scholarly journals Spatially and temporally resolved measurements of NO<sub><i>x</i></sub> fluxes by airborne eddy covariance over Greater London

2021 ◽  
Vol 21 (19) ◽  
pp. 15283-15298
Author(s):  
Adam R. Vaughan ◽  
James D. Lee ◽  
Stefan Metzger ◽  
David Durden ◽  
Alastair C. Lewis ◽  
...  
Keyword(s):  
Eddy Covariance ◽  
Time Of Day ◽  
Environmental Drivers ◽  
Environmental Response ◽  
City Region ◽  
Diurnal Variability ◽  
Airborne Measurements ◽  
Measured Flux ◽  
Spatial Coverage ◽  
Early Afternoon

Abstract. Flux measurements of nitrogen oxides (NOx) were made over London using airborne eddy covariance from a low-flying aircraft. Seven low-altitude flights were conducted over Greater London, performing multiple overpasses across the city during eight days in July 2014. NOx fluxes across the Greater London region (GLR) exhibited high heterogeneity and strong diurnal variability, with central areas responsible for the highest emission rates (20–30 mg m−2 h−1). Other high-emission areas included the M25 orbital motorway. The complexity of London's emission characteristics makes it challenging to pinpoint single emissions sources definitively using airborne measurements. Multiple sources, including road transport and residential, commercial and industrial combustion sources, are all likely to contribute to measured fluxes. Measured flux estimates were compared to scaled National Atmospheric Emissions Inventory (NAEI) estimates, accounting for monthly, daily and hourly variability. Significant differences were found between the flux-driven emissions and the NAEI estimates across Greater London, with measured values up to 2 times higher in Central London than those predicted by the inventory. To overcome the limitations of using the national inventory to contextualise measured fluxes, we used physics-guided flux data fusion to train environmental response functions (ERFs) between measured flux and environmental drivers (meteorological and surface). The aim was to generate time-of-day emission surfaces using calculated ERF relationships for the entire GLR; 98 % spatial coverage was achieved across the GLR at 400 m2 spatial resolution. All flight leg projections showed substantial heterogeneity across the domain, with high emissions emanating from Central London and major road infrastructure. The diurnal emission structure of the GLR was also investigated, through ERF, with the morning rush hour distinguished from lower emissions during the early afternoon. Overall, the integration of airborne fluxes with an ERF-driven strategy enabled the first independent generation of surface NOx emissions, at high resolution using an eddy-covariance approach, for an entire city region.

scholarly journals Spatially and temporally resolved measurements of NO<sub>x</sub> fluxes by airborne eddy-covariance over Greater London

2021 ◽  
Author(s):  
Adam R. Vaughan ◽  
James D. Lee ◽  
Stefan Metzger ◽  
David Durden ◽  
Alastair C. Lewis ◽  
...  
Keyword(s):  
Eddy Covariance ◽  
Time Of Day ◽  
Environmental Drivers ◽  
Environmental Response ◽  
City Region ◽  
Diurnal Variability ◽  
Airborne Measurements ◽  
Measured Flux ◽  
Spatial Coverage ◽  
Early Afternoon

Abstract. Flux measurements of nitrogen oxides (NOx) were made over London using airborne eddy-covariance from a low flying aircraft. Seven low altitude flights were conducted over Greater London performing multiple over-passes across the city during eight days in July 2014. NOx fluxes across the Greater London region exhibited high heterogeneity and strong diurnal variability, with central areas responsible for the highest emission rates (20–30 mg m−2 h−1). Other high emission areas included the M25 orbital motorway. The complexity of London’s emission characteristics makes it challenging to pinpoint single emission sources definitively using airborne measurements. Multiple sources, including road transport and residential, commercial and industrial combustion sources are all likely to contribute to measured fluxes. Measured flux estimates were compared to scaled National Atmospheric Emissions Inventory (NAEI) estimates, accounting for; monthly, daily and hourly variability. Significant differences were found between the flux-driven emissions and the NAEI estimates across Greater London, with measured values up to two times higher in Central London than those predicted by the inventory. To overcome the limitations of using the national inventory to contextualise measured fluxes, we used physics-guided flux data fusion to train environmental response functions (ERF) between measured flux and environmental drivers (meteorological and surface). The aim was to generate time-of-day emission surfaces using calculated ERF relationships for the entire Greater London region (GLR). 98 % spatial coverage was achieved across GLR at 400 m2 spatial resolution. All flight leg projections showed substantial heterogeneity across the domain, with high emissions emanating from Central London and major road infrastructure. The diurnal emission structure of the GLR was also investigated, through ERF, with the morning rush-hour distinguished from lower emissions during the early afternoon. Overall, the integration of airborne fluxes with an ERF-driven strategy enabled the first independent generation of surface NOx emissions, at high resolution using an eddy-covariance approach, for an entire city region.

