scholarly journals Extending seasonal predictability of Yangtze River summer floods

2018 ◽  
Author(s):  
Shanshan Wang ◽  
Xing Yuan
Keyword(s):  
El Niño ◽  
Yangtze River ◽  
El Nino ◽  
Yangtze River Basin ◽  
Summer Precipitation ◽  
Moisture Flux ◽  
Atmospheric Moisture ◽  
Potential Predictability ◽  
Strongly Connected ◽  
Flooding Events

Abstract. Extreme pluvial floods across China's Yangtze River basin in the summer of 2016 was strongly connected with intense atmospheric moisture transport, and resulted in vast loss of properties after a strong El Niño winter. Predicting such extreme floods in advance is essential for hazard mitigation, but the flood forecast skill is relatively low due to the limited predictability of summer precipitation. By using a perfect model assumption, here we show that atmospheric moisture flux has a higher potential predictability than precipitation over the Yangtze River at seasonal time scales. The predictability of precipitation and moisture are higher in post-El Niño summers than those in post-La Niñas, especially for flooding events. As compared with extreme precipitation, the potential detectability of extreme moisture increases by 20 % in post-El Niño summers, which suggests that atmospheric moisture could be crucial for early warning of Yangtze River summer floods.

scholarly journals Extending seasonal predictability of Yangtze River summer floods

2018 ◽  
Vol 22 (8) ◽  
pp. 4201-4211 ◽  
Author(s):  
Shanshan Wang ◽  
Xing Yuan
Keyword(s):  
El Niño ◽  
Yangtze River ◽  
El Nino ◽  
Yangtze River Basin ◽  
Summer Precipitation ◽  
Moisture Flux ◽  
Atmospheric Moisture ◽  
Potential Predictability ◽  
Strongly Connected ◽  
Flooding Events

Abstract. Extreme pluvial floods across China's Yangtze River basin in the summer of 2016 were strongly connected with intense atmospheric moisture transport, and resulted in vast loss of properties after a strong El Niño winter. Predicting such extreme floods in advance is essential for hazard mitigation, but the flood forecast skill is relatively low due to the limited predictability of summer precipitation. By using a “perfect model” assumption, here we show that atmospheric moisture flux has a higher potential predictability than precipitation over the Yangtze River at seasonal timescales. The predictability of precipitation and moisture flux is higher in post-El Niño summers than in post-La Niñas, especially for flooding events. As compared with extreme precipitation, the potential detectability of extreme moisture flux increases by 20 % in post-El Niño summers, which suggests that atmospheric moisture flux could be crucial for early warning of Yangtze River summer floods.

scholarly journals Diagnosis of Tropospheric Moisture over Saudi Arabia and Influences of IOD and ENSO

2006 ◽  
Vol 134 (2) ◽  
pp. 598-617 ◽  
Author(s):  
Arun Chakraborty ◽  
Swadhin K. Behera ◽  
Milind Mujumdar ◽  
Ryohji Ohba ◽  
Toshio Yamagata
Keyword(s):  
Saudi Arabia ◽  
Correlation Coefficient ◽  
Red Sea ◽  
El Niño ◽  
El Nino ◽  
Moisture Flux ◽  
Boreal Summer ◽  
Atmospheric Moisture ◽  
Middle Troposphere ◽  
Peak Correlation

Abstract A diagnostic study of atmospheric moisture data over Saudi Arabia derived from a 43-yr National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) reanalysis revealed that moisture convergence in the lower troposphere and divergence in and above the middle troposphere occurs throughout the year. Although the amount of precipitable water content in the middle troposphere is high, precipitation is less than expected over this semiarid region during a boreal summer monsoon season because of strong moisture divergence. The net tropospheric moisture flux over the arid and semiarid regions of Saudi Arabia shows seasonal and interannual variability. The seasonal variability has a strong semiannual signal with its primary peak February–April and its secondary peak June–August. This pattern is consistent with a similar semiannual signal observed in rainfall climatology. The restricted moisture supply to southwestern Saudi Arabia during summer presumably explains the lack of precipitation in other areas of the country. Winter precipitation, however, is widespread. The increased transport of net atmospheric moisture flux is higher during El Niño and positive Indian Ocean dipole (IOD) phenomena. During these events, influx across the Red Sea (west) side of Saudi Arabia increases. The net flux to the region is reduced by a slight increase of outflux across the Persian Gulf (east) side. Reanalysis data and model-sensitivity experiments show that El Niño or a concurrent positive IOD and El Niño event more strongly amplify net transport than does an independent positive IOD event. The partial-lag correlation analysis with net moisture flux from the Red Sea side shows that the positive IOD mode has a peak correlation coefficient of ∼0.5 with close to a 5-month lead and that El Niño has a peak correlation coefficient of ∼0.6 with close to a 2-month lead.

