scholarly journals An Investigation into the Relationship between Teleconnections and Taiwan's Streamflow

2017 ◽  
Author(s):  
Chia-Jeng Chen ◽  
Tsung-Yu Lee
Keyword(s):  
Large Scale ◽  
Critical Role ◽  
Phase Relationship ◽  
Temporal Variations ◽  
Prediction Skill ◽  
Climate Indices ◽  
Pacific Basin ◽  
Linear Regression Models ◽  
Quasi Biennial Oscillation ◽  
The Relationship

Abstract. Interannual variations in catchment streamflow represent an integrated response to anomalies in regional moisture transport and atmospheric circulations and are ultimately linked to large-scale climate oscillations. This study investigates the relationship between Taiwan’s long-term summertime (July to September, JAS) streamflow and manifold teleconnection patterns. Lagged correlation analysis is conducted to calculate how JAS streamflow data derived at 28 upstream and 13 downstream gauges in Taiwan correlate with 14 teleconnection indices in the current or preceding seasons. Of the many indices, the West-Pacific and Pacific-Japan (PJ) patterns, both of which play a critical role in determining cyclonic activity in the western North Pacific basin, exhibit the highest concurrent correlations (most significant r = 0.50) with the JAS flows in Taiwan. Alternately, the Quasi-Biennial Oscillation averaged over the period from the previous October to June of the current year is significantly correlated with the JAS flows (most significant r = −0.66), indicating some forecasting utility. By further examining the correlation results using a 20-year moving window, peculiar temporal variations and possible climate regime shifts (CRSs) can be revealed. To identify suspicious, abrupt changes in the correlation, a CRS test is employed. The late 1970s and 1990s are identified as two significant change points, and during the intermediate period, a marked in-phase relationship (r > 0.8) between Taiwan's streamflow and the PJ index is observed. Linear regression models that incorporate the climate indices into streamflow prediction are found to provide reasonable prediction skill in general, and the models are then used to illustrate the dramatic variations in prediction skill from the pre- to post-regime shift epoch. It is verified that the two shifts are in concordance with the alteration of large-scale circulations in the Pacific basin. The changes in pattern correlation and composite maps before and after the change point are discussed, and our results suggest that empirical forecasting techniques should take into account the effect of CRSs on predictor screening.

scholarly journals On the Relationship between Teleconnections and Taiwan's Streamflow: Evidence of Climate Regime Shift and Implications for Seasonal Forecasting

2016 ◽  
Author(s):  
Chia-Jeng Chen ◽  
Tsung-Yu Lee
Keyword(s):  
Large Scale ◽  
Critical Role ◽  
Phase Relationship ◽  
Temporal Variations ◽  
Pacific Basin ◽  
Climate Regime ◽  
Quasi Biennial Oscillation ◽  
Teleconnection Patterns ◽  
Integrated Response ◽  
The Relationship

Abstract. Interannual variations of catchment streamflow represent an integrated response to anomalies in regional moisture transport and atmospheric circulations, ultimately linked to large-scale climate oscillations. This study investigates the relationship between Taiwan's long-term summertime (July to September, JAS) streamflow and manifold teleconnection patterns. Lagged correlation analysis is conducted to calculate how JAS streamflow data derived at 28 upstream and 13 downstream gauges in Taiwan correlate with 14 teleconnection indices in the concurrent or preceding seasons. Out of the many indices, the West-Pacific and Pacific-Japan (PJ) patterns, both of which play a critical role in determining cyclonic activity in the western North Pacific basin, exhibit the highest concurrent correlations (most significant r = 0.48) with the JAS flows in Taiwan. At a one-month lead time, on the other hand, the Quasi-Biennial Oscillation significantly correlate with the JAS flows (most significant r = −0.66), indicating some forecasting utility. By further examining the correlation results using a 20-year moving window, peculiar temporal variations and possible climate regime shifts (CRS) can be revealed. To identify suspicious, abrupt changes in the correlation, a CRS test is employed. The late 1970s and 1990s are identified as two significant change points, and during the intermediate period, a marked in-phase relationship (r ~ 0.9) between Taiwan's streamflow and the PJ index is observed. It is verified that the two shifts are in concordance with the alteration of large-scale circulations in the Pacific basin. Discussion about the changes in pattern correlation and composite maps before and after the change point is carried out, and our results suggest that empirical forecasting techniques should take into account the effect of CRS on predictor screening.

