Observed extreme air-sea heat flux variations during three tropical cyclones in the tropical southeastern Indian Ocean

2021 ◽  
pp. 1-77
Author(s):  
Xiangzhou Song ◽  
Chunlin Ning ◽  
Yongliang Duan ◽  
Huiwu Wang ◽  
Chao Li ◽  
...  
Keyword(s):  
Heat Flux ◽  
Indian Ocean ◽  
Tropical Cyclones ◽  
Heat Fluxes ◽  
Shortwave Radiation ◽  
Turbulent Heat ◽  
Maximum Magnitude ◽  
Surface Cooling ◽  
Mean Values ◽  
The Mean

AbstractSix-month buoy-based heat flux observations from the poorly sampled tropical southeastern Indian Ocean are examined to document the extremes during three tropical cyclones (TCs) from December 2018 to May 2019. The most striking feature at the mooring site (115.2°E, 16.9°S) during the TCs is the extensively suppressed diurnal cycle of net surface flux, with a mean daytime (nighttime) reduction of 470 (131) W m-2, a peak decrease at approximately noon of 695 W m-2 and an extreme drop during TC Riley of 800 W m-2. The mean surface cooling in the daytime is primarily contributed by the 370 W m-2 decrease in shortwave radiation associated with the increased cloudiness. The air-sea turbulent heat fluxes increase by approximately 151 W m-2 in response to the enhanced wind speed under near-neutral boundary conditions. The daily mean rainfall-induced cooling is 8 W m-2, with a maximum magnitude of 90 W m-2. The mean values, seasonal variation, and synoptic variability of the characteristic heat fluxes are used to assess the new reanalysis data from ERA5 and MERRA2 and the analyzed OAFlux. The overall performance of the high-frequency net heat flux estimates at the synoptic scale is satisfactory, but the four flux components exhibit different quality levels. A serious error is that ERA5 and MERRA2 poorly represent TCs, and they show significant daily mean Qnet biases with opposite directions, -59 W m-2 (largely due to the overestimated latent heat with a bias of -76 W m-2) and 50 W m-2 (largely due to the overestimated shortwave radiation with a bias of 41 W m-2), respectively.

Vertical Structure of the Upper–Indian Ocean Thermal Variability

2020 ◽  
Vol 33 (17) ◽  
pp. 7233-7253 ◽  
Author(s):  
Yuanlong Li ◽  
Weiqing Han ◽  
Fan Wang ◽  
Lei Zhang ◽  
Jing Duan
Keyword(s):  
Heat Flux ◽  
Indian Ocean ◽  
Time Scale ◽  
Vertical Structure ◽  
Southern Oscillation ◽  
Linear Trend ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Shortwave Radiation ◽  
Turbulent Heat

AbstractMulti-time-scale variabilities of the Indian Ocean (IO) temperature over 0–700 m are revisited from the perspective of vertical structure. Analysis of historical data for 1955–2018 identifies two dominant types of vertical structures that account for respectively 70.5% and 21.2% of the total variance on interannual-to-interdecadal time scales with the linear trend and seasonal cycle removed. The leading type manifests as vertically coherent warming/cooling with the maximal amplitude at ~100 m and exhibits evident interdecadal variations. The second type shows a vertical dipole structure between the surface (0–60 m) and subsurface (60–400 m) layers and interannual-to-decadal fluctuations. Ocean model experiments were performed to gain insights into underlying processes. The vertically coherent, basinwide warming/cooling of the IO on an interdecadal time scale is caused by changes of the Indonesian Throughflow (ITF) controlled by Pacific climate and anomalous surface heat fluxes partly originating from external forcing. Enhanced changes in the subtropical southern IO arise from positive air–sea feedback among sea surface temperature, winds, turbulent heat flux, cloud cover, and shortwave radiation. Regarding dipole-type variability, the basinwide surface warming is induced by surface heat flux forcing, and the subsurface cooling occurs only in the eastern IO. The cooling in the southeast IO is generated by the weakened ITF, whereas that in the northeast IO is caused by equatorial easterly winds through upwelling oceanic waves. Both El Niño–Southern Oscillation (ENSO) and IO dipole (IOD) events are favorable for the generation of such vertical dipole anomalies.

scholarly journals Annual, Seasonal, and Interannual Variability of Air–Sea Heat Fluxes in the Indian Ocean

