Dynamics of Atmospheres and Oceans最新文献

英文中文

Quasi-homogeneous regions of climatic distributions of wind wave parameters in the Black Sea

IF 1.9 4区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Dynamics of Atmospheres and Oceans

Pub Date : 2025-01-20 DOI: 10.1016/j.dynatmoce.2025.101535

Boris V. Divinsky, Yana V. Saprykina

The main aim of the study is to identify in the Black Sea quasi-homogeneous spatial areas and corresponding relevant features, the climatic statistical characteristics of which will determine these areas. Numerical modeling and discriminant analysis were applied. As a result of modeling an array of wind wave parameters for the period of 45 years (1979–2023) was obtained. The values of the main parameters (significant wave heights, spectrum peak periods, propagation directions) for this period at 92 points uniformly distributed over the Black Sea were analyzed. The main features, by which the zoning of the Black Sea was carried out, were climatic repeatabilities of the following parameters: significant wave heights in the ranges of h_s< 1 m, 1 <h_s< 3 m, 3 <h_s< 5 m, h_s> 5 m; and spectrum peak periods in the ranges t_p< 3 s, 3 <t_p< 6 s, 6 <t_p< 9 s, t_p> 9 s. According discriminant analysis six quasi-homogeneous areas (clusters) in the Black Sea were identified. The main zoning parameters are wave heights in the ranges 3 <h_s< 5 m and h_s> 5 m and periods 6 <t_p< 9 s. The identified clusters are quite homogeneous in the repeatability of wave action of the north-eastern and north-western directions. The obtained quasi-homogeneous areas of the Black Sea significantly refine the zoning obtained earlier and can be used to study and forecast sea climate change.

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引用次数: 0

A 2D numerical study on Kuroshio currents with free slip coastal boundary

IF 1.9 4区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Dynamics of Atmospheres and Oceans

Pub Date : 2024-12-30 DOI: 10.1016/j.dynatmoce.2024.101524

Sudhakar Matle

The paper presents a comprehensive analysis of generating a Kuroshio current-like phenomenon using a novel mathematical model and advanced numerical methods. It helps to understand the streamline behavior on the western boundary over the time scales due to the presence of free slip conditions at the north and at the south coastal boundaries.

The ocean is modeled as a square domain occupied by homogeneous, incompressible fluid of constant density and a variable surface height. Dynamics of the flow are examined in a shallow water system. The salient parameters investigated here are the wind stress coefficient, the stochastic wind force coefficient, and time scales.

It is proved that streamlines are crowded on the western boundary through numerical study, and also these are bifurcated when the wind stress coefficient is 3.12. The bifurcation of the flow indicates the stability. It is also reported that the Milstein method and a standard numerical method are in good agreement while the Fokker–Planck equation-based method and the Milstein method are partially agreed. The solution by the Milstein method diverged while the solution by the Fokker–Planck method converged when

ω \geq 0.2

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引用次数: 0

A comparative study of the sensitivity of an ocean model outputs to atmospheric forcing: ERA-Interim vs. ERA5 for Adriatic Sea Ocean modelling

IF 1.9 4区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Dynamics of Atmospheres and Oceans

Pub Date : 2024-12-27 DOI: 10.1016/j.dynatmoce.2024.101525

Javad Babagolimatikolaei

Advancements in atmospheric data have the potential to improve the accuracy of ocean modeling, as these models rely heavily on atmospheric parameters as key forcing inputs. One such dataset is the ECMWF reanalysis, with ERA5 being the latest version, succeeding ERA-Interim (ERA-I or ERAI). However, limited research has explored whether ERA5 improves ocean model accuracy compared to ERA-I. We use the ROMS model on the Adriatic Sea under two atmospheric forcing scenarios: ERA-I and ERA5. Results show that ERA5 calculates higher temperature and salinity values than ERA-I. ERA5 shows better alignment with satellite and Mediterranean reanalysis data than ERA-I. For temperature, ERA5 has a higher bias range (–2.29℃ to 0.83℃) compared to ERA-I (–2.34℃ to 0.80℃) and achieves a lower minimum bias, particularly in summer (0.02℃). Against Mediterranean reanalysis data, ERA5’s temperature bias range (–2.06℃ to 1.54℃) is lower range than ERA-I’s (–3.14℃ to 1.51℃). For salinity, ERA5 also has a smaller bias range (–0.02 PSU to 0.27 PSU) and achieves zero bias in spring, indicating a more accurate seasonal alignment than ERA-I. The warmer water temperatures in ERA5 are attributed to higher values of atmospheric parameters such as shortwave radiation flux, sensible heat flux, and air temperature, while, increased salinity is linked to more negative latent heat flux up to 10 W/m², longwave radiation up to 5 W/m², and higher wind speeds. These factors collectively lead to improved ocean modeling performance in ERA5.

