scholarly journals The role of land and ocean evaporation on the variability of precipitation in the Yangtze River valley

2019 ◽  
Vol 23 (6) ◽  
pp. 2525-2540 ◽  
Author(s):  
Astrid Fremme ◽  
Harald Sodemann
Keyword(s):  
Yangtze River ◽  
Asian Monsoon ◽  
East Asian Monsoon ◽  
East Asian ◽  
Precipitation Variability ◽  
Yangtze River Valley ◽  
The Yangtze River ◽  
Moisture Source ◽  
Moisture Sources

Abstract. The Yangtze River valley (YRV) experiences large intraseasonal and interannual precipitation variability, which is mainly due to East Asian monsoon influence. The East Asian monsoon is caused by interaction of many processes in the coupled land–atmosphere–ocean system. To better understand YRV precipitation variability in this complex system, we have studied the precipitation moisture sources and their connection to YRV precipitation. We obtained the moisture sources by using the European Centre for Medium-Range Weather Forecasts' (ECMWF) ERA-Interim reanalysis dataset, the FLEXible PARTicle dispersion model (FLEXPART), and the WaterSip moisture source diagnostic. The variability of moisture sources reflects the variability of YRV precipitation. Intraseasonal variations of moisture sources include a shift of the most important source regions as the monsoon progresses. Interannual variability of the moisture sources shows that sources which are less important climatologically are closely connected to variations of the driest and wettest years. Our results show that land directly contributes 58 % of moisture for YRV precipitation during 1980–2016, whereas the ocean contributes 42 % in direct transport. While the importance of the ocean as a moisture source is often emphasized, our results underscore the importance of the process of continental recycling and the role of land moisture sources.

scholarly journals The influence of wind and land evapotranspiration on the variability of moisture sources and precipitation of the Yangtze River Valley

2019 ◽  
Author(s):  
Astrid Fremme ◽  
Harald Sodemann
Keyword(s):  
Yangtze River ◽  
Asian Monsoon ◽  
East Asian Monsoon ◽  
East Asian ◽  
Precipitation Variability ◽  
Yangtze River Valley ◽  
River Valley ◽  
The Yangtze River ◽  
Moisture Source ◽  
Moisture Sources

Abstract. The Yangtze River Valley (YRV) experiences large intraseasonal and interannual precipitation variability, which is mainly due to East Asian monsoon influence. The East Asian monsoon is caused by interaction of many processes in the coupled land-atmosphere-ocean system. To better understand YRV precipitation variability in this complex system, we have studied the precipitation moisture sources and their connection to YRV precipitation. We obtained the moisture sources by using the ECMWF's ERA Interim reanalysis data set, the FLEXible PARTicle dispersion model (FLEXPART) and the WaterSip moisture source diagnostic. The variability of moisture sources reflects the variability of YRV precipitation. Intraseasonal variations of moisture sources include a shift of the most important source regions as the monsoon progresses. Interannual variability of the moisture sources shows that sources which are less important climatologically are closely connected to variations of the driest and wettest years. Our results show that land directly contributes 58 % of moisture for YRV precipitation during 1980–2016, whereas the ocean contributes 42 % in direct transport. While the importance of the ocean as a moisture source is often emphasized, our results underscore the importance of the process of continental recycling and the role of land moisture sources.

scholarly journals East Asian monsoon during the past 10,000 years recorded by grain size of Yangtze River delta

2021 ◽  
Vol 13 (1) ◽  
pp. 505-516
Author(s):  
Xiaohui Wang ◽  
Longsheng Wang ◽  
Shouyun Hu ◽  
Ge Yu ◽  
Qing Wang ◽  
...  
Keyword(s):  
Grain Size ◽  
Yangtze River ◽  
Asian Monsoon ◽  
Environmental Changes ◽  
East Asian Monsoon ◽  
East Asian ◽  
Yangtze River Delta ◽  
River Delta ◽  
The Yangtze River ◽  
The Yangtze River Delta

