Atmospheric Dynamics

NWP is an important topic for students of meteorology, oceanography, Atmospheric Physics etc. Without using mathematics or equations, here briefly described. This has come out of the lecture given to CSIR/UGC NET students who are competing for the fellowship which was organized by Lions club which was well appreciated by eminent meteorologists and oceanographers who attended this talk. Thus this will give an overall knowledge on NWP to any beginner particularly for B.Sc and M.Sc meteorology, oceanography, atmospheric science etc. students.

This work examines the life cycle of sudden stratospheric warmings (SSWs) from composites of a large number of events. The events are sampled from idealized general circulation model (GCM) integrations and form a database of several hundred major, displacement, splitting, and weak vortex events. It is shown that except for a few details, the generic zonal-mean evolution does not depend on the definition used to detect SSWs. In all cases, the composites show the stratosphere in a positive annular mode phase prior to the events and a barotropic response in the stratosphere at onset. There is a clear positive peak in upward Eliassen–Palm (EP) flux prior to the onset date in the stratosphere and a much weaker peak in the troposphere, making the evolution more consistent with the picture of the stratosphere acting as a variable filter of tropospheric EP flux, rather than SSWs being forced by a strong ''burst'' in the troposphere. When comparing composites of SSWs from the database with apparent influence at the surface (downward ''propagating'') to those without such influence, the only significant differences are a somewhat more barotropic response at the onset date and longer persistence in the lower stratosphere after the onset for propagating SSWs. There is no significant difference in EP flux between propagating and nonpropagating events, and none of the definitions considered here shows a particular skill in selecting propagating events.

We present a numerical model that reveals a mechanism governing the polar atmospheric dynamics of Jupiter, Saturn, Uranus and Neptune. Exploration of the polar regions of the gas giants has produced surprisingly diverse results, with Cassini finding a single, intense, compact polar cyclone precisely centered on each pole of Saturn, and Voyager data and ground-based observations suggesting Uranus and Neptune have dominant, single polar cyclones as well. The Juno spacecraft at Jupiter finds several tightly packed cyclones surrounding a central cyclone offset from the poles. These discoveries raise questions about the mechanism that differentiates these polar atmospheric dynamics regimes. To help determine what physical mechanisms control these differences, we use the Explicit Planetary Isentropic Coordinate (EPIC) model to carry out forced-turbulence shallow-water simulations in a gamma-plane configuration, i.e. a Cartesian grid with a pole placed at the center. The model is forced by small-scale stochastic mass pulses that parametrically represent cumulus storms. The effects of three parameters, the planetary Burger number, Bu = (Ld / a) 2 (Ld is the Rossby deformation radius, a is the planetary radius), input storm strength, s, and proportion of cyclonic and anticyclonic storms injected into the domain, α, are systematically investigated. Bu emerges to be the most important, able to distinguish between four distinct dynamical regimes, matching those of the giant planets, which from large to small Bu, are: i) a large cyclonic polar vortex (i.e., Uranus/Neptune-like), ii) a compact intense cyclonic polar vortex (Saturn-like), iii) two large vortices or one vortex offset from the pole (transitional), and iv) meandering jets with no centrally dominant vortex, or with multiple circumpolar cyclones (Jupiter-like). The boundaries of these regimes are found to be only slightly modulated by the values of s and α. By applying this correlation with respect to Bu in reverse, an observation of a particular polar regime could in principle be used to constrain Ld .

