scholarly journals The Fidelity of NCEP CFS Seasonal Hindcasts over Nordeste

2007 ◽  
Vol 135 (2) ◽  
pp. 618-627 ◽  
Author(s):  
Vasubandhu Misra ◽  
Yuning Zhang
Keyword(s):  
Atlantic Ocean ◽  
Large Scale ◽  
Southern Oscillation ◽  
Rainfall Variability ◽  
Small Region ◽  
Tropical Atlantic ◽  
Forecast System ◽  
Climate Forecast System ◽  
Tropical Atlantic Ocean ◽  
Scale Error

Abstract The fidelity of the interannual variability of precipitation over Nordeste is examined using the suite of the NCEP Climate Forecast System (CFS) seasonal hindcasts. These are coupled ocean–land–atmosphere multiseasonal integrations. It is shown that the Nordeste rainfall variability in the season of February–April has relatively low skill in the CFS seasonal hindcasts. Although Nordeste is a comparatively small region in the northeast of Brazil, the analysis indicates that the model has a large-scale error in the tropical Atlantic Ocean. The CFS exhibits a widespread El Niño–Southern Oscillation (ENSO) forcing over the tropical Atlantic Ocean. As a consequence of this remote ENSO forcing, the CFS builds an erroneous meridional SST gradient in the tropical Atlantic that is known from observations to be a critical forcing for the rainfall variability over Nordeste.

The ENSO Teleconnection to the Tropical Atlantic Ocean: Contributions of the Remote and Local SSTs to Rainfall Variability in the Tropical Americas*

2001 ◽  
Vol 14 (24) ◽  
pp. 4530-4544 ◽  
Author(s):  
Alessandra Giannini ◽  
John C. H. Chiang ◽  
Mark A. Cane ◽  
Yochanan Kushnir ◽  
Richard Seager
Keyword(s):  
Atlantic Ocean ◽  
Rainfall Variability ◽  
Tropical Atlantic ◽  
Tropical Atlantic Ocean

scholarly journals What can we learn from observed temperature and salinity isopycnal anomalies at eddy generation sites?  Application in the Tropical Atlantic Ocean.

2021 ◽  
Author(s):  
Habib Micaël Aguedjou ◽  
Alexis Chaigneau ◽  
Isabelle Dadou ◽  
Yves Morel ◽  
Cori Pegliasco ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
Large Scale ◽  
Tropical Atlantic ◽  
Diapycnal Mixing ◽  
Tropical Atlantic Ocean ◽  
Ocean Eddies ◽  
New Born ◽  
Numerical Studies ◽  
Eddy Generation ◽  
Key Parameter

<p>Potential vorticity (PV) is a key parameter to analyze the generation and dynamics of mesoscale eddies. Numerical studies have shown how adiabatic (displacement of particles within a background gradient of PV) and diabatic (diapycnal mixing and friction) processes can be involved in the generation of localized PV anomalies and vortices. Such processes are however difficult to evaluate in the ocean because PV is difficult to evaluate at mesoscale. In this study, we argue that qualitative analysis can be done, based on the link between PV anomalies and isopycnal temperature/salinity anomalies (<em>Ɵ’</em><em>/S’</em>). Indeed, in the ocean, eddies created by diapycnal mixing or isopycnal advection of water-masses, are associated with PV anomalies and significant isopycnal <em>Ɵ’</em><em>/S’</em>. In contrast, eddies created by friction are associated with PV anomalies but without isopycnal <em>Ɵ’</em><em>/S’</em>. In this study, based on 18 years of satellite altimetry data and vertical <em>Ɵ</em><em>/S</em> profiles acquired by Argo floats, we analyze the isopycnal <em>Ɵ’</em><em>/S’</em> within new-born eddies in the tropical Atlantic Ocean (TAO) and discuss the possible mechanisms involved in their generation. Our results show that on density-coordinates system, both anticyclonic (AEs) and cyclonic (CEs) eddies can exhibit positive, negative, or non-significant <em>Ɵ’</em><em>/S’</em>. Almost half of the sampled eddies do not have significant <em>Ɵ’</em><em>/S’ </em>at their generation site, indicating that frictional effects probably play a significant role in the generation of their PV anomalies. The other half of eddies, likely generated by diapycnal mixing or isopycnal advection, exhibits significant positive or negative anomalies with typical Ɵ’ of ±0.5°C. More than 70% of these significant eddies are subsurface-intensified, having their cores below the seasonal pycnocline. Refined analyses of the vertical structure of new-born eddies in three selected subregions of the TAO where the strongest anomalies were observed, show the dominance of cold (warm, respectively) subsurface AEs (CEs) likely due to isopycnal advection of large scale PV and temperature.</p>

scholarly journals The influence of biogenic emissions from Africa on tropical tropospheric ozone during 2006: a global modeling study

