scholarly journals How intense daily precipitation depends on temperature and the occurrence of specific weather systems – an investigation with ERA5 reanalyses in the extratropical Northern Hemisphere

2021 ◽  
Author(s):  
Philipp Zschenderlein ◽  
Heini Wernli
Keyword(s):  
Central Europe ◽  
Northern Hemisphere ◽  
Rocky Mountains ◽  
Daily Precipitation ◽  
Mediterranean Area ◽  
Regional Variability ◽  
Weather System ◽  
Atmospheric Rivers ◽  
Precipitation Efficiency ◽  
Intense Precipitation

Abstract. Precipitation and surface temperature are two of the most important variables that describe our weather and climate. Several previous studies investigated aspects of their relationship, for instance the climatological dependence of daily precipitation on daily mean temperature, P(T). However, the role of specific weather systems in shaping this relationship has not been analysed yet. This study therefore identifies the weather systems (WS) that are associated with intense precipitation days as a function of T, focusing on the question how this relationship, symbolically expressed as P(T,WS), varies regionally across the Northern Hemisphere and between seasons. To this end, we first quantify, if intense precipitation occurs on climatologically warmer or on colder days, respectively. In winter, over most continental and ocean regions, intense precipitation falls on warmer days apart from the Mediterranean area and regions in the lee of the Rocky Mountains, where intense precipitation is favoured on colder days. In summer, only at high latitudes intense precipitation is favoured on warmer days, whereas continental areas experience intense precipitation on colder days. For selected regions in Europe and North America, we then identify the weather systems that occur preferentially on days with intense precipitation (referred to as wet days). In winter, cyclones are slightly dominant on colder wet days, whereas warm conveyor belts and atmospheric rivers occur preferentially on warmer wet days. In summer, the overall influence of atmospheric rivers increases and the occurrence of weather systems depend less on wet day temperature. Wet days in the lee of the Rocky Mountains are influenced by most likely convective systems in anticyclones. Finally, we investigate P(T,WS) during the wettest and driest season in Central Europe and the Central US. In qualitative agreement with the results from the first part of this study, the wettest winter is warmer than normal in Central Europe but colder in the Central US, and the wettest summer is colder in both regions. The opposite holds for the driest winter and summer, respectively. During these anomalous seasons, both the frequency and the precipitation efficiency of weather systems changes in Central Europe, while the wettest and driest seasons in Central US mainly arise from a modified precipitation efficiency. Our results show that the precipitation-temperature-weather system relationship strongly depends on the region, and that (extreme) seasonal precipitation is influenced by the frequency and precipitation efficiency of the different weather systems. This regional variability is reflected in the relative importance of weather system frequency and efficiency anomalies for the formation of anomalously wet and dry seasons.

Uncertainty in different precipitation products in the case of two atmospheric river events

2021 ◽  
Author(s):  
Alexandre M. Ramos ◽  
Rémy Roca ◽  
Pedro M.M. Soares ◽  
Anna M. Wilson ◽  
Ricardo M. Trigo ◽  
...  
Keyword(s):  
North Atlantic ◽  
Daily Precipitation ◽  
Climate Extremes ◽  
Research Programme ◽  
Late Glacial ◽  
Atmospheric Rivers ◽  
Atmospheric River ◽  
Western Us ◽  
Weather And Climate ◽  
The Tropics

<p>One of the World Climate Research Programme Grand Challenges is to evaluate whether existing observations are enough to underpin the assessment of weather and climate extremes. In this study, we focus on extreme associated with Atmospheric Rivers (ARs). ARs are characterized by intense moisture transport usually from the tropics to the extra-tropics. They can either be beneficial, providing critical water supply, or hazardous, when excessive precipitation accumulation leads to floods. Here, we examine the uncertainty in gridded precipitation products included in the Frequent Rainfall Observations on GridS (FROGS) database during two atmospheric river events in distinct Mediterranean climates: one in California, USA, and another in Portugal. FROGS is composed of gridded daily-precipitation products on a common 1∘×1∘ grid to facilitate intercomparison and assessment exercises. The database includes satellite, ground-based and reanalysis products. Results show that the precipitation products based on satellite data, individually or combined with other products, perform least well in capturing daily precipitation totals over land during both cases studied here. The reanalysis and the gauge-based products show the best agreement with local ground stations. As expected, there is an overall underestimation of precipitation by the different products. For the Portuguese AR, the multi-product ensembles reveal mean absolute percentage errors between -25% and -60%. For the Western US case, the range is from -60% to -100 %. </p><p> </p><p>Acknowledgments</p><p>The financial support for this work was possible through the following FCT project: HOLMODRIVE—North Atlantic Atmospheric Patterns Influence on Western Iberia Climate: From the Late Glacial to the Present (PTDC/CTA-GEO/29029/2017). A.M. Ramos was supported by the Scientific Employment Stimulus 2017 from Fundação para a Ciência e a Tecnologia (FCT, CEECIND/00027/2017). </p><p> </p>