Abstract We present a numerical model that reveals a mechanism governing the polar atmospheric dynamics of Jupiter, Saturn, Uranus and Neptune. Exploration of the polar regions of the gas giants has produced surprisingly diverse results, with Cassini finding a single, intense, compact polar cyclone precisely centered on each pole of Saturn, and Voyager data and ground-based observations suggesting Uranus and Neptune have dominant, single polar cyclones as well. The Juno spacecraft at Jupiter finds several tightly packed cyclones surrounding a central cyclone offset from the poles. These discoveries raise questions about the mechanism that differentiates these polar atmospheric dynamics regimes. To help determine what physical mechanisms control these differences, we use the Explicit Planetary Isentropic Coordinate (EPIC) model to carry out forced-turbulence shallow-water simulations in a gamma-plane configuration, i.e. a Cartesian grid with a pole placed at the center. The model is forced by small-scale stochastic mass pulses that parametrically represent cumulus storms. The effects of three parameters, the planetary Burger number, Bu = (Ld / a)2 (Ld is the Rossby deformation radius, a is the planetary radius), input storm strength, s, and proportion of cyclonic and anticyclonic storms injected into the domain, α, are systematically investigated. Bu emerges to be the most important, able to distinguish between four distinct dynamical regimes, matching those of the giant planets, which from large to small Bu, are: i) a large cyclonic polar vortex (i.e., Uranus/Neptune-like), ii) a compact intense cyclonic polar vortex (Saturn-like), iii) two large vortices or one vortex offset from the pole (transitional), and iv) meandering jets with no centrally dominant vortex, or with multiple circumpolar cyclones (Jupiter-like). The boundaries of these regimes are found to be only slightly modulated by the values of s and α. By applying this correlation with respect to Bu in reverse, an observation of a particular polar regime could in principle be used to constrain Ld.

١٩٣ Global Climate Models (GCM) has been developed to perform climate projection to simulate and understand climate change in response to emission of greenhouse. The aim of this study is to use simple numerical climate models to investigate effect of various parameters, functions, and components of climate system on the temperature rise. Two climate changes scenarios used to estimate and explore the future rise surface air temperature over Iraq until 2050. The result of the surface air temperature of scenario A for July has been 31.6 C in the first decade (1961-1970), while the last decade of study has been more than 37 ºC, while scenario C less than scenario A 3.8 ºC for most cases. January's surface air temperature for last decade has been 10.0 ºC, while observation data is more than model by two times. Anomaly surface air temperature focused on the behavior of variable more than value of it, so that this study carried out the fluctuations of two scenarios have been close together for first five decades, while the difference appears in the last three decades for example for Baghdad city in winter the difference between two scenarios began form 2030 about 2 ºC. Summer surface air temperature for Baghdad city has been higher value than surrounding regions for both scenarios A and C to reach 2-3 ºC.

The dispersion of heavier-than-air aerosol clouds is of great relevance to the analysis and assessment of hazards in the chemical and petrochemical industries. There are many simple mathematical models for heavy gas dispersion but, in most cases, two-phase dynamics are either ignored or treated in a very simple way, without any convincing scientific justification. In fact almost all of those models which do treat two-phase phenomena rely on the “homogeneous equilibrium” assumption, whether they be for jet dispersion, for gravity dominated dispersion, or for any other aspect of a two-phase release.Here we test the homogeneous equilibrium model against a more sophisticated aerosol approach, in the context of two-phase ammonia clouds released in dry and moist air. It is shown that the simpler model does indeed provide a good description for some envisaged release situations, and guidance is given on where the homogeneous equilibrium model is not likely to be adequate. The homogeneous equilibrium model seems to be adequate for evaluating the dispersion of heavier-than-air clouds containing droplets smaller than 100 μm.

Atmospheric Surface layer (ASL) is the bottom most part of Atmospheric Boundary Layer (ABL) and is very close to the earth's surface, while ABL is that part of the atmosphere extending from the surface of the earth to a height of 1 to 2 km in which the effects of the earth's surface is felt. The ASL directly influences the daily activities of nearly all life on planet Earth extending up to an altitude of the order of 50-100 meters. The ABL studies gained importance because it is virtually controlling the human activity in the application of every branch of meteorology like air pollution, NWP, urban, agriculture, aviation and hydrometeorology. Particularly the stability of ASL decides the generation of weather systems like tornadoes, thunderstorms, cyclones and fronts. The heights of ASL and ABL are not constant. The heights vary with temperature and turbulence.

Analysis of the influence of condensation and related latent heat release upon developing barotropic and baroclinic instabilities of large-scale low Rossby number shielded vortices on the f - plane is performed within the moist-convective rotating shallow water model, in its barotropic (one-layer) and baroclinic (two-layer) versions. Numerical simulations with a high-resolution well-balanced finite-volume code, using a relaxation parameterisation for condensation, are made. Evolution of the instability in four different environments, with humidity (i) behaving as passive scalar, (ii) subject to condensation beyond a saturation threshold, (iii) subject to condensation and evaporation, with two different parameterisations of the latter, are inter-compared. The simulations are initialized with unstable modes determined from the detailed linear stability analysis in the "dry" version of the model. In a configuration corresponding to low-level mid-latitude atmospheric vortices,...

