Interannual variation of summer rainbelts along the Arctic frontal zones

Rainfall along the Arctic frontal zone plays an important role not only on the regional scale, but also to the global climate system. River runoff from rainfall along the Arctic frontal zone in the two northern landmasses could be an important source of fresh water in the Arctic Ocean basin which induce thermohaline circulation in the global ocean. An interesting aspect of summer rainfall along Arctic frontal zone is regarding its interannual variability: 1) whether a systematic and significant interannual variability can be found in rainfall amount, and 2) what mechanism can drive the interannual variation. These two aspect will be answered in our present study.

First, a significant interannual variability of summer rainfall is eminent along the Arctic frontal zone over the two northern landmasses (Eurasia and North America). Two interesting features of rainfall interannual variability are found: i) regionally different phases with smaller scale, and ii) a clear eastward propagation of seasonal rainfall anomalies. Second, a key mechanism to drive the interannual variation of rainfall is possibly due to year-to-year changes of the transient activity along Arctic frontal zone. With the longitude-time (x-t) diagram and sequenced horizontal plots of rainfall and storm activity, this close relationship between rainfall and storm activity can be substantiated. This result concur with our previous study about the climatological aspects of summer rainfall along boreal forest.

Furthermore, the interannual variability of storm activity can be linked to that of stationary waves in high latitudes. Dynamic relationships between summertime stationary waves and storm activity along the Arctic frontal zone will be discussed.