The article considers the reasons for the underestimation of the wind speed by the WRF-ARW model when simulating downslope windstorms in the Russian Arctic. Simulation results for the Tiksi windstorm, for which sensitivity tests were carried out, appeared to be weakly dependent on the initial and boundary conditions, topography resolution, and boundary layer parameterization. Wind speed underestimation

The sensitivity of different atmospheric forcing on the simulation of Sea Surface Temperature (SST) in the Indian Ocean is examined using Regional Ocean Modeling System (ROMS). Model simulations using three different atmospheric forcings from the National Centers for Environmental Prediction (NCEP; 2.5 deg), National Centre for Medium Range Weather Forecasting (NCMRWF; 0.25 deg) and TropFlux (0.5 deg)

Inspired by the Charney-and-de Vore hypothesis, Hansen and Sutera in 1986 came forward with the claim of having detected a fingerprint of the presence of two preferred state in the tropospheric circulation at northern Hemisphere mid-latitudes. Shortly after, Nitsche et al. found that this claim was premature, since it may be caused by a insufficient data base. Now, with much more data, both from reanalyses

The impact of applying three-dimensional variational data assimilation (3D-Var DA) on convective-scale forecasts is investigated by using two mesoscale models, the Weather Research and Forecasting model (WRF-ARW) and the Hirlam and Aladin Research Model On Non-hydrostatic-forecast Inside Europe (HARMONIE-AROME). One month (1 to 30 December 2013) of numerical experiments were conducted with these two

The work identified the monsoon intraseasonal oscillation (MISO) from the observed met-ocean parameters from the moored buoys and satellite datasets during June 2013 – September 2013. The 30–60 days bandpass filtered winds, sea surface temperature (SST), and rainfall from both the satellites and moored buoys have indicated the existence of active and break phases of MISOs with a periodicity of 10–12

In the northern Bay of Bengal, mechanisms of seasonal sea-level variation have not previously been examined, and the understanding of longer-term inter-annual sea-level variation is also not concrete. These parameters are addressed in this study utilizing available tide gauge and satellite altimetry data. The contribution of steric sea level to seasonal and longer-term inter-annual sea-level variations

Record-breaking extreme temperatures have been measured in the last two decades all over Turkey, with recent studies detecting positive trends in extreme temperature time series. In this study, nonstationary extreme value analysis was performed on extreme temperature time series obtained from fifty stations scattered over the seven geographical regions of Turkey. Basic characterization of the data

A shallow-water model with horizontally nonuniform density is used to study the dynamics of jet flows that arise under the influence of buoyancy and the Coriolis force. Within this approach, the jet is described by a self-similar compactly-localized solution and interpreted as a band of shear flow having a temperature contrast with the ambient fluid. In addition to stationary states, the dynamics of

The problem of determining the absolute velocity of marine currents, including its barotropic component, is revisited. A generalization of the classical Needler’s formula is discussed for a Boussinesq fluid and it is shown that the steady flow solution can be deduced from a variational principle that uses the constants of motion existing in the problem. A simple model of a steady flow is considered

The year 2019 experienced an excess monsoon season over the Indian region, with the seasonal rainfall being 110 % of the long period average (LPA). Several zones across the country suffered multiple extreme rainfall events and flood situations resulting in a massive loss of life and property. The first half of 2019 experienced a moderate El Niño Modoki event that lasted till mid-summer. Another important

Southwestern Indian state, Kerala experienced extreme devastating statewide flood event of the century during 2018 monsoon season. In this study, an attempt has been made to bring out the salient dynamical factors contributed to the Kerala flood. There were 3 active spells over Kerala during 2018 Monsoon season. All the three spells were accustomed with the intrinsic factors of low frequency components

Geometric features in oceanic mesoscale eddies such as tilt and anisotropy can influence the properties of the Reynolds stress that provides feedback between the eddies and the background flow. By regarding an eddy as a wave, previous studies have parameterized the Reynolds stress based on the equivalence in the tilt angle between the phase of the eddy stream functions and the variance ellipse for