scholarly journals Variations in the correlation between teleconnections and Taiwan's streamflow

2017 ◽  
Vol 21 (7) ◽  
pp. 3463-3481 ◽  
Author(s):  
Chia-Jeng Chen ◽  
Tsung-Yu Lee
Keyword(s):  
Large Scale ◽  
Critical Role ◽  
Phase Relationship ◽  
Temporal Variations ◽  
Pacific Basin ◽  
Quasi Biennial Oscillation ◽  
Intermediate Period ◽  
Before And After ◽  
Composite Maps ◽  
Integrated Response

Abstract. Interannual variations in catchment streamflow represent an integrated response to anomalies in regional moisture transport and atmospheric circulations and are ultimately linked to large-scale climate oscillations. This study conducts correlation analysis to calculate how summertime (July–September, JAS) streamflow data derived at 28 upstream and 13 downstream gauges in Taiwan correlate with 14 teleconnection indices in the current or preceding seasons. We find that the western Pacific (WP) and Pacific–Japan (PJ) patterns, both of which play a critical role in determining cyclonic activity in the western North Pacific basin, exhibit the highest concurrent correlations (most significant r = 0. 50) with the JAS flows in Taiwan. Alternatively, the Quasi-Biennial Oscillation (QBO) averaged over the period from the previous October to June of the current year is significantly correlated with the JAS flows (most significant r = −0. 66), indicating some forecasting utility. By further examining the correlation results using a 20-year moving window, peculiar temporal variations and possible climate regime shifts (CRSs) can be revealed. A CRS test is employed to identify suspicious and abrupt changes in the correlation. The late 1970s and 1990s are identified as two significant change points. During the intermediate period, Taiwan's streamflow and the PJ index exhibit a marked in-phase relationship (r > 0. 8). It is verified that the two shifts are in concordance with the alteration of large-scale circulations in the Pacific basin by investigating the changes in pattern correlation and composite maps before and after the change point. Our results suggest that empirical forecasting techniques should take into account the effect of CRSs on predictor screening.

scholarly journals Hydrological alteration of the upper Yangtze River and its possible links with large-scale climate indices

2019 ◽  
Vol 50 (4) ◽  
pp. 1120-1137
Author(s):  
Qianjin Dong ◽  
Debin Fang ◽  
Jian Zuo ◽  
Yongqiang Wang
Keyword(s):  
Yangtze River ◽  
Water Resource Management ◽  
Large Scale ◽  
Phase Relationship ◽  
Wavelet Coherence ◽  
Climate Indices ◽  
Hydrological Alteration ◽  
Upper Yangtze River ◽  
The Relationship ◽  
The Upper Yangtze River

Abstract The relationship between hydrological alteration and climate variability in the upper Yangtze River is not fully understood. In this paper, the periodicity features and the intercorrelation of annual and seasonal eco-flow metrics at the Yichang gauge station are analyzed for the period 1882 to 2013. Analysis is carried out to explore the formation of the eco-flow metrics and the possible linkages between eco-flow metrics and selected climate indices, using the cross-wavelet and wavelet coherence methods on data from 1948 to 2013. The results show that the variation of eco-flow metrics correlates well with some selected climate indices, but changes in different eco-flow metrics are complex. Most annual and seasonal eco-flow metrics correlate well with the Northern Hemisphere (N.H) and Indian Ocean Dipole (IOD) and have a significant common power in the two to four years band. In addition, most annual eco-flow metrics have an obvious phase relationship with the selected climate indices. However, the seasonal eco-flow metrics have no significant phase relationship with the selected climate indices. These findings provide a better understanding of how hydrological alterations of the streamflow and better water resource management can ensure ecosystem sustainability for the Yangtze River.

