scholarly journals An integrated atmospheric modeling system for the simulation of coupled physical and chemical processes

2014 ◽  
Author(s):  
Jonilda Kushta
Keyword(s):  
Cloud Condensation Nuclei ◽  
Atmospheric Modeling ◽  
Radiative Transfer Model ◽  
Explicit Calculation ◽  
Limited Area ◽  
Transfer Model ◽  
Ice Nuclei ◽  
Meteorological Modelling ◽  
Physical And Chemical ◽  
Regional Atmospheric Modeling

Τα σωματίδια, είτε φυσικής είτε ανθρωπογενούς προέλευσης, επηρεάζουν την ακτινοβολία απορροφώντας ή/και σκεδάζοντας μέρος της ηλιακής και γήινης ακτινοβολίας. Αυτός ο μηχανισμός είναι γνωστός ως ‘άμεσος’ μηχανισμός αλληλεπίδρασης. Μέσω αυτής της διαδικασίας επηρεάζεται η θερμοδυναμική κατάσταση της ατμόσφαιρας καθώς και η χωροχρονική κατανομή των νεφών και του υετού. Ενας άλλος μηχανισμός αλληλεπίδρασης των σωματιδίων με τις ατμοσφαιρικές διεργασίες, ονομαζόμενος ‘έμμεσος’ μηχανισμός, δημιουργείται όταν τα σωματίδια πληρούν τις προϋποθέσεις να ενεργοποιηθούν ως πυρήνες συμπύκνωσης (cloud condensation nuclei – CCN) ή παγοποίησης (ice nuclei – IN). Μέσω αυτού του μηχανισμού τα σωματίδια τροποποιούν τις οπτικές ιδιότητες των νεφών καθώς και την χωρική και χρονική κατανομή του παραγόμενου υετού. Οι προαναφερθείσες αλλαγές στα θερμοδυναμικά χαρακτηριστικά της ατμόσφαιρας επηρεάζουν, σε ένα πολύπλοκο κύκλο, την κατανομή των σωματιδίων και αερίων ρύπων σε όλες τις φάσεις παραγωγής, μεταφοράς και εναπόθεσής τους. Επιπλέον, οι αλλαγές στην θερμοκρασιακή κατανομή και τις ροές ακτινοβολίας τροποποιούν τους ρυθμούς χημικών αντιδράσεων καθώς και τους φωτοχημικούς συντελεστές. Ως αποτέλεσμα αυτών των επιδράσεων, οι συγκεντρώσεις αερίων ρύπων (όπως του όζοντος) εμφανίζουν διαφορές που εξαρτώνται από μια σειρά παραμέτρων, μετεωρολογικής και χημικής φύσεως. Οι φυσικές και χημικές διεργασίες στην ατμόσφαιρα, ιστορικά, προσομοιώνονται με ξεχωριστά μοντέλα. Με αυτή την προσέγγιση, παρά την υπολογιστικά ελκυστική απόδοσή της, υπάρχουν ασυνέπειες στην περιγραφή των πεδίων (όταν η πληροφορία ανταλλάσσεται από το ένα μοντέλο στο άλλο) καθώς τα μοντέλα αυτά χρησιμοποιούν διαφορετικές χρονικές και χωρικές αναλύσεις και διαφορετικά συστήματα συντεταγμένων. Επιπλέον, η ξεχωριστή ανάλυση των διεργασιών δεν αφήνει χώρο για την -διπλής κατεύθυνσης- ανταλλαγή πληροφορίας (two way interaction) ώστε να μπορούν να περιγραφούν οι αλληλεπιδράσεις μεταξύ τους.Με την ενίσχυση των αποδείξεων πως αυτές οι αλληλεπιδράσεις παίζουν σημαντικό ρόλο σε εφαρμογές ποικίλης χρονικής διακύμανσης (από τοπικές προβλέψεις καιρού έως εφαρμογές κλιματικής αλλαγής), όπως αυτές κατεγράφησαν σε ειδικές εκθέσεις από την Διεθνή Επιτροπή για την Κλιματική Αλλαγή, η επιστημονική κοινότητα επικέντρωσε τις προσπάθειές της στη δημιουργία μοντέλων που συμπεριλαμβάνουν στο μέγιστο δυνατό βαθμό αυτές τις αλληλεπιδράσεις. Η εργασία αυτή είναι μέρος της ‘αλλαγής κατεύθυνσης’ προς την νέα επιστημονική έννοια της ‘Πρόβλεψης Χημικού Καιρού’ όπως ονομάστηκε από ειδικούς του χώρου. Το αντικείμενο αυτής της διατριβής είναι η προσθήκη νέων και η βελτίωση υφιστάμενων μηχανισμών και δυνατοτήτων στο αριθμητικό μοντέλο RAMS όπως αυτό έχει τροποποιηθεί από την Ομάδα Ατμοσφαιρικών Μοντέλων και Πρόγνωσης Καιρού (Ο.Α.Μ.Π.