12 research outputs found
On the assessment of the moisture transport by the Great Plains low-level jet
Low-level jets (LLJs) can be defined as wind corridors of anomalously high
wind speed values located within the first kilometre of the troposphere.
These structures are one of the major meteorological systems in the
meridional transport of moisture on a global scale. In this work, we focus on
the southerly Great Plains low-level jet, which plays an important role in
the moisture transport balance over the central United States. The Gulf of
Mexico is the main moisture source for the Great Plains low-level jet
(GPLLJ), which has been identified as a key factor for rainfall modulation
over the eastern and central US.
The relationship between moisture transport from the Gulf of Mexico to the
Great Plains and precipitation has been well documented in previous studies.
Nevertheless, a large uncertainty still remains in the quantification of the
moisture amount actually carried by the GPLLJ. The main goal of this work is
to address this question. For this purpose, a relatively new tool, the
regional atmospheric Weather Research and Forecasting Model with 3-D water
vapour tracers (WRF-WVT; Insua-Costa and Miguez-Macho, 2018) is used together
with the Lagrangian model FLEXPART to estimate the load of precipitable water
advected within the GPLLJ. Both models were fed with data from ERA Interim. From a climatology of jet intensity
over a 37-year period, which follows a Gaussian distribution, we select five
cases for study, representing the mean and 1 and 2 standard deviations above
and below it. Results show that the jet is responsible for roughly
70 %â80 % of the moisture transport occurring in the southern Great
Plains when a jet event occurs. Furthermore, moisture transport by the GPLLJ
extends to the north-east US, accounting for 50 % of the total in areas
near the Great Lakes. Vertical distributions show the maximum of moisture
advected by the GPLLJ at surface levels and maximum values of moisture flux
about 500 m above, in coincidence with the wind speed profile.</p
The concurrence of atmospheric rivers and explosive cyclogenesis in the North Atlantic and North Pacific basins
Abstract. The explosive cyclogenesis of extratropical cyclones and the occurrence of atmospheric rivers are characteristic features of a baroclinic atmosphere, and are both closely related to extreme hydrometeorological events in the mid-latitudes, particularly on coastal areas on the western side of the continents. The potential role of atmospheric rivers in the explosive cyclone deepening has been previously analysed for selected case studies, but a general assessment from the climatological perspective is still missing. Using ERA-Interim reanalysis data for 1979â2011, we analyse the concurrence of atmospheric rivers and explosive cyclogenesis over the North Atlantic and North Pacific basins for the extended winter months (ONDJFM). Atmospheric rivers are identified for almost 80âŻ% of explosive deepening cyclones. For non-explosive cyclones, atmospheric rivers are found only in roughly 40âŻ% of the cases. The analysis of the time evolution of the high values of water vapour flux associated with the atmospheric river during the cyclone development phase leads us to hypothesize that the identified relationship is the fingerprint of a mechanism that raises the odds of an explosive cyclogenesis occurrence and not merely a statistical relationship. These new insights on the relationship between explosive cyclones and atmospheric rivers may be helpful to a better understanding of the associated high-impact weather events
Tagging moisture sources with Lagrangian and inertial tracers: application to intense atmospheric river events
Two Lagrangian tracer tools are evaluated for studies on atmospheric
moisture sources and pathways. In these methods, a moisture volume is
assigned to each particle, which is then advected by the wind flow. Usual
Lagrangian methods consider this volume to remain constant and the particle
to follow flow path lines exactly. In a different approach, the initial
