# Characteristics of Summer Flash Drought and Its Effect on Maize Growth in Liaoning Province, China
###### Abstract  
Flash droughts, characterized by their abrupt onset and rapid intensification, are predicted to increase in frequency and severity under global warming. Understanding the incidence and progression of a flash drought and its impact on maize growth is crucial for maize production to withstand flash drought events. This study used the evaporative demand drought index (EDDI) method to evaluate the incidence of summer drought in Liaoning during the period 1961-2020. It examined the incidence and characteristics of summer flash droughts in Liaoning Province in the period of 1961-2020 and evaluated the factors responsible and the impact on maize during the critical development period. The ratio of the number of stations recording a disaster to total number of stations (IOC) curve, i.e., the ratio of the number of stations recording disasters and total stations, for summer flash droughts in Liaoning showed an upward trend during the period of 1961-2020, with large-scale, regional, and local flash droughts occurring in 8, 10, and 31 years, respectively. Summer flash droughts in Liaoning were mainly in the extreme drought category and ranged in frequency from 10% to 20% in most areas. Before the flash drought occurrence in three typical years (1989, 1997, and 2018), a precipitation deficit without large-scale high-temperature events was observed, and the cumulative water deficit caused the flash drought. Regional or large-scale high-temperature events were often accompanied by flash droughts, and the drought intensified rapidly, owing to the influence of heat waves and water deficits. Summer flash droughts caused a reduction in total primary productivity (GPP) of maize by more than 20% in most areas in the three typical years. The yield reduction rate in 1989, 1997, and 2018, was 27.6%, 26.4%, and 5%, respectively. The degree of decline in maize productivity and yield was associated with the onset and duration of the flash drought. The atmospheric conditions of summer flash droughts were characterized by high-pressure anomalies and atmospheric subsidence, which were unconducive for precipitation but conducive to flash drought occurrence. The continuous high-pressure anomaly promoted the maintenance of the flash drought. flash drought; heat wave; maize growth; evaporative demand drought index; effects 12344  
slowly develop over 1 month or more [3]. Compared with a conventional drought, a flash drought may lead to rapid soil desiccation and crop damage. Owing to its rapid onset, it reduces the period available to mitigate its impact and may potentially cause greater harm to agriculture and the economy. In the summer of 2012, a flash drought in the midwest of the United States caused wide-ranging crop losses and resulted in a 26% reduction in crop yields [4]. Subsequently, the study of flash droughts has attracted widespread attention. In the summer of 2013, 13 provinces in southern China experienced a flash drought lasting less than 1 month, resulting in crop damage to an area exceeding 2 million ha [5]. In early 2018, a flash drought in Queensland, Australia, severely impacted agriculture [1]. In the late summer of 2019, a flash drought in South China led to a paddy wilt area of 2.35 million ha [6]. In the summer of 2022, an unprecedented high-temperature event occurred in the northern hemisphere, triggering a massive flash drought in the Yangtze River Basin in China, affecting 60.9 million ha of crops [7]. These examples illustrate that extreme drought can develop rapidly and severely damage crops through soil desiccation [8]. The transformation of a flash drought into a prolonged drought will cause devastating effects [6]. Therefore, it is critically important to accurately and quickly identify flash droughts and clarify their effect on agriculture for early warning and disaster mitigation [9]. The study of flash droughts is still in its infancy.