The Karakoram/Western Tibetan vortex: seasonal and year-to-year variability

Li, Xiaofeng; Fowler, Hayley J.; Forsythe, Nathan; Blenkinsop, Stephen; Pritchard, David

doi:10.1007/s00382-018-4118-2

Cited by 34 publications

(43 citation statements)

References 51 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…By day 0, the cold anomalies had started to invade the atmosphere above the SETP (Figure g). Together with the cyclonic anomaly over the TP on day 0, these cold anomalies are consistent with the “warm high/cold low” temperature‐circulation relationship over the Karakoram‐West TP previously identified by Forsythe et al () and Li et al (). Their findings regarding this temperature–circulation relationship can therefore be applied to nearly the entire TP.…”

Section: Thermodynamic Conditions Necessary For Wintertime Extreme Prsupporting

confidence: 89%

“…By contrast, the vertical advection and the diabatic heating played roles in inhibiting the rapid temperature drop. As pointed out by Forsythe et al (2017) and Li et al (2018), the large cold anomalies associated with the cyclonic anomaly (i.e., the cold low) over the Karakoram-West TP were mainly generated by the adiabatic cooling due to the powerful upward motion. Thus, the heat budget analysis here indicates that their finding about the dominant role of the adiabatic cooling in the formation of cold anomalies in the cyclonic anomaly can be applied to nearly the whole TP region.…”

Section: Heat Budget Analysis Of the Temperature Variationmentioning

confidence: 85%

See 1 more Smart Citation

On the Formation Mechanism for Wintertime Extreme Precipitation Events Over the Southeastern Tibetan Plateau

et al. 2018

View full text Add to dashboard Cite

The formation mechanism for wintertime extreme precipitation events over the southeastern Tibetan Plateau (SETP) is explored. The crucial step in the development of these events was the emergence of a cyclonic anomaly above the Tibetan Plateau. Wave activity fluxes along a Rossby wave train embedded in the subtropical jet stream (i.e., the circumglobal teleconnection) played the dominant role in producing this cyclonic anomaly, supported by weaker wave activity fluxes along a second Rossby wave train originating over Scandinavia. The cyclonic anomaly then moved over the SETP, favored strong updrafts, large‐scale moisture convergence, and intense precipitation. Extreme precipitation was more likely to ensue when the arrival of the cyclonic anomaly was preceded by persistent warm anomalies over the SETP, which favored moisture accumulation there. Temperatures above the SETP dropped sharply around the onset of the extreme precipitation. A heat budget analysis indicates that adiabatic cooling associated with convective ascent along the downstream edge of the cyclone played a leading role in this temperature drop, while a cold air intrusion associated with an anticyclonic anomaly over western Siberia (one center of action along the second wave train) played a complementary role. An Eulerian moisture budget analysis shows that variations in precipitable water delayed the onset and enhanced the intensity of these events, with moisture for precipitation delivered to the SETP mainly through the western and southern boundaries. A companion Lagrangian moisture source analysis reveals that the land areas south of the Tibetan Plateau typically contributed 78.7% of the moisture supply for these events.

show abstract

Section: Thermodynamic Conditions Necessary For Wintertime Extreme Prsupporting

confidence: 89%

Section: Heat Budget Analysis Of the Temperature Variationmentioning

confidence: 85%

On the Formation Mechanism for Wintertime Extreme Precipitation Events Over the Southeastern Tibetan Plateau

et al. 2018

View full text Add to dashboard Cite

show abstract

“…Both orographic and convective uplift favor the occurrence of precipitation over the southern TP (Tucker, ). In addition to these two lifting processes, further study has revealed that cyclonic systems moving along the subtropical westerly jet stream play an important role in triggering wintertime intense precipitation over the TP by strengthening large‐scale moisture convergence and updrafts (Cannon et al, , , ; Dimri et al, ; Forsythe et al, ; Lang & Barros, ; Li et al, ).…”

Section: Introductionmentioning

confidence: 99%

Moisture Sources for Wintertime Intense Precipitation Events Over the Three Snowy Subregions of the Tibetan Plateau