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引用次数: 0

On baroclinic instability of curved fronts

IF 1.9 4区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Dynamics of Atmospheres and Oceans

Pub Date : 2024-12-23 DOI: 10.1016/j.dynatmoce.2024.101523

Suraj Singh , Christian E. Buckingham , Amit Tandon

Baroclinic instability has traditionally been examined using a model of a straight front in approximate geostrophic and hydrostatic balance. However, mesoscale curved fronts and eddies are ubiquitous in the oceans and their curvature may have an impact on baroclinic instability. In this study, we present modifications of the classical Eady and Charney problems, introducing a small amount of curvature in the small-Rossby, large-Richardson number limit. Employing quasi-geostrophic scalings for a predominantly zonal flow in cylindrical polar coordinates, we derive the governing equation of perturbation pressure in the presence of small curvature, treating this quantity as a deviation from a straight front. We find the importance of curvature principally arises through the potential vorticity (PV) gradient. Consequently, although curvature enters the Eady model via an introduction of so-called Green modes, the introduction of curvature does not modify the most unstable mode. In Charney’s model, however, the curvature of the flow introduces a depth scale that governs the vertical extent of the unstable modes and whose importance often presides over planetary beta. We find that introducing cyclonic curvature in Charney’s model increases the horizontal wavelength of the most unstable mode. We also report that curvature modifies the vertical buoyancy flux by extending the vertical scale of the most unstable mode. The possible consequences of these results are discussed. Since our present-day understanding of baroclinic instability assumes centrifugal forces in the mean state to be zero and since this undergirds existing eddy parameterizations, this study (1) offers a new interpretation of at least some of the observed vortices in the ocean and (2) suggests a weakly-curved Charney model might inform future sub-grid-scale parameterizations of baroclinic instability of curved fronts in the oceans.

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引用次数: 0

Simulation study of reservoir water environment based on Mike21-taking Baisha reservoir as an example

IF 1.9 4区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Dynamics of Atmospheres and Oceans

Pub Date : 2024-12-11 DOI: 10.1016/j.dynatmoce.2024.101522

Shaolei Guo , Yuehan Zhang , Xianqi Zhang , Yang Yang , Wanhui Cheng

This study aims to simulate the reservoir area by constructing a coupled model to analyze the variations in the water flow field and the migration patterns of pollutants in the Baisha Reservoir under different flow increments. One of the key challenges in this process is selecting an appropriate model and calibrating its parameters. The MIKE21 hydrodynamic-water quality coupled model was employed to simulate the reservoir area, with extensive experimental calibration of the HD and Ecolab models' parameters based on the actual conditions of Baisha Reservoir. The performance of the models was evaluated, and the results indicated a high level of reliability. In the Ecolab model, three commonly used water quality indicators—BOD, NH₃-N, and NO₃—were considered for simulation and analysis. To examine the changes in the water flow field under different flow increments, three distinct flow increment scenarios were tested. The results showed that the best simulation performance occurred when the flow increment was 30 %, with BOD improvement of 51.02 %, NH₃-N improvement of 26.31 %, and NO₃ improvement of 37.13 %. Furthermore, an ESN model was developed to predict future water quality changes in Baisha Reservoir. The accuracy of the ESN model was validated using the water quality simulation results from Scenario 3, yielding an average relative error of 3.26 %. The water quality concentrations predicted under this scenario were significantly lower than the initial concentrations, providing practical insights into addressing issues related to water quantity and quality in the reservoir.

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引用次数: 0

Long-term variability of the low-level clouds across Indo-Gangetic Plain

IF 1.9 4区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Dynamics of Atmospheres and Oceans

Pub Date : 2024-12-06 DOI: 10.1016/j.dynatmoce.2024.101521

Krishna Kumar Shukla , Gajendra Kumar , Chander Singh Tomar , Raju Attada , Kondapalli Niranjan Kumar , Anoop Kumar Mishra

This study examines the long-term variability (1980–2022) of low-level clouds and their base heights using cloud observations from India Meteorological Department (IMD) over the Indo-Gangetic Plain (IGP) crucial for aviation. For this purpose, synoptic cloud observation data, coded as per World Meteorological Organisation (WMO) standards, were collected every three hours from four weather stations of IMD namely Amritsar, Delhi, Lucknow, and Patna. Highest prevalence of cloud types namely Stratus (St), Stratocumulus (Sc), Cumulus (Cu), and Cumulonimbus (Cb) was observed during monsoon than pre-monsoon. We have reported the occurrence of Cb clouds during monsoon in the range of 20–50 %. Sc clouds show diurnal variation, peaking at 00, 03 UTC, and 15, 18, and 21 UTC. Cu and Cb clouds exhibit maxima in the afternoon during pre-monsoon and monsoon seasons, possibly due to the diurnal cycle of the atmospheric boundary layer height variations. Monsoon cases surpass pre-monsoon at all IGP sites. Notably, Cb with CBH 600–1000 m causes maximum rainfall during monsoon, and predominant Cb base heights are 600–1000 m, 1000–1500 m, and 1500–2000m across decades.