Κ.) του ΕΚΠΑ, με σκοπό να χρησιμοποιηθεί για την μελέτη των αλυσιδωτών αντιδράσεων των μηχανισμών στην ατμόσφαιρα. Το RAMS χρησιμοποιήθηκε ως πυρήνας της ανάπτυξης του ολοκληρωμένου αριθμητικού συστήματος λόγω του αναλυτικού μικροφυσικού σχήματος που περιέχει που δύναται να παίζει σημαντικό ρόλο στην ικανοποιητική προσομοίωση του ατμοσφαιρικού κύκλου του νερού. Oι σχετικές τροποποιήσεις που αφορούν τον άμεσο υπολογισμό (explicit calculation) των πυρήνων συμπύκνωσης και παγοποίησης στην ατμόσφαιρα πραγματοποιήθηκαν στα πλαίσια της προηγηθείσας διδακτορικής διατριβής του κυρίου Σταύρου Σολωμού. Το RAMS είναι ένα μοντέλο με δυνατότητες εμφώλευσης (nesting) που έχει χρησιμοποιηθεί από την Ο.Α.Μ.Π.Κ, καθώς και άλλες διεθνείς ομάδες, και έχει ελεχθεί ως προς την απόδοσή του σε ποικίλα ατμοσφαιρικά φαινόμενα. Το RAMS επεκτάθηκε στα πλαίσια αυτής της διατριβής με σχήματα χημείας αέριας, υγρής και στερεής φάσης και ατμοσφαιρικού κύκλου φυσικών σωματιδίων (σκόνης και αλατιού). Ο υπολογισμός ρυθμών φωτόλυσης, που καθορίζουν σε μεγάλο βαθμό τα επίπεδα ρύπανσης, ενσωματώθηκε στο μοντέλο ώστε να πραγματοποιηθεί άμεσα (online). To νέο σύστημα εμπλουτίστηκε με την ενσωμάτωση ενός νέου σχήματος ακτινοβολίας, το Rapid Radiative Transfer Model (RRTM), που περιέχει μια λεπτομερέστερη κατανομή μήκους κύματος της ακτινοβολίας σε σχέση με το προϋπάρχον σχήμα (Ηarrington, 1997). Η λεπτομερέστερη κατανομή είναι σημαντική για τον ακριβέστερο υπολογισμό των ρυθμών φωτόλυσης. Οι σημαντικότερες βελτιώσεις του μοντέλου που πραγματοποιήθηκαν στα πλαίσια αυτής της διατριβής, οι νέες δυνατότητες, καθώς και οι αλληλεπιδράσεις που λαμβάνονται υπόψη αριθμούνται ως εξής: 1.Ενσωμάτωση του υπολογισμού των φωτολυτικών ρυθμών ο οποίος έγινε απευθείας στο σχήμα ακτινοβολίας και λαμβάνει υπόψη την επίδραση νεφών και ρύπων στο ισοζύγιό της.2.Ενσωμάτωση της αέριας χημείας βασιζόμενη στο σχήμα SAPRC99, της χημείας υγρής και στερεής φάσης και για ανόργανες και για οργανικές ενώσεις.3.Επίδραση των φυσικών (σκόνη, αλάτι) και ανθρωπογενών (sulfates, nitrates) σωματιδίων στη -μικρού και μεγάλου μήκος κύματος- ακτινοβολία. Η επίδραση των υδροφιλικών σωματιδίων (αλάτι) λαμβάνει υπόψη και την υγρασία της ατμόσφαιρας, πέρα του μεγέθους των σωματιδίων που λαμβάνεται υπόψη για όλα τα προαναφερθέντα σωματίδια.4.Ενεργοποίηση των ανθρωπογενών σωματιδίων ως πυρήνες συμπύκνωσης (sulfates) επιπλέον των φυσικών σωματιδίων (σκόνη και αλάτι).5.Χρήση βιογενών εκπομπών από παραμετροποίηση από το μοντέλο (online), συμπεριλαμβανομένης και της δυνατότητας χρήσης διαφόρων θερμοκρασιών στο σχήμα παραμετροποίησης. Η χρήση διαφόρων δεδομένων εκπομπών, χρησιμοποιήθηκε ως ένα εργαλείο ελέγχου της ευαισθησίας του μοντέλου. Ειδικότερα ερευνήθηκε η επίδραση εκπομπών από την πολιτική αεροπορία λόγω της σημαντικής αύξησης αυτής της ανθρωπογενούς δραστηριότητας και της ιδιαιτερότητας των εκπομπών της (εκπομπές κυρίως στην μέση και ανώτερη τροπόσφαιρα).Το μοντέλο ονομάστηκε RAMS/ICLAMS (Regional Atmospheric Modeling System/Ιntegrated Community Limited Area Modeling System) και συμπεριλαμβάνεται επίσημα στην λίστα των state-of-the-art ολοκληρωμένων συστημάτων προσομοίωσης του COST action “Enhancing Meso-scale Meteorological Modelling Capabilities for Air Pollution and Dispersion Applications” (ES1004).Το ολοκληρωμένο σύστημα χρησιμοποιήθηκε ως εργαλείο για την ανάλυση των άμεσων και έμμεσων επιδράσεων των αερολυμάτων. Tο μοντέλο εφαρμόστηκε σε περιπτώσεις αυξημένων συγκεντρώσεων φυσικών και ανθρωπογενών σωματιδίων και μελετήθηκε η επίδρασή τους πάνω στο ισοζύγιο της ακτινοβολίας, την θερμοδυναμική της ατμόσφαιρας, την κατανομή νεφών και υετού, καθώς και τη συνεπαγόμενη επίδραση των θερμοδυναμικών αλλαγών στη κατανομή των σωματιδίων και τις συγκεντρώσεις του όζοντος.

