Comparison of sea surface flux measured by instrumented aircraft and ship during SOFIA and SEMAPHORE experiments

Durand, Pierre; Dupuis, Hélène; Lambert, Dominique; Bénech, B.; Druilhet, A.; Katsaros, Kristina B.; Taylor, Peter K.; Weill, Alain

doi:10.1029/97jc03758

Cited by 17 publications

(6 citation statements)

References 36 publications

(9 reference statements)

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“…In this situation (increasing flux and aircraft runs at increasing altitudes) a simple linear extrapolation of the airborne measurements would clearly underestimate the surface heat flux. Such systematic discrepancies between extrapolated fluxes and ground-based measurements were reported several times (Betts et al, 1990(Betts et al, , 1992Grunwald et al, 1996;Durand et al, 1998), and an overview was given by Isaac et al (2004). Systematic measurement errors (e.g.…”

Section: Box Flightsmentioning

confidence: 98%

“…Applying the simple box flight pattern, the number of legs n = 4. Assuming a linear heat flux profile in the CBL the area-averaged fluxes are then extrapolated to the ground (e.g., Durand et al, 1998).…”

Section: Box Flightsmentioning

confidence: 99%

“…This procedure (named the box method in the following) assumes a certain (usually linear) shape of the flux profile across a large portion of the ABL. It has been often applied to estimate the surface sensible heat flux in a CBL (e.g., Betts et al, 1990;Grunwald et al, 1996;Durand et al, 1998). The method is simple, but in comparison with simultaneous ground-based measurements often systematic discrepancies have been observed.…”

Section: Introductionmentioning

confidence: 99%

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A New Method for the Determination of Area-Averaged Turbulent Surface Fluxes from Low-Level Flights Using Inverse Models

Bange

Zittel

Spiess

et al. 2006

Boundary-Layer Meteorol

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The low-level flight method (LLF) has been combined with linear inverse models (IM) resulting in an LLF+IM method for the determination of area-averaged turbulent surface fluxes. With this combination, the vertical divergences of the turbulent latent and sensible heat fluxes were calculated from horizontal flights. The statistical errors of the derived turbulent surface fluxes were significantly reduced. The LLF+IM method was tested both in numerical and field experiments. Large-eddy simulations (LES) were performed to compare 'true' flux profiles with 'measurements' of simulated flights in an idealised convective boundary layer. Small differences between the 'true' and the 'measured' fluxes were found, but the vertical flux divergences were correctly calculated by the LLF+IM method. The LLF+IM method was then applied to data collected during two flights with the Helipod, a turbulence probe carried by a helicopter, and with the research aircraft Do 128 in the LITFASS-98 field campaign. The derived surface fluxes were compared with results from eddy-covariance surface stations and with large-aperture scintillometer data. The comparison showed that the LLF+IM method worked well for the sensible heat flux at 77 and 200 m flight levels, and also for the latent heat flux at the lowest level. The model quality control indicated failures for the latent heat flux at the 200 m level (and higher), which were probably due to large moisture fluctuations that could not be modelled using linear assumptions. Finally the LLF+IM method was applied to more than twenty low-level flights from the LITFASS-2003 experiment. Comparison with aggregated surface flux data revealed good agreement for the sensible heat flux but larger discrepancies and a higher statistical uncertainty for the latent heat flux.

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Section: Box Flightsmentioning

confidence: 98%

Section: Box Flightsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A New Method for the Determination of Area-Averaged Turbulent Surface Fluxes from Low-Level Flights Using Inverse Models

Bange

Zittel

Spiess

et al. 2006

Boundary-Layer Meteorol

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“…Although AMMA was the first scientific campaign during which the plane was operated, the measurement systems and data processing were quite similar to those used on the previous aircraft (e.g. Lambert and Durand, 1998;Durand et al, 1998;Saïd et al, 2005). According to their response time, the signals delivered by the various sensors were generally recorded at a rate ranging from 1 to 50 s −1 .…”

Section: Instrumentation and Data Processingmentioning

confidence: 99%

Seasonal evolution of boundary‐layer turbulence measured by aircraft during the AMMA 2006 Special Observation Period

