By exciting subtropical teleconnections, sea surface temperature (SST) anomalies in the North Tropical Atlantic (NTA) during boreal spring can trigger El Niño-Southern Oscillation (ENSO) events in the following boreal winter, thereby providing a precursor for ENSO predictability. However, this NTA−ENSO connection is not stationary, and it varies considerably over multidecadal timescales, which cannot be directly explained by the Atlantic multidecadal oscillation or the global warming trend. Here we show that multidecadal changes in the NTA−ENSO connection are principally controlled by multidecadal variability associated with the North Atlantic Oscillation (NAO). During the positive phase of the NAO, the amplification of the NTA impact on ENSO mainly arises from strengthening of the boreal spring mean precipitation over the equatorial Atlantic and enhancement of the persistence of NTA SST anomalies, which enhance the NTA influence by exciting stronger and more persistent subtropical teleconnections. Our findings show that multidecadal variability of the NAO is key to understanding the impacts of the NTA SST on the tropical Pacific Ocean.

This study investigates the connection between the North Pacific Victoria mode (VM) during the boreal spring (February–March–April; FMA) and the following boreal winter (January–February–March; JFM) rainfall over South China (SC). The VM is defined as the second empirical orthogonal function mode (EOF2) of sea surface temperature (SST) anomalies (SSTAs) in the North Pacific poleward of 20°N. It is found that the boreal spring VM has a significant positive correlation with the following winter rainfall over SC. Analyses indicate that a strong positive VM during spring can induce an El Niño during the following winter via an air–sea interaction, resulting in the generation of an anomalous anticyclone over western North Pacific (WNPAC). The anomalous southwesterlies along the southeast coast of East Asia associated with the WNPAC favor an abundant supply of water vapor and anomalous ascending motion over SC. As a result, winter rainfall over SC increases. A linear regression model based on the VM shows that the VM can act as an effective predictor of winter rainfall over SC about one year in advance. And it has a higher prediction skill than ENSO in predicting winter rainfall over SC.

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As an important indicator of vegetation coverage, the Normalized Difference Vegetation Index (NDVI) reflects the changing pattern and evolving trend of the environment. In the Loess Plateau, vegetation plays a critical role in soil and water conservation, which strongly affects the achievement of sustainable development goals. The study of the spatial distribution and temporal trends of NDVI is of great practical importance for the planning of soil and water conservation measures, the evaluation of environmental situation. In this study, the NDVI, precipitation and land cover data of the Jing River Basin were collected, the emerging hot spot and cold spot patterns of NDVI were examined, the characteristics of spatial distribution and temporal variation of the NDVI in the basin were analyzed, the impacts on NDVI changes from climate, land cover change have been discussed. The results show that the NDVI in Jing River Basin shows a spatial trend of decreasing from northwest to southeast. The emerging hot spot analysis results show that diminishing cold spot, oscillating hot spot, intensifying hot spot are predominant patterns in the basin.The whole basin shows the statistically significant upward trend of high-value aggregation of NDVI. The temporal trend of NDVI in the basin varies from-0.0171 to 0.0185 per year. The increasing trend of vegetation coverage in the basin is statistically significant. The positive correlation between the NDVI and the precipitation mainly observed upstream of the basin, revealing that the growth of vegetation in the Loess Plateau is more dependent on the water supply from the precipitation. Land cover transition patterns and the land use patterns also impact the spatial-temporal trends of the vegetation coverage in the basin. The study results may helpful for the vegetation restoration, soil and water conservation and sustainable development of the Jing River Basin.

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