Midday Conditions Research Articles

Application of Photovoltaic Panels as Producers of Electrical Energy With IoT Technology Based on Programmable Logic Controller

The process of converting solar cell electrical energy is a form of utilizing environmentally friendly alternative energy sources (renewable energy). The conversion system is in the form of PV panels that are installed in a location exposed to sunlight and unobstructed. Monitoring is carried out when the sun shines from morning to evening. The location of the panel is in the vehicle parking lot of the engineering faculty, while monitoring is carried out in the Control Laboratory of the Tanjungpura University Engineering Faculty, which is 300 meters away. Factors that determine the quality of PV panels are the system and dimensions. This shows that fluctuations in current (I), voltage (V) and power (P) need to be controlled so that load distribution and reserves can prevent reduced energy generation. Observation and control using Long Range Area (LoRa) radio transmission media connections, Internet of Things (IoT) and Programmable Logical Control (PLC) in real-time. Observation and test results show that energy generation has experienced an increase in temperature which has an impact on reducing power. Meanwhile, the effect of the distance between the installed panels produces an average delay of 7 milliseconds (midday conditions). Meanwhile, the Signal to Noise Ratio (SNR) value for data transmission is 30 dBm at the device frequency of 868.125 MHz. Baud rate 2400-9600 bps with a speed of 0.3 bps – 62.5 Kbps. The application of this system is a research novelty because it can determine and control the generation of electrical energy at minimum, maximum and optimum conditions with a certain distance between the observer and the installed panel.

Environmental light induce deletion-dependent RNA editing in the mitochondrial atp6 gene of Calotropis procera

Evidence substantiates a correlation between RNA editing and cellular stress in plants, particularly within organelles such as mitochondria responsible for electron transport. The mitochondrial atp6 (mt-atp6) gene, which is renowned for playing a crucial role in ATP synthase activity, encodes the a-subunit of ATP synthase. We conducted a comprehensive analysis encompassing three distinct environmental conditions (dawn, midday, and pre-dusk): pre- and post-irrigation intervals, assessing cDNAs derived from the mt-atp6 gene (accession no. OQ673859) in the arid plant species Calotropis procera. Reconstructed atp6 cDNAs corresponding to dawn (accession no. OQ673860), midday (accession no. OQ673861), and pre-dusk (accession no. OQ673862) were generated from RNA-seq data. Conversely, cDNA assemblies’ post-irrigation yielded iD (accession no. OQ673863), iM (accession no. OQ673864), and iPD (accession no. OQ673865) transcripts. Furthermore, Atp6 DNA sequences were reconstituted utilizing the MT-atp6 gene from Hoya lithophytica (accession no. MW71905). Our research showed that the mt-atp6 gene of Calotropis procera has 19 editing sites. Eleven of these sites stayed the same in all of the conditions we tested them in. Finding fragment deletions was an interesting discovery. This was a new phenomenon that was seen in all conditions except for the pre-dusk (PD) and post-irrigation pre-dusk (iPD) datasets. It was discovered that deletions that depend on editing RNA had a big effect on the secondary and tertiary structures of the ATP synthase alpha-subunit, which in turn had an effect on the accumulation of ATP. Among these sites, three were specific to the dawn and midday conditions before (D, M) and after irrigation (iD, iM), three were specific to the pre-dusk conditions before (PD) and after irrigation (iPD), and two sites were exclusive to the post-irrigation pre-dusk (iPD) dataset.

A data-intensive documentation of plant ecosystem thermoregulation across spatial and temporal scales.

This article is a Commentary on Guo et al. (2023), 238: 1004–1018.

Intrinsic Photosensitivity of the Vulnerable Seagrass Phyllospadix iwatensis: Photosystem II Oxygen-Evolving Complex Is Prone to Photoinactivation.

