Influence of Eastern Tibetan Plateau Spring Snow Cover on North American Air Temperature and Its Interdecadal Change

2020 ◽  
Vol 33 (12) ◽  
pp. 5123-5139
Author(s):  
Zhibiao Wang ◽  
Renguang Wu ◽  
Anmin Duan ◽  
Xia Qu
Keyword(s):  
North America ◽  
Tibetan Plateau ◽  
Snow Cover ◽  
Atmospheric Circulation ◽  
Air Temperature ◽  
North American ◽  
Eastern Tibetan Plateau ◽  
The North ◽  
The Relationship ◽  
Tibetan Plateau Snow Cover

AbstractPrevious studies revealed the influence of the autumn–winter Tibetan Plateau snow cover on atmospheric circulation and climate in the North American region. The present study documents the relationship between the eastern Tibetan Plateau snow cover and the North American air temperature in spring and the associated physical processes using satellite-based snow cover, reanalysis atmospheric and surface variables, observation-based surface air temperature (SAT), and sea surface temperature (SST). A stable relationship is identified between the eastern Tibetan Plateau snow cover and the North American SAT in spring before the mid-2000s. Positive snow-cover anomalies over the eastern Tibetan Plateau induce cooling in the local atmospheric column. The atmospheric cooling stimulates a large-scale atmospheric wave pattern at the upper level that extends northeastward from the eastern Tibetan Plateau via northeast Asia and the North Pacific to North America. An anomalous high forms over North America, accompanied by anomalous descent. In the northwestern part, the horizontal advection by anomalous southerly winds along the west flank of anomalous anticyclone induces SAT increase. In the central part, the enhanced surface sensible heat flux following anomalous descent-induced downward shortwave radiation increase leads to SAT increase. The relationship between the eastern Tibetan Plateau snow cover and the North American SAT is weakened after the mid-2000s. The weakened relationship is attributed to an intensified impact of tropical central Pacific SST anomalies on the North American SAT variations through a Pacific–North America-like atmospheric circulation pattern, which overcomes the influence of the Tibetan Plateau snow-cover anomalies.

An interdecadal change in the influence of ENSO on the spring Tibetan Plateau snow cover variability in the early 2000s

2021 ◽  
pp. 1
Author(s):  
Zhibiao Wang ◽  
Renguang Wu ◽  
Song Yang ◽  
Mengmeng Lu
Keyword(s):  
Tibetan Plateau ◽  
Snow Cover ◽  
Atmospheric Circulation ◽  
North Atlantic ◽  
Southern Oscillation ◽  
Interdecadal Change ◽  
The Tibetan Plateau ◽  
The Relationship ◽  
Tibetan Plateau Snow Cover ◽  
Sst Anomalies

AbstractEl Niño–Southern Oscillation (ENSO) and the Tibetan Plateau snow cover are important factors in interannual climate variability. The relationship between ENSO and the Tibetan Plateau snow variation is still an issue unresolved. While some studies suggested that ENSO is a key factor of changes in snow cover over the Tibetan Plateau, other studies noted independence between the two. The present study revealed a prominent interdecadal change in the relationship between ENSO and the spring Tibetan Plateau snow cover variation in the early 2000s. There is a significant positive correlation between ENSO and the spring Tibetan Plateau snow cover variation in the period 1988-2003, but an obvious negative relationship is detected in the period 2004-2019. The interdecadal change in the ENSO-snow relationship is related to the distinct pathway of ENSO influence on the spring Tibetan Plateau snow cover variation during the two periods. In the period 1988-2003, ENSO induces anomalous convection over the tropical western North Pacific that in turn cause atmospheric circulation and moisture anomalies over the Tibetan Plateau. The resultant winter snow anomalies over the central-eastern Tibetan Plateau persist to the following spring. In the period 2004-2019, ENSO induces North Atlantic sea surface temperature (SST) anomalies in winter that are maintained to the following spring. The North Atlantic SST anomalies then stimulate the atmospheric circulation anomalies extending to the Tibetan Plateau that induce snow cover anomalies there in spring. The different processes of ENSO influence lead to opposite anomalies of spring snow cover over the Tibetan Plateau in the two periods.

