scholarly journals The Meridional Displacement of the Summer Asian Jet, Silk Road Pattern, and Tropical SST Anomalies

2016 ◽  
Vol 29 (10) ◽  
pp. 3753-3766 ◽  
Author(s):  
Xiaowei Hong ◽  
Riyu Lu
Keyword(s):  
Significant Relationship ◽  
Statistical Significance ◽  
Silk Road ◽  
Tropospheric Temperature ◽  
Temperature Anomalies ◽  
Western Asia ◽  
Meridional Displacement ◽  
Leading Mode ◽  
Silk Road Pattern ◽  
Sst Anomalies

Abstract The Silk Road pattern (SRP), which depicts the teleconnection pattern along the Asian jet, has been extensively investigated and commonly described as the leading mode of upper-tropospheric meridional wind anomalies in summer. In this study, the SRP is identified as having a significant relationship with the meridional displacement of the Asian jet (JMD), which manifests as the leading mode of upper-tropospheric zonal wind anomalies. This significant relationship is confirmed by the correlation coefficient between the indices for JMD and SRP, which is 0.39 and reaches statistical significance at the 0.01 level. When the Asian jet is in a northward (southward) displacement, the phase of SRP tends to be shown as anticyclonic (cyclonic) anomalies over western Asia and East Asia and cyclonic (anticyclonic) anomalies over Europe and central Asia. The authors propose an internal atmospheric mechanism for this relationship. In addition, it is found that the JMD is significantly affected by the tropical surface temperature anomalies. In particular, the negative (positive) SST anomalies in the tropical central and eastern Pacific of the preceding spring lead to significant cooler (warmer) tropical tropospheric temperatures in summer and may induce the northward (southward) displacement of the Asian jet through modifying the meridional gradient of tropospheric temperatures. The tropical tropospheric temperature anomalies may also affect the SRP through the JMD.

scholarly journals Interdecadal Variations of the Silk Road Pattern

2017 ◽  
Vol 30 (24) ◽  
pp. 9915-9932 ◽  
Author(s):  
Lin Wang ◽  
Peiqiang Xu ◽  
Wen Chen ◽  
Yong Liu
Keyword(s):  
Wave Train ◽  
Atlantic Multidecadal Oscillation ◽  
Teleconnection Pattern ◽  
Silk Road ◽  
Boreal Summer ◽  
Northeastern Asia ◽  
Western Asia ◽  
Silk Road Pattern ◽  
Decadal Climate ◽  
The Silk Road

Based on several reanalysis and observational datasets, this study suggests that the Silk Road pattern (SRP), a major teleconnection pattern stretching across Eurasia in the boreal summer, shows clear interdecadal variations that explain approximately 50% of its total variance. The interdecadal SRP features a strong barotropic wave train along the Asian subtropical jet, resembling its interannual counterpart. Additionally, it features a second weak wave train over the northern part of Eurasia, leading to larger meridional scale than its interannual counterpart. The interdecadal SRP contributes approximately 40% of the summer surface air temperature’s variance with little uncertainty and 10%–20% of the summer precipitation’s variance with greater uncertainty over large domains of Eurasia. The interdecadal SRP shows two regime shifts in 1972 and 1997. The latter shift explains over 40% of the observed rainfall reduction over northeastern Asia and over 40% of the observed warming over eastern Europe, western Asia, and northeastern Asia, highlighting its importance to the recent decadal climate variations over Eurasia. The Atlantic multidecadal oscillation (AMO) does not show a significant linear relationship with the interdecadal SRP. However, the Monte Carlo bootstrapping resampling analysis suggests that the positive (negative) phases of the spring and summer AMO significantly facilitate the occurrence of negative (positive) phases of the interdecadal SRP, implying plausible prediction potentials for the interdecadal variations of the SRP. The reported results are insensitive to the long-term trends in datasets and thereby have little relevance to externally forced climate change.