moisture volume can be considered to depend on time as it is advected by the
flow due to thermodynamic processes. In this case, the tracer volume drag
must be taken into account. Equations have been implemented and moisture
convection was taken into account for both Lagrangian and inertial models. We
apply these methods to evaluate the intense atmospheric rivers that
devastated (i) the Pacific Northwest region of the US and (ii) the western
Iberian Peninsula with flooding rains and intense winds in early
November 2006 and 20 May 1994, respectively. We note that the usual
Lagrangian method underestimates moisture availability in the continent, while
active tracers achieve more realistic results
Climatology of Lyapunov exponents: the link between atmospheric rivers and large-scale mixing variability
Large-scale tropospheric mixing and Lagrangian transport properties have been analyzed for the long-term period 1979â2014 in
terms of the finite-time Lyapunov exponents (FTLEs). Wind field reanalyses from the European Centre for Medium-Range
Weather Forecasts were used to calculate the Lagrangian trajectories of large ensembles of particles. Larger values of the
interannual and intra-annual mixing variabilities highlight the El Niño Southern Oscillation, the storm track, or the
Intertropical Convergence Zone among other large-scale structures. The mean baroclinic instability growth rate and the mean
atmospheric river occurrence show large correlation values with the FTLE climatology as an indication of their influence
on tropospheric mixing in the midlatitudes. As a case study, the role that land-falling atmospheric rivers have on
large-scale tropospheric mixing and the precipitation rates observed in Saharan Morocco and the British Isles
has
been analyzed. The atmospheric river contribution to tropospheric mixing is found to decrease from 15âŻ% in
Saharan Morocco to less than 5âŻ% for the UK and Ireland regions, in agreement with their contribution to precipitation that is
40âŻ% larger in the former than in the latter region
On the relationship between atmospheric rivers, weather types and floods in Galicia (NWÂ Spain)
Atmospheric rivers (ARs) â long and narrow structures of
anomalously high water vapor flux located in the warm sector of extratropical
cyclones â have been shown to be closely related to extreme
precipitation and flooding. In this paper we analyze the connection
between ARs and flooding in the northwestern Spanish region of
Galicia under a variety of synoptic conditions represented by the
so-called weather types, a classification of daily sea-level pressure
patterns obtained by means of a simple scheme that adopts the subjective
procedure of Lamb. Flood events are identified from official reports
conducted by the Spanish emergency management agency (Protección Civil) from 1979 to 2010. Our results suggest that, although most flood events in Galicia do not coincide with the presence of an overhead AR, ARs are present in the majority of severe cases, particularly in coastal areas. Flood events
associated with ARs are connected to cyclonic weather types with
westerly and southwesterly flows, which occur mostly
in winter months. The link between ARs and severe flooding is not very
apparent in inland areas or during summer months, in which case heavy
precipitation is usually not frontal in nature but rather
convective. Nevertheless, our results show that, in general, the amount of
precipitation in flood events in Galicia more than doubles when an AR is present
Evaluation of the moisture sources in two extreme landfalling atmospheric river events using an Eulerian WRF tracers tool
A new 3-D tracer tool is coupled to the WRF model to analyze the origin of
the moisture in two extreme atmospheric river (AR) events: the so-called
Great Coastal Gale of 2007 in the
Pacific Ocean and the Great Storm of
1987 in the North Atlantic. Results show that
between 80 and 90âŻ% of moisture advected by the ARs, and a high
percentage of the total precipitation produced by the systems have a
tropical origin. The tropical contribution to precipitation is in general
above 50âŻ% and largely exceeds this value in the most affected areas.