Phyllospadix iwatensis, a foundation species of the angiosperm-dominated marine blue carbon ecosystems, has been recognized to be a vulnerable seagrass. Its degradation has previously been reported to be associated with environmental changes and human activities, while there has been a limited number of studies on its inherent characteristics. In this study, both the physiological and molecular biological data indicated that the oxygen-evolving complex (OEC) of P. iwatensis is prone to photoinactivation, which exhibits the light-dependent trait. When exposed to laboratory light intensities similar to typical midday conditions, <10% of the OEC was photoinactivated, and the remaining active OEC was sufficient to maintain normal photosynthetic activity. Moreover, the photoinactivated OEC could fully recover within the same day. However, under harsh light conditions, e.g., light intensities that simulate cloudless sunny neap tide days and continual sunny days, the OEC suffered irreversible photoinactivation, which subsequently resulted in damage to the photosystem II reaction centers and a reduction in the rate of O2 evolution. Furthermore, in situ measurements on a cloudless sunny neap tide day revealed both poor resilience and irreversible photoinactivation of the OEC. Based on these findings, we postulated that the OEC dysfunction induced by ambient harsh light conditions could be an important inherent reason for the degradation of P. iwatensis.

Ecosystem Photosynthesis in Land‐Surface Models: A First‐Principles Approach Incorporating Acclimation

AbstractVegetation regulates land‐atmosphere, water, and energy exchanges and is an essential component of land‐surface models (LSMs). However, LSMs have been handicapped by assumptions that equate acclimated photosynthetic responses to the environment with the fast responses observable in the laboratory. The effects of acclimation can be taken into account by including PFT‐specific values of photosynthetic parameters, but at the cost of increasing parameter requirements. Here, we develop an alternative approach for including acclimation in LSMs by adopting the P model, an existing light‐use efficiency model for gross primary production (GPP) that implicitly predicts the acclimation of photosynthetic parameters on a weekly to monthly timescale via optimality principles. We demonstrate that it is possible to explicitly separate the fast and slow photosynthetic responses to environmental conditions, allowing the simulation of GPP at the sub‐daily timesteps required for coupling in an LSM. The resulting model reproduces the diurnal cycles of GPP recorded by eddy‐covariance flux towers in a temperate grassland and boreal, temperate and tropical forests. The best performance is achieved when biochemical capacities are adjusted to match recent midday conditions. Comparison between this model and the operational LSM in the European Centre for Medium‐range Weather Forecasts climate model shows that the new model has better predictive power in most of the sites and years analyzed, particularly in summer and autumn. Our analyses suggest a simple and parameter‐sparse method to include both instantaneous and acclimated responses within an LSM framework, with potential applications in weather, climate, and carbon‐cycle modeling.

Does Organization in Turbulence Influence Ozone Removal by Deciduous Forests?

AbstractDry deposition is an important sink of tropospheric ozone and influences background and episodic ozone air pollution. Plant canopies remove ozone through uptake by plant stomata, leaf cuticles, and soil. Stomatal uptake of ozone injures vegetation, thereby altering local‐to‐global water and carbon cycling. Observed ozone fluxes are used to inform dry deposition parameterizations in chemical transport models but represent the net influence of several poorly constrained processes. Advancing understanding of the processes controlling dry deposition is key for building predictive ability of the terrestrial ozone sink and plant damage. Here, we constrain the influence of spatial structure in turbulence on ozone dry deposition with large eddy simulation coupled to a multilayer canopy model. We investigate whether organized turbulence separates areas of efficient leaf uptake from areas of high or low ozone mixing ratios. We simulate summertime midday conditions at three homogenous deciduous forests with varying leaf area, soil moisture, and ambient humidity. Sensitivity simulations perturb atmospheric stability, parameters related to ozone dry deposition, how quickly stomata respond to local atmospheric variations, and entrainment of ozone from atmospheric boundary layer growth. Overall, we find a low covariance between ozone and leaf uptake, in part due to counteracting influences from micrometeorological variations on ozone and leaf uptake individually versus the influence of leaf uptake on ozone. The low covariance between ozone and leaf uptake suggests that dry deposition parameterizations and interpretations of ozone flux observations can ignore the influence of organized turbulence on dry deposition.

Model of the Ionospheric Trough for Daytime Winter Conditions Based on Data from Interkosmos-19 and Champ Satellites

