Decadal predictability of late winter precipitation in western Europe through an ocean–jet stream connection

The European climate during the Holocene period is characterised by frequent changes of temperature and precipitation. The North Atlantic plays a major role as a driver for European climate and is a dominant precipitation source, particularly for the western European and north African realm. Atmospheric pressure gradients over the Atlantic (North Atlantic Oscillation, NAO), Atlantic circulation patterns (Atlantic Multidecadal Oscillation, AMO) or positioning of the Atlantic jet stream have been suggested to be responsible for precipitation patterns across western Europe. However, proxy data provide an inconsistent picture on how precipitation responds to changes in the Atlantic realm such as changes of Atlantic temperature (IRD), atmospheric pressure (NAO), water circulation (AMO) or the jet stream. Here we present a record of speleothem-based winter precipitation amount from Portugal. The record covers most of the Holocene and demonstrates that wetter conditions were synchronous in western and southern Iberia during early and mid Holocene. The record also shows a correlation between increased winter precipitation amount in western Iberia and Atlantic cooling, evidenced by Bond events, between 10 and 4 ka.

Download Full-text

Impact of jet stream and associated mechanisms on winter precipitation in Pakistan

Meteorology and Atmospheric Physics ◽

10.1007/s00703-019-00683-8 ◽

2019 ◽

Vol 132 (2) ◽

pp. 225-238 ◽

Cited By ~ 3

Author(s):

Fayyaz Ahmed ◽

Shahzada Adnan ◽

Muhammad Latif

Keyword(s):

Winter Precipitation ◽

Jet Stream

Download Full-text

Modeled and Observed Multidecadal Variability in the North Atlantic Jet Stream and Its Connection to Sea Surface Temperatures

Journal of Climate ◽

10.1175/jcli-d-18-0168.1 ◽

2018 ◽

Vol 31 (20) ◽

pp. 8313-8338 ◽

Cited By ~ 16

Author(s):

Isla R. Simpson ◽

Clara Deser ◽

Karen A. McKinnon ◽

Elizabeth A. Barnes

Keyword(s):

North Atlantic ◽

Sea Surface ◽

Late Winter ◽

Jet Stream ◽

Sea Surface Temperatures ◽

Multidecadal Variability ◽

The North ◽

Surface Temperatures ◽

The North Atlantic ◽

North Atlantic Jet

Multidecadal variability in the North Atlantic jet stream in general circulation models (GCMs) is compared with that in reanalysis products of the twentieth century. It is found that almost all models exhibit multidecadal jet stream variability that is entirely consistent with the sampling of white noise year-to-year atmospheric fluctuations. In the observed record, the variability displays a pronounced seasonality within the winter months, with greatly enhanced variability toward the late winter. This late winter variability exceeds that found in any GCM and greatly exceeds expectations from the sampling of atmospheric noise, motivating the need for an underlying explanation. The potential roles of both external forcings and internal coupled ocean–atmosphere processes are considered. While the late winter variability is not found to be closely connected with external forcing, it is found to be strongly related to the internally generated component of Atlantic multidecadal variability (AMV) in sea surface temperatures (SSTs). In fact, consideration of the seasonality of the jet stream variability within the winter months reveals that the AMV is far more strongly connected to jet stream variability during March than the early winter months or the winter season as a whole. Reasoning is put forward for why this connection likely represents a driving of the jet stream variability by the SSTs, although the dynamics involved remain to be understood. This analysis reveals a fundamental mismatch between late winter jet stream variability in observations and GCMs and a potential source of long-term predictability of the late winter Atlantic atmospheric circulation.

Download Full-text

Propagating Atmospheric Patterns Associated with Midwest Winter Precipitation

Journal of Hydrometeorology ◽

10.1175/jhm-d-11-0111.1 ◽

2012 ◽

Vol 13 (4) ◽

pp. 1371-1382 ◽

Cited By ~ 7

Author(s):

Courtenay Strong ◽

Jessica Liptak

Keyword(s):