scholarly journals Variability of Summer Precipitation Events Associated with Tropical Cyclones over Mid-Lower Reaches of Yangtze River Basin: Role of the El Niño–Southern Oscillation

Atmosphere ◽  
2019 ◽  
Vol 10 (5) ◽  
pp. 256 ◽  
Author(s):  
Fuqiang Cao ◽  
Tao Gao ◽  
Li Dan ◽  
Lian Xie ◽  
Xiang Gong
Keyword(s):  
River Basin ◽  
El Niño ◽  
Yangtze River ◽  
El Nino ◽  
Southern Oscillation ◽  
Yangtze River Basin ◽  
El Nino Southern Oscillation ◽  
Rainfall Events ◽  
Normal Rainfall ◽  
Precipitation Events

Based on tropical cyclone (TC) track data and gridded observational rainfall data of CN05.1 during the period of 1961 to 2014, we examine the contribution of TCs on three metrics of summertime rainfall regimes and identify the connection between TC-induced precipitation events and El Niño–Southern Oscillation (ENSO) in middle–lower reaches of Yangtze River Basin (MLYRB). At the regional scale, TCs are responsible for approximately 14.4%, 12.5%, and 6.9% of rainfall events for normal, 75th, and 95th percentile precipitation cases, respectively. There is no evidence of significant long-term trends of the three type events linked with TCs, while their interdecadal variability is remarkable. Fractionally, larger proportions of TC-induced events occur along southeast coastal regions of MLYRB for normal rainfall events, and they are recorded over southwest and central-east MLYRB for 95th percentile cases. Moreover, a larger contribution of 95th percentile precipitation events to summer total rainfall is found than that for 75th percentile cases, suggesting that TCs may exert stronger impacts on the upper tail of summertime precipitation distribution across MLYRB. The TC-induced normal rainfall events tend to occur more frequency over central-west MLYRB during negative phase of ENSO in summer. However, the higher likelihood of TC-induced rainfall for three defined metrics are found over the majority of areas over MLYRB during negative ENSO phase in spring. In preceding winter, La Niña episode plays a crucial role in controlling the frequency of both normal and 75th percentile precipitation events.

Northwest Pacific Anticyclonic Anomalies during Post–El Niño Summers Determined by the Pace of El Niño Decay

2019 ◽  
Vol 32 (12) ◽  
pp. 3487-3503 ◽  
Author(s):  
Wenping Jiang ◽  
Gang Huang ◽  
Ping Huang ◽  
Renguang Wu ◽  
Kaiming Hu ◽  
...  
Keyword(s):  
Rossby Wave ◽  
El Niño ◽  
Yangtze River ◽  
El Nino ◽  
Yangtze River Basin ◽  
Northwest Pacific ◽  
The Yangtze River ◽  
Kelvin Wave ◽  
The Yangtze River Basin ◽  
Sst Anomalies

Abstract This study investigates the characteristics and maintaining mechanisms of the anomalous northwest Pacific anticyclone (NWPAC) following different El Niño decaying paces. In fast decaying El Niño summers, the positive SST anomalies in the tropical central-eastern Pacific (TCEP) have transformed to negative, and positive SST anomalies appear around the Maritime Continent (MC), whereas in slow decaying El Niño summers, positive SST anomalies are present in the TCEP and in the tropical Indian Ocean (TIO). During fast decaying El Niño summers, the cold Rossby wave in response to the negative TCEP SST anomalies has a primary contribution to maintaining the NWPAC anomalies. The warm Kelvin wave response and enhanced Hadley circulation anomalies forced by the positive MC SST anomalies also facilitate developing the NWPAC anomalies. During slow decaying El Niño summers, the warm Kelvin wave anchored over the TIO plays a crucial role in sustaining the NWPAC anomalies, while the warm Rossby wave triggered by the positive TCEP SST anomalies weakens the western part of the NWPAC anomalies. The southwesterly anomalies of the NWPAC anomalies during fast decaying El Niño summers can reach to higher latitudes than those during slow decaying El Niño summers. Correspondingly, positive rainfall anomalies appear in northern China and the Yangtze River basin in fast decaying El Niño summers but are only distributed in the Yangtze River basin in slow decaying El Niño summers. This study implies that the El Niño decaying pace is a key factor in East Asian summer climate.

scholarly journals The asymmetric response of Yangtze river basin summer rainfall to El Niño/La Niña

2018 ◽  
Vol 13 (2) ◽  
pp. 024015 ◽  
Author(s):  
Steven C Hardiman ◽  
Nick J Dunstone ◽  
Adam A Scaife ◽  
Philip E Bett ◽  
Chaofan Li ◽  
...  
Keyword(s):  
River Basin ◽  
El Niño ◽  
Yangtze River ◽  
El Nino ◽  
Yangtze River Basin ◽  
Summer Rainfall ◽  
La Niña ◽  
La Nina ◽  
Asymmetric Response

scholarly journals Variation of precipitation concentration from 1960 to 2014 in the Middle and Lower reaches of the Yangtze River Basin, China