The principles and algorithm for the construction of an empirical model of the ionospheric trough for quiet (Kр = 2) daytime (06−18 LT) winter conditions in the Northern and Southern Hemispheres are described. The model consists of models of the trough position and shape. The model of the trough position describes longitudinal variations of the trough position in terms of the geographic latitude for fixed moments of local time. The model of the trough shape describes the latitudinal–longitudinal variations of foF2 within the interval of geographic latitudes 40°−85° in both hemispheres. The model of the ionospheric trough is probabilistic, since the trough is not always observed under midday conditions. In other words, the problem consists of the construction of a model of foF2 in the daytime, high-latitude ionosphere that would describe the trough structure. Data from the Interkosmos-19 and CHAMP satellites were used to solve this problem. The IRI international model of the ionosphere was also widely used; however, according to the tests, the constructed model more adequately describes the diurnal, longitudinal, and latitudinal variations of foF2 than IRI-2016. This model, together with the previously constructed model of the nighttime trough, makes it possible to speak of the creation of a complete model of foF2 in the winter ionosphere. Soon, the complete foF2 model will be accessible at the IZMIRAN site http://www.izmiran.ru/ionosphere/sm-mit/ . The model make it possible to calculate the longitudinal variations of the trough position and the latitudinal–longitudinal variations of foF2 for any local time and any level of solar activity within the range F10.7 = 70−200 for all winter months.

Microwave and Meteorological Fusion: A method of Spatial Downscaling of Remotely Sensed Soil Moisture

Downscaling of microwave remotely sensed that soil moisture content (SMC) is an efficient way to obtain spatial continuous SMC at a finer resolution. However, the classical optical/thermal and microwave fusion, and the active and passive microwave fusion cannot work under all-weather conditions because of contamination of clouds or the lack of suitable radar data source. In this study, a microwave and meteorological fusion (MMF) is provided. The MMF method is based on a complementary relationship hypothesis assuming SMC is reflected in the adjacent surface atmospheric moisture under midday conditions. By this method, daily passive SMC products from Soil Moisture Active Passive (SMAP) mission with 36-km resolution were disaggregated using a daily gridded meteorological data with nominal 4-km resolution. The original and downscaled SMCs were evaluated by comparing with in situ SMC obtained from three core validation sites and three sparse networks. The experiment was conducted in the central part of the U.S. from April 2015 to June 2018. Results demonstrated that the downscaled SMC maintained the dynamic range of original SMC product and energy was conserved. Furthermore, the downscaled SMC showed good agreement with and slightly outperformed the original SMC as compared with in situ SMC. The downscaling method is shown to capture higher resolution SMC spatial variability while preserving the quality of original SMC. However, because of the complexity of soil moisture-atmosphere interactions, the actual contributing domain of downscaled SMC may be greater than 4 km. The MMF method is suggested as a supplementary for all-weather downscaling coarse-resolution SMC.

Mars Initial Reference Ionosphere (MIRI) Model: Updates and Validations Using MAVEN, MEX, and MRO Data Sets

AbstractThe Mars Initial Reference Ionosphere (MIRI) model is a semiempirical formulation designed to provide climatological estimates of key parameters of the Martian ionosphere. For the new MIRI‐2018 version, an expanded database is used from the Mars Express/Mars Advanced Radar for Subsurface and Ionosphere Sounding/Active Ionospheric Sounding (MEX/MARSIS/AIS) instrument, consisting of 215,818 values of maximum electron density of the M2‐layer (NmM2) from the years 2005–2015. These data are organized by photochemical‐equilibrium equations to obtain a functional dependence of NmM2 upon solar drivers (flux and solar zenith angle). The resulting peak density is used to calibrate normalized electron density profiles [Ne (h)] derived from theory and an empirical model. The MIRI‐2018 thus provides estimates of NmM2, Ne (h), and total electron content (TEC) for any date past or future. Validation using Mars Atmosphere and Volatile EvolutioN (MAVEN)'s new radio occultation science experiment (ROSE) was successful for NmM2 values, but MIRI was found to overestimate TEC values. The validation failure for TEC was traced to overestimates of plasma at low altitudes (M1 layer). A separate module for TEC was derived using 126,055 values from the Mars Reconnaissance Orbiter/SHAllow RADar (MRO/SHARAD) TEC database from 2006 to 2014. Validation of this new TEC module with ROSE data was successful. Future improvements to MIRI‐2018 require new ways to characterize the bottomside ionosphere's contribution to the TEC integral for midday (low solar zenith angle) conditions. This requires new simulation studies of secondary ionization rates by photoelectrons produced via the primary X‐ray ionization process for the M1 layer.