scholarly journals Sensitivity of Tropical Tropospheric Temperature to Sea Surface Temperature Forcing*

2003 ◽  
Vol 16 (9) ◽  
pp. 1283-1301 ◽  
Author(s):  
Hui Su ◽  
J. David Neelin ◽  
Joyce E. Meyerson
Keyword(s):  
El Niño ◽  
El Nino ◽  
Sea Surface ◽  
Eastern Pacific ◽  
Substantial Contribution ◽  
Tropospheric Temperature ◽  
Temperature Anomalies ◽  
Sst Forcing ◽  
Sst Anomaly ◽  
Sst Anomalies

Abstract During El Niño, there are substantial tropospheric temperature anomalies across the entire tropical belt associated with the warming of sea surface temperatures (SSTs) in the central and eastern Pacific. The quasi-equilibrium tropical circulation model (QTCM) is used to investigate the mechanisms for tropical tropospheric temperature response to SST forcing. In both observations and model simulations, the tropical averaged tropospheric temperature anomaly 〈T̂′〉 is approximately linear with the tropical mean SST anomaly 〈T′s〉 for observed SST forcing. Regional SST anomaly experiments are used to estimate regional sensitivity measures and quantify the degree of nonlinearity. For instance, SST anomalies of 3°C in the central Pacific would give a nonlinear 〈T̂′〉 response about 15% greater than a linear fit to small SST anomaly experiments would predict, but for the maximum observed SST anomaly in this region the response differs by only 5% from linearity. Nonlinearity in 〈T̂′〉 response is modest even when local precipitation response is highly nonlinear. While temperature anomalies have large spatial scales, the main precipitation anomaly tends to be local to the SST anomaly regions. The tropical averaged precipitation anomalies 〈P′〉 do not necessarily have a simple relation to tropical averaged tropospheric temperature anomalies or SST forcing. The approximate linearity of the 〈T̂′〉 response is due to two factors: 1) the strong nonlinearities that occur locally tend to be associated with the transport terms, which become small in the large-area average; and 2) the dependence on temperature of the top-of-atmosphere and surface fluxes has only weak nonlinearity over the range of 〈T̂′〉 variations. Analytical approximations to the QTCM suggest that the direct impact of climatological SST, via flux terms, contributes modestly to regional variations in the sensitivity α of 〈T̂′〉 to 〈T′s〉. Wind speed has a fairly strong effect on α but tends to oppose the direct effect of SST since cold SST regions often have stronger climatological wind, which would yield larger slopes. A substantial contribution to regional variation in α comes from the different reaction of moisture to SST anomalies in precipitating and nonprecipitating regions. Although regions over climatologically warm water have a slightly higher sensitivity, subregions of El Niño SST anomalies even in the colder eastern Pacific contribute substantially to tropospheric temperature anomalies.

Interdecadal Variations in the Frequency of Persistent Hot Events in Boreal Summer over Midlatitude Eurasia

2019 ◽  
Vol 32 (16) ◽  
pp. 5161-5177 ◽  
Author(s):  
Ning Shi ◽  
Yicheng Wang ◽  
Xiaoqiong Wang ◽  
Pinyu Tian
Keyword(s):  
Time Scale ◽  
Wave Train ◽  
Northern China ◽  
Stationary Wave ◽  
Silk Road ◽  
Boreal Summer ◽  
Western Asia ◽  
Silk Road Pattern ◽  
The Silk Road ◽  
Circulation Changes

