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Andrew Hoell, Andrea E. Gaughan, Shraddhanand Shukla, and Tamuka Magadzire

1. Introduction Southern Africa precipitation during December–March (DJFM), the height of the rainy season, is closely related with variations of the El Niño–Southern Oscillation (ENSO; e.g., Nicholson and Entekhabi 1986 ; Manatsa et al. 2015 ) and the subtropical Indian Ocean dipole (SIOD; Behera et al. 2000 ; Behera and Yamagata 2001 ; Reason 2001 ; Washington and Preston 2006 ) modes of climate variability. Further, recent research has shown that the combined effects of ENSO and SIOD

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Hanh Nguyen, Jason A. Otkin, Matthew C. Wheeler, Pandora Hope, Blair Trewin, and Christa Pudmenzky

precipitation but have also been linked to higher-than-normal temperatures ( Nicholls 2004 ). The primary modes of climate variability influencing Australian rainfall and temperature on seasonal time scales are the El Niño–Southern Oscillation (ENSO), the Indian Ocean dipole (IOD), and the southern annular mode (SAM) ( Risbey et al. 2009 ). El Niño and a positive IOD generally cause hotter and drier conditions across Australia (e.g., Meyers et al. 2007 ), while the effect of the SAM is seasonally and

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Emily A. Slinskey, Paul C. Loikith, Duane E. Waliser, Bin Guan, and Andrew Martin

causing extensive flooding ( Neiman et al. 2008b ; Rutz et al. 2014 ; Mueller et al. 2017 ). The signal of inland-penetrating ARs over the western United States is evident in the spring and autumn as well ( Figs. 4b,c ). Results show that the largest ARs occur more commonly across the West compared to the East with an extensive portion of the Southwest and Southern Great Plains experiencing ARs with a smaller areal extent (<2 × 10 6 km 2 ) during the summer ( Fig. 4c ). Fig . 4. Median AR area (×10

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Allison B. Marquardt Collow, Haiden Mersiovsky, and Michael G. Bosilovich

south in California where ARs are present in between the Northern Coast and Southern Coast Ranges. As ARs transport large quantities of water vapor across from over the ocean to the land surface, moisture is provided to allow for precipitation to occur. The most extreme precipitation events, in this case, those that exceed the 95th percentile, have the largest impact on society ( Ralph et al. 2013 ). Figure 1c shows the percentage of 95th percentile extreme precipitation events that were

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ZONGJIAN KE, XINGWEN JIANG, JINMING FENG, and ZUNYA WANG

Abstract

In the last two decades, southwestern China (SWC) has experienced severe droughts, which are always accompanied by severe deficiencies in precipitation. In this study, we found that the interannual variability in boreal winter precipitation in SWC is modulated by the Philippine Sea anomalous anticyclone (PSAC). The interannual relationship between the PSAC and SWC precipitation experienced an interdecadal change around the early 1980s. The correlation between them was enhanced in the period from 1981 to 2001 (P2) compared to the period from 1961 to 1980 (P1). In P1, the moisture transported by the PSAC mainly affected eastern China, as the PSAC was located over the northern Philippine Sea, and the moisture budget of SWC was dominated by moisture transport at the western boundary. The PSAC, however, strengthened and shifted southwestward in P2, accompanied by a deepened India-Burma trough. As such, the PSAC transported moist air from the western North Pacific and the Indian Ocean into SWC through its southern boundary. Meanwhile, the stronger PSAC in P2 was accompanied by an upper-level convergence from the western North Pacific to the Bay of Bengal, which induced an upper-level divergence and ascending motion over SWC. Thus, the PSAC caused a significant increase in precipitation in P2. Stronger air-sea interactions in the western North Pacific induced by the El Niño–Southern Oscillation may be responsible for the enhancement and southwestward shift of the PSAC in P2 compared to that in P1.

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Rasool Porhemmat, Heather Purdie, Peyman Zawar-Reza, Christian Zammit, and Tim Kerr

. 2017 ). The analysis of three historic snowstorms during the past 60 years on Mt. Shasta, in California, United States, demonstrated a clear link between large snowfall events and ARs ( Hansen 2016 ). Investigation of climatology of winter precipitation over the subtropical central Andes indicates that strong water vapor transport from the Pacific Ocean largely modulates heavy snowfall events in the region ( Viale and Nuñez 2011 ). In the southern Andes, Saavedra et al. (2020) reported that

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Xianghui Kong, Aihui Wang, Xunqiang Bi, Xingyu Li, and He Zhang

[including global area-weighted average, the root-mean-square error (RMSE) and SCC] are shown in Fig. 8 . MERRA2 and simulated precipitation amounts are larger than CMORPH, especially in parts of the western Pacific Ocean, India Ocean, Atlantic Ocean, and along the southern part of the Tibetan Plateau ( Fig. 8a and Fig. S2 ). Simulated precipitation amount noticeably changes with grid spacing. For the two low-resolution simulations, dry biases are present across the eastern portions of the Indian

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Carolina A. Bieri, Francina Dominguez, and David M. Lawrence

differences ( Fig. 7c ) suggest that there is augmented flow from the humid Amazon region of South America into southern Brazil as well as from the Atlantic Ocean into Uruguay and northern Argentina. Increased moisture transport related to the anomalous cyclonic circulation could explain increased precipitation ( Fig. 7f ) over the southern portion of the box and over the northern part. There are also clear increases to north/northeast of the box. An interesting aspect of these results is the thermal low

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R. Garreaud

Pacific anticyclone, featuring a semiarid climate between extremely dry conditions to the north and more humid conditions to the south (e.g., Fig. 2b ). In the east–west direction, the Andes cordillera—rising over 4000 m MSL—acts as a boundary between the continental climate of central Argentina and the milder, ocean-controlled climate of central Chile (e.g., Garreaud et al. 2009 ). Annual mean precipitation varies from 200 to 700 mm, depending on latitude and altitude, and exhibits significant

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W. M. De Kock, R. C. Blamey, and C. J. C. Reason

. On the other hand, COL numbers per year with LREs range from one to five with only 9 out of 25 summers with LREs having only one COL. Singleton and Reason (2007a) suggested that annual COL numbers over the subtropical southern Africa region and neighboring oceans (10°–40°E, 20°–40°S) were higher during La Niña events but this does not appear to be the case here with only the La Niña summers prior to 1998 tending to show increased COL frequency. On the other hand, there are reduced COL numbers

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