scholarly journals Impact of New Solar Radiation Parameterization in the Eta Model on the Simulation of Summer Climate over South America

2006 ◽  
Vol 45 (2) ◽  
pp. 318-333 ◽  
Author(s):  
T. A. Tarasova ◽  
J. P. R. Fernandez ◽  
I. A. Pisnichenko ◽  
J. A. Marengo ◽  
J. C. Ceballos ◽  
...  
Keyword(s):  
Solar Radiation ◽  
South America ◽  
Surface Air Temperature ◽  
Surface Flux ◽  
Global Precipitation Climatology Project ◽  
South Atlantic Convergence Zone ◽  
Horizontal Resolution ◽  
The South ◽  
Near Surface ◽  
Incident Solar Radiation

Abstract The regional Eta workstation (WS) model with horizontal resolution of 40 km has been integrated over South America for January 2003. The NCEP–DOE Reanalysis II was used for initial and lateral boundary conditions. The comparison of the model-simulated and satellite-derived values of monthly mean incident solar radiation at the surface demonstrates that the former values are larger by 20%–30% over the entire region. To improve the surface flux representation in the model, a new solar radiation scheme has been implemented in it. An offline comparison of the original and the new radiation schemes with the detailed line-by-line method demonstrates a higher accuracy for the new scheme. With the new scheme, the model-simulated incident solar radiation at the surface is in a better agreement with the satellite-derived data. Nevertheless, a noticeable systematic difference of 10%–20% still remains, probably because of the incorrect description of cloud parameters in the model. The lower incident solar radiation in the new version of the model causes a decrease of near-surface air temperature by 0.1°–1°C and a decrease of precipitation rate by up to 20%–30% over most of the continent. The increase in the simulated incident solar radiation and temperature is found in the region of the South Atlantic convergence zone, which is responsible for the enhanced cloudiness and precipitation in the central and southeastern parts of Brazil during summer. The model results are compared with observational data of meteorological stations, the Global Precipitation Climatology Project (GPCP), and the South American Low-Level Jet Experiment (SALLJEX) and are discussed.

scholarly journals Assessment of Heat Stress and Cloudiness Probabilities in Post-Flowering of Wheat and Canola in The Southern Cone of South America

2021 ◽  
Author(s):  
Gonzalo Martín Rivelli ◽  
María Elena Fernández Long ◽  
Leonor Gabriela Abeledo ◽  
Daniel Calderini ◽  
Daniel Julio Miralles ◽  
...  
Keyword(s):  
Heat Stress ◽  
Solar Radiation ◽  
South America ◽  
Southern Cone ◽  
Maximum Temperature ◽  
Curvilinear Relationship ◽  
Climate Scenarios ◽  
Incident Solar Radiation ◽  
Probability Of Occurrence ◽  
Combined Stresses

Abstract Episodes of heat stress constrain crop production and will be aggravated in the near future according to short and medium-term climate scenarios. Global increase in cloudiness has also been observed, decreasing the incident solar radiation. This work was aimed to quantify the probability of occurrence of heat stress and cloudiness, alone or combined, during the typical post-flowering period of wheat and canola in the Southern Cone of South America. Extended climate series (last 3-5 decades with daily register) of 33 conventional weather stations from Argentina, Brazil, Chile and Uruguay (23ºS to 40ºS) were analysed considering the period from September to December. Two different daily events of heat stress were determined: i) maximum daily temperature above 30ºC (T>30ºC), and ii) 5ºC above the historical average maximum temperature of that day (T+5ºC). A cloudiness event was defined in our work as incident solar radiation 50% lower than the historical average radiation of that day (R50%). The T>30ºC event increased its probability of occurrence throughout the post-flowering phase, from September to December. By contrast, the risk of T+5ºC event decreased slightly, just like for R50%, and the higher the latitude, the lower the probability of R50%. The T>30ºC plus R50% combined stresses reached greater cumulated probabilities during post-flowering, compared to T+5ºC plus R50%, being 42% vs. 15% in northernmost locations, 26% vs. 19% in central (between 31ºS to 35ºS), and 28% vs. 1% in southernmost locations, respectively. A curvilinear relationship emerged between the monthly probability of combined stresses and the number of days with stress per month. In summary, T>30ºC was the most frequent thermal stress during post-flowering in wheat and canola. Both combined stresses had a noticeable risk of occurrence, but T>30ºC plus R50% was the highest. Evidence of the recent past and current occurrence of heat stress individually, and its combination with cloudiness events during post-flowering of temperate crops, serves as a baseline for future climate scenarios in main cropped areas in the Southern Cone of South America.

