scholarly journals Skillful prediction of summer rainfall in the Tibetan Plateau on multiyear time scales

2021 ◽  
Vol 7 (24) ◽  
pp. eabf9395
Author(s):  
Shuai Hu ◽  
Tianjun Zhou
Keyword(s):  
Tibetan Plateau ◽  
Time Scales ◽  
North Atlantic ◽  
Prediction Models ◽  
Summer Rainfall ◽  
The Tibetan Plateau ◽  
Silk Road Pattern ◽  
Near Term ◽  
Asian Water ◽  
The Silk Road

Skillful near-term climate predictions of rainfall over the Tibetan Plateau (TP), the Asian water tower, benefit billions of people. On the basis of the state-of-the-art decadal prediction models, we showed evidence that although the raw model outputs show low predicted ability for the summer Inner TP (ITP) rainfall due to low signal-to-noise ratios in models, we can produce realistic predictions by extracting the predictable signal from large ensemble predictions along with a postprocessing procedure of variance adjustment. The results indicate that the summer ITP rainfall is highly predictable on multiyear time scales. The predictability of ITP rainfall originates from the Silk Road pattern driven by sea surface temperature over the subpolar gyre region in North Atlantic. Real-time forecasts suggest that the ITP will become wetter, with 12.8% increase in rainfall during 2020–2027 relative to 1986–2005. Our results will help the water resources management in the surrounding regions.

scholarly journals A Mechanism for the Recently Increased Interdecadal Variability of the Silk Road Pattern

2019 ◽  
Vol 32 (3) ◽  
pp. 717-736 ◽  
Author(s):  
Claudia Christine Stephan ◽  
Nicholas P. Klingaman ◽  
Andrew G. Turner
Keyword(s):  
South Asia ◽  
Time Scales ◽  
Prediction Models ◽  
Decadal Variability ◽  
Causal Effect ◽  
Vertical Motion ◽  
Silk Road ◽  
The North ◽  
Silk Road Pattern ◽  
The Silk Road

The Silk Road pattern (SRP) teleconnection manifests in summer over Eurasia, where it is associated with substantial temperature and precipitation anomalies. The SRP varies on interannual and decadal scales; reanalyses show an increase in its decadal variability around the mid-1970s. Understanding what drives this decadal variability is particularly important, because contemporary seasonal prediction models struggle to predict the phase of the SRP. Based on analysis of observations and multiple targeted numerical experiments, this study proposes a mechanism for decadal SRP variability. Causal effect network analysis confirms a positive feedback loop between the eastern portion of the SRP pattern and vertical motion over India on synoptic time scales. Anomalies over a larger region of subtropical South Asia can reinforce a background state that projects onto the positive or negative SRP through this mechanism. This effect is isolated and confirmed in targeted numerical simulations. The transition from weak to strong decadal variability in the mid-1970s is consistent with more spatially coherent interannual precipitation variability over subtropical South Asia. Furthermore, results suggest that oceanic variability does not directly force the SRP. Nevertheless, sea surface temperatures in the North Atlantic and the North Pacific may indirectly affect the SRP by modulating South Asian rainfall on decadal time scales.

scholarly journals Impact of Solar Activity on Snow Cover Variation Over the Tibetan Plateau and Linkage to the Summer Precipitation in China

2022 ◽  
Vol 9 ◽  
Author(s):  
Yan Song ◽  
Zhicai Li ◽  
Yu Gu ◽  
Ziniu Xiao
Keyword(s):  
Solar Activity ◽  
Tibetan Plateau ◽  
Snow Cover ◽  
Time Scales ◽  
Southern Oscillation ◽  
Summer Precipitation ◽  
Summer Rainfall ◽  
High Solar Activity ◽  
The Tibetan Plateau ◽  
The Impact

