Decadal shift of the influence of Arctic Oscillation on dust weather frequency in spring over the Middle East during 1974-2019

Dust weather has an impact on human health and climate change in the Middle East. In this study, we examined the influence of the Arctic Oscillation (AO) on spring dust weather frequency over the Middle East at an interannual timescale during 1974-2019. The results show that there was an interdecadal shift of the influence of AO on dust weather frequency in the Middle East, with a correlation coefficient between the AO index and dust weather frequency changing from -0.52 during 1974-1994 period (P1) to 0.49 during 1995-2013 period (P2). During P1, negative correlations between AO index and dust weather frequency were found over the northern Arabian Peninsula, and during P2, positive ones were mostly over the central and southwestern Arabian Peninsula. In the lower and middle troposphere, negative geopotential height anomalies are associated with the negative phase of the AO over South Europe during P1, whereas negative geopotential height anomalies are associated with the positive phase of the AO over Northeast Africa during P2. The negative height anomalies resulted in the occurrence of more low-pressure systems and, thus, dust weather in the Middle East. It is found that the interdecadal shift of the influence of the AO on dust weather was related to an AO-related northward displacement of wave train propagation during P2. Specifically, during P1 period, the northern branch of AO-related wave train dominated over the middle latitudes of the North Atlantic across South Europe to the Arabian Peninsula, which resulted in the negative height anomaly over South Europe in the lower and middle troposphere. However, during P2 period, the AO-related wave train propagation moved northward, and then, the southern branch of the AO-related wave train dominated over the low latitudes of the North Atlantic across northern Africa to the Arabian Peninsula, which played an important role in the formation of the negative height anomalies over Northeast Africa.