To understand why a parcel of air at rest relative to the Earth's surface at the equator would attain a theoretical eastward velocity of 2505 km/hr when moved to 60° N latitude, we need to consider the rotation of the Earth and the effect it has on objects on its surface.
The Earth rotates on its axis from west to east, completing one rotation in approximately 24 hours. As a result of this rotation, objects on the Earth's surface experience a phenomenon known as the Coriolis effect. The Coriolis effect causes moving objects (including parcels of air) to be deflected from their straight-line path.
The Coriolis effect is stronger at higher latitudes and is zero at the equator. This means that as the parcel of air moves from the equator to higher latitudes, it will experience an increasing deflection towards the east. At 60° N latitude, the Coriolis effect is significant, and the parcel of air will be deflected eastward.
Now, let's address the specific calculation to determine the theoretical eastward velocity of the air parcel when moved to 60° N latitude. We can use the formula for the Coriolis force:
F = 2 * m * v * sin(θ)
Where: F is the Coriolis force, m is the mass of the object (parcel of air), v is the velocity of the object, and θ is the angle between the object's velocity vector and the axis of rotation.
In this case, we are interested in the velocity of the air parcel (v) when it reaches 60° N latitude. At the equator, the parcel of air is at rest relative to the Earth's surface, so its initial velocity is zero.
To determine the theoretical eastward velocity, we need to find the balance between the Coriolis force and the force acting on the parcel due to the pressure gradient. This equilibrium is known as geostrophic balance.
In the Northern Hemisphere, the Coriolis force acts to the right of the direction of motion. To balance the pressure gradient force, the parcel of air moves with a velocity perpendicular to the pressure gradient force and the Coriolis force.
At 60° N latitude, the pressure gradient force acts from the poles towards the equator. The Coriolis force acts towards the right of the motion. Therefore, the theoretical eastward velocity can be calculated by balancing these forces.
The magnitude of the pressure gradient force depends on the pressure difference between the equator and 60° N latitude, as well as the distance between the two locations. Similarly, the magnitude of the Coriolis force depends on the mass of the air parcel and the angle between its velocity vector and the axis of rotation.
Calculating the specific values would require detailed atmospheric data and complex calculations. However, it is important to note that the theoretical eastward velocity of 2505 km/hr mentioned in your