scholarly journals Simulation of Daily Extreme Precipitation over the United States in the CMIP5 30-Yr Decadal Prediction Experiment

2019 ◽  
Vol 58 (4) ◽  
pp. 875-886 ◽  
Author(s):  
Steve T. Stegall ◽  
Kenneth E. Kunkel
Keyword(s):  
United States ◽  
Extreme Precipitation ◽  
Daily Precipitation ◽  
The United States ◽  
Natural Variability ◽  
Return Level ◽  
Historical Period ◽  
Regional Variability ◽  
Anthropogenic Forcing ◽  
Near Term

AbstractThe CMIP5 decadal hindcast (“Hindcast”) and prediction (“Predict”) experiment simulations from 11 models were analyzed for the United States with respect to two metrics of extreme precipitation: the 10-yr return level of daily precipitation, derived from the annual maximum series of daily precipitation, and the total precipitation exceeding the 99.5th percentile of daily precipitation. Both Hindcast simulations and observations generally show increases for the 1981–2010 historical period. The multimodel-mean Hindcast trends are statistically significant for all regions while the observed trends are statistically significant for the Northeast, Southeast, and Midwest regions. An analysis of CMIP5 simulations driven by historical natural (“HistoricalNat”) forcings shows that the Hindcast trends are generally within the 5th–95th-percentile range of HistoricalNat trends, but those outside that range are heavily skewed toward exceedances of the 95th-percentile threshold. Future projections for 2006–35 indicate increases in all regions with respect to 1981–2010. While there is good qualitative agreement between the observations and Hindcast simulations regarding the direction of recent trends, the multimodel-mean trends are similar for all regions, while there is considerable regional variability in observed trends. Furthermore, the HistoricalNat simulations suggest that observed historical trends are a combination of natural variability and anthropogenic forcing. Thus, the influence of anthropogenic forcing on the magnitude of near-term future changes could be temporarily masked by natural variability. However, continued observed increases in extreme precipitation in the first decade (2006–15) of the “future” period partially confirm the Predict results, suggesting that incorporation of increases in planning would appear prudent.

scholarly journals Impacts of Atmospheric Rivers in Extreme Precipitation on the European Macaronesian Islands

Atmosphere ◽  
2018 ◽  
Vol 9 (8) ◽  
pp. 325 ◽  
Author(s):  
Alexandre M. Ramos ◽  
Ricardo M. Trigo ◽  
Ricardo Tomé ◽  
Margarida L. R. Liberato
Keyword(s):  
Canary Islands ◽  
Extreme Precipitation ◽  
Daily Precipitation ◽  
Comprehensive Assessment ◽  
Atmospheric Rivers ◽  
Extreme Precipitation Events ◽  
Macaronesian Islands ◽  
Weather Stations ◽  
The Relationship ◽  
Precipitation Events

The European Macaronesia Archipelagos (Azores, Madeira and Canary Islands) are struck frequently by extreme precipitation events. Here we present a comprehensive assessment on the relationship between atmospheric rivers and extreme precipitation events in these three Atlantic Archipelagos. The relationship between the daily precipitation from the various weather stations located in the different Macaronesia islands and the occurrence of atmospheric rivers (obtained from four different reanalyses datasets) are analysed. It is shown that the atmospheric rivers’ influence over extreme precipitation (above the 90th percentile) is higher in the Azores islands when compared to Madeira or Canary Islands. In Azores, for the most extreme precipitation days, the presence of atmospheric rivers is particularly significant (up to 50%), while for Madeira, the importance of the atmospheric rivers is reduced (between 30% and 40%). For the Canary Islands, the occurrence of atmospheric rivers on extreme precipitation is even lower.

