Changes in the Impact of the Autumn Tibetan Plateau Snow Cover on the Winter Temperature Over North America in the mid‐1990s

Abstract

This study investigates the changes in the impact of the interannual variation of autumn snow cover over the eastern Tibetan Plateau (TP; ASCETP) on winter surface air temperature (SAT) over North America (NA) in the mid‐1990s using both observational data and a linear baroclinic numerical model. The index of ASCETP shows an abrupt change with a predominant negative phase before and a predominant positive phase after 1994; thus, the analysis is performed for two subperiods: 1979–1994 (P1) and 1995–2014 (P2). An ASCETP‐related energy budget analysis shows that the ASCETP variation has a more pronounced cooling effect on the above atmosphere in P1 than in P2. The snow‐related anomalous negative geopotential height above the TP is more pronounced and extends farther northeastward in P1 than in P2. Further analysis shows that the relationship between the ASCETP and NA winter SAT is not steady. During P1, associated with an anomalous positive ASCETP, negative geopotential height anomalies emerge over the northeastern TP. These negative anomalies impose an anomalous vorticity perturbation near the East Asian westerly jet core that propagates eastward, forming a wave train‐like pattern. It crosses the North Pacific Ocean and reaches the NA region, leading to positive and negative winter SAT anomalies over western and eastern NA, respectively. In contrast, during P2, the impact of anomalous ASCETP on the variation in the winter SAT over NA is weak, probably due to the relatively weak local cooling effect of the ASCETP and the weak ASCETP‐related vorticity forcing around the East Asian westerly jet.

On the Interdecadal Change in the Interannual Variation in Autumn Snow Cover Over the Central Eastern Tibetan Plateau in the Mid‐1990s

“…The Tibetan Plateau (TP) has the highest elevation on Earth and presents a large snow cover area in cold seasons (Che et al, 2019; Chu et al, 2017; Pu et al, 2007; Wang et al, 2017; Wang, Wu, et al, 2019). Snow cover anomalies can significantly impact the surface energy budget and hydrological cycle as well as both local and remote climates (e.g., Blanford, 1884; Dey & Kumar, 1983; Ding et al, 2008, 2009; Hahn & Shukla, 1976; Jia et al, 2018; Lin & Wu, 2011, 2012; Liu et al, 2017; Mote & Kutney, 2012; Qian et al, 2019; Walker, 1910; Wang, Wu, et al, 2019; Wu & Kirtman, 2007; Zhao & Moore, 2004; Zwiers, 1993). The snow cover over the TP forms in autumn and can persist to the following winter and spring or even into summer in some high‐altitude regions (e.g., Li et al, 2017; Pu et al, 2007; Wang et al, 2017, 2018).…”

Machine Learning Models for the Seasonal Forecast of Winter Surface Air Temperature in North America

“…As revealed by previous studies (Lin & Wu, 2011, 2012; Qian et al, 2019), autumn TP snow cover can affect the winter SAT over NA via the propagation of a snow‐related Rossby wave train. These previous studies suggest that TP snow cover can be an important climate predictor for NA winter SAT.…”

“…A longer training data set might be helpful for improving the forecasting skill of the XGBoost model. As an extension of previous work (Lin & Wu, 2011;Qian et al, 2019), the sensitivity of empirical model skill to the TP snow predictor is also investigated. It is shown that the additional use of the TP snow predictor can improve the forecast skill of the three empirical models but over different regions of NA.…”

“…In addition to the ocean, sensible heat flux from the land surface may also provide a potential source of predictability for NA climate prediction (e.g., Gong et al, 2002; Gong et al, 2004; Sobolowski et al, 2010). For example, the autumn snow cover on the Tibetan Plateau (TP) has been revealed to affect the winter SAT over NA through thermally forced Rossby wave trains related to snow cover changes (Lin & Wu, 2011; Qian et al, 2019). This suggests that the TP snow cover can also serve as a useful predictor for the seasonal prediction of NA winter SAT and extreme events (e.g., Lin & Wu, 2012).…”

Rapid response of the East Asian trough to Tibetan Plateau snow cover

“…The Tibetan Plateau snow cover (TPSC) and its variations exert substantial influences on the weather, climate and ecosystem of the Tibetan Plateau and its surrounding areas (You et al ., 2020). In most of the literature, TPSC is generally considered as an atmospheric indicator at interannual (e.g., Wu and Qian, 2003; Lin and Wu, 2011; Xiao and Duan, 2016; Wang et al ., 2017; Lyu et al ., 2018; Wang et al ., 2018; Qian et al ., 2019; Qiu et al ., 2019; Yuan et al ., 2019) and decadal time scales (e.g., Zhang et al ., 2004; Zhao and Moore, 2004; Wu et al ., 2012; Si and Ding, 2013); other studies have examined the long‐term trends of TPSC (e.g., Zhao and Moore, 2006; Zhao et al ., 2007).…”