ENSO events impacts on apple production in Shandong Ⅱ: Changes in agricultural meteorological disasters under different ENSO scenarios and their impacts on apple yield

Apple is one of the dominant fruits in Shandong Province, and its production is profoundly affected by agricultural meteorological disasters. Exploring the evolutionary characteristics of agrometeorological disasters and their influence on local apple production under extreme climate events is of great significance. In this study, based on daily meteorological data, prefectural and municipal apple production statistical data, and monthly ENSO event data from 1991 to 2019 in Shandong, we analyzed the objectives of the study using mathematical statistical analysis and ArcGIS spatial expression. First, the results showed significant regional differences in agrometeorological disasters under different ENSO years from 1991 to 2019. During the period of fruit expansion from June to August, droughts occurred frequently during El Niño years (78 times), and the highest drought frequency was approximately 50%. In neutral years, flooding disasters were relatively serious, occurring up to 60 times. Drought frequently occurred in areas with sufficient heat resources, such as in West and Central Shandong. Rainfall and waterlogging disasters frequently occurred in areas with abundant rainfall resources in South Shandong. In East Shandong and the Jiaodong Peninsula, extreme low-temperature disasters occurred frequently during the apple flowering period from March to May. The number of low-temperature days was approximately 7–9 d·a⁻¹, with a frequency of approximately 60%–100%. In West Shandong and other places, high-temperature heat disasters occurred during the apple fruit expansion period from June to August, with occurrence days of 11–15 d·a⁻¹. Second, the study showed that, under different ESNO events, drought was positively correlated with El Niño years, whereas it was negatively correlated with La Niña years. During the apple growth period from March to October, there was a positive correlation between the Southern Oscillation Index (SOI) and rainfall during El Niño years, while there was a negative correlation between the SOI and rain waterlogging during La Niña and neutral years. Low-temperature disasters were negatively correlated with the SOI in El Niño years, while they were positively correlated with the SOI in La Niña and neutral years during the apple flowering period from March to May. Third, from March to October, the drought in the Jiaodong Peninsula intensified, leading to an increase in the apple yield reduction rate in El Niño years. Furthermore, the impact of rain and waterlogging on apple yield and income was aggravated in neutral years. In La Niña years and neutral years, drought in West Shandong was positively correlated with apple yield reduction rate. Meanwhile, in neutral years, the rainfall in most areas of Shandong was positively related to the reduction rate of apple yield during the apple expansion period from June to August. In El Niño years, the reduction rate of apple yield was less affected by extreme low-temperature disasters but more affected by high-temperature heat damage. The number of days of low temperature increased in most areas of Shandong during La Niña and neutral years, which led to a reduction in the rates of apple yield and risk increase. Owing to the high temperature and drought in the ENSO event, we should prevent the effects of low temperature, rain, and waterlogging on apple yield and quality and ensure the healthy and sustainable production of the apple industry.