scholarly journals Weaker connection between the Atlantic Multidecadal Oscillation and Indian summer rainfall since the mid-1990s

2017 ◽  
Vol 11 (1) ◽  
pp. 37-43 ◽  
Author(s):  
Fei-Fei LUO ◽  
Shuanglin LI ◽  
Tore FUREVIK
2008 ◽  
Vol 21 (11) ◽  
pp. 2371-2383 ◽  
Author(s):  
Qi Hu ◽  
Song Feng

Abstract The North American summer monsoon holds the key to understanding warm season rainfall variations in the region from northern Mexico to the Southwest and the central United States. Studies of the monsoon have pictured mosaic submonsoonal regions and different processes influencing monsoon variations. Among the influencing processes is the “land memory,” showing primarily the influence of the antecedent winter season precipitation (snow) anomalies in the Northwest on summer rainfall anomalies in the Southwest. More intriguingly, the land memory has been found to vary at the multidecadal time scale. This memory change may actually reflect multidecadal variations of the atmospheric circulation in the North American monsoon region. This notion is examined in this study by first establishing the North American monsoon regimes from relationships of summer rainfall variations in central and western North America, and then quantifying their variations at the multidecadal scale in the twentieth century. Results of these analyses show two monsoon regimes: one featured with consistent variations in summer rainfall in west Mexico and the Southwest and an opposite variation pattern in the central United States, and the other with consistent rainfall variations in west Mexico and the central United States but different from the variations in the southwest United States. These regimes have alternated at multidecadal scales in the twentieth century. This alternation of the regimes is found to be in phase with the North Atlantic Multidecadal Oscillation (AMO). In warm and cold phases of the AMO, distinctive circulation anomalies are found in central and western North America, where lower than average pressure prevailed in the warm phase and the opposite anomaly in the cold phase. Associated wind anomalies configured different patterns for moisture transport and may have contributed to the development and variation of the monsoon regimes. These results indicate that investigations of the effects of AMO and its interaction with the North Pacific circulations could lead to a better understanding of the North American monsoon variations.


2013 ◽  
Vol 14 (6) ◽  
pp. 1944-1951 ◽  
Author(s):  
Susan Stillman ◽  
Xubin Zeng ◽  
William J. Shuttleworth ◽  
David C. Goodrich ◽  
Carl L. Unkrich ◽  
...  

Abstract The Walnut Gulch Experimental Watershed (WGEW) in southeastern Arizona covers ~150 km2 and receives the majority of its annual precipitation from highly variable and intermittent summer storms during the North American monsoon. In this study, the patterns of precipitation in the U.S. Department of Agriculture–Agricultural Research Service (USDA-ARS) 88-rain-gauge network are analyzed for July through September from 1956 to 2011. Because small-scale convective systems generate most of this summer rainfall, the total (T), intensity (I), and frequency (F) exhibit high spatial and temporal variability. Although subsidiary periods may have apparent trends, no significant trends in T, I, and F were found for the study period as a whole. Observed trends in the spatial coverage of storms change sign in the late 1970s, and the multidecadal variation in I and spatial coverage of storms have statistically significant correlation with the Pacific decadal oscillation and the Atlantic multidecadal oscillation indices. Precipitation has a pronounced diurnal cycle with the highest T and F occurring between 1500 and 2200 LT, and its average fractional coverage over 2- and 12-h periods is less than 40% and 60% of the gauges, respectively. Although more gauges are needed to estimate area-averaged daily precipitation, 5–11 gauges can provide a reasonable estimate of the area-averaged monthly total precipitation during the period from July through September.


