Papers by Jacques Servain
* le bilan radiatif des ondes courtes et longues est celui de la climatologie mensuelle de Esbens... more * le bilan radiatif des ondes courtes et longues est celui de la climatologie mensuelle de Esbensen et Kushnir (1981). * les flux de chaleur sensible et latente sont calculés à l'aide des formules aérodynamiques globales où la température de l'air provient de la climatologie mensuelle d'Esbensen et Kushnir (1981), l'humidité relative est forcée à une valeur constante (80 %), et la SST est celle simulée par le modèle au pas de temps précédent .
Flux de chaleur sur l'Atlantique tropical en 1989
Climate Studies in Tropical Region
Atmospheric turbulent fluxes over the tropical Atlantic Ocean: project FluTuA preliminary results
Extremes: climate and water in the Southern Hemisphere: short abstracts, 2009
Summer and winter Atlantic Niño: connections with ENSO and implications
Climate Dynamics, 2020
The teleconnection between the Atlantic Niño and the Pacific El Niño Southern Oscillation (ENSO) ... more The teleconnection between the Atlantic Niño and the Pacific El Niño Southern Oscillation (ENSO) is revisited using observational and reanalysis data for the 1905–2014 period. Two types of Atlantic Niño are significantly negatively correlated with ENSO, with Atlantic leading ENSO by 6-month to 1-year. The first one is the already well-known connection between the boreal summer Atlantic Niño (ATL3: 3° N–3° S, 20° W–0°) and the subsequent winter ENSO (Niño3: 5° N–5° S, 150° W–90° W). This relationship is strong in the first and last decades of the study period. It is shown that a second Atlantic Niño in boreal fall/early winter (October–December, hereinafter called winter Atlantic Niño) is also significantly correlated with the following year ENSO. This winter Atlantic Niño leads to an early development of ENSO from boreal summer onwards, with a marked multidecadal modulation of the lead time. A nearly 1-year leading connection between winter Atlantic Niño and the following ENSO is generally observed in the mid-twentieth century, mostly when the summer Atlantic Niño teleconnection with the subsequent winter ENSO is weak. The same mechanism of the Atlantic–Pacific Niño connection, which involves the Walker circulation, operates for the two types of Atlantic Niño. Our analysis supports the leading influence of the summer and winter Atlantic equatorial modes on climate variability in South America. These results suggest the relevance of different types of Atlantic Niño for the 6-month to 1-year predictability of ENSO and its climatic impacts.
Geochemistry, Geophysics, Geosystems, 2018
Although relatively rare compared to similar latitudes in the Pacific or Indian Oceans, massive c... more Although relatively rare compared to similar latitudes in the Pacific or Indian Oceans, massive coral colonies are present in the Tropical/Equatorial Southwestern Atlantic Ocean. However, detailed geochemical compositions of these corals are still largely unknown. In this work, we present growth rates, Sr/Ca, and U/Ca ratios of the coral colony (Siderastrea stellata) sampled at Rocas Atoll, off the Brazilian coast. These variables are primarily affected by sea surface temperature (SST) at seasonal scale, and by wind stress at interannual scale, these results represent a broad new finding. A lower significance at the interannual time scale between Sr/Ca and U/Ca with respect to SST is attributed to the low SST amplitude closed to Equator. An investigation on the dependence of coral growth rates with respect to the “cloud shading effect” promoted by the Intertropical Convergence Zone (ITCZ) does not show significant influence. Additionally, rain seems to act on local geochemistry of S...
A geostatistic method, known as the kriging method is employed to produce a gridded wind field us... more A geostatistic method, known as the kriging method is employed to produce a gridded wind field using ERS-1 scatterometer-retrieved wind vectors. The method, which differs from the classical interpolation methods, makes use of spatial and temporal empirical structure functions for wind speed, eastward wind component u and northward wind component u, and the Gauss-Markov theorem to objectively analyze this vector field and yields an expression for the variance error expected in this estimate. The stationarity assumptions needed to apply the kriging method are tested statistically. Resultant three-, seven-and ten-day average wind fields computed over the tropical region indicate that the method reproduces large and small-scale features. The accuracy of the gridded wind fields is determined by comparisons with three-day averages calculated from European Centre for Medium-range Weather Forecasts (ECMWF) wind vector analysis, with ten-day averages derived from ship measurements over the tropical Atlantic, and with seven-day averages computed from moored-buoy wind measurements, which were recorded by Pacific Marine Environmental Laboratory (PMEL) in the Pacific ocean. I n all cases, there is good agreement between the data sets. The rms values of the difference between satellite and numerical analysis, ship and buoy-derived wind fields are 1.67m/s, 1.17m/s and 1.05 m/s, respectively.
