scholarly journals Atmospheric conditions associated with oceanic convection in the south-east Labrador Sea

2008 ◽  
Vol 35 (6) ◽  
Author(s):  
David A. J. Sproson ◽  
Ian A. Renfrew ◽  
Karen J. Heywood
Keyword(s):  
Labrador Sea ◽  
Atmospheric Conditions ◽  
The South ◽  
Oceanic Convection

scholarly journals Atmospheric Conditions Associated with Labrador Sea Deep Convection: New Insights from a Case Study of the 2006/07 and 2007/08 Winters

2016 ◽  
Vol 29 (14) ◽  
pp. 5281-5297 ◽  
Author(s):  
Who M. Kim ◽  
Stephen Yeager ◽  
Ping Chang ◽  
Gokhan Danabasoglu
Keyword(s):  
North America ◽  
North Atlantic ◽  
Large Scale ◽  
Initial Conditions ◽  
Deep Convection ◽  
La Niña ◽  
Labrador Sea ◽  
Atmospheric Conditions ◽  
Circulation Anomaly ◽  
La Nina

Abstract Deep convection in the Labrador Sea (LS) resumed in the winter of 2007/08 under a moderately positive North Atlantic Oscillation (NAO) state. This is in sharp contrast with the previous winter with weak convection, despite a similar positive NAO state. This disparity is explored here by analyzing reanalysis data and forced-ocean simulations. It is found that the difference in deep convection is primarily due to differences in large-scale atmospheric conditions that are not accounted for by the conventional NAO definition. Specifically, the 2007/08 winter was characterized by an atmospheric circulation anomaly centered in the western North Atlantic, rather than the eastern North Atlantic that the conventional NAO emphasizes. This anomalous circulation was also accompanied by anomalously cold conditions over northern North America. The controlling influence of these atmospheric conditions on LS deep convection in the 2008 winter is confirmed by sensitivity experiments where surface forcing and/or initial conditions are modified. An extended analysis for the 1949–2009 period shows that about half of the winters with strong heat losses in the LS are associated with such a west-centered circulation anomaly and cold conditions over northern North America. These are found to be accompanied by La Niña–like conditions in the tropical Pacific, suggesting that the atmospheric response to La Niña may have a strong influence on LS deep convection.

Atmospheric forcing of coastal polynyas in the south-western Weddell Sea

2015 ◽  
Vol 27 (4) ◽  
pp. 388-402 ◽  
Author(s):  
Verena Haid ◽  
Ralph Timmermann ◽  
Lars Ebner ◽  
Günther Heinemann
Keyword(s):  
Sea Ice ◽  
Large Scale ◽  
Reanalysis Data ◽  
Ocean Model ◽  
Weddell Sea ◽  
Small Scale ◽  
Atmospheric Conditions ◽  
Atmospheric Forcing ◽  
The South ◽  
Ice Production

AbstractThe development of coastal polynyas, areas of enhanced heat flux and sea ice production strongly depend on atmospheric conditions. In Antarctica, measurements are scarce and models are essential for the investigation of polynyas. A robust quantification of polynya exchange processes in simulations relies on a realistic representation of atmospheric conditions in the forcing dataset. The sensitivity of simulated coastal polynyas in the south-western Weddell Sea to the atmospheric forcing is investigated with the Finite-Element Sea ice-Ocean Model (FESOM) using daily NCEP/NCAR reanalysis data (NCEP), 6 hourly Global Model Europe (GME) data and two different hourly datasets from the high-resolution Consortium for Small-Scale Modelling (COSMO) model. Results are compared for April to August in 2007–09. The two coarse-scale datasets often produce the extremes of the data range, while the finer-scale forcings yield results closer to the median. The GME experiment features the strongest winds and, therefore, the greatest polynya activity, especially over the eastern continental shelf. This results in higher volume and export of High Salinity Shelf Water than in the NCEP and COSMO runs. The largest discrepancies between simulations occur for 2008, probably due to differing representations of the ENSO pattern at high southern latitudes. The results suggest that the large-scale wind field is of primary importance for polynya development.