(In English) Lightning is appropriate to convective cloud such as Cumulonimbus that is formed by atmospheric instability. Humidity analysis is conducted to observe water vapor, streamline analysis to observe air mass orientation, relative vorticity to observe vertical movement, and (Convective Available Potential Energy) CAPE index analysis to observe the level of Cumulonimbus accreation potential. Furthermore, a comparison is made with lightning data that has been processed into a map of lightning distribution. The analysis results show an increase in Cumulonimbus cloud growth caused by energy derived from the vast supply of water vapor, the presence of convergence patterns, as well as strong vertical air movement. A comparison with the map of the lightning distribution shows the frequency of lightning increases as Cumulonimbus cloud increases during the rainy season and transitions.

(In Bahasa) Petir identik dengan adanya pertumbuhan awan konvektif berjenis Cumulonimbus yang dapat terbentuk oleh adanya ketidakstabilan dinamika atmosfer. Dilakukan analisis kelembapan udara untuk melihat konsentrasi uap air, analisis streamline untuk melihat pola angin, analisis vortisitas relatif untuk melihat gerak vertikal, serta analisis indeks CAPE (Convective Available Potential Energy) untuk melihat tingkat potensi pertumbuhan awan Cumulonimbus. Selanjutnya dilakukan perbandingan dengan data petir yang telah diolah menjadi peta sebaran petir. Hasil analisis menunjukkan peningkatan pertumbuhan awan Cumulonimbus disebabkan oleh energi yang berasal dari besarnya pasokan uap air, adanya pola konvergensi serta gerakan udara vertikal yang kuat. Perbandingan dengan peta sebaran petir menunjukkan frekuensi petir bertambah seiring meningkatnya pertumbuhan awan Cumulonimbus saat musim hujan dan transisi.

Kata kunci :cumulonimbus, kelembapan udara, petir, vortisitas.

Key Points: • A statistical approach explores the sudden warming predictability beyond the ten-day limit of dynamical forecasts • The approach utilizes upward wave activity and meridional potential vorticity gradient to determine conditional sudden warming probabilities • The conditional probabilities show significant information gain over climatology out to one season * Current address: Abstract This work explores dynamical arguments for statistical prediction of Stratospheric Sudden Warming events (SSWs). Based on climate model output, it focuses on two predictors: upward wave activity in the lower stratosphere and meridional potential vorticity (PV) gradient in the upper stratosphere, and detects large values of these predictors. Then it quantifies how many SSWs are preceded by predictor events, and, inversely, how many events are followed by SSWs. This allows to compute conditional probabilities of future SSW occurrence. It is found that upward wave activity leads to important increases in SSW probability within the following three weeks, but is less important thereafter. A weak PV gradient is associated with increased SSW probability at short lags and, perhaps more importantly, decreased SSW probability at long lags. Finally, when both predictors are considered in combination, the information gain is large on the weekly and small but significant on the intra-seasonal time scale.

Fenomena cuaca seperti cold surge, southerly surge, dan Borneo vortex dapat menjadi penyebab anomali musim hujan di Indonesia. Penelitian ini mengkaji dinamika atmosfer saat terjadinya cold surge, southerly surge, dan Borneo vortex di benua maritim Indonesia (BMI) bagian barat pada tanggal 9-15 Desember 2012 dengan memanfaatkan model weather research and forecasting (WRF). Data yang digunakan pada penelitian ini adalah final global data. Untuk verifikasi digunakan data angin, kelembapan relatif, curah hujan hasil observasi, serta data curah hujan global satellite mapping of precipitation (GSMaP). Metode yang digunakan adalah metode statistik dan deskriptif. Hasil penelitian menunjukkan bahwa model WRF mampu merespon kehadiran cold surge, southerly surge dan Borneo vortex dengan baik. Hal ini dibuktikan dengan nilai mean absolute error (MAE) pada kelembapan relatif, kecepatan angin, dan curah hujan yang secara umum masih di bawah nilai toleransi kesalahan. Namun, model WRF belum mamp...

