Abstract
Current seasonal climate predictions mainly reside in the ocean anomalies. However, the prediction skills are generally limited over many extra-tropical land areas where the oceanic effects are relatively weak. In this study, we address the potential of preceding spring soil moisture condition to predict summer hot days over Northeastern China, a typical Northern Hemisphere mid-latitude region. The results show that spring soil moisture condition over Central-Eastern China is closely related with following summer hot days over Northeastern China for the period of 1979–2017. The statistical model based on the preceding spring soil moisture condition yields temporal cross-validated correlation skill of 0.57 for summer hot days over Northeastern China. The spatial pattern correlation skills of independent hindcast experiments for 2009–2017 are also high, ranging from 0.87 to 0.94. Our results can be easily applied to practical prediction of summer hot days over Northeastern China, and help to provide better climate services and reduce the detrimental effects of extreme heat over this extra-tropical region.
Highlights
Accurate seasonal climate forecasts save lives, support agriculture and water resource managements, and avoid or reduce economic losses
The time series of the Empirical Orthogonal Function (EOF) first mode are highly consistent with those of summer hot days averaged over Northeastern China (Fig. 1b)
Northeastern China which is located in middle latitudes of Northern Hemisphere, is increasingly influenced by extreme high temperature events during the summer
Summary
Accurate seasonal climate forecasts save lives, support agriculture and water resource managements, and avoid or reduce economic losses. The slowly varying soil moisture takes a crucial role in modulating surface climate during the summer over some middle and high latitude land areas such as Eastern China via altering local surface heat fluxes and changing regional atmospheric circulation[12,13,14,15]. There are clear evidences that the preceding soil moisture or precipitation conditions provide potentially key sources for predictability of summer hot extremes[28,29,30,31]. We applied correlation analysis to investigate the relationship of spring soil moisture condition with summer hot days over Northeastern China, and identified the key region of spring soil moisture. Regression analysis was adopted to explore the possible underlying physical causes for the association of spring soil moisture condition over the key region with summer hot days over Northeastern China. Prediction skills were tested by using leave-one-out cross-validation and independent hindcast experiments
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