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Drought, Climate Variability, and Implications for Water Supply and Management
Published in Bonnie G. Colby, Katharine L. Jacobs, Arizona Water Policy, 2010
Gregg Garfin, Michael A. Crimmins, Katharine L. Jacobs
Considerable attention recently has been focused on variations at longer time scales, associated with multidecadal variations in the Pacific and Atlantic Oceans. The Pacific decadal oscillation (PDO) is characterized by persistent ENSO-like ocean temperature patterns that are pronounced in the North Pacific Ocean (Mantua and Hare 2002). Multidecade regimes of sustained warm and cool PDO behavior are associated with winter half-year precipitation variations in the western United States, including below-average winter precipitation and episodes of sustained drought in the Southwest, as seen during the 1950s, and above average precipitation, such as the post-1976 wet period. The physical mechanisms behind the PDO are not currently known, and explanations range from complex North Pacific Ocean–atmosphere dynamics to delays in the emergence of ENSO-related tropical ocean perturbations in the northern oceans. Even in the absence of a precise understanding of the mechanisms governing PDO, statistical associations between PDO and Arizona climate yield insights into past episodes of sustained drought and their influence on water resources.
Hydrological Modeling to Assess Runoff in a Semi-arid Andean Headwater Catchment for Water Management in Central Chile
Published in Diego A. Rivera, Alex Godoy-Faundez, Mario Lillo-Saavedra, Andean Hydrology, 2018
S. Penedo-Julien, A. Nauditt, A. Künne, M. Souvignet, P. Krause
The UHB is located within the Coquimbo region and has a drainage area of 670 km2 (see Fig. 10.66). The elevation varies from 2,000 to 5,500 m a.s.l. with a mean elevation of 3,724. According to the Köppen-Geiger classification the UHB belongs to the Bsk subgroup which is characterized by a long dry season (7-10 months) and that precipitation is less than potential evapotranspiration (Souvignet, 2010). The regional climate is driven by three main factors: (i) the southeast Pacific anticyclone, (ii) the cold Humboldt Current along the Pacific coast, (ii) the mountain range of the Andes (Oyarzún et al., 2003). Precipitation and temperature patterns follow an E-W axis driven by changes in altitude. Mean annual precipitation, including snowfall, for the period 1979-2006 measured at Hurtado was 147 mm concentrating in the winter months of June and July. The dry season goes from September until April. Precipitation is strongly influenced by orography, El Niño Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) contributing to a high inter- and intra-annual variability (Souvignet, 2010; Núñez et al., 2013). For instance, ENSO events can multiply annual precipitation by a factor of 2–3 (Oyarzún et al., 2003). Moreover, local basin features such as valley orientation, hill slope exposure, abrupt elevation changes result in relevant, small-scale variability in precipitation and snow accumulation spatial patterns (Favier et al., 2009). Mean annual temperature, also measured at Hurtado for the same period, was 17°C reaching its minimum in July (13°C), coinciding with the precipitation maximum, while the maximum temperature was reached in February (21°C).
Meteorological Drought Indices: Rainfall Prediction in Argentina
Published in Saeid Eslamian, Faezeh Eslamian, Handbook of Drought and Water Scarcity, 2017
Marcela H. González, Eugenia M. Garbarini, Alfredo L. Rolla, Saeid Eslamian
The Pacific Decadal Oscillation (PDO) is a long-lived El Niño–like pattern of Pacific Ocean variability. The PDO Index (in °C) is defined as the leading principal component of monthly SST anomalies in the North Pacific Ocean, poleward of 20°N. The monthly mean global average SST anomalies are removed to separate this pattern of variability from any “global warming” signal that may be present in the data. The periodicity of the PDO is about 15–25 years and 50–70 years, and the major signals are found in North Pacific and American sectors. However, there is evidence that the PDO positive (negative) phase is related to a stronger ENSO warm (cold) phase [40,41,74]. A cold phase of PDO was observed in 1947–1976; a warm phase prevailed in 1925–1946 and 1977–1995. The cause of these anomalies is not fully understood yet and the potential predictability of the PDO is studied and monitored all over the world. PDO data used in this study were obtained from the University of Washington [79]. The interannual variability of Atlantic Ocean’s SST is an important feature to be considered. The Atlantic Multidecadal Oscillation (AMO, in °C) is a mode of variability of the SST in the North Atlantic Ocean that Schlesinger [62] first defined. The periodicity of this oscillation is 60–80 years [65]. The AMO index [64] is defined as the difference between SST in two different regions: AMO=SSTa−SSTb where Region a: 0°–60°N, 0°–80°WRegion b: 60°S–60°N
Twentieth-century Pacific Decadal Oscillation simulated by CMIP5 coupled models
Published in Atmospheric and Oceanic Science Letters, 2018
The Pacific Decadal Oscillation (PDO) is one of the most important modes of decadal climate variability (Mantua et al. 1997; Mantua and Hare 2002), whose index is defined as the leading principal component of SST anomalies in the Pacific basin, poleward of 20°N. Based on the last 100 years of observations, the spatial pattern of the PDO shows a characteristic ‘horseshoe’ shape in the North Pacific. During a positive PDO phase, anomalously cool SSTs are observed in the Kuroshio–Oyashio extension and central North Pacific, surrounded by anomalously warm SSTs along the west coast of the Americas that extend towards the tropics (Figure 1, observation). The spatial pattern is reversed during a negative PDO phase.
Variations of rapidly intensifying tropical cyclones and their landfalls in the Western North Pacific
Published in Coastal Engineering Journal, 2021
The changes in frequency and intensity of TC activities were studied extensively based on historical records as well as future climate change scenarios (Elsner, Kossin, and Jagger 2008; Emanuel 2005; Knutson et al. 2010; Mei and Xie 2016; Webster et al. 2005). For example, increasing intensities of strong (Category 4 and 5 on the Saffir–Simpson Scale) or the strongest TCs were reported by both Webster et al. (2005; worldwide) and Elsner, Kossin, and Jagger (2008; Atlantic basin). In the western North Pacific (WNP), a significant increase of the ratio of RI TCs was reported in recent decades, resulting from decreasing TC numbers (Fudeyasu, Ito, and Miyamoto 2018; Zhao et al. 2018); the magnitude of RI also exhibits a strengthening tendency because of significantly increased strong RI events (Song, Duan, and Klotzbach 2020). As RI was generally suggested to share common environmental conditions with TC formation (Wang and Zhou 2008; Klotzbach 2012; Shu, Ming, and Chi 2012; Wang et al. 2015), the large-scale environmental factors and their variation induced by climate change were regarded as underlying mechanisms. The affecting factors may differ upon basins. The oceanic thermodynamic was regarded likely to play a more important role on RI formation in the WNP, where not only the warm sea surface temperature (SST) but thick upper layer containing high tropical cyclone heat potential (TCHP) are crucial factors for supporting RI occurrence (Zhao et al. 2018; Guo and Tan 2018; Song, Duan, and Klotzbach 2020). Ting et al. (2019) explained how climate warming induced a decrease in vertical wind shear (VWS), one of the atmospheric factors, played the important role in strengthening TC intensity along the U.S. East coast, through eroding the barrier of high VWS. Meanwhile, the climate patterns, e.g. the El Niño-Southern Oscillation (ENSO) or the Pacific decadal oscillation (PDO), affected the large-scale environment which can attribute to variability of RI activities on various timescales (Mei et al. 2015; Wang et al. 2015; Zhao et al. 2018; Guo and Tan 2018).