Intraseasonal Snow Cover Variations Over Western Siberia and Associated Atmospheric Processes

Song, Lei; Wu, Renguang

doi:10.1029/2019jd030479

Cited by 14 publications

(8 citation statements)

References 34 publications

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“…In strong MJO events, positive sea level pressure anomalies are observed over northwestern Siberia in MJO phase 2, accompanied by northerly wind anomalies on the eastern and southern flanks (Figure 4a). This explains the formation of cold anomalies over western Siberia (Figure 3a) as anomalous northerlies bring colder air from the high latitudes (Song and Wu, 2019c). The anticyclonic anomalies over Eurasia move eastward and are enhanced, leading to stronger northerly wind anomalies in MJO phase 3 (Figure 4b).…”

Section: Distinct Circulation Anomalies Of the Strong And Weak Mjo Evmentioning

confidence: 96%

Distinct Eurasian climate anomalies associated with strong and weak MJO events

Song

2020

Intl Journal of Climatology

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The MJO-related tropical Indian Ocean outgoing longwave radiation anomalies display a bimodal distribution, indicating two types of MJO events. The present study distinguishes 14 strong and 16 weak MJO events during the 37 winters from 1979 to 2016 and compares the circulation and climate over the mid-latitude Eurasia between strong and weak MJO events. Cold anomalies appear over Siberia and East Asia during strong MJO events when the MJO-related convection is located over the tropical Indian Ocean, whereas the temperature anomalies are weak over Eurasia during weak MJO events. The cold anomalies over Eurasia in strong MJO events are associated with the development of surface anticyclonic anomalies and the accompanying northerly wind anomalies. On one hand, the enhancement of surface anticyclonic anomalies can be attributed to the poleward Rossby wave packets triggered by the MJO convection over the tropical Indian Ocean. On the other hand, the strong convective heating over the tropical Indian Ocean can induce anomalous meridional overturning circulation between the tropics and mid-latitudes. The anomalous divergent winds associated with the convective heating can reach western Siberia and the descending branch of the vertical cell contributes to the enhancement of surface anticyclonic anomalies and northerly wind anomalies, leading to cold anomalies over Siberia and East Asia. In weak MJO events, the poleward Rossby waves are weak and anomalous meridional overturning is of limited meridional extent. As a result, the MJO-related wind anomalies are weak and the associated temperature anomalies are small over large areas of Eurasia.

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Section: Distinct Circulation Anomalies Of the Strong And Weak Mjo Evmentioning

confidence: 96%

Distinct Eurasian climate anomalies associated with strong and weak MJO events

Song

2020

Intl Journal of Climatology

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“…On the hemispheric scale, snow cover changes slowly with a period longer than a season. However, snow cover can vary rapidly within a season over discontinuous or sporadic permafrost zones (Wang et al ., ; Li et al ., ; Suriano and Leathers, ; Song et al ., ; Song and Wu, ). Understanding the rapid variations in snow cover is important for short‐ and medium‐range weather forecasting applications (Clark and Serreze, ; Li et al ., 2018; Zhang et al ., ).…”