2009 ◽  
Vol 9 (2) ◽  
pp. 10367-10427 ◽  
Author(s):  
J. E. Williams ◽  
M. P. Scheele ◽  
P. F. J. van Velthoven ◽  
J.-P. Cammas ◽  
V. Thouret ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
Tropospheric Ozone ◽  
Large Scale ◽  
Transport Model ◽  
Biogenic Emissions ◽  
Tropical Region ◽  
Tropical Atlantic ◽  
Tropical Atlantic Ocean ◽  
Volatile Organic ◽  
The Tropics

Abstract. We have performed simulations using a 3-D global chemistry-transport model to investigate the influence that biogenic emissions from the African continent exert on the composition of the tropopause in the tropical region. For this purpose we have applied two recently developed biogenic emission inventories provided for use in large-scale global models (Granier et al., 2005; Lathiére et al., 2006) whose seasonality and temporal distribution for isoprene, biogenic NO and biogenic volatile organic compounds is markedly different. The use of the climatological values for biogenic emissions provided by Lathiére et al. (2006) results in an increase in the amount of nitrogen sequestrated into longer lived reservoir compounds which contributes to the reduction in tropospheric ozone burden in the tropics. The associated re-partitioning of nitrogen between PAN, HNO3 and organic nitrates also results in a ~5% increase in the loss of nitrogen by wet deposition. At a global scale there is a reduction in the oxidizing capacity of the model atmosphere which increases the atmospheric lifetimes of CH4 and CO by ~1.5% and ~4%, respectively. By the use of sensitivity studies we show that the release of NO from soils in Africa accounts for between ~5–45% of tropospheric ozone in the African troposphere, ~10% in the upper troposphere and between ~5–20% of the tropical tropospheric ozone column over the tropical Atlantic Ocean. The subsequent reduction in OH over the source regions allows enhanced transport of CO out of the region. For biogenic volatile organic C1 to C3 species released from Africa the effects on tropical tropospheric ozone are rather limited, although this source contributes to the global burden of VOC by between ~2–4% and has a large influence on the organic composition of the troposphere over the tropical Atlantic Ocean. Comparisons against a range of different measurements indicate that applying the climatology of Lathiére et al. (2006) improves the performance of TM4 for 2006 in the tropics.

scholarly journals The influence of biogenic emissions from Africa on tropical tropospheric ozone during 2006: a global modeling study

2009 ◽  
Vol 9 (15) ◽  
pp. 5729-5749 ◽  
Author(s):  
J. E. Williams ◽  
M. P. Scheele ◽  
P. F. J. van Velthoven ◽  
J.-P. Cammas ◽  
V. Thouret ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
Tropospheric Ozone ◽  
Large Scale ◽  
Transport Model ◽  
Biogenic Emissions ◽  
Tropical Region ◽  
Tropical Atlantic ◽  
Tropical Atlantic Ocean ◽  
Volatile Organic ◽  
The Tropics

Abstract. We have performed simulations using a 3-D global chemistry-transport model to investigate the influence that biogenic emissions from the African continent exert on the composition of the troposphere in the tropical region. For this purpose we have applied two recently developed biogenic emission inventories provided for use in large-scale global models (Granier et al., 2005; Lathière et al., 2006) whose seasonality and temporal distribution for biogenic emissions of isoprene, other volatile organic compounds and NO is markedly different. The use of the 12 year average values for biogenic emissions provided by Lathière et al. (2006) results in an increase in the amount of nitrogen sequestrated into longer lived reservoir compounds which contributes to the reduction in the tropospheric ozone burden in the tropics. The associated re-partitioning of nitrogen between PAN, HNO3 and organic nitrates also results in a ~5% increase in the loss of nitrogen by wet deposition. At a global scale there is a reduction in the oxidizing capacity of the model atmosphere which increases the atmospheric lifetimes of CH4 and CO by ~1.5% and ~4%, respectively. Comparisons against a range of different measurements indicate that applying the 12 year average of Lathière et al. (2006) improves the performance of TM4_AMMA for 2006 in the tropics. By the use of sensitivity studies we show that the release of NO from soils in Africa accounts for between ~2–45% of tropospheric ozone in the African troposphere, ~10% in the upper troposphere and between ~5–20% of the tropical tropospheric ozone column over the tropical Atlantic Ocean. The subsequent reduction in OH over the source regions allows enhanced transport of CO out of the region. For biogenic volatile organic C1 to C3 species released from Africa, the effects on tropical tropospheric ozone are rather limited, although this source contributes to the global burden of VOC by between ~2–4% and has a large influence on the organic composition of the troposphere over the tropical Atlantic Ocean.

scholarly journals Correction to: Weakened SST variability in the tropical Atlantic Ocean since 2000

2021 ◽  
Author(s):  
Arthur Prigent ◽  
Joke F. Lübbecke ◽  
Tobias Bayr ◽  
Mojib Latif ◽  
Christian Wengel
Keyword(s):  
Atlantic Ocean ◽  
Tropical Atlantic ◽  
Tropical Atlantic Ocean ◽  
Sst Variability
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