Model studies on vibrationally-rotationally excited hydroxyl molecules in the mesopause region

2020 ◽  
Author(s):  
Justus Notholt ◽  
Holger Winkler ◽  
Stefan Noll
Keyword(s):  
Near Infrared ◽  
Measurement Data ◽  
Model Parameters ◽  
Chemical Production ◽  
Echelle Spectrograph ◽  
Mesopause Region ◽  
Rotational States ◽  
Model Studies ◽  
Temperature Component ◽  
Remotely Sense

<p>One of the standard methods to remotely sense the temperature of the mesopause region is based on spectroscopic measurements of near-infrared emissions of vibrationally-rotationally excited hydroxyl molecules, and to calculate  rotational temperatures. For the interpretation of the retrieved temperatures, the aspect of rotational thermalization is of great importance. We present results of a first-principle kinetic model of vibrationally-rotationally excited hydroxyl molecules which accounts for chemical production and loss processes as well as radiative and collision-induced vibrational-rotational transitions. The model allows one to assess deviations of the rotational populations from local thermodynamic equilibrium, and to identify the key parameters which control the rotational thermalization processes. The model simulations reproduce the observed bimodality in temperatures, i.e. a cold temperature component dominating the population of low rotational states, and a hot temperature component dominating higher states. The model results are compared to measurement data from the UVES echelle spectrograph at Cerro Paranal in Chile (Presentation EGU2020-3169) which allows us to confine free model parameters such as the rotational state changes in vibrational quenching process.</p>

Properties of OH roto-vibrational level populations in the Earth's mesopause region

2020 ◽  
Author(s):  
Stefan Noll ◽  
Holger Winkler ◽  
Oleg Goussev ◽  
Bastian Proxauf
Keyword(s):  
Vibrational Level ◽  
Near Infrared ◽  
Population Distribution ◽  
Echelle Spectrograph ◽  
Emission Layer ◽  
Mesopause Region ◽  
Important Indicator ◽  
Infrared Wavelength ◽  
Cold Component ◽  
Upper Level

<p>Chemiluminescent OH airglow emission dominates the nighttime radiation of the Earth's atmosphere in the near-infrared wavelength regime. It is an important indicator of the state and variability of the mesopause region at about 90 km. However, the interpretation of the line intensities suffers from uncertainties in the knowledge of the complex roto-vibrational level population distribution, which is far from local thermodynamic equilibrium (LTE). For a better understanding, we investigated these populations in detail mainly based on a high-quality high-resolution mean spectrum from the UVES echelle spectrograph at Cerro Paranal in Chile, which allowed us to measure about 1,000 individual lines including numerous resolved Λ-doublet components between 560 and 1060 nm. As the quality of the currently available sets of OH Einstein-A coefficients is not sufficient for accurate population retrievals, we derived an improved set by a semi-empirical approach, which benefited from the measurement of multiple lines with the same upper level. The resulting populations indicate a clear bimodality for each vibrational level, which is characterised by a cold component indicating the ambient temperature at the OH layer heights and a hot non-LTE component dominating high rotational levels. Our promising two-population fits allowed us to constrain the non-LTE contributions to rotational temperatures based on lines with upper states with low rotational and fixed vibrational quantum number, which are widely used to estimate temperatures in the mesopause region. The bimodality is also clearly indicated by the different population changes depending on the effective altitude of the OH emission layer. Only the cold component significantly decreases with increasing altitude. Our results will be very useful for the challenging modelling of the OH thermalisation process.</p>

scholarly journals Modeling of German Low Voltage Cables with Ground Return Path

Energies ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1265 ◽  
Author(s):  
Johanna Geis-Schroer ◽  
Sebastian Hubschneider ◽  
Lukas Held ◽  
Frederik Gielnik ◽  
Michael Armbruster ◽  
...  
Keyword(s):  
Low Voltage ◽  
Measurement Data ◽  
Analytical Calculation ◽  
Laboratory Measurement ◽  
Model Parameters ◽  
Calculation Methods ◽  
Modeling Approach ◽  
Measurement Results ◽  
Simulation Results ◽  
Return Path

