Climate Variability and Change of Mediterranean-Type Climates

Seager, Richard; Osborn, Timothy J.; Kushnir, Yochanan; Simpson, Isla R.; Nakamura, Jennifer A.; Liu, Haibo

doi:10.1175/jcli-d-18-0472.1

Cited by 178 publications

(184 citation statements)

References 82 publications

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“…The changes in the mean atmospheric state and circulation in winter are connected to an elevated geopotential height anomaly over the Mediterranean stemming from the driving GCMs. Seager et al (2014Seager et al ( , 2019 suggested a combination of time-mean circulation and specific humidity changes as causes of the Mediterranean winter drying, consistent with our findings.…”

Section: Discussionsupporting

confidence: 91%

“…The situation in winter is different. While some observations support Mediterranean winter drying (Mariotti 2010, Mariotti et al 2015, Seager et al 2019, large-scale circulation changes are poorly understood and models disagree on the projected drying, both in large ensembles (Christensen et al 2013) and our regional simulations ( figure S3). These seasonal differences in the causes of the Mediterranean drying and the different associated uncertainties are relevant for studying the impact of climate change on freshwater resources, as the absolute decrease in precipitation is similar in summer and winter (figure S1).…”

Section: Comparison Of Seasonsmentioning

confidence: 59%

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Causes of future Mediterranean precipitation decline depend on the season

Brogli

Sørland

Kröner

et al. 2019

Environ. Res. Lett.

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Future mean precipitation in the Mediterranean is projected to decrease year-round in response to global warming, threatening to aggravate water stress in the region, which can cause social and economic difficulties. We investigate possible causes of the Mediterranean drying in regional climate simulations. To test the influence of multiple large-scale drivers on the drying, we sequentially add them to the simulations. We find that the causes of the Mediterranean drying depend on the season. The summer drying results from the land-ocean warming contrast, and from lapse-rate and other thermodynamic changes, but only weakly depends on circulation changes. In contrast, to reproduce the simulated Mediterranean winter drying, additional changes in the circulation and atmospheric state have to be represented in the simulations. Since land-ocean contrast, thermodynamic and lapserate changes are more robust in climate simulations than circulation changes, the uncertainty associated with the projected drying should be considered smaller in summer than in winter.

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Section: Discussionsupporting

confidence: 91%

Section: Comparison Of Seasonsmentioning

confidence: 59%

Causes of future Mediterranean precipitation decline depend on the season

Brogli

Sørland

Kröner

et al. 2019

Environ. Res. Lett.

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“…That is why the wind direction in the AI region displays a circular pattern ( Figure 12). The CC region is influenced by a tropical Mediterranean-type climate characterized by wet winters and dry summers [52]. The westerly wind path is located closer to the tropical area in winter than in summer, which means that the path of the extratropical cyclone through California could bring more vapor through the atmospheric river.…”

mentioning

confidence: 99%

Regional Dependence of Atmospheric Responses to Oceanic Eddies in the North Pacific Ocean