scholarly journals Identifying Diurnal Variability of Brain Connectivity Patterns Using Graph Theory

2021 ◽  
Vol 11 (1) ◽  
pp. 111
Author(s):  
Farzad V. Farahani ◽  
Magdalena Fafrowicz ◽  
Waldemar Karwowski ◽  
Bartosz Bohaterewicz ◽  
Anna Maria Sobczak ◽  
...  
Keyword(s):  
Resting State ◽  
Network Architecture ◽  
Inferior Frontal Gyrus ◽  
Brain Network ◽  
Time Of Day ◽  
Precentral Gyrus ◽  
Network Organization ◽  
Diurnal Variability ◽  
Sleep Inertia ◽  
Brain Functions

Significant differences exist in human brain functions affected by time of day and by people’s diurnal preferences (chronotypes) that are rarely considered in brain studies. In the current study, using network neuroscience and resting-state functional MRI (rs-fMRI) data, we examined the effect of both time of day and the individual’s chronotype on whole-brain network organization. In this regard, 62 participants (39 women; mean age: 23.97 ± 3.26 years; half morning- versus half evening-type) were scanned about 1 and 10 h after wake-up time for morning and evening sessions, respectively. We found evidence for a time-of-day effect on connectivity profiles but not for the effect of chronotype. Compared with the morning session, we found relatively higher small-worldness (an index that represents more efficient network organization) in the evening session, which suggests the dominance of sleep inertia over the circadian and homeostatic processes in the first hours after waking. Furthermore, local graph measures were changed, predominantly across the left hemisphere, in areas such as the precentral gyrus, putamen, inferior frontal gyrus (orbital part), inferior temporal gyrus, as well as the bilateral cerebellum. These findings show the variability of the functional neural network architecture during the day and improve our understanding of the role of time of day in resting-state functional networks.

scholarly journals Variability of Urinary Creatinine in Healthy Individuals

2021 ◽  
Vol 18 (6) ◽  
pp. 3166
Author(s):  
Gerd Sallsten ◽  
Lars Barregard
Keyword(s):  
Flow Rate ◽  
Excretion Rate ◽  
Time Of Day ◽  
Urinary Flow Rate ◽  
Urinary Flow ◽  
Diurnal Variability ◽  
Creatinine Excretion ◽  
Blood Samples ◽  
Urinary Creatinine ◽  
Creatinine Excretion Rate

Many urinary biomarkers are adjusted for dilution using creatinine or specific gravity. The aim was to evaluate the variability of creatinine excretion, in 24 h and spot samples, and to describe an openly available variability biobank. Urine and blood samples were collected from 60 healthy non-smoking adults, 29 men and 31 women. All urine was collected at six time points during two 24 h periods. Blood samples were also collected twice and stored frozen. Analyses of creatinine in urine was performed in fresh urine using an enzymatic method. For creatinine in urine, the intra-class correlation (ICC) was calculated for 24 h urine and spot samples. Diurnal variability was examined, as well as association with urinary flow rate. The creatinine excretion rate was lowest in overnight samples and relatively constant in the other five samples. The creatinine excretion rate in each individual was positively correlated with urinary flow rate. The creatinine concentration was highest in the overnight sample and at 09:30. For 24 h samples the ICC was 0.64, for overnight samples it was 0.5, and for all spot samples, it was much lower. The ICC for urinary creatinine depends on the time of day of sampling. Frozen samples from this variability biobank are open for researchers examining normal variability of their favorite biomarker(s).

