Iberian thermal lows in a changed climate

Hoinka, Klaus-Peter; Gaertner, Miguel Ángel; Castro, Manuel de

doi:10.1002/qj.78

Cited by 10 publications

(7 citation statements)

References 27 publications

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“…Here we show that the combination of these two mechanisms results in the development of a heat low over the Mediterranean area that appears to be the dominant climate response in MSLP over that region. Our results are consistent with Hoinka et al [2007], who noted an intensification of the Iberian heat low in response to greenhouse warming.…”

Section: Discussionsupporting

confidence: 93%

Drier Mediterranean soils due to greenhouse warming bring easterly winds over summertime central Europe

Haarsma¹,

Selten²,

Hurk³

et al. 2009

Geophysical Research Letters

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Western European summers become more continental in simulations for the 21st century. Anomalously large summer warming over the Mediterranean area in concert with drier soils and a reduced surface pressure can explain this change. The warming is enhanced due to soil moisture depletion which limits the cooling of the land surface by evaporation. A large‐scale Mediterranean heat low develops, bringing easterly winds over Central Europe. Statistical analysis for present‐day conditions indicates that the same mechanism operates on intra‐seasonal timescales; dry Mediterranean soils in June are correlated with high temperature and low surface pressure in July‐August. Idealized simulations confirm the relation between the surface warming of the Mediterranean area and the development of a heat low. The development of a heat low in response to dry soils induces a positive feedback: drier Mediterranean soils in summer bring easterly winds over Europe and increase the continental character of Western European summer climate.

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Section: Discussionsupporting

confidence: 93%

Drier Mediterranean soils due to greenhouse warming bring easterly winds over summertime central Europe

Haarsma¹,

Selten²,

Hurk³

et al. 2009

Geophysical Research Letters

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“…However, the spatial resolution of that analysis is too coarse to elucidate finer scale wind flow patterns. Hoinka et al (2009) analyzed relationships between regional scale weather patterns and wildfires in central Portugal, namely the role of the Iberian thermal low (Hoinka and Castro, 2003;Hoinka et al, 2007). They showed that previously to days with extensive area burned, the atmospheric flow above Portugal is from the north, turning to easterly on the severe fire day, and to south-easterly afterwards.…”

Section: Discussionmentioning

confidence: 98%

Identifying geographical patterns of wildfire orientation: A watershed-based analysis

Barros

Pereira

Lund

2012

Forest Ecology and Management

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a b s t r a c tWe searched for geographical patterns in the orientation of wildfires, using watersheds as spatial support for the analysis. An 1975-2005 annual fire atlas of mainland Portugal was used to compute the orientation of fire perimeters and watersheds, using principal component analysis. Circular statistics were employed to test for the existence of a preferred, as opposed to random, mean fire orientation in each watershed, and to search for evidence of orographic channelling of fire by comparing fire orientation and watershed orientation. We also tested for differences in fire orientation patterns under conditions of mild versus severe fire weather. Our findings show that in the 31 year period of the study, 84% of the overall area burned is accounted for by watersheds where fires display preferential orientation. Twelve of 102 watersheds display evidence of alignment between fire and watershed orientation and we found no distinction in fire orientation as response to fire weather. The spatial arrangement of watersheds where fires present similar orientation suggests wind as a major driver of the broader patterns found in this study. Results from this analysis ought to be relevant for supporting the delineation of landscape-scale fuelbreaks.

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“…Three data series were used in the current study: European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis (ERA40) data; fire activity as provided by the Portuguese General Directorate of Forestry Resources (DGRF); and Iberian daily thermal low occurrence based on ERA40 taken from Hoinka et al (2007).…”

Section: Methodsmentioning

confidence: 99%

“…Finally, the series of Iberian thermal low occurrence were taken from Hoinka et al (2007), containing the objectively determined occurrence of the Iberian thermal low based on ERA40 data. The related criteria can be found in Hoinka and Castro (2003).…”

Section: Methodsmentioning

confidence: 99%

Regional-scale weather patterns and wildland fires in central Portugal

Hoinka

Carvalho

Miranda

2009

Int. J. Wildland Fire

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The characteristic evolution of the synoptic- and meso-scale wind, temperature and humidity pattern during wildland fire events in Portugal was determined by lagged covariances for the period 1980 to 2001. The daily burnt area was chosen as the parameter to be correlated with atmospheric fields provided by the European Centre for Medium-Range Weather Forecasts Reanalysis (ERA40) data. The related time series consisted of wildland fires with a daily burnt area of more than 500 ha in central Portugal. Five days in advance of a fire event, a strong positive anomaly existed in the surface pressure and in the 500-hPa geopotential field, both appearing to the west of the Iberian Peninsula and moving towards Brittany until lag zero. In advance of the fire event, the flow above Portugal came from the north, turning to easterlies at lag time zero and finally coming from the south-east during the post-event phase. Surface wind statistics taken at Castelo Branco supported these results. Smoke plumes from wildland fires detected by satellites indicated a similar flow structure, which was quite different to the averaged summertime flow above Portugal. Cross-covariance regression between the Iberian thermal low and burnt area showed that the peak amount of burnt area occurred up to 3 days after the appearance of a thermal low. This suggested that in the pre-phase of a wildland fire, heated air is transported from the peninsula’s centre towards Portugal.

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Iberian thermal lows in a changed climate

Cited by 10 publications

References 27 publications

Drier Mediterranean soils due to greenhouse warming bring easterly winds over summertime central Europe

Drier Mediterranean soils due to greenhouse warming bring easterly winds over summertime central Europe

Identifying geographical patterns of wildfire orientation: A watershed-based analysis

Regional-scale weather patterns and wildland fires in central Portugal

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