Long-lead precipitation forecasts for 1–4 seasons ahead are usually difficult in dynamical climate models due to the model deficiencies and the limited persistence of initial signals. But, these forecasts could be empirically improved by statistical approaches. In this study, to improve the seasonal precipitation forecast over the southern China (SC), the statistical downscaling (SD) models are built

This paper presents an analysis of December to February (DJF) season wet and dry events and their associated circulation anomalies during the period of 1978–2010 over Malawi. The study was conducted using meteorological daily observed rainfall datasets during the entire study period. A set of regional wet and dry indices with a scheme of classifying their severity was employed to classify the wet and

Based on the in-situ subsurface thermal and salinity measurements from the Ocean Moored buoy network for Northern Indian Ocean (OMNI) during the Super Cyclone Amphan in the Bay of Bengal during 14–18 May 2020, we have identified that the ocean-atmosphere interaction is limited to 80 m, the depth of the pycnocline. Using the OAEE-TS algorithm and dynamic changes in the sea subsurface temperature, salinity

El Niño is a phenomenon of the catastrophic increase of surface temperature in the eastern part of the Pacific Ocean. It has a significant impact to weather of the American continent and western regions of the tropical Pacific, as well as on the weather and climate of entirely the Earth. Most important factors influencing El Niño are the wind, ocean currents and slope of the water surface (and temperature

The southwestern coast of the Caspian Sea often experiences heavy snowfall during winter season due to the lake effect. The accurate estimation of snowfall in this region is still a challenge for weather forecasters. This study attempts to investigate the simulation of lake-effect snow (LES) event occurring along the southwest coastline of the Caspian Sea from 31 January to 4 February 2014 using Weather

The turbulent motions in ocean interact in a broad continuous range of the spatial scales. To study the quantitative structures at multiple spatial scales in oceanic dynamics, the multi-level dissipation element (ML-DE) analysis is proposed. Considering a sea surface temperature (SST) field θ(x,y,t), from any spatial point, one can inevitably reach a local maximum temperature point and a local minimum

Climate modeling studies in the context of Indian summer monsoon (ISM) variability have usually been performed on the seasonal and interannual timescales. The present study assesses the fidelity of the Regional Climate Model (RegCM v4.6) in capturing the subseasonal active and break spells along with the seasonal mean rainfall during the ISM season. The model fields are obtained from 24 years (1982–2005)

In this paper, we propose a numerical framework to study the shapes, dynamics and the stabilities of the self-localized solutions of the nonlinear wave blocking problem. With this motivation, we use the nonlinear Schrodinger equation (NLSE) derived by Smith as a model for the nonlinear wave blocking. We propose a spectral renormalization method (SRM) to find the self-localized solitons of this model

Abstract The formation of cyclones over the sea surface is driven by air-sea interaction with feedbacks on wave generation, thermohaline structures, and biochemical properties of upper-ocean layers. In the Mediterranean basin, strong cyclonic systems having tropical-like characteristics are called “medicanes”. The consequences of such events are usually assessed over the land, however, hydrographic

Abstract Present work elucidates the impact of 3DVAR data assimilation technique for the simulation of one of the heavy rainfall events reported over Kotdwara region in the North-West Himalayan (NWH) region on 4th August 2017. We have examined the impact of conventional and satellite-based radiance datasets on the simulated results with and without assimilating the observations into the Weather Research

Abstract Latent Heat Flux (LHF) and Sensible Heat Flux (SHF) are the two important parameters in air-sea interactions and hence have significant implications for any coupled ocean-atmospheric model. These two fluxes are conventionally computed from met-ocean parameters using bulk aerodynamic formulations; or the Coupled Ocean Atmosphere Response Experiment (COARE) bulk flux algorithms. Here COARE 3