Solar activity is one of the main external forcing factors driving the Earth’s climate system to change. The snow cover over the Tibetan Plateau is an important physical factor affecting the East Asian climate. At present, insufficient research on the connection between solar activity and snow cover over the Tibetan Plateau has been carried out. Using Solar Radio Flux (SRF), Solar Sunspot Number (SSN), and Total Solar Irradiance (TSI) data, this paper calculated the correlation coefficients with snow indices over the Tibetan Plateau, such as winter and spring snow depth (WSD/SSD) and snow day number (WSDN/SSDN). These snow indices are obtained from the daily gauge snow data in the Tibetan Plateau. Through correlation analyses, it is found that there are significant synchronous or lag correlations between snow indices and solar parameters on multi-time scales. In particular, the Spring Snow Day Number (SSDN) is of significant synchronous or lag correlation with SRF, SSN, and TSI on multi-time scales. It is further found that SSDN over the Tibetan Plateau has more stable positive correlations with SRF by using the 21-year running mean and cross spectrum analyses. Therefore, SSDN can be ascertained to be the most sensitive snow index to the solar activity compared with other snow indices. Moreover, its influence on summer precipitation of China is strongly regulated by solar activity. In high solar activity years (HSAY), the significant correlated area of summer precipitation in China to SSDN is located further north than that in low solar activity years (LSAY). Such impact by solar activity is also remarkable after excluding the impact of ENSO (i.e., El Niño–Southern Oscillation) events. These results provide support for the application of snow indices in summer rainfall prediction in China.

scholarly journals How Predictable Are the Arctic and North Atlantic Oscillations? Exploring the Variability and Predictability of the Northern Hemisphere

2018 ◽  
Vol 31 (3) ◽  
pp. 997-1014 ◽  
Author(s):  
Daniela I. V. Domeisen ◽  
Gualtiero Badin ◽  
Inga M. Koszalka
Keyword(s):  
Time Scales ◽  
Northern Hemisphere ◽  
North Atlantic ◽  
Prediction Models ◽  
The Arctic ◽  
Ensemble Prediction ◽  
Atmospheric Conditions ◽  
Short Term ◽  
The North ◽  
The North Atlantic Oscillation

ABSTRACT The North Atlantic Oscillation (NAO) and the Arctic Oscillation (AO) describe the dominant part of the variability in the Northern Hemisphere extratropical troposphere. Because of the strong connection of these patterns with surface climate, recent years have shown an increased interest and an increasing skill in forecasting them. However, it is unclear what the intrinsic limits of short-term predictability for the NAO and AO patterns are. This study compares the variability and predictability of both patterns, using a range of data and index computation methods for the daily NAO and AO indices. Small deviations from Gaussianity are found along with characteristic decorrelation time scales of around one week. In the analysis of the Lyapunov spectrum it is found that predictability is not significantly different between the AO and NAO or between reanalysis products. Differences exist, however, between the indices based on EOF analysis, which exhibit predictability time scales around 12–16 days, and the station-based indices, exhibiting a longer predictability of 18–20 days. Both of these time scales indicate predictability beyond that currently obtained in ensemble prediction models for short-term predictability. Additional longer-term predictability for these patterns may be gained through local feedbacks and remote forcing mechanisms for particular atmospheric conditions.

scholarly journals Assessing the Performance of CMIP5 Global Climate Models for Simulating Future Precipitation Change in the Tibetan Plateau

Water ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1771 ◽  
Author(s):  
Kun Jia ◽  
Yunfeng Ruan ◽  
Yanzhao Yang ◽  
Chao Zhang
Keyword(s):  
Tibetan Plateau ◽  
Climate Models ◽  
Global Climate ◽  
Precipitation Change ◽  
Multiple Criteria ◽  
Global Climate Models ◽  
The Tibetan Plateau ◽  
Spatial Distributions ◽  
Near Term ◽  
Far Future

