scholarly journals Deriving Photosynthetically Active Radiation at ground level in cloud-free conditions from Copernicus Atmospheric Monitoring Service (CAMS) products

2018 ◽  
Author(s):  
William Wandji Nyamsi ◽  
Phillipe Blanc ◽  
John A. Augustine ◽  
Antti Arola ◽  
Lucien Wald
Keyword(s):  
Photosynthetically Active Radiation ◽  
Ground Level ◽  
Photosynthetic Photon Flux Density ◽  
Surface Radiation ◽  
Coefficient Of Determination ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Distribution Method ◽  
Active Radiation ◽  
Monitoring Service

Abstract. A method is described that estimates the photosynthetically active radiation (PAR) at ground level in cloud-free conditions. It uses a fast approximation of the libRadtran radiative transfer numerical model, known as the k-distribution method and the correlated-k approximation of Kato et al. (1999). LibRadtran provides irradiances aggregated over several fixed spectral bands and a spectral resampling is proposed followed by an aggregation in the range [400, 700] nm. The Copernicus Atmosphere Monitoring Service (CAMS) produces daily estimates of the aerosol properties, and total column contents in water vapor and ozone that are input to the method. A comparison of the results is performed against instantaneous measurements of global Photosynthetic Photon Flux Density (PPFD) on a horizontal plane made in cloud-free conditions at seven sites of the Surface Radiation network (SURFRAD) in the USA in various climates. The bias ranges between −12 µmol m−2 s−1 (−1 % of the mean value at Desert Rock) and +61 µmol m−2 s−1 (+5 % at Penn. State Univ). The root mean square error ranges from 37 µmol m−2 s−1 (3 %) to 82 µmol m−2 s−1 (6 %). The coefficient of determination R2 ranges between 0.97 and 0.99. This work demonstrates the quality of the proposed method combined with the CAMS products.

scholarly journals A New Clear-Sky Method for Assessing Photosynthetically Active Radiation at the Surface Level

Atmosphere ◽  
2019 ◽  
Vol 10 (4) ◽  
pp. 219
Author(s):  
William Wandji Nyamsi ◽  
Philippe Blanc ◽  
John A. Augustine ◽  
Antti Arola ◽  
Lucien Wald
Keyword(s):  
Photosynthetically Active Radiation ◽  
Photosynthetic Photon Flux Density ◽  
Surface Radiation ◽  
Radiation Budget ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Distribution Method ◽  
Active Radiation ◽  
Surface Level ◽  
Clear Sky

A clear–sky method to estimate the photosynthetically active radiation (PAR) at the surface level in cloudless atmospheres is presented and validated. It uses a fast and accurate approximation adopted in several radiative transfer models, known as the k-distribution method and the correlated-k approximation, which gives a set of fluxes accumulated over 32 established wavelength intervals. A resampling technique, followed by a summation, are applied over the wavelength range [0.4, 0.7] µm in order to retrieve the PAR fluxes. The method uses as inputs the total column contents of ozone and water vapor, and optical properties of aerosols provided by the Copernicus Atmosphere Monitoring Service. To validate the method, its outcomes were compared to instantaneous global photosynthetic photon flux density (PPFD) measurements acquired at seven experimental sites of the Surface Radiation Budget Network (SURFRAD) located in various climates in the USA. The bias lies in the interval [−12, 61] µmol m−2 s−1 ([−1, 5] % in values relative to the means of the measurements at each station). The root mean square error ranges between 37 µmol m−2 s−1 (3%) and 82 µmol m−2 s−1 (6%). The squared correlation coefficient fluctuates from 0.97 to 0.99. This comparison demonstrates the high level of accuracy of the presented method, which offers an accurate estimate of PAR fluxes in cloudless atmospheres at high spatial and temporal resolutions useful for several bio geophysical models.

scholarly journals Estimating the photosynthetically active radiation under clear skies by means of a new approach