scholarly journals Extreme storm surges in the south of Brazil: atmospheric conditions and shore erosion

2009 ◽  
Vol 57 (3) ◽  
pp. 175-188 ◽  
Author(s):  
Cláudia Klose Parise ◽  
Lauro Júlio Calliari ◽  
Nisia Krusche
Keyword(s):  
Sea Level ◽  
Storm Surges ◽  
Weather Conditions ◽  
Reanalysis Data ◽  
Beach Erosion ◽  
Storm Events ◽  
Atmospheric Conditions ◽  
The South ◽  
Level Elevation ◽  
South Of Brazil

The region under study is regularly subject to the occurrence of storms associated with frontal systems and extratropical cyclones, since it is located near one of the cyclogenetic regions in South America. These storms can generate storm surges that cause anomalous high sea level rises on Cassino Beach. The use of reanalysis data along with an efficient technique for the location of the cyclone, using a vorticity threshold, has provided a new classification based upon the trajectories of events that produce positive sea level variation. Three patterns have been identified: 1) Cyclogenesis to the south of Argentina with displacement to the east and a trajectory between 47.5ºS and 57.5ºS; 2) Cyclogenesis to the south of Uruguay with displacement to the east and a trajectory between 35ºS and 42.5ºS; and 3) Cyclogenesis to the south of Uruguay with displacement to the southeast and a trajectory between 35ºS and 57.5ºS. Maximum water level elevation above the mean sea level and beach erosion were associated, respectively, with winter and summer storms. Cassino beach displayed a seasonal morphological behavior, with short periods of episodic erosion associated with winter storm events followed by long periods of accretion characterized by the dominance of fair weather conditions.

scholarly journals The Methods of Locating Areas Exposed to Wind Erosion in the South Moravia Region

2015 ◽  
Vol 63 (1) ◽  
pp. 113-121 ◽  
Author(s):  
Jana Podhrázská ◽  
Josef Kučera ◽  
Hana Středová
Keyword(s):  
Wind Erosion ◽  
Climatic Conditions ◽  
Soil Conditions ◽  
Atmospheric Conditions ◽  
The South ◽  
Spatial Function ◽  
Forest Belts ◽  
Protective Forest ◽  
South Moravia ◽  
The Impact

The conditions for the development of wind erosion are determined by the soil and climatic conditions as well as by the presence or absence of wind barriers. It is because of its climatic and soil conditions that the territory of the South Moravia Region has been affected by erosion for centuries. Combined with the atmospheric conditions, the dry and warm climate enables the development of aeolian processes both in light, drying soils and – under certain climatic conditions – in heavy, clay-loam soils. Soil erosion exposure maps have been prepared in order to identify the territories which are potentially exposed to wind erosion in terms of the soil and climatic conditions. Six exposure categories have been applied to the soils. However, the impact of permanent vegetation barriers – line elements – must be considered in order to identify the most exposed areas. Protective forest belts were planted in the 1950s to counter the effects of wind erosion and they are included in the database of the Institute for Economic Forest Management. The network of these wind barriers and the heath condition of the individual elements are often unsatisfactory because of poor maintenance. The purpose of the study was to evaluate the spatial function of the network of protective forest belts using the map of the potential exposure of soil in the Region of South Moravia. The method used to evaluate the spatial function of the windbreaks presented in the study using GIS instruments.

scholarly journals Position of the South Atlantic Anticyclone and Its Impact on Surface Conditions across Brazil

2018 ◽  
Vol 57 (3) ◽  
pp. 535-553 ◽  
Author(s):  
Joshua M. Gilliland ◽  
Barry D. Keim
Keyword(s):  
Wind Speed ◽  
Sea Level ◽  
Surface Wind ◽  
South Atlantic ◽  
Atmospheric Conditions ◽  
Southern Brazil ◽  
The South ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
Northern Brazil

