scholarly journals A Climatology of Atmospheric Rivers in New Zealand

2021 ◽  
Vol 34 (11) ◽  
pp. 4383-4402
Author(s):  
Hamish D. Prince ◽  
Nicolas J. Cullen ◽  
Peter B. Gibson ◽  
Jono Conway ◽  
Daniel G. Kingston
Keyword(s):  
New Zealand ◽  
Extreme Precipitation ◽  
Moisture Flux ◽  
Cold Season ◽  
Southern Alps ◽  
Windward Side ◽  
Western Coast ◽  
Jet Streams ◽  
Extreme Precipitation Events ◽  
Hemisphere Winter

AbstractThe occurrence of extreme precipitation events in New Zealand regularly results in devastating impacts to the local society and environment. An automated atmospheric river (AR) detection technique (ARDT) is applied to construct a climatology (1979–2019) of extreme midlatitude moisture fluxes conducive to extreme precipitation. A distinct seasonality exists in AR occurrence aligning with seasonal variations in the midlatitude jet streams. The formation of the Southern Hemisphere winter split jet enables AR occurrence to persist through all seasons in northern regions of New Zealand, while southern regions of the country exhibit a substantial (50%) reduction in AR occurrence as the polar jet shifts southward during the cold season. ARs making landfall on the western coast of New Zealand (90% of all events) are characterized by a dominant northwesterly moisture flux associated with a distinct dipole pressure anomaly, with low pressure to the southwest and high pressure to the northeast of New Zealand. Precipitation totals during AR events increase with AR rank (five-point scale) throughout the country, with the most substantial increase on the windward side of the Southern Alps (South Island). The largest events (rank 5 ARs) produce 3-day precipitation totals exceeding 1000 mm. ARs account for up to 78% of total precipitation and up to 94% of extreme precipitation on the west coast of the South Island. Assessment of the multiscale atmospheric processes associated with AR events governing extreme precipitation in the Southern Alps of New Zealand should remain a priority given their hydrological significance and impact on people and infrastructure.

scholarly journals Large-Scale Flow Patterns Associated with Extreme Precipitation and Atmospheric Rivers over Norway

2019 ◽  
Vol 147 (4) ◽  
pp. 1415-1428 ◽  
Author(s):  
Imme Benedict ◽  
Karianne Ødemark ◽  
Thomas Nipen ◽  
Richard Moore
Keyword(s):  
Extreme Precipitation ◽  
Large Scale ◽  
Moisture Flux ◽  
Cold Season ◽  
Fuzzy Cluster ◽  
The South ◽  
Atmospheric Rivers ◽  
The North ◽  
Extreme Precipitation Events ◽  
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.

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

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.

scholarly journals The Seasonal Nature of Extreme Hydrological Events in the Northeastern United States

2015 ◽  
Vol 16 (5) ◽  
pp. 2065-2085 ◽  
Author(s):  
Allan Frei ◽  
Kenneth E. Kunkel ◽  
Adao Matonse
Keyword(s):  
United States ◽  
Extreme Precipitation ◽  
Extreme Event ◽  
Warm Season ◽  
The United States ◽  
Cold Season ◽  
Northeastern United States ◽  
Extreme Precipitation Events ◽  
Extreme Hydrological Events ◽  
Precipitation Events

Abstract Recent analyses of extreme hydrological events across the United States, including those summarized in the recent U.S. Third National Climate Assessment (May 2014), show that extremely large (extreme) precipitation and streamflow events are increasing over much of the country, with particularly steep trends over the northeastern United States. The authors demonstrate that the increase in extreme hydrological events over the northeastern United States is primarily a warm season phenomenon and is caused more by an increase in frequency than magnitude. The frequency of extreme warm season events peaked during the 2000s; a secondary peak occurred during the 1970s; and the calmest decade was the 1960s. Cold season trends during the last 30–50 yr are weaker. Since extreme precipitation events in this region tend to be larger during the warm season than during the cold season, trend analyses based on annual precipitation values are influenced more by warm season than by cold season trends. In contrast, the magnitude of extreme streamflow events at stations used for climatological analyses tends to be larger during the cold season: therefore, extreme event analyses based on annual streamflow values are overwhelmingly influenced by cold season, and therefore weaker, trends. These results help to explain an apparent discrepancy in the literature, whereby increasing trends in extreme precipitation events appear to be significant and ubiquitous across the region, while trends in streamflow appear less dramatic and less spatially coherent.

