scholarly journals Impacts of Agulhas Leakage on the Tropical Atlantic Western Boundary Systems

2017 ◽  
Vol 30 (17) ◽  
pp. 6645-6659 ◽  
Author(s):  
P. Castellanos ◽  
E. J. D. Campos ◽  
J. Piera ◽  
O. T. Sato ◽  
M. A. F. Silva Dias
Keyword(s):  
Heat Flux ◽  
Atlantic Ocean ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Thermohaline Circulation ◽  
Ocean Model ◽  
Brazilian Coast ◽  
Western Boundary ◽  
Western Coast ◽  
Tropical Atlantic

The influx of warmer and saltier Indian Ocean waters into the Atlantic—the Agulhas leakage—is now recognized to play an important role in the global thermohaline circulation and climate. In this study the results of a ⅞° simulation with the Hybrid Coordinate Ocean Model, which exhibit an augmentation in the Agulhas leakage, is investigated. This increase in the leakage ought to have an impact on the meridional oceanic volume and heat transports in the Atlantic Ocean. Significant linear trends found in the integrated transport at 20°, 15°, and 5°S correlate well with decadal fluctuations of the Agulhas leakage. The augmented transport also seems to be related to an increase in the latent heat flux observed along the northeastern coastline of Brazil since 2003. This study shows that the precipitation on the Brazilian coast has been increasing since 2005, at the same location and with the same regime shift observed for the latent heat flux and the volume transport. This suggests that the increase of the Agulhas transport affects the western boundary system of the tropical Atlantic Ocean, which is directly related to an increase in the precipitation and latent heat flux along the western coast.

Latent Heat Flux over the North Atlantic Ocean—A Case Study

1991 ◽  
Vol 30 (12) ◽  
pp. 1627-1635 ◽  
Author(s):  
Susanne Crewell ◽  
Eberhard Ruprecht ◽  
Clemens Simmer
Keyword(s):  
Heat Flux ◽  
Atlantic Ocean ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
The North ◽  
The North Atlantic

Coupled Ocean–Atmosphere Interactions between the Madden–Julian Oscillation and Synoptic-Scale Variability over the Warm Pool

2005 ◽  
Vol 18 (12) ◽  
pp. 2004-2020 ◽  
Author(s):  
Crispian P. Batstone ◽  
Adrian J. Matthews ◽  
David P. Stevens
Keyword(s):  
Heat Flux ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Surface Wind ◽  
Principal Component ◽  
Ocean Model ◽  
Dominant Mode ◽  
Madden Julian Oscillation ◽  
Wind Variability ◽  
Eastern Hemisphere

Abstract A principal component analysis of the combined fields of sea surface temperature (SST) and surface zonal and meridional wind reveals that the dominant mode of intraseasonal (30 to 70 day) covariability during northern winter in the tropical Eastern Hemisphere is that of the Madden–Julian oscillation (MJO). Regression calculations show that the submonthly (30-day high-pass filtered) surface wind variability is significantly modulated during the MJO. Regions of increased (decreased) submonthly surface wind variability propagate eastward, approximately in phase with the intraseasonal surface westerly (easterly) anomalies of the MJO. Because of the dependence of the surface latent heat flux on the magnitude of the total wind speed, this systematic modulation of the submonthly surface wind variability produces a significant component in the intraseasonal latent heat flux anomalies, which partially cancels the latent heat flux anomalies due to the slowly varying intraseasonal wind anomalies, particularly south of 10°S. A method is derived that demodulates the submonthly surface wind variability from the slowly varying intraseasonal wind anomalies. This method is applied to the wind forcing fields of a one-dimensional ocean model. The model response to this modified forcing produces larger intraseasonal SST anomalies than when the model is forced with the observed forcing over large areas of the southwest Pacific Ocean and southeast Indian Ocean during both phases of the MJO. This result has implications for accurate coupled modeling of the MJO. A similar calculation is applied to the surface shortwave flux, but intraseasonal modulation of submonthly surface shortwave flux variability does not appear to be important to the dynamics of the MJO.

scholarly journals Uncertainty characterization of HOAPS 3.3 latent heat-flux-related parameters

2018 ◽  
Vol 11 (3) ◽  
pp. 1793-1815 ◽  
Author(s):  
Julian Liman ◽  
Marc Schröder ◽  
Karsten Fennig ◽  
Axel Andersson ◽  
Rainer Hollmann
Keyword(s):  
Heat Flux ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Quality Data ◽  
Boreal Winter ◽  
Western Boundary ◽  
Decomposition Approach ◽  
In Situ Data ◽  
Global Mean

