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

2019 ◽  
Vol 46 (23) ◽  
pp. 14145-14152
Author(s):  
Remco J. Kok ◽  
Walter W. Immerzeel
Keyword(s):  
Surface Temperature ◽  
Near Surface ◽  
Temperature Variations ◽  
Emergent Feature

The Western Tibetan Vortex as an emergent feature of near-surface temperature variations

2020 ◽  
Author(s):  
Remco de Kok ◽  
Walter Immerzeel
Keyword(s):  
Surface Temperature ◽  
20Th Century ◽  
Large Scale ◽  
High Mountain ◽  
Net Radiation ◽  
Near Surface ◽  
Temperature Variations ◽  
Surface Temperatures ◽  
Emergent Feature ◽  
Main Driver

<p>Glaciers are growing in a part of High Mountain Asia (HMA), contrary to the demise of glaciers worldwide. A proposed explanation for this behaviour is the decreasing strength of the "Western Tibetan Vortex" (WTV), a circular motion of air in the troposphere around northwestern High Mountain Asia, 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 20th 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 mid-latitude regions as well.</p>

scholarly journals Observed Multi-Timescale Differences between Summertime Near-Surface Equivalent Temperature and Temperature for China and Their Linkage with Global Sea Surface Temperatures

Atmosphere ◽  
2019 ◽  
Vol 10 (8) ◽  
pp. 447
Author(s):  
Jingping Li ◽  
Xiao Li ◽  
Xing Li ◽  
Lian Chen ◽  
Likun Jin
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Spatial Patterns ◽  
Southern Oscillation ◽  
Linear Trend ◽  
Sea Surface ◽  
Multiple Time ◽  
Equivalent Temperature ◽  
Near Surface ◽  
Temperature Variations

Based on the ensemble empirical mode decomposition method, this study explores the differences and similarities in multiple time-scale characteristics of summer air temperature (T) and equivalent temperature (Te) over China during 1961–2017, using daily meteorological observations collected at 412 stations in China. Their relationships to global sea surface temperature variations is also discussed. Results show that both T and Te can be decomposed into five components, which includes multiple timescales, from interannual to long-term trends. The spatial patterns of each timescale’s leading mode show that the variations of Te are generally larger than that of T. Meanwhile, both T and Te are dominated by their inter-annual, multi-decadal variations and the non-linear trend. High correlations of T and Te can also be found in these major scales. The related sea surface temperature variations in these major scales also show consistent patterns, which correspond to El Niño–Southern Oscillation, Atlantic Multidecadal Oscillation and the global warming trend in the sea, respectively. In other scales, both spatial patterns of T and Te and the corresponding correlation patterns with sea surface temperature are distinguishable. The current results explore the compound changes of surface temperature-humidity during the past five decades from a new perspective, which provides some insights for a better understanding of the possible causes of climate change over China.

Physics of Changes in Synoptic Midlatitude Temperature Variability

2015 ◽  
Vol 28 (6) ◽  
pp. 2312-2331 ◽  
Author(s):  
Tapio Schneider ◽  
Tobias Bischoff ◽  
Hanna Płotka
Keyword(s):  
Global Warming ◽  
Surface Temperature ◽  
Northern Hemisphere ◽  
Potential Temperature ◽  
Temperature Variability ◽  
Temperature Gradients ◽  
Arctic Amplification ◽  
Near Surface ◽  
Temperature Variations ◽  
Temperature Variance

Abstract This paper examines the physical processes controlling how synoptic midlatitude temperature variability near the surface changes with climate. Because synoptic temperature variability is primarily generated by advection, it can be related to mean potential temperature gradients and mixing lengths near the surface. Scaling arguments show that the reduction of meridional potential temperature gradients that accompanies polar amplification of global warming leads to a reduction of the synoptic temperature variance near the surface. This is confirmed in simulations of a wide range of climates with an idealized GCM. In comprehensive climate simulations (CMIP5), Arctic amplification of global warming similarly entails a large-scale reduction of the near-surface temperature variance in Northern Hemisphere midlatitudes, especially in winter. The probability density functions of synoptic near-surface temperature variations in midlatitudes are statistically indistinguishable from Gaussian, both in reanalysis data and in a range of climates simulated with idealized and comprehensive GCMs. This indicates that changes in mean values and variances suffice to account for changes even in extreme synoptic temperature variations. Taken together, the results indicate that Arctic amplification of global warming leads to even less frequent cold outbreaks in Northern Hemisphere winter than a shift toward a warmer mean climate implies by itself.

scholarly journals Estimation of the terms acting on local 1 h surface temperature variations in Paris region: the specific contribution of clouds

2021 ◽  
Vol 21 (20) ◽  
pp. 15699-15723
Author(s):  
Oscar Javier Rojas Muñoz ◽  
Marjolaine Chiriaco ◽  
Sophie Bastin ◽  
Justine Ringard
Keyword(s):  
Heat Exchange ◽  
Surface Temperature ◽  
Radiative Forcing ◽  
Small Scale ◽  
Radiative Effect ◽  
Near Surface ◽  
Temperature Variations ◽  
Clear Sky ◽  
Hourly Temperature ◽  
Specific Contribution

Abstract. Local short-term temperature variations at the surface are mainly dominated by small-scale processes coupled through the surface energy balance terms, which are well known but whose specific contribution and importance on the hourly scale still need to be further analyzed. A method to determine each of these terms based almost exclusively on observations is presented in this paper, with the main objective being to estimate their importance in hourly near-surface temperature variations at the SIRTA observatory, near Paris. Almost all terms are estimated from the multi-year dataset SIRTA-ReOBS, following a few parametrizations. The four main terms acting on temperature variations are radiative forcing (separated into clear-sky and cloudy-sky radiation), atmospheric heat exchange, ground heat exchange, and advection. Compared to direct measurements of hourly temperature variations, it is shown that the sum of the four terms gives a good estimate of the hourly temperature variations, allowing a better assessment of the contribution of each term to the variation, with an accurate diurnal and annual cycle representation, especially for the radiative terms. A random forest analysis shows that whatever the season, clouds are the main modulator of the clear-sky radiation for 1 h temperature variations during the day and mainly drive these 1 h temperature variations during the night. Then, the specific role of clouds is analyzed exclusively in cloudy conditions considering the behavior of some classical meteorological variables along with lidar profiles. Cloud radiative effect in shortwave and longwave and lidar profiles show a consistent seasonality during the daytime, with a dominance of mid- and high-level clouds detected at the SIRTA observatory, which also affects near-surface temperatures and upward sensible heat flux. During the nighttime, despite cloudy conditions and having a strong cloud longwave radiative effect, temperatures are the lowest and are therefore mostly controlled by larger-scale processes at this time.

Holocene sea surface temperature variations recorded in corals from Kikai Island, Japan

2017 ◽  
Vol 51 (4) ◽  
pp. e9-e14 ◽  
Author(s):  
Hiroto Kajita ◽  
Atsuko Yamazaki ◽  
Takaaki Watanabe ◽  
Chung-Che Wu ◽  
Chuan-Chou Shen ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Sea Surface ◽  
Temperature Variations
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