Arctic Influence on the Eastern Asian Cold Surge Forecast: A Case Study of January 2016

Abstract

An extreme cold surge during 21-25 January 2016 resulted in extensive damage to eastern Asian countries. Synoptic diagnoses show that the southward movement of the north Siberian anomalous anticyclone to the midlatitudes was the key process for the cold surge. Operational forecasts from the European Centre for Medium-Range Weather Forecasts show that this event could be captured in the control forecast started on 12 January. Further diagnosis shows that the control forecast started on 11 January missed it, possibly due to uncertainties in the Arctic because the north Siberian anomalous anticyclone is not strong enough due to the erroneous eddy vorticity forcing (EVF) induced by the Arctic initial conditions uncertainty. Therefore, the north Siberian anomalous anticyclone cannot move southward to midlatitude when another anomalous anticyclone comes from the Caspian Sea. Finally, numerical experiments are conducted with the Open Integrated Forecasting System model to verify the role of the Arctic initial conditions. Numerical results show that integration with the ERA5 initial conditions could capture the cold surge in the forecast starting on 12 January, while integration with the ERA-Interim initial conditions could not. Sensitivity experiments with modified Arctic initial conditions show an improved cold surge forecast skill. This improvement may be due to the north Siberian anomalous anticyclone, which is sufficiently strong to move southward when the anomalous anticyclone comes from the Caspian Sea, with accurate EVF induced by the improved initial conditions in the Arctic. This result highlights the importance of the Arctic initial conditions in this eastern Asian cold surge forecast.

Midwinter Breakdown of ENSO Climate Impacts in East Asia

“…However, it is interesting to nd that there is a remarkable and unique breakdown of the ENSO in uence on the EAWM during the midwinter. This collapse lasts about 10 days and mostly occurs in mid-January, when East Asia's climate is at its coldest point of the year, posing a potential threat to local socio-economic activities 37 .…”

The Nature and Predictability of the East Asian Extreme Cold Events of 2020/21

“…Previous studies suggest that the mediumrange and extended-range forecasts of 500 hPa geopotential height in the Northern Hemisphere can be improved with a more accurate initial representation of the Arctic atmosphere (Jung et al, 2014). Recently, Dai and Mu (2020b) investigated a cold surge that occurred in East Asia during 21-25 January 2016 and found that the skill of 10-day weather forecast is sensitive to the atmospheric initial conditions in the Arctic. A possible reason for this concerns the northerly winds which lead to a cold surge, which act to underscore the influence of the upstream Arctic atmosphere (Semmler et al, 2018).…”

Extent of the Impact of Arctic Atmospheric Uncertainty on Extended‐Range Forecasting of Cold Events in East Asia

“…Although the notable global warming trend continues (Huang et al., 2017; C. Zhang et al., 2019), extreme cold events remain a common feature during the winter season. Moreover, some studies have suggested that the frequency of extreme winter cold events has increased in Eurasia during the past two decades (Cohen et al., 2014, 2020; Dai & Mu, 2020; Fu & Ding, 2021; Johnson et al., 2018; Min et al., 2015; Wu et al., 2017; X. Zhang et al., 2012).…”

“…For the extended-range forecast, Jung et al (2014) suggests that the forecast in Eurasia is improved when the Arctic atmosphere relaxed toward the reanalysis data during the course of the forecast, but the result was derived statistically from the climatology. Recently, Dai and Mu (2020) studied the forecasting skill for a cold surge in East Asia that took place during January 2016 and found that the atmospheric initial condition in the Arctic was critical to improving the forecast. All these findings suggest that forecasts in East Asia are sensitive to the atmospheric initial condition in the Arctic.…”