Tall Tower Research Articles

Intercomparison of Planetary Boundary Layer Heights Using Remote Sensing Retrievals and ERA5 Reanalysis over Central Amazonia

The atmospheric boundary layer height (zi) is a key parameter in the vertical transport of mass, energy, moisture, and chemical species between the surface and the free atmosphere. There is a lack of long-term and continuous observations of zi, however, particularly for remote regions, such as the Amazon forest. Reanalysis products, such as ERA5, can fill this gap by providing temporally and spatially resolved information on zi. In this work, we evaluate the ERA5 estimates of zi (zi-ERA5) for two locations in the Amazon and corrected them by means of ceilometer, radiosondes, and SODAR measurements (zi-experimental). The experimental data were obtained at the remote Amazon Tall Tower Observatory (ATTO) with its pristine tropical forest cover and the T3 site downwind of the city of Manaus with a mixture of forest (63%), pasture (17%), and rivers (20%). We focus on the rather typical year 2014 and the El Niño year 2015. The comparison of the experimental vs. ERA5 zi data yielded the following results: (i) zi-ERA5 underestimates zi-experimental daytime at the T3 site for both years 2014 (30%, underestimate) and 2015 (15%, underestimate); (ii) zi-ERA5 overestimates zi-experimental daytime at ATTO site (12%, overestimate); (iii) during nighttime, no significant correlation between the zi-experimental and zi-ERA5 was observed. Based on these findings, we propose a correction for the daytime zi-ERA5, for both sites and for both years, which yields a better agreement between experimental and ERA5 data. These results and corrections are relevant for studies at ATTO and the T3 site and can likely also be applied at further locations in the Amazon.

A precise method unaffected by atmospheric reabsorption for ground-based retrieval of red and far-red sun-induced chlorophyll fluorescence

Remote sensing employs solar-induced chlorophyll fluorescence (SIF) as a proxy for photosynthesis from field to airborne and satellite sensors. The investigation of SIF offers a unique way of studying vegetation functioning from the local to the global scale. However, the passive, optical retrieval of the SIF signal is still challenging. Common retrieval approaches extract the SIF infilling directly from atmospheric oxygen bands in down-welling and up-welling radiance. They often involve a complex signal correction to compensate for atmospheric reabsorption and require long computing time. In contrast, the exploitation of solar Fraunhofer lines is devoid of atmospheric disturbances. We propose a new retrieval method for red and far-red SIF directly from up-welling radiance spectra in the spectral range between 650 nm and 810 nm by applying Partial Least Squares (PLS) regression machine learning. Solar Fraunhofer lines are exploited for SIF retrieval with the PLS approach by excluding telluric absorption features. The PLS models are trained and tested on synthetic reflectance and SIF data modeled with SCOPE. We identified a logarithmic relationship of the retrieval error with respect to signal-to-noise ratio of the instrument. The approach has been tested with real-world data measured by the Fluorescence Box (FloX), and evaluated against two well-established retrieval methods: the spectral fitting method (SFM) and the singular value decomposition (SVD). PLS models exploiting solar Fraunhofer lines retrieved meaningful SIF values with high precision and demonstrated robustness against atmospheric reabsorption, including from a 100m tall tower. In addition, PLS retrieval requires no complex correction for atmospheric reabsorption and computes 37 times faster than SFM. Hence, PLS retrieval allows fast and robust exploitation of SIF from solar Fraunhofer lines with high precision under conditions in which other retrieval approaches require complex atmospheric correction.

