scholarly journals Aerial Rivers and Lakes: Looking at Large-Scale Moisture Transport and Its Relation to Amazonia and to Subtropical Rainfall in South America

2012 ◽  
Vol 25 (2) ◽  
pp. 543-556 ◽  
Author(s):  
Josefina Moraes Arraut ◽  
Carlos Nobre ◽  
Henrique M. J. Barbosa ◽  
Guillermo Obregon ◽  
José Marengo
Keyword(s):  
South America ◽  
Moisture Transport ◽  
Large Scale ◽  
Precipitable Water ◽  
Trade Wind ◽  
Strong Increase ◽  
The North ◽  
The Andes ◽  
Dry Seasons ◽  
Southern Amazonia

Abstract This is an observational study of the large-scale moisture transport over South America, with some analyses on its relation to subtropical rainfall. The concept of aerial rivers is proposed as a framework: it is an analogy between the main pathways of moisture flow in the atmosphere and surface rivers. Opposite to surface rivers, aerial rivers gain (lose) water through evaporation (precipitation). The magnitude of the vertically integrated moisture transport is discharge, and precipitable water is like the mass of the liquid column—multiplied by an equivalent speed it gives discharge. Trade wind flow into Amazonia, and the north/northwesterly flow to the subtropics, east of the Andes, are aerial rivers. Aerial lakes are the sections of a moisture pathway where the flow slows down and broadens, because of diffluence, and becomes deeper, with higher precipitable water. This is the case over Amazonia, downstream of the trade wind confluence. In the dry season, moisture from the aerial lake is transported northeastward, but weaker flow over southern Amazonia heads southward toward the subtropics. Southern Amazonia appears as a source of moisture to this flow. Aerial river discharge to the subtropics is comparable to that of the Amazon River. The variations of the amount of moisture coming from Amazonia have an important effect over the variability of discharge. Correlations between the flow from Amazonia and subtropical rainfall are not strong. However, some months within the set of dry seasons observed showed a strong increase (decrease) occurring together with an important increase (decrease) in subtropical rainfall.

scholarly journals Lagrangian formation pathways of moist anomalies in the trade-wind region during the dry season: two case studies from EUREC<sup>4</sup>A

2021 ◽  
Author(s):  
Leonie Villiger ◽  
Heini Wernli ◽  
Maxi Boettcher ◽  
Martin Hagen ◽  
Franziska Aemisegger
Keyword(s):  
Long Range ◽  
North Atlantic ◽  
Large Scale ◽  
Cold Front ◽  
Trade Wind ◽  
Long Range Transport ◽  
The North ◽  
Range Transport ◽  
The North Atlantic ◽  
The Tropics

Abstract. Shallow clouds in the trade-wind region over the North Atlantic contribute substantially to the global radiative budget. In the vicinity of the Caribbean island Barbados, they appear in different mesoscale organisation patterns with distinct net cloud radiative effects (CRE). Cloud formation processes in this region are typically controlled by the prevailing large-scale subsidence. However, occasionally weather systems from remote origin cause significant disturbances. This study investigates the complex cloud-circulation interactions during the field campaign EUREC4A (Elucidate the Couplings Between Clouds, Convection and Circulation) from 16 January to 20 February 2020, using a combination of Eulerian and Lagrangian diagnostics. Based on observations and ERA5 reanalyses, we identify the relevant processes and characterise the formation pathways of two moist anomalies above the Barbados Cloud Observatory (BCO), one in the lower (~1000–650 hPa) and one in the middle troposphere (~650–300 hPa). These moist anomalies are associated with strongly negative CRE values and with contrasting long-range transport processes from the extratropics and the tropics, respectively. The low-level moist anomaly is characterised by an unusually thick cloud layer, high precipitation totals and a strongly negative CRE. Its formation is connected to an “extratropical dry intrusion” (EDI) that interacts with a trailing cold front. A quasi-climatological (2010–2020) analysis reveals that EDIs lead to different conditions at the BCO depending on how they interact with the associated cold front. Based on this climatology, we discuss the relevance of the strong large-scale forcing by EDIs for the low-cloud patterns near the BCO and the related CRE. The second case study about the mid-tropospheric moist anomaly is associated with an extended and persistent mixed-phase shelf cloud and the lowest daily CRE value observed during the campaign. Its formation is linked to “tropical mid-level detrainment” (TMD), which refers to detrainment from tropical deep convection near the melting layer. The quasi-climatological analysis shows that TMDs consistently lead to mid-tropospheric moist anomalies over the BCO and that the detrainment height controls the magnitude of the anomaly. However, no systematic relationship was found between the amplitude of this mid-tropospheric moist anomaly and the CRE at the BCO. Overall, this study reveals the important impact of the long-range transport, driven by dynamical processes either in the extratropics or the tropics, on the variability of the vertical structure of moisture and clouds, and on the resulting CRE in the North Atlantic winter trades.