2007 ◽  
Vol 20 (13) ◽  
pp. 3190-3209 ◽  
Author(s):  
Lisan Yu ◽  
Xiangze Jin ◽  
Robert A. Weller
Keyword(s):  
Heat Flux ◽  
Indian Ocean ◽  
Interannual Variability ◽  
Seasonal Cycle ◽  
Arabian Sea ◽  
Heat Fluxes ◽  
The Other ◽  
Net Heat Flux ◽  
The Indian Ocean ◽  
The Mean

Abstract This study investigated the accuracy and physical representation of air–sea surface heat flux estimates for the Indian Ocean on annual, seasonal, and interannual time scales. Six heat flux products were analyzed, including the newly developed latent and sensible heat fluxes from the Objectively Analyzed Air–Sea Heat Fluxes (OAFlux) project and net shortwave and longwave radiation results from the International Satellite Cloud Climatology Project (ISCCP), the heat flux analysis from the Southampton Oceanography Centre (SOC), the National Centers for Environmental Prediction reanalysis 1 (NCEP1) and reanalysis-2 (NCEP2) datasets, and the European Centre for Medium-Range Weather Forecasts operational (ECMWF-OP) and 40-yr Re-Analysis (ERA-40) products. This paper presents the analysis of the six products in depicting the mean, the seasonal cycle, and the interannual variability of the net heat flux into the ocean. Two time series of in situ flux measurements, one taken from a 1-yr Arabian Sea Experiment field program and the other from a 1-month Joint Air–Sea Monsoon Interaction Experiment (JASMINE) field program in the Bay of Bengal were used to evaluate the statistical properties of the flux products over the measurement periods. The consistency between the six products on seasonal and interannual time scales was investigated using a standard deviation analysis and a physically based correlation analysis. The study has three findings. First of all, large differences exist in the mean value of the six heat flux products. Part of the differences may be attributable to the bias in the numerical weather prediction (NWP) models that underestimates the net heat flux into the Indian Ocean. Along the JASMINE ship tracks, the four NWP modeled mean fluxes all have a sign opposite to the observations, with NCEP1 being underestimated by 53 W m−2 (the least biased) and ECMWF-OP by 108 W m−2 (the most biased). At the Arabian Sea buoy site, the NWP mean fluxes also have an underestimation bias, with the smallest bias of 26 W m−2 (ERA-40) and the largest bias of 69 W m−2 (NCEP1). On the other hand, the OAFlux+ISCCP has the best comparison at both measurement sites. Second, the bias effect changes with the time scale. Despite the fact that the mean is biased significantly, there is no major bias in the seasonal cycle of all the products except for ECMWF-OP. The latter does not have a fixed mean due to the frequent updates of the model platform. Finally, among the four products (OAFlux+ISCCP, ERA-40, NCEP1, and NCEP2) that can be used for studying interannual variability, OAFlux+ISCCP and ERA-40 Qnet have good consistency as judged from both statistical and physical measures. NCEP1 shows broad agreement with the two products, with varying details. By comparison, NCEP2 is the least representative of the Qnet variabilities over the basin scale.

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.

The Effect of Soil on the Summertime Surface Energy Budget of a Humid Subarctic Tundra in Northern Quebec, Canada

2021 ◽  
Vol 22 (10) ◽  
pp. 2547-2564
Author(s):  
Georg Lackner ◽  
Daniel F. Nadeau ◽  
Florent Domine ◽  
Annie-Claude Parent ◽  
Gonzalo Leonardini ◽  
...  
Keyword(s):  
Heat Flux ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Land Surface ◽  
Sensible Heat Flux ◽  
Arctic Region ◽  
Heat Fluxes ◽  
Surface Energy Budget ◽  
Turbulent Heat ◽  
Turbulent Heat Fluxes

AbstractRising temperatures in the southern Arctic region are leading to shrub expansion and permafrost degradation. The objective of this study is to analyze the surface energy budget (SEB) of a subarctic shrub tundra site that is subject to these changes, on the east coast of Hudson Bay in eastern Canada. We focus on the turbulent heat fluxes, as they have been poorly quantified in this region. This study is based on data collected by a flux tower using the eddy covariance approach and focused on snow-free periods. Furthermore, we compare our results with those from six Fluxnet sites in the Arctic region and analyze the performance of two land surface models, SVS and ISBA, in simulating soil moisture and turbulent heat fluxes. We found that 23% of the net radiation was converted into latent heat flux at our site, 35% was used for sensible heat flux, and about 15% for ground heat flux. These results were surprising considering our site was by far the wettest site among those studied, and most of the net radiation at the other Arctic sites was consumed by the latent heat flux. We attribute this behavior to the high hydraulic conductivity of the soil (littoral and intertidal sediments), typical of what is found in the coastal regions of the eastern Canadian Arctic. Land surface models overestimated the surface water content of those soils but were able to accurately simulate the turbulent heat flux, particularly the sensible heat flux and, to a lesser extent, the latent heat flux.