AbstractThis study examines the surface wind characteristics of Brazil on the basis of the location of the maximum high pressure center in the South Atlantic basin (SAB), known as the South Atlantic anticyclone (SAA), from three reanalysis datasets for the period of 1980–2014. Linear wind speed trends determined for Brazil are geographically related to surface and macroscale atmospheric conditions found in the SAB. The daily mean position of the SAA exhibited a latitudinal poleward shift for all seasons, and a longitudinal trend was dependent upon extratropical activity found in the SAB. Results also show that wind speed and sea level pressure for northern Brazil are dependent upon the latitudinal position of the SAA. Consequently, surface wind correlations for southern Brazil tend to be related to changes in the longitudinal position of the SAA, which result from transient anticyclones migrating over the SAB. An examination of positive and negative wind anomalies shows that shifts in the position of the SAA are coupled with changes in sea level pressure for northern Brazil and air temperature for southern Brazil. From these findings, a surface wind analysis was performed to demonstrate how the geographical location of the SAA affects wind speed anomalies across Brazil and the SAB. Results from this study can assist in understanding how atmospheric systems change within the SAB so that forthcoming socioeconomic and climate-related causes of wind for the country of Brazil can be known.

scholarly journals The Nature of a Heat Wave in Eastern Argentina Occurring during SALLJEX

2007 ◽  
Vol 135 (3) ◽  
pp. 1165-1174 ◽  
Author(s):  
S. Bibiana Cerne ◽  
Carolina S. Vera ◽  
Brant Liebmann
Keyword(s):  
South America ◽  
Heat Wave ◽  
Strong Impact ◽  
South American ◽  
Atmospheric Conditions ◽  
The South ◽  
Low Level ◽  
Central Argentina ◽  
Temperature Advection ◽  
Low Level Jet

Abstract This note describes the physical processes associated with the occurrence of a heat wave over central Argentina during the austral summer of 2002/03, during which the South American Low-Level Jet Experiment (SALLJEX) was carried out. The SALLJEX heat wave that lasted between 25 January and 2 February 2003 was punctuated by extreme conditions during its last 3 days, with the highest temperature recorded over the last 35 yr at several stations of the region. It was found that not only the activity of synoptic-scale waves, but also the intraseasonal oscillation variability, had a strong impact on the temperature evolution during this summer. During the weeks previous to the heat wave development, an intensified South Atlantic convergence zone (SACZ) dominated the atmospheric conditions over tropical South America. Temperatures started to increase in the subtropics due to the subsidence and diabatic warming associated with the SACZ, as depicted by SALLJEX upper-air observations. An extratropical anticyclone that evolved along southern South America further intensified subsidence conditions. By the end of January the warming processes associated with SACZ activity weakened, while horizontal temperature advection began to dominate over central Argentina due to the intensification of the South American low-level jet. This mechanism led to temperature extremes by 2 February with temperature anomalies at least two standard deviations larger than the climatological mean values. Intense solar heating favored by strong subsidence was responsible for the heat wave until 31 January, after which horizontal temperature advection was the primary process associated with the temperature peak.

scholarly journals Circulation and Transport in the Western Boundary Currents at Cape Farewell, Greenland

2009 ◽  
Vol 39 (8) ◽  
pp. 1854-1870 ◽  
Author(s):  
N. P. Holliday ◽  
S. Bacon ◽  
J. Allen ◽  
E. L. McDonagh
Keyword(s):  
Water Transport ◽  
Deep Water ◽  
Flow Direction ◽  
Labrador Sea ◽  
Western Boundary ◽  
Boundary Current ◽  
The South ◽  
Western Boundary Currents ◽  
Boundary Currents ◽  
Irminger Sea