The effects of light intensity on the growth of Japanese Gambierdiscus spp. (Dinophyceae)

Marine toxic dinoflagellates of the genus Gambierdiscus are the causative agents of ciguatera fish poisoning (CFP), a form of seafood poisoning that is widespread in tropical, subtropical and temperate regions worldwide. The distributions of Gambierdiscus australes, Gambierdiscus scabrosus and two phylotypes of Gambierdiscus spp. type 2 and type 3 have been reported for the waters surrounding the main island of Japan. To explore the bloom dynamics and the vertical distribution of these Japanese species and phylotypes of Gambierdiscus, the effects of light intensity on their growth were tested, using a photoirradiation-culture system. The relationship between the observed growth rates and light intensity conditions for the four species/phylotypes were formulated at R>0.92 (p<0.01) using regression analysis and photosynthesis-light intensity (P-L) model. Based on this equation, the optimum light intensity (Lmax) and the semi-optimum light intensity range (Ls-opt) that resulted in the maximum growth rate (μmax) and ≥80% μmax values of the four species/phylotypes, respectively, were as follows: (1) the Lmax and Ls-opt of G. australes were 208μmol photons m−2s−1 and 91–422μmol photons m−2s−1, respectively; (2) those of G. scabrosus were 252 and 120–421μmol photons m−2s−1, respectively; (3) those of Gambierdiscus sp. type 2 were 192 and 75–430μmol photons m−2s−1, respectively; and (4) those of Gambierdiscus sp. type 3 were ≥427 and 73–427μmol photons m−2s−1, respectively. All four Gambierdiscus species/phylotypes required approximately 10μmol photons m−2s−1 to maintain growth. The light intensities in coastal waters at a site in Tosa Bay were measured vertically at 1m intervals once per season. The relationships between the observed light intensity and depth were formulated using Beer’s Law. Based on these equations, the range of the attenuation coefficients at Tosa Bay site was determined to be 0.058–0.119m−1. The values 1700μmol photons m−2s−1, 500μmol photons m−2s−1, and 200μmol photons m−2s−1 were substituted into the equations to estimate the vertical profiles of light intensity at sunny midday, cloudy midday and rainy midday, respectively. Based on the regression equations coupled with the empirically determined attenuation coefficients for each of the four seasons, the ranges of the projected depths of Lmax and Ls-opt for the four Gambierdiscus species/phylotypes under sunny midday conditions, cloudy midday conditions, and rainy midday conditions were 12–38m and 12–54m, 1–16m and 1–33m, and 0m and 0–16m, respectively. These results suggest that light intensity plays an important role in the bloom dynamics and vertical distribution of Gambierdiscus species/phylotypes in Japanese coastal waters.

The lifetime of nitrogen oxides in an isoprene-dominated forest

Abstract. The lifetime of nitrogen oxides (NOx) affects the concentration and distribution of NOx and the spatial patterns of nitrogen deposition. Despite its importance, the lifetime of NOx is poorly constrained in rural and remote continental regions. We use measurements from a site in central Alabama during the Southern Oxidant and Aerosol Study (SOAS) in summer 2013 to provide new insights into the chemistry of NOx and NOx reservoirs. We find that the lifetime of NOx during the daytime is controlled primarily by the production and loss of alkyl and multifunctional nitrates (ΣANs). During SOAS, ΣAN production was rapid, averaging 90 ppt h−1 during the day, and occurred predominantly during isoprene oxidation. Analysis of the ΣAN and HNO3 budgets indicate that ΣANs have an average lifetime of under 2 h, and that approximately 45 % of the ΣANs produced at this site are rapidly hydrolyzed to produce nitric acid. We find that ΣAN hydrolysis is the largest source of HNO3 and the primary pathway to permanent removal of NOx from the boundary layer in this location. Using these new constraints on the fate of ΣANs, we find that the NOx lifetime is 11 ± 5 h under typical midday conditions. The lifetime is extended by storage of NOx in temporary reservoirs, including acyl peroxy nitrates and ΣANs.