ABSTRACT Based on the daily Japanese 55-year Reanalysis (JRA-55) dataset, this study reveals that southern Europe/western Asia (SEWA) and northern China are two large-scale regions that have exhibited consistent interdecadal variations in the frequency of persistent hot events (PHEs). Over the past 58 summers, the period approximately from 1973 to 1996 represents an inactive period for the occurrence of PHEs over the two regions, whereas the antecedent and subsequent periods are active periods. At the subseasonal time scale, the regional PHEs over SEWA are characterized by quasi-stationary wave train anomalies aloft from the northwest Atlantic to Europe, while the regional PHEs over northern China are characterized by quasi-stationary wave train anomalies over the Eurasian continent. The persistence of the quasi-stationary anomalies is associated with the Rossby wave propagation. Moreover, the energy extraction from the basic flow is also favorable for their persistence. Our study reveals that the above typical circulation anomalies for the PHEs over both SEWA and northern China are in phase with the background circulation changes during the two active periods. Thus, the interdecadal changes in background circulation can modulate the frequency of PHEs over the two regions simultaneously. Further analysis reveals that the background circulation changes are closely related to the interdecadal variation in the Silk Road pattern based on their similarities in both spatial pattern and temporal variation. The sea surface temperature over four particular regions seems to facilitate the phase shifts in the Silk Road pattern on the interdecadal time scale.

An Interdecadal Change of the Boreal Summer Silk Road Pattern around the Late 1990s

2020 ◽  
Vol 33 (16) ◽  
pp. 7083-7100
Author(s):  
Yong Liu ◽  
Wen Zhou ◽  
Xia Qu ◽  
Renguang Wu
Keyword(s):  
Climate Impact ◽  
Teleconnection Pattern ◽  
Silk Road ◽  
Boreal Summer ◽  
Interdecadal Change ◽  
Westerly Jet ◽  
Leading Mode ◽  
Precipitation Anomalies ◽  
Silk Road Pattern ◽  
Upper Level

AbstractThe Silk Road pattern (SRP) is a well-known teleconnection pattern along the upper-level westerly jet over the Eurasian continent during boreal summer. The SRP has experienced an interdecadal change around the late 1970s. The present study identified a new change of the SRP around the late 1990s, which is characterized by significant weakening and zonal phase shift of the major centers of the SRP during the recent decades. The recent reshaping of the SRP is attributed to an enhanced impact of precipitation anomalies over the northeastern Indian summer monsoon (ISM), which is associated with the leading mode change of the ISM precipitation anomalies around the late 1990s. The interdecadal weakening of the upper-level westerly jet over central and East Asia also favors the southward movement of the SRP during recent periods. The differences of the features, climate impact, and causes related to the recent SRP change from those related to the SRP change around the late 1970s are also contrasted in this study.

An Enhanced Influence of Tropical Indian Ocean on the South Asia High after the Late 1970s

2012 ◽  
Vol 25 (20) ◽  
pp. 6930-6941 ◽  
Author(s):  
Xia Qu ◽  
Gang Huang
Keyword(s):  
Indian Ocean ◽  
South Asia ◽  
Tropical Indian Ocean ◽  
Tropospheric Temperature ◽  
Decadal Change ◽  
The South ◽  
South Asia High ◽  
The Impact ◽  
Change In Mean ◽  
Sst Anomalies

Abstract The tropical Indian Ocean (TIO)’s influence on the South Asia high (SAH)’s intensity experiences a decadal change in the late 1970s; after (before) the decadal shift, the influence is significant (insignificant). The present study investigates the role of tropospheric temperature in relaying the impact of sea surface temperature (SST) to the SAH and the change in the TIO’s influence. During the two epochs, the local tropospheric temperature responses to the TIO warming are distinct—more significant during the second epoch. It is inferred that this change may be responsible for the strengthening of the TIO’s influence on the SAH. Encouragingly, the ensemble simulations accurately capture the time of the decadal change, indicating that the enhanced influence is attributed to the SST forcing. There are two possible reasons for the change in the TIO–SAH relationship. The first reason is the change in the locations of the SST anomalies in the TIO. During the second epoch, positive SST anomalies lie in the Indian Ocean warm pool. Through the background vigorous convection and moist adjustment, the SST anomalies affect largely the tropospheric temperature and thus the SAH. The second reason is the decadal change in mean SST and the SST variability. During the recent decades, both the background SST and the variability of the TIO SST increase, which enhance the influence of the SST anomalies on the atmosphere. The influence of the remote oceanic forcing on the enhanced TIO–SAH relationship and its comparison with the contribution of the TIO SST are also discussed.

