The role of large‐scale eddies in the occurrence of winter precipitation deficits in Portugal

Santos, João A.; Andrade, Cristina; Corte‐Real, João; Leite, S. M.

doi:10.1002/joc.1818

Cited by 31 publications

(27 citation statements)

References 41 publications

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“…Furthermore, these patterns suggest that the 2010 precipitation anomalies recorded in Portugal were a result of an uncommon large-scale atmospheric circulation, not being attributable to regional or local effects. This assessment is corroborated by previous studies, where the precipitation regime in Portugal was clearly linked to large-scale atmospheric patterns (Xoplaki et al 2004, Santos et al 2005, 2009b, Andrade et al 2010. The transient-eddy humidity fluxes are also a manifestation of the presence of synoptic disturbances.…”

Section: Meteorological Characterisation Of the 2010 Wintersupporting

confidence: 88%

“…Fig. 2 in Santos et al 2009b). These meteorological data were provided by the European Climate Assessment & Dataset project (Klein Tank et al 2002).…”

Section: Methodsmentioning

confidence: 97%

“…Pereira et al 2002) and also playing a key role in triggering hydrological droughts (e.g. Santos et al 2009b). This precipitation regime thus has a great im-pact on water resource management and on water quality in Portugal, and explains the high vulnerability of the country to wintertime rainfall occurrence and respective amounts.…”

Section: Introductionmentioning

confidence: 99%

“…Most of them analysed winter precipitation and its relationships with the largescale atmospheric circulation (Zorita et al 1992, Ulbrich et al 1999, Goodess & Jones 2002, Santos et al 2009b, Andrade et al 2010. In particular, the occurrence of severe precipitation deficits (and thus droughts) in Portugal was specifically related to the development of strong and persistent anticyclonic ridge episodes over the eastern North Atlantic (Santos et al 2009a).…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Large-scale atmospheric dynamics of the wet winter 2009–2010 and its impact on hydrology in Portugal

Andrade¹,

Santos²,

Pinto³

et al. 2011

Clim. Res.

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The anomalously wet winter of 2010 had a very important impact on the Portuguese hydrological system. Owing to the detrimental effects of reduced precipitation in Portugal on the environmental and socio-economic systems, the 2010 winter was predominantly beneficial by reversing the accumulated precipitation deficits during the previous hydrological years. The recorded anomalously high precipitation amounts have contributed to an overall increase in river runoffs and dam recharges in the 4 major river basins. In synoptic terms, the winter 2010 was characterised by an anomalously strong westerly flow component over the North Atlantic that triggered high precipitation amounts. A dynamically coherent enhancement in the frequencies of mid-latitude cyclones close to Portugal, also accompanied by significant increases in the occurrence of cyclonic, south and southwesterly circulation weather types, are noteworthy. Furthermore, the prevalence of the strong negative phase of the North Atlantic Oscillation (NAO) also emphasises the main dynamical features of the 2010 winter. A comparison of the hydrological and atmospheric conditions between the 2010 winter and the previous 2 anomalously wet winters (1996 and 2001) was also carried out to isolate not only their similarities, but also their contrasting conditions, highlighting the limitations of estimating winter precipitation amounts in Portugal using solely the NAO phase as a predictor.

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Section: Meteorological Characterisation Of the 2010 Wintersupporting

confidence: 88%

“…Fig. 2 in Santos et al 2009b). These meteorological data were provided by the European Climate Assessment & Dataset project (Klein Tank et al 2002).…”

Section: Methodsmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Large-scale atmospheric dynamics of the wet winter 2009–2010 and its impact on hydrology in Portugal

Andrade¹,

Santos²,

Pinto³

et al. 2011

Clim. Res.