In this study, the performance of 33 Coupled Model Intercomparison Project 5 (CMIP5) global climate models (GCMs) in simulating precipitation over the Tibetan Plateau (TP) was assessed using data from 1961 to 2005 by an improved score-based method, which adopts multiple criteria to achieve a comprehensive evaluation. The future precipitation change was also estimated based on the Delta method by selecting the submultiple model ensemble (SMME) in the near-term (2006–2050) and far future (2051–2095) periods under Representative Concentration Pathways (RCP) scenarios RCP4.5 and RCP8.5. The results showed that most GCMs can reasonably simulate the precipitation pattern of an annual cycle; however, all GCMs overestimated the precipitation over TP, especially in spring and summer. The GCMs generally provide good simulations of the temporal characteristics of precipitation, while they did not perform as well in reproducing its spatial distributions. Different assessment criteria lead to inconsistent results; however, the improved rank score method, which adopts multiple criteria, provided a robust assessment of GCMs performance. The future annual precipitation was projected to increase by ~6% in the near-term with respect to the period 1961–2005, whereas increases of 12.3% and 16.7% are expected in the far future under RCP4.5 and RCP8.5 scenarios, respectively. Similar spatial distributions of future precipitation changes can be seen in the near-term and far future periods under the two scenarios, and indicate that the most predominant increases occurred in the north of TP. The results of this study are expected to provide valuable information on climate change, and for water resources and agricultural management in TP.

Why Is There an Early Spring Cooling Shift Downstream of the Tibetan Plateau?

2005 ◽  
Vol 18 (22) ◽  
pp. 4660-4668 ◽  
Author(s):  
Jian Li ◽  
Rucong Yu ◽  
Tianjun Zhou ◽  
Bin Wang
Keyword(s):  
Tibetan Plateau ◽  
North Africa ◽  
North Atlantic ◽  
Radiative Forcing ◽  
Temperature Shift ◽  
Early Spring ◽  
Climate Feedback ◽  
The Tibetan Plateau ◽  
The North ◽  
The North Atlantic

Abstract The temperature shift over the eastern flank of the Tibetan Plateau is examined using the last 50 yr of Chinese surface station observations. It was found that a strong cooling shift occurs in early spring (March and April) and late summer (July, August, and September) in contrast to the warming shift in other seasons. The cause of the March–April (MA) cooling is investigated in this study. The MA cooling shift on the lee side of the Tibetan Plateau is found to be not a local phenomenon, but rather it is associated with an eastward extension of a cooling signal originating from North Africa that is related to the North Atlantic Oscillation (NAO) in the previous winter. The midtropospheric westerlies over the North Atlantic and North Africa tend to intensify during positive NAO phases. The enhanced westerlies, after passing over the Tibetan Plateau, result in strengthened ascending motion against the lee side of the plateau, which favors the formation of midlevel stratiform clouds. The increased amount of stratus clouds induces a negative net cloud–radiative forcing, which thereby cools the surface air and triggers a positive cloud–temperature feedback. In this way, the cooling signal from the upstream could “jump” over the Tibetan Plateau and leave a footprint on its lee side. The continental stratiform cloud–climate feedback plays a significant role in the amplification of the cooling shift downstream of the Tibetan Plateau.

Potential Predictability of the Silk Road Pattern and the Role of SST as Inferred from Seasonal Hindcast Experiments of a Coupled Climate Model

2020 ◽  
Vol 33 (22) ◽  
pp. 9567-9580
Author(s):  
Ronald Kwan Kit Li ◽  
Chi Yung Tam ◽  
Ngar Cheung Lau ◽  
Soo Jin Sohn ◽  
Joong Bae Ahn
Keyword(s):  
North Atlantic ◽  
Silk Road ◽  
Potential Predictability ◽  
The North ◽  
Silk Road Pattern ◽  
The North Atlantic ◽  
Upper Level ◽  
The Silk Road ◽  
Wind Bias