Quantifying the interplay of clouds and their environment through an energetic lens during EUREC4A

2021 ◽  
Author(s):  
Anna Lea Albright ◽  
Sandrine Bony ◽  
Bjorn Stevens ◽  
Raphaela Vogel
Keyword(s):  
Large Scale ◽  
Hydrological Cycle ◽  
Trade Wind ◽  
Energy Budgets ◽  
Moist Static Energy ◽  
Radiative Effect ◽  
The North ◽  
Cloud Radiative Effect ◽  
Moist Static Energy Budget ◽  
Static Energy

&lt;p&gt;The trades form an important link in the atmospheric energy supply, transporting moisture and momentum to the deep tropics and influencing the global hydrological cycle.&amp;#160;Trade-wind cumuli are the most ubiquitous cloud type over tropical oceans, yet models disagree in simulating their response to warming.&amp;#160;Our study takes advantage of extensive in-situ soundings performed&amp;#160;during the EUREC4A campaign, which took place in the downstream&amp;#160;trades of the North Atlantic in winter 2020. We employ 1068&amp;#160;dropsondes&amp;#160;made in a ca. 2deg x 2deg area&amp;#160;to&amp;#160;close the moisture and energy budgets of the subcloud layer and atmospheric column. Our motivation for closing moisture and energy budgets using EUREC4A data is two-fold. First, we try to understand which large-scale environmental factors control&amp;#160;variability in subcloud layer moisture and moist static energy, given their influence on setting convective potential.&amp;#160;Second,&amp;#160;we quantify the interplay between clouds and their environment through an energetic lens. The&amp;#160;cloud radiative effect emerges as a residual from the total column moist static energy budget,&amp;#160;yielding an energetic estimate of clouds. We quantify how this cloud radiative effect compares with coincident satellite and geometric (i.e. cloud fraction) estimates of cloudiness,&amp;#160;varies on different scales, and relates to large-scale environmental conditions.&lt;/p&gt;

scholarly journals Precipitable water characteristics during the 2013 Colorado flood using ground-based GPS measurements

2017 ◽  
Vol 10 (11) ◽  
pp. 4055-4066 ◽  
Author(s):  
Hannah K. Huelsing ◽  
Junhong Wang ◽  
Carl Mears ◽  
John J. Braun
Keyword(s):  
United States ◽  
Moisture Transport ◽  
Large Scale ◽  
Precipitable Water ◽  
Tropical Eastern Pacific ◽  
Public And Private ◽  
Maximum Rainfall ◽  
Water Characteristics ◽  
Synoptic Features ◽  
Saturated Atmosphere