The tracer-tracer correlation technique (TRAC) has been widely employed to infer chemical ozone loss from observations. Yet, its applicability to chemistry-climate model(CCM) data is disputed. Here, we report the successful application of TRAC on theresults of a CCM simulation. By comparing TRAC-calculated ozone loss to ozone lossderived with the passive ozone method in a chemistry transport model we differentiateeffects of internal mixing and cross vortex boundary mixing on a TRAC referencecorrelation. As a test case, we consider results of a cold Arctic winter/spring episode froman E39/C experiment, where typical features, for example, sufficient polar stratosphericcloud formation potential, denitrification and dehydration, and intermittent and finalstratospheric warming events, are simulated. We find that internal mixing does not impact the TRAC-derived reference correlation at all. Mixing across the vortex boundary wouldlead to an underestimation of ozone loss by 10% when calculated with TRAC. We provide arguments that TRAC is a consistent and conservative method to derive chemicalozone loss and can be used to extract its chemical signature also from CCM simulations. As a consequence, we will be able to provide a lower bound for chemical ozone loss for model simulations where a passive ozone tracer is not available

One of the most reliable methods for the prediction of odour impact from environmental facilities, strongly influenced by topography and local atmospheric dynamics, involves the use of atmospheric dispersion models.The present study focuses on the implementation of a dispersion model for the prediction of odour impact from a large and complex landfill system, localized in Borgo Montello (Latina), in the Lazio Region (Central Italy). The Calpuff dispersion model was selected for the simulations of odour impact, since it is well recognized as the preferred model for assessing the long range transport of pollutants. The odour emission rates, which are the inputs to the dispersion model, were defined on the basis of dynamic olfactometric analyses on air samples taken in the landfills areas. Different scenarios were simulated, with the aim of evaluating the odour impact caused by a project of landfill expansion through height raise. The environmental odour impacts were assessed through t...

The coupling of processes in the lower atmosphere to the ionosphere remains a complex and challenging problem. The ionosphere consists of several conductive layers that reflect radio waves, a characteristic which
is of interest problem for scientists and engineers, especially in the telecommunications industry. Disruption of the ground to satellite communication cause loss of lock on satellite signal driven by mechanism that involved the coupling process of lower atmosphere and ionosphere. This study investigate possibility effect of the
tropospheric mesoscale convective complexes (MCC) events on the F-region of the ionosphere over Indonesia.
The presence of meteorological systems like MCC over Indonesia are detected during 2007 to 2012 in several sites such as over Indian Ocean, Western Sumatera, Central and Eastern of Kalimantan and Central of
Sulawesi. Three types of ionospheric data, critical frequency of F2-layer (foF2) and virtual height of F-layer (h'F) from ionosonde, and also RTI plot of Field Aligned Irregularities from Equatorial Atmosphere Radar
data are analyzed during periods of geomagnetic storms and periods of without geomagnetic storms related to evolution of MCC generation. The results show the effect of the tropospheric MCC events on the F-region of ionosphere.

Observations reveal a poleward expansion of the tropics in recent decades, implying a potential role of human activity. However, although theory and modelling suggest increasing GHG concentrations should widen the tropics, previous observational-based studies depict disparate rates of expansion, including many that are far higher than those simulated by climate models. Here, we review the rates and possible causes of observed and projected tropical widening. By accounting for methodological differences, the tropics are found to have widened about 0.5° of latitude per decade since 1979. However, it is too early to detect robust anthropogenically induced widening imprints due to large internal variability. Future work should target the seasonal and regional signatures of forced widening, as well as the associated dynamical mechanisms.

The Moroccan Mediterranean coastline is located in the transition zone between the unstable mid-latitude circulation dominant in the winter season and the influence of high subtropical high pressures in the dry season. The topography of the coastline, marked by the Rifan mountains, contributes to the creation of a multitude of very different local climates. This zone experiences fluctuations in rainfall, marked by periods of drought or extreme rain events. The purpose of this study is to perform a spatio-temporal regionalization by a Principal Component Analysis with Varimax Rotation (ACPR) of the rainfall of the winter season in order to extract scores on which to analyze trends according to the test By Man Kendall. An explanation of these fluctuations will be given by the dominant modes of variability of Large Scale Atmospheric
Circulation (LSAC): the North Atlantic Oscillation (NAO) and the Western Mediterranean Oscillation (WeMO).