2017 ◽  
Vol 30 (20) ◽  
pp. 8299-8316 ◽  
Author(s):  
Dong Si ◽  
Aixue Hu

Abstract Interdecadal oceanic variabilities can be generated from both internal and external processes, and these variabilities can significantly modulate climate on global and regional scales, including the warming slowdown in the early twenty-first century and rainfall in East Asia. By analyzing simulations from a unique Community Earth System Model (CESM) Large Ensemble (CESM-LE) project, it is shown that the interdecadal Pacific oscillation (IPO) is primarily an internally generated oceanic variability, while the Atlantic multidecadal oscillation (AMO) may be an oceanic variability generated by internal oceanic processes and modulated by external forcing in the twentieth century. Although the observed relationship between IPO and the Yangtze–Huaihe River valley (YHRV) summer rainfall in China is well simulated in both the preindustrial control and the twentieth-century ensemble simulation, none of the twentieth-century ensemble members can reproduce the observed time evolution of both the IPO and YHRV rainfall because of the unpredictable nature of IPO on multidecadal time scales. On the other hand, although CESM-LE cannot reproduce the observed relationship between the AMO and Huanghe River valley (HRV) summer rainfall of China in the preindustrial control simulation, this relationship in the twentieth-century simulations is well reproduced, and the chance of reproducing the observed time evolution of both AMO and HRV rainfall is about 30%, indicating the important role of the interaction between the internal processes and the external forcing to realistically simulate the AMO and HRV rainfall.


2020 ◽  
Vol 650 ◽  
pp. 269-287
Author(s):  
WC Thaxton ◽  
JC Taylor ◽  
RG Asch

As the effects of climate change become more pronounced, variation in the direction and magnitude of shifts in species occurrence in space and time may disrupt interspecific interactions in ecological communities. In this study, we examined how the fall and winter ichthyoplankton community in the Newport River Estuary located inshore of Pamlico Sound in the southeastern United States has responded to environmental variability over the last 27 yr. We relate the timing of estuarine ingress of 10 larval fish species to changes in sea surface temperature (SST), the Atlantic Multidecadal Oscillation, the North Atlantic Oscillation, wind strength and phenology, and tidal height. We also examined whether any species exhibited trends in ingress phenology over the last 3 decades. Species varied in the magnitude of their responses to all of the environmental variables studied, but most shared a common direction of change. SST and northerly wind strength had the largest impact on estuarine ingress phenology, with most species ingressing earlier during warm years and delaying ingress during years with strong northerly winds. As SST warms in the coming decades, the average date of ingress of some species (Atlantic croaker Micropogonias undulatus, summer flounder Paralichthys dentatus, pinfish Lagodon rhomboides) is projected to advance on the order of weeks to months, assuming temperatures do not exceed a threshold at which species can no longer respond through changes in phenology. These shifts in ingress could affect larval survival and growth since environmental conditions in the estuarine and pelagic nursery habitats of fishes also vary seasonally.


2021 ◽  
Author(s):  
Yubo Liu ◽  
Chi Zhang ◽  
Qiuhong Tang ◽  
Seyed-Mohammad Hosseini-Moghari ◽  
Gebremedhin Gebremeskel Haile ◽  
...  

2021 ◽  
pp. 105792
Author(s):  
Wenhua Gao ◽  
Lulin Xue ◽  
Liping Liu ◽  
Chunsong Lu ◽  
Yuxing Yun ◽  
...  

2012 ◽  
Vol 39 (9) ◽  
pp. n/a-n/a ◽  
Author(s):  
Petr Chylek ◽  
Chris Folland ◽  
Leela Frankcombe ◽  
Henk Dijkstra ◽  
Glen Lesins ◽  
...  

1976 ◽  
Vol 87 (1) ◽  
pp. 163-170 ◽  
Author(s):  
P. Needham ◽  
D. A. Boyd

SummarySeventeen experiments with spring barley testing seven amounts of nitrogen were made on commercial farms in Somerset, Devon and Cornwall between 1965 and 1968. Crop measurements and determinable site factors were only partially successful in accounting for differences between sites and between years in optimal N and efficiency of N use below optimum.The actual optima were found to differ considerably from predicted N requirements based on past cropping and summer rainfall.


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