Section: Introductionmentioning

confidence: 98%

Intraseasonal variability of Tibetan Plateau snow cover

Qiu

Guo

et al. 2019

Intl Journal of Climatology

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Using the daily snow cover data at 24‐km resolution from the Interactive Multi‐sensor Snow and Ice Mapping System snow cover analysis, this study describes the variability in Tibetan Plateau (TP) snow cover (TPSC) at multiple time scales with a focus on the intraseasonal time scale (10–90 days). TPSC demonstrates variability over a wide range of temporal scales, but the annual cycle is generally dominant. Synoptic‐scale variability, seasonal variability and interannual and long‐term changes make small contributions to the total daily variability in TPSC. Intraseasonal variability (ISV) is dominant over most of the central and eastern TP and explains 22–40% of the total variability and leads to obvious variations in TPSC over periods shorter than a season. The ISV of TPSC is more active in the cold season than in the warm season. Specifically, the ISV over the Changtang Plateau explains approximately 50% of the total variability of snow cover in the cold season and is even more dominant than the annual cycle. Possible influences of regional atmospheric circulations on TPSC are also examined. TPSC variability is highly correlated with regional surface air temperature (SAT) and precipitation at an intraseasonal time scale. TPSC and SAT tend to have a simultaneous relationship, while anomalous precipitation leads to subsequent TPSC variations with a lag of approximately 5 days and a positive relationship. Such relationships are the result of intraseasonal variations in regional atmospheric circulation. The anomalous adiabatic heating induced by vertical ascending motion leads to tropospheric temperature variations. Furthermore, the horizontal advection of moisture and apparent moisture sink, which are induced by anomalous moisture supply and snow evaporation anomalies, respectively, lead to anomalous moisture associated with changes in the TPSC.

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“…Causes for the non-stationarity are still discussed, with possible influences from the Quasi-Biennial Oscillation (QBO), El Niño-Southern Oscillation (ENSO) or simply snow cover vari-ance (Peings et al, 2017;O'Reilly et al, 2017;Tyrrell et al, 2018;Wegmann et al, 2020;Weisheimer et al, 2020). Disentangling co-variability is further challenged by the co-occurrence of increased Eurasian snow cover and increased Ural blocking frequency, questioning the lead-lag relationship between snow cover and blocking (Peings, 2019;Kretschmer et al, 2018;Song and Wu, 2019;Santolaria-Otín et al, 2021). Moreover, a variety of temporal and spatial snow cover indices used among the different studies obstruct direct comparisons.…”

Section: Introductionmentioning

confidence: 99%

Impact of Eurasian autumn snow on the winter North Atlantic Oscillation in seasonal forecasts of the 20th century

Wegmann

Orsolini

Weisheimer

et al. 2021

Weather Clim. Dynam.

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Abstract. As the leading climate mode of wintertime climate variability over Europe, the North Atlantic Oscillation (NAO) has been extensively studied over the last decades. Recently, studies highlighted the state of the Eurasian cryosphere as a possible predictor for the wintertime NAO. However, missing correlation between snow cover and wintertime NAO in climate model experiments and strong non-stationarity of this link in reanalysis data are questioning the causality of this relationship. Here we use the large ensemble of Atmospheric Seasonal Forecasts of the 20th Century (ASF-20C) with the European Centre for Medium-Range Weather Forecasts model, focusing on the winter season. Besides the main 110-year ensemble of 51 members, we investigate a second, perturbed ensemble of 21 members where initial (November) land conditions over the Northern Hemisphere are swapped from neighboring years. The Eurasian snow–NAO linkage is examined in terms of a longitudinal snow depth dipole across Eurasia. Subsampling the perturbed forecast ensemble and contrasting members with high and low initial snow dipole conditions, we found that their composite difference indicates more negative NAO states in the following winter (DJF) after positive west-to-east snow depth gradients at the beginning of November. Surface and atmospheric forecast anomalies through the troposphere and stratosphere associated with the anomalous positive snow dipole consist of colder early winter surface temperatures over eastern Eurasia, an enhanced Ural ridge and increased vertical energy fluxes into the stratosphere, with a subsequent negative NAO-like signature in the troposphere. We thus confirm the existence of a causal connection between autumn snow patterns and subsequent winter circulation in the ASF-20C forecasting system.

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Intraseasonal Snow Cover Variations Over Western Siberia and Associated Atmospheric Processes

Cited by 14 publications

References 34 publications

Distinct Eurasian climate anomalies associated with strong and weak MJO events

Distinct Eurasian climate anomalies associated with strong and weak MJO events

Intraseasonal variability of Tibetan Plateau snow cover

Impact of Eurasian autumn snow on the winter North Atlantic Oscillation in seasonal forecasts of the 20th century

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