In meteorology, what is the main physical reason that a sea breeze blows from the sea toward the land during the daytime?

Introduction / Context:
Along coastlines, people often experience a cool breeze blowing from the sea toward the land during warm sunny days. This regular daytime wind is called a sea breeze. Understanding why sea breezes occur requires knowledge of how land and water heat at different rates and how this leads to pressure differences that drive air motion. This question asks you to identify the main physical cause behind the formation of a sea breeze.

Given Data / Assumptions:
- The situation is a sunny daytime along a coast with land on one side and sea on the other.
- Land and water have different specific heat capacities and therefore heat at different rates.
- Air pressure depends on air temperature and density above land and sea.
- Planetary effects like the Coriolis force influence wind direction on large scales but are not the primary local cause here.

Concept / Approach:
Land surfaces heat up quickly during the day because they have lower specific heat capacity and often lower thermal inertia than water. Water heats more slowly. As a result, air over the land becomes warmer and less dense than air over the sea. Warm air over the land rises, creating a region of lower surface pressure. Cooler, higher pressure air over the sea then flows toward the land to replace the rising warm air. This flow of air from sea to land is the sea breeze. The root cause is therefore a pressure difference created by unequal heating of land and sea, which itself is due to their different specific heats.

Step-by-Step Solution:
Step 1: During daytime, the sun heats both land and sea, but land warms faster because of lower specific heat capacity. Step 2: The air above the land warms, becomes less dense and rises, producing a local region of lower air pressure near the surface. Step 3: The air above the sea remains relatively cooler and denser, so surface pressure over the water stays relatively higher. Step 4: Air flows from regions of higher pressure to regions of lower pressure, so air moves from the sea toward the land. Step 5: This horizontal movement of cooler air from the sea that replaces rising warm air over land is the sea breeze. Step 6: Therefore, the immediate cause is the pressure difference created by unequal heating of land and sea, controlled by their different specific heats.

Verification / Alternative check:
Observations show that sea breezes are strongest on clear, hot days when the temperature contrast between land and sea is large. They weaken or disappear on cloudy days or at night when the temperature difference is smaller. This behaviour supports the explanation based on differential heating and pressure differences. Numerical weather models and meteorological diagrams also show pressure gradients from sea to land during typical sea breeze conditions.

Why Other Options Are Wrong:
Only the Coriolis force: The Coriolis effect turns winds on large scales but does not by itself create the initial pressure difference that drives a sea breeze.
Random changes in wind direction: Sea breezes follow a regular pattern based on heating differences and are not random.
Only the specific heat of water, without affecting air pressure: Specific heat is important but only because it leads to temperature and pressure differences; ignoring pressure misses the key driving force for the wind.

Common Pitfalls:
Learners sometimes think of wind as purely random or blame sea breezes entirely on coastal geography. Others focus only on temperature and forget that pressure differences are the actual driving force for air motion. Remember that land and sea heat at different rates due to their specific heats, and this creates pressure gradients that produce well organised local winds like sea breezes.

Final Answer:
A sea breeze is mainly caused by a pressure difference created by unequal heating of land and sea due to their different specific heats.