View full text Add to dashboard Cite

show abstract

“…However, the identified NAO influence is only a first and rough approximation since other large-scale patterns are also significantly coupled with the winter precipitation in Portugal, e.g. the AO influences (Santos et al, 2009 al. (2010), periodicities of more than 10 years, more frequent in the northern region, are difficult to relate with the NAO.…”

Section: Discussionmentioning

confidence: 99%

Assessing drought cycles in SPI time series using a Fourier analysis

Moreira

Martins

Pereira

2015

Nat. Hazards Earth Syst. Sci.

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Abstract. In this study, drought in Portugal was assessed using 74 time series of Standardized Precipitation Index (SPI) with a 12-month timescale and 66 years length. A clustering analysis on the SPI Principal Components loadings was performed in order to find regions where SPI drought characteristics are similar. A Fourier analysis was then applied to the SPI time series considering one SPI value per year relative to every month. The analysis focused on the December SPI time series grouped in each of the three identified clusters to investigate the existence of cycles that could be related to the return periods of droughts. The most frequent significant cycles in each of the three clusters were identified and analysed for December and the other months. Results for December show that drought periodicities vary among the three clusters, pointing to a 6-year cycle across the country and a 9.4-year cycle in central and southern Portugal. Both these cycles likely show the influence of the North Atlantic Oscillation (NAO) on the occurrence and severity of droughts in Portugal. Relative to other months it was observed that cycles varied according to the common occurrence of precipitation: for the rainy months -November, December and January -cycles are similar to those for December; for the dry months -May to September -where the lack of precipitation masks the occurrence of drought, the dominant cycles are of short duration and cannot be related to the NAO or other large circulation indices to explain drought variability; for the transition months -February, March, April and October -6-year and 3-year cycles were identified, the latter being more strongly apparent in central and southern Portugal. NAO influence is again identified relative to the 6-year cycles. The short cycles are apparently associated with positive SPI, thus with wetness, not drought. Overall, results confirm the importance of the NAO as a driving force for dry and wet periods.

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Understanding climate change projections for precipitation over western Europe with a weather typing approach

et al. 2016

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Precipitation over western Europe (WE) is projected to increase (decrease) roughly northward (equatorward) of 50°N during the 21st century. These changes are generally attributed to alterations in the regional large-scale circulation, e.g., jet stream, cyclone activity, and blocking frequencies. A novel weather typing within the sector (30°W-10°E, 25-70°N) is used for a more comprehensive dynamical interpretation of precipitation changes. A k-means clustering on daily mean sea level pressure was undertaken for ERA-Interim reanalysis . Eight weather types are identified: S1, S2, S3 (summertime types), W1, W2, W3 (wintertime types), B1, and B2 (blocking-like types). Their distinctive dynamical characteristics allow identifying the main large-scale precipitation-driving mechanisms. Simulations with 22 Coupled Model Intercomparison Project 5 models for recent climate conditions show biases in reproducing the observed seasonality of weather types. In particular, an overestimation of weather type frequencies associated with zonal airflow is identified. Considering projections following the (Representative Concentration Pathways) RCP8.5 scenario over 2071-2100, the frequencies of the three driest types (S1, B2, and W3) are projected to increase (mainly S1, +4%) in detriment of the rainiest types, particularly W1 (À3%). These changes explain most of the precipitation projections over WE. However, a weather type-independent background signal is identified (increase/decrease in precipitation over northern/southern WE), suggesting modifications in precipitation-generating processes and/or model inability to accurately simulate these processes. Despite these caveats in the precipitation scenarios for WE, which must be duly taken into account, our approach permits a better understanding of the projected trends for precipitation over WE. (2016), Understanding climate change projections for precipitation over western Europe with a weather typing approach,

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The role of large‐scale eddies in the occurrence of winter precipitation deficits in Portugal

Cited by 31 publications

References 41 publications

Large-scale atmospheric dynamics of the wet winter 2009–2010 and its impact on hydrology in Portugal

Large-scale atmospheric dynamics of the wet winter 2009–2010 and its impact on hydrology in Portugal

Assessing drought cycles in SPI time series using a Fourier analysis

Understanding climate change projections for precipitation over western Europe with a weather typing approach

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