In this study, the dynamics of track deflection associated with Tropical Cyclone (TC) Sidr (2007) are explored using a numerical weather prediction model. It is found that (a) the simulated track of Sidr is sensitive to flow, orographic, and model vertical structure that change the environmental steering flow leading to the track deflection. In particular, the track of TC Sidr is deflected northwestward

Tropical easterly waves are common features in the trade wind zones and they are important sources of tropical cyclogenesis. Despite numerous studies have analyzed the genesis and maintenance of easterly waves in the Western North Pacific, few had examined their dissipation processes. Focusing on tropical easterly waves during May-September of 1979–2017, this study shows that most of the easterly waves

Satellite observations have long revealed to us a spatially growing Kuroshio Extension (KEx), but its underlying dynamics is yet to be studied. With a normal mode model of absolute/convective instability, it is found that the mean zonal jet is unstable at all the sections in the downstream region (east of 154 °E). In each of the resulting complex dispersion relation diagrams there lies a single saddle

The monsoon reversal winds in different seasons and high influx of freshwater from various rivers make the Bay of Bengal (BoB) a unique region. Thus, the knowledge of the dynamics of the mixed layer over this region is very important to assess the climatic variation of the Indian subcontinent. A comprehensive study of the role of external forcing on the seasonal and interannual mixed layer depth (MLD)

This study evaluates the dependence of simulated surface air temperatures on model resolution and orography for the mid-Holocene. Sensitivity experiments with the atmospheric general circulation model ECHAM5 are performed with low (∼3.75°, 19 vertical levels) and high (∼1.1°, 31 vertical levels) resolution. Results are compared to the respective preindustrial runs. It is found that the large-scale

The onset and advance of southwest monsoon are accompanied by the appearance of the offshore trough along the southwest coast of India. This offshore trough escorts a deluge of rainfall to the southwest coast, and sometimes rainfall band moves eastward further into south India. These broad observations were noticed during the summer monsoon of June 2017. Meteorological agencies and media had reported

The synoptic and dynamic aspects of heavy rainfall occurred on 5th May 2017 and caused flash flooding in arid and semi-arid central-northern Iran is analyzed by the Weather Research and Forecasting (WRF) model. This system synoptically is attributed to a surface low-pressure centered over southern Iran extended to the central parts, linking to a mid-tropospheric tilted-trough over western Iran, and

The aerodynamic drag coefficient (CD) is conjectured to change (or remains almost uniform) with the horizontal wind speed (U) over a flexible (or fixed) surface element, which is represented with the surface roughness (z0). This conjecture is tested for the near neutral atmospheric turbulence (i.e. when surface stability z/L is almost equal to 0, where z is the measurement height and L is Obukhov length)

In this research the dynamic downscaling method by Regional Climate Model (RegCM4.5) was used to assess the performance and sensitivity of seasonal simulated North and West of Iran (NI&WI) climate factors to different convection schemes, and transforms the large-scale simulated climate variables into land surface states over the North of Iran (NI) and West of Iran (WI). A 30-year (1986–2015) numerical

Tropical cyclone (TC) rainfall asymmetry is often influenced by vertical wind shear and storm motion. This study examined the effects of environmental vertical wind shear (200-850 hPa) and storm motion on TC rainfall asymmetry over the North Indian Ocean (NIO): the Bay of Bengal (BoB) and the Arabian Sea (AS). Four TC groups were used in this study: Cyclonic Storm (CS), Severe Cyclonic Storm (SCS)

The study proposes an enhanced method of computing wind drag coefficient (Cd) for extreme hurricane wind conditions which can be applied to precisely estimate the hurricane induced storm wave and surge. Thirty different tropical cyclone/hurricane conditions were chosen and modeled using the enhanced Wave Boundary Layer Model (WBLM) to estimate Cd based on air-sea interaction concept and are then subjected

In this research, tropopause temperature (TT) and tropopause geopotential height (TGH) over the inner-core and environmental regions of all tropical cyclones (TCs) over the northwest of the Indian Ocean (NWIO) from 1990 to 2019 were investigated. To this aim, observational/analysis/reanalysis data and also simulated data from both historical and Representative Concentration Pathway 8.5 (RCP8.5) experiments