Abstract. During 9–16 September 2013, the Front Range region of Colorado experienced heavy rainfall that resulted in severe flooding. Precipitation totals for the event exceeded 450 mm, damages to public and private properties were estimated to be over USD 2 billion, and nine lives were lost. This study analyzes the characteristics of precipitable water (PW) surrounding the event using 10 years of high-resolution GPS PW data in Boulder, Colorado, which was located within the region of maximum rainfall. PW in Boulder is dominated by seasonal variability with an average summertime maximum of 36 mm. In 2013, the seasonal PW maximum extended into early September and the September monthly mean PW exceeded the 99th percentile of climatology with a value 25 % higher than the 40-year climatology. Prior to the flood, around 18:00 UTC on 8 September, PW rapidly increased from 22 to 32 mm and remained around 30 mm for the entire event as a result of the nearly saturated atmosphere. The frequency distribution of September PW for Boulder is typically normal, but in 2013 the distribution was bimodal due to a combination of above-average PW values from 1 to 15 September and much drier conditions from 16 to 30 September. The above-normal, near-saturation PW values during the flood were the result of large-scale moisture transport into Colorado from the Tropical Eastern Pacific and the Gulf of Mexico. This moisture transport was the product of a stagnating cutoff low over the southwestern United States working in conjunction with an anticyclone located over the southeastern United States. A blocking ridge located over the Canadian Rocky Mountains kept both of the synoptic features in place over the course of several days, which helped to provide continuous moisture to the storm, thus enhancing the accumulated precipitation totals.

scholarly journals Synoptic and Mesoscale atmospheric features associated with an extreme Snowstorm over the Central Andes in August 2013

2019 ◽  
Author(s):  
Marcelo Zamuriano ◽  
Paul Froidevaux ◽  
Isabel Moreno ◽  
Mathias Vuille ◽  
Stefan Brönnimann
Keyword(s):  
Spatial Distribution ◽  
Snow Cover ◽  
Rossby Wave ◽  
Moisture Transport ◽  
Large Scale ◽  
Amazon Basin ◽  
Cold Front ◽  
Wave Train ◽  
Pressure System ◽  
The Andes

Abstract. We study the synoptic and mesoscale characteristics of a snowfall event over the Bolivian Altiplano in August 2013 that caused severe damage to people, infrastructure and livestock. This event was associated with a cold front episode following the eastern slope of the Andes-Amazon interface and a cut-off low pressure system (COL) over the Pacific Ocean. Large scale analyses suggest a two-stage mechanism: The first phase consisted of a strong cold surge to the east of the Andes inducing low level blocking of southward moisture transport over the SW Amazon basin due to post-frontal high-pressure up to 500 hPa synchronized to a Rossby wave train. The second stage was initiated by the displacement of 500 hPa anticyclone over the Andes due to a Rossby wave passage and a subsequent increase in north-easterly moisture transport, while another cold front along the eastern Andes provided additional lifting. We analyse an analog event (July 2010) to confirm the influence of these large-scale features on snow formation. We conduct a mesoscale analysis using the Weather Research and Forecasting (WRF-ARW) model. For this purpose, we perform a series of high-resolution numerical experiments that include sensitivity studies where we apply orographic and lake Titicaca temperature modifications. We compare our findings to MODIS snow cover estimates and in-situ measurements. The control simulation is able to capture the snow cover spatial distribution and sheds light over several aspects of the snowfall dynamics. In our WRF simulations, daytime snowfall mainly occurs around complex orography whereas nocturnal snowfall is concentrated over the plateau due to a combination of nocturnal winds and complex orography inside the plateau. The sensitivity experiments indicate the importance of the lake and mountain for thermal wind circulation affecting the spatial distribution of snowfall by shifting the position of the convergence zones. The influence of the lake's thermal effect is not evident around the regions surrounding the lake.

scholarly journals Precipitable Water Characteristics during the 2013 Colorado Flood using Ground-Based GPS Measurements

2017 ◽  
Author(s):  
Hannah K. Huelsing ◽  
Junhong Wang ◽  
Carl Mears ◽  
John J. Braun
Keyword(s):  
United States ◽  
Moisture Transport ◽  
Large Scale ◽  
Precipitable Water ◽  
Front Range ◽  
Public And Private ◽  
Maximum Rainfall ◽  
Water Characteristics ◽  
Synoptic Features ◽  
Saturated Atmosphere