scholarly journals Precipitation Sensitivity to the Uncertainty of Terrestrial Water Flow in WRF-Hydro: An Ensemble Analysis for Central Europe

2018 ◽  
Vol 19 (6) ◽  
pp. 1007-1025 ◽  
Author(s):  
Joël Arnault ◽  
Thomas Rummler ◽  
Florian Baur ◽  
Sebastian Lerch ◽  
Sven Wagner ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Spatial Variability ◽  
Central Europe ◽  
Water Flow ◽  
Daily Precipitation ◽  
Three Dimensional ◽  
Wrf Model ◽  
Vertical Direction ◽  
Surface Flux ◽  
Terrestrial Water

Abstract Precipitation is affected by soil moisture spatial variability. However, this variability is not well represented in atmospheric models that do not consider soil moisture transport as a three-dimensional process. This study investigates the sensitivity of precipitation to the uncertainty in the representation of terrestrial water flow. The tools used for this investigation are the Weather Research and Forecasting (WRF) Model and its hydrologically enhanced version, WRF-Hydro, applied over central Europe during April–October 2008. The model grid is convection permitting, with a horizontal spacing of 2.8 km. The WRF-Hydro subgrid employs a 280-m resolution to resolve lateral terrestrial water flow. A WRF/WRF-Hydro ensemble is constructed by modifying the parameter controlling the partitioning between surface runoff and infiltration and by varying the planetary boundary layer (PBL) scheme. This ensemble represents terrestrial water flow uncertainty originating from the consideration of resolved lateral flow, terrestrial water flow uncertainty in the vertical direction, and turbulence parameterization uncertainty. The uncertainty of terrestrial water flow noticeably increases the normalized ensemble spread of daily precipitation where topography is moderate, surface flux spatial variability is high, and the weather regime is dominated by local processes. The adjusted continuous ranked probability score shows that the PBL uncertainty improves the skill of an ensemble subset in reproducing daily precipitation from the E-OBS observational product by 16%–20%. In comparison to WRF, WRF-Hydro improves this skill by 0.4%–0.7%. The reproduction of observed daily discharge with Nash–Sutcliffe model efficiency coefficients generally above 0.3 demonstrates the potential of WRF-Hydro in hydrological science.

scholarly journals A Climatology of the Mesoscale Environment Associated with Heavily Precipitating Events over a Northwestern Mediterranean Area

2012 ◽  
Vol 51 (3) ◽  
pp. 468-488 ◽  
Author(s):  
Didier Ricard ◽  
Véronique Ducrocq ◽  
Ludovic Auger
Keyword(s):  
Daily Precipitation ◽  
Flow Instability ◽  
Three Dimensional ◽  
Mediterranean Area ◽  
Mature Stage ◽  
Target Area ◽  
High Moisture ◽  
Low Level ◽  
Ridge Pattern ◽  
Low Level Jet

AbstractA climatological approach is developed to characterize the mesoscale environment in which heavily precipitating events (HPEs) grow over a mountainous Mediterranean area. This climatology that is based on three-dimensional variational data assimilation (3D-Var) mesoscale analyses is performed for a 5-yr period, considering cases with daily precipitation of >150 mm occurring over southern France during autumn. Different diagnostics are used to document the time evolution of mesoscale features associated with the HPEs for initiation, mature, and dissipation stages. To underline differences according to the location of precipitation, four subdomains are also considered: Languedoc-Roussillon, Cévennes-Vivarais, South Alps, and Corsica. Composite analyses show that these events are driven by some common features (slowly evolving trough–ridge pattern and diffluent midlevel flow). Instability and moisture are transported by the low-level jet (LLJ) toward the target area from their sources, which are located upstream over the Mediterranean Sea. Strong moisture convergence is located within the left exit of the LLJ. These parameters reach a maximum during the mature stage. During the life cycle of the HPEs, the low-level winds rotate clockwise. Composite analyses also show that the synoptic and mesoscale patterns can differ greatly as a function of the location of the precipitation. Indeed, the LLJ varies from southeasterly to southwesterly. The midlevel flow varies from southerly to southwesterly. The areas of high moisture and instability are stretched in different orientations. Long-lasting events are associated with a more pronounced quasi-stationary trough–ridge pattern, higher values of CAPE, a wetter troposphere, and faster LLJ. The most-heavily precipitating events are found to be in general associated with higher values of these parameters or with a low-level inflow that is closer to perpendicular to the relief.