scholarly journals Modeling the radiative effects of desert dust on weather and regional climate

2013 ◽  
Vol 13 (11) ◽  
pp. 5489-5504 ◽  
Author(s):  
C. Spyrou ◽  
G. Kallos ◽  
C. Mitsakou ◽  
P. Athanasiadis ◽  
C. Kalogeri ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Regional Climate ◽  
Lower Troposphere ◽  
Integrated Approach ◽  
Dust Particles ◽  
Radiative Transfer Model ◽  
Limited Area ◽  
Transfer Model ◽  
Radiative Effects ◽  
Desert Dust

Abstract. Mineral dust aerosols exert a significant effect on both solar and terrestrial radiation. By absorbing and scattering, the solar radiation aerosols reduce the amount of energy reaching the surface. In addition, aerosols enhance the greenhouse effect by absorbing and emitting outgoing longwave radiation. Desert dust forcing exhibits large regional and temporal variability due to its short lifetime and diverse optical properties, further complicating the quantification of the direct radiative effect (DRE). The complexity of the links and feedbacks of dust on radiative transfer indicate the need for an integrated approach in order to examine these impacts. In order to examine these feedbacks, the SKIRON limited area model has been upgraded to include the RRTMG (Rapid Radiative Transfer Model – GCM) radiative transfer model that takes into consideration the aerosol radiative effects. It was run for a 6 year period. Two sets of simulations were performed, one without the effects of dust and the other including the radiative feedback. The results were first evaluated using aerosol optical depth data to examine the capabilities of the system in describing the desert dust cycle. Then the aerosol feedback on radiative transfer was quantified and the links between dust and radiation were studied. The study has revealed a strong interaction between dust particles and solar and terrestrial radiation, with several implications on the energy budget of the atmosphere. A profound effect is the increased absorption (in the shortwave and longwave) in the lower troposphere and the induced modification of the atmospheric temperature profile. These feedbacks depend strongly on the spatial distribution of dust and have more profound effects where the number of particles is greater, such as near their source.

scholarly journals Impact of aerosol–radiation interaction on new particle formation