Abstract. During 9th–16th September 2013, the Front Range region of Colorado experienced heavy rainfall that resulted in severe flooding. Precipitation totals for the event exceeded 450 mm, damages to public and private properties were estimated to be over $ 2 billion, and nine lives were lost. This study analyzes the characteristics of precipitable water (PW) surrounding the event using 10 years of high-resolution GPS PW data in Boulder, Colorado, which was located within the region of maximum rainfall. PW in Boulder is dominated by seasonal variability with an average summertime maximum of 36 mm. In 2013, the seasonal PW maximum extended into early September and the September monthly mean PW exceeded the 99th percentile of climatology with a value 25 % higher than the 40 year climatology. Prior to the flood, around 18 UTC on 8 September, PW rapidly increased from 22 mm to 32 mm and remained around 30 mm for the entire event as a result of the nearly saturated atmosphere. The frequency distribution of September PW for Boulder is typically normal, but in 2013 the distribution was bimodal due to a combination of above average PW values from September 1st–15th and much drier conditions from 16th–30th September. The above normal, near saturation PW values during the flood were the result of large-scale moisture transport into Colorado from the eastern tropical Pacific and the Gulf of Mexico. This moisture transport was the product of a stagnating, cutoff low over the southwestern United States working in conjunction with an anticyclone located over the southeastern United States. A blocking ridge located over the Canadian Rocky Mountains kept both of the synoptic features in place over the course of several days, which helped to provide continuous moisture to the storm, thus enhancing the accumulated precipitation totals.

scholarly journals Moisture origin, transport pathways, and driving processes of intense wintertime moisture transport into the Arctic

2021 ◽  
Author(s):  
Lukas Papritz ◽  
David Hauswirth ◽  
Katharina Hartmuth
Keyword(s):  
North Atlantic ◽  
Moisture Transport ◽  
Large Scale ◽  
The Arctic ◽  
Polar Cap ◽  
Transport Pathways ◽  
Moisture Sources ◽  
The North ◽  
Total Transport ◽  
Air Streams

Abstract. Poleward moisture transport occurs in episodic, high-amplitude events with strong impacts on the Arctic and its climate system components such as sea ice. This study focuses on the origin of such events and examines the moisture sources, moisture transport pathways, and their linkage to the large-scale circulation. For that purpose, 597 events of intense zonal mean poleward moisture transport at 70° N (exceeding the 90th anomaly percentile) are identified and kinematic backward trajectories from 70° N are computed to pinpoint the moisture sources and characterize the air-streams accomplishing the transport. The bulk of the moisture transported into the polar cap during these events originates in the eastern North Atlantic with an uptake maximum poleward of 50° N. This asymmetry between ocean basins is a direct consequence of the fact that most of the moisture transport into the polar cap occurs in this sector. As a result of the fairly high-latitude origin of the moisture, the median time moisture spends in the atmosphere prior to reaching 70° N amounts to about 2.5 days. Trajectories further reveal an inverse relationship between moisture uptake latitude and the level at which moisture is injected into the polar cap, consistent with ascent of poleward flowing air in a baroclinic atmosphere. Focusing on events for which 75 % of the zonal mean moisture transport takes place in the North Atlantic east of Greenland (424 events) reveals that lower tropospheric moisture transport results predominantly from two types of air-streams: (i) cold, polar air advected from the Canadian Arctic over the North Atlantic and around Greenland, whereby the air is warmed and moistened by surface fluxes, and (ii) air subsiding from the mid-troposphere into the boundary layer. Both air-streams contribute about 36 % each to the total transport. The former dominates the moisture transport during events associated with an anomalously high frequency of cyclones east of Greenland (218 events), whereas the latter is more important in the presence of atmospheric blocking over Scandinavia and the Ural (145 events). A substantial portion of the moisture sources associated with both types of air-streams are located between Iceland, the British Isles, and Norway. Long-range moisture transport, accounting for 17 % of the total transport, is the dominant type of air-stream during events with weak forcing by baroclinic weather systems (64 events). Finally, mid-tropospheric moisture transport is invariably associated with (diabatically) ascending air and moisture origin in the central and western North Atlantic, including the Gulf Stream front, accounting for roughly 10 % of the total transport. In summary, our study reveals that moisture injections into the polar atmosphere are not primarily caused by the poleward transport of warm and humid air from low latitudes – a conclusion that applies in particular to cases where the transport is driven by baroclinic weather systems such as extratropical cyclones. Instead, it results from a combination of air-streams with pre-dominantly high-latitude or high-altitude origin and their interplay with large-scale weather systems (e.g., cyclones, blocks).

