What do large‐scale patterns teach us about extreme precipitation over the Mediterranean at medium‐ and extended‐range forecasts?

Extreme precipitation in the Northern French Alps are mainly associated with large-scale circulations (LSCs) bringing moist air from the Atlantic Ocean and the Mediterranean Sea - two atmospheric influences that are very frequent in the climatology. In this work, we investigate what characterizes the Atlantic/Mediterranean circulations driving extreme precipitation in the Northern French Alps in comparison to "random" Atlantic/Mediterranean circulations. We focus on extreme 3-day precipitation over two medium size neighboring catchments from 1950 to 2017. Atlantic and Mediterranean circulations are identified using an existing weather pattern classification established for Southern France. Every single LSC is characterized using three atmospheric descriptors based on analogy in geopotential shapes at 500hPa over Western Europe that were introduced in previous works. They are i) the celerity, characterizing the stationary nature of a geopotential shape, and ii) the singularity and relative singularity, characterizing the resemblance of a geopotential shape to its analogs, in other words the way this geopotential shape is closely reproduced in the climatology. We add to these analogy-based descriptors a new (non analogy) descriptor accounting for the strength of the low and high pressure systems. We show that Atlantic/Mediterranean circulations driving extreme 3-day precipitation in the Northern French Alps are the Atlantic/Mediterranean circulations featuring the strongest centers of action as well as the most stationary and the most reproducible geopotential shapes - characteristics that are rare for both atmospheric influences. In the Atlantic case, these characteristics appear to be even more pronounced and rare with regard to the whole climatology, pointing LSC as an important driver of extreme precipitation. In the Mediterranean case, these characteristics appear to be more random with regard to the whole climatology, pointing a more balanced contribution between specific LSC and humidity in driving extreme precipitation.

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Extreme precipitation events in the Mediterranean region: their characteristics and connection to large-scale atmospheric patterns

10.5194/egusphere-egu2020-8593 ◽

2020 ◽

Author(s):

Nikolaos Mastrantonas ◽

Linus Magnusson ◽

Florian Pappenberger ◽

Jörg Matschullat

Keyword(s):

Natural Hazards ◽

Extreme Events ◽

Extreme Precipitation ◽

Mediterranean Region ◽

Large Scale ◽

Early Warning Systems ◽

Spatiotemporal Variability ◽

Extreme Precipitation Events ◽

The Mediterranean ◽

Precipitation Events

The Mediterranean region is an area with half a billion population, about 10 percent contribution to the world&#8217;s GDP, and locations of global natural, historical and cultural significance. In this context, natural hazards in the area have the potential for severe negative impacts on society, economy, and environment.&#160;Some of the most frequent and devastating natural hazards that affect the Mediterranean relate to extreme precipitation events causing flash floods and landslides. Thus, given their adverse consequences, it is of immense importance to better understand their statistical characteristics and connection to large-scale atmospheric patterns. Such advances can substantially support the accurate and early identification of these extreme events, improve early warning systems, and contribute to mitigating related risks.&#160;This work focuses on the characteristics and spatiotemporal variability of extreme precipitation events of large spatial coverage across the Mediterranean region. The study uses the ERA5 dataset, the latest, state of the art, reanalysis dataset from Copernicus/ECMWF. Initially, exploratory analysis is performed to assess the different characteristics at various subdomains within the study area. Furthermore, composite analysis is used to understand the connection of extreme events with large-scale atmospheric patterns. Finally, the Empirical Orthogonal Function (EOF) analysis is implemented to quantify the importance of weather regimes with respect to the frequency of extreme precipitation events.&#160;Preliminary results indicate that there is a spatial division in the occurrence of identified events. Winter and autumn are the seasons of the highest frequency of extreme precipitation for the east and west Mediterranean respectively. Troughs and cut-off lows in the lower and middle-level troposphere have a strong association with such extreme events, and the effect is modulated by other parameters, such as local orography. Results of this work are in accordance with previous studies in the region and provide information that can be utilized by future research for improving the predictability of such events in the medium- and extended-range forecasts.&#160;This work is part of the Climate Advanced Forecasting of sub-seasonal Extremes (CAFE) project. The project has received funding from the European Union&#8217;s Horizon 2020 research and innovation programme under the Marie Sk&#322;odowska-Curie grant agreement No 813844.

