Abstract
AbstractThis study explored the interannual relationship between autumn Arctic sea ice concentration (SIC) and the subsequent summer precipitation over East Asia (EASP). Since the late‐1990s, the declining SIC in the Kara–Laptev Seas has been significantly correlated with EASP as well as extremely positive anomalies in northern China and intensely negative anomalies in central‐eastern East Asia. However, there was a weak correlation between autumn SIC and EASP before the late‐1990s. Furthermore, the anomalous precipitation pattern in summer and its connection with autumn SIC variability can be explained by the seasonal persistence of continental processes (snow depth and soil moisture) into the spring. In particular, a decreasing SIC was connected with simultaneously positive and negative precipitation anomalies over northeastern China and the Siberian region, respectively, since the late‐1990s and tends to produce corresponding soil moisture anomalies over the Eurasian continent. Declining SIC also favours increased snow depth anomalies in winter over northeastern East Asia. These anomalous signals of surface processes can persist from winter into the subsequent spring, making the connection between the autumn SIC and EASP possible. The Community Earth System Model Large Ensemble simulations further verified these physical processes. More detailed mechanism for this relationship needs to be stressed in further work by numerical simulations. The results have important implications for extending the seasonal prediction validity of EASP. Moreover, before the late‐1990s, SIC‐related circulation anomalies shifted westward and northward as negative precipitation anomalies developed over west Siberia in autumn. As a result, anomalous dry soil conditions in Siberia persisted into the subsequent spring and then led to wetter‐than‐normal conditions through locally negative soil moisture–precipitation feedback before the late‐1990s.
Highlights
To eliminate the possible linear influence of El Nino-Southern Oscillation (ENSO) while exploring the possible mechanism for how autumn Arctic sea ice affects the ensuing summer precipitation pattern over East Asia, we applied a linear regression to the variable, with regard to the simultaneous Nino-3.4 index, and calculated the residual, which was the difference between the raw variable and the regressed variable
We have shown interannual covariation between East Asian anomalous summer precipitation patterns and autumn Arctic sea ice loss in the Kara–Laptev Seas
During the period 1997–2016, associated with autumn Arctic sea ice loss, anomalous wet and dry conditions tend to occur over East Asia and south of Japan, respectively
Summary
East Asian summer (June–August) precipitation (EASP) contributes most of the annual precipitation over East Asia and its interannual variability usually shows a tripole anomaly pattern (Hsu and Liu, 2003; Hsu and Lin, 2007; Wang and He, 2015), with one centre over central-eastern China and Japan and two opposite centres over northern and southern China (Hsu and Lin, 2007; Wang and He, 2015). The PJ pattern, related to active convection over the tropical western Pacific, is a dynamical mode and can draw energy from the summer mean flow and EASP (Nitta, 1987; Kosaka and Nakamura, 2006) Another wave train, the Silk Road pattern, is related to interannual variability of the tripole precipitation pattern by emitting anomalous signals across the Eurasian continent (Hsu and Lin, 2007). Diabatic heating over the Tibetan Plateau affects summer precipitation interannual variability by triggering a Rossby wave (Hsu and Liu, 2003) This precipitation anomaly is tied to the meridional migration of the westerly winds relative to the Plateau region (Hsu and Lin, 2007; Chiang et al, 2017). These past studies mostly concentrated on the linkage between precipitation anomaly patterns and mid- and lower-latitudes circulations
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