From severe droughts in South America to marine heatwaves in the South Atlantic

2020 ◽  
Author(s):  
Regina Rodrigues ◽  
Andrea Taschetto ◽  
Alex Sen Gupta ◽  
Gregory Foltz
Keyword(s):  
South America ◽  
South Atlantic Convergence Zone ◽  
South Atlantic ◽  
Shortwave Radiation ◽  
Severe Drought ◽  
Atmospheric Blocking ◽  
The South ◽  
Water Shortages ◽  
Southwest Atlantic ◽  
Anticyclonic Circulation

<p>In 2013/14 eastern South America experienced one of its worst droughts, leading to water shortages in São Paulo, the world’s fourth most populated city. This event was also responsible for a dengue fever outbreak that tripled the usual number of fatalities and reduced Brazilian coffee production leading to a global shortages and worldwide price increases. The drought was associated with an anomalous anticyclonic circulation off southeast South America that prevented synoptic systems reaching the region while inhibiting the development of the South Atlantic Convergence Zone and its associated rainfall. A concomitant and unprecedented marine heatwave also developed in the southwest Atlantic. Here we show from observations that such droughts and adjacent marine heatwaves have a common remote cause. Atmospheric blocking triggered by tropical convection in the Indian and Pacific oceans can cause persistent anticyclonic circulation that not only leads to severe drought but also generates marine heatwaves in the adjacent ocean. We show that increased shortwave radiation due to reduced cloud cover and reduced ocean heat loss from weaker winds are the main contributors to the establishment of marine heatwaves in the region. The proposed mechanism, which involves droughts, extreme air temperature over land and atmospheric blocking explains approximately 60% of the marine heatwave events in the western South Atlantic. We also identified an increase in frequency, duration, intensity and extension of marine heatwave events over the satellite period 1982–2016. Moreover, surface primary production was reduced during these events with implications for regional fisheries.</p>

scholarly journals Impact of Atmospheric Blocking on South America in Austral Summer

2017 ◽  
Vol 30 (5) ◽  
pp. 1821-1837 ◽  
Author(s):  
Regina R. Rodrigues ◽  
Tim Woollings
Keyword(s):  
South America ◽  
Wave Train ◽  
Austral Summer ◽  
Surface Air Temperature ◽  
South Atlantic Convergence Zone ◽  
Atmospheric Blocking ◽  
Central Pacific ◽  
Temperature And Precipitation ◽  
The Indian Ocean

Abstract This study investigates atmospheric blocking over eastern South America in austral summer for the period of 1979–2014. The results show that blocking over this area is a consequence of propagating Rossby waves that grow to large amplitudes and eventually break anticyclonically over subtropical South America (SSA). The SSA blocking can prevent the establishment of the South Atlantic convergence zone (SACZ). As such, years with more blocking days coincide with years with fewer SACZ days and reduced precipitation. Convection mainly over the Indian Ocean associated with Madden–Julian oscillation (MJO) phases 1 and 2 can trigger the wave train that leads to SSA blocking whereas convection over the western/central Pacific associated with phases 6 and 7 is more likely to lead to SACZ events. It is found that the MJO is a key source of long-term variability in SSA blocking frequency. The wave packets associated with SSA blocking and SACZ episodes differ not only in their origin but also in their phase and refraction pattern. The tropopause-based methodology used here is proven to reliably identify events that lead to extremes of surface temperature and precipitation over SSA. Up to 80% of warm surface air temperature extremes occur simultaneously with SSA blocking events. The frequency of SSA blocking days is highly anticorrelated with the rainfall over southeast Brazil. The worst droughts in this area, during the summers of 1984, 2001, and 2014, are linked to record high numbers of SSA blocking days. The persistence of these events is also important in generating the extreme impacts.