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引用次数: 0

The regional coupled ocean-atmosphere model simulation over Eastern Tropical Africa

IF 1.9 4区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Dynamics of Atmospheres and Oceans

Pub Date : 2024-12-05 DOI: 10.1016/j.dynatmoce.2024.101520

Vasubandhu Misra , C.B. Jayasankar

In this study we examine a 25-year simulation of a Regional Coupled Ocean-Atmosphere Model (RCOM) forced by global atmospheric and ocean reanalysis at the lateral boundaries over eastern equatorial Africa which includes parts of the Great Horn of Africa (GHA). It is a first of its kind use of a RCOM for the region. The model shows several observed features of the regional climate with bimodal peaks in the seasonal cycle interspersed with regions of unimodal peak, significant diurnal and intra-seasonal variations of precipitation especially over Lake Victoria and robust seasonal cycle of the upper western India Ocean. Nonetheless the model shows significant dry bias of seasonal precipitation that is persistent throughout the year, which is also reflected at diurnal and intra-seasonal scales. The mixed layer and thermocline depths are found to be shallower in the model simulation suggesting a far more stratified upper western Indian Ocean than the observations indicate.

引用次数: 0

Uncertainty reduction in ENSO periodicity projection based on the Wyrtki index

IF 1.9 4区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Dynamics of Atmospheres and Oceans

Pub Date : 2024-12-01 DOI: 10.1016/j.dynatmoce.2024.101516

Ximei Zhao , Bo Lu

Using the Wyrtki index, which comprehensively characterizes the dynamics of ENSO, we evaluated the fitting performance of 24 CMIP6 models for the ENSO dynamic processes during the period from 1980 to 2014. We identified the high-skill (HS) models with better simulation capabilities and the low-skill (LS) models with poorer simulation abilities. Compared to observational and reanalysis data, the HS models better simulate the average state of the tropical Pacific and the associated dynamic processes of ENSO from 1980 to 2014. In contrast, the LS models show a colder equatorial cold tongue, a steeper thermocline slope, and stronger trade winds in the central and western Pacific. The zonal advection feedback in the LS models is weaker, while the thermocline feedback is stronger, which may contribute to the deviations observed in the LS models when simulating the historical ENSO periodicity. The HS models indicate a trend of shorter conventional ENSO periodicity for the period from 2066 to 2100, which contrasts sharply with the conclusion drawn from the 24 CMIP6 models that show no significant change in ENSO periodicity duration. Additionally, the period of CP ENSO is projected to become shorter under SSP585 scenario for the HS models and all models. In contrast, the CP ENSO period change is insignificant for the LS models.

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引用次数: 0

Corrigendum to “Effects of equatorially-confined shear flow on MRG and Rossby waves” [Dyn. Atmos. Oceans 100 (2022) 101331] “赤道约束剪切流对MRG和rosby波的影响”的更正[Dyn. Atmos]。海洋100 (2022)101331]

IF 1.9 4区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Dynamics of Atmospheres and Oceans

Pub Date : 2024-12-01 DOI: 10.1016/j.dynatmoce.2024.101499

Mukesh Singh Raghav , Sharath Jose , Amit Apte , Rama Govindarajan

引用次数: 0

Impacts of two types of El Niño events on spring surface air temperature over Sri Lanka

IF 1.9 4区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Dynamics of Atmospheres and Oceans

Pub Date : 2024-11-29 DOI: 10.1016/j.dynatmoce.2024.101517

Pathmarasa Kajakokulan , Raju Attada , Dzung Nguyen-Le , Jasti S. Chowdary

The relationship between El Niño events and surface air temperature (SAT) over Sri Lanka (SL) has been well documented. However, the impact of the two different types of El Niño flavors on seasonal SAT variability in SL remains to be thoroughly investigated. Therefore, to identify the effect of two different types of El Niño on SAT over SL, we analyzed reanalysis and observational datasets from 1981 to 2020. This study mainly focused on the boreal spring season during the decaying phase of El Niño events. We show the presence of a strong SAT cooling in spring over the SL during the decaying phase of Central Pacific (CP) El Niño events, while intense spring SAT warming over SL is particularly pronounced during the Eastern Pacific (EP) El Niño decaying phase. It is found that low-level convergence over SL and the east coast of India associated with easterlies extending from the southern flank of the westward-shifted Western North Pacific anticyclones (WNPA) lead to updrafts. This results in enhanced cloud conditions and decreased incoming shortwave radiation, thereby causing strong cooling during CP El Niño events. Conversely, during EP El Niño, the WNPA shifts eastward, and the easterlies are confined around the equator, which helps develop the anti-cyclonic circulation over the Bay of Bengal (BoB). As a result, anomalous low-level divergence induces a strong downdraft over SL. This leads to cloud-free conditions and significantly enhanced incoming shortwave radiation during EP El Niño events, helping to enhance the SAT warming over SL. In addition, a composite analysis of CP and EP El Niño events demonstrated that strong cool (warm) conditions are prevalent in CP (EP) El Niño decaying spring years. This study highlights two distinct types of El Niño as a significant driver for understanding the SAT variability in Sri Lanka.

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