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Predictability of large-scale atmospheric flow patterns connected to extreme precipitation events in the Mediterranean

10.5194/egusphere-egu21-9931 ◽

2021 ◽

Author(s):

Nikolaos Mastrantonas ◽

Linus Magnusson ◽

Florian Pappenberger ◽

Jörg Matschullat

Keyword(s):

Extreme Precipitation ◽

Mediterranean Region ◽

Large Scale ◽

Prediction Models ◽

Weather Prediction ◽

Flow Patterns ◽

Atmospheric Flow ◽

Extreme Precipitation Events ◽

The Mediterranean ◽

Precipitation Events

The Mediterranean region frequently experiences extreme precipitation events with devastating consequences for the affected societies, economies, and environment. Being able to provide reliable and skillful predictions of such events is crucial for mitigating their adverse impacts and related risks. One important part of the risk mitigation chain is the sub-seasonal predictability of such extremes, with information provided at such timescales supporting a range of actions, as for example warn decision-makers, and preposition materials and equipment.This work focuses on the predictability of large-scale atmospheric flow patterns connected to extreme precipitation events in the Mediterranean. Previous research has identified strong connections between localized extremes and large-scale patterns. This is promising to provide useful information at sub-seasonal timescales. For such lead times, the Numerical Weather Prediction models are more skillful in predicting large-scale patterns than localized extremes. Here, we analyze the usefulness of these connections at sub-seasonal timescales by using the ECMWF extended-range forecasts. We aim at quantifying related benefits for the different areas in the Mediterranean region and providing insights that are of interest to the operational community.Initial results suggest that the ECMWF forecasts provide skillful information in the predictability of large-scale patterns up to about 15 days lead time.&#160;<img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gnp.3687c29b370068376801161/sdaolpUECMynit/12UGE&app=m&a=0&c=49e65b5908090e0787f0f7f4f8930219&ct=x&pn=gnp.elif&d=1" alt="">Large-scale patterns over the Mediterranean based on anomalies of sea level pressure (color shades) and geopotential at 500 hPa (contours) (Figure adapted from Mastrantonas et al, 2020)

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Alexandria, Kom el-Dikka. Fieldwork in the 2019 season

10.31338/uw.2083-537x.pam29.2.20 ◽

2020 ◽

pp. 469-496

Author(s):

Grzegorz Majcherek

Keyword(s):

Large Scale ◽

Direct Evidence ◽

Geometric Design ◽

Late Antique ◽

Construction Work ◽

Floor Tiles ◽

Stone Material ◽

The Mediterranean ◽

Late Roman

The report offers an account of archaeological and conservation work carried out at the site. Excavations in the central part of the site (Sector F) were continued for the fourth season in a row. Exploration of remains of early Roman houses led to the discovery of a well preserved multicolored triclinium mosaic floor with a floral and geometric design. A large assemblage of fragments of polychrome marble floor tiles, recorded in the house collapse, showed the scale of importation of decorative stone material from various regions of the Mediterranean. Overlying the early Roman strata was direct evidence of intensive construction work carried out in the vicinity in the form of large-scale kilnworks, supplying lime most probably for the building of the late Roman bath and cistern. Included in the presentation is a brief review of the limited conservation work that was conducted in the complex of late antique auditoria.