Wind Speed ◽

Daily Precipitation ◽

Winter Precipitation ◽

Precipitation Variability ◽

Jet Stream ◽

Study Region ◽

Lake Effect ◽

The Pacific ◽

High Precipitation ◽

Transport Patterns

Abstract For winters over eastern North America, complex Hilbert empirical orthogonal function (HEOF) analysis was used to objectively identify propagating patterns in four atmospheric fields that have potential relevance to precipitation: jet stream–level wind speed, 850-hPa moisture transport (qv), temperature advection (TA), and vorticity advection (VA). A novel phase shift method was used to show the location where each propagating pattern was most correlated with Midwest precipitation, and each of the four phase-shifted HEOF patterns was compared to its respective high-precipitation composite view. The leading HEOFs of the three transport fields (qv, TA, and VA), which collectively represented the dynamics associated with a midlatitude cyclone, accounted for almost half of Midwest precipitation variability and were associated with lake effect snow when propagating downstream from the Midwest. Correlation and spectral analyses revealed how the propagating transport patterns were related to the Pacific–North American pattern and other teleconnections. The leading HEOF of jet stream–level wind speed, which represented the tendency for the jet stream to migrate equatorward over the study region during winter, accounted for only about 4% of Midwest daily precipitation variability. In contrast, the second HEOF of jet stream–level wind speed, which represented an eastward propagating trough dynamically consistent with a midlatitude cyclone, accounted for 16% of Midwest daily precipitation variability.

Download Full-text

Predictive skill of atmospheric rivers in the Iberian Peninsula

10.5194/egusphere-egu2020-7354 ◽

2020 ◽

Author(s):

Alexandre M. Ramos ◽

Pedro M. Sousa ◽

Emanuel Dutra ◽

Ricardo M. Trigo

Keyword(s):

Iberian Peninsula ◽

Extreme Precipitation ◽

Western Europe ◽

North Atlantic Ocean ◽

Forecast Accuracy ◽

Strong Relationship ◽

Winter Precipitation ◽

Lead Times ◽

Atmospheric Rivers ◽

Predictive Skill

In recent years a strong relationship has been found between Atmospheric Rivers (ARs) and extreme precipitation and floods across western Europe, with some regions having 8 of their top 10 annual maxima precipitation events related to ARs. In the case of the Iberian Peninsula, the association between ARs and extreme precipitation days has also been well documented, particularly for western Iberia river basins.Since ARs are often associated with high impact weather, it is important to study their medium-range predictability. Here we perform such an assessment using the ECMWF ensemble forecasts up to 15 days, for events that made landfall in western Iberian Peninsula during the winters spanning between 2012/2013 and 2015/16. IVT and precipitation from the 51 ensemble members of the ECMWF Integrated Forecasting System (IFS) ensemble (ENS) were processed over a domain including western Europe and contiguous North Atlantic Ocean.Metrics concerning the ARs location, intensity and orientation were computed, in order to compare the predictive skill (for different prediction lead times) of IVT and precipitation analyses in the IFS. We considered several regional boxes over Western Iberia, where the presence of ARs is detected in analysis/forecasts, enabling the construction of contingency tables and probabilistic evaluation for further objective verification of forecast accuracy. Our results indicate that the ENS forecasts have skill to detect upcoming ARs events, which can be particularly useful to improve the prediction of associated hydrometeorological extremes. We also characterized how the ENS dispersion and confidence curves change with increasing forecast lead times for each sub-domain. We employed the standard ROC analysis to evaluate the probabilistic component of these predictions showing that for short lead times precipitation forecasts are more accurate than IVT forecasts, while for longer lead times this result is reversed (~10 days). Furthermore, we show that this reversal occurs at shorter lead times in areas where the ARs contribution is more relevant for winter precipitation totals (e.g. northwestern Iberia).&#160;AcknowledgementsThe work done was supported by the project&#160;Landslide Early Warning soft technology prototype to improve community resilience and adaptation to environmental change (BeSafeSlide) funded by Funda&#231;&#227;o para a Ci&#234;ncia e a Tecnologia, Portugal (FCT, PTDC/GES-AMB/30052/2017). A.M.R. was also supported by the Scientific Employment Stimulus 2017 from FCT (CEECIND/00027/2017).

Download Full-text

EFFECTS OF RUN-OFF PREVENTION AND LEACHING WATER ON A SALINE SOIL

Canadian Journal of Soil Science ◽

10.4141/cjss61-027 ◽

1961 ◽

Vol 41 (2) ◽

pp. 207-217 ◽

Cited By ~ 4

Author(s):

Fred M. Sandoval ◽

C. W. Carlson ◽

R. H. Mickelson ◽

Leo Benz

Keyword(s):

Saline Soil ◽

Correlation Coefficients ◽

Winter Precipitation ◽

Red River ◽

Late Winter ◽

Applied Water ◽

Red River Valley ◽

Run Off ◽

Summer Rain ◽

Yearly Precipitation

A 4-year study was conducted on the effects of precipitation management on salt movement and spring wheat yields on an imperfectly drained saline silt loam in the northern Red River Valley of North Dakota. Partial leaching by artificially applied water at the beginning of the experiment was compared to leaching benefits by impounded precipitation. Average monthly water table fluctuated from 2 to 11 feet with rainfall and was usually lowest in late winter or spring and highest during the summer. Average yearly precipitation is 20 inches.Impounded precipitation was found effective in partially desalinizing the soil. Summer rain was more effective than winter precipitation. Wheat yields were inversely related to soil salinity with the highest correlation coefficients occurring on springtime data for the 6- to 16-inch depth.