Abstract. Latent heat flux (LHF) is one of the main contributors to the global energy budget. As the density of in situ LHF measurements over the global oceans is generally poor, the potential of remotely sensed LHF for meteorological applications is enormous. However, to date none of the available satellite products have included estimates of systematic, random, and sampling uncertainties, all of which are essential for assessing their quality. Here, the challenge is taken on by matching LHF-related pixel-level data of the Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite (HOAPS) climatology (version 3.3) to in situ measurements originating from a high-quality data archive of buoys and selected ships. Assuming the ground reference to be bias-free, this allows for deriving instantaneous systematic uncertainties as a function of four atmospheric predictor variables. The approach is regionally independent and therefore overcomes the issue of sparse in situ data densities over large oceanic areas. Likewise, random uncertainties are derived, which include not only a retrieval component but also contributions from in situ measurement noise and the collocation procedure. A recently published random uncertainty decomposition approach is applied to isolate the random retrieval uncertainty of all LHF-related HOAPS parameters. It makes use of two combinations of independent data triplets of both satellite and in situ data, which are analysed in terms of their pairwise variances of differences. Instantaneous uncertainties are finally aggregated, allowing for uncertainty characterizations on monthly to multi-annual timescales. Results show that systematic LHF uncertainties range between 15 and 50 W m−2 with a global mean of 25 W m−2. Local maxima are mainly found over the subtropical ocean basins as well as along the western boundary currents. Investigations indicate that contributions from qa (U) to the overall LHF uncertainty are on the order of 60 % (25 %). From an instantaneous point of view, random retrieval uncertainties are specifically large over the subtropics with a global average of 37 W m−2. In a climatological sense, their magnitudes become negligible, as do respective sampling uncertainties. Regional and seasonal analyses suggest that largest total LHF uncertainties are seen over the Gulf Stream and the Indian monsoon region during boreal winter. In light of the uncertainty measures, the observed continuous global mean LHF increase up to 2009 needs to be treated with caution. The demonstrated approach can easily be transferred to other satellite retrievals, which increases the significance of the present work.

scholarly journals Tropical Atlantic Moisture Flux, Convection over Northeastern Brazil, and Pertinence of the PIRATA Network*

2005 ◽  
Vol 18 (12) ◽  
pp. 2093-2101 ◽  
Author(s):  
Bruno Durand ◽  
Jacques Servain ◽  
Henri Laurent ◽  
Luiz A. T. Machado
Keyword(s):  
Heat Flux ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Negative Correlation ◽  
Moisture Flux ◽  
Northeastern Brazil ◽  
Trade Wind ◽  
Tropical Atlantic ◽  
Correlation Pattern ◽  
Positive Correlation

Abstract This study aims to examine the relationship between the tropical Atlantic latent heat flux and convective cloud coverage over northeast Brazil (NEB) during the four months of the main rainy season (February–May). The correlation with anomalies of these data is investigated, both without lag and with a 1-month lag (the heat flux in advance). In both cases, a significant positive correlation appears in the northwestern tropical Atlantic, and a significant negative correlation is obtained for a limited area off eastern NEB. These two correlation patterns are linked to anomalies in the trade wind intensity and in the meridional position of the intertropical convergence zone (ITCZ), which relate to the latent heat flux anomalies and NEB convective coverage anomalies, respectively. The positive correlation pattern is spread over a large part of the northern tropical Atlantic, whereas the negative correlation pattern is confined off NEB. This indicates the existence of different regional mechanisms in the tropical Atlantic basin. The impact of the Atlantic heat fluxes on NEB convection is somewhat different from the classical meridional dipole related to the SST variability. The analysis of the horizontal moisture flux shows that during flood years an additional meridional inflow balances the eastward loss, and the upward velocity reinforced over NEB contributes to intensify NEB convection. The positive correlation pattern indicates that the location of the northern branch of the Pilot Research moored Array in the Tropical Atlantic (PIRATA) moorings is pertinent to monitor the ocean–atmosphere interface parameters. The negative correlation pattern off NEB provides new support for the possible extension of the PIRATA array toward the Brazilian coast. Complementary results at 1-month lag and the real-time availability of the PIRATA data confirm the potential of NEB forecasting.

An analog period method for gap‐filling of latent heat flux measurements

2021 ◽  
Author(s):  
Lucas Emilio B. Hoeltgebaum ◽  
Nelson Luís Dias ◽  
Marcelo Azevedo Costa
Keyword(s):  
Heat Flux ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Gap Filling ◽  
Flux Measurements

Scanning 10-W Water Vapor DIAL for the Investigation of Atmospheric Turbulence and Land-Atmosphere Feedback

2021 ◽  
Author(s):  
Andreas Behrendt ◽  
Florian Spaeth ◽  
Volker Wulfmeyer
Keyword(s):  
Heat Flux ◽  
Water Vapor ◽  
Latent Heat ◽  
Atmospheric Turbulence ◽  
Latent Heat Flux ◽  
Climate Models ◽  
Weather Forecast ◽  
Surface Characteristics ◽  
Scanning System ◽  
Forecast Models

<p>We will present recent measurements made with the water vapor differential absorption lidar (DIAL) of University of Hohenheim (UHOH). This scanning system has been developed in recent years for the investigation of atmospheric turbulence and land-atmosphere feedback processes.</p><p>The lidar is housed in a mobile trailer and participated in recent years in a number of national and international field campaigns. We will present examples of vertical pointing and scanning measurements, especially close to the canopy. The water vapor gradients in the surface layer are related to the latent heat flux. Thus, with such low-elevation scans, the latent heat flux distribution over different surface characteristics can be monitored, which is important to verify and improve both numerical weather forecast models and climate models.</p><p>The transmitter of the UHOH DIAL consists of a diode-pumped Nd:YAG laser which pumps a Ti:sapphire laser. The output power of this laser is up to 10 W. Two injection seeders are used to switch pulse-to-pulse between the online and offline signals. These signals are then either directly sent into the atmosphere or coupled into a fiber and guided to a transmitting telescope which is attached to the scanner unit. The receiving telescope has a primary mirror with a dimeter of 80 cm. The backscatter signals are recorded shot to shot and are typically averaged over 0.1 to 1 s.</p>

Sign in / Sign up

Export Citation Format

Share Document