Abstract The circulation and volume transports in the western boundary currents around Cape Farewell, Greenland, are derived from full-depth hydrographic and velocity measurements from August–September 2005. The western boundary currents from surface to seafloor transport 40.5 ± 8.1 Sv (Sv ≡ 106 m3 s−1) southward in the Irminger Sea, and 53.8 ± 10.8 Sv northward in the Labrador Sea. The Deep Western Boundary Current (DWBC, defined as water with potential density greater than 27.80 kg m−3) transports 12.3 ± 2.5 Sv southward in the Irminger Sea. The deep water transport is reduced south of Cape Farewell, where it changes flow direction from southward to northward (the south corner). At a section over the Eirik Ridge, a bathymetric feature extending southwest of Cape Farewell, the DWBC transports 8.7 ± 1.7 Sv westward. The reduction in transport at the south corner is associated with decreased velocities within the deepest layers and the volumetric loss of the most saline deep water types. The observations suggest that the paths of the shallow and deep western boundary currents diverge at the south corner. Downstream in the eastern Labrador Sea the deep water transport is increased to 19.7 ± 3.9 Sv northward, with the addition of recirculating denser deep waters. The representativeness of the results from the semisynoptic survey is discussed with reference to companion current meter measurements of the DWBC.

scholarly journals BICEP: a cosmic microwave background polarization telescope at the South Pole

2009 ◽  
Vol 5 (H15) ◽  
pp. 618-619
Author(s):  
Yuki D. Takahashi
Keyword(s):  
Cosmic Microwave Background ◽  
Gravitational Waves ◽  
San Diego ◽  
South Pole ◽  
Polarization Anisotropy ◽  
Atmospheric Conditions ◽  
The South ◽  
Microwave Background ◽  
Cmb Polarization ◽  
Cosmic Microwave Background Polarization

AbstractBicep was a telescope designed to probe the polarization of the cosmic microwave background (CMB) for the signature of gravitational waves produced during the epoch of inflation. The instrument was developed by a team of scientists from Caltech/JPL, UC Berkeley, and UC San Diego. It was installed at the South Pole in November 2005 and the CMB observations were conducted from February to November each year with one winter-over scientist responsible for operating and maintaining the instrument. Taking advantage of the excellent atmospheric conditions at the South Pole, we mapped 2% of the sky at 100 and 150 GHz. We completed 3 years of observations from 2006 to 2008, mapping the CMB polarization anisotropy at degree angular scales with unprecedented sensitivity. In 2010, a next generation instrument, Bicep2, will be installed on the existing telescope mount for an even deeper survey.

Diagnosis of Local Land–Atmosphere Feedbacks in India

2011 ◽  
Vol 24 (1) ◽  
pp. 251-266 ◽  
Author(s):  
O. A. Tuinenburg ◽  
R. W. A. Hutjes ◽  
C. M. J. Jacobs ◽  
P. Kabat
Keyword(s):  
Soil Moisture ◽  
Land Surface ◽  
The United States ◽  
Monsoon Onset ◽  
Convective Precipitation ◽  
Onset Date ◽  
Positive Trend ◽  
Precipitation Trend ◽  
Atmospheric Conditions ◽  
The South

Abstract Following the convective triggering potential (CTP)–humidity index (HIlow) framework by Findell and Eltahir, the sensitivity of atmospheric convection to soil moisture conditions is studied for India. Using the same slab model as Findell and Eltahir, atmospheric conditions in which the land surface state affects convective precipitation are determined. For India, CTP–HIlow thresholds for land surface–atmosphere feedbacks are shown to be slightly different than for the United States. Using atmospheric sounding data from 1975 to 2009, the seasonal and spatial variations in feedback strength have been assessed. The patterns of feedback strengths thus obtained have been analyzed in relation to the monsoon timing. During the monsoon season, atmospheric conditions where soil moisture positively influences precipitation are present about 25% of the time. During onset and retreat of the monsoon, the south and east of India show more potential for feedbacks than the north. These feedbacks suggest that large-scale irrigation in the south and east may increase local precipitation. To test this, precipitation data (from 1960 to 2004) for the period about three weeks just before the monsoon onset date have been studied. A positive trend in the precipitation just before the monsoon onset is found for irrigated stations. It is shown that for irrigated stations, the trend in the precipitation just before the monsoon onset is positive for the period 1960–2004. For nonirrigated stations, there is no such upward trend in this period. The precipitation trend for irrigated areas might be due to a positive trend in the extent of irrigated areas, with land–atmosphere feedbacks inducing increased precipitation.

Sign in / Sign up

Export Citation Format

Share Document