2015 ◽  
Vol 12 (1) ◽  
pp. 5-10 ◽  
Author(s):  
W. Wandji Nyamsi ◽  
B. Espinar ◽  
P. Blanc ◽  
L. Wald
Keyword(s):  
Root Mean Square Error ◽  
Mean Square Error ◽  
Root Mean Square ◽  
Photosynthetically Active Radiation ◽  
Photon Flux ◽  
Transfer Model ◽  
Mean Square ◽  
Distribution Method ◽  
Active Radiation ◽  
Spectral Bands

Abstract. The k-distribution method and the correlated-k approximation of Kato et al. (1999) is a computationally efficient approach originally designed for calculations of the broadband solar radiation by dividing the solar spectrum in 32 specific spectral bands from 240 to 4606 nm. This paper describes a technique for an accurate assessment of the photosynthetically active radiation (PAR) from 400 to 700 nm at ground level, under clear-sky conditions using twelve of these spectral bands. It is validated against detailed spectral calculations of the PAR made by the radiative transfer model libRadtran. For the direct and global PAR irradiance, the bias is −0.4 W m−2 (−0.2%) and −4 W m−2 (−1.3%) and the root mean square error is 1.8 W m−2 (0.7%) and 4.5 W m−2 (1.5%). For the direct and global Photosynthetic Photon Flux Density, the biases are of about +10.3 μmol m−2 s−1 (+0.8%) and 1.9 μmol m−2 s−1 (−0.1%) respectively, and the root mean square error is 11.4 μmol m−2 s−1 (0.9%) and 4.0 μmol m−2 s−1 (0.3%). The correlation coefficient is greater than 0.99. This technique provides much better results than two state-of-the-art empirical methods computing the daily mean of PAR from the daily mean of broadband irradiance.

scholarly journals A new method for estimating UV fluxes at ground level in cloud-free conditions

2017 ◽  
Vol 10 (12) ◽  
pp. 4965-4978 ◽  
Author(s):  
William Wandji Nyamsi ◽  
Mikko R. A. Pitkänen ◽  
Youva Aoun ◽  
Philippe Blanc ◽  
Anu Heikkilä ◽  
...  
Keyword(s):  
Ground Level ◽  
New Method ◽  
Coefficient Of Determination ◽  
Total Column Ozone ◽  
Distribution Method ◽  
The Mean ◽  
Column Ozone ◽  
Monitoring Service ◽  
Made In

Abstract. A new method has been developed to estimate the global and direct solar irradiance in the UV-A and UV-B at ground level in cloud-free conditions. It is based on a resampling technique applied to the results of the k-distribution method and the correlated-k approximation of Kato et al. (1999) over the UV band. Its inputs are the aerosol properties and total column ozone that are produced by the Copernicus Atmosphere Monitoring Service (CAMS). The estimates from this new method have been compared to instantaneous measurements of global UV irradiances made in cloud-free conditions at five stations at high latitudes in various climates. For the UV-A irradiance, the bias ranges between −0.8 W m−2 (−3 % of the mean of all data) and −0.2 W m−2 (−1 %). The root mean square error (RMSE) ranges from 1.1 W m−2 (6 %) to 1.9 W m−2 (9 %). The coefficient of determination R2 is greater than 0.98. The bias for UV-B is between −0.04 W m−2 (−4 %) and 0.08 W m−2 (+13 %) and the RMSE is 0.1 W m−2 (between 12 and 18 %). R2 ranges between 0.97 and 0.99. This work demonstrates the quality of the proposed method combined with the CAMS products. Improvements, especially in the modeling of the reflectivity of the Earth's surface in the UV region, are necessary prior to its inclusion into an operational tool.

scholarly journals A new method for estimating UV fluxes at ground level in cloud-free conditions

2017 ◽  
Author(s):  
William Wandji Nyamsi ◽  
Mikko R. A. Pitkänen ◽  
Youva Aoun ◽  
Philippe Blanc ◽  
Anu Heikkilä ◽  
...  
Keyword(s):  
Ground Level ◽  
New Method ◽  
Coefficient Of Determination ◽  
Total Column Ozone ◽  
Distribution Method ◽  
The Mean ◽  
Column Ozone ◽  
Monitoring Service ◽  
Made In