Comprehensive assessment of vertical variations in urban atmospheric CO2 concentrations by using tall tower measurement and an atmospheric transport model

In this study, we performed a comprehensive assessment of the vertical CO2 concentration in the urban atmosphere using measurements at two different heights (113 m and 420 m) in Seoul, South Korea. The difference in CO2 concentration between the two altitudes (△CO2 = CO2 at 113 m minus CO2 at 420 m) showed a significant diurnal variation, with the highest at 07:00 (19.9 ppm) and the lowest at 16:00 (3.9 ppm). When the planetary boundary layer (PBL) rose above the two sites (daytime), the CO2 concentrations at the two altitudes were highly correlated (r = 0.87) with low △CO2. In contrast, when the PBL was located between the two sites (night time), the correlation coefficient of the CO2 concentration between the two altitudes decreased by 0.55 with a high △CO2. To explain the cause of this variation in △CO2 according to PBL, we performed Weather Research and Forecasting-stochastic time-inverted Lagrangian transport (WRF-STILT) simulations. Simulations showed that CO2 measurements at two different heights were influenced by the same nearby urban areas during the daytime. However, the site above the PBL only measured the CO2 of air transported from the outside downtown area during the night time. Consequently, the observed night time △CO2 is explained by the difference in air mass between the two measurements owing to PBL variations. The night time △CO2 further implicates the local attribution of observed CO2 below the PBL by removing the effect from the remote area. Because of this unique night time characteristic of △CO2, we evaluated the changes in CO2 concentration in Seoul during the COVID-19 period. Compared to the pre-COVID-19 period, △CO2 clearly decreased from 26.5 ppm to 6.2 ppm with the implementation of social distancing, thus confirming the decreasing local influence of CO2 concentrations. Our findings highlight the potential of atmospheric CO2 monitoring at high altitudes as an observation-based method to assess the effectiveness of local carbon management.

Relationship between Land Use and Spatial Variability of Atmospheric Brown Carbon and Black Carbon Aerosols in Amazonia

The aerosol radiative effect is an important source of uncertainty in estimating the anthropogenic impact of global climate change. One of the main open questions is the role of radiation absorption by aerosols and its relation to land use worldwide, particularly in the Amazon Rainforest. Using AERONET (Aerosol Robotic Network) long-term measurements of aerosol optical depth (AOD) at a wavelength of 500 nm and absorption AOD (AAOD) at wavelengths of 440, 675, and 870 nm, we estimated the fraction and seasonality of the black carbon (BC) and brown carbon (BrC) contributions to absorption at 440 nm. This was conducted at six Amazonian sites, from central Amazon (Manaus and the Amazon Tall Tower Observatory—ATTO) to the deforestation arc (Rio Branco, Cuiabá, Ji-Paraná, and Alta Floresta). In addition, land use and cover data from the MapBiomas collection 6.0 was used to access the land transformation from forest to agricultural areas on each site. The results showed, for the first time, important geographical and seasonal variability in the aerosol optical properties, particularly the BC and BrC contributions. We observed a clear separation between dry and wet seasons, with BrC consistently accounting for an average of approximately 12% of the aerosol AAOD at 440 nm in the deforestation arc. In central Amazon, the contribution of BrC was approximately 25%. A direct relationship between the reduction in forests and the increase in the area dedicated to agriculture was detected. Moreover, places with lower fractions of forest had a smaller fraction of BrC, and regions with higher fractions of agricultural areas presented higher fractions of BC. Therefore, significant changes in AOD and AAOD are likely related to land-use transformations and biomass burning emissions, mainly during the dry season. The effects of land use change could introduce differences in the radiative balance in the different Amazonian regions. The analyses presented in this study allow a better understanding of the role of aerosol emissions from the Amazon Rainforest that could have global impacts.