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Impact of air–sea coupling on the climate change signal over the Iberian Peninsula

Climate Dynamics ◽

10.1007/s00382-021-05812-x ◽

2021 ◽

Author(s):

Alba de la Vara ◽

William Cabos ◽

Dmitry V. Sein ◽

Claas Teichmann ◽

Daniela Jacob

Keyword(s):

Climate Change ◽

Iberian Peninsula ◽

Mediterranean Sea ◽

Large Scale ◽

Regional Distribution ◽

Coupled Model ◽

Climate Change Signal ◽

The North ◽

The Mediterranean ◽

The Impact

AbstractIn this work we use a regional atmosphere–ocean coupled model (RAOCM) and its stand-alone atmospheric component to gain insight into the impact of atmosphere–ocean coupling on the climate change signal over the Iberian Peninsula (IP). The IP climate is influenced by both the Atlantic Ocean and the Mediterranean sea. Complex interactions with the orography take place there and high-resolution models are required to realistically reproduce its current and future climate. We find that under the RCP8.5 scenario, the generalized 2-m air temperature (T2M) increase by the end of the twenty-first century (2070–2099) in the atmospheric-only simulation is tempered by the coupling. The impact of coupling is specially seen in summer, when the warming is stronger. Precipitation shows regionally-dependent changes in winter, whilst a drier climate is found in summer. The coupling generally reduces the magnitude of the changes. Differences in T2M and precipitation between the coupled and uncoupled simulations are caused by changes in the Atlantic large-scale circulation and in the Mediterranean Sea. Additionally, the differences in projected changes of T2M and precipitation with the RAOCM under the RCP8.5 and RCP4.5 scenarios are tackled. Results show that in winter and summer T2M increases less and precipitation changes are of a smaller magnitude with the RCP4.5. Whilst in summer changes present a similar regional distribution in both runs, in winter there are some differences in the NW of the IP due to differences in the North Atlantic circulation. The differences in the climate change signal from the RAOCM and the driving Global Coupled Model show that regionalization has an effect in terms of higher resolution over the land and ocean.

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Geospatial Analysis of Extreme Weather Events in Nigeria (1985–2015) Using Self-Organizing Maps

Advances in Meteorology ◽

10.1155/2017/8576150 ◽

2017 ◽

Vol 2017 ◽

pp. 1-11 ◽

Cited By ~ 9

Author(s):

Adeoluwa Akande ◽

Ana Cristina Costa ◽

Jorge Mateu ◽

Roberto Henriques

Keyword(s):

Extreme Precipitation ◽

Large Scale ◽

Northern Region ◽

Extreme Weather Events ◽

Self Organizing Map ◽

Spatial And Temporal Patterns ◽

Self Organizing Maps ◽

The North ◽

Precipitation Regimes ◽

Self Organizing

The explosion of data in the information age has provided an opportunity to explore the possibility of characterizing the climate patterns using data mining techniques. Nigeria has a unique tropical climate with two precipitation regimes: low precipitation in the north leading to aridity and desertification and high precipitation in parts of the southwest and southeast leading to large scale flooding. In this research, four indices have been used to characterize the intensity, frequency, and amount of rainfall over Nigeria. A type of Artificial Neural Network called the self-organizing map has been used to reduce the multiplicity of dimensions and produce four unique zones characterizing extreme precipitation conditions in Nigeria. This approach allowed for the assessment of spatial and temporal patterns in extreme precipitation in the last three decades. Precipitation properties in each cluster are discussed. The cluster closest to the Atlantic has high values of precipitation intensity, frequency, and duration, whereas the cluster closest to the Sahara Desert has low values. A significant increasing trend has been observed in the frequency of rainy days at the center of the northern region of Nigeria.