2016 ◽  
Vol 42 (1) ◽  
pp. 205 ◽  
Author(s):  
L. Zhao ◽  
J. M. Wang ◽  
Z. Zhao ◽  
J. Fang
Keyword(s):  
River Basin ◽  
El Niño ◽  
Rainy Season ◽  
Yangtze River ◽  
El Nino ◽  
Yangtze River Basin ◽  
Risk Governance ◽  
Positive Trend ◽  
Precipitation Concentration ◽  
The Mean

Based on the daily rainfall data of 127 stations from 1960 to 2014, this study investigated the spatial-temporal variation of PCD (precipitation-concentration degree) and PCP (precipitation-concentration period), and their possible relations with ENSO (El Niño-Southern Oscillation) in the middle and lower reaches of Yangtze River of China. Main results have indicated that, firstly, the mean PCD was generally below 0.5 across the whole study area, with the lower value located in the northeast and south. Besides, there was a positive trend of concentrated precipitation in the west part while negative in the east. Secondly, the mean PCP ranged from May to July and delayed from south to north, along with a trend of advancing rainy season in the central part. In addition, PCD had a positive relation with ONI (Oceanic Niño Index), while PCP negative. El Niño led the rainy season earlier and the precipitation more concentrated. This study could not only shed a light on the understanding of the variation of precipitation pattern, but also provide theoretical support for regional disaster risk governance and water resources management in the middle and lower Yangtze River Basin.

Different responses of Central Asian precipitation to strong and weak El Niño events

2021 ◽  
pp. 1-60
Keyword(s):  
Soil Moisture ◽  
Central Asia ◽  
El Niño ◽  
El Nino ◽  
Moisture Flux ◽  
The Arctic ◽  
Central Asian ◽  
El Niño Events ◽  
Sst Anomalies ◽  
El Nino Events

Abstract The present study investigated impacts of strong and weak El Niño events on Central Asian precipitation variability from El Niño developing years to decaying years. It is found that strong El Niño events persistently enhance Central Asian precipitation from the mature winter to decaying summer. Large warm sea surface temperature (SST) anomalies in the tropical central-eastern Pacific induce anomalous upper-level divergence and updraft over Central Asia through large-scale convergence and divergence in the mature winter and decaying spring. Meanwhile, the associated wind anomalies induce anomalous eastward and northeastward moisture flux from the North Atlantic and Arabian Sea to Central Asia. Both anomalous ascent and moisture flux convergence favor above-normal precipitation over Central Asia in the mature winter and decaying spring. The El Niño events induced Central Asian precipitation anomalies are extended to the decaying summer due to the role of soil moisture. Increased rainfall in winter and spring enhances soil moisture in the following summer, which in turn, contributes to more precipitation in summer through modulating regional evaporation. During weak El Niño events, significant wet anomalies are only seen in the developing autumn, which result from anomalous southeastward moisture flux from the Arctic Ocean, and the abnormal signals are weak in the other seasons. The different responses of Central Asian precipitation to strong and weak El Niño events may be attributed to the difference in intensity of tropical SST anomalies between the two types of events.

scholarly journals CP El Niño and PDO Variability Affect Summer Precipitation over East China

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Wan-Jiao Song ◽  
Qi-Guang Wang
Keyword(s):  
El Niño ◽  
El Nino ◽  
Summer Precipitation ◽  
Western Pacific Subtropical High ◽  
Western Pacific ◽  
Subtropical High ◽  
East China ◽  
Central Pacific ◽  
Cp El Niño ◽  
Precipitation Anomalies

The summer precipitation produced by the East Asian summer monsoon (EASM) is significantly affecting agriculture and socioeconomics. Based on the Precipitation Reconstruction dataset in East China from 1950 to 2017, we investigate the spatiotemporal variations of summer precipitation, influencing environmental factors and their relation with the EASM and the Pacific Decadal Oscillation (PDO) in both central Pacific (CP) El Niño developing and decaying years. Results indicate the following: (1) The evolutions of CP El Niño events modulate the summer precipitation anomalies in East China. In the cool PDO phase, CP El Niño causes enhanced precipitation anomalies in the decaying years but less precipitation anomalies in the developing years, and vice versa for the warm PDO phase. (2) Atmospheric circulation anomalies drive the moisture transportation and combine the motion of western Pacific subtropical high resulting in the variation of precipitation patterns. Anomalous cyclone over the western North Pacific and the sustained Western Pacific Subtropical High (WPSH) are favorable for the increment of summer precipitation. (3) The different CP El Niño-EASM relationship is caused by the influences of PDO on the evolution of CP El Niño. CP El Niño develops slowly (decays rapidly) and is associated with rapidly developing (slowly decaying) anomalous warming in the north Indian Ocean during the developing (decaying) years.

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