scholarly journals Effects of Periodic Tidal Elevations on the Air-Sea Momentum and Turbulent Heat Fluxes in the East China Sea

Atmosphere ◽  
2022 ◽  
Vol 13 (1) ◽  
pp. 90
Author(s):  
Yuting Han ◽  
Yuxin Liu ◽  
Xingwei Jiang ◽  
Mingsen Lin ◽  
Yangang Li ◽  
...  
Keyword(s):  
East China Sea ◽  
Wind Stress ◽  
Heat Fluxes ◽  
Surface Elevation ◽  
East China ◽  
Turbulent Heat ◽  
Sensible Heat ◽  
The East China Sea ◽  
Turbulent Heat Fluxes ◽  
The Mean

Using bulk formulas, two-year platform (fastened to the seabed) hourly observations from 2016 to 2017 in the East China Sea (121.6° E, 32.4° N) are used to investigate the role of the tide-induced surface elevation in changing the fixed observational height and modifying the momentum and air-sea turbulent heat fluxes. The semidiurnal tide-dominated elevation anomalies ranging from −3.6 to 3.9 m change the fixed platform observational height. This change causes hourly differences in the wind stress and latent and sensible heat fluxes between estimates with and without considering surface elevation, with values ranging from −1.5 × 10−3 Nm−2, −10.2 Wm−2, and −3.6 Wm−2 to 2.2 × 10−3 Nm−2, 8.4 Wm−2, and 4.6 Wm−2, respectively. More significant differences occur during spring tides. The differences show weak dependence on the temperature, indicating weak seasonal variations. The mean (maximum) difference percentage relative to the mean magnitude is approximately 3.5% (7%), 1.5% (3%), and 1.5% (3%) for the wind stress and latent and sensible heat fluxes, respectively. The boundary layer stability (BLS) can convert from near-neutral conditions to stable and unstable states in response to tide-induced changes in the observational height, with a probability of occurrence of 2%. Wind anomalies play dominant roles in determining the hourly anomalies of the latent heat flux, regardless of the state of the BLS. Extreme cases, including the cold air outbreak in 2016, tropical cyclones Meranti in 2016, and Ampil in 2018, are also examined. This study will facilitate future observation-reanalysis comparisons in the studied coastal region where ocean–atmosphere-land interactive processes are significant.

Generation and propagation of 21-day bottom pressure variability driven by wind stress curl in the East China Sea

2020 ◽  
Vol 39 (7) ◽  
pp. 91-106
Author(s):  
Hua Zheng ◽  
Xiao-Hua Zhu ◽  
Hirohiko Nakamura ◽  
Jae-Hun Park ◽  
Chanhyung Jeon ◽  
...  
Keyword(s):  
East China Sea ◽  
Wind Stress ◽  
East China ◽  
Bottom Pressure ◽  
The East China Sea ◽  
Wind Stress Curl ◽  
China Sea

The importance of including sea surface current when estimating air-sea turbulent heat fluxes and wind stress in the Gulf Stream region

2020 ◽  
Author(s):  
Xiangzhou Song
Keyword(s):  
Heat Flux ◽  
Wind Stress ◽  
Gulf Stream ◽  
Turbulent Heat Flux ◽  
Heat Fluxes ◽  
Turbulent Heat ◽  
Surface Currents ◽  
Mean Flow ◽  
Geostrophic Currents ◽  
Turbulent Heat Fluxes

AbstractUsing buoy observations from 2004 to 2010 and newly released atmospheric reanalysis and satellite altimetry-derived geostrophic currents from 1993 to 2017, the quantitative contribution of daily mean surface currents to air-sea turbulent heat flux and wind stress uncertainties in the Gulf Stream (GS) region is investigated based on bulk formulas. At four buoy stations, the daily mean latent (sensible) heat flux difference between the estimates with and without surface currents ranges from -18 (-4) to 20 (4) Wm-2, while the daily mean wind stress difference ranges from -0.04 to 0.02 Nm-2. The positive values indicate higher estimates with opposite directions between surface currents and absolute winds. The transition between positive and negative differences is significantly associated with synoptic-scale weather variations. The uncertainties based on buoy observations are approximately 7% and 3% for wind stress and turbulent heat fluxes, respectively. The new reanalysis and satellite geostrophic currents confirm the uncertainties identified by buoy observations with acceptable discrepancies and provide a spatial view of the uncertainty fields. The mean geostrophic currents are aligned with the surface wind along the GS; therefore, the turbulent heat fluxes and wind stress will be ‘underestimated’ with surface currents included. However, on both sides of the GS, the surface flow can be upwind due to possible mechanisms of eddy-mean flow interactions and recirculations, resulting in higher turbulent heat flux estimations. The wind stress and turbulent heat flux uncertainties experience significant seasonal variations and show long-term trends.