Variations and sources of volatile organic compounds (VOCs) in urban region: insights from measurements on a tall tower

Abstract. Volatile organic compounds (VOCs) are key precursors of ozone and particulate matter, which are the two dominant air pollutants in urban environments. However, compositions and sources of VOCs in urban air aloft have rarely been reported so far. To address this matter, highly time-resolved measurements of VOCs were made by a proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS) at a 450 m platform on the Canton Tower in Guangzhou, China. A combination of in situ measurements and modeling techniques was used to characterize variations in and sources of VOCs. Five sources were identified from positive matrix factorization (PMF) analysis, namely daytime mixed (e.g., biogenic emissions and secondary formation), visitor-related (e.g., human breath, cooking, and volatilization of ethanol-containing products), vehicular–industrial, regional transport, and volatile chemical product (VCP) (i.e., volatilization of personal care products), contributing on average to 21 %, 30 %, 28 %, 10 %, and 11 % of total VOC (TVOC) mixing ratios, respectively. We observe that contributions of the visitor-related source, mainly composed of ethanol, followed with the variation in visitor numbers on the tower well. The VCP-dominated source only had an average contribution of ∼5.7 ppb during the campaign, accounting for a small fraction (11 %) of TVOC mixing ratios but a large fraction (22 %) of the total OH reactivity. However, large fractions of reactive VOC species, e.g., monoterpenes (49 %), were attributed to the VCP-dominated source, indicating important contributions of VCPs to ambient concentrations of these species in urban environments. Vertical profiles of air pollutants (namely NOx, ozone, Ox, and PM2.5), measured at 5, 118, 168, and 488 m, exhibited more evident gradients at night than in the daytime owing to the stronger stability of the nocturnal boundary layer. Mixing ratios of VOC species during the nighttime generally decreased with time when the 450 m platform was located in the nocturnal residual layer and markedly increased when impacted by emissions at ground level. The results in this study demonstrated composition characteristics and sources of VOCs in urban air aloft, which could provide valuable implications in making strategies for control of VOCs and secondary air pollutants.

Lagrangian Particle Dispersion Models in the Grey Zone of Turbulence: Adaptations to FLEXPART-COSMO for Simulations at 1 km Grid Resolution

Lagrangian particle dispersion models (LPDMs) are frequently used for regional-scale inversions of greenhouse gas emissions. However, the turbulence parameterizations used in these models were developed for coarse resolution grids, hence, when moving to the kilometre-scale the validity of these descriptions should be questioned. Here, we analyze the influence of the turbulence parameterization employed in the LPDM FLEXPART-COSMO model. Comparisons of the turbulence kinetic energy between the turbulence schemes of FLEXPART-COSMO and the underlying Eulerian model COSMO suggest that the dispersion in FLEXPART-COSMO suffers from a double-counting of turbulent elements when run at a high resolution of 1 times 1 ,hbox {km}^2. Such turbulent elements are represented in both COSMO, by the resolved grid-scale winds, and FLEXPART, by its stochastic parameterizations. Therefore, we developed a new parametrization for the variations of the winds and the Lagrangian time scales in FLEXPART in order to harmonize the amount of turbulence present in both models. In a case study for a power plant plume, the new scheme results in improved plume representation when compared with in situ flight observations and with a tracer transported in COSMO. Further in-depth validation of the LPDM against methane observations at a tall tower site in Switzerland shows that the model’s ability to predict the observed tracer variability and concentration at different heights above ground is considerably enhanced using the updated turbulence description. The high-resolution simulations result in a more realistic and pronounced diurnal cycle of the tracer concentration peaks and overall improved correlation with observations when compared to previously used coarser resolution simulations (at 7 km times 7 km). Our results indicate that the stochastic turbulence schemes of LPDMs, developed in the past for coarse resolution models, should be revisited to include a resolution dependency and resolve only the part of the turbulence spectrum that is a subgrid process at each different mesh size. Although our new scheme is specific to COSMO simulations at 1 times 1 ,hbox {km}^2 resolution, the methodology for deriving the scheme can easily be applied to different resolutions and other regional models.