Local convergence transport is responsible for the remaining moisture and
precipitation. The ratio of tropical moisture to total moisture is maximized
as the cold front arrives on land. Vertical cross sections of the moisture
content suggest that the maximum in tropical humidity does not necessarily
coincide with the low-level jet (LLJ) of the extratropical cyclone. Instead,
the amount of tropical humidity is maximized in the lowest atmospheric level
in southern latitudes and can be located above, below or ahead of the LLJ
in northern latitudes in both analyzed cases
Running a Scientific Conference During Pandemic Times
Despite the COVID-19 pandemic, the science of atmospheric rivers was well served by the organization of a virtual symposium joined by more than 100 researchers. In addition to conveying new science, significant lessons were learned on how to run virtual events.Fil: Garreaud, RenĂ©. Universidad de Chile; ChileFil: Ralph, M.. University of California; Estados UnidosFil: Wilson, A.. University of California; Estados UnidosFil: Ramos, A. M.. Universidade de Lisboa; PortugalFil: Eiras Barca, J.. Universidad de Vigo; EspañaFil: Steen Larsen, H. C.. University of Bergen; NoruegaFil: Rutz, J.. Nws Western Region; Estados UnidosFil: Albano, C.. Desert Research Institute; Estados UnidosFil: Tilinina, N.. Russian Academy Of Sciences. Shirshov Institute of Oceanology; RusiaFil: Warner, M.. U.S. Army Corps of Engineers; Estados UnidosFil: Viale, Maximiliano. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Mendoza. Instituto Argentino de NivologĂa, GlaciologĂa y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de NivologĂa, GlaciologĂa y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de NivologĂa, GlaciologĂa y Ciencias Ambientales; ArgentinaFil: Rondanelli, R.. Universidad de Chile; ChileFil: McPhee, J.. Universidad de Chile; ChileFil: Valenzuela, R.. Universidad de O Higgins (uoh);Fil: Gorodetskaya, I.. Universidade de Aveiro; Portuga
Effects of Atmospheric Rivers
This book is intended to summarize the state of the science of atmospheric rivers (ARs) and itsapplication to practical decision-making and broader policy topics. It is the first book on thesubject and is intended to be a learning resource for professionals, students, and indeed anyonenew to the field, as well as a reference source for all.We first envisioned the book during the heady days of 2013 when the Center for WesternWeather and Water Extremes was being planned and established. However, right from the start,we recognized that the effort required would exceed that of any single or couple of authors, andthat the book would surely benefit from a broad range of perspectives and knowledge from avariety of leaders of atmospheric-river science from around the world. Consequently, the firststep toward this book was to organize workshops addressing various aspects of AR science thatwe were able to co-opt, in part, for recruitment of, and discussions among, possible contributingauthors. This led to the diverse authorship team that ultimately wrote this book, as well asour engagement of an experienced publication and book editing team. Among the strategiesagreed to by the contributing authors, one key decision was that the book would focus mostlyon results that have already been published and would emphasize figures and references fromthose formal publications. Where vital, new information has been developed and incorporated.Each chapter was led by a few expert lead authors recruited by the four of us, and those chapterleads recruited contributions from other experts on the chapter topic. Each chapter wasreviewed by other specialists who were not part of its authorship team, generally including onehighly technical expert and one reviewer intended to represent members of a broader audience.This helped ensure the accuracy of interpretations as well as high standards and accessibilityof presentation. We, the editors of the book, reviewed all chapters at various stages of compositionand layout.Given currently high levels of interest in ARs in the scientific community as well as by thepublic, we hope that the book will be a useful starting place for many readers. Writing a bookabout a topic that is as new and that is advancing as quickly as AR science is today (in 2018)poses many difficult challenges but, with the help of the large team of expert authors who havecontributed, we believe that, with this book, we are providing a firm foundation for futureexpansion and advances in this important field.Fil: Dettinger, Michael D.. United States Geological Survey; Estados UnidosFil: Lavers, David A.. No especifĂca;Fil: Compo, Gilbert P.. State University of Colorado at Boulder; Estados UnidosFil: Gorodetskaya, Irina V.. Universidade de Aveiro; PortugalFil: Neff, William. State University of Colorado at Boulder; Estados UnidosFil: Neiman, Paul J.. National Oceanic And Atmospheric Administration; Estados UnidosFil: Ramos, Alexandre M.. Universidade Nova de Lisboa; PortugalFil: Rutz, Jonathan J.. National Weather Service; Estados UnidosFil: Viale, Maximiliano. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Mendoza. Instituto Argentino de NivologĂa, GlaciologĂa y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de NivologĂa, GlaciologĂa y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de NivologĂa, GlaciologĂa y Ciencias Ambientales; ArgentinaFil: Wade, Andrew J.. University of Reading; Reino UnidoFil: White, Allen B.. National Oceanic And Atmospheric Administration; Estados Unido