Chiang

et al. 2020

Remote Sensing

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Based on sea surface height anomaly (SSHA) from satellite altimeter and microwave radiometer datasets, this study investigates atmospheric responses to oceanic eddies in four subdomains of the North Pacific Ocean with strongest eddy activity: Kuroshio Extension (KE), Subtropical Front (SF), California Coastal Current (CC) and Aleutian Islands (AI). Analyses show that anticyclonic eddies cause sea surface temperature, surface wind speed and precipitation rate to increase in all four subdomains, and vice versa. Through a further examination of the regional dependence of atmospheric responses to oceanic eddies, it is found that the strongest and the weakest surface wind speed responses (in winter and summer) are observed in the KE and AI region, respectively. For precipitation rate, seasonal variation of the atmospheric responses to oceanic eddies is strongest in winter and weakest in summer in the KE, CC and AI regions, but stronger in summer in the SF area. The reasons for such regional dependence and seasonality are the differences in the strength of SST anomalies, the vertical kinetic energy flux and atmospheric instability in the four subdomains. 149 the 90-day high pass-filtered surface EKE averaged from 2002 to 2010 in the North Pacific. The highest 150 EKE occurs in the KE and SF regions [42-43]. In addition, compared with adjacent areas, EKE is also 151 high in the AI and CC regions. The largest EKE in the KE region is primarily caused by the strong 152 horizontal shear and the meandering of the Kuroshio path [42]. The higher EKE in the SF region is 153 predominantly modulated by the baroclinic instability of the background currents [44]. The CC 154 region is characterized by strong eddy activity where the persistent equatorward wind causes coastal 155 upwelling fronts. Instability of these upwelling fronts results in eddy generation. The instability of 156 the coast shelf trapped jet causes the eddy formation in the AI region. One can see that the eddy 157 generation mechanisms are varied in the four subdomains, which could cause a difference in 158 mesoscale air-sea interaction characteristics in the four regions.159 160 Figure 2. 90-day high pass-filtered eddy kinetic energy (EKE; shaded) averaged from January 2002 to 161 December 2010. The black dashed lines delineate the four subdomains in this study.Remote Sens. 2020. 4 of 18 0.05 °C (for anticyclonic eddies), and radii larger than 20 km, are selected. As a result, there are about 138 14677, 19636, 16684 and 12220 cyclonic eddies, and 14469, 22043, 16747 and 13195 anticyclonic eddies 139 in the KE, SF, CC and AI regions, respectively. The matching method is adopted from Ma et al. [24]. 157 generation mechanisms are varied in the four subdomains, which could cause a difference in 158 mesoscale air-sea interaction characteristics in the four regions. Remote Sens. 2020. 5 of 18 Satellite altimetry data provides an opportunity to characterize eddies in terms of their basic 163 parameters such as polarity, lifetime, size, vorticity and moving speed in the ...

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“…California will be especially vulnerable to anticipated climate change (Bedsworth et al, ), with temperatures projected to continue increasing for the rest of the 21st century Southern California (IPCC, ; Overpeck et al, ). Total annual precipitation has increased in since 1901 in the Mediterranean climate region of the North American West Coast (Seager et al, ). Both projections for higher temperatures and precipitation will drive evaporative demand that may shift California's Mediterranean biome itself northward (Seager et al, ).…”

Section: Introductionmentioning

confidence: 99%

Southern California Vegetation, Wildfire, and Erosion Had Nonlinear Responses to Climatic Forcing During Marine Isotope Stages 5–2 (120–15 ka)

Glover

Chaney

Kirby

et al. 2020

Paleoceanog and Paleoclimatol

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A multiproxy record from Baldwin Lake, San Bernardino Mountains, allowed us to examine variation and relationships between erosion, wildfire, vegetation, and climate in subalpine Southern California from 120 to 15 ka. Bulk organics, biogenic silica, and molar C:N data were generally antiphased with magnetic and trace element data and displayed long‐term (105 year) shifts between autochthonous and allocthonous deposition. This was most pronounced during Marine Isotope Stage (MIS) 5, and we hypothesize that local summer insolation was the primary driver for Baldwin Lake's productive and unproductive lake state alternations. Wildfire history was inferred from charcoal concentrations and vegetation change from pollen. Relationships between these ecological processes, basin deposition, and summer insolation were often nonlinear. Sagebrush expansion, wildfire, and weak basin weathering characterized MIS 4, while during MIS 2, the basin was highly erosive, rarely burned, and the forest was impacted by shifts in Southern Californian hydroclimate. Despite coniferous forest cover throughout MIS 3, submillennial oscillations in charcoal, pollen, and bulk organic content occurred, consistent with pollen records from Eurasia's Mediterranean biome that span multiple glacial‐interglacial cycles. Highly resolved global CO2 records and sea surface temperatures in key regions of the Pacific show no apparent relationship to these landscape conditions, and we suggest submillennial hydroclimatic variability as a potential driver. Highly resolved long pollen records from Southern California are an urgent research need to better understand the finer‐scale (≤103 year) interactions between past vegetation, wildfire, and erosion, given the current natural disaster risks that 21st century climate change poses to both human and ecological communities.

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Climate Variability and Change of Mediterranean-Type Climates

Cited by 178 publications

References 82 publications

Causes of future Mediterranean precipitation decline depend on the season

Causes of future Mediterranean precipitation decline depend on the season

Regional Dependence of Atmospheric Responses to Oceanic Eddies in the North Pacific Ocean

Southern California Vegetation, Wildfire, and Erosion Had Nonlinear Responses to Climatic Forcing During Marine Isotope Stages 5–2 (120–15 ka)

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