Studies on Lower Atmospheric Processes over South India using Numerical Atmospheric Models and Experiments

Inhaltsverzeichnis (Table of Contents)

• Introduction
• General Introduction
• Criticalities involved in the various Atmospheric Events
• Scales of Atmospheric Motion
• Rapid changes in Atmospheric Parameterization
• Computing Requirements
• Dissemination of Forecast Product to the User's Community
• Examples of some Mesoscale Atmospheric Processes
• Density or Gravity Current
• Tropical Cyclones
• Thunderstorms
• Tornadoes
• Squall Lines
• Sea/Land Breezes
• Gravity or Buoyancy Waves
• Mountain/Lee Waves
• Slope and Valley Winds
• History of Numerical Weather Prediction (NWP)
• Potentials of Atmospheric Model
• Objective of the Thesis
• Organization of the Thesis
• Numerical Atmospheric Models used in the Study
• General Introduction
• What is an 'Atmospheric Model'?
• Limitations of NWP Models
• Basic Classification of Atmospheric Models
• Hydrostatic Approximation
• Atmospheric Model classification
• High-resolution Regional Model (HRM)
• Differential form of the Model Equations
• Physical Parameterization
• Radiation and Clouds
• Grid Scale Precipitation
• Convection
• Turbulent Fluxes in ABL and Free Atmosphere
• Soil Model
• Operational Use of HRM based on GME Data
• Advanced Regional Prediction System (ARPS)
• Dynamic Equations and Numerical Formulation
• The Coordinate System
• Governing Equations
• Parameterization
• Sub-grid Scale Turbulence
• Microphysics
• Planetary Boundary Layer Depth
• Surface Flux
• Land Surface Energy and Soil Vegetation
• Cumulus Parameterization
• Boundary Conditions
• Lateral Boundary Conditions
• Top and Bottom Boundary Conditions
• Comparison between HRM and ARPS
• Limitations of HRM and ARPS
• Rationale Behind the Choice of the Models
• Discussion
• Statistical Assessment of Atmospheric Models used in the Study
• General Introduction
• Methodology of Evaluation of Statistical Bias and its Significance
• Model Bias and Simulation Errors: General Introduction
• Statistical Significance of the Model Bias
• Normalization of Model Bias
• Incorporation of Model Bias in Near Real Time Simulations
• Statistical Skill Parameters: Correlation Coefficient and Root Mean Square Error (RMSE)
• Statistical Evaluation of HRM forecast fields
• Error Analysis for the Entire Domain
• Methodology
• Model Performance for +24 hours and +48 hours simulations
• Monthly Mean Normalized Bias in different Seasons
• Evaluation of the Performance of the Model in the Entire Domain during different seasons
• Model Bias over SHAR and Trivandrum
• Sensitivity of ARPS to the Initial Conditions and its Impact on the forecast fields
• Discussion
• Characterization of Sea/Land Breeze Circulation Along the West Coast of Indian Sub-continent
• General Introduction
• Sea/Land Breeze Circulation
• SLBC over the West Coast of Indian Sub-continent: A Review
• Domain of Study and Definition of Sea Breeze Component
• Data
• Model Data
• Ship Data
• IMD Data
• Results
• Thermal and wind structure of SLBC over Ocean and Land
• Numerical Simulation of SLBC characteristics during pre-monsoon and winter
• Diurnal Variation of Sea/Land Breeze Component
• Spatial Variation of Sea Breeze component
• Spatial variation of Boundary Layer Height within the SLBC
• Discussion
• Mountain Wave Activity Over the Western Ghats of Indian Sub-continent
• General Introduction
• Mountain Wave Projects
• Mountain Waves and their Significance
• Domain of Study and Database
• Theory
• Mountain Waves
• Orographic Lifting
• Froude Number
• Scorer Parameter
• Results
• Vertical Propagation and Wave Breaking Characteristics from the Model Simulations
• Vertical Momentum Flux
• Discussion
• Thunderstorm Over the East and West Coast of Indian Sub-continent: A Case Study
• General Introduction
• Thunderstorm: Some Meteorological Aspects
• What is a Thunderstorm?
• Related Natural Hazards and Meteorological Importance
• Precursors to Thunderstorm Occurrence
• Triggering Mechanism
• Conditional Instability
• High Dew-point Temperature
• Low-level Wind Shear
• Life Cycle of Thunderstorm
• A Review of thunderstorm Studies
• Thunderstorm Events over SHAR and Trivandrum: Typical case Study
• Model Configuration
• Results
• Prediction of Thunderstorm over SHAR: A Case Study
• Prevailing Conditions
• Model Simulations
• Surface Level Horizontal Divergence
• Pressure Perturbation
• Vertical Velocity
• Discussion: Prediction of Thunderstorm
• Post Analysis of Thunderstorm event over Trivandrum
• Meteorological Conditions Prevailing over the Location

Zielsetzung und Themenschwerpunkte (Objectives and Key Themes)

The thesis aims to investigate the characteristics and dynamics of mesoscale atmospheric processes over the Indian subcontinent using numerical atmospheric models. The study focuses on improving the accuracy of weather forecasts by analyzing the performance of different models in simulating these events.

• Evaluating the performance of numerical atmospheric models in simulating mesoscale atmospheric processes
• Analyzing the characteristics of sea/land breeze circulation along the west coast of India
• Investigating the dynamics of mountain wave activity over the Western Ghats
• Examining the development and prediction of thunderstorms over the east and west coasts of India
• Exploring the impact of initial conditions and model parameterization on the accuracy of weather forecasts

Zusammenfassung der Kapitel (Chapter Summaries)

The first chapter provides a general introduction to the topic of mesoscale atmospheric processes, outlining the challenges and importance of accurate weather forecasting. It also presents the objectives and organization of the thesis.

Chapter 2 describes the numerical atmospheric models used in the study, including the High-resolution Regional Model (HRM) and the Advanced Regional Prediction System (ARPS). The chapter delves into the model equations, parameterizations, and limitations.

Chapter 3 focuses on the statistical assessment of the models, evaluating their performance in terms of bias, correlation, and root mean square error. The chapter examines the sensitivity of the models to initial conditions and their impact on forecast fields.

Chapter 4 analyzes the characteristics of sea/land breeze circulation along the west coast of India using both model data and observational data. The chapter investigates the diurnal and spatial variations of sea/land breeze components and boundary layer height.

Chapter 5 investigates the dynamics of mountain wave activity over the Western Ghats, examining the role of orographic lifting, Froude number, and Scorer parameter in wave formation and propagation.

Chapter 6 presents a case study of a thunderstorm event over the east and west coasts of India. The chapter analyzes the meteorological conditions preceding the event and examines the model's ability to predict the thunderstorm's development and intensity.

Schlüsselwörter (Keywords)

Mesoscale atmospheric processes, numerical weather prediction, high-resolution regional model (HRM), Advanced Regional Prediction System (ARPS), statistical evaluation, sea/land breeze circulation, mountain wave activity, thunderstorms, India.