MAVEN and the Mars Initial Reference Ionosphere model

AbstractThe Neutral Gas and Ion Mass Spectrometer (NGIMS) on the Mars Atmosphere and Volatile EvolutioN (MAVEN) satellite measured the distribution of thermal ions (2–150 amu) at ionospheric heights (~130–400 km) under midday conditions during the “Deep‐Dip” orbit campaign from 17 to 22 April 2015. Assuming charge neutrality, we use the sum of NGIMS ions as a proxy for electron density (Ne) and compare results with a new version of the Mars Initial Reference Ionosphere (MIRI) developed for this study. At altitudes where the transition between photochemical and dynamical processes occurs (130–200 km), the NGIMS results agree with the shape of the MIRI‐predicted Ne(h) profiles, but the model predictions are a factor of 2 higher. Above 200 km, the NGIMS gradients of total ions versus height diverge even more from MIRI's Ne(h) predictions for reasons that may involve crustal‐B field effects, ionopause‐like boundaries, and horizontal plasma transport away from the noon sector—factors not yet included in MIRI.

A Buffelgrass Aerial Spraying Pilot Project: Spray Application and Deposition

<abstract> <sc><bold>Abstract.</bold> </sc>A pilot project was conducted to evaluate the feasibility of aerially spraying buffelgrass (Cenchrus ciliaris) with glyphosate in the Sonoran Desert of Arizona. Buffelgrass is an invasive grass that is spreading rapidly and has catastrophic ecological impacts. Spraying was conducted using a helicopter and extremely coarse drops. Blue dye was used as a deposition tracer. This work indicates that it is possible to aerially spray buffelgrass in this setting though it is difficult to get herbicide to deposit in hot, dry, unstable, midday conditions. The extremely complex, broken terrain and the small spray blocks targeted in this project are a challenge to precision application.

The potential near-source ozone impacts of upstream oil and gas industry emissions

Increased drilling in urban areas overlying shale formations and its potential impact on human health through decreased air quality make it important to estimate the contribution of oil and gas activities to photochemical smog. Flares and compressor engines used in natural gas operations, for example, are large sources not only of NOx but also of formaldehyde, a hazardous air pollutant and powerful ozone precursor. We used a neighborhood scale (200 m horizontal resolution) three-dimensional (3D) air dispersion model with an appropriate chemical mechanism to simulate ozone formation in the vicinity of a hypothetical natural gas processing facility, based on accepted estimates of both regular and nonroutine emissions. The model predicts that, under average midday conditions in June, regular emissions mostly associated with compressor engines may increase ambient ozone in the Barnett Shale by more than 3 ppb beginning at about 2 km downwind of the facility, assuming there are no other major sources of ozone precursors. Flare volumes of 100,000 cubic meters per hour of natural gas over a period of 2 hr can also add over 3 ppb to peak 1-hr ozone somewhat further (>8 km) downwind, once dilution overcomes ozone titration and inhibition by large flare emissions of NOx. The additional peak ozone from the hypothetical flare can briefly exceed 10 ppb about 16 km downwind. The enhancements of ambient ozone predicted by the model are significant, given that ozone control strategy widths are of the order of a few parts per billion. Degrading the horizontal resolution of the model to 1 km spuriously enhances the simulated ozone increases by reducing the effectiveness of ozone inhibition and titration due to artificial plume dilution. Implications: Major metropolitan areas in or near shale formations will be hard pressed to demonstrate future attainment of the federal ozone standard, unless significant controls are placed on emissions from increased oil and gas exploration and production. The results presented here show the importance of improving the temporal and spatial resolution of both emission inventories and air quality models used in ozone attainment demonstrations for areas with significant oil and gas activities. Supplemental Materials: Supplemental materials are available for this article. Go to the publisher's online edition of the Journal of the Air & Waste Management Association for further technical details on the HARC model chemical mechanism and its performance evaluation.

Vertical mixing and the effects of solar radiation on photosystem II electron transport by phytoplankton in the Ross Sea Polynya

Detailed studies were made in the springtime Ross Sea Polynya of the interaction between near-surface mixing processes, inferred from Thorpe scales and acoustic backscatter, and the quantum efficiency and rate of PSII electron transport of phytoplankton photosynthesis measured at fine depth and time scales by active fluorometry. The phytoplankton assemblage was dominated by Phaeocystis antarctica. Surface conditions alternated between windy episodes producing Langmuir circulation (LC) or calm periods favoring internal waves, in both cases there was significant vertical transport of phytoplankton. During LC episodes, strong near-surface (<10m) vertical gradients in quantum efficiency and inhibition of electron transport were observed despite evidence of vigorous vertical exchange. Under sunny mid-day conditions, profiles of PSII electron transport had sub-surface peaks and electron transport at PAR irradiances >40μmolphotonsm−2s−1 was generally lower compared to early morning profiles on the same day. In time-series deployments, intrinsic quantum efficiency (Fv′/Fm′) was relatively constant under calm conditions at 12m, but highly variable at 6m under LC conditions. Simultaneously measured time-series of acoustic backscatter and Fv′/Fm′ during LC conditions were negatively correlated, i.e. high backscatter arising from the downward advection of surface originating microbubbles coincided with low intrinsic efficiency. Transport also occurred in connection with finer-scale features, possibly arising from breaking surface waves. These results show that LC in the Ross Sea Polynya, in combination with changes in quenching driven by near surface UVR and PAR exposure, reduce photosynthetic electron transport over much of the upper mixed layer. Further observations and modeling will be needed to establish the extent to which this decreases water column productivity.