AbstractThe Silk Road pattern (SR) is a leading mode of atmospheric circulation over midlatitude Eurasia in boreal summer. Its temporal phase is known to be unpredictable in many models. Previous studies have not reached a clear consensus on the role of sea surface temperature (SST) associated with SR. By comparing seasonal hindcasts from the Pusan National University (PNU) coupled general circulation model with reanalysis, we investigate if there are any sources of predictability originating from the SST. It was found that the PNU model cannot predict SR temporally. In fact, SR is associated with El Niño–Southern Oscillation (ENSO) in the model hindcasts, in contrast to reanalysis results in which SR is more associated with North Atlantic SST anomalies. The PNU system, however, shows potential predictability in SR associated with tropical Pacific SST. Bias in stationary Rossby waveguides is proposed as an explanation for the SR–ENSO relationship in hindcast runs. Model upper-level wind bias in the North Atlantic results in a less continuous waveguide connecting the North Atlantic to Asia, and may hinder wave propagations induced by North Atlantic SST to trigger SR. On the other hand, model upper-level wind bias in the subtropical western Pacific may favor westward propagation of zonally elongated waves from the ENSO region to trigger SR. This study implies that the role of SST with regard to SR can be substantially changed depending on the fidelity of model upper-level background winds.

scholarly journals Influence of Tibetan Plateau On The North American Summer Monsoon Precipitation

2021 ◽  
Author(s):  
Qin Wen ◽  
Zixuan Han ◽  
Hajun Yang ◽  
Jianbo Cheng ◽  
Zhengyu Liu ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Summer Monsoon ◽  
North Atlantic ◽  
North American ◽  
Wave Train ◽  
Meridional Overturning Circulation ◽  
Hadley Cell ◽  
Dynamical Process ◽  
The Tibetan Plateau ◽  
The North

Abstract It has been well known that the uplift of the Tibetan Plateau (TP) can significantly enhance the Asian monsoon. Here, by comparing the sensitivity experiments with vs without the TP, we find that TP uplift can also increase the precipitation of North American Summer Monsoon (NASM), with atmosphere teleconnection accounting for 6% and oceanic dynamical process accounting for another 6%. Physically, TP uplift generates a stationary Rossby wave train traveling from Asian continent to the North Atlantic region, resulting in an anomalous high-pressure over tropical-subtropical North Atlantic. The anomalous subtropical high enhances the low level southerly winds, forcing an anomalous upward motion over North American monsoon (NAM) region and then an increased summer precipitation there. In addition, TP uplift enhances the Atlantic meridional overturning circulation, which reduces the meridional temperature gradient and leads to a northward shift of Hadley Cell over eastern Pacific-Atlantic section. The latter shifts the convection center northward to 10°N and further increases the NASM precipitation. The enhanced NASM precipitation can also be understood by the northward shift of Intertropical Convergence Zone. Our study implies that the changes of NAM climate can be affected by not only local process but also remote forcing, including the Asian highland.

scholarly journals Portraying the Impact of the Tibetan Plateau on Global Climate

2020 ◽  
Vol 33 (9) ◽  
pp. 3565-3583 ◽  
Author(s):  
Haijun Yang ◽  
Xingchen Shen ◽  
Jie Yao ◽  
Qin Wen
Keyword(s):  
Tibetan Plateau ◽  
North Atlantic ◽  
Thermohaline Circulation ◽  
Global Climate ◽  
Tropical Pacific ◽  
The Tibetan Plateau ◽  
The North ◽  
The North Atlantic ◽  
The Impact ◽  
The Tropical Pacific

AbstractAs the most extensive highland in the world, the Tibetan Plateau (TP) plays an important role in shaping the global climate. Quantifying the effect of the TP on global climate is the first step for a full understanding of the TP’s standing on planet Earth. Through coupled model sensitivity experiments, we draw a panorama of the TP’s global impact in this paper. Our model results show that the absence of the TP would result in a 4°C colder and 10% drier climate in the Northern Hemisphere (NH). The TP has a striking remote effect on the North Atlantic. Removing the TP would enhance the westerlies in the mid- to high latitudes of the NH and weaken the easterlies over the tropical Pacific. More moisture would be relocated from the tropical Pacific to the North Atlantic, shutting down the Atlantic thermohaline circulation, which would eventually result in more than 15°C colder and 20% drier climate over the North Atlantic. Our model results suggest that the presence of the TP may have contributed greatly to the hospitable modern climate in the NH, by promoting the establishment of the thermohaline circulation in the Atlantic, and therefore enhancing the northward ocean heat transport and atmosphere moisture transport across the equator.

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