scholarly journals Influence of ENSO on North American subseasonal surface air temperature variability

2021 ◽  
Vol 2 (2) ◽  
pp. 395-412
Author(s):  
Patrick Martineau ◽  
Hisashi Nakamura ◽  
Yu Kosaka
Keyword(s):  
North America ◽  
Air Temperature ◽  
North American ◽  
Surface Air Temperature ◽  
Tropical Pacific ◽  
La Niña ◽  
Western North America ◽  
The North ◽  
Subseasonal Variability ◽  
La Nina

Abstract. The wintertime influence of tropical Pacific sea surface temperature (SST) variability on subseasonal variability is revisited by identifying the dominant mode of covariability between 10–60 d band-pass-filtered surface air temperature (SAT) variability over the North American continent and winter-mean SST over the tropical Pacific. We find that the El Niño–Southern Oscillation (ENSO) explains a dominant fraction of the year-to-year changes in subseasonal SAT variability that are covarying with SST and thus likely more predictable. In agreement with previous studies, we find a tendency for La Niña conditions to enhance the subseasonal SAT variability over western North America. This modulation of subseasonal variability is achieved through interactions between subseasonal eddies and La Niña-related changes in the winter-mean circulation. Specifically, eastward-propagating quasi-stationary eddies over the North Pacific are more efficient in extracting energy from the mean flow through the baroclinic conversion during La Niña. Structural changes of these eddies are crucial to enhance the efficiency of the energy conversion via amplified downgradient heat fluxes that energize subseasonal eddy thermal anomalies. The enhanced likelihood of cold extremes over western North America is associated with both an increased subseasonal SAT variability and the cold winter-mean response to La Niña.

scholarly journals Impact of Autumn-Winter Tibetan Plateau Snow Cover Anomalies on the East Asian Winter Monsoon and Its Interdecadal Change

2021 ◽  
Vol 9 ◽  
Author(s):  
Zhang Chen ◽  
Renguang Wu ◽  
Zhibiao Wang
Keyword(s):  
Tibetan Plateau ◽  
Snow Cover ◽  
Atmospheric Circulation ◽  
East Asian Winter Monsoon ◽  
East Asian ◽  
Winter Monsoon ◽  
Interdecadal Change ◽  
Asian Winter Monsoon ◽  
The North ◽  
Atmospheric Circulation Anomalies

The present study investigates the impacts of autumn-winter Tibetan Plateau (TP) snow cover anomalies on the interannual variability of the East Asian winter monsoon (EAWM). It is found that the northern component of EAWM is significantly associated with October-November-December-January (ONDJ) snow cover anomalies over the eastern TP, whereas the TP snow cover changes have little impact on the southern component of EAWM. However, the relationship of the northern component of EAWM to ONDJ TP snow cover experienced an obvious change in the mid-1990s. During 1979–1998, due to the high persistence of TP snow anomalies from autumn to winter, extensive ONDJ TP snow cover anomalies have a prominent influence on atmospheric circulation over Asia and the North Pacific, with more TP snow cover followed by an enhanced Siberian high and a deepened Aleutian low in winter, resulting in stronger EAWM. During 1999–2016, TP snow cover anomalies have a weak persistence. The atmospheric circulation anomalies display a different distribution. As such, there is a weak connection between the northern component of EAWM and the TP snow cover anomalies during this period.

scholarly journals Combined Influences on North American Winter Air Temperature Variability from North Pacific Blocking and the North Atlantic Oscillation: Subseasonal and Interannual Time Scales

2020 ◽  
Vol 33 (16) ◽  
pp. 7101-7123 ◽  
Author(s):  
Binhe Luo ◽  
Dehai Luo ◽  
Aiguo Dai ◽  
I. Simmonds ◽  
Lixin Wu
Keyword(s):  
North America ◽  
Air Temperature ◽  
North Atlantic ◽  
North American ◽  
North Pacific ◽  
Eastern North America ◽  
The North ◽  
The North Atlantic ◽  
The North Atlantic Oscillation ◽  
The North Pacific