We show that the monthly recorded history (1866–2014) of the Southern Oscillation Index (SOI), a descriptor of the El Niño Southern Oscillation (ENSO) phenomenon, can be correctly described as a dynamic system supporting a potential nonlinear predictability well beyond the spring barrier. Long-term predictability is strongly connected to a detailed knowledge about the topology of the attractor obtained by embedding the SOI index in a wavelet base state space. By utilizing the state orbits on the attractor, we show that the information contained in the SOI is sufficient to provide nonlinear attractor information, allowing the detection of predictability for longer than a year: 2, 3, and 4 years in advance throughout the record with an acceptable error. This is possible due to the fact that the lower-frequency variability of the SOI presents long-term positive autocorrelation. Thus, by using complementary methods, we confirm that the reconstructed attractor of the low-frequency part (lower than 1/year) of SOI time series cannot be attributed to stochastic influences. Furthermore, we establish its multifractality. As an example of the capabilities of the methodology, we investigate a few specific El Niño (1972–1973, 1982–1983, 1997–1998) and La Niña (1973–1974, 1988–1989 and 2010–2011) events. Our results indicate that each of these present several equivalent temporal structures over other eras of these 149 years (1866–2014). Accordingly, none of these cases, including extreme events, presents temporal singularity. We conclude that the methodology’s simplicity of implementation and ease of use makes it suitable for studying nonlinear predictability in any area where observations are similar to those describing the ENSO phenomenon.

По материалам синоптических и спутниковых наблюдений средиземноморского бассейна за 1986-1987 гг. проанализированы 86 случаев зарождения и эволюции южных циклонов. Методом кластерного анализа проведено их районирование. Наибольшую вероятность выхода на южные регионы СССР имеют генуэзские, кипрские и малоазиатские циклоны. Приведены их основные количественные характеристики. Рассмотрены основные пути перемещения циклонов на Крым и Украину. Представлен ряд отличительных признаков облачности циклонов, позволяющих использовать их при составлении и уточнении прогнозов погоды на Крым и Украину.

Vertical profiles of wind velocity and air temperature from a SODAR-RASS derived dataset within an alpine valley of the New Zealand Southern Alps were analyzed. The data covered the month of September 2013, and Self-Organizing Maps (SOM), which is a data clustering approach based on an unsupervised machine-learning algorithm, is used to detect topological relationships between profiles. The results of the SOM were shown to reflect the physical processes within the valley boundary layer, by preserving valley boundary layer dynamics and its response to wind shear. By examining the temporal evolution of ridge-top wind speed and direction and SOM node transitions, the sensitivity of the valley boundary layer to ridge-top weather conditions was highlighted. The approach of using a composite variable (wind speed and potential temperature) with SOM was successful in revealing the coupling of dynamics and atmospheric stability. The results reveal the capabilities of SOM in analyzing large datasets of atmospheric boundary-layer measurements and elucidating the connectivity of ridge-top wind speeds and valley boundary layers.

One major issue in the accurate solution of advection-dominated problems by means of high-order methods is the ability of the solver to maintain monotonicity. This problem is critical for spectral elements, where Gibbs oscillations may pollute the solution. However, typical filter-based stabilization techniques used with spectral elements are not monotone. In this paper, residual-based stabilization methods originally derived for finite elements are constructed and applied to high-order spectral elements. In particular, we show that the use of the variational multiscale (VMS) method greatly improves the solution of the transport-diffusion equation by reducing over- and under-shoots, and can be therefore considered an alternative to filter-based schemes. We also combine these methods with discontinuity capturing schemes (DC) to suppress oscillations that may occur in proximity of boundaries or internal layers. Additional improvement in the solution is also obtained when a method that we call FOS (for First-Order Subcells) is used in combination with VMS and DC. In the regions where discontinuities occur, FOS subdivides a spectral element of order p into p2 subcells and then uses 1st-order basis functions and integration rules on every subcell of the element. The algorithms are assessed with the solution of classical steady and transient 1D, 2D, and pseudo-3D problems using spectral elements up to order 16.