Abstract. A new method has been developed to estimate the global and direct solar irradiance in the UV-A and UV-B, at ground level in cloud-free conditions. It is based on a resampling technique applied to the results of the k-distribution method and the correlated-k approximation of Kato et al. (1999) over the UV band. Its inputs are the aerosol properties, and total column ozone that are produced by the Copernicus Atmosphere Monitoring Service (CAMS). The estimates from this new method have been compared to instantaneous measurements of global UV irradiances made in cloud-free conditions at five stations at high latitudes in various climates. For the total or UV-A global irradiance, the bias ranges between −0.8 W m−2 (−3 % of the mean of all data) and −0.2 W m−2 (−1%). The root mean square error (RMSE) ranges from 1.1 W m−2 (6 %) to 1.9 W m−2 (9 %). The coefficient of determination R2 is greater than 0.98. The bias for UV-B is between −0.04 W m−2 (−4 %) and 0.08 W m−2 (+13 %) and the RMSE is 0.1 W m−2 (between 12 % and 18 %). R2 ranges between 0.97 and 0.99. This work demonstrates the quality of the proposed method combined with the CAMS products. Improvements, especially in the modelling of the reflectivity of the Earth's surface in the UV region, are necessary prior its inclusion into an operational tool.

Put out the light, and then put out the light

2000 ◽  
Vol 80 (1) ◽  
pp. 1-25 ◽  
Author(s):  
J.A. Raven ◽  
J.E. Kübler ◽  
J. Beardall
Keyword(s):  
Flux Density ◽  
Photosynthetically Active Radiation ◽  
Protein Turnover ◽  
Energy Input ◽  
Charge Recombination ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Input Rate ◽  
Active Radiation ◽  
Energy Input Rate

The lowest photon flux density of photosynthetically active radiation at which O2-evolving marine photolithotrophs appear to be able to grow is some 10 nmol photon m−2 s−1, while marine non-O2-evolvers can grow at 4 nmol photon m−2 s−1, in both cases with the photon flux density averaged over the 24 hour L:D cycle. Constraints on the ability to grow at very low fluxes of photosynthetically active radiation fall into three categories. Category one includes essential processes whose efficiency is independent of the rate of energy input, but whose catalysts show phylogenetic variation leading to different energy costs for a given process in different taxa, e.g. light-harvesting complexes, RUBISCO and probably in the sensitivity of PsII to photodamage. The second category comprises essential processes whose efficiency decreases with decreasing energy input rate as a result of back-reactions independent of the energy input rate, e.g. charge recombination following charge separation by PsII and short-circuit H+ fluxes across the thylakoid membrane which decrease the fraction of pumped H+ which can be used in adenosine diphosphate phosphorylation. Category two also includes that component of protein turnover which cannot be related to replacement of polypeptides which were incorrectly assembled following uncorrected errors of transcription or translation, or which were damaged by processes whose rate increases with increasing energy input rate such as photodamage to PsII. The third category includes only O2-dependent damage to the D1 protein of PsII whose rate increases with a decreasing incident flux of photosynthetically active radiation. Processes in categories two and three are most likely to impose the lower limit on the photon flux density which can support photolithotrophic growth. The available literature, mainly on organisms which are not adapted to growth at very low photon flux densities, suggests that three major limitations (charge recombination in PsII, H+ leakage and slippage, and protein turnover) can individually impose lower limits in excess of 20 nmol photon m−2 s−1 on photolithotrophic growth. Furthermore, these three limitations are interactive, so that considering all three processes acting in series leads to an even higher predicted lower photon flux density limit for photolithotrophic growth.

scholarly journals LED Illumination Spectrum Manipulation for Increasing the Yield of Sweet Basil (Ocimum basilicum L.)

