests that the study area has received less precipitation and experienced less frequent but longer duration of dry spells over the period 1966–2011. The droughts in the study area have become relatively worse in terms of not only the total amount of precipitation but also duration of dry periods, although dry periods have occurred less frequently.

Under the possible impact of climate warming, recent changes in dry and wet spells have contributed significantly to climate-related hazards around the world. In this work, spatial and temporal variations in dry and wet spells over Canada are investigated using daily precipitation data from 1979 to 2018. The time-varying relationships between precipitation spells and large-scale climate anomalies are modeled using a nonstationary generalized extreme value (GEV) distribution and Bayesian quantile regression. Over the period 1979–2018, significant changes in dry and wet spells have been observed across Canada, particularly in the southern Canadian Prairies (CP), where both the number and duration of dry spells show positive trends. Dry and wet spells over many parts of Canada are nonstationary under the effects of the El Niño–Southern Oscillation (ENSO) and the Pacific–North American pattern (PNA), with PNA having stronger effects on annual maximum dry spells than ENSO, especially in the central CP and eastern Ontario. For western Canada, the influence of ENSO on dry spells tends to be relatively strong, especially for dry spells of high quantiles, as El Niño generally induces atmospheric moisture deficit. For central Canada, ENSO and PNA have a negative (positive) impact on the wet spell duration of low (high) quantiles. For eastern Canada, PNA is negatively correlated with the duration of wet spells, especially for wet spells of high quantiles. Therefore, a better understanding of the spatial and temporal variability in dry and wet spell return periods will be useful for the effective management of water resources, and for developing effective disaster mitigation measures against the possible social and economic impacts of climate-related hazards.