Long-term variations of SST and heat content in the Atlantic Ocean
EGU General Assembly Conference Abstracts, Apr 1, 2015
Journal of Geophysical Research, 1990
During the past few years, an increasing effort has been made to estimate recent interannual vari... more During the past few years, an increasing effort has been made to estimate recent interannual variability of the world climate. Most of the studies were based on analyses of air and sea surface temperature (SST) time series. Indeed, for data collected from the beginning of the present century, it is generally accepted [Cayan, 1980; Paltridge and Woodruff, 19811 that these two variables vary in harmony on time scales of more than a month. Because of heating of the ship superstructures during the daytime, the correlation is better when only using nightime marine air temperatures [Follatid et al., 1984; Oort e t al., 19871. On a hemispheric scale, these authors and others [Jones er al., 1982, 1986a, b; Angell, 19861 show that the southern hemisphere experienced sustained warming and is currently at its warmest level [Jones, 19881. Northern hemisphere temperatures increased until 1930-1950, decreased during the 1960s, and increased again during the past 10 years. Regional-scale studies allow us to specify these climate changes. Since tropical oceans strongly affect global atmospheric circulation, they are particularly important to investigate. The purpose of the current 10-year program Tropical Ocean-Global Atmosphere (TOGA) is to observe and understand year-to-year climate variability. The A !
El Niño. A statistical analysis, associating these fields with time series of precipitaliod regim... more El Niño. A statistical analysis, associating these fields with time series of precipitaliod regimes in Africa and Brazil, enlarges on some earlier studies performed from' restricted occurrences.
Causes and processes of two opposite climatic years in the tropical Atlantic warm pools
Dynamics of Atmospheres and Oceans
Marine reports from merchant ships in marine decks are routinely used to analyze the large-scale ... more Marine reports from merchant ships in marine decks are routinely used to analyze the large-scale seasonal variability of the sea surface temperature (SST). Marine reports, together with other in-situ data, are also used (Reynolds, 1988) to correct possible biases in SST retrieved from-satellite-borne radiometers (McClain et al., 1985; Strong and McClain, 1984). Whether these data are of
Advances in Meteorology, 2015
Tropical Atlantic Ocean-atmosphere interactions and their contributions to strong variability of ... more Tropical Atlantic Ocean-atmosphere interactions and their contributions to strong variability of rainfall along the Northeast Brazilian coast (NEB) were investigated for the years 1974-2008. The core rainy seasons of March-April (MA) and June-July (JJ) were identified for Fortaleza (northern Northeast Brazil; NNEB) and Recife (eastern Northeast Brazil; ENEB), respectively. Lagged linear regressions between sea surface temperature (SST) and pseudo wind stress (PWS) anomalies over the entire tropical Atlantic and strong rainfall anomalies at Fortaleza (NNEB) and Recife (ENEB) show that the rainfall variability of these regions is differentially influenced by the dynamics of the tropical Atlantic. When the intertropical convergence zone (ITCZ) is abnormally displaced southward a few months prior to the NNEB rainy season, the associated meridional mode (strengthening of the NE trade winds, relaxation of the SE trade winds, colder SST in the North, and warmer SST in the South) increases humidity and precipitation during the rainy season. The opposite effect occurs during the positive phase of the dipole. Additionally, this study shows strong influence and predictive effect of SST, PWS and barrier layer thickness, in the Northwestern equatorial Atlantic (NEA), on the NNEB rainfall. The dynamical influence of the tropical Atlantic on the June-July ENEB rainfall variability shows a northwestward-propagating area of strong, positively correlated SST from the southeastern tropical Atlantic to the southwestern Atlantic warm pool (SAWP) offshore of Brazil. The northwestward-propagating area,
These widely used products, derived from surface-based observations, are an excellent resource for ENSO forecasting and ocean-atmosphere research
Bourassa, M. A., 2004: An Improved Seastate Dependency For Surface Stress Derived from In Situ and Remotely Sensed Winds. Advances in Space Res., 33(7), 1136-1142
ABSTRACT An improved model is developed for the dependency of surface turbulent stress on wave ch... more ABSTRACT An improved model is developed for the dependency of surface turbulent stress on wave characteristics. Recent studies have used differences between satellite and in situ observations to gain insights into the physical processes that might be related to air-sea interaction. Both scatterometers and buoys provide very accurate measurements of wind speed. Differences between these measurements can be explained in terms of the different mechanisms to which the instruments respond. A physically-based flux model is developed herein. Prior results suggest that the stress parameterizations, converting neutral equivalent wind speed to stress, applied to in situ observations differ subtlety from those that should be used for scatterometer-derived winds. These differences are due to water waves modifying the surface stress. This model provides a physical explanation of the observed differences, and provides a model for calculating stresses from scatterometer winds. The model is validated with recent in situ observations gathered under severe conditions. The model explains more wave-related variability in surface stress than previous models.