scholarly journals Atmospheric convergence zones stemming from large-scale mixing

2021 ◽  
Vol 2 (2) ◽  
pp. 475-488
Author(s):  
Gabriel M. P. Perez ◽  
Pier Luigi Vidale ◽  
Nicholas P. Klingaman ◽  
Thomas C. M. Martin
Keyword(s):  
South America ◽  
Large Scale ◽  
Hydrological Cycle ◽  
Moisture Flux ◽  
South Atlantic Convergence Zone ◽  
South Atlantic ◽  
Convergence Zone ◽  
The South ◽  
Atmospheric Flow ◽  
Convergence Zones

Abstract. Organised cloud bands are important features of tropical and subtropical rainfall. These structures are often regarded as convergence zones, alluding to an association with coherent atmospheric flow. However, the flow kinematics is not usually taken into account in classification methods for this type of event, as large-scale lines are rarely evident in instantaneous diagnostics such as Eulerian convergence. Instead, existing convergence zone definitions rely on heuristic rules of shape, duration and size of cloudiness fields. Here we investigate the role of large-scale turbulence in shaping atmospheric moisture in South America. We employ the finite-time Lyapunov exponent (FTLE), a metric of deformation among neighbouring trajectories, to define convergence zones as attracting Lagrangian coherent structures (LCSs). Attracting LCSs frequent tropical and subtropical South America, with climatologies consistent with the South Atlantic Convergence Zone (SACZ), the South American Low-Level Jet (SALLJ) and the Intertropical Convergence Zone (ITCZ). In regions under the direct influence of the ITCZ and the SACZ, rainfall is significantly positively correlated with large-scale mixing measured by the FTLE. Attracting LCSs in south and southeast Brazil are associated with significant positive rainfall and moisture flux anomalies. Geopotential height composites suggest that the occurrence of attracting LCSs in these regions is related with teleconnection mechanisms such as the Pacific–South Atlantic. We believe that this kinematical approach can be used as an alternative to region-specific convergence zone classification algorithms; it may help advance the understanding of underlying mechanisms of tropical and subtropical rain bands and their role in the hydrological cycle.

scholarly journals Estimation of Incident Solar Radiation on the Walls of a Habitat for the Typical Day of April in the Ouagadougou Region in Burkina Faso

2020 ◽  
Vol 5 (9) ◽  
pp. 1128-1132
Author(s):  
Baba MANSARE ◽  
Mamadouba CONTE ◽  
Yacouba CAMARA ◽  
Amadou Lamarana BAH ◽  
Drissa OUEDRAOGO
Keyword(s):  
Mathematical Model ◽  
Solar Radiation ◽  
Burkina Faso ◽  
Programming Language ◽  
Solar Flux ◽  
The South ◽  
Incident Solar Radiation ◽  
Typical Day ◽  
Set Up ◽  
Fortran Programming Language

His work aims to develop a mathematical model of incident solar radiation on all the walls of a sloping roof habitat for a typical climate in the Ouagadougou region. Subsequently, we set up a program for the calculations of the essential parameters of illumination and the various components of solar radiation under the Fortran Programming Language and to plot our curves using the Origin software. This work allowed us to estimate the amount of solar flux that each wall of a habitat receives during a day, to know the importance of the orientation of the main facade of the habitat to the south and to find out how often the roof is exposed to solar radiation.

scholarly journals Atmospheric convergence zones stemming from large-scale mixing

2020 ◽  
Author(s):  
Gabriel M. P. Perez ◽  
Pier Luigi Vidale ◽  
Nicholas P. Klingaman ◽  
Thomas C. M. Martin
Keyword(s):  
South America ◽  
Large Scale ◽  
Hydrological Cycle ◽  
Moisture Flux ◽  
South Atlantic Convergence Zone ◽  
South Atlantic ◽  
Convergence Zone ◽  
The South ◽  
Atmospheric Flow ◽  
Convergence Zones