In this contribution, measurement data of phase, neutral, and ground currents from real low voltage (LV) feeders in Germany is presented and analyzed. The data obtained is used to review and evaluate common modeling approaches for LV systems. An alternative modeling approach for detailed cable and ground modeling, which allows for the consideration of typical German LV earthing conditions and asymmetrical cable design, is proposed. Further, analytical calculation methods for model parameters are described and compared to laboratory measurement results of real LV cables. The models are then evaluated in terms of parameter sensitivity and parameter relevance, focusing on the influence of conventionally performed simplifications, such as neglecting house junction cables, shunt admittances, or temperature dependencies. By comparing measurement data from a real LV feeder to simulation results, the proposed modeling approach is validated.

scholarly journals Forest summer albedo is sensitive to species and thinning: how should we account for this in Earth system models?

2014 ◽  
Vol 11 (8) ◽  
pp. 2411-2427 ◽  
Author(s):  
J. Otto ◽  
D. Berveiller ◽  
F.-M. Bréon ◽  
N. Delpierre ◽  
G. Geppert ◽  
...  
Keyword(s):  
Forest Management ◽  
Tree Species ◽  
Near Infrared ◽  
Model Parameters ◽  
Earth System ◽  
Forest Thinning ◽  
Area Index ◽  
System Models ◽  
Maximum Change ◽  
Earth System Models

Abstract. Although forest management is one of the instruments proposed to mitigate climate change, the relationship between forest management and canopy albedo has been ignored so far by climate models. Here we develop an approach that could be implemented in Earth system models. A stand-level forest gap model is combined with a canopy radiation transfer model and satellite-derived model parameters to quantify the effects of forest thinning on summertime canopy albedo. This approach reveals which parameter has the largest affect on summer canopy albedo: we examined the effects of three forest species (pine, beech, oak) and four thinning strategies with a constant forest floor albedo (light to intense thinning regimes) and five different solar zenith angles at five different sites (40° N 9° E–60° N 9° E). During stand establishment, summertime canopy albedo is driven by tree species. In the later stages of stand development, the effect of tree species on summertime canopy albedo decreases in favour of an increasing influence of forest thinning. These trends continue until the end of the rotation, where thinning explains up to 50% of the variance in near-infrared albedo and up to 70% of the variance in visible canopy albedo. The absolute summertime canopy albedo of all species ranges from 0.03 to 0.06 (visible) and 0.20 to 0.28 (near-infrared); thus the albedo needs to be parameterised at species level. In addition, Earth system models need to account for forest management in such a way that structural changes in the canopy are described by changes in leaf area index and crown volume (maximum change of 0.02 visible and 0.05 near-infrared albedo) and that the expression of albedo depends on the solar zenith angle (maximum change of 0.02 visible and 0.05 near-infrared albedo). Earth system models taking into account these parameters would not only be able to examine the spatial effects of forest management but also the total effects of forest management on climate.

Dynamic Data-Driven Spatiotemporal System Behavior Prediction With Simulations and Sensor Measurement Data

2018 ◽  
Author(s):  
Xiangxue Zhao ◽  
Shapour Azarm ◽  
Balakumar Balachandran
Keyword(s):  
Dynamical System ◽  
Real Time ◽  
Measurement Data ◽  
Data Driven ◽  
Sensor Data ◽  
Model Parameters ◽  
High Fidelity ◽  
System Behavior ◽  
Sensor Measurement

Online prediction of dynamical system behavior based on a combination of simulation data and sensor measurement data has numerous applications. Examples include predicting safe flight configurations, forecasting storms and wildfire spread, estimating railway track and pipeline health conditions. In such applications, high-fidelity simulations may be used to accurately predict a system’s dynamical behavior offline (“non-real time”). However, due to the computational expense, these simulations have limited usage for online (“real-time”) prediction of a system’s behavior. To remedy this, one possible approach is to allocate a significant portion of the computational effort to obtain data through offline simulations. The obtained offline data can then be combined with online sensor measurements for online estimation of the system’s behavior with comparable accuracy as the off-line, high-fidelity simulation. The main contribution of this paper is in the construction of a fast data-driven spatiotemporal prediction framework that can be used to estimate general parametric dynamical system behavior. This is achieved through three steps. First, high-order singular value decomposition is applied to map high-dimensional offline simulation datasets into a subspace. Second, Gaussian processes are constructed to approximate model parameters in the subspace. Finally, reduced-order particle filtering is used to assimilate sparsely located sensor data to further improve the prediction. The effectiveness of the proposed approach is demonstrated through a case study. In this case study, aeroelastic response data obtained for an aircraft through simulations is integrated with measurement data obtained from a few sparsely located sensors. Through this case study, the authors show that along with dynamic enhancement of the state estimates, one can also realize a reduction in uncertainty of the estimates.