An Explicit Algebraic Model for Turbulent Heat Transfer in Wall-Bounded Flow With Streamline Curvature

2006 ◽  
Vol 129 (4) ◽  
pp. 425-433 ◽  
Author(s):  
B. A. Younis ◽  
B. Weigand ◽  
S. Spring
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Heat Flux ◽  
Algebraic Model ◽  
Heat Fluxes ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Streamline Curvature ◽  
Turbulent Heat Fluxes ◽  
The Mean

Fourier’s law, which forms the basis of most engineering prediction methods for the turbulent heat fluxes, is known to fail badly in capturing the effects of streamline curvature on the rate of heat transfer in turbulent shear flows. In this paper, an alternative model, which is both algebraic and explicit in the turbulent heat fluxes and which has been formulated from tensor-representation theory, is presented, and its applicability is extended by incorporating the effects of a wall on the turbulent heat transfer processes in its vicinity. The model’s equations for flows with curvature in the plane of the mean shear are derived and calculations are performed for a heated turbulent boundary layer, which develops over a flat plate before encountering a short region of high convex curvature. The results show that the new model accurately predicts the significant reduction in the wall heat transfer rates wrought by the stabilizing-curvature effects, in sharp contrast to the conventional model predictions, which are shown to seriously underestimate the same effects. Comparisons are also made with results from a complete heat-flux transport model, which involves the solution of differential transport equations for each component of the heat-flux tensor. Downstream of the bend, where the perturbed boundary layer recovers on a flat wall, the comparisons show that the algebraic model yields indistinguishable predictions from those obtained with the differential model in regions where the mean-strain field is in rapid evolution and the turbulence processes are far removed from local equilibrium.

Scintillometry Observations of Sensible and Latent Heat Fluxes over a Boreal Reservoir, Quebec, Canada

2021 ◽  
Author(s):  
Adrien Pierre ◽  
Daniel Nadeau ◽  
Pierre-Érik Isabelle ◽  
Antoine Thiboult ◽  
Alain Rousseau ◽  
...  
Keyword(s):  
Latent Heat ◽  
Regional Scale ◽  
Turbulent Fluxes ◽  
Heat Fluxes ◽  
Water Bodies ◽  
Turbulent Heat ◽  
Sensible Heat ◽  
Near Surface ◽  
Comparison Results ◽  
Turbulent Heat Fluxes

<p>Observations of sensible and latent heat fluxes over inland water bodies are unfortunately scarce and, yet, critical to the development of adequate lake parameterization for numerical weather forecast and climate models. When available, they usually consist of eddy covariance (EC) or lysimeter measurements, both representative of a relatively small footprint area, typically of a few hectares in the case of the EC approach. Over the past decades, we have seen the emergence of bichromatic scintillometry (SC), which allows for a ‘regional’ (~km<sup>2</sup>) estimation of turbulent heat fluxes. In brief, two beams travelling from a set of transmitters to a set of receivers scintillate in the turbulent air above the surface of interest and enable, using the Monin-Obukhov Similarity Theory, the computation of sensible and latent heat fluxes at the land-atmosphere interface. While a handful of studies have looked at the performance of this approach over land surfaces, very few have assessed it over water bodies. This study presents an evaluation of scintillometry-derived turbulent heat fluxes over an 85-km<sup>2</sup> boreal hydropower reservoir of eastern Canada (50.69°N, 63.24°W) with respect to those obtained with EC measurements collected on a nearby floating platform. The scintillometer beam path travelled for 1.7 km over a surface of the reservoir that reached depths of ~100m, from 14 August to 9 October 2019. Results indicate positive, day-and-night, latent heat fluxes throughout the whole period; highlighting that the reservoir steadily released heat over the second half of the open water period, from mid-august until freeze-up. Sensible heat fluxes peaked at night due to the near-surface air temperature vertical gradient reaching its daily maximum. For sensible heat fluxes, the SC approach corroborates well with the EC approach, while for latent heat fluxes, the agreement between EC and SC decreases. This suggests that the larger footprint of the SC system might be affected by heterogeneous surface flux characteristics in the reservoir, which encapsulates the need for large-scale measurements. Grouping results by atmospheric stability regimes does not improve comparison results. These results provide an opportunity to validate an innovative approach for measuring turbulent fluxes at a regional scale and, hence, improving our understanding of turbulent fluxes over large reservoirs and lakes.</p>

scholarly journals Probability Distribution Characteristics for Surface Air–Sea Turbulent Heat Fluxes over the Global Ocean