scholarly journals Probing Regional Orographic Controls of Precipitation and Cloudiness in the Central Andes Using Satellite Data

2009 ◽  
Vol 10 (1) ◽  
pp. 167-182 ◽  
Author(s):  
Jason P. Giovannettone ◽  
Ana P. Barros
Keyword(s):  
Moisture Transport ◽  
Large Scale ◽  
Tropical Rainfall Measuring Mission ◽  
Space Time ◽  
Cloud Formation ◽  
Time Variability ◽  
Brightness Temperatures ◽  
The Andes ◽  
Precipitation Regimes ◽  
One Year

Abstract Data obtained from NOAA’s Geostationary Operational Environmental Satellite (GOES) and NASA’s Tropical Rainfall Measuring Mission (TRMM) satellites were used to investigate the relationships between topography, large-scale circulation, and the climatology of precipitation and cloudiness in the Andes—specifically over Peru and the Altiplano Plateau—at diurnal, seasonal, and interannual time scales. The spatial variability of cloudiness was assessed through empirical orthogonal function (EOF) analysis of GOES brightness temperatures. Results indicate that landform is the principal agent of the space–time variability of moist atmospheric processes in the Andes, with the first mode explaining up to 70% of all observed variability. These results substantiate the differences between “continental” (Andes and Himalayas) and “maritime” (Western Cordillera) orographic precipitation regimes, reflecting the degree to which upwind landmasses modulate moisture transport toward and across mountain barriers. GOES brightness temperatures show that afternoon convective activity during the rainy season is more intense on wet hydrometeorological years such as 2001, whereas the space–time structure of nighttime cloudiness at the foothills and outlets of deep interior valleys does not change during the monsoon and from one year to another independently of large-scale conditions. This suggests that daytime cloud formation and precipitation is strongly dependent on large-scale moisture transport. Interactions between mesoscale and ridge–valley circulations, which are locked to the topography, determine the space–time organization of clouds and precipitation at nighttime. This leads to strong clustering of precipitation features associated with enhanced convection at high elevations along the ridges and near the headwaters of the major river systems in the TRMM data.

Extreme Summer Convection in South America

2010 ◽  
Vol 23 (14) ◽  
pp. 3761-3791 ◽  
Author(s):  
Ulrike Romatschke ◽  
Robert A. Houze
Keyword(s):  
South America ◽  
Amazon Basin ◽  
Three Dimensional ◽  
Tropical Rainfall Measuring Mission ◽  
Central Andes ◽  
South Atlantic Convergence Zone ◽  
Reanalysis Data ◽  
The North ◽  
The Andes ◽  
Environmental Prediction

Abstract Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) and National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) reanalysis data are used to indicate mechanisms responsible for extreme summer convection over South America. The three-dimensional reflectivity field is analyzed to define three types of extreme echo, deep convective cores, wide convective cores, and broad stratiform regions. The location and timing of these echoes are sensitive to midlatitude synoptic disturbances crossing the Andes. At the leading edges of these disturbances the nocturnal South American low-level jet (SALLJ) transports moisture along the eastern edge of the Andes from the tropical to the subtropical part of the continent. Where the SALLJ rises over lower but steep mountains on the east side of the southern central Andes, deep and wide convective cores are triggered in the evening. When the SALLJ withdraws to the north as the disturbance passes, nocturnal triggering occurs in the northeastern foothills of the central Andes. Extreme convection over the Amazon basin takes the form of broad stratiform regions that evolve from systems with wide convective cores moving into the center of the region from both the southwest and northeast. The systems from the northeast form at the northeast coast and are likely squall lines. Along the coast of the Brazilian Highlands, diurnal/topographic forcing leads to daytime maxima of deep convective cores followed a few hours later by wide convective cores. Wide convective cores and broad stratiform regions form in the South Atlantic convergence zone (SACZ) with a diurnal cycle related to continental heating.