Comparison of Seismic Response of Mono and Hybrid Structural System for Tall Windmill Tower considering Near-field and Far-field Earthquake

The windmill towers are the tall structures which are used as supporting mechanism for mounting the nacelle and rotor of windmill. These tower structures are conventionally steel structures with monopole configuration. It may be possible that these towers are installed in area of high earthquake risk and they are subjected to natural disaster like earthquake during its life span. The conventional monopole towers are not useful for very tall windmill tower in seismically active regions owing to slender effect. To reduce damages in conventional monopole tower constructed in near filed seismic regions, the new hybrid structural system which is blending of monopole and lattice configuration is proposed in present research. The mass and stiffness of structure are important parameters to resist the seismic forces, therefore in present research, new structural configuration is proposed which gives more stiffness to structure. The 125 mt high conventional monopole windmill tower is modelled in the numerical simulation and appropriate model of hybrid tower is also modelled in FE software. Both monopole and hybrid towers are subjected to natural disaster like earthquake, considering different near field and far filed Seismic excitation. Detailed dynamic analysis of both towers was carried out and response of monopole and hybrid tower was compared for parameters like displacement in time domain, baes shear in time domain and response spectra of structure. From the results obtained using numerical investigation, it is concluded that the innovative hybrid structural system is more effective in tall windmill tower and can be used efficiently to resist the natural disasters like earthquake.

Solar Typologies: A Comparative Analysis of Urban Form and Solar Potential

Efficient use of energy in the construction sector is a pillar of the European Union’s 2050 climate protection goals, yet legislation makes no explicit reference to urban morphology or building form, which are recognized as key to energy performance in buildings. Rapidly changing energy standards and new requirements for on-site energy production demand a vigorous scrutiny of established urban typologies that are largely the product of an older energy regime. The research explores a set of 312 building shapes with floor-to-area ratio (FAR) of 3 within a given plot to identify emerging trends, ranges, and correlations between geometric variables, visual comfort, and energy indicators. Cases are grouped and evaluated in relation to three main urban typologies to highlight unique features related to each typology. The paper also compares two groups of results related to passive and active solar potential, respectively, to identify formal traits that are specific to each of these two design strategies. Finally, the research ranks design options based on total energy use taking into account the energy need for artificial lighting as well as contributions from both passive energy savings and active energy production. Results show that energy demand across cases varies by a factor 2 for passive strategies and a factor 5 when active potential is considered based on shape alone. Best results are clearly positioned at the two extremes of the geometric and proportional range. On the one hand, low-rise compact bar and courtyard buildings that are perhaps most prevalent in our cities today may be effectively retrofitted to meet active energy targets. On the other hand, extremely tall and slim towers appear to be the only typology in the study with the potential to achieve zero-energy status by virtue of their form alone. The work sheds light on the formal implications of EU energy mandates and offers a glimpse of how buildings may adapt to the combined selective pressures of high on-site energy fraction and low energy use to shape our future cities.

Simulation of an orographic gravity wave above the Amazon rainforest and its influence on gases transport near the surface

The influence of the topography at the ATTO site (Amazon Tall Tower Observatory) in the formation of Gravity Waves (GW) was investigated in this work. The role of these waves in gas transport on different heights in the nocturnal boundary layer, was also investigated. For this, were analyzed: experimental data of wind speed, temperature, humidity and CO2 to identify the GW. Furthermore satellite images, ECMWF ERA5 (European Center for Medium-Range Weather Forecasts) reanalysis, and numerical simulations from the mesoscale JULES-CCATT-BRAMS model (Brazilian Regional Atmospheric Modeling System) version 5.3 were used to perform GW simulations. The simulations involved two configurations (Control-With Topography and No Topography). The sattelite images made it clear that the GW was not associated with convective activities. The simulations showed clear ondulatory signs in air temperature, vertical component of the wind, and gases like CO and O3. Moreover, they also reveal that the wave originated by the presence of the local topography and this orograph gravity wave had and important role in the transport of gases above the ATTO site.