Plants ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 344
Author(s):  
Md Momtazur Rahman ◽  
Mikhail Vasiliev ◽  
Kamal Alameh
Keyword(s):  
Growth Rate ◽  
Fold Increase ◽  
Photosynthetic Photon Flux Density ◽  
Ocimum Basilicum ◽  
Photon Flux ◽  
Photon Flux Density ◽  
White Led ◽  
Experimental Conditions ◽  
Sweet Basil ◽  
Optimal Illumination

Manipulation of the LED illumination spectrum can enhance plant growth rate and development in grow tents. We report on the identification of the illumination spectrum required to significantly enhance the growth rate of sweet basil (Ocimum basilicum L.) plants in grow tent environments by controlling the LED wavebands illuminating the plants. Since the optimal illumination spectrum depends on the plant type, this work focuses on identifying the illumination spectrum that achieves significant basil biomass improvement compared to improvements reported in prior studies. To be able to optimize the illumination spectrum, several steps must be achieved, namely, understanding plant biology, conducting several trial-and-error experiments, iteratively refining experimental conditions, and undertaking accurate statistical analyses. In this study, basil plants are grown in three grow tents with three LED illumination treatments, namely, only white LED illumination (denoted W*), the combination of red (R) and blue (B) LED illumination (denoted BR*) (relative red (R) and blue (B) intensities are 84% and 16%, respectively) and a combination of red (R), blue (B) and far-red (F) LED illumination (denoted BRF*) (relative red (R), blue (B) and far-red (F) intensities are 79%, 11%, and 10%, respectively). The photosynthetic photon flux density (PPFD) was set at 155 µmol m−2 s−1 for all illumination treatments, and the photoperiod was 20 h per day. Experimental results show that a combination of blue (B), red (R), and far-red (F) LED illumination leads to a one-fold increase in the yield of a sweet basil plant in comparison with only white LED illumination (W*). On the other hand, the use of blue (B) and red (R) LED illumination results in a half-fold increase in plant yield. Understanding the effects of LED illumination spectrum on the growth of plant sweet basil plants through basic horticulture research enables farmers to significantly improve their production yield, thus food security and profitability.

scholarly journals Plant buffering against the high-light stress-induced accumulation of CsGA2ox8 transcripts via alternative splicing to finely tune gibberellin levels and maintain hypocotyl elongation

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Bin Liu ◽  
Shuo Zhao ◽  
Pengli Li ◽  
Yilu Yin ◽  
Qingliang Niu ◽  
...  
Keyword(s):  
Alternative Splicing ◽  
Light Intensity ◽  
Intron Retention ◽  
Light Stress ◽  
Photosynthetic Photon Flux Density ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Rna Seq ◽  
Multiple Transcripts ◽  
Novel Transcript

AbstractIn plants, alternative splicing (AS) is markedly induced in response to environmental stresses, but it is unclear why plants generate multiple transcripts under stress conditions. In this study, RNA-seq was performed to identify AS events in cucumber seedlings grown under different light intensities. We identified a novel transcript of the gibberellin (GA)-deactivating enzyme Gibberellin 2-beta-dioxygenase 8 (CsGA2ox8). Compared with canonical CsGA2ox8.1, the CsGA2ox8.2 isoform presented intron retention between the second and third exons. Functional analysis proved that the transcript of CsGA2ox8.1 but not CsGA2ox8.2 played a role in the deactivation of bioactive GAs. Moreover, expression analysis demonstrated that both transcripts were upregulated by increased light intensity, but the expression level of CsGA2ox8.1 increased slowly when the light intensity was >400 µmol·m−2·s−1 PPFD (photosynthetic photon flux density), while the CsGA2ox8.2 transcript levels increased rapidly when the light intensity was >200 µmol·m−2·s−1 PPFD. Our findings provide evidence that plants might finely tune their GA levels by buffering against the normal transcripts of CsGA2ox8 through AS.

Sign in / Sign up

Export Citation Format

Share Document