Abstract Paleoenvironmental research is critical for understanding delta evolution processes and managing delta sustainability, particularly for delta experiencing significant recent fluvial sediment discharge. Based on other previously reported optically stimulated luminescence (OSL) data, Holocene environmental changes of the Yangtze River delta in response to climate fluctuations and human activities were reviewed on the basis of grain-size analyses of core YZ07. The results of grain-size and end-member analysis (EMA) provide a detailed history of East Asian monsoon variability and environmental changes since ∼10,000 cal year B.P. The lower median values (Md) and sand content reflect relatively cool and dry climate conditions between 10,000 and 9,570 cal year B.P. During the early Holocene (9,570–7,630 cal year B.P.), the highest Md values and sand contents and the lowest end member 2 (EM2) contents suggest the Holocene transgression. The increased Md values and sand contents indicate that the climate conditions were warm and wet during the mid-Holocene thermal optimum. From 4,690 to 4,150 cal year B.P., the climate was cool and dry, corresponding to the cool event, as indicated by the finer grain size. Subsequently, between 4,150 and 2,850 cal year B.P., the grain size derived from the Md value and sand content increased, which reflect a wet and warm episode. The climate, which shifted from warm and wet to cool and dry between 2,850 and 1,020 cal year B.P., may have caused a reduction in the sand contents and Md values. After 1,020 cal year B.P., the lowest values of Md and Standard deviation (Sd) and the highest contents of EM2 and clay suggest that the Yangtze River delta has been severely affected by anthropogenic activity. The variability of the East Asian monsoon intensity in the Yangtze River delta strongly correlates with other East Asian monsoon paleoclimate records in China. These results are important for investigations into the interactions between regional systems and global change in monsoonal climatic regions and can provide an example of the evolution of a large scale geomorphic feature resulting from river-sea interaction.

Effect of the East Asian Westerly Jet’s Intensity on Summer Rainfall in the Yangtze River Valley and Its Mechanism

2016 ◽  
Vol 29 (7) ◽  
pp. 2395-2406 ◽  
Author(s):  
Shixin Wang ◽  
Hongchao Zuo
Keyword(s):  
Yangtze River ◽  
Interannual Variation ◽  
East Asian ◽  
Summer Rainfall ◽  
Early Summer ◽  
Yangtze River Valley ◽  
River Valley ◽  
The Yellow Sea ◽  
The Yangtze River ◽  
Warm Advection

Abstract Many studies have shown that the northward (southward) displacement of the East Asian westerly jet (EAWJ) drastically reduces (increases) summer rainfall in the Yangtze River valley (YRV). However, the effect of the jet’s intensity on interannual variation in summer rainfall has not been systematically studied. The present study investigates the effect of the EAWJ’s intensity on this interannual variation and analyzes the mechanism by which this process occurs. In early summer, the EAWJ consists of two branches: one located over northern continental East Asia [western branch (EAWJWB)] and one extending from southern China to the northern Pacific [eastern branch (EAWJEB)]. The former merges into the latter over the Yellow Sea. A stronger EAWJEB leads to increased rainfall in the YRV, while the EAWJWB does not significantly affect rainfall in the YRV. The faster EAWJEB directly strengthens midtropospheric warm advection over the YRV because the corresponding changes in the meridional wind and horizontal temperature gradient are insignificant. The strengthened warm advection increases rainfall in the YRV by accelerating both adiabatic ascent and the ascent associated with diabatic heating primarily generated by convection. In midsummer, the EAWJ has no branches and is located over the midlatitudes of Asia. The strengthening of the EAWJ reduces rainfall in the YRV in midsummer through the Pacific–Japan (PJ) pattern. As the EAWJ strengthens, the PJ pattern turns to its positive phase. This results in the deceleration of the midtropospheric westerly wind and a reduction in the meridional temperature contrast, which weakens midtropospheric warm advection. The weakened warm advection in turn reduces rainfall in the YRV, following the process outlined for early summer.

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