scholarly journals Evidence of a significant rotational non-LTE effect in the CO<sub>2</sub> 4.3 µm PFS-MEX limb spectra

2017 ◽  
Vol 10 (1) ◽  
pp. 265-271 ◽  
Author(s):  
Alexander A. Kutepov ◽  
Ladislav Rezac ◽  
Artem G. Feofilov
Keyword(s):  
Near Infrared ◽  
Thermal Structure ◽  
Radiative Lifetime ◽  
Martian Atmosphere ◽  
Vibrational States ◽  
Rotational States ◽  
First Results ◽  
Rotational Distribution ◽  
Multi Level ◽  
Excited Molecules

Abstract. Since January 2004, the planetary Fourier spectrometer (PFS) on board the Mars Express satellite has been recording near-infrared limb spectra of high quality up to the tangent altitudes ≈ 150 km, with potential information on density and thermal structure of the upper Martian atmosphere. We present first results of our modeling of the PFS short wavelength channel (SWC) daytime limb spectra for the altitude region above 90 km. We applied a ro-vibrational non-LTE model based on the stellar astrophysics technique of accelerated lambda iteration (ALI) to solve the multi-species and multi-level CO2 problem in the Martian atmosphere. We show that the long-standing discrepancy between observed and calculated spectra in the cores and wings of 4.3 µm region is explained by the non-thermal rotational distribution of molecules in the upper vibrational states 10011 and 10012 of the CO2 main isotope second hot (SH) bands above 90 km altitude. The redistribution of SH band intensities from band branch cores into their wings is caused (a) by intensive production of the CO2 molecules in rotational states with j > 30 due to the absorption of solar radiation in optically thin wings of 2.7 µm bands and (b) by a short radiative lifetime of excited molecules, which is insufficient at altitudes above 90 km for collisions to maintain rotation of excited molecules thermalized. Implications for developing operational algorithms for massive processing of PFS and other instrument limb observations are discussed.

scholarly journals Dynamic torque calibration by means of model parameter identification

ACTA IMEKO ◽  
2015 ◽  
Vol 4 (2) ◽  
pp. 39 ◽  
Author(s):  
Leonard Klaus ◽  
Barbora Arendacká ◽  
Michael Kobusch ◽  
Thomas Bruns
Keyword(s):  
Frequency Response ◽  
Dynamic Behaviour ◽  
Measurement Data ◽  
Model Parameters ◽  
Dynamic Calibration ◽  
Extended Model ◽  
Unknown Parameters ◽  
Measuring Device ◽  
Torque Transducer ◽  
Least Squares Approach

For the dynamic calibration of torque transducers, a model of the transducer and an extended model of the mounted transducer including the measuring device have been developed. The dynamic behaviour of a torque transducer under test is going to be described by its model parameters. This paper describes the models with these known and unknown parameters and how the calibration measurements are going to be carried out. The principle for the identification of the transducer's model parameters from measurement data is described using a least squares approach. The influence of a variation of the transducer's parameters on the frequency response of the expanded model is analysed.

scholarly journals Summertime canopy albedo is sensitive to forest thinning

2013 ◽  
Vol 10 (9) ◽  
pp. 15373-15414 ◽  
Author(s):  
J. Otto ◽  
D. Berveiller ◽  
F.-M. Bréon ◽  
N. Delpierre ◽  
G. Geppert ◽  
...  
Keyword(s):  
Forest Management ◽  
Tree Species ◽  
Structural Changes ◽  
Near Infrared ◽  
Canopy Structure ◽  
Model Parameters ◽  
Transfer Model ◽  
Forest Thinning ◽  
Crown Volume ◽  
The Difference

