| 1. |
- Cao, Qing, et al.
(författare)
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Impact of ENSO regimes on developing- and decaying-phase precipitation during rainy season in China
- 2017
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Ingår i: Hydrology and Earth System Sciences. - : Copernicus GmbH. - 1027-5606 .- 1607-7938. ; 21:11, s. 5415-5426
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Tidskriftsartikel (refereegranskat)abstract
- This study investigated the influence of five El Niño-Southern Oscillation (ENSO) types on rainy-season precipitation in China: central Pacific warming (CPW), eastern Pacific cooling (EPC), eastern Pacific warming (EPW), conventional ENSO and ENSO Modoki. The multi-scale moving t test was applied to determine the onset and withdrawal of rainy season. Results showed that the precipitation anomaly can reach up to 30 % above average precipitation during decaying CPW and EPW phases. Developing EPW could cause decreasing precipitation over large areas in China with 10-30 % lower than average precipitation in most areas. Conventional El Niño in the developing phase had the largest influence on ENSO-related precipitation among developing ENSO and ENSO Modoki regimes. Decaying ENSO also showed a larger effect on precipitation anomalies, compared to decaying ENSO Modoki. The difference between rainy-season precipitation under various ENSO regimes may be attributed to the combined influence of anti-cyclone in the western North Pacific and the Indian monsoon. Stronger monsoon and anti-cyclone are associated with enhanced rainy-season precipitation. The results suggest a certain predictability of rainy-season precipitation related to ENSO regimes.
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| 2. |
- Cao, Qing, et al.
(författare)
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On the predictability of daily rainfall during rainy season over the Huaihe River Basin
- 2019
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Ingår i: Water. - : MDPI AG. - 2073-4441. ; 11:5
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Tidskriftsartikel (refereegranskat)abstract
- In terms of climate change and precipitation, there is large interest in how large-scale climatic features affect regional rainfall amount and rainfall occurrence. Large-scale climate elements need to be downscaled to the regional level for hydrologic applications. Here, a new Nonhomogeneous Hidden Markov Model (NHMM) called the Bayesian-NHMM is presented for downscaling and predicting of multisite daily rainfall during rainy season over the Huaihe River Basin (HRB). The Bayesian-NHMM provides a Bayesian method for parameters estimation. The model avoids the risk to have no solutions for parameter estimation, which often occurs in the traditional NHMM that uses point estimates of parameters. The Bayesian-NHMM accurately captures seasonality and interannual variability of rainfall amount and wet days during the rainy season. The model establishes a link between large-scale meteorological characteristics and local precipitation patterns. It also provides a more stable and efficient method to estimate parameters in the model. These results suggest that prediction of daily precipitation could be improved by the suggested new Bayesian-NHMM method, which can be helpful for water resources management and research on climate change.
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| 3. |
- Cao, Qing, et al.
(författare)
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ENSO influence on rainy season precipitation over the Yangtze River Basin
- 2017
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Ingår i: Water. - : MDPI AG. - 2073-4441. ; 9:7
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Tidskriftsartikel (refereegranskat)abstract
- The paper explores the impact of El Niño-Southern Oscillation (ENSO) on rainy season precipitation properties over the Yangtze River Basin. The multi-scale moving t-test was used to determine the onset and withdrawal of the rainy season. Results showed the following: (1) Onset and withdrawal of the averaged rainy season over the Yangtze River Basin showed a similar distribution and both progressed northwards and westwards. There is a trend for delayed onset of rainy season precipitation over the Yangtze River Basin. A similar trend in the withdrawal of rainy season precipitation was not found. (2) The decaying Central and Eastern PacificWarming are indicative of wet signals in the Yangtze River Basin, with precipitation anomalies up to 25% above normal. The decaying Eastern Pacific Cooling and developing Eastern PacificWarming are indicative of dry signals over the Yangtze River Basin, with 5-20% lower than average precipitation (3) ENSO Modoki in the developing phase is more important than the developing ENSO when it comes to present wetter or drier signals. Conversely, the decaying ENSO shows more prominent wet or dry signals than the decaying ENSO Modoki.
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| 4. |
- Chen, Sichun, et al.
(författare)
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Spatiotemporal Changes in Precipitation and Temperature in the Huaibei Plain and the Relation between Local Precipitation and Global Teleconnection Patterns
- 2019
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Ingår i: Journal of Hydrologic Engineering. - 1084-0699. ; 24:8
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Tidskriftsartikel (refereegranskat)abstract
- The Huaibei Plain is one of the most severe water scarcity areas in China. Understanding of hydroclimatic variation in this area at different timescales and its relationship with global teleconnection patterns are important for assessment of water resources utilization. In this study, spatiotemporal changes of seasonal and annual precipitation and temperature, including trend, abrupt change, variability, and periodicity were examined to recognize the potential remarkable changes during the last 41 years. The relationship between precipitation in the Huaibei Plain and teleconnection patterns using climate indexes was revealed by applying singular value decomposition. Results showed a nonsignificant annual precipitation increase about 2.4 mm/year. The annual average temperature increased about 1.2°C during 1970-2010. The abrupt change of annual precipitation mainly occurred during the 1970s and 1980s, while the primary mutation points for temperature were detected in 1990s, especially in 1997. The mean areal precipitation is characterized by a statistically significant 2- to 4-year periodicity at different phases, and the 2- to 5-year band is the major cycle for annual average temperature in this region. A statistically strong 5- to 8-year periodicity for precipitation could be detected from the middle of the 1980s to the end of the 1990s. Precipitation has positive correlation with the West Pacific Pattern and El Nino Southern Oscillation. The investigated results might have considerable implications for managing water resources in the Huaibei Plain.