AbstractWinter surface air temperature (SAT) over North America exhibits pronounced variability on subseasonal, interannual, decadal, and interdecadal time scales. Here, reanalysis data from 1950–2017 are analyzed to investigate the atmospheric and surface ocean conditions associated with its subseasonal to interannual variability. Detrended daily SAT data reveal a known warm west/cold east (WWCE) dipole over midlatitude North America and a cold north/warm south (CNWS) dipole over eastern North America. It is found that while the North Pacific blocking (PB) is important for the WWCE and CNWS dipoles, they also depend on the phase of the North Atlantic Oscillation (NAO). When a negative-phase NAO (NAO−) coincides with PB, the WWCE dipole is enhanced (compared with the PB alone case) and it also leads to a warm north/cold south dipole anomaly in eastern North America; but when PB occurs with a positive-phase NAO (NAO+), the WWCE dipole weakens and the CNWS dipole is enhanced. The PB events concurrent with the NAO− (NAO+) and SAT WWCE (CNWS) dipole are favored by the Pacific El Niño–like (La Niña–like) sea surface temperature mode and the positive (negative) North Pacific mode. The PB-NAO+ has a larger component projecting onto the SAT WWCE dipole during the La Niña winter than during the El Niño winter because a more zonal wave train is formed. Strong North American SAT WWCE dipoles and enhanced projections of PB-NAO+ events onto the SAT WWCE dipole component are also readily seen for the positive North Pacific mode. The North Pacific mode seems to play a bigger role in the North American SAT variability than ENSO.

scholarly journals Systematic bias of Tibetan Plateau snow cover in subseasonal-to-seasonal models

2020 ◽  
Author(s):  
Shuzhen Hu ◽  
Wenkai Li
Keyword(s):  
Tibetan Plateau ◽  
Snow Cover ◽  
Air Temperature ◽  
Lead Time ◽  
Surface Air Temperature ◽  
The Tibetan Plateau ◽  
Systematic Bias ◽  
Forecast Lead Time ◽  
Systematic Biases ◽  
Tibetan Plateau Snow Cover

Abstract. Accurate subseasonal-to-seasonal (S2S) atmospheric forecasts and hydrological forecasts have considerable socioeconomic value. This study conducts a multimodel comparison of the Tibetan Plateau snow cover (TPSC) prediction skill using three models (ECMWF, NCEP and CMA) selected from the S2S project database to understand their performance in capturing TPSC variability. S2S models can skilfully forecast TPSC within a lead time of 2 weeks but show limited skill beyond 3 weeks. Compared with the observational snow cover analysis, all three models tend to overestimate the area of TPSC, especially during winter. Another remarkable issue regarding the TPSC forecast is the increasing TPSC with forecast lead time, which further increases the systematic positive biases of TPSC in the S2S models at longer forecast lead times. The underestimation of TPSC dissipation induces an increase in TPSC with forecast lead time in the models. Such systematic biases of TPSC influence the forecasted surface air temperature in the S2S models. The surface air temperature over the Tibetan Plateau becomes colder with increasing forecast lead time in the S2S models.

scholarly journals Systematic bias of Tibetan Plateau snow cover in subseasonal-to-seasonal models

2020 ◽  
Vol 14 (10) ◽  
pp. 3565-3579
Author(s):  
Wenkai Li ◽  
Shuzhen Hu ◽  
Pang-Chi Hsu ◽  
Weidong Guo ◽  
Jiangfeng Wei
Keyword(s):  
Tibetan Plateau ◽  
Snow Cover ◽  
Air Temperature ◽  
Lead Time ◽  
Surface Air Temperature ◽  
Model Integration ◽  
The Tibetan Plateau ◽  
Systematic Bias ◽  
Forecast Lead Time ◽  
Tibetan Plateau Snow Cover