Saïd

Canut

Durand

et al. 2010

Quart J Royal Meteoro Soc

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International audienceDuring the African Monsoon Multidisciplinary Analysis (AMMA) field campaign, the ATR research aircraft made observations of fluxes and thermodynamics during three 15-day periods, which allowed the seasonal evolution of the atmospheric boundary-layer (ABL) characteristics to be monitored before and after the monsoon onset. As expected, temperature and humidity showed a contrast between dry warm conditions and moister cooler conditions from one period to the other. Most of the time, the wind blew from the west (northwesterly to southwesterly) in the ABL and from the east in the free troposphere. Following rainfall events occuring in July and August, surface sensible heat flux decreased and evaporation increased while the momentum flux remained large in the entire boundary layer, whatever the period. The aim of this paper is to characterize turbulence in terms of fluxes and length-scales for ABLs that exhibit particular characteristics relative to (i) entrainment at the top, (ii) wind rotation at the interface between the monsoon and the Saharan air layer and (iii) seasonal variability. In spite of the poorer accuracy of the turbulent flux estimations at the top of the ABL, the flux profiles were observed to increase or decrease linearly with altitude which enabled accurate estimates of entrainment flux ratios. It was found that the moisture flux distribution in the ABL was governed by top-down processes during the driest period and a mixture of top-down and bottom-up processes during the monsoon period. Significant differences in turbulence length-scales were also highlighted. Copyright © 2009 Royal Meteorological Societ

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“…The fluxes used in this study were filtered values. On the high-frequency range a resolution of 16 s -• is sufficient to achieve a good description of the transfers [Durand et al, 1998]. The sensors must thus have a fast enough response time to capture frequencies at the upper end of the cospectra, while covariance averaging times must be long enough to include frequencies at the lower end [Lenschow and Stankov, 1986;Mahrt, 1997].…”

Section: Actually X'y'= Lim 1 Ix' (T)y' (T)dtmentioning

confidence: 99%

Dynamic and thermodynamic structure of the lower troposphere above rain forest and wet savanna during the EXPRESSO campaign

Delon¹,

Druilhet²,

Delmas³

et al. 2000

J. Geophys. Res.

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Abstract. This paper focuses on the energy budget of atmospheric surface and boundary layers over the wet savanna and the rain forest during the Experiment of Regional Sources and Sinks of Oxidants (EXPRESSO). It assesses dynamic features at the transition between savanna and forest at the beginning of the dry season. The experimental zone was still influenced by the monsoon flow with water vapor mixing ratio of about 16 g/kg. Thermodynamic characteristics of the savanna and forest ecosystems are similar. However, for an equivalent net radiation, evaporation is greater over the forest and leads to lower Bowen ratios (0.2 over the forest, 0.45 over the savanna). Low horizontal winds with no mean direction are observed, due to the proximity of the Intertropical Convergence Zone (ITCZ). However, in spite of low horizontal winds, the momentum flux is high, owing to high drag coefficients and roughness lengths. Some differences appear in the turbulent kinetic energy budget: dynamic and thermal production terms over the forest are nearly half those over the savanna. As a consequence, turbulent exchanges are more efficient over the savanna. Entrainment velocities are deduced from the latent heat flux values at the top of the atmospheric boundary layer (ABL) and from the jump in water vapor mixing ratio between the ABL and the free troposphere. Entrainment velocities are of the same order as subsidence velocities deduced from European Centre Medium-Range Weather Forecasts statistical analyses. High pollution levels are observed in the forest ABL (CO concentration is around 280 ppb). Pollutants, produced by savanna fires, are transported from the free troposphere into the forest ABL by entrainment. Furthermore, horizontal exchanges between the savanna and the forest, induced by large eddies, may occur, increasing the pollution of the forest ABL. Through this study, the ITCZ appears to be an exchange zone rather than a barrier to the transfer of pollutants.

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Comparison of sea surface flux measured by instrumented aircraft and ship during SOFIA and SEMAPHORE experiments

Cited by 17 publications

References 36 publications

A New Method for the Determination of Area-Averaged Turbulent Surface Fluxes from Low-Level Flights Using Inverse Models

A New Method for the Determination of Area-Averaged Turbulent Surface Fluxes from Low-Level Flights Using Inverse Models

Seasonal evolution of boundary‐layer turbulence measured by aircraft during the AMMA 2006 Special Observation Period

Dynamic and thermodynamic structure of the lower troposphere above rain forest and wet savanna during the EXPRESSO campaign

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