scholarly journals Climatic changes between 20th century and pre-industrial times over South America in regional model simulations

2011 ◽  
Vol 7 (5) ◽  
pp. 2981-3022 ◽  
Author(s):  
S. Wagner ◽  
I. Fast ◽  
F. Kaspar
Keyword(s):  
South America ◽  
20Th Century ◽  
Large Scale ◽  
Climate Model ◽  
Climatic Changes ◽  
Andes Mountains ◽  
Model Simulations ◽  
The Andes ◽  
Paraná Basin ◽  
Parana Basin

Abstract. Two simulations with a regional climate model are analyzed for climatic changes between the late 20th century and a pre-industrial period over central and southern South America. The model simulations have been forced with large-scale boundary data from the global simulation performed with a coupled atmosphere-ocean general circulation model. The regional simulations have been carried out on a 0.44° × 0.44° grid (approx. 50 km × 50 km horizontal resolution). The differences in the external forcings are related to a changed greenhouse gas content of the atmosphere, being higher in the present-day simulation. For validation purposes the climate model is analyzed using a five year long simulation between 1993 and 1997 forced with re-analysis data. The climate model reproduces the main climatic features reasonably well, especially when comparing model output co-located with observational station data. However, the comparison between observed and simulated climate is hampered by the sparse meteorological station network in South America. The present-day simulation is compared with the pre-industrial simulation for atmospheric fields of near-surface temperatures, precipitation, sea level pressure and zonal wind. Higher temperatures in the present-day simulation are evident over entire South America, mostly pronounced over the southern region of the Andes Mountains and the Parana basin. During southern winter the higher temperatures prevail over the entire continent, with largest differences over the central Andes Mountains and the Amazonian basin. Precipitation differences show a more heterogeneous pattern, especially over tropical regions. This might be explained by changes in convective processes acting on small scales. During southern summer wetter conditions are evident over the Amazonian and Parana basin in the present-day simulation. Precipitation increases are evident over Patagonia together with decreases to the north along the western slope of the Andes Mountains. During southern winter also a dipole pattern along the Andes Mountains with wetter conditions over the southern parts and drier conditions over the central parts is evident. An interesting feature relates to precipitation changes with changing sign within a few 10th of kilometers along the southern parts of the Andes mountain chain. This pattern can be explained by changes in large-scale circulation related to latitudinal changes of the extratropical southern hemispheric westerlies.

scholarly journals A ghost in the mist: extension of the known range of Colombian Weasel, Neogale felipei (Izor & de la Torre, 1978) (Carnivora, Mustelidae), in the Cordillera Occidental

Check List ◽  
2021 ◽  
Vol 17 (5) ◽  
pp. 1359-1364
Author(s):  
Juan C. Cepeda-Duque ◽  
Andrés Link ◽  
Luis Mazariegos ◽  
Elver Ledesma-Castañeda ◽  
Uriel Rendón-Jaramillo ◽  
...  
Keyword(s):  
Natural History ◽  
South America ◽  
The North ◽  
The Andes ◽  
Natural Reserve ◽  
Trail Camera

The Colombian weasel, Neogale felipei (Izor &amp; de la Torre, 1978), is one of the most enigmatic and threatened carnivores in South America, with only six confirmed records in the Andes of Ecuador and Colombia. During a long-term trail camera survey conducted at Mesenia-Paramillo Natural Reserve, we recorded the northernmost occurrence of the species, which extends its distribution by approximately 120 km to the north from the nearest previously known locality in Colombia. We also provide some comments on its natural history.

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