Sensitivity and predictive uncertainty of the ACASA model  at a spruce forest site

Staudt, Katharina; Falge, Eva; Pyles, R. D.; Foken, Thomas

doi:10.5194/bg-7-3685-2010

Cited by 54 publications

(23 citation statements)

References 85 publications

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“…Therefore, we estimated the ground surface from measurements of the projected plant surface neglecting stem and understory contributions. The average PAI (Plant Area Index) of this forest stand is 5 m 2 m −2 (Staudt et al, 2010). This projected area can be converted to a surface area by multiplying with π for wooden parts (assuming they are round), which contribute about 20% (5-35% (Gower et al, 1999)) to the PAI and by a factor of 2.65 derived by Oren et al (1986) to convert the projected LAI (∼ 80% of PAI) to the geometric needle surface.…”

Section: S/v Ground Versus S/v Aerosolmentioning

confidence: 99%

Simultaneous HONO measurements in and above a forest canopy: influence of turbulent exchange on mixing ratio differences

et al. 2011

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Abstract.We have combined chemical and micrometeorological measurements to investigate the formation and distribution of HONO throughout a forest canopy. HONO was measured simultaneously at two heights, close to the forest floor and just above canopy. The turbulent exchange between the forest and the atmosphere above was studied using vertical profiles of eddy covariance measurements of wind velocity, sonic temperature, water vapour and CO 2 . HONO mixing ratios at both heights showed typical diel cycles with low daytime values (∼80 ppt) and high nighttime values (up to 500 ppt), but were influenced by various sources and sinks leading to mixing ratio differences (above canopy minus below) of up to +240 ppt at nighttime. In the late afternoon and early night mixing ratios increased at higher rates near the forest floor, indicating a possible ground source. Due to the simultaneous decoupling of the forest from the air layer above the canopy, mixing ratio differences reached about −170 ppt. From the late night until the early morning mixing ratios above the forest were typically higher than close to the forest floor. For some cases, this could be attributed to advection above the forest, which only partly penetrated the canopy. Measured photolysis frequencies above and below the forest canopy differed by a factor of 10-25 resulting in HONO lifetimes of about 10 min above and 100-250 min below the canopy at noontime. However, these differences of the main daytime HONO sink were not evident in the mixing ratio differences, which were close to zero during the morning hours. Effective turbulent exchange due to a complete coupling of the forest to the air layer above the canopy in Correspondence to: M. Sörgel (matthias.soergel@uni-bayreuth.de) the morning has offset the differences caused by the daytime photolytic sink and added to the interplay between different HONO production and loss processes.

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Section: S/v Ground Versus S/v Aerosolmentioning

confidence: 99%

Simultaneous HONO measurements in and above a forest canopy: influence of turbulent exchange on mixing ratio differences

et al. 2011

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“…In a few studies, the authors decided to use the raw flux data without closing the energy balance. This decision to use a third method was made because either the authors were interested in flux patterns rather than total fluxes (Carrer et al, 2012) or they had doubts about the correctness of the Bowen ratio method (Staudt et al, 2010). Recently, based on arguments raised by Foken (2008) and experimental findings of Mauder and Foken (2006), a fourth method was proposed.…”

Section: Introductionmentioning

confidence: 99%

On the use of the post-closure methods uncertainty band to evaluate the performance of land surface models against eddy covariance flux data

et al. 2015

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Abstract. The energy balance of eddy covariance (EC) flux data is normally not closed. Therefore, at least if used for modelling, EC flux data are usually post-closed, i.e. the measured turbulent fluxes are adjusted so as to close the energy balance. At the current state of knowledge, however, it is not clear how to partition the missing energy in the right way. Eddy flux data therefore contain some uncertainty due to the unknown nature of the energy balance gap, which should be considered in model evaluation and the interpretation of simulation results. We propose to construct the post-closure methods uncertainty band (PUB), which essentially designates the differences between non-adjusted flux data and flux data adjusted with the three post-closure methods (Bowen ratio, latent heat flux (LE) and sensible heat flux (H ) method). To demonstrate this approach, simulations with the NOAH-MP land surface model were evaluated based on EC measurements conducted at a winter wheat stand in southwest Germany in 2011, and the performance of the Jarvis and Ball-Berry stomatal resistance scheme was compared. The width of the PUB of the LE was up to 110 W m −2 (21 % of net radiation). Our study shows that it is crucial to account for the uncertainty in EC flux data originating from lacking energy balance closure. Working with only a single post-closing method might result in severe misinterpretations in model-data comparisons.

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“…The model was modified in three parts. The first change relates to the soil respiration calculations and was already examined by Staudt et al (2010) for spruce. The original soil moisture 30 attenuation factor was disabled because it not only reduced soil microbial respiration during dry periods, but also enhanced respiration rates to unreasonably high values during wet periods.…”

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confidence: 99%

“…The second change according to Staudt et al (2010) was made to the calculation of photosynthesis. Originally, in the plant physiology sub-module, the temperature dependence of the maximum catalytic activity of Rubisco at saturated ribulose biphosphate (RuBP) and saturated CO 2 , V cmax (µmol m…”

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confidence: 99%

Application of the ACASA model for a spruce forest and a nearby patchy clearing

Gatzsche¹,

Babel²,

Pyles³

et al. 2017

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Abstract. The ACASA (Advanced Canopy-Atmosphere-Soil Algorithm) model, with a higher order closure for tall vegetation, has already been successfully tested and validated for spruce forests. The aim of this paper is the further application for a clearing with a heterogeneous structure of the underlying surface. The comparison with flux data shows a good agreement with a footprint aggregated tile approach of the model. However, the results of a comparison with a tile approach on the basis of the mean land use classification of the clearing is not significantly different. It is assumed that the footprint model is not accurate 5 enough to separate small scale heterogeneities. All measured fluxes are corrected for energy balance closure with a Bowen ratio and a buoyancy flux correction method. The comparison with the model -where the energy balance is closed -shows that the buoyancy correction for Bowen ratios > 1.5 better fits the measured data. For lower Bowen ratios, the correction probably lies between both methods, but the amount of available data was too small to make a conclusion. With an assumption of a similarity between water and carbon dioxide fluxes, no correction of the net ecosystem exchange is necessary for Bowen ratios 10 > 1.5.

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Sensitivity and predictive uncertainty of the ACASA model at a spruce forest site

Cited by 54 publications

References 85 publications

Simultaneous HONO measurements in and above a forest canopy: influence of turbulent exchange on mixing ratio differences

Simultaneous HONO measurements in and above a forest canopy: influence of turbulent exchange on mixing ratio differences

On the use of the post-closure methods uncertainty band to evaluate the performance of land surface models against eddy covariance flux data

Application of the ACASA model for a spruce forest and a nearby patchy clearing

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