2021 ◽  
Vol 21 (13) ◽  
pp. 9995-10004
Author(s):  
Gang Zhao ◽  
Yishu Zhu ◽  
Zhijun Wu ◽  
Taomou Zong ◽  
Jingchuan Chen ◽  
...  
Keyword(s):  
Cloud Condensation Nuclei ◽  
Mixing Layer ◽  
Particle Formation ◽  
Radiative Transfer Model ◽  
Aerosol Size Distribution ◽  
Transfer Model ◽  
New Particle Formation ◽  
Condensation Nuclei ◽  
The Impact ◽  
Different Altitudes

Abstract. New particle formation (NPF) is thought to contribute half of the global cloud condensation nuclei. A better understanding of the NPF at different altitudes can help assess the impact of NPF on cloud formation and corresponding physical properties. However, NPF is not sufficiently understood in the upper mixing layer because previous studies mainly focused on ground-level measurements. In this study, the developments of aerosol size distribution at different altitudes are characterized based on the field measurement conducted in January 2019 in Beijing, China. We find that the partition of nucleation-mode particles in the upper mixing layer is larger than that at the ground, which implies that the nucleation processing is more likely to happen in the upper mixing layer than that at the ground. Results of the radiative transfer model show that the photolysis rates of the nitrogen dioxide and ozone increase with altitude within the mixing layer, which leads to a higher concentration of sulfuric acid in the upper mixing layer than that at the ground. Therefore, the nucleation processing in the upper mixing layer should be stronger than that at the ground, which is consistent with our measurement results. Our study emphasizes the influence of aerosol–radiation interaction on the NPF. These results have the potential to improve our understanding of the source of cloud condensation nuclei on a global scale due to the impacts of aerosol–radiation interaction.

Modeling Aerosol Impacts on Convective Storms in Different Environments

2010 ◽  
Vol 67 (12) ◽  
pp. 3904-3915 ◽  
Author(s):  
Rachel L. Storer ◽  
Susan C. van den Heever ◽  
Graeme L. Stephens
Keyword(s):  
Indirect Effects ◽  
Initial Conditions ◽  
Cloud Condensation Nuclei ◽  
Deep Convection ◽  
Atmospheric Modeling ◽  
Condensation Nuclei ◽  
Surface Precipitation ◽  
Convective Storms ◽  
Cloud Resolving Model ◽  
Regional Atmospheric Modeling

Abstract Aerosols are known to have both direct and indirect effects on clouds through their role as cloud condensation nuclei. This study examines the effects of differing aerosol concentrations on convective storms developing under different environments. The Regional Atmospheric Modeling System (RAMS), a cloud-resolving model with sophisticated microphysical and aerosol parameterization schemes, was used to achieve the goals of this study. A sounding that would produce deep convection was chosen and consistently modified to obtain a variety of CAPE values. Additionally, the model was initiated with varying concentrations of aerosols that were available to act as cloud condensation nuclei. Each model run produced long-lived convective storms with similar storm development, but they differed slightly based on the initial conditions. Runs with higher initial CAPE values produced the strongest storms overall, with stronger updrafts and larger amounts of accumulated surface precipitation. Simulations initiated with larger concentrations of aerosols developed similar storm structures but showed some distinctive dynamical and microphysical changes because of aerosol indirect effects. Many of the changes seen because of varying aerosol concentrations were of either the same order or larger magnitude than those brought about by changing the convective environment.

scholarly journals Moving toward Subkilometer Modeling Grid Spacings: Impacts on Atmospheric and Hydrological Simulations of Extreme Flash Flood–Inducing Storms

2017 ◽  
Vol 18 (1) ◽  
pp. 209-226 ◽  
Author(s):  
Nikolaos S. Bartsotas ◽  
Efthymios I. Nikolopoulos ◽  
Emmanouil N. Anagnostou ◽  
Stavros Solomos ◽  
George Kallos
Keyword(s):  
Flash Flood ◽  
Heavy Precipitation ◽  
Atmospheric Model ◽  
Hydrologic Model ◽  
Atmospheric Modeling ◽  
Limited Area ◽  
Complex Processes ◽  
The Alps ◽  
The Right ◽  
Regional Atmospheric Modeling