scholarly journals Large Scale Solar Magnetic Fields: Temporal Variations

2004 ◽  
Vol 219 ◽  
pp. 552-556 ◽  
Author(s):  
R. Knaack ◽  
J. O. Stenflo
Keyword(s):  
Magnetic Field ◽  
Time Series ◽  
Large Scale ◽  
Solar Magnetic Field ◽  
Temporal Variations ◽  
Solar Photosphere ◽  
Solar Cycles ◽  
Radial Magnetic Field ◽  
Quasi Biennial Oscillation ◽  
Harmonic Decomposition

We have investigated the temporal evolution of the solar magnetic field during solar cycles 20, 21 and 22 by means of spherical harmonic decomposition and subsequent time series analysis. A 33 yr and a 25 yr time series of daily magnetic maps of the solar photosphere, recorded at the Mt. Wilson and NSO/Kitt Peak observatories respectively, were used to calculate the spherical coefficients of the radial magnetic field. Fourier and wavelet analysis were then applied to deduce the temporal variations. We compare the results of the two datasets and present examples of zonal modes which show significant variations, e. g. with a period of approx. 2.0—2.5 years. We provide evidence that this quasi-biennial oscillation originates mainly from the southern hemisphere. Furthermore, we show that low degree modes with odd l — m exhibit periods of 29.2 and 28.1 days while modes with even l — m show a dominant period of 26.9 days. A resonant modal structure of the solar magnetic field (apart from the 22 yr cycle) has not been found.

scholarly journals Assessing the contribution of ENSO and MJO to Australian dust activity based on satellite and ground-based observations

2020 ◽  
Author(s):  
Yan Yu ◽  
Paul Ginoux
Keyword(s):  
El Niño ◽  
Large Scale ◽  
El Nino ◽  
Southern Oscillation ◽  
Regional Climate ◽  
Critical Role ◽  
Temporal Variations ◽  
Austral Spring ◽  
Maximum Enhancement ◽  
Eastern Australia

Abstract. Despite Australian dust's critical role in the regional climate and surrounding marine ecosystems, the controlling factors of the spatio-temporal variations of Australian dust are not fully understood. Here we assess the connections between observed spatial-temporal variations of Australian dust with key modes of large-scale climate variability, namely the El Niño-Southern Oscillation (ENSO) and Madden-Julian Oscillation (MJO). Multiple dust observations from Aerosol Robotic Network (AERONET), weather stations, and satellite instruments, namely the Moderate Resolution Imaging Spectroradiometer (MODIS) and Multi-angle Imaging SpectroRadiometer (MISR) are examined. The assessed multiple dust observations consistently identify the natural and agricultural dust hotspots in Australia, including the Lake Eyre Basin, Lake Torrens Basin, Lake Frome Basin, Simpson Desert, Barwon-Darling Basin, Riverina, Barkly Tableland, and lee side of the Great Diving Range, as well as a country-wide, austral spring-to-summer peak in dust activity. Our regression analysis of observed dust optical depth (DOD) upon an ocean Niño index confirms previous model-based finding on the enhanced dust activity in southern and eastern Australia during the subsequent austral spring and summer dust season following the strengthening of austral wintertime El Niño. Our analysis further indicates the modulation of the ENSO-dust relationship with the MJO phases. During sequential MJO phases, the dust-active center moves from west to east associated with the eastward propagation of MJO, with maximum enhancement in dust activity at about 120° E, 130° E, and 140° E corresponding to MJO phases 1–2, 3–4, and 5–6, respectively. MJO phases 3–6 are favorable for enhanced ENSO modulation of dust activity, especially the occurrence of extreme dust events, in southeastern Australia, currently hypothesized to be attributed to the interaction between MJO-induced anomalies in convection and wind and ENSO-induced anomalies in soil moisture and vegetation.