An explicit algebraic Reynolds-stress and scalar-flux model for stably stratified flows

2013 ◽  
Vol 723 ◽  
pp. 91-125 ◽  
Author(s):  
W. M. J. Lazeroms ◽  
G. Brethouwer ◽  
S. Wallin ◽  
A. V. Johansson
Keyword(s):  
Heat Flux ◽  
Kinetic Energy ◽  
Temperature Gradient ◽  
Reynolds Stress ◽  
Turbulent Heat Flux ◽  
Turbulent Heat ◽  
Homogeneous Shear ◽  
Self Consistent ◽  
The Mean ◽  
Homogeneous Shear Flow

AbstractThis work describes the derivation of an algebraic model for the Reynolds stresses and turbulent heat flux in stably stratified turbulent flows, which are mutually coupled for this type of flow. For general two-dimensional mean flows, we present a correct way of expressing the Reynolds-stress anisotropy and the (normalized) turbulent heat flux as tensorial combinations of the mean strain rate, the mean rotation rate, the mean temperature gradient and gravity. A system of linear equations is derived for the coefficients in these expansions, which can easily be solved with computer algebra software for a specific choice of the model constants. The general model is simplified in the case of parallel mean shear flows where the temperature gradient is aligned with gravity. For this case, fully explicit and coupled expressions for the Reynolds-stress tensor and heat-flux vector are given. A self-consistent derivation of this model would, however, require finding a root of a polynomial equation of sixth-order, for which no simple analytical expression exists. Therefore, the nonlinear part of the algebraic equations is modelled through an approximation that is close to the consistent formulation. By using the framework of a$K\text{{\ndash}} \omega $model (where$K$is turbulent kinetic energy and$\omega $an inverse time scale) and, where needed, near-wall corrections, the model is applied to homogeneous shear flow and turbulent channel flow, both with stable stratification. For the case of homogeneous shear flow, the model predicts a critical Richardson number of 0.25 above which the turbulent kinetic energy decays to zero. The channel-flow results agree well with DNS data. Furthermore, the model is shown to be robust and approximately self-consistent. It also fulfils the requirements of realizability.

The Importance of Relative Wind Speed in Estimating Air–Sea Turbulent Heat Fluxes in Bulk Formulas: Examples in the Bohai Sea

2020 ◽  
Vol 37 (4) ◽  
pp. 589-603 ◽  
Author(s):  
Xiangzhou Song
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Wind Speed ◽  
Bohai Sea ◽  
Heat Fluxes ◽  
Turbulent Heat ◽  
Surface Currents ◽  
The Bohai Sea ◽  
Turbulent Heat Fluxes ◽  
Relative Wind

AbstractSea surface currents are commonly neglected when estimating the air–sea turbulent heat fluxes in bulk formulas. Using buoy observations in the Bohai Sea, this paper investigated the effects of near-coast multiscale currents on the quantification of turbulent heat fluxes, namely, latent heat flux (LH) and sensible heat flux (SH). The maximum current reached 1 m s−1 in magnitude, and a steady northeastward current of 0.16 m s−1 appeared in the southern Bohai Strait. The predominant tidal signal was the semidiurnal current, followed by diurnal components. The mean absolute surface wind was from the northeast with a speed of approximately 3 m s−1. The surface winds at a height of 11 m were dominated by the East Asian monsoon. As a result of upwind flow, the monthly mean differences in LH and SH between the estimates with and without surface currents ranged from 1 to 2 W m−2 in July (stable boundary layer) and November (unstable boundary layer). The hourly differences were on average 10 W m−2 and ranged from 0 to 24 W m−2 due to changes in the relative wind speed by high-frequency rotating surface tidal currents. The diurnal variability in LH/SH was demonstrated under stable and unstable boundary conditions. Observations provided an accurate benchmark for flux comparisons. The newly updated atmospheric reanalysis products MERRA-2 and ERA5 were superior to the 1° OAFlux data at this buoy location. However, future efforts in heat flux computation are still needed to, for example, consider surface currents and resolve diurnal variations.

scholarly journals Air–Sea Turbulent Heat Fluxes in Climate Models and Observational Analyses: What Drives Their Variability?