Abstract Flash floods develop over small spatiotemporal scales, an attribute that makes their predictability a particularly challenging task. The serious threat they pose for human lives, along with damage estimates that can exceed one billion U.S. dollars in some cases, urge toward more accurate forecasting. Recent advances in computational science combined with state-of-the-art atmospheric models allow atmospheric simulations at very fine (i.e., subkilometer) grid scales, an element that is deemed important for capturing the initiation and evolution of flash flood–triggering storms. This work provides some evidence on the relative gain that can be expected from the adoption of such subkilometer model grids. A necessary insight into the complex processes of these severe incidents is provided through the simulation of three flood-inducing heavy precipitation events in the Alps for a range of model grid scales (0.25, 1, and 4 km) with the Regional Atmospheric Modeling System–Integrated Community Limited Area Modeling System (RAMS–ICLAMS) atmospheric model. A distributed hydrologic model [Kinematic Local Excess Model (KLEM)] is forced with the various atmospheric simulation outputs to further evaluate the relative impact of atmospheric model resolution on the hydrologic prediction. The use of a finer grid is beneficial in most cases, yet there are events where the improvement is marginal. This underlines why the use of finer scales is a step in the right direction but not a solitary component of a successful flash flood–forecasting recipe.

scholarly journals Explicit calculation of indirect global warming potentials for halons using atmospheric models

2009 ◽  
Vol 9 (22) ◽  
pp. 8719-8733 ◽  
Author(s):  
D. Youn ◽  
K. O. Patten ◽  
J.-T. Lin ◽  
D. J. Wuebbles
Keyword(s):  
Global Warming ◽  
Ozone Depletion ◽  
Radiative Forcing ◽  
Radiative Transfer Model ◽  
Explicit Calculation ◽  
Transfer Model ◽  
Atmospheric Models ◽  
Pulse Emission ◽  
Cooling Effects ◽  
Global Warming Potentials

Abstract. The concept of Global Warming Potentials (GWPs) has been extensively used in policy consideration as a relative index for comparing the climate impact of an emitted greenhouse gas (GHG), relative to carbon dioxide with equal mass emissions. Ozone depletion due to emission of chlorinated or brominated halocarbons leads to cooling of the climate system in the opposite direction to the direct warming contribution by halocarbons as GHGs. This cooling is a key indirect effect of the halocarbons on climatic radiative forcing, which is accounted for by indirect GWPs. With respect to climate, it is critical to understand net influences considering direct warming and indirect cooling effects especially for Halons due to the greater ozone-depleting efficiency of bromine over chlorine. Until now, the indirect GWPs have been calculated using a parameterized approach based on the concept of Equivalent Effective Stratospheric Chlorine (EESC) and the observed ozone depletion over the last few decades. As a step towards obtaining indirect GWPs through a more robust approach, we use atmospheric models to explicitly calculate the indirect GWPs of Halon-1211 and Halon-1301 for a 100-year time horizon. State-of-the-art global chemistry-transport models (CTMs) were used as the computational tools to derive more realistic ozone depletion changes caused by an added pulse emission of the two major Halons at the surface. The radiative forcings on climate from the ozone changes have been calculated for indirect GWPs using an atmospheric radiative transfer model (RTM). The simulated temporal variations of global average total column Halons after a pulse perturbation follow an exponential decay with an e-folding time which is consistent with the expected chemical lifetimes of the Halons. Our calculated indirect GWPs for the two Halons are much smaller than those from past studies but are within a single standard deviation of WMO (2007) values and the direct GWP values derived agree with the published values. Our model-based assessment of the Halon indirect GWPs thus confirms the significant importance of indirect effects on climate.

scholarly journals Explicit calculation of indirect global warming potentials for halons using atmospheric models

2009 ◽  
Vol 9 (4) ◽  
pp. 15511-15540
Author(s):  
D. Youn ◽  
K. O. Patten ◽  
J.-T. Lin ◽  
D. J. Wuebbles
Keyword(s):  
Global Warming ◽  
Ozone Depletion ◽  
Radiative Forcing ◽  
Radiative Transfer Model ◽  
Explicit Calculation ◽  
Transfer Model ◽  
Atmospheric Models ◽  
Pulse Emission ◽  
Cooling Effects ◽  
Global Warming Potentials