CANONICAL CORRELATION AMONG LARGE SCALE OSCILLATIONS, TEMPERATURE AND PRECIPITATION IN COASTAL REGIONS OF COLOMBIA

2017 ◽  
Author(s):  
Diana Díaz ◽  
Diana Díaz ◽  
Nancy Villegas ◽  
Nancy Villegas
Keyword(s):  
North Atlantic ◽  
Canonical Correlation ◽  
Large Scale ◽  
Climate Indices ◽  
Coastal Regions ◽  
Quasi Biennial Oscillation ◽  
Data Set ◽  
Climatic Oscillations ◽  
Temperature And Precipitation ◽  
Biennial Oscillation

This study examines relationships between available surface meteorology variables and climatic oscillations by using canonical correlation analysis (CCA). Canonical loadings and cross loadings from CCA are evaluated for meteorological stations located over coastal regions of Colombia. The tests, used for these studies, consider the temperature, the precipitation data, three of the main oscillations – the Ocean Niño Index (ONI), North Atlantic Oscillation (NAO), and the Quasi-biennial oscillation (QBO). The results show the power of the statistical method used to identify associations on the data set with an acceptable level of confidence using multivariate approach. The analysis reveals relations mostly between the variables and the ENSO for all cases and a discrete connection with the NAO and QBO. To add climate indices to the group of independent variables increased the variance rates between 5 and 7%.

scholarly journals Intraseasonal Tropical Cyclogenesis Prediction in a Global Coupled Model System

2018 ◽  
Vol 31 (15) ◽  
pp. 6209-6227 ◽  
Author(s):  
Xianan Jiang ◽  
Baoqiang Xiang ◽  
Ming Zhao ◽  
Tim Li ◽  
Shian-Jiann Lin ◽  
...  
Keyword(s):  
Large Scale ◽  
Critical Role ◽  
Coupled Model ◽  
Model System ◽  
Prediction Skill ◽  
Tropical Cyclogenesis ◽  
Weather Extremes ◽  
Low Level ◽  
Predictive Skill ◽  
Global Coupled Model

Motivated by increasing demand in the community for intraseasonal predictions of weather extremes, predictive skill of tropical cyclogenesis is investigated in this study based on a global coupled model system. Limited intraseasonal cyclogenesis prediction skill with a high false alarm rate is found when averaged over about 600 tropical cyclones (TCs) over global oceans from 2003 to 2013, particularly over the North Atlantic (NA). Relatively skillful genesis predictions with more than 1-week lead time are only evident for about 10% of the total TCs. Further analyses suggest that TCs with relatively higher genesis skill are closely associated with the Madden–Julian oscillation (MJO) and tropical synoptic waves, with their geneses strongly phase-locked to the convectively active region of the MJO and low-level cyclonic vorticity associated with synoptic-scale waves. Moreover, higher cyclogenesis prediction skill is found for TCs that formed during the enhanced periods of strong MJO episodes than those during weak or suppressed MJO periods. All these results confirm the critical role of the MJO and tropical synoptic waves for intraseasonal prediction of TC activity. Tropical cyclogenesis prediction skill in this coupled model is found to be closely associated with model predictability of several large-scale dynamical and thermodynamical fields. Particularly over the NA, higher predictability of low-level relative vorticity, midlevel humidity, and vertical zonal wind shear is evident along a tropical belt from the West Africa coast to the Caribbean Sea, in accord with more predictable cyclogenesis over this region. Over the extratropical NA, large-scale variables exhibit less predictability due to influences of extratropical systems, leading to poor cyclogenesis predictive skill.

scholarly journals Effect of Road Traffic on Air Pollution. Experimental Evidence from COVID-19 Lockdown

2020 ◽  
Vol 12 (21) ◽  
pp. 8984 ◽  
Author(s):  
Riccardo Rossi ◽  
Riccardo Ceccato ◽  
Massimiliano Gastaldi
Keyword(s):  
Air Quality ◽  
Large Scale ◽  
Road Traffic ◽  
Statistical Tests ◽  
Traffic Flows ◽  
Linear Regression Models ◽  
Sources Of Pollution ◽  
Urban Contexts ◽  
The Relationship ◽  
The City