Using deep learning to nowcast the spatial coverage of convection from Himawari-8 satellite data

2021 ◽  
Author(s):  
Ryan Lagerquist ◽  
Jebb Q. Stewart ◽  
Imme Ebert-Uphoff ◽  
Christina Kumler
Keyword(s):  
Deep Learning ◽  
Satellite Data ◽  
Geographic Location ◽  
Ground Truth ◽  
Atmospheric Science ◽  
Skill Score ◽  
Time Of Day ◽  
Lead Times ◽  
Weather Radars ◽  
Spatial Coverage

AbstractPredicting the timing and location of thunderstorms (“convection”) allows for preventive actions that can save both lives and property. We have applied U-nets, a deep-learning-based type of neural network, to forecast convection on a grid at lead times up to 120 minutes. The goal is to make skillful forecasts with only present and past satellite data as predictors. Specifically, predictors are multispectral brightness-temperature images from the Himawari-8 satellite, while targets (ground truth) are provided by weather radars in Taiwan. U-nets are becoming popular in atmospheric science due to their advantages for gridded prediction. Furthermore, we use three novel approaches to advance U-nets in atmospheric science. First, we compare three architectures – vanilla, temporal, and U-net++ – and find that vanilla U-nets are best for this task. Second, we train U-nets with the fractions skill score, which is spatially aware, as the loss function. Third, because we do not have adequate ground truth over the full Himawari-8 domain, we train the U-nets with small radar-centered patches, then apply trained U-nets to the full domain. Also, we find that the best predictions are given by U-nets trained with satellite data from multiple lag times, not only the present. We evaluate U-nets in detail – by time of day, month, and geographic location – and compare to persistence models. The U-nets outperform persistence at lead times ≥ 60 minutes, and at all lead times the U-nets provide a more realistic climatology than persistence. Our code is available publicly.

Intra- and inter-day variability in plasma tCO2 concentration in sedentary horses

2014 ◽  
Vol 10 (1) ◽  
pp. 39-47
Author(s):  
B.E. Bergstrom ◽  
J.H. Foreman ◽  
C.R. Foreman ◽  
A.M. Barger
Keyword(s):  
Blood Test ◽  
Indoor Environment ◽  
Early Morning ◽  
Time Of Day ◽  
Individual Variability ◽  
Strong Ion Difference ◽  
Serum Chemistry ◽  
Blood Samples ◽  
Early Afternoon ◽  
Glass Tubes

Sodium bicarbonate and other alkalinising solutions (‘milkshakes’) have been given to horses surreptitiously before exercise to provide exogenous buffering effects. After an initial positive blood test, some accused horse trainers claim that their horses ‘naturally test high’, so some jurisdictions allow a secured quarantine in which the horse is tested multiple times. The objective of this experiment was to determine the intra- and inter-day variability of plasma total CO2 (tCO2) and other plasma strong ions in a group of sedentary horses housed similarly to a quarantine period. The hypothesis was that plasma tCO2 would not remain constant over a multi-day monitoring interval, but would vary measurably during that interval. Eight sedentary (unconditioned) horses were studied for 2 weeks. Horses were acclimated to a climate-controlled indoor environment and an alfalfa-only diet for a minimum of 10 days prior to sampling. Horses were sampled 3 times daily for 5 consecutive days at 7:00, 11:00 and 15:00 h. Blood samples were collected directly into 10 ml heparinised evacuated glass tubes by jugular venipuncture using a double-ended 0.91 mm needle. Samples were chilled until concentrations of plasma tCO2, Na+, K+, and Cl-, were determined within 1-3 h of sampling using an automated serum chemistry analyzer which was calibrated daily using commercial reagents obtained from the manufacturer as well as externally-obtained NIST-traceable calibrating solutions. Mean results documented mild variations in mean plasma tCO2 (range 28.9-31.6 mmol/l), but individual horses’ plasma tCO2 ranged over 4-7 units. Results showed that there was considerable intra- and inter-individual variability in plasma tCO2. Mean pooled tCO2 and measured strong ion difference (SIDm) differed by time-of-day, with both late morning and early afternoon values lower than early morning values (P<0.001). There was a strong positive linear relationship between plasma SIDm and tCO2 (r=0.75, P<0.001).