Contribution from a eutrophic temperate estuary to the landscape flux of nitrous oxide

For mitigation of climate change, all sources and sinks of greenhouse gases from the environment must be quantified and their driving factors identified. Nitrous oxide (N2O) is a strong greenhouse gas, and the contribution of aquatic systems to the global N2O budget remains poorly constrained. In this study, we measured N2O concentrations in a eutrophic coastal system, Roskilde Fjord (Denmark), and combined measurements with statistical modeling to quantify the N2O fluxes and budget in the system over a period of six months. To do so, we collected water at 15 sampling points and measured N2O concentrations along with physico-chemical water quality parameters, e.g. temperature, salinity, dissolved inorganic nitrogen and phosphorus, and silicon. We used mixed-effect regression models to predict N2O concentrations in the water from water quality parameters. We then derived N2O fluxes using well-established equations of N2O solubility and water-atmosphere exchanges. These fluxes were then put in perspective with those measured at the landscape scale by eddy-covariance at a 96 m nearby tall tower, and to those estimated from the agricultural land next to the fjord using Intergovernmental Panel on Climate Change (IPCC) guidelines. N2O concentrations in the Roskilde Fjord ranged between 2.40 and 8.05 nmol l−1. The best fitting model between water parameters and N2O concentrations in water included phosphorus and temperature. We estimated that (i) Roskilde Fjord was a sink of N2O, with a median inward flux of -0.04 nmol m−2 s−1, (ii) while the surrounding median agricultural flux was 0.13-0.18 nmol m−2 s−1, and (iii) the median landscape flux was 0.07 nmol m−2 s−1. All estimates of N2O fluxes were of the same magnitude and consistent with each other. These preliminary results need to be consolidated by further research.

3D Mapping of Winter Lightning in Japan with an Array of Discone Antennas

We have developed a 3D lightning mapping system with an array of Discone Antennas working in the medium frequency‐high frequency (MF‐HF) bands. This system is called discone antenna lightning mapping array (DALMA) and has been deployed in Hokuriku area of Japan for the 3D mapping of winter lightning. Radio waves in the MF‐HF bands are rarely used for lightning 3D mapping due to large noises in these frequency bands. However, we have demonstrated in this paper that by using a wideband antenna, 3D mapping in the MF‐HF bands can also produce satisfactory results. We have analyzed two lightning flashes with complicated features observed in the last winter. In the first flash, we have successfully mapped an upward leader triggered by a negative cloud‐to‐ground (CG) lightning from a tall tower. In the second flash, we have successfully mapped a fast downward leader preceding an intense return stroke. Finally, we have also discussed the advantages of DALMA compared with other 3D mapping systems in LF or very high frequency (VHF) bands. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Mapping the evolution of Canada’s wind energy fleet

This paper describes the development of a data set mapping all commercial wind turbines in Canada: the 9th largest onshore wind energy fleet in the world. Details contained in the data enable the analysis of the evolution of commercially deployed wind turbines as well as the illustrating the effects of the introduction and cessation of different policies affected historical deployment. In total, over 6700 turbines spanning more than 265 projects and nearly 14.0 GW of generating capacity were indexed including coordinates, model, manufacturer, owner, tower height and commissioning date. Data were compiled from publicly available sources including planning documents, technical reports, environmental impact studies and acoustic emission reports. In 2021, average rotor diameters were 140 m with 108 m tall towers, more than triple the average diameter and double the average tower height from 20 years ago. The analysis of this data found that a typical wind farm in Canada consists of 0.97 turbines/km2, while the typical installed capacity density has recently jumped from around 1 to 2.94 MW/km2 in 2021. Competitive procurement policies have often trended towards larger installed capacities, whereas smaller wind farms emerged more often when policies directed at community ownership were in place. Policies that encouraged local manufacturing developed regional clusters of particular manufacturers, but generally ceased after the local manufacturing policies ended. This work serves as a benchmark for the evolution of wind energy in Canada and a framework for similar data sets in other jurisdictions, and provides a resource for academic researchers, wind farm developers, government bodies and planning agencies as well as the general public.