scholarly journals Linear Atelectasis around the Hilum on Chest Radiography: A Novel Sign of Early Lung Cancer

2018 ◽  
Vol 8 ◽  
pp. 27
Author(s):  
Kerem Ozturk ◽  
Esra Soylu ◽  
Ugur Topal
Keyword(s):  
Lung Cancer ◽  
Significant Relationship ◽  
Retrospective Review ◽  
Statistical Significance ◽  
Primary Lung Cancer ◽  
Chest Radiographs ◽  
Bronchial Obstruction ◽  
Total Thickness ◽  
Patient Subgroup ◽  
Linear Shape

Background: Linear atelectasis is a focal area of subsegmental atelectasis with a linear shape. Linear atelectasis may occur as a consequence of subsegmental bronchial obstruction. Aims: We propose an early roentgen sign of obstructing lung tumors, namely perihilar linear atelectasis, and ascertain whether this phenomenon could be used as a sign to detect radiographically occult primary lung cancer. Materials and Methods: We performed a retrospective review of 45,000 posteroanterior chest radiographs to determine the frequency of appearance and characteristics of perihilar linear atelectasis. The perihilar region of chest radiographs was evaluated for the presence of linear atelectasis. When linear atelectasis was found, the total thickness was measured. Student's t-test was used to evaluate statistical significance, correlating the thickness of atelectasis and the presence of obstructing central primary lung cancer. Results: Perihilar linear atelectasis was demonstrated in 58 patients. Atelectasis was caused by an obstructing tumor in 21 (36%) cases and a variety of other conditions in 37 (64%) patients. A statistically significant relationship (P < 0.001) was observed between the dimension of perihilar linear atelectasis and primary lung cancer, with 16 of 19 patients with thick (>5.5 mm) perihilar linear atelectasis found to have primary lung cancer. Conclusion: Thick perihilar linear atelectasis is a new diagnostic roentgen sign that suggests subsegmental bronchial obstruction. In this patient subgroup, who are otherwise asymptomatic, a persistent linear atelectasis can be due to primary lung cancer.

Observed Tropospheric Temperature Response to 11-yr Solar Cycle and What It Reveals about Mechanisms

2013 ◽  
Vol 70 (1) ◽  
pp. 9-14 ◽  
Author(s):  
Jiansong Zhou ◽  
Ka-Kit Tung
Keyword(s):  
Solar Cycle ◽  
Large Scale ◽  
Stratospheric Ozone ◽  
Statistical Significance ◽  
Temperature Response ◽  
Polar Regions ◽  
Tropospheric Temperature ◽  
Tropical Ocean ◽  
Global Data ◽  
Difference Projection

Abstract Using 54 yr of NCEP reanalysis global data from 1000 to 10 hPa, this study establishes the existence and the statistical significance of the zonal-mean temperature response to the 11-yr solar cycle throughout the troposphere and parts of the lower stratosphere. Two types of statistical analysis are used: the composite-mean difference projection method, which tests the existence of the solar cycle signal level by level, and the adaptive AR(p)-t test, which tells if a particular local feature is statistically significant at the 95% confidence level. A larger area of statistical significance than that in previous published work is obtained, due to the longer record and a better trend removal process. It reveals a spatial pattern consistent with a “bottom up” mechanism, involving evaporative feedback near the tropical ocean surface and tropical vertical convection, latent heating of the tropical upper troposphere, and poleward large-scale heat transport to the polar regions. It provides an alternative to the currently favored “top down” mechanism involving stratospheric ozone heating.

Sign in / Sign up

Export Citation Format

Share Document