Northeast China cold vortex is the key factor influencing the high-impact agroclimatic events in Northeast China

Abstract

Based on the data from 245 observation stations in Northeast China and the atmospheric reanalysis dataset, we investigate the impact and causes of the Northeast China cold vortex (NCCV) and its different circulation configurations on high-impact agroclimatic events in the past 60 years. The results show that the NCCV, in coordination with large-scale circulations at different geopotential heights, results in anomalous high-impact agroclimatic events. In April, the upper-level jet stream at 30°N over Northeast Asia is more robust, the stronger mid-level NCCV controls Northeast China, and the low-level cold air moves eastward and southward along the rear of the NCCV. This circulation pattern results in the delay in the date for spring temperature to exceed critical temperature stably. Consequently, the sowing, growth and maturation periods for warm-loving crops are postponed. Besides, in April, the upper-level westerly jet at 45°N over Northeast Asia is more intense, the rear portion of the strong mid-level NCCV is located over eastern Northeast China, and the low-level water vapor is transported to Northeast China from the Indian Ocean and the South China Sea. This circulation pattern can lead to an earlier onset of spring soaking rain, thereby increasing soil moisture during the spring ploughing and improving the emergence rate of crops. In June, the upper-level westerly jet at 45°N is more intense, the mid-level Ural blocking high is stronger, and a relatively vigorous NCCV controls eastern Northeast China. Additionally, the low-level water vapor is transported southwestward to Northeast China from the Bay of Bengal and the South China Sea, as well as is transported eastward and northwestward from the Northwest Pacific, leading to a relatively greater number of heavy rainfall days in Northeast China during June, This situation protects crops from the effects of droughts but may pose a risk of reduced yields due to potential flooding.