Identifying climatic factors and circulation indices related to apple yield variation in main production areas of China

Assessing the impacts of future climate change on crop yields requires basic research into both the major meteorological factors that affect crop yield and the influence that changes to global circulation patterns have on local meterological parameters. For example, the atmospheric circulation and crop “meteorological yield” and the response of meteorological yield to climate change are positively correlated. Using apple (Malus domestica) production as an example, the present work investigated the link between fruit yield and global circulation factors by using yield data from 28 apple-producing counties in Shaanxi province, China, from 1980 to 2015. We used four methods to isolate apple production and applied a Grey relational analysis of 88 meteorological factors and the associated sequential correlation. We extracted the major climate factors based on the high consistency of climatic factors and the variation trend of meteorological yield of apple, and analyzed the main meteorological factors for the meteorological apple yield of three major apple producing areas by analyzing high-impact atmospheric circulation indices. The climate factors included solar radiation, pan evaporation, accumulated temperature, precipitation, wind speed, maximum temperature, minimum temperature, mean temperature, heat injury over several days, number of frost days during flowering, number of freezing days during dormancy, and annual temperature range. The main meteorological factors affecting annual apple meteorological yield were total solar radiation from April to October, evaporation from April to September, precipitation in April and June to August, and minimum temperature in mid-April. The Southern Oscillation Index (SOI) was the circulation index most closely related to total summer solar radiation, pan evaporation, and precipitation. Correlation analysis showed that the polar vortex area index and sea surface temperature index were important circulation indices affecting climate yield in apple regions. The meteorological yields of apples in zones Ⅰ and Ⅲ were significantly correlated with the ENSO period index, mainly in the autumn and winter. Similar to the conclusions of previous studies, the uncertainty of meteorological yield in the Shaanxi fruit region is predicted to increase under future climate change. Keywords: Apple yield, Shaanxi province, Grey relational analysis, Climate factors, Circulation index