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| 5. |
- Du, Yiheng, et al.
(författare)
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Hydrologic response of climate change in the source region of the Yangtze River, based on water balance analysis
- 2017
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Ingår i: Water. - : MDPI AG. - 2073-4441. ; 9:2
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Tidskriftsartikel (refereegranskat)abstract
- Due to the large amount of water resources stored in glaciers, permafrost, and lakes, the source region of the Yangtze River (SRYR) is of great importance for the overall basin water flow. For this purpose, a state of art review and calculations were made for the period 1957-2013 using observed hydrological and meteorological data with a water balance approach. Actual evapotranspiration was calculated and validated by empirical formulas. Water storage change analysis was conducted with uncertainty boundaries using a 10-year moving window. Results show that temperature, precipitation, and actual evapotranspiration in the SRYR increased by 0.34°C, 11.4 mm, and 7.6 mm per decade, respectively (significant at 0.05 probability level). Runoffappears to have increased at a rate of 3.3 mm per decade. The SRYR water storage in total has not changed significantly during the period, although the moving average is mostly below zero. Based on the water balance equation, the increase in calculated evapotranspiration is mainly due to the significantly increasing temperature. This in combination with increasing precipitation leads to a relatively stable water storage during the study period. Correlation analyses show that precipitation dominates runoffduring the warm season (May to October), while temperature anomalies dominate the runoffduring the cold season (November to April). The influence of temperature on runoffseems to enhance during the winter period.
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| 6. |
- du, Yiheng, et al.
(författare)
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Integrated large‐scale circulation impact on rainy season precipitation in the source region of the Yangtze River
- 2020
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Ingår i: International Journal of Climatology. - : Wiley. - 1097-0088 .- 0899-8418. ; 40:4, s. 2285-2295
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Tidskriftsartikel (refereegranskat)abstract
- Monthly precipitation data at regular grids of 0.5° × 0.5° derived from observations during June–August 1961–2016 were used to reveal characteristics of large‐scale circulations associated with rainy season precipitation over the source region of the Yangtze River (SRYR). The integrated impact of major influencing circulation patterns was examined by principal component analysis and composites. Results showed that the first rainy season precipitation mode associates with the Southern Oscillation Index (SOI) and the Pacific Decadal Oscillation (PDO), explaining 64% of spatial and temporal rainy season precipitation variance in the region. Composites of precipitation pattern under different phases of SOI and PDO revealed that the effect of PDO on precipitation varies with the SOI phase. When out of phase with the SOI, PDO‐induced precipitation anomalies are magnified. When they are in phase, anomalies weaken or even disappear. Composites of moisture flux patterns show that large‐scale atmospheric circulation affects the strength of westerlies that transport moisture to the study area and formation of convergence. In coming decades, the PDO is likely to continue in a negative phase with La Niña (positive SOI) events, implying more precipitation during the rainy season. Consequently, this knowledge can be used to improve decision making regarding water supply and flood risk management in the SRYR.
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| 7. |
- du, Yiheng, et al.
(författare)
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Multi-Space Seasonal Precipitation Prediction Model Applied to the Source Region of the Yangtze River, China
- 2019
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Ingår i: Water. - 2073-4441. ; 11:12
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Tidskriftsartikel (refereegranskat)abstract
- This paper developed a multi-space prediction model for seasonal precipitation using a high-resolution grid dataset (0.5° × 0.5°) together with climate indices. The model is based on principal component analyses (PCA) and artificial neural networks (ANN). Trend analyses show that mean annual and seasonal precipitation in the area is increasing depending on spatial location. For this reason, a multi-space model is especially suited for prediction purposes. The PCA-ANN model was examined using a 64-grid mesh over the source region of the Yangtze River (SRYR) and was compared to a traditional multiple regression model with a three-fold cross-validation method. Seasonal precipitation anomalies (1961–2015) were converted using PCA into principal components. Hierarchical lag relationships between principal components and each potential predictor were identified by Spearman rank correlation analyses. The performance was compared to observed precipitation and evaluated using mean absolute error, root mean squared error, and correlation coefficient. The proposed PCA-ANN model provides accurate seasonal precipitation prediction that is better than traditional regression techniques. The prediction results displayed good agreement with observations for all seasons with correlation coefficients in excess of 0.6 for all spatial locations.
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| 8. |
- Yuan, Feifei, et al.