Modification of Fraser’s Method for the Atmospheric CO2 Mass Estimation by Using Satellite Data

One of the most critical greenhouse gases in the atmosphere is carbon dioxide (CO2) due to its long-lasting and negative impact on climate change. The global atmospheric monthly mean CO2 concentration is currently greater than 410 ppm which has changed dramatically since the industrial era. To choose suitable climate change mitigation and adaptation strategies it is necessary to define carbon dioxide mass distribution and global atmospheric carbon dioxide mass. The available method to estimate the global atmospheric CO2 mass was proposed in 1980. In this study, to increase the accuracy of the available method, various observation platforms such as ground-based stations, ground-based tall towers, aircrafts, balloons, ships, and satellites are compared to define the best available observations, considering the temporal and spatial resolution. In the method proposed in this study, satellite observations (OCO2 data), from January 2019 to December 2021, are used to estimate atmospheric CO2 mass. The global atmospheric CO2 mass is estimated around 3.24 × 1015 kg in 2021. For the sake of comparison, global atmospheric CO2 mass was estimated by Fraser’s method using NOAA data for the mentioned study period. The proposed methodology in this study estimated slightly greater amounts of CO2 in comparison to Fraser’s method. This comparison resulted in 1.23% and 0.15% maximum and average difference, respectively, between the proposed method and Fraser’s method. The proposed method can be used to estimate the required capacity of systems for carbon capturing and can be applied to smaller districts to find the most critical locations in the world to plan for climate change mitigation and adaptation.

Methane, carbon dioxide, hydrogen sulfide, and isotopic ratios of methane observations from the Permian Basin tower network

Abstract. We describe the instrumentation, calibration, and uncertainty of the network of ground-based, in situ, cavity ring down spectroscopy (CRDS) greenhouse gas (GHG) measurements deployed in the Permian Basin. The primary goal of the network is to be used in conjunction with atmospheric transport modeling to determine methane emissions of the Delaware sub-basin of the Permian Basin oil and natural gas extraction area in Texas and New Mexico. Four of the measurements are based on tall communications towers, while one is on a building on a mountain ridge, with the recent addition of a small tower at that site. Although methane (CH4) is the primary species of interest, carbon dioxide (CO2), hydrogen sulfide (H2S), and the isotopic ratio of methane (δ13CH4) are also reported for a subset of the sites. Measurements were reported following the WMO X2004A scale for CH4 and the WMO X2019 scale for CO2. CRDS instruments were calibrated for CH4 and CO2 in the laboratory prior to deployment. For H2S, data were offset-corrected using the minimum 40 min running mean value of the day, and for δ13CH4, calibrations were based on laboratory data. We describe the characteristics of the dataset with a set of illustrative analyses. Methane and carbon dioxide showed strong seasonality, with a well-defined diurnal cycle during the summer, which was opposed to the winter, when a diurnal cycle was absent. CH4 enhancements to the background, during the winter, are up to twice the summer values, which is attributed to the changes in boundary layer depth and wind speed. The largest CH4 enhancements occurred when winds blow from the center of the Delaware sub-basin, where most of the methane emissions come from. The magnitude of enhancements of CO2 did not present seasonality. H2S enhancements indicated a potential source northeast of the tower (Hobbs, New Mexico) where the inlet is installed. Isotopic ratios of methane indicated that oil and natural gas extraction is the source of local methane in the region. The hourly-averaged data, starting on 1 March 2020 and described in this paper, are archived at The Pennsylvania State University Data Commons at https://doi.org/10.26208/98y5-t941 (Monteiro et al., 2021).

