# Characteristics of Summer Flash Drought and Its Effect on Maize Growth in Liaoning Province, China
###### Abstract
Disagreement remains regarding the formation and driving factors of flash drought, but flash drought events are generally characterized by their abrupt onset and rapid intensification [10]. In the past decade, some authors have attempted to use indicators to identify and monitor flash droughts, with three types of methods mainly employed. The drought index method uses a drought index to identify flash droughts, such as the evaporative stress index, standardized evaporative stress ratio, and evaporative demand drought index (EDDI) [11; 12; 1]. The multi-index threshold method identifies flash droughts based on the anomaly threshold of multiple indices; for example, a flash drought is recognized when the soil moisture anomaly, evapotranspiration anomaly, temperature anomaly, and other variables attain a certain threshold [13; 14]. The soil moisture percentile method determines the occurrence of flash drought according to the rate of decrease in soil moisture percentile and/or drought duration [15]. Among these indicators, the EDDI method, based on atmospheric evaporation demand (E0), was proposed by [PERSON] et al. (2016) [16] and considers radiative forcing and stratospheric forcing in the evaporation process. This index provides continuous information on abnormal evaporation demand in a certain region [12] and has shown considerable potential and adaptability for early warning and quantification of flash droughts [17]. [PERSON] et al. [18] compared and analyzed the EDDI with the United States Drought Monitor (USDM), the standardized precipitation index (SPI), the standardized soil moisture index (SSI), and the evaporative stress index (ESI). Their findings indicated that the EDDI identified droughts earlier than USDM, SPI, and SSI. Additionally, [PERSON] et al. [19] demonstrated that the EDDI could forecast the onset and cessation of flash droughts in advance when assessing the spatio-temporal evolution of droughts in China during 1961-2013. [PERSON] et al. [12] compared the efficacy of the standardized precipitation index (SPI), evaporative stress index (ESI), and EDDI and found that the EDDI and ESI were more useful for monitoring flash drought development. The rate of drought onset is a crucial feature to distinguish conventional droughts from flash droughts [20]. A conventional drought refers to the phenomenon of a water shortage persisting for months or years. A flash drought is a rapidly intensifying process of water shortage in only a few days. The Intergovernmental Panel on Climate Change Sixth Assessment Report states that, with the intensification of global warming, the probability of extreme events, such as heat waves and droughts, will increase globally [21]. Flash droughts may be triggered and exacerbated by compound extreme events [1]. Against the background of global warming, the intensity and frequency of droughts have increased, and the incidence of drought disasters has become normalized, but no consensus has been reached on whether a flash drought is likely to become a \"new normal\" of drought disasters [22]. Previous research indicates that Northeast China is a hot spot for climate change in East Asia and, potentially, on a global scale [23]. It is also a hot spot for flash droughts caused by extreme climatic events, such as droughts and heat waves [15; 24]. Northeast China is one of three \"golden maize belts\" in the world. Climate warming is predicted to cause drought incidence and severity in Northeast China to worsen. A significant increase in the severity of flash droughts in Northeast China is modeled under the RCP4.5 scenario [15]. Under the B2 scenario, maize crop yields are predicted to decline in most areas of Northeast China [25]. Liaoning Province is one of the important grain production bases in Northeast China. In 2018, the maize planted area was 27,130 km\({}^{2}\), which is 78% of the total area of grain crops in Liaoning Province [26].