et al. 2019

View full text Add to dashboard Cite

Wintertime intense precipitation events often lead to severe snow disasters. In this study, a Lagrangian approach is employed to examine the evaporative moisture sources for wintertime intense precipitation events over the three snowy subregions of the Tibetan Plateau (TP) during 1979–2016, including the western TP (WTP), south central TP (SCTP), and southeastern TP (SETP). More than 80.0% of the moisture for intense precipitation over each subregion originates from terrestrial areas. Although prevailing westerly winds dominate above the TP and its surrounding areas during winter, half of the precipitation over the three subregions is supplied by evaporation from the south (i.e., the Indian Peninsula). Specifically, evaporation from the Indian Peninsula contributes 68.0%, 65.0%, and 45.0% of the moisture for intense precipitation over the WTP, SCTP, and SETP, respectively. The two primary oceanic moisture source regions for intense precipitation are the Arabian Sea and the Bay of Bengal, playing complementary roles in supplying moisture. The relative contributions of the Arabian Sea to intense precipitation over the WTP, SCTP, and SETP are 9.2%, 6.9%, and 1.1%, while those of the Bay of Bengal are 1.1%, 12.1%, and 8.6%. Southerly winds downstream of a cyclonic anomaly over the Indian Peninsula are crucial for the low‐level moisture transport from the south to the Himalayan foothills. Under the combined effects of orographic lifting and favorable large‐scale circulation patterns, moisture ascends further into the three subregions. Changes in the position and intensity of the cyclonic anomaly are particularly crucial to facilitating moisture contributions from the key source regions.

show abstract

“…However, the region of correlated near-surface temperatures associated with the WTV also includes regions that experience rapid decline of glaciers, such as Spiti Lahaul (Brun et al, 2017). Precipitation associated with the WTV might shed more light on this issue (Li et al, 2018), but the WTV might not be the main dynamical response to changes in precipitation, as it is for changes in temperature (Acosta & Huber, 2017;Cannon et al, 2015;Cash et al, 2015). Precipitation associated with the WTV might shed more light on this issue (Li et al, 2018), but the WTV might not be the main dynamical response to changes in precipitation, as it is for changes in temperature (Acosta & Huber, 2017;Cannon et al, 2015;Cash et al, 2015).…”

Section: Resultsmentioning

confidence: 99%

“…Another suggestion was put forward by Forsythe et al (2017), who found that temperatures in northwestern HMA highly correlate with the circulation around northwestern HMA at pressures between 500 and 200 hPa. This structure of correlated atmospheric variables was dubbed the "Karakoram Vortex," or "Western Tibetan Vortex" (WTV) by Forsythe et al (2017) and following work by Li et al (2018Li et al ( , 2019, together referred to as FL17-19 here. They propose that adiabatic heating and cooling, caused by the vortex, is the driver of temperature changes in northwestern HMA.…”

Section: Introductionmentioning

confidence: 99%

The Western Tibetan Vortex as an Emergent Feature of Near‐Surface Temperature Variations

Kok

Immerzeel

2019

Geophysical Research Letters

View full text Add to dashboard Cite

Glaciers around the world are shrinking, yet in a region in northwestern High Mountain Asia (HMA), glaciers show growth. A proposed explanation for this anomalous behavior is related to the variability of the "Western Tibetan Vortex" (WTV), which correlates well with near-surface temperatures in northwestern HMA. Using analytical formulations and ERA5 reanalysis data, we show that the WTV is the change of wind field resulting from changes in near-surface temperature gradients in geostrophic flow and that it is not unique to northwestern HMA. Instead, we argue that net radiation is likely the main driver of near-surface temperatures in Western HMA in summer and autumn. The decreasing strength of the WTV during summer in the twentieth century is thus likely the result of decreasing net radiation. We do argue that the WTV is a useful concept that could yield insights in other regions as well.Plain Language Summary Glaciers are growing in a part of High Mountain Asia (HMA), contrary to the demise of glaciers worldwide. A proposed explanation for this behavior is the decreasing strength of the "Western Tibetan Vortex" (WTV), a circular motion of air in the troposphere around northwestern HMA, which is proposed to drive near-surface temperatures. Here, we show that the WTV is the change of wind field resulting from changes in near-surface temperature, and that it is not unique to northwestern HMA, but is generally applicable to large parts of the globe. Instead, we argue that net radiation is likely the main driver of near-surface temperatures in Western HMA in summer and autumn and that the WTV is the response of the atmosphere to changes in temperature. The decreasing strength of the WTV, as seen during summer in the twentieth century, is thus likely the result of changing net radiation and not the main driver of cooling itself. We do argue that the WTV is a useful concept to understand large-scale climate variability in the region and that such an approach could yield important insights in other midlatitude regions as well.

show abstract

The Karakoram/Western Tibetan vortex: seasonal and year-to-year variability

Cited by 34 publications

References 51 publications

On the Formation Mechanism for Wintertime Extreme Precipitation Events Over the Southeastern Tibetan Plateau

On the Formation Mechanism for Wintertime Extreme Precipitation Events Over the Southeastern Tibetan Plateau

Moisture Sources for Wintertime Intense Precipitation Events Over the Three Snowy Subregions of the Tibetan Plateau

The Western Tibetan Vortex as an Emergent Feature of Near‐Surface Temperature Variations

Contact Info

Product

Resources

About