Vertical propagation of submeso and coherent structure in a tall and dense Amazon Forest in different stability conditions PART I: Flow structure within and above the roughness sublayer

Understanding the processes that govern the mixing and transport of scalars within and above the Amazon Forest is of great importance for many environmental applications. The impact of atmospheric stability on the roughness sublayer (RSL) as well as the influence on it by the processes in the overlying atmosphere are investigated using measurements collected at the Atmospheric Tall Tower Observatory. Five different stabilities are defined according to the turbulent fluxes’ behaviour. Ejections dominate the transport in the RSL. In near neutral and unstable conditions coherent structures propagate up to 2–3 times the canopy height (h) and intermittently penetrate in the lowest part of the forest where sweeps drive the transport processes. In the unstable regime a weakening of the wind inflection at the canopy top and a transition to a convective regime above z = 2 h are observed. In stable conditions three regimes were defined characterised by a progressive lowering of the RSL and the weakening of the mixing-layer type coherent structures. In the ‘weakly stable’ regime the intense momentum and scalar fluxes appear driven by the coherent structures being able to penetrate inside the canopy intermittently coupling the flow above and within the forest. The ‘very stable’ regime is characterized by weak winds, a weakening of coherent structures and a decrease of the turbulent fluxes inhibited by buoyancy. The definition of a ‘super stable’ regime allowed the identification of a peculiar condition characterized by low-wind and weak coherent structures confined close to the canopy top and producing negligible transport. Submeso motions dominate the flow dynamics in this regime both above and inside the RSL. Multiresolution analysis highlights the ability of submeso motions to propagate inside the canopy and to modulate the exchange, particularly of scalars, fully driving the large positive CO2 flux observed inside the forest in the super stable regime.

Vertical propagation of submeso and coherent structure in a tall and dense amazon forest in different stability conditions. PART II: Coherent structures analysis

Observations of the vertical structure of the turbulent flow in different stability regimes above and within the Amazon Forest at the Amazon Tall Tower Observatory (ATTO) site have been presented in Part I. Here, the influence of stability on the inception and development of coherent structures is investigated. According to the mixing-layer analogy the coherent vortices that dominate the turbulent flows at the canopy-atmosphere interface are generated by hydrodynamical instabilities triggered by an inflection in the vertical profile of the mean wind speed at or near the canopy top. The coherent motions time, Tpeak and separation length scale, Λ, depend on the shear length scale, Ls, close to the canopy top. The present analysis studies the characteristics of Ls, Tpeak and Λ in the five stability regimes defined in Part I.The behaviour of Ls with stability is evaluated and parameterized. Ls increases with decreasing stability, presenting two asymptotes for large unstable and stable stratification and a linear behaviour close to neutral stratification. Coherent structures and their timescale are detected with an original method based on the autocorrelation functions of 5-min subsets of turbulent quantities. The vertical time scale is larger in neutral conditions and decreases for both increasing and decreasing stability. At the canopy top the separation length scale presents a linear dependence on Ls, whose slope is maximum in neutral conditions and decreases departing from neutrality. An original parameterization of the dependence of this slope on h/L, where h is the canopy height and L is the Obukhov length, is shown. Combining the parameterizations, the dependence of the separation length scale is finally presented. Λ has a maximum for slightly unstable conditions, linearly decreases towards neutral and weakly stable stratifications and then it tends to zero for very intense unstable and stable stratifications.

Flue gas cleaning by periodic absorption

AbstractSimulations and designs are presented of conventional and periodic SO2 absorption from exhaust gases using salt water as absorption solvent. Operating conditions resemble those of a maritime operation, involving relatively small amounts of SO2, so the separation is in the linear region. The advantages of periodic operation, as already demonstrated for conventional distillation remain valid for absorption processes: Less tall towers, than staged towers are possible, or substantially less salt water is required for the process employing periodic cycling.