Abstract. The concept of Global Warming Potentials (GWPs) has been extensively used in policy consideration as a relative index for comparing the climate impact of an emitted greenhouse gas (GHG), relative to carbon dioxide with equal mass emissions. Ozone depletion due to emission of chlorinated or brominated halocarbons leads to cooling of the climate system in the opposite direction to the direct warming contribution by halocarbons as GHGs. This cooling is a key indirect effect of the halocarbons on climatic radiative forcing, which is accounted for by indirect GWPs. With respect to climate, it is critical to understand net influences considering direct warming and indirect cooling effects for Halons. Until now, the indirect GWPs have been calculated using a para\\-meterized approach based on the concept of Equivalent Effective Stratospheric Chlorine (EESC) and the observed ozone depletion over the last few decades. As a step towards obtaining indirect GWPs through a more robust approach, we use atmospheric models to explicitly calculate the indirect GWPs of Halon-1211 and Halon-1301 for a 100-year time horizon. State-of-the-art global chemistry-transport models (CTMs) were used as the computational tools to derive more realistic ozone depletion changes caused by an added pulse emission of the two major Halons at the surface. The radiative forcings on climate from the ozone changes have been calculated for indirect GWPs using an atmospheric radiative transfer model (RTM). The simulated temporal variations of global average total column Halons after a pulse perturbation follow an exponential decay with an e-folding time which is consistent with the expected chemical lifetimes of the Halons. Our calculated indirect GWPs for the two Halons are smaller than past studies although direct GWPs agree with the published values. Nonetheless, our model-based assessment of the Halon indirect GWPs confirms the significant importance of indirect effects on climate.

A Method for Forecasting Cloud Condensation Nuclei Using Predictions of Aerosol Physical and Chemical Properties from WRF/Chem

2011 ◽  
Vol 50 (7) ◽  
pp. 1601-1615 ◽  
Author(s):  
Daniel Ward ◽  
William Cotton
Keyword(s):  
Hydrological Cycle ◽  
Spatial Scales ◽  
Cloud Condensation Nuclei ◽  
Cloud Microphysics ◽  
Atmospheric Modeling ◽  
Number Concentration ◽  
Integrated System ◽  
Condensation Nuclei ◽  
Field Campaign ◽  
Physical And Chemical

AbstractModel investigations of aerosol–cloud interactions across spatial scales are necessary to advance basic understanding of aerosol impacts on climate and the hydrological cycle. Yet these interactions are complex, involving numerous physical and chemical processes. Models capable of combining aerosol dynamics and chemistry with detailed cloud microphysics are recent developments. In this study, predictions of aerosol characteristics from the Weather Research and Forecasting Model with Chemistry (WRF/Chem) are integrated into the Regional Atmospheric Modeling System microphysics package to form the basis of a coupled model that is capable of predicting the evolution of atmospheric aerosols from gas-phase emissions to droplet activation. The new integrated system is evaluated against measurements of cloud condensation nuclei (CCN) from a land-based field campaign and an aircraft-based field campaign in Colorado. The model results show the ability to capture vertical variations in CCN number concentration within an anthropogenic pollution plume. In a remote continental location the model-forecast CCN number concentration exhibits a positive bias that is attributable in part to an overprediction of the aerosol hygroscopicity that results from an underprediction in the organic aerosol mass fraction. In general, the new system for predicting CCN from forecast aerosol fields improves on the existing scheme in which aerosol quantities were user prescribed.

scholarly journals Effects of Aerosols as Ice Nuclei on the Dynamics, Microphysics and Precipitation of Severe Storm Clouds

Atmosphere ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 783
Author(s):  
Huiling Yang ◽  
Hui Xiao ◽  
Chunwei Guo
Keyword(s):  
Northern China ◽  
Atmospheric Modeling ◽  
Cloud Droplets ◽  
Severe Storm ◽  
Mixing Ratios ◽  
Convective Clouds ◽  
Ice Nuclei ◽  
High Concentrations ◽  
Regional Atmospheric Modeling

The Regional Atmospheric Modeling System (RAMS) is used to investigate the effect of aerosols acting as ice nuclei (IN) on the formation and growth of hydrometeor particles as well as on the dynamics and precipitation of a severe storm in Northern China. The focus of this study is to determine how the overall dynamics and microphysical structure of deep convective clouds are influenced if IN concentrations are somehow altered in a storm environment that is otherwise unchanged. Ice mixing ratios tend to increase and liquid mixing ratios tend to decrease with increasing IN concentrations. High concentrations of IN reduce the mean hail diameter and hail particles with smaller diameters melt more easily, which leads to a decrease in ground hailfall and an increase in surface rainfall. Liquid water plays a more important role in the process of hail formation, while the role of ice particles in the process of hail formation decreases with higher IN concentrations. The role of small cloud droplets in the formation of raindrops is increased and the role of hail melting in the process of raindrops formation is weakened with enhanced IN concentrations. Both latent heat release and absorption significantly increase with increasing IN concentrations. Increasing the concentration of IN by an appropriate amount is beneficial for increasing the total water content and strengthening the updraft, leading to enhancement of a storm, but excessive IN concentrations will inhibit the development of a storm.