Abstract. Organised cloud bands are important features of tropical and subtropical rainfall. These structures are often regarded as convergence zones, alluding to an association with coherent atmospheric flow. However, the flow kinematics is not usually taken into account in classification methods for this type of event, as large-scale lines are rarely evident in instantaneous diagnostics such as Eulerian convergence. Instead, existing convergence zone definitions rely on heuristic rules of shape, duration and size of cloudiness fields. Here we investigate the role of large-scale turbulence in shaping atmospheric moisture in South America. We employ the Finite-Time Lyapunov Exponent (FTLE), a metric of deformation among neighboring trajectories, to define convergence zones as attracting Lagrangian Coherent Structures (LCSs). Attracting LCSs frequent tropical and subtropical South America, with climatologies consistent with the South Atlantic Convergence Zone (SACZ), the South American Low-level Jet (SALLJ) and the Intertropical Convergence Zone (ITCZ). In regions under the direct influence of the ITCZ and the SACZ, rainfall is significantly positively correlated with large-scale mixing measured by the FTLE. Attracting LCSs in South and Southeast Brazil are associated with significant positive rainfall and moisture flux anomalies. Geopotential height composites suggest that the occurrence of attracting LCSs in these regions is related with teleconnection mechanisms such as the Pacific-South Atlantic. We believe that this kinematical approach can be used as an alternative to region-specific convergence zone classification algorithms; it may help advance the understanding of underlying mechanisms of tropical and subtropical rain bands and their role in the hydrological cycle.

scholarly journals Submonthly Convective Variability over South America and the South Atlantic Convergence Zone

1999 ◽  
Vol 12 (7) ◽  
pp. 1877-1891 ◽  
Author(s):  
Brant Liebmann ◽  
George N. Kiladis ◽  
JoséA. Marengo ◽  
Tércio Ambrizzi ◽  
John D. Glick
Keyword(s):  
South America ◽  
South Atlantic Convergence Zone ◽  
South Atlantic ◽  
Convergence Zone ◽  
The South

scholarly journals Using GRACE to Estitmate Snowfall Accumulation and Assess Gauge Undercatch Corrections in High Latitudes

2018 ◽  
Vol 31 (21) ◽  
pp. 8689-8704 ◽  
Author(s):  
Ali Behrangi ◽  
Alex Gardner ◽  
John T. Reager ◽  
Joshua B. Fisher ◽  
Daqing Yang ◽  
...  
Keyword(s):  
High Latitude ◽  
Surface Air Temperature ◽  
Global Precipitation Climatology Project ◽  
Dynamic Correction ◽  
Northern Asia ◽  
Near Surface ◽  
Precipitation Climatology ◽  
Global Precipitation Climatology Centre ◽  
Terrestrial Water ◽  
Global Precipitation

Ten years of terrestrial water storage anomalies from the Gravity Recovery and Climate Experiment (GRACE) were used to estimate high-latitude snowfall accumulation using a mass balance approach. The estimates were used to assess two common gauge-undercatch correction factors (CFs): the Legates climatology (CF-L) utilized in the Global Precipitation Climatology Project (GPCP) and the Fuchs dynamic correction model (CF-F) used in the Global Precipitation Climatology Centre (GPCC) monitoring product. The two CFs can be different by more than 50%. CF-L tended to exceed CF-F over northern Asia and Eurasia, while the opposite was observed over North America. Estimates of snowfall from GPCP, GPCC-L (GPCC corrected by CF-L), and GPCC-F (GPCC corrected by CF-F) were 62%, 64%, and 46% more than GPCC over northern Asia and Eurasia. The GRACE-based estimate (49% more than GPCC) was the closest to GPCC-F. We found that as near-surface air temperature decreased, the products increasingly underestimated the GRACE-based snowfall accumulation. Overall, GRACE showed that CFs are effective in improving GPCC estimates. Furthermore, our case studies and overall statistics suggest that CF-F is likely more effective than CF-L in most of the high-latitude regions studied here. GPCP showed generally better skill than GPCC-L, which might be related to the use of satellite data or additional quality controls on gauge inputs to GPCP. This study suggests that GPCP can be improved if it employs CF-L instead of CF-F to correct for gauge undercatch. However, this implementation requires further studies, region-specific analysis, and operational considerations.

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