Revista Brasileira de Meteorologia, 2014
Tropical Instability Waves and the warming of the Atlantic cold tongue: Analysis of the ATLAS and ADCP PIRATA moorings data from 0n, 23W
AGU Spring …, 2004
Title: Tropical Instability Waves and the warming of the Atlantic cold tongue : Analysis of the A... more Title: Tropical Instability Waves and the warming of the Atlantic cold tongue : Analysis of the ATLAS and ADCP PIRATA moorings data from 0n, 23W. ... Origin: AGU. Keywords: 1620 Climate dynamics (3309), 4500 OCEANOGRAPHY: PHYSICAL, 4504 Air/sea interactions (0312). ...
Temperature, salinity, and recent velocity records from the PIRATA moorings at 0 o N, 23 o W coll... more Temperature, salinity, and recent velocity records from the PIRATA moorings at 0 o N, 23 o W collected during 2002 are used to examine the Tropical Instability Waves (TIW) and their role in the mixed layer heat balance of the central equatorial Atlantic. The TIW appear as periodic 20-30 day fluctuations in currents which intensify beginning in June in phase with the strengthening of the southeasterly trade winds and the seasonal appearance of the equatorial cold tongue. Zonal velocity fluctuations are largest in July-August, while meridional velocity fluctuations are largest in August-September. The meridional component of velocity is also distinguished from the zonal component in that fluctuations of the meridional component extend coherently in the vertical to at least 120 m while zonal fluctuations are coherent within the mixed layer only. Our estimate of horizontal eddy heat advection in the mixed layer averaged June-September is ~ 100 W m -2 with meridional advection dominating and peaking in late boreal summer. Averaged over the whole summer the contribution of the TIW events to the warming of the mixed layer is of 0.5 o C, which corresponds to a modest value of the eddy heat advection of 15 W m -2 . Since this value is very much less than the estimates of the summer mean eddy horizontal heat advection of 50 -100 W m -2 this indicates that horizontal and vertical eddy heat advection balance in part, as suggested recently by .
Water Resources Management, 2012
This study investigated the sensitivity of a dynamic downscaling atmospheric model system coupled... more This study investigated the sensitivity of a dynamic downscaling atmospheric model system coupled with a rainfall-runoff model to hindcast an example of reservoir water management in the semi-arid region of Northeast Brazil (NEB). A regional atmospheric spectral model (RSM) is driven by the outputs of an atmospheric general circulation model (AGCM), itself forced by the observed sea surface temperature over the World Ocean. Daily precipitation simulated by the RSM was then used as the input to a hydrological rainfallrunoff model for the Upper Jaguaribe River Basin to estimate inflows at the Orós Reservoir in the state of Ceará. A hindcast analysis of precipitation was performed during the rainy season over NEB (January to June) from 1971 to 2000. The RSM captured the precipitation variability relatively well when a probability density function (PDF) was used to correct the numerical bias. Three hindcast series of inflow using (i) the observed rainfall, (ii) the simulated rainfall before the PDF correction, and (iii) the simulated rainfall after the PDF correction were performed during the study period and then compared to the series of observed inflow. The atmospheric-rainfall-runoff "cascade" model efficiency was evaluated by comparing the Orós Reservoir release decisions from different scenarios based on observed, simulated (RSM, RSM-PDF), and mean historical reservoir inflows. The cascade model has the potential, relatively well balanced during dry, normal or wet years, to be a Water Resour Manage useful tool to correctly forecast the decision managements of reservoirs in the semi-arid region of NEB. Additional progress in the numerical simulation is however necessary to improve the performance.
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Papers by Jacques Servain