Abstract. Accurate subseasonal-to-seasonal (S2S) atmospheric forecasts and hydrological forecasts have considerable socioeconomic value. This study conducts a multimodel comparison of the Tibetan Plateau snow cover (TPSC) prediction skill using three models (ECMWF, NCEP and CMA) selected from the S2S project database to understand their performance in capturing TPSC variability during wintertime. S2S models can skillfully forecast TPSC within a lead time of 2 weeks but show limited skill beyond 3 weeks. Compared with the observational snow cover analysis, all three models tend to overestimate the area of TPSC. Another remarkable issue regarding the TPSC forecast is the increasing TPSC with forecast lead time, which further increases the systematic positive biases of TPSC in the S2S models at longer forecast lead times. All three S2S models consistently exaggerate the precipitation over the Tibetan Plateau. The exaggeration of precipitation is prominent and always exists throughout the model integration. Systematic bias of TPSC therefore occurs and accumulates with the model integration time. Such systematic biases of TPSC influence the forecasted surface air temperature in the S2S models. The surface air temperature over the Tibetan Plateau becomes colder with increasing forecast lead time in the S2S models. Numerical experiments further confirm the causality.

Different Sources of 10-30-day Intraseasonal Variations of Autumn Snow over Western and Eastern Tibetan Plateau

2020 ◽  
Author(s):  
Lei Song
Keyword(s):  
Tibetan Plateau ◽  
Snow Cover ◽  
Wave Train ◽  
Snow Accumulation ◽  
The Arctic ◽  
Eastern Tibetan Plateau ◽  
The Caspian Sea ◽  
The North ◽  
The North Atlantic Oscillation ◽  
Different Sources

<p>Using the latest daily MODIS satellite snow cover data, the present study reveals distinctly different sources of 10-30-day intraseasonal snow cover variations over the western and eastern Tibetan Plateau (TP) during September-December. The intraseasonal snow variation over the western TP is related to a mid-latitude wave train associated with the Arctic Oscillation and that over the eastern TP is related to a subtropical wave train triggered by the North Atlantic Oscillation. The Rossby wave train in both cases leads to anomalous water vapor convergence and ascending motion, which contributes to snow accumulation and positive snow cover anomalies. For the western TP snow events, the moisture comes from the Caspian Sea. During the eastern TP snow events, the moisture originates from the Bay of Bengal.</p>

scholarly journals Interdecadal Change in the Effect of Tibetan Plateau Snow Cover on Spring Precipitation over Eastern China around the Early 1990s

2021 ◽  
Author(s):  
Chao Zhang ◽  
Yuanyuan Guo ◽  
Zhiping Wen
Keyword(s):  
Tibetan Plateau ◽  
Snow Cover ◽  
Eastern China ◽  
Interdecadal Change ◽  
Phase Pattern ◽  
Spring Precipitation ◽  
Interdecadal Shift ◽  
Additional Support ◽  
The Relationship ◽  
Tibetan Plateau Snow Cover

Abstract Previous works extensively investigated the influences of the winter-spring Tibetan Plateau snow cover (TP, TPSC) on climate variability over the East Asia. The present work documents an interdecadal-changed impacts of different spring TPSC anomaly (TPSCA) patterns on spring precipitation over eastern China (SPEC) around the early 1990s. It is found that the correlation of eastern and western TPSCA shifts from negative to positive around 1990. The empirical orthogonal function (EOF) analysis applying onto the spring TPSCA during 1970–1989 (P1) and during 1991–2017 (P2) adds additional support for such interdecadal change in the relationship between the eastern and western TPSCA. Specifically, the leading EOF (EOF1) mode in P1 shows an out-of-phase pattern with opposite signals lying over the eastern and western TP, while the counterpart in P2 is characterized by an in-phase pattern over the entire TP. Corresponding to more (less) snow cover in the eastern (western) TP in P1, a significant TP cold cyclone (TPCC) and a downstream anticyclone over the western North Pacific are observed. Anomalous southerly flow prevailing east to TPCC could bring the warm-wet air from tropics to the coast of East Asian, which largely enhances the spring precipitation south to Yangtze River Valley (YRV). By contrast, regarding more snow cover both in the eastern and western TP in P2, a relatively northward-displaced and wider TPCC sweeps over the entire TP compared with the TPSC-induced TPCC in P1. Moreover, there are significant sinking anomalies observed in the downstream YRV-HRV region, which leads to suppressed spring precipitation over there via the dry-cold advection process. Hence, these discrepancies of local and downstream atmospheric circulation induced by the out-of-phase and in-phase TPSCA patterns in two epochs play an important role in resulting in the interdecadal shift of the SPEC anomaly pattern around 1990.

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