Anthropogenic aerosols (AA) have significantly caused anomalous winter mean atmospheric circulation over the Northern Hemisphere, but the main daily patterns of winter large-scale circulation change are not well understood. Here a self-organizing map analysis is applied to identify the leading patterns in AA-induced winter daily geopotential height (Z) anomaly fields simulated by three atmospheric

Dust storm, which has a significant impact on regional air quality, is one of the most hazardous meteorological phenomena in the arid areas. Yazd province is one of the arid areas in Iran that is exposed to dust storms. In this study, two cases of dust storms of Yazd province are studied with the use of coupling numerical models and aerosol optical depth (AOD) from MODIS data. We investigated synoptic

In this study, a long-term comparative assessment of the potential of wave power in the Black Sea was conducted using the calibrated and validated SWAN (Simulating WAves Nearshore) model forced by two well-known wind fields. The European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim and National Centers for Environmental Prediction/Climate Forecast System Reanalysis (NCEP/CFSR) wind

Analytical solution for two-dimensional thermal plume updraft velocity is obtained under the assumption of a uniform temperature excess inside the plume. In this way, the thermal plume motion is modeled in both mixed layer and entrainment zone. Also, a semi-analytical solution is obtained using an empirical model for the plume temperature excess in the mixed layer. In addition, an analytical model

The occurrence of extreme precipitation events is now a serious concern in recent years in Japan. This study explores the atmospheric driving mechanisms of two extreme precipitation events occurred during 5–6 July 2017 and 5–8 July 2018 over western Japan. We identified that the atmospheric transport of large amounts of moisture and wind streams with wind speed of minimum 15 m s−1 from south of Japan

Abstract We investigate the structure of surface lateral mixing in the Lofoten area in the Norwegian Sea using surface velocity field derived from a 1/12o reanalysis data. We compute a Lagrangian diagnostic based on the evolution of Finite Time Lyapanov Exponents (FTLEs) by advecting (backward in time) a large number of particles to quantify the hidden skeleton of different dynamical regions in the

Abstract Deep convection is one of the key components of the Atlantic Meridional Overturning Circulation. The intensity of deep convection (DC) is traditionally estimated as the maximum mixed layer depth (MMLD). In this study, we developed a criterion of the minimum number of casts needed for obtaining the MMLD in the Greenland Sea with a pre-defined accuracy. The criterion depends on convection intensity

Abstract Simulations of a mesoscale convective system (MCS), which propagated across northern India on 2nd May 2018 - leading to many fatalities when the gust front knocked down homes and tore apart building roofs - have been performed using the National Centre for Medium Range Weather Forecasting (NCMRWF) Unified Model – Regional (4 km horizontal grid spacing), to evaluate the model’s convective treatments

Abstract Cambodia is one of the most vulnerable countries to climate change impacts such as floods and droughts. Study of future climate change and drought conditions in the upper Siem Reap River catchment is vital because this river plays a crucial role in maintaining the Angkor Temple Complex and livelihood of the local population since 12th century. The resolution of climate data from Global Circulation

Abstract The long-term variations of wave characteristics in the Black Sea are evaluated by using a third-generation wave model (Simulating WAves Nearshore, SWAN), forced by the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim and National Centers for Environmental Prediction/Climate Forecast System Reanalysis (NCEP/CFSR) wind data, covering the period of 1979-2018. The model

Abstract Fronts are ubiquitous dynamic processes in the ocean, which play a significant role in the ocean dynamical and ecological environments. In this paper strong temperature fronts are investigated on the shelf of the Northern South China Sea using high resolution satellite data. These fronts have large horizontal gradients exceeding 1 °C km−1 with spatial scales around several kilometers. The