2019 ◽  
Vol 32 (8) ◽  
pp. 2397-2421 ◽  
Author(s):  
R. Justin Small ◽  
Frank O. Bryan ◽  
Stuart P. Bishop ◽  
Robert A. Tomas
Keyword(s):  
Heat Flux ◽  
Climate Models ◽  
Climate Model ◽  
Turbulent Heat Flux ◽  
Heat Fluxes ◽  
Small Scale ◽  
Turbulent Heat ◽  
Realistic Representation ◽  
Frontal Zones ◽  
The Tropics

Abstract A traditional view is that the ocean outside of the tropics responds passively to atmosphere forcing, which implies that air–sea heat fluxes are mainly driven by atmosphere variability. This paper tests this viewpoint using state-of-the-art air–sea turbulent heat flux observational analyses and a climate model run at different resolutions. It is found that in midlatitude ocean frontal zones the variability of air–sea heat fluxes is not predominantly driven by the atmosphere variations but instead is forced by sea surface temperature (SST) variations arising from intrinsic oceanic variability. Meanwhile in most of the tropics and subtropics wind is the dominant driver of heat flux variability, and atmosphere humidity is mainly important in higher latitudes. The predominance of ocean forcing of heat fluxes found in frontal regions occurs on scales of around 700 km or less. Spatially smoothing the data to larger scales results in the traditional atmosphere-driving case, while filtering to retain only small scales of 5° or less leads to ocean forcing of heat fluxes over most of the globe. All observational analyses examined (1° OAFlux; 0.25° J-OFURO3; 0.25° SeaFlux) show this general behavior. A standard resolution (1°) climate model fails to reproduce the midlatitude, small-scale ocean forcing of heat flux: refining the ocean grid to resolve eddies (0.1°) gives a more realistic representation of ocean forcing but the variability of both SST and of heat flux is too high compared to observational analyses.

scholarly journals Decadal SST Variability in the Southeast Indian Ocean and Its Impact on Regional Climate

2019 ◽  
Vol 32 (19) ◽  
pp. 6299-6318 ◽  
Author(s):  
Yuanlong Li ◽  
Weiqing Han ◽  
Lei Zhang ◽  
Fan Wang
Keyword(s):  
Heat Flux ◽  
Wind Speed ◽  
Indian Ocean ◽  
General Circulation Model ◽  
General Circulation ◽  
Circulation Model ◽  
Turbulent Heat ◽  
Central Pacific ◽  
Offshore Area ◽  
Sst Variability

Abstract The southeast Indian Ocean (SEIO) exhibits decadal variability in sea surface temperature (SST) with amplitudes of ~0.2–0.3 K and covaries with the central Pacific (r = −0.63 with Niño-4 index for 1975–2010). In this study, the generation mechanisms of decadal SST variability are explored using an ocean general circulation model (OGCM), and its impact on atmosphere is evaluated using an atmospheric general circulation model (AGCM). OGCM experiments reveal that Pacific forcing through the Indonesian Throughflow explains <20% of the total SST variability, and the contribution of local wind stress is also small. These wind-forced anomalies mainly occur near the Western Australian coast. The majority of SST variability is attributed to surface heat fluxes. The reduced upward turbulent heat flux (QT; latent plus sensible heat flux), owing to decreased wind speed and anomalous warm, moist air advection, is essential for the growth of warm SST anomalies (SSTAs). The warming causes reduction of low cloud cover that increases surface shortwave radiation (SWR) and further promotes the warming. However, the resultant high SST, along with the increased wind speed in the offshore area, enhances the upward QT and begins to cool the ocean. Warm SSTAs co-occur with cyclonic low-level wind anomalies in the SEIO and enhanced rainfall over Indonesia and northwest Australia. AGCM experiments suggest that although the tropical Pacific SST has strong effects on the SEIO region through atmospheric teleconnection, the cyclonic winds and increased rainfall are mainly caused by the SEIO warming through local air–sea interactions.