Correction to: ‘Structure and dynamics of the convective boundary layer on Mars as inferred from large‐eddy simulations and remote‐sensing measurements’

The structure of the Martian convective boundary layer (BL) is decribed by means of a novel approach involving both modelling and data analysis. Mars Express radio-occultation (RO) temperature profiles are compared to large-eddy simulations (LESs) performed with the Martian mesoscale model. The model combines the Martian radiative transfer, soil and surface layer schemes designed at Laboratoire de Meteorologie Dynamique (LMD) with the most recent version of the Weather Research and Forecast (WRF) fully compressible non-hydrostatic dynamical core. The key roles of the vertical resolution and, to lesser extent, of the domain horizontal extent have been investigated to ensure the robustness of the LES results. The dramatic regional variations of the BL depth are quantitatively reproduced by the Martian LES. Intense BL dynamics are found to underlie the measured depths (up to 9 km): vertical speed up to 20 m s−1, heat flux up to 2.7 K m s−1 and turbulent kinetic energy up to 26 m2 s−2. Under specific conditions, both the model and the measurements show a distinctive positive correlation between surface topography and BL depth. Our interpretation is that, in the tenuous CO2 Martian near-surface environment, the daytime BL is to first order controlled by the infrared radiative heating, fairly independent of elevation, which implies a simple correlation between the BL potential temperature and the inverse pressure (‘pressure effect’). No prominent ‘pressure effect’ is in action on Earth where sensible heat flux dominates the BL energy budget. Both RO observations and numerical simulations confirm the terrain-following behaviour of near-surface temperature on Mars induced by the dominant radiative influence. The contribution of the Martian sensible heat flux is not negligible and results in a given isotherm in the BL being comparatively closer to the ground at higher surface elevation. The strong radiative control of the Martian convective BL implies a generalised formulation for the BL dimensionless quantities. Based on this formulation and the variety of simulated BL depths by the LES, new similarity relationships for the Martian convective BL in quasi-steady midday conditions are derived. Rigorous comparisons between the Martian and terrestrial BL and fast computations of the mean Martian BL turbulent statistics are now made possible by such similarity laws. Copyright © 2010 Royal Meteorological Society

Structure and dynamics of the convective boundary layer on Mars as inferred from large‐eddy simulations and remote‐sensing measurements

AbstractThe structure of the Martian convective boundary layer (BL) is decribed by means of a novel approach involving both modelling and data analysis. Mars Express radio‐occultation (RO) temperature profiles are compared to large‐eddy simulations (LESs) performed with the Martian mesoscale model. The model combines the Martian radiative transfer, soil and surface layer schemes designed at Laboratoire de Météorologie Dynamique (LMD) with the most recent version of the Weather Research and Forecast (WRF) fully compressible non‐hydrostatic dynamical core. The key roles of the vertical resolution and, to lesser extent, of the domain horizontal extent have been investigated to ensure the robustness of the LES results. The dramatic regional variations of the BL depth are quantitatively reproduced by the Martian LES. Intense BL dynamics are found to underlie the measured depths (up to 9 km): vertical speed up to 20 m s−1, heat flux up to 2.7 K m s−1 and turbulent kinetic energy up to 26 m2 s−2. Under specific conditions, both the model and the measurements show a distinctive positive correlation between surface topography and BL depth. Our interpretation is that, in the tenuous CO2 Martian near‐surface environment, the daytime BL is to first order controlled by the infrared radiative heating, fairly independent of elevation, which implies a simple correlation between the BL potential temperature and the inverse pressure (‘pressure effect’). No prominent ‘pressure effect’ is in action on Earth where sensible heat flux dominates the BL energy budget. Both RO observations and numerical simulations confirm the terrain‐following behaviour of near‐surface temperature on Mars induced by the dominant radiative influence. The contribution of the Martian sensible heat flux is not negligible and results in a given isotherm in the BL being comparatively closer to the ground at higher surface elevation. The strong radiative control of the Martian convective BL implies a generalised formulation for the BL dimensionless quantities. Based on this formulation and the variety of simulated BL depths by the LES, new similarity relationships for the Martian convective BL in quasi‐steady midday conditions are derived. Rigorous comparisons between the Martian and terrestrial BL and fast computations of the mean Martian BL turbulent statistics are now made possible by such similarity laws. Copyright © 2010 Royal Meteorological Society