The increasing concentration of human activities in cities has been leading to a worsening in air quality, thus negatively affecting the lives and health of humans living in urban contexts. Transport is one of the main sources of pollution in such environments. Several local authorities have therefore implemented strict traffic-restriction measures. The aim of this paper is to evaluate the effectiveness and limitations of these interventions, by analyzing the relationship between traffic flows and air quality. The used dataset contains concentrations of NO, NO2, NOx and PM10, vehicle counts and meteorology, all collected during the COVID-19 lockdown in the city of Padova (Italy), in which severe limitations to contain the spread of the virus simulated long and large-scale traffic restrictions in normal conditions. In particular, statistical tests, correlation analyses and multivariate linear regression models were applied to non-rainy days in 2020, 2018 and 2017, in order to isolate the effect of traffic. Analysis indicated that vehicle flows significantly affect NO, NO2, and NOx concentrations, although no evidence of a relationship between traffic and PM10 was highlighted. According to this perspective, measures to limit traffic flows seem to be effective in improving air quality only in terms of reducing nitrogen oxide.

Estimation of winter PM2.5 concentrations in East Asia associated with climate variability

2020 ◽  
Author(s):  
Jaein Jeong ◽  
Rokjin Park ◽  
Sang-Wook Yeh ◽  
Joon-Woo Roh
Keyword(s):  
Climate Variability ◽  
East Asia ◽  
Transport Model ◽  
Climate Index ◽  
Anthropogenic Emissions ◽  
Climate Indices ◽  
Linear Regression Models ◽  
Chemical Transport Model ◽  
High Position ◽  
The Relationship

<p>Interannual variability in large circulations associated with climate connections, such as monsoon and El Niño, have a significant impact on winter PM<sub>2.5</sub> concentrations in East Asia. In this study, we use the global 3D chemical transport model (GEOS-Chem) over the last 35 years to investigate the relationship between major climate variability and winter PM<sub>2.5</sub> concentrations in East Asia. First, the model is evaluated by comparing the simulated and observed aerosol concentrations with the ground and satellite-based aerosol concentrations. The results indicate that this model well reproduces the variability and magnitude of aerosol concentrations observed in East Asia. Sensitivity simulations are then used with fixed anthropogenic emissions to investigate the effects of meteorological variability on changes in aerosol concentrations in East Asia. The variability of winter PM<sub>2.5</sub> concentrations in northern East Asia was found to be closely correlated with ENSO and Siberian high position. To predict PM<sub>2.5</sub> concentrations using key climate indices, we develop multiple linear regression models. As a result, the predicted winter PM<sub>2.5</sub> concentrations using the key climate index are well reproduced in the simulated PM<sub>2.5</sub> concentrations, especially in northern East Asia.</p>

CANONICAL CORRELATION AMONG LARGE SCALE OSCILLATIONS, TEMPERATURE AND PRECIPITATION IN COASTAL REGIONS OF COLOMBIA

2017 ◽  
Author(s):  
Diana Díaz ◽  
Diana Díaz ◽  
Nancy Villegas ◽  
Nancy Villegas
Keyword(s):  
North Atlantic ◽  
Canonical Correlation ◽  
Large Scale ◽  
Climate Indices ◽  
Coastal Regions ◽  
Quasi Biennial Oscillation ◽  
Data Set ◽  
Climatic Oscillations ◽  
Temperature And Precipitation ◽  
Biennial Oscillation

This study examines relationships between available surface meteorology variables and climatic oscillations by using canonical correlation analysis (CCA). Canonical loadings and cross loadings from CCA are evaluated for meteorological stations located over coastal regions of Colombia. The tests, used for these studies, consider the temperature, the precipitation data, three of the main oscillations – the Ocean Niño Index (ONI), North Atlantic Oscillation (NAO), and the Quasi-biennial oscillation (QBO). The results show the power of the statistical method used to identify associations on the data set with an acceptable level of confidence using multivariate approach. The analysis reveals relations mostly between the variables and the ENSO for all cases and a discrete connection with the NAO and QBO. To add climate indices to the group of independent variables increased the variance rates between 5 and 7%.

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