scholarly journals Analysis of a 3 year meteorological record from the ablation zone of Morteratschgletscher, Switzerland: energy and mass balance

2000 ◽  
Vol 46 (155) ◽  
pp. 571-579 ◽  
Author(s):  
J. Oerlemans
Keyword(s):  
Heat Flux ◽  
Sensible Heat Flux ◽  
Longwave Radiation ◽  
Solar Radiation Pressure ◽  
Turbulent Energy ◽  
Snow Accumulation ◽  
Shortwave Radiation ◽  
Glacier Surface ◽  
The Mean ◽  
Snow Temperature

AbstractSince 1 October 1995, an automatic weather station has been operated on the tongue of Morteratschgletscher, Switzerland. The station stands freely on the ice, and sinks with the melting glacier surface. It is located at 2100 m a.s.l., and measures air temperature, wind speed and direction, incoming and reflected solar radiation, pressure and snow temperature. A sonic ranger, mounted to stakes drilled into the ice, measures surface height from which melt rates and snow accumulation can be derived. In this paper the data for the period 1 October 1995 to 30 September 1998 are used to evaluate the surface energy balance. The turbulent energy fluxes are calculated with the bulk method. The turbulent exchange coefficient Ch is used as a control parameter. With Ch = 0.00127 the calculated melt equals the observed melt, which is 17.70 m w.e. over the 3 years. When averaged over the time when melting occurs (i.e. 35% of the time), the mean surface heat flux equals 191 W m−2. Net shortwave radiation contributes 177 W m−2, net longwave radiation −25 W m−2, the sensible-heat flux 31 W m−2 and the latent-heat flux 8 W m−2.

A Comparison of Southern Ocean Air–Sea Buoyancy Flux from an Ocean State Estimate with Five Other Products

2011 ◽  
Vol 24 (24) ◽  
pp. 6283-6306 ◽  
Author(s):  
Ivana Cerovečki ◽  
Lynne D. Talley ◽  
Matthew R. Mazloff
Keyword(s):  
Heat Flux ◽  
Southern Ocean ◽  
Heat Loss ◽  
Large Scale ◽  
Heat Fluxes ◽  
Buoyancy Flux ◽  
Western Boundary ◽  
Turbulent Heat ◽  
Radiative Fluxes ◽  
State Estimate

Abstract The authors have intercompared the following six surface buoyancy flux estimates, averaged over the years 2005–07: two reanalyses [the recent ECMWF reanalysis (ERA-Interim; hereafter ERA), and the National Centers for Environmental Prediction (NCEP)–NCAR reanalysis 1 (hereafter NCEP1)], two recent flux products developed as an improvement of NCEP1 [the flux product by Large and Yeager and the Southern Ocean State Estimate (SOSE)], and two ad hoc air–sea flux estimates that are obtained by combining the NCEP1 or ERA net radiative fluxes with turbulent flux estimates using the Coupled Ocean–Atmosphere Response Experiment (COARE) 3.0 bulk formulas with NCEP1 or ERA input variables. The accuracy of SOSE adjustments of NCEP1 atmospheric fields (which SOSE uses as an initial guess and a constraint) was assessed by verification that SOSE reduces the biases in the NCEP1 fluxes as diagnosed by the Working Group on Air–Sea Fluxes (Taylor), suggesting that oceanic observations may be a valuable constraint to improve atmospheric variables. Compared with NCEP1, both SOSE and Large and Yeager increase the net ocean heat loss in high latitudes, decrease ocean heat loss in the subtropical Indian Ocean, decrease net evaporation in the subtropics, and decrease net precipitation in polar latitudes. The large-scale pattern of SOSE and Large and Yeager turbulent heat flux adjustment is similar, but the magnitude of SOSE adjustments is significantly larger. Their radiative heat flux adjustments patterns differ. Turbulent heat fluxes determined by combining COARE bulk formulas with NCEP1 or ERA should not be combined with unmodified NCEP1 or ERA radiative fluxes as the net ocean heat gain poleward of 25°S becomes unrealistically large. The other surface flux products (i.e., NCEP1, ERA, Large and Yeager, and SOSE) balance more closely. Overall, the statistical estimates of the differences between the various air–sea heat flux products tend to be largest in regions with strong ocean mesoscale activity such as the Antarctic Circumpolar Current and the western boundary currents.

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