Long-term changes of precipitation in Latvia

2010 ◽  
Vol 41 (3-4) ◽  
pp. 241-252 ◽  
Author(s):  
Lita Lizuma ◽  
Agrita Briede ◽  
Maris Klavins
Keyword(s):  
Extreme Precipitation ◽  
Winter Season ◽  
Cold Season ◽  
Annual Precipitation ◽  
Precipitation Pattern ◽  
Term Trend ◽  
Positive Tendency ◽  
Extreme Precipitation Events ◽  
Long Term Trend

This study investigated long-term variability and trends in Latvia's annual, seasonal, monthly and daily precipitation using data from 10 meteorological stations for the period 1925–2006 and from station Riga University for the period 1850–2006. The obtained results indicate that during the 20th century a significant increase in precipitation has occurred in the cold season while the warm period showed a decreasing tendency. The annual precipitation totals showed a slight decrease, at half of the studied stations, due to opposite tendencies in cold season and warm season. The long-term trend in the annual precipitation in Riga (from 1850) was positive with large interannual and interdecadal variability. The extreme precipitation events were evaluated using a set of nine climate change indices. Of these, number of wet days, 1-day and 5-days maximum precipitation, moderate wet days and very wet days showed a well pronounced positive tendency in the cold period of the year particularly in winter. No overall long-term trend was detected in extreme precipitation in summer. As in the case of 150-year precipitation pattern, extreme precipitation exhibited cyclic fluctuations that were more pronounced than linear changes. The close correlation between North Atlantic oscillation (NAO) and extreme precipitation was found for winter season.

scholarly journals Characterization of extreme precipitation within atmospheric river events over California

2015 ◽  
Vol 1 (1) ◽  
pp. 45-57 ◽  
Author(s):  
S. Jeon ◽  
S. Byna ◽  
J. Gu ◽  
W. D. Collins ◽  
M. F. Wehner ◽  
...  
Keyword(s):  
Extreme Precipitation ◽  
Large Scale ◽  
Climate Model ◽  
Western Coast ◽  
Climate Data ◽  
Extreme Precipitation Events ◽  
The Future ◽  
High Concentrations ◽  
Climate Analysis ◽  
The Impact

Abstract. Atmospheric rivers (ARs) are large, spatially coherent weather systems with high concentrations of elevated water vapor. These systems often cause severe downpours and flooding over the western coastal United States – and with the availability of more atmospheric moisture in the future under global warming we expect ARs to play an important role as potential causes of extreme precipitation changes. Therefore, we aim to investigate changes in extreme precipitation properties correlated with AR events in a warmer climate, which are large-scale meteorological patterns affecting the weather and climate of California. We have recently developed the TECA (Toolkit for Extreme Climate Analysis) software for automatically identifying and tracking features in climate data sets. Specifically, we can now identify ARs that make landfall on the western coast of North America. Based on this detection procedure, we can investigate the impact of ARs by exploring the spatial extent of AR precipitation using climate model (CMIP5) simulations and characterize spatial patterns of dependence for future projections between AR precipitation extremes under climate change within the statistical framework. Our results show that AR events in the future RCP (Representative Concentration Pathway)8.5 scenario (2076–2100) tend to produce heavier rainfall with higher frequency and longer days than events from the historical run (1981–2005). We also find that the dependence between extreme precipitation events has a shorter spatial range, within localized areas in California, under the high future emissions scenario than under the historical run.

scholarly journals Atmospheric River–Induced Precipitation and Snowpack during the Western United States Cold Season

2019 ◽  
Vol 20 (4) ◽  
pp. 613-630 ◽  
Author(s):  
Hisham Eldardiry ◽  
Asif Mahmood ◽  
Xiaodong Chen ◽  
Faisal Hossain ◽  
Bart Nijssen ◽  
...  
Keyword(s):  
Sierra Nevada ◽  
Extreme Precipitation ◽  
Snow Water Equivalent ◽  
Weather Prediction ◽  
Cold Season ◽  
Snow Accumulation ◽  
Precipitation Frequency ◽  
Extreme Precipitation Events ◽  
Snow Water ◽  
Precipitation Events

Abstract Atmospheric rivers (ARs) are narrow, elongated corridors of high water vapor content transported from tropical and/or extratropical cyclones. We characterize precipitation and snow water equivalent associated with ARs intersecting the western U.S. coast during the cold season (November– March) of water years 1949–2015. For each AR landfalling date, we retrieved the precipitation and relevant hydrometeorological variables from dynamically downscaled atmospheric reanalyses (NCEP–NCAR) using the WRF mesoscale numerical weather prediction model. Landfalling ARs resulted in higher precipitation amounts throughout the domain than did non-AR storms. ARs contributed the most extreme precipitation events during January and February. Daily snow water equivalent (SWE) changes during ARs indicate that high positive net snow accumulation conditions accompany ARs in December, January, and February. We also assess the historical impact of AR storm duration and precipitation frequency by considering the precipitation depth estimated during a 72-h window bounding the AR landfall date. More extreme precipitation amounts are produced by ARs in the South Cascades and Sierra Nevada ranges compared with ARs with landfall farther north. Most AR extreme precipitation events (and lower SWE accumulations) are produced during warm AR dates, especially toward the northern end of our domain. Analysis of ARs during dry and wet years reveals that ARs during wet years are more frequent and produce heavier precipitation and snow accumulation as compared with dry years. Such conditions are evident in drought events that are associated with a reduced frequency of ARs.