Microhabitat use during brumation in the Japanese treefrog, Dryophytes japonicus

2018 ◽  
Vol 39 (2) ◽  
pp. 163-175 ◽  
Author(s):  
Amaël Borzée ◽  
Miyeon Kim ◽  
Jun Young Kim ◽  
Taeho Kim ◽  
Yikweon Jang
Keyword(s):  
Life Cycle ◽  
Time Of Day ◽  
Diel Cycle ◽  
Microhabitat Use ◽  
Behavioural Thermoregulation ◽  
Direction Finder ◽  
Early Afternoon

Abstract Although amphibians undergo drastic changes in physiology and behaviour before hibernation, this phase of their life cycle (i.e., brumation) is the least understood. We investigated the patterns of microhabitat use by Dryophytes japonicus during brumation using a Harmonic Direction Finder to track 27 adults in October 2013. Most frogs used chestnut trees throughout their diel cycle. The species was most active within the “leafy vegetation” microhabitat, moving about 2 m within 72 h on average, and mostly circa 10 AM. Frogs moved less in the four other microhabitats, with individuals moving between 1 m and 50 cm, typically during the early afternoon. Around 3 pm, the microhabitat mostly used was “on bark”, with displacements almost totally halted. The use of microhabitats and shelters, as well as movements in relation to time of day, suggests that D. japonicus displays behavioural thermoregulation during brumation. This research is the first providing insights in the brumation ecology of a non-freeze-resistant Palearctic anuran.

scholarly journals Eddy-covariance flux measurements with a weight-shift microlight aircraft

2012 ◽  
Vol 5 (7) ◽  
pp. 1699-1717 ◽  
Author(s):  
S. Metzger ◽  
W. Junkermann ◽  
M. Mauder ◽  
F. Beyrich ◽  
K. Butterbach-Bahl ◽  
...  
Keyword(s):  
Heat Flux ◽  
Eddy Covariance ◽  
Low Cost ◽  
Sensible Heat Flux ◽  
Flux Measurement ◽  
Wind Measurement ◽  
Airborne Measurements ◽  
Weight Shift ◽  
Flux Measurements

Abstract. The objective of this study is to assess the feasibility and quality of eddy-covariance flux measurements from a weight-shift microlight aircraft (WSMA). Firstly, we investigate the precision of the wind measurement (σu,v ≤ 0.09 m s−1, σw = 0.04 m s−1), the lynchpin of flux calculations from aircraft. From here, the smallest resolvable changes in friction velocity (0.02 m s−1), and sensible- (5 W m−2) and latent (3 W m−2) heat flux are estimated. Secondly, a seven-day flight campaign was performed near Lindenberg (Germany). Here we compare measurements of wind, temperature, humidity and respective fluxes between a tall tower and the WSMA. The maximum likelihood functional relationship (MLFR) between tower and WSMA measurements considers the random error in the data, and shows very good agreement of the scalar averages. The MLFRs for standard deviations (SDs, 2–34%) and fluxes (17–21%) indicate higher estimates of the airborne measurements compared to the tower. Considering the 99.5% confidence intervals, the observed differences are not significant, with exception of the temperature SD. The comparison with a large-aperture scintillometer reveals lower sensible heat flux estimates at both tower (−40 to −25%) and WSMA (−25–0%). We relate the observed differences to (i) inconsistencies in the temperature and wind measurement at the tower and (ii) the measurement platforms' differing abilities to capture contributions from non-propagating eddies. These findings encourage the use of WSMA as a low cost and highly versatile flux measurement platform.

scholarly journals A Comparison between the MODIS Product (MOD17A2) and a Tide-Robust Empirical GPP Model Evaluated in a Georgia Wetland

2018 ◽  
Vol 10 (11) ◽  
pp. 1831 ◽  
Author(s):  
Jianbin Tao ◽  
Deepak Mishra ◽  
David Cotten ◽  
Jessica O’Connell ◽  
Monique Leclerc ◽  
...  
Keyword(s):  
Eddy Covariance ◽  
Vegetation Index ◽  
Gross Primary Production ◽  
Training Data ◽  
Environmental Drivers ◽  
Canopy Reflectance ◽  
Co2 Fluxes ◽  
Moisture Index ◽  
Validation Data ◽  
Reflectance Data