Abstract. Despite an emerging body of literature linking canopy albedo to forest management, understanding of the process is still fragmented. We combined a stand-level forest gap model with a canopy radiation transfer model and satellite-derived model parameters to quantify the effects of forest thinning, that is removing trees at a certain time during the forest rotation, on summertime canopy albedo. The effects of different forest species (pine, beech, oak) and four thinning strategies (light to intense thinning regimes) were examined. During stand establishment, summertime canopy albedo is driven by tree species. In the later stages of stand development, the effect of tree species on summertime canopy albedo decreases in favour of an increasing influence of forest thinning on summertime canopy albedo. These trends continue until the end of the rotation where thinning explains up to 50% of the variance in near-infrared canopy albedo and up to 70% of the variance in visible canopy albedo. More intense thinning lowers the summertime shortwave albedo in the canopy by as much as 0.02 compared to unthinned forest. The structural changes associated with forest thinning can be described by the change in LAI in combination with crown volume. However, forests with identical canopy structure can have different summertime albedo values due to their location: the further north a forest is situated, the more the solar zenith angle increases and thus the higher is the summertime canopy albedo, independent of the wavelength. Despite the increase of absolute summertime canopy albedo values with latitude, the difference in canopy albedo between managed and unmanaged forest decreases with increasing latitude. Forest management thus strongly altered summertime forest albedo.

Can high-frequency data enable better parameterization of water quality models and disentangling of DO processes?

2021 ◽  
Author(s):  
Jingshui Huang ◽  
Pablo Merchan-Rivera ◽  
Gabriele Chiogna ◽  
Markus Disse ◽  
Michael Rode
Keyword(s):  
Water Quality ◽  
High Frequency ◽  
Critical Role ◽  
Measurement Data ◽  
High Frequency Data ◽  
Model Parameters ◽  
Frequency Data ◽  
Quality Models ◽  
Model Parameter ◽  
Water Quality Models

&lt;p&gt;Water quality models offer to study dissolved oxygen (DO) dynamics and resulting DO balances. However, the infrequent temporal resolution of measurement data commonly limits the reliability of disentangling and quantifying instream DO process fluxes using models. These limitations of the temporal data resolution can result in the equifinality of model parameter sets. In this study, we aim to quantify the effect of the combination of emerging high-frequency monitoring techniques and water quality modelling for 1) improving the estimation of the model parameters and 2) reducing the forward uncertainty of the continuous quantification of instream DO balance pathways.&lt;/p&gt;&lt;p&gt;To this end, synthetic measurements for calibration with a given series of frequencies are used to estimate the model parameters of a conceptual water quality model of an agricultural river in Germany. The frequencies vary from the 15-min interval, daily, weekly, to monthly. A Bayesian inference approach using the DREAM algorithm is adopted to perform the uncertainty analysis of DO simulation. Furthermore, the propagated uncertainties in daily fluxes of different DO processes, including reaeration, phytoplankton metabolism, benthic algae metabolism, nitrification, and organic matter deoxygenation, are quantified.&lt;/p&gt;&lt;p&gt;We hypothesize that the uncertainty will be larger when the measurement frequency of calibrated data was limited. We also expect that the high-frequency measurements significantly reduce the uncertainty of flux estimations of different DO balance components. This study highlights the critical role of high-frequency data supporting model parameter estimation and its significant value in disentangling DO processes.&lt;/p&gt;

scholarly journals Understanding chemical production processes by using PLS path model parameters as soft sensors

2020 ◽  
Vol 139 ◽  
pp. 106841 ◽  
Author(s):  
Geert H. van Kollenburg ◽  
Jacoline van Es ◽  
Jan Gerretzen ◽  
Heleen Lanters ◽  
Roel Bouman ◽  
...  
Keyword(s):  
Path Model ◽  
Model Parameters ◽  
Chemical Production ◽  
Soft Sensors ◽  
Production Processes

scholarly journals Development of a Near-Infrared Echelle Spectrograph “NICE”

2007 ◽  
Vol 59 (2) ◽  
pp. 387-395 ◽  
Author(s):  
Tomoyasu Yamamuro ◽  
Hironobu Kawabata ◽  
Ko Nedachi ◽  
Yuichiro Nishimaki ◽  
Kentaro Motohara ◽  
...  
Keyword(s):  
Near Infrared ◽  
Echelle Spectrograph
Sign in / Sign up

Export Citation Format

Share Document