Predictability of moisture flux anomalies indicating central European extreme precipitation events

Abstract A climatology of extreme cold season precipitation events in Norway from 1979 to 2014 is presented, based on the 99th percentile of the 24-h accumulated precipitation. Three regions, termed north, west, and south are identified, each exhibiting a unique seasonal distribution. There is a proclivity for events to occur during the positive phase of the NAO. The result is statistically significant at the 95th percentile for the north and west regions. An overarching hypothesis of this work is that anomalous moisture flux, or so-called atmospheric rivers (ARs), are integral to extreme precipitation events during the Norwegian cold season. An objective analysis of the integrated vapor transport illustrates that more than 85% of the events are associated with ARs. An empirical orthogonal function and fuzzy cluster technique is used to identify the large-scale weather patterns conducive to the moisture flux and extreme precipitation. Five days before the event and for each of the three regions, two patterns are found. The first represents an intense, southward-shifted jet with a southwest–northeast orientation. The second identifies a weak, northward-shifted, zonal jet. As the event approaches, regional differences become more apparent. The distinctive flow pattern conducive to orographically enhanced precipitation emerges in the two clusters for each region. For the north and west regions, this entails primarily zonal flow impinging upon the south–north-orientated topography, the difference being the latitude of the strong flow. In contrast, the south region exhibits a significant southerly component to the flow.

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Impacts of Storm Track Variations on Wintertime Extreme Precipitation and Moisture Budgets over the Ohio Valley and Northwestern United States

Journal of Climate ◽

10.1175/jcli-d-19-0543.1 ◽

2020 ◽

Vol 33 (13) ◽

pp. 5371-5391

Author(s):

Chen-Geng Ma ◽

Edmund K. M. Chang ◽

Sun Wong ◽

Rui Zhang ◽

Minghua Zhang ◽

...

Keyword(s):

United States ◽

Extreme Precipitation ◽

Moisture Flux ◽

Water Vapor Transport ◽

Lower Latitude ◽

Ohio Valley ◽

Central Pacific ◽

Budget Analysis ◽

Extreme Precipitation Events ◽

Precipitation Events

AbstractPrevious studies have shown that variations in extratropical cyclone activity significantly affect the frequency of extreme precipitation events over the Ohio Valley and northwestern United States. In this study, we examine the similarities and differences between the dynamics governing these events in these two regions. In the Ohio Valley, extreme precipitation events are associated with midlatitude synoptic-scale convergence northeast of cyclones and a southwestward oriented ridge near the Atlantic coast that drives strong water vapor transport from the Gulf of Mexico into the Ohio Valley. In the northwestern United States, extreme precipitation events are associated with a cyclonic and anticyclonic circulation pair aligned northwest to southeast, which together drive a long and strong moisture transport corridor from the lower latitude of the central Pacific Ocean toward the northwestern United States. Moisture budget analysis shows that moisture convergence due to dynamical convergence dominates in the Ohio Valley, whereas moisture advection dominates over the Pacific Northwest. Differences between the cases in the same region are examined by an empirical orthogonal function (EOF) analysis conducted on the vertically integrated moisture flux. Different EOFs highlight shifts in spatial location, orientation, and intensity of the moisture flux but demonstrate consistent roles of dynamics in the two regions. Composites based on these EOFs highlight the range of likely synoptic scenarios that can give rise to precipitation extremes over these two regions.

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Spatial patterns and time distribution of central European extreme precipitation events between 1961 and 2013

International Journal of Climatology ◽

10.1002/joc.6019 ◽

2019 ◽

Vol 39 (7) ◽

pp. 3282-3297 ◽

Cited By ~ 3

Author(s):

Blanka Gvoždíková ◽

Miloslav Müller ◽

Marek Kašpar

Keyword(s):

Spatial Patterns ◽

Extreme Precipitation ◽

Time Distribution ◽

Central European ◽

Extreme Precipitation Events ◽

Precipitation Events

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Understanding Simulated Extreme Precipitation Events in Madison, Wisconsin, and the Role of Moisture Flux Convergence during the Late Twentieth and Twenty-First Centuries*

Journal of Hydrometeorology ◽

10.1175/jhm-d-11-052.1 ◽

2012 ◽

Vol 13 (3) ◽

pp. 877-894 ◽

Cited By ~ 15

Author(s):

Kathleen D. Holman ◽

Stephen J. Vavrus

Keyword(s):

Twentieth Century ◽

Extreme Precipitation ◽

Moisture Flux ◽

First Century ◽

Moisture Flux Convergence ◽

Extreme Precipitation Events ◽

Late Twentieth ◽

Twenty First Century ◽

Precipitation Events

Abstract Understanding extreme precipitation events in the current and future climate system is an important aspect of climate change for adaptation and mitigation purposes. The current study investigates extreme precipitation events over Madison, Wisconsin, during the late twentieth and late twenty-first centuries using 18 coupled ocean–atmosphere general circulation models that participated in the Coupled Model Intercomparison Project (CMIP3). An increase of ~10% is found in the multimodel average of annual precipitation received in Madison by the end of the twenty-first century, with the largest increases projected to occur during winter [December–February (DJF)] and spring [March–May (MAM)]. It is also found that the observed seasonal cycle of precipitation in Madison is not accurately captured by the models. The multimodel average shows a strong seasonal peak in May, whereas observations peak during midsummer. Model simulations also do not accurately capture the annual cycle of extreme precipitation events in Madison, which also peak in summer. Instead, the timing of model-simulated extreme events exhibits a bimodal distribution that peaks during spring and fall. However, spatial composites of average daily precipitation simulated by GCMs during Madison’s wettest 1% of precipitation events during the twentieth century strongly resemble the spatial pattern produced in observations. The role of specific humidity and vertically integrated moisture flux convergence (MFC) during extreme precipitation events in Madison is investigated in twentieth- and twenty-first-century simulations. Spatial composites of MFC during the wettest 1% of days during the twentieth-century simulations agree well with results from the North American Regional Reanalysis dataset (NARR), suggesting that synoptic-scale dynamics are vital to extreme precipitation events.

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