Proposed form for the atmospheric turbulence spatial spectrum at large scales

The performance of large optical systems can be strongly influenced by the behavior of large-scale atmospheric turbulence. Previous optical phase difference data diverged from theoretical predictions based on von Kármán's model. To establish a better model microthermal data over large spatial scales were collected at two sites with few terrain inhomogeneities, in unstable midday conditions. Spatial structure function and spectra are developed. A model spatial spectrum is fit to the data with parameters to set two power law dependencies and the transition rate between them. By working with spatial spectral data the assumption of frozen flow is avoided. The optimum spatial spectrum is Kolmogorov-like in the inertial range. Temporal spectral data compare favorably with the new model, which better describes the transition of turbulence scaling from small scales to large.

Photosynthetic characteristics of Spirulina platensis grown in commercial-scale open outdoor raceway ponds: what do the organisms tell us?

At least six important factors that determine productivity in mass algal cultures have been identified. These are (1) the culture depth or optical cross section, (2) turbulence, (3) nutrient content and supply, (4) cultivation procedure, (5) biomass concentration and areal density, and (6) photo-acclimation. Since the efficient capturing of light energy relates to high productivities and efficiencies, all potential losses and inefficiencies need to be managed and eliminated. Photoinhibition could reduce areal productivities by up to 30% and more, where photoinhibition is the decline in photosynthetic rates at supra-optimal irradiancies. It is, however, unclear whether this occurs in high density and turbulent mass algal cultures. Using chlorophyll a fluorescence, it was possible to show how the maximum quantum efficiency of dark adapted cells (Φmax) decreased at midday conditions of high irradiancies. Neither photochemical (qP) nor, to a lesser extent, non-photochemical quenching (qN), could explain the midday depression. Using chlorophyll a fluorescence transient analyses it was shown that, although light absorption increased towards midday, the captured energy was essentially lost as heat dissipation. This was clearly shown in low-density cultures where the average light per cell was high, compared to denser cultures where the effects of high light exposure were significantly reduced. In low-density cultures, more than 60% of the reaction centres (RCs) became “silent”, meaning that they neither reduce QA, nor return their excitation energy to the antenna. At higher cell densities, losses due to photoinhibition and the number of “silent RCs” were much reduced. Elucidation of the relationship between active RCs and productivity should be a priority for optimising photobioreactor productivity.

Water Stress Detection in a Greenhouse by a Step Change of Ventilation

Water stress of a greenhouse crop results in a lower-than-normal transpiration and photosynthesis rates, which affects the humidity and CO 2 concentration of the greenhouse air. This change may be detected and used for stress diagnosis if the signal-to-noise ratio is sufficiently large. Under midday conditions, when water stress is likely to occur, the greenhouse is often ventilated, resulting in a rather small signal-to-noise ratio. It is suggested here that the signal level may be increased by exciting the system, namely by suspending the ventilation for a short period of time. The transient response of temperature, humidity and CO 2 concentration to the abrupt change of ventilation may be monitored, analysed and compared to a modelled normal response for the same greenhouse with an unstressed crop. A significant discrepancy between the two would indicate that the crop is stressed. Lawn, serving as a crop substitute, has been submitted to several irrigation–drought sequences in a small experimental greenhouse. Each day, in the early afternoon, ventilation was suspended for three periods of 30 min each. Differences in the response of CO 2 concentration enabled the detection of all stress periods as soon as the rate of transpiration decreased to below normal. The humidity response was slightly less sensitive, and the temperature response was the least sensitive. Water-stress detection via the excitation method was considerably better than detection based on observations at full ventilation.