Download Full-text

The Large-Scale Displacement of Subtropical Jet Stream over Western Europe in Winter

Journal of the Meteorological Society of Japan Ser II ◽

10.2151/jmsj1965.51.2_146 ◽

1973 ◽

Vol 51 (2) ◽

pp. 146-150 ◽

Cited By ~ 1

Author(s):

M. Fujii

Keyword(s):

Large Scale ◽

Western Europe ◽

Jet Stream ◽

Subtropical Jet Stream ◽

Subtropical Jet

Download Full-text

The European 2016/17 Drought

Journal of Climate ◽

10.1175/jcli-d-18-0331.1 ◽

2019 ◽

Vol 32 (11) ◽

pp. 3169-3187 ◽

Cited By ~ 24

Author(s):

Ricardo García-Herrera ◽

Jose M. Garrido-Perez ◽

David Barriopedro ◽

Carlos Ordóñez ◽

Sergio M. Vicente-Serrano ◽

...

Keyword(s):

Forest Fires ◽

Western Europe ◽

Sunshine Duration ◽

Jet Stream ◽

Hydroelectric Power ◽

European Regions ◽

Evaporative Demand ◽

Continental Scale ◽

Flow Circulation ◽

Thermodynamic Processes

Abstract We have analyzed the record-breaking drought that affected western and central Europe from July 2016 to June 2017. It caused widespread impacts on water supplies, agriculture, and hydroelectric power production, and was associated with forest fires in Iberia. Unlike common continental-scale droughts, this event displayed a highly unusual spatial pattern affecting both northern and southern European regions. Drought conditions were observed over 90% of central-western Europe, hitting record-breaking values (with respect to 1979–2017) in 25% of the area. Therefore, the event can be considered as the most severe European drought at the continental scale since at least 1979. The main dynamical forcing of the drought was the consecutive occurrence of blocking and subtropical ridges, sometimes displaced from their typical locations. This led to latitudinal shifts of the jet stream and record-breaking positive geopotential height anomalies over most of the continent. The reduction in moisture transport from the Atlantic was relevant in the northern part of the region, where decreased precipitation and increased sunshine duration were the main contributors to the drought. On the other hand, thermodynamic processes, mostly associated with high temperatures and the resulting increase in atmospheric evaporative demand, were more important in the south. Finally, using flow circulation analogs we show that this drought was more severe than it would have been in the early past.

Download Full-text

A Robust Intensification of Wintertime Jet Stream Extremes in Future Climates

10.5194/egusphere-egu21-14521 ◽

2021 ◽

Author(s):

Ben Harvey

Keyword(s):

North America ◽

North Atlantic ◽

Western Europe ◽

Subsequent Development ◽

Jet Stream ◽

Wind Speeds ◽

The North ◽

Sequence Of Events ◽

The North Atlantic ◽

Jet Streak

The east coast of North America experienced a record-breaking jet stream event on 20 Feb 2019, with peak wind speeds exceeding 110 m/s observed by weather balloons over Nova Scotia. At the time this was the strongest wind speed ever recorded over North America. The extreme `jet streak' propagated out over the North Atlantic where it played a key role in the subsequent development of a large and rapidly deepening cyclone on 22 Feb 2019. The cyclone had little societal impact because it did not make landfall. It did however act to amplify a large scale Rossby wave, producing a strong poleward advection of warm air towards western Europe, and leading to record-breaking February warmth in several European countries on 27 Feb 2019. The whole sequence of events took just over a week to complete.This case provides an illustration of how climate extremes (here the record warmth in western Europe) are often the result of complex and chaotic nonlinear interactions of the atmosphere on weather timescales. The particular sequence of events is not uncommon, but both the strength of the initial jet streak over North America and the resulting temperatures in Europe were. Given the observed trend in surface temperatures, it seems likely that the temperatures were at least partly enhanced in a passive way by the warming climate. A more difficult question to answer is whether climate change is also impacting the frequency or amplitude of the preceding sequence of weather events. As a first step to answering this question, this study asks the question: do we expect extreme jet streak events to intensify in future?Based on an analysis of CMIP simulations over the North Atlantic, we find a robust intensification of wintertime jet extremes in future climates, with the strongest instantaneous wind speeds increasing in every model. This contrasts with the strength of the time mean jet streams, which do not exhibit a robust change across the ensemble. Possible reasons for the differing behaviour of the mean winds and the extreme winds are discussed and a hypothesis is suggested to explain the robust increase in the latter.

Download Full-text