Abstract The validity of a spectral cumulus parameterization (spectral scheme) for simulating a diurnal cycle of precipitation over the Maritime Continent (MC) was examined using a regional atmospheric model. The impacts of entrainment parameterization and each type of convective closure, i.e., non-equilibrium (or equilibrium) closure for deep convection, mid-level, and shallow convective closures

Triadic resonance is one mechanism via which internal waves dissipate their energy, often at locations away from their generation sites. In this paper, we perform a combined theoretical and numerical study of triadic resonance in internal wave modes in a finite-depth ocean with background rotation and an arbitrary stratification profile. The spatial evolution of the modal amplitudes within a resonant

Abstract The Barents Sea is the most productive sea in the Arctic. The main causes of phytoplankton spring blooms are studied for a decadal time period of 2003–2013 at the region of (70 °N-80 °N, 30 °E-40 °E) in Barents Sea. Due to the rapidly ice melt in the southern region (70 °N-75 °N), almost no ice left after year 2005, sea surface temperature (SST) and wind speed (WIND) are two main dominant

Abstract In depth examination of the extreme precipitation over Kerala during 15–17th August 2018 – triggering major flood episode in the peninsular Indian state - have been made via the National Centre for Medium Range Weather Forecasting (NCMRWF) Unified Model. A rare alignment of an intense low pressure area (LPA) over head Bay of Bengal (BoB) and a couple of typhoons over South China Sea and West

Abstract Observational studies and cloud resolving numerical simulations have shown that developing tropical cyclones often have markedly asymmetric distributions of moist convection. The present study uses a shallow-water model on the f-plane to gain further insight into the variety of vortex intensification pathways that may exist under such conditions. The diabatic forcing associated with asymmetric

Abstract The interaction mechanisms between the lower part of the atmosphere and the ocean surface comprise of a complicated issue with many parameters to be studied. Heat, moisture and momentum exchanges in the air-sea system exert a significant role on both lower atmosphere and sea state conditions. Working towards the understanding of how wave characteristics link the atmosphere with the ocean,

Abstract It is well known that the primitive equations (the atmospheric equations of motion under the additional assumption of hydrostatic equilibrium for large scale motions) are ill posed when used in a limited area on the globe. Yet the atmospheric equations of motion for large scale motions are essentially a hyperbolic system that with appropriate boundary conditions should lead to a well posed

Abstract The present work extensively describes the tropical dynamical changes during the Vortex split Major Stratospheric Warming (V-MSW) event occurred in recent decades. For better visualization of high latitude influence of tropical atmosphere, in this study, we have utilized three successive major vortex split warming events occurred in winters 1984/85, 1988/89 and 2008/09. The realistic visualization

Abstract A 1D model, including a time variation of eddy viscosity and mixed layer depth, is applied to study Ekman spirals. It simulates a weak velocity in the atmosphere but a jet in the upper oceanic mixed layer during daytime; and a strong velocity in the atmosphere but a weak, uniform velocity in the ocean at night. The mean spirals in both atmosphere and ocean are close to the average spirals

Abstract At least two main oceanic fronts (the subarctic and subtropical fronts) exist in the North Pacific. Especially in the subtropical frontal zone (STFZ), the sea subsurface temperature gradient is significantly larger than that of the surface layer in winter. Subseasonal interaction between the subsurface subtropical front and overlaying atmosphere is revealed by using empirical orthogonal function

Abstract In this study, long-term change of wind characteristics on the Black Sea has been investigated using two widely used data sources, i.e., European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim and National Centers for Environmental Prediction/Climate Forecast System Reanalysis (NCEP/CFSR), spanning 40 years between 1979 and 2018. Spatial and seasonal variability of climatic

Abstract By analyzing NCEP-NCAR reanalysis daily data for 1979–2016, the modulation by Madden-Julian Oscillation (MJO) of the wintertime surface air temperature (SAT) over high latitude is examined. The real-time multivariate MJO (RMM) index, which divides the MJO into eight phases, is used. It is found that a significantly negative SAT anomaly over the northern high latitude region of (180°–60 °W