2012 ◽  
Vol 25 (1) ◽  
pp. 184-206 ◽  
Author(s):  
Sergey K. Gulev ◽  
Konstantin Belyaev
Keyword(s):  
Probability Density ◽  
Interannual Variability ◽  
Probability Distributions ◽  
Heat Fluxes ◽  
Western Boundary ◽  
Turbulent Heat ◽  
Boundary Current ◽  
Turbulent Heat Fluxes ◽  
The Mean ◽  
The Impact

Abstract To analyze the probability density distributions of surface turbulent heat fluxes, the authors apply the two-parametric modified Fisher–Tippett (MFT) distribution to the sensible and latent turbulent heat fluxes recomputed from 6-hourly NCEP–NCAR reanalysis state variables for the period from 1948 to 2008. They derived the mean climatology and seasonal cycle of the location and scale parameters of the MFT distribution. Analysis of the parameters of probability distributions identified the areas where similar surface turbulent fluxes are determined by the very different shape of probability density functions. Estimated extreme turbulent heat fluxes amount to 1500–2000 W m−2 (for the 99th percentile) and can exceed 2000 W m−2 for higher percentiles in the subpolar latitudes and western boundary current regions. Analysis of linear trends and interannual variability in the mean and extreme fluxes shows that the strongest trends in extreme fluxes (more than 15 W m−2 decade−1) in the western boundary current regions are associated with the changes in the shape of distribution. In many regions changes in extreme fluxes may be different from those for the mean fluxes at interannual and decadal time scales. The correlation between interannual variability of the mean and extreme fluxes is relatively low in the tropics, the Southern Ocean, and the Kuroshio Extension region. Analysis of probability distributions in turbulent fluxes has also been used in assessing the impact of sampling errors in the Voluntary Observing Ship (VOS)-based surface flux climatologies, allowed for the estimation of the impact of sampling in extreme fluxes. Although sampling does not have a visible systematic effect on mean fluxes, sampling uncertainties result in the underestimation of extreme flux values exceeding 100 W m−2 in poorly sampled regions.

scholarly journals Spatial variations in the Kuroshio nutrient transport from the East China Sea to south of Japan

2013 ◽  
Vol 10 (4) ◽  
pp. 6737-6762 ◽  
Author(s):  
X. Y. Guo ◽  
X.-H. Zhu ◽  
Y. Long ◽  
D. J. Huang
Keyword(s):  
East China Sea ◽  
East China ◽  
Nitrate Transport ◽  
The East China Sea ◽  
China Sea ◽  
Subsurface Maximum ◽  
Nitrate Flux ◽  
The Mean ◽  
South Of Japan ◽  
The Kuroshio

Abstract. Based on absolute geostrophic velocity calculated from repeated hydrographic data of 39 cruises from 2000 to 2009 and nitrate concentrations measured at the same sections from 1964 to 2011, we obtained temporally averaged nitrate flux (the product of velocity and nitrate concentration) and nitrate transport (integration of flux over a section) through 4 sections along the Kuroshio path from the East China Sea (sections PN and TK) to south of Japan (sections ASUKA and 137E). In addition, we examined section OK east of the Ryukyu Islands in order to understand the contribution of Ryukyu Current to the Kuroshio nutrient transport south of Japan. The mean nitrate flux shows a subsurface maximum core with a value of 10, 10, 11, 11, and 6 mol m–2 s–1 at sections PN, TK, ASUKA, 137E, and OK, respectively. The depth of subsurface maximum core changes among five sections and is approximately 400, 500, 500, 400, and 800 m at sections PN, TK, ASUKA, 137E, and OK respectively. The mean downstream nitrate transport is 199.3, 176.3, 909.2, 1385.5, and 341.2 kmol m–1 at sections PN, TK, ASUKA, 137E, and OK respectively. The nutrient transports at these sections suggest the presence of Kuroshio nutrient stream from its upstream region to downstream. The deep current structure of Ryukyu Current (section OK) makes it contribute more nitrate transport than the Kuroshio in the East China Sea (section TK) to the Kuroshio south of Japan. In addition, the positive difference between the downstream nitrate transport through section ASUKA and the sum of nitrate transports through sections TK and OK, as well as the positive difference of downstream nitrate transport between sections 137E and ASUKA, suggest that the Kuroshio recirculation significantly intensifies the downstream (eastward) nitrate transport by the Kuroshio.