scholarly journals A PV Perspective on the Vertical Structure of Mature Midlatitude Cyclones in the Northern Hemisphere

2012 ◽  
Vol 69 (2) ◽  
pp. 725-740 ◽  
Author(s):  
Jana Čampa ◽  
Heini Wernli
Keyword(s):  
Northern Hemisphere ◽  
Potential Vorticity ◽  
Vertical Structure ◽  
Potential Temperature ◽  
Vertical Cylinder ◽  
Mature Stage ◽  
Extratropical Cyclones ◽  
Surface Acting ◽  
Regional Variability ◽  
Stratospheric Intrusion

Abstract Development of extratropical cyclones can be seen as an interplay of three positive potential vorticity anomalies: an upper-level stratospheric intrusion, low-tropospheric diabatically produced potential vorticity (PV), and a warm anomaly at the surface acting as a surrogate PV anomaly. This study, based on the interim ECMWF Re-Analysis (ERA-Interim) dataset, quantifies the amplitude of the PV anomalies of mature extratropical cyclones in different regions in the Northern Hemisphere on a climatological basis. A tracking algorithm is applied to sea level pressure (SLP) fields to identify cyclone tracks. Surface potential temperature anomalies Δθ and vertical profiles of PV anomalies ΔPV are calculated at the time of the cyclones’ minimum SLP in a vertical cylinder around the surface cyclone center. To compare the cyclones’ characteristics they are grouped according to their location and intensity. Composite ΔPV profiles are calculated for each region and intensity class at the time of minimum SLP and during the cyclone intensification phase. In the mature stage all three anomalies are on average larger for intense than for weak winter cyclones [e.g., 0.6 versus 0.2 potential vorticity units (PVU; 1 PVU = 10−6 K kg−1 m2 s−1) at lower levels, and 1.5 versus 0.5 PVU at upper levels]. The regional variability of the cyclones’ vertical structure and the profile evolution is prominent (cyclones in some regions are more sensitive to the amplitude of a particular anomaly than in other regions). Values of Δθ and low-level ΔPV are on average larger in the western parts of the oceans than in the eastern parts. Results for summer are qualitatively similar, except for distinctively weaker surface Δθ values.

scholarly journals Atmospheric Rivers and Precipitation in the Middle East and North Africa (MENA)

Water ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2863
Author(s):  
Elias Massoud ◽  
Theresa Massoud ◽  
Bin Guan ◽  
Agniv Sengupta ◽  
Vicky Espinoza ◽  
...  
Keyword(s):  
Middle East ◽  
North Africa ◽  
Daily Precipitation ◽  
Large Fraction ◽  
Coupled Model ◽  
Mena Region ◽  
Atmospheric Rivers ◽  
The North ◽  
Projected Change ◽  
Change In Mean

This study investigates the historical climatology and future projected change of atmospheric rivers (ARs) and precipitation for the Middle East and North Africa (MENA) region. We use a suite of models from the Coupled Model Intercomparison Project Phase 5 (CMIP5, historical and RCP8.5 scenarios) and other observations to estimate AR frequency and mean daily precipitation. Despite its arid-to-semi-arid climate, parts of the MENA region experience strong ARs, which contribute a large fraction of the annual precipitation, such as in the mountainous areas of Turkey and Iran. This study shows that by the end of this century, AR frequency is projected to increase (~20–40%) for the North Africa and Mediterranean areas (including any region with higher latitudes than 35 N). However, for these regions, mean daily precipitation (i.e., regardless of the presence of ARs) is projected to decrease (~15–30%). For the rest of the MENA region, including the Arabian Peninsula and the Horn of Africa, minor changes in AR frequency (±10%) are expected, yet mean precipitation is projected to increase (~50%) for these regions. Overall, the projected sign of change in AR frequency is opposite to the projected sign of change in mean daily precipitation for most areas within the MENA region.

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