(författare)
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Changes in precipitation extremes over the source region of the Yellow River and its relationship with teleconnection patterns
- 2020
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Ingår i: Water. - 2073-4441. ; 12:4
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Tidskriftsartikel (refereegranskat)abstract
- Precipitation extremes and their underlying causes are important processes to understand to plan appropriate adaptation measures. This paper presents an analysis of the spatiotemporal variability and trend of precipitation extremes in the important source region of the Yellow River and explores the connection to global teleconnection patterns and the 850-mb vector wind. Six indices for precipitation extremes were computed and analyzed for assessment of a changing regional climate. Results showed that these indices have a strong gradient from the northwest to the southeast part for the period 1961-2015, due to the great influence from the south-easterly summer monsoon flow. However, no statistically significant trends were found for the defined indices at the majority of stations, and their spatial distribution are noticed by irregularly mixed positive and negative changes except for the maximum number of consecutive wet days (CWD). Singular value decomposition analysis revealed that the precipitation extreme indices-including annual total precipitation when daily precipitation >95th percentile (R95p), annual count of days with daily precipitation ≥10 mm (R10mm), annual maximum consecutive 5-day precipitation (R5d), total precipitation divided by the number of wet days (SDII), and CWD-are negatively related to the El Nino-Southern Oscillation (NINO 3.4) in the first mode, and the maximum number of consecutive dry days (CDD) is positively related to the Scandinavian pattern in the second mode at 0.05 significance level. The 850-mb vector wind analysis showed that the southwestern monsoon originating from the Indian Ocean brings sufficient moisture to this region. Furthermore, the anti-cyclone in the western part of the North Pacific plays a significant role in the transport of moisture to the source region of the Yellow River. The links between precipitation extremes and teleconnection patterns explored in this study are important for better prediction and preparedness of climatic extremes.
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| 9. |
- Yuan, Feifei, et al.
(författare)
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Hydro Climatic Trend and Periodicity for the Source Region of the Yellow River
- 2015
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Ingår i: Journal of Hydrologic Engineering. - 1084-0699. ; 20:10
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Tidskriftsartikel (refereegranskat)abstract
- The hydrology of the Yellow River source region is expected to be affected by coming climate change. This will have repercussions for the 110million basin inhabitants. Consequently, precipitation, temperature, and streamflow trends and periodicities during the last 50years were investigated to identify significant changes in time and space over the study area. Results showed that mean annual temperature increased for all stations and it had an accelerated increasing trend during the last decade. Mean annual precipitation trends varied depending on the station; however, they were generally slightly decreasing. Annual streamflow decreased markedly, especially from the 1990s, but showed recovery during recent years. Statistically significant changes in trend occurred for temperature in 1998 and for streamflow in 1990. Based on the streamflow change point, seasonal analysis results showed that precipitation mainly decreased during the summer monsoon period (July-September) and temperature increased throughout the year. Corresponding to the weakened monsoon period the average runoff depth is decreasing by 0.74mm/year over the whole area. Statistically significant 2- to 4-year periodicities for mean areal precipitation and temperature occurred over the area. For streamflow, an even stronger 8-year periodicity was revealed from the end of the 1960s to the beginning of the 1990s. Frequency analysis investigated the magnitudes of mean annual precipitation and discharge corresponding to a given frequency. Hydroclimatic trends and linkages at each subbasin were investigated to further improve the understanding of observed streamflow changes. The investigated results have important implications for future water availability in the Yellow River source region.
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| 10. |
- Yuan, Feifei, et al.
(författare)
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Regional sea-surface temperatures explain spatial and temporal variation of summer precipitation in the source region of the Yellow River
- 2016
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Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 61:8, s. 1383-1394
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Tidskriftsartikel (refereegranskat)abstract
- The summer precipitation (June–September) in the source region of the Yellow River accounts for about 70% of the annual total, playing an important role in water availability. This study divided the source region of the Yellow River into homogeneous zones based on precipitation variability using cluster analysis. Summer precipitation trends and teleconnections with global sea-surface temperatures (SST) and the Southern Oscillation Index (SOI) from 1961 to 2010 were investigated by Mann-Kendall test and Pearson product-moment correlation analysis. The results show that the northwest part (Zone 1) had a non-significantly increasing trend, and the middle and southeast parts (zones 2 and 3) that receive the most precipitation displayed a statistically significant decreasing trend for summer precipitation. The summer precipitation in the whole region showed statistically significant negative correlations with the central Pacific SST for 0–4 month lag and with the Southern Indian and Atlantic oceans SST for 5–8 month lag. Analyses of sub-regions reveal intricate and complex correlations with different SST areas that further explain the summer precipitation variability. The SOI had significant positive correlations, mainly for 0–2 months lag, with summer precipitation in the source region of the Yellow River. It is seen that El Niño Southern Oscillation (ENSO) events have an influence on summer precipitation, and the predominant negative correlations indicate that higher SST in equatorial Pacific areas corresponding to El Niño coincides with less summer precipitation in the source region of the Yellow River. Editor Z.W. Kundzewicz; Associate editor D. Gerten
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