scholarly journals Radiative effects of desert dust on weather and regional climate

2013 ◽  
Vol 13 (1) ◽  
pp. 1327-1365 ◽  
Author(s):  
C. Spyrou ◽  
G. Kallos ◽  
C. Mitsakou ◽  
P. Athanasiadis ◽  
C. Kalogeri ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Regional Climate ◽  
Lower Troposphere ◽  
Integrated Approach ◽  
Dust Particles ◽  
Radiative Transfer Model ◽  
Limited Area ◽  
Transfer Model ◽  
Radiative Effects ◽  
Desert Dust

Abstract. Mineral dust aerosols exert a significant effect on both solar and terrestrial radiation. By absorbing and scattering the solar radiation aerosols reduce the amount of energy reaching the surface. In addition, aerosols enhance the greenhouse effect by absorbing and emitting outgoing longwave radiation. Desert dust forcing exhibits large regional and temporal variability due to its short lifetime and diverse optical properties, further complicating the quantification of the Direct Radiative Effect (DRE). The complexity of the links and feedbacks of dust on radiative transfer indicate the need of an integrated approach in order to examine these impacts. In order to examine these feedbacks, the SKIRON limited area model has been upgraded to include the RRTMG (Rapid Radiative Transfer Model – GCM) radiative transfer model that takes into consideration the aerosol radiative effects. It was run for a 6 yr period. Two sets of simulations were performed, one without the effects of dust and the other including the radiative feedback. The results were first evaluated using aerosol optical depth data to examine the capabilities of the system in describing the desert dust cycle. Then the aerosol feedback on radiative transfer has been quantified and the links between dust and radiation have been studied. The study has revealed a strong interaction between dust particles and solar and terrestrial radiation, with several implications on the energy budget of the atmosphere. A profound effect is the increased absorption (in the shortwave and longwave) in the lower troposphere and the induced modification of the atmospheric temperature profile. These feedbacks depend strongly on the spatial distribution of dust and have more profound effects where the number of particles is greater, such as near their source.

scholarly journals An integrated modeling study on the effects of mineral dust and sea salt particles on clouds and precipitation

2011 ◽  
Vol 11 (2) ◽  
pp. 873-892 ◽  
Author(s):  
S. Solomos ◽  
G. Kallos ◽  
J. Kushta ◽  
M. Astitha ◽  
C. Tremback ◽  
...  
Keyword(s):  
Early Stage ◽  
Eastern Mediterranean ◽  
Model Performance ◽  
Cloud Droplet ◽  
Atmospheric Modeling ◽  
Dust Particles ◽  
Limited Area ◽  
Cloud Development ◽  
Regional Atmospheric Modeling

Abstract. This report addresses the effects of pollution on the development of precipitation in clean ("pristine") and polluted ("hazy") environments in the Eastern Mediterranean by using the Integrated Community Limited Area Modeling System (ICLAMS) (an extended version of the Regional Atmospheric Modeling System, RAMS). The use of this model allows one to investigate the interactions of the aerosols with cloud development. The simulations show that the onset of precipitation in hazy clouds is delayed compared to pristine conditions. Adding small concentrations of GCCN to polluted clouds promotes early-stage rain. The addition of GCCN to pristine clouds has no effect on precipitation amounts. Topography was found to be more important for the distribution of precipitation than aerosol properties. Increasing by 15% the concentration of hygroscopic dust particles for a case study over the Eastern Mediterranean resulted in more vigorous convection and more intense updrafts. The clouds that were formed extended about three kilometers higher, delaying the initiation of precipitation by one hour. Prognostic treatment of the aerosol concentrations in the explicit cloud droplet nucleation scheme of the model, improved the model performance for the twenty-four hour accumulated precipitation. The spatial distribution and the amounts of precipitation were found to vary greatly between the different aerosol scenarios. These results indicate the large uncertainty that remains and the need for more accurate description of aerosol feedbacks in atmospheric models and climate change predictions.

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