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

2012 ◽  
Vol 13 (3) ◽  
pp. 877-894 ◽  
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.

scholarly journals Discussing the role of tropical and subtropical moisture sources in cold season extreme precipitation events in the Mediterranean region from a climate change perspective

2016 ◽  
Vol 16 (1) ◽  
pp. 269-285 ◽  
Author(s):  
S. O. Krichak ◽  
S. B. Feldstein ◽  
P. Alpert ◽  
S. Gualdi ◽  
E. Scoccimarro ◽  
...  
Keyword(s):  
Climate Change ◽  
Extreme Precipitation ◽  
Mediterranean Region ◽  
Cold Season ◽  
Tropical Atlantic ◽  
Moist Air ◽  
Atmospheric Rivers ◽  
Extreme Precipitation Events ◽  
Precipitation Events

Abstract. This paper presents a review of a large number of research studies performed during the last few decades that focused on the investigation of cold season extreme precipitation events (EPEs) in the Mediterranean region (MR). The publications demonstrate the important role of anomalously intense transports of moist air from the tropical and subtropical Atlantic in the occurrence of EPEs in the MR. EPEs in the MR are directly or indirectly connected to narrow bands with a high concentration of moisture in the lower troposphere, i.e., atmospheric rivers, along which a large amount of moisture is transported from the tropics to midlatitudes. Whereas in a significant fraction of the EPEs in the western MR moisture is transported to the MR from the tropical Atlantic, EPEs in the central, and especially the eastern, MR are more often associated with intense tropical moisture transports over North Africa and the Red Sea. The moist air for the EPEs in the latter part of the MR also mainly originates from the tropical Atlantic and Indian oceans, and in many cases it serves as a temporary moisture reservoir for future development. The paper is supplemented by the results of a test for a possible connection between declining Arctic sea ice and the climatology of intense precipitation in the eastern MR. Based on the results of the evaluation supporting those from the earlier climate change analyses and modeling studies, it is concluded that a further anthropogenic global warming may lead a greater risk of higher rainfall totals and therefore larger winter floods in western and central parts of the MR as a consequence of stronger and more numerous Atlantic atmospheric rivers, possibly accompanied by a decline in the number of EPEs in the eastern part of the MR.

scholarly journals Paläoklimatologische Eindrücke aus Neuseeland

1965 ◽  
Vol 16 (1) ◽  
pp. 226-238
Author(s):  
Martin Schwarzbach
Keyword(s):  
New Zealand ◽  
Windward Side ◽  
Western Coast ◽  
Volcanic Area ◽  
The North ◽  
Long Time ◽  
Glacier Ice ◽  
Climatic History ◽  
The Difference ◽  
Wet Climate

Abstract. Some observations and remarks about the climate and paleoclimate of New Zealand, founded on journeys and the work of New Zealandic geologists. Some peculiarities of the climate (fig. 1). New Zealand has a relatively cool and wet climate (similar to Tasmania at the present). There is a very conspicious difference between the very humid windward side and the arid lee-side of the Southern Alps (also in the vegetation, fig. 2). „Edaphically caused deserts" begin to develop in the volcanic area of the North Island (fig. 3). The glaciers on the western coast of New Zealand (fig. 4), especially Franz Josef and Fox Glaciers, are impressive examples for the coexistence of lush, nearly subtropical rainforests (with tree-ferns) with glacier ice (figs. 6, 8). Therefore they are especially important for paleoclimatologists and for the interpretation of climatic indicators. Both glaciers have their tongues near the sea, nearly 2000 mts. below snow-line. Their recession (fig. 7) was 1200 and 1800 m respectively in 21 years. The cause for the low position of the tongues is to bee seen in high precipitation in connexion with the altitude and steepness of the mountains. Climatic history of New Zealand. The Quaternary is not treated; it only is referred to the influence of recent tectonic movements on the terraces. — The climate of the Tertiary was temperate to subtropical and humid. Maximal temperatures did not occur (as in Europe and North America) in the older, but (as in Australia) in the middle Tertiary (fig. 9). The author tries to explain this difference by the combination of 2 curves (fig. 10): one is the curve of changing latitude, caused by drift, the other is the general trend of the decline of temperature in Tertiary time. Because Australia obviously moved towards the equator, but Europe (if at all) towards the pole, the resulting curve is different in both continents. — Also the Mesozoic climate was neither tropical nor arid. Perhaps the Permian was a little warmer than in Australia. Compared with Australia, the climatic history is distinctly different. Australia changed from a polar climate to a subtropical and tropical one since the Carboniferous-Permian period, but New Zealand seems to have remained more or less in the same climatic zone during this long time. We don't yet know whether the difference between New Zealand and Australia is only apparent (caused by gaps in our knowledge), or is caused by an independent northward drift of both regions (Australia quickly, New Zealand more slowly).

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