07. MSIS Option 7: Semidiurnal

This example demonstrates the analysis of MSIS Option 7, which controls 12-hour atmospheric tidal effects. This option represents a key physical process that affects atmospheric density variations.

Understanding how this option affects atmospheric structure is important for atmospheric modeling, satellite operations, and space weather applications.

import matplotlib.pyplot as plt
from msis_options_utils import create_option_analysis_figure

Option 7 controls 12-hour atmospheric tidal effects

This atmospheric effect includes:

• Thermal forcing by solar heating

• Gravitational tidal forces (minor contribution)

• Atmospheric wave propagation and resonance

• Interaction with the Earth’s rotation

This analysis shows how turning OFF this option affects atmospheric density across different dimensions and conditions.

option_index = 7
option_name = "Semidiurnal"

fig = create_option_analysis_figure(option_index, option_name)

Understanding the Results

Panel A (Altitude Profiles): Shows how this effect varies with altitude and between different seasonal and diurnal conditions. Look for differences between the four curves to understand temporal variability.

Panel B (Geographic Map): Reveals the global pattern of this atmospheric effect. The contour plot shows percentage changes when the option is turned OFF compared to the baseline (all options ON).

Panel C (Diurnal Cycle): Demonstrates how this effect varies throughout a 24-hour period at a fixed location (45°N, 0°E, 300 km altitude).

Panel D (Seasonal Cycle): Shows how the strength of this effect varies throughout the year, revealing seasonal dependencies.

plt.show()

Physical Importance

This atmospheric effect is important because:

• Important for atmospheric wave dynamics

• Affects satellite drag calculations

• Key component of upper atmospheric dynamics

• Provides insight into atmospheric wave propagation

When this option is turned OFF, these physical processes are removed from the atmospheric model, which can significantly impact the accuracy of density predictions depending on the specific application and conditions.