scholarly journals Spatial variations in the Kuroshio nutrient transport from the East China Sea to south of Japan

2013 ◽  
Vol 10 (10) ◽  
pp. 6403-6417 ◽  
Author(s):  
X. Y. Guo ◽  
X.-H. Zhu ◽  
Y. Long ◽  
D. J. Huang
Keyword(s):  
East China Sea ◽  
Nitrate Concentration ◽  
East China ◽  
Nitrate Transport ◽  
The East China Sea ◽  
China Sea ◽  
Nitrate Flux ◽  
The Mean ◽  
South Of Japan ◽  
The Kuroshio

Abstract. Based on absolute geostrophic velocity, which was calculated using repeated hydrographic data of 39 cruises from 2000 to 2009 and nitrate concentrations measured in the same areas from 1964 to 2009, we obtained the temporally averaged nitrate flux (the product of velocity and nitrate concentration) and nitrate transport (integration of flux over one section) of four sections across the Kuroshio from the East China Sea (sections PN and TK) to an area south of Japan (sections ASUKA and 137E). In addition, we examined section OK east of the Ryukyu Islands in order to understand how the Ryukyu Current contributes to the transport of nutrients by the Kuroshio south of Japan. The mean nitrate flux shows a subsurface maximum core with values of 9.6, 10.6, 11.2, 10.5, and 5.7 mol m−2 s−1 at sections PN, TK, ASUKA, 137E, and OK, respectively. The depth of the subsurface maximum core changes among these five sections and is approximately 400, 500, 500, 400, and 800 m at sections PN, TK, ASUKA, 137E, and OK, respectively. The mean downstream nitrate transport is 204.8, 165.8, 879.3, 1230.4, and 338.6 kmol s−1 at sections PN, TK, ASUKA, 137E, and OK, respectively. The transport of nutrients in these sections suggests the presence of the Kuroshio nutrient stream from its upstream to downstream regions. The deep current structure of the Ryukyu Current (section OK) contributes to the same order of nitrate transport as does the Kuroshio from the East China Sea (section TK) to the area south of Japan; however, the former only has one-fifth the volume transport of the latter. A budget calculation suggests that the downstream increase of transported nitrate along the Kuroshio is mainly caused by the recirculation of nitrate into the Kuroshio. This conclusion, however, depends on water depth. In the upper layers (< 26.5σθ), the downstream change of nitrate concentration along the Kuroshio and that from the recirculation of nitrate has a significant contribution to the downstream increase of nitrate transport along the Kuroshio. In the deep layers (> 26.5σθ), the change in nitrate concentration is small and the Kuroshio recirculation dominates the downstream increase of nitrate transport.

scholarly journals Effects of flooding on organic carbon consumption in the East China Sea

2015 ◽  
Vol 12 (7) ◽  
pp. 5609-5639 ◽  
Author(s):  
C.-C. Chen ◽  
G.-C. Gong ◽  
W.-C. Chou ◽  
C.-C. Chung ◽  
F.-K. Shiah ◽  
...  
Keyword(s):  
East China Sea ◽  
Sea Surface Salinity ◽  
East China ◽  
Community Respiration ◽  
The East China Sea ◽  
Surface Salinity ◽  
Mean Values ◽  
China Sea ◽  
Flood Period ◽  
The Mean

Abstract. This study was designed to determine the effects of flooding on plankton community respiration (CR) in the East China Sea (ECS). In July 2010, a devastating flood occurred in the Changjiang River; the mean monthly discharge was 60 527 m3 s−1. To compare, the variables were also examined in the low riverine flow of July 2009 (33 955 m3 s−1). During the flooding, the Changjiang diluted water (CDW) zone, the sea surface salinity (SSS) was ≤ 31 psu, covering almost two thirds of the ECS, which was approximately six times that in the non-flooding period. The mean nitrate concentration was higher in 2010 (6.2 μM) than in 2009 (2.0 μM). However, in the 2010 flood, the mean values of Chl a and the bacterial biomass were only slightly higher or even lower than in 2009. Surprisingly, however, the CR was still higher in the flood period than in the non-flood period, with mean values of 105.6 and 73.2 mg C m−3 d−1, respectively. The higher CR in 2010 could be attributed to vigorous plankton activities, especially phytoplankton, at stations in the CDW zone, which were not mostly covered by low SSS in 2009. There was a huge amount of fCO2 drawdown in the 2010 flood. These results suggested that the devastating flood in 2010 had a significant effect on the carbon balance in the ECS. This effect might become more pronounced as extreme rainfall events and flooding magnitudes increase dramatically throughout the world.

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