Characteristics of the derived energy dissipation rate using the 1 Hz commercial aircraft quick access recorder (QAR) data

Abstract. The cube root of the energy dissipation rate (EDR), as a standard reporting metric of atmospheric turbulence, is estimated using 1 Hz quick access recorder (QAR) data from Korean-based national air carriers with two different types of aircraft (Boeing 737 (B737) and Boeing 777 (B777)), archived for 12 months from January to December 2012. The EDRs are estimated using three wind components (zonal, meridional, and derived vertical wind) and the derived equivalent vertical gust (DEVG) of the 1 Hz post-flight data by applying all possible EDR methods. Wind components are used to calculate three different EDRs, utilizing the second-order structure function, power spectral density, and von Kármán wind spectrum and maximum-likelihood method. In addition, two DEVG-based EDRs are calculated using the lognormal mapping technique and the predefined parabolic relationship between the observed EDR and DEVG. When the reliability of lower-rate (1 Hz) data to estimate the EDR is examined using the higher-rate (20 Hz) wind data obtained from a tall tower observatory, it is found that the 1 Hz EDR can be underestimated (2.19 %–12.56 %) or overestimated (9.32 %–10.91 %). In this study, it is also found that the structure-function-based EDR shows lower uncertainty (2.19 %–8.14 %) than the energy spectrum-based EDRs (9.32 %–12.56 %) when the 1 Hz datasets are used. The observed EDR estimates using 1 Hz QAR data are examined in three strong turbulence cases that are relevant to clear-air turbulence (CAT), mountain wave turbulence (MWT), and convectively induced turbulence (CIT). The observed EDR estimates derived from three different wind components show different characteristics depending on potential sources of atmospheric turbulence at cruising altitudes, indicating good agreement with selected strong turbulence cases with respect to turbulence intensity and incident time. Zonal wind-based EDRs are stronger in the CAT case that is affected by synoptic-scale forcing such as upper-level jet/frontal system. In the CIT case, vertical wind-based EDRs are stronger, which is related to convectively induced gravity waves outside the cloud boundary. The MWT case has a peak of the EDR based on both the zonal and vertical winds, which can be related to the propagation of mountain waves and their subsequent breaking. It is also found that the CAT and MWT cases occurred by synoptic-scale forcing have longer variations in the observed EDRs before and after the turbulence incident, while the CIT case triggered by a mesoscale convective cell has an isolated peak of the EDR. Current results suggest that the 1 Hz aircraft data can be an additional source of the EDR estimations contributing to expand more EDR information at the cruising altitudes in the world and that these data can be helpful to provide a better climatology of aviation turbulence and a situational awareness of cruising aircraft.

Infinitely Tall Pop-up Towers

Infinitely Tall Pop-up Towers

ОПРЕДЕЛЕНИЕ ОБЩЕГО СОДЕРЖАНИЯ ДИОКСИДА УГЛЕРОДА НАД ТЕРРИТОРИЕЙ РОССИИ ПО ДАННЫМ ОТЕЧЕСТВЕННОГО КОСМИЧЕСКОГО АППАРАТА “МЕТЕОР-М” № 2

A description is given of the method for the retrieval of atmospheric column-averaged dry-air mole fractions of carbon dioxide (XCO2) from the data of IKFS-2 infrared Fourier spectrometer on board the Meteor-M Russian meteorological satellites. The method is based on estimating XCO2 using a second-order regression, whose predictors are the effective spectral optical depths of the atmosphere in the infrared region of 8-14 μm. The optical depth is determined using spectral intensities of outgoing radiation measured by the IKFS-2 as well as the calculated intensities of the Earth’s surface or cloud top simulated as a gray body with temperature T s. The temperature T s is retrieved from IKFS-2 measurements within the atmospheric microwindow at the wave number equal to 900.1 cm-1. The reference XCO2 values for constructing the regression were the results of contact CO2 measurements on the tall tower at the ZOTTO international observatory (Central Siberia) and at the NOAA observatory on the Mauna Loa volcano (Hawaii) in 2015-2016. The methodology was validated by comparing the XCO2 retrieved from Meteor-M No. 2 IKFS-2 measurements with parallel measurements over Siberia by the OCO and CrIS satellite spectrometers on board the OCO-2 and NOAA-20 satellites (USA). The maximum discrepancies in the daily estimates of the spatially averaged XCO2 during October 9-19, 2021 derived from the IKFS-2 data do not exceed 2.3 ppm versus the OCO data and 5 ppm versus the CrIS data.