Despite the importance of tidal ecosystems in the global carbon budget, the relationships between environmental drivers and carbon dynamics in these wetlands remain poorly understood. This limited understanding results from the challenges associated with in situ flux studies and their correlation with satellite imagery which can be affected by periodic tidal flooding. Carbon dioxide eddy covariance (EC) towers are installed in only a few wetlands worldwide, and the longest eddy-covariance record from Georgia (GA) wetlands contains only two continuous years of observations. The goals of the present study were to evaluate the performance of existing MODIS Gross Primary Production (GPP) products (MOD17A2) against EC derived GPP and develop a tide-robust Normalized Difference Moisture Index (NDMI) based model to predict GPP within a Spartina alterniflora salt marsh on Sapelo Island, GA. These EC tower-based observations represent a basis to associate CO2 fluxes with canopy reflectance and thus provide the means to use satellite-based reflectance data for broader scale investigations. We demonstrate that Light Use Efficiency (LUE)-based MOD17A2 does not accurately reflect tidal wetland GPP compared to a simple empirical vegetation index-based model where tidal influence was accounted for. The NDMI-based GPP model was capable of predicting changes in wetland CO2 fluxes and explained 46% of the variation in flux-estimated GPP within the training data, and a root mean square error of 6.96 g C m−2 in the validation data. Our investigation is the first to create a MODIS-based wetland GPP estimation procedure that demonstrates the importance of filtering tidal observations from satellite surface reflectance data.

EFFECT OF TIME OF DAY, A PARASITIC FUNGUS, AND A GENETIC MUTATION ON RATE OF PHOTOSYNTHESIS IN THE LOWBUSH BLUEBERRY

1966 ◽  
Vol 44 (5) ◽  
pp. 529-533 ◽  
Author(s):  
I. V. Hall ◽  
F. R. Forsyth ◽  
C. L. Lockhart ◽  
L. E. Aalders
Keyword(s):  
Early Morning ◽  
Genetic Mutation ◽  
Time Of Day ◽  
Parasitic Fungus ◽  
Mutant Type ◽  
Lowbush Blueberry ◽  
Early Afternoon ◽  
Rate Of Photosynthesis ◽  
Sugar Levels ◽  
Leaf Disks

The apparent rate of photosynthesis in the lowbush blueberry was measured, at four periods of the day, on leaf disks in Warburg flasks and with the use of Pardee's CO2 buffers. Significant differences were found in rates of O2 evolution at the four different periods. Oxygen evolution was greatest in the early morning when reducing sugars and starch levels were lowest. By early afternoon when starch and reducing sugar levels were much greater in the leaf disks the rate was the lowest.Leaf disks infected with Exobasidium vaccinii had a lower rate of apparent photosynthesis than normal leaves of the same clone. Disks cut from normal leaves of Vaccinium angustifolium had a higher rate of apparent photosynthesis than those of a variegated mutant. The leaves of the mutant were significantly smaller and seedlings of the mutant type grew more slowly than normal ones of the same cross. For these reasons lowbush blueberry plants of the mutant type or having the red-leaf disease are at a distinct disadvantage in nature.

scholarly journals At What Time of Day Do Daily Extreme Near-Surface Wind Speeds Occur?

2014 ◽  
Vol 27 (11) ◽  
pp. 4226-4244 ◽  
Author(s):  
Robert Fajber ◽  
Adam H. Monahan ◽  
William J. Merryfield
Keyword(s):  
Extreme Values ◽  
Mechanistic Model ◽  
Surface Wind ◽  
Time Of Day ◽  
Near Surface ◽  
Wind Speeds ◽  
Boundary Layer Processes ◽  
Early Afternoon ◽  
Extreme Wind ◽  
Extreme Wind Speeds

Abstract The timing of daily extreme wind speeds from 10 to 200 m is considered using 11 yr of 10-min averaged data from the 213-m tower at Cabauw, the Netherlands. This analysis is complicated by the tendency of autocorrelated time series to take their extreme values near the beginning or end of a fixed window in time, even when the series is stationary. It is demonstrated that a simple averaging procedure using different base times to define the day effectively suppresses this “edge effect” and enhances the intrinsic nonstationarity associated with diurnal variations in boundary layer processes. It is found that daily extreme wind speeds at 10 m are most likely in the early afternoon, whereas those at 200 m are most likely in between midnight and sunrise. An analysis of the joint distribution of the timing of extremes at these two altitudes indicates the presence of two regimes: one in which the timing is synchronized between these two layers, and the other in which the occurrence of extremes is asynchronous. These results are interpreted physically using an idealized mechanistic model of the surface layer momentum budget.

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