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Subseasonal Forecasts of the Northern Queensland Floods of February 2019: Causes and Forecast Evaluation

Atmosphere ◽

10.3390/atmos12060758 ◽

2021 ◽

Vol 12 (6) ◽

pp. 758

Author(s):

Wayne Yuan-Huai Tsai ◽

Mong-Ming Lu ◽

Chung-Hsiung Sui ◽

Yin-Min Cho

Keyword(s):

Large Scale ◽

Deep Convection ◽

Austral Summer ◽

Rainfall Event ◽

Monsoon Depression ◽

Forecast Skill ◽

Sea Surface ◽

Central Pacific ◽

Percentile Rank ◽

Extended Range

During the austral summer 2018/19, devastating floods occurred over northeast Australia that killed approximately 625,000 head of cattle and inundated over 3000 homes in Townsville. In this paper, the disastrous event was identified as a record-breaking subseasonal peak rainfall event (SPRE). The SPRE was mainly induced by an anomalously strong monsoon depression that was modulated by the convective phases of an MJO and an equatorial Rossby (ER) wave. The ER wave originated from an active equatorial deep convection associated with the El Niño warm sea surface temperatures near the dateline over the central Pacific. Based on the S2S Project Database, we analyzed the extended-range forecast skill of the SPRE from two different perspectives, the monsoon depression represented by an 850-hPa wind shear index and the 15-day accumulated precipitation characterized by the percentile rank (PR) and the ratio to the three-month seasonal (DJF) totals. The results of four S2S models of this study suggest that the monsoon depression can maintain the same level of skill as the short-range (3 days) forecast up to 8–10 days. For precipitation parameters, the conclusions are similar to the monsoon depression. For the 2019 northern Queensland SPRE, the model forecast was, in general, worse than the expectation derived from the hindcast analysis. The clear modulation of the ER wave that enhanced the SPRE monsoon depression circulation and precipitation is suspected as the main cause for the lower forecast skill. The analysis procedure proposed in this study can be applied to analyze the SPREs and their associated large-scale drivers in other regions.

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Observed trends in extreme precipitation events in China during 1961–2001 and the associated changes in large-scale circulation

Geophysical Research Letters ◽

10.1029/2005gl022574 ◽

2005 ◽

Vol 32 (9) ◽

Cited By ~ 177

Author(s):

Yuqing Wang

Keyword(s):

Extreme Precipitation ◽

Large Scale ◽

Large Scale Circulation ◽

Extreme Precipitation Events ◽

Precipitation Events

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A Near-Uniform Basin-Wide Sea Level Fluctuation of the Mediterranean Sea

Journal of Physical Oceanography ◽

10.1175/jpo3016.1 ◽

2007 ◽

Vol 37 (2) ◽

pp. 338-358 ◽

Cited By ~ 56

Author(s):

Ichiro Fukumori ◽

Dimitris Menemenlis ◽

Tong Lee

Keyword(s):

Atlantic Ocean ◽

Mediterranean Sea ◽

Sea Level ◽

Ocean Circulation ◽

Large Scale ◽

Circulation Model ◽

Level Fluctuation ◽

Strait Of Gibraltar ◽

Sea Level Fluctuation ◽

The Mediterranean

Abstract A new basin-wide oscillation of the Mediterranean Sea is identified and analyzed using sea level observations from the Ocean Topography Experiment (TOPEX)/Poseidon satellite altimeter and a numerical ocean circulation model. More than 50% of the large-scale, nontidal, and non-pressure-driven variance of sea level can be attributed to this oscillation, which is nearly uniform in phase and amplitude across the entire basin. The oscillation has periods ranging from 10 days to several years and has a magnitude as large as 10 cm. The model suggests that the fluctuations are driven by winds at the Strait of Gibraltar and its neighboring region, including the Alboran Sea and a part of the Atlantic Ocean immediately to the west of the strait. Winds in this region force a net mass flux through the Strait of Gibraltar to which the Mediterranean Sea adjusts almost uniformly across its entire basin with depth-independent pressure perturbations. The wind-driven response can be explained in part by wind setup; a near-stationary balance is established between the along-strait wind in this forcing region and the sea level difference between the Mediterranean Sea and the Atlantic Ocean. The amplitude of this basin-wide wind-driven sea level fluctuation is inversely proportional to the setup region’s depth but is insensitive to its width including that of Gibraltar Strait. The wind-driven fluctuation is coherent with atmospheric pressure over the basin and contributes to the apparent deviation of the Mediterranean Sea from an inverse barometer response.

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