Inverse modelling for the tropospheric chemical state estimation by 4-dimensional variational data assimilation from routinely and campaign platforms

The use of models to analyse the complex atmospheric processes deals with a lot of uncertainties of key parameters, most prominently the emission rates along with the initial values. Especially for campaigns, the ability to analyse the processes is dependent on the most precise state of the variables needed for the parametrisation of the system, notably the emissions. Using its 4D-var and inverse modelling scheme, the chemistry transport model EURAD-IM is able to provide optimised initial state variables, highlighting the optimisation of the emission factors for the gas phase. In order to address how emission plumes can be identified, real case studies were applied with EURAD-IM to study the dispersion of the anthropogenic emissions over regional to urban surface within the planetary boundary layer. To achieve a high analysis skill, some features needed to be updated and also some new to be developed and added to the model setup. The online calculation of emissions in the CTM has been coupled to the joint optimisation of initial values and emission rates, providing detailed spatial and temporal emission distribution per source and per grid cell. Moreover, improvement of the background emission factor error covariances is achieved by including additional correlations between the emitted species and rectifying the standard deviations of the emission factors, optimising, thus, the precondition of the minimisation problem. In addition, assimilation of the comprehensive observational set of PEGASOS project during campaign in the polluted region of Po valley, performed to study the vertical structure of the atmosphere, analysing the mixing within the PBL and to validate the airborne data influence on the model performance. Quality control of the assimilation procedure, obtained by χ2-validation and comparison with independent observations, shows successful minimisation performance of the 4D-var algorithm. The case study analysis concluded to optimised emission factors, addressing also the lack of representativity of observations (such as NO2) by the high resolution of the nesting technique - up to 1 km. The more in depth assessment of the vertical mixing in the PBL, by the assimilation of the airborne campaign measurements, captures fairly clear the temporal variations of the emission patterns, the influence of the inverse temperature on the concentrations of pollutants and the layered structure of the PBL. In general, considerable improvement of the forecast quality of the model is achieved and the system's ability to provide improved chemical consistent simulation results throughout the PBL, mainly in urban polluted regions, is demonstrated. Besides, the assimilation of airborne measurements could be applied to shed light to the development of the PBL and the processes there in, information that is shown to miss when no campaign data are available

Μοντελοποίηση και υπολογιστική προσομοίωση της δυναμικής εξάπλωσης πυρκαγιών σε μεγάλης κλίμακας ετερογενείς εκτάσεις με χρήση γεωγραφικών πληροφοριακών συστημάτων και κυτταρικά αυτόματα

69 σ.Η παρούσα διπλωματική εργασία με τίτλο «Μοντελοποίηση και υπολογιστική προσομοίωση της δυναμικής εξάπλωσης πυρκαγιών σε μεγάλης κλίμακας ετερογενείς εκτάσεις με χρήση γεωγραφικών πληροφοριακών συστημάτων και κυτταρικά αυτόματα» εκπονήθηκε στα πλαίσια της προπτυχιακής εκπαίδευσής μου στη Σχολή Εφαρμοσμένων Μαθηματικών και Φυσικών Επιστημών του Εθνικού Μετσόβιου Πολυτεχνείου. Σκοπός της εργασίας είναι καταρχάς η γνωριμία και η μελέτη της υπολογιστικής μεθόδου των κυτταρικών αυτόματων, δίνοντας ιδιαίτερη έμφαση στην εφαρμογή τους σε μοντέλα προσομοίωσης της διάδοσης μιας φωτιάς σε δάσος και συγκρίνοντάς τα ως προς τη συμπεριφορά τους κατά τη διαδικασία αυτή. Επιπλέον βασικό στόχο αποτελεί η προσομοίωση της δυναμικής της εξάπλωσης μιας φωτιάς σε μεγάλης κλίμακας ετερογενές περιβάλλον συνδυάζοντας δεδομένα από Γεωγραφικά Πληροφοριακά Συστήματα (GIS data) και τη διαδικασία της επεξεργασίας ψηφιακής εικόνας (Image Processing) ώστε να λαμβάνονται υπ’όψη πλήθος παραγόντων που την επηρεάζουν, όπως η κλίση του εδάφους, τα χαρακτηριστικά του ανέμου και της βλάστησης στην περιοχή διάδοσης. Για το σκοπό αυτό επιχειρείται η κατασκευή ενός μοντέλου Κυτταρικού Αυτόματου για την προσομοίωση ενός πραγματικού γεγονότος, την πυρκαγιά που ξέσπασε στις Σπέτσες τον Αύγουστο του 1990 καταστρέφοντας ένα μεγάλο μέρος της βλάστησης του νησιού. Τέλος, αυτή η εφαρμογή του μοντέλου σε μια περίπτωση πραγματικής πυρκαγιάς δίνει τη δυνατότητα σύγκρισης των αποτελεσμάτων της προσομοίωσης με τα πραγματικά και προβάλει την επάρκεια της μεθόδου στην πρόβλεψη της διάδοσης της φωτιάς, γεγονός που θα μπορούσε να ωφελήσει στις προσπάθειες αντιμετώπισης μιας τέτοιας κατάστασης.This Diploma Thesis entitled «Modeling and Computational Simulation of Dynamic Fire Spread in Large Scale Heterogeneous Environments using Geographical Information Systems and Cellular Automata» was produced as part of my undergraduate education at the School of Applied Mathematics and Physical Sciences of The National Technical University of Athens. The purpose of the Thesis is, initially, the familiarity in the use of the computational method of Cellular Automata, emphasizing on their application to models that simulate the spread of a fire in forests and comparing them to their behaviour during this process.Moreover the basic objective is to simulate the dynamics of the spread of fire in large scale heterogeneous environment combining theory from combustion, fluid mechanics, data from Geographic Information Systems (GIS data) and digital image processing techniques. Key-factors that affect the fire spread, such as the slope of the ground, the wind’s velocity and direction and the type and the density of the vegetation in the area of dissemination were also taken into account. Towards this aim a model of Cellular Automata is constructed for the simulation of a real wildland fire incident: the wild fire that broke up on the Greek island Spetses in August of 1990 and destroyed a major part of the island’s forest. Finally, this model’s application on a real incident gives the opportunity to compare the simulation’s results with the real ones. This comparison points out the adequacy of the method to predict the spread of the fire, which could be very important and beneficial when dealing with similar situationsΖωή Γ. Πασχαλίδ

Inverse Modeling for the anthropogenic emission estimation by 4D-var

By taking a group of archaeological sites around the area of Borġ in-Nadur in south-east Malta, this collection of essays is an attempt at filling in the islands’ history during the long second millennium BC .peer-reviewe

Assimilation of crowd-sourced surface observations over Germany in a regional weather prediction system

Near-surface temperature and humidity observations over Germany, comingon the one hand from the citizen weather station’s network Netatmo and onthe other hand from synoptic weather stations, were assimilated into the lim-ited are mode of the Icosahedral Nonhydrostatic Model with 2-km resolution(ICON-D2). For that we use the Kilometre-Scale Ensemble Data Assimilation(KENDA) system and a bias-correction approach that improves the assimila-tion of the observations by taking into account the diurnal cycle of temperatureand humidity variables. Our results show that the assimilation of bias-correctedobservations from Netatmo stations reduces the forecast error considerably;meanwhile, the assimilation of Netatmo observations without bias correctionleads to a strong warm bias with a negative impact on forecast performance.In contrast, for the assimilation of synoptic observations the usage of ourbias-correction approach does not lead to any significant decrease in the fore-cast error, yet reduces the bias for the diurnal cycle of synoptic stations. Overall,it can be concluded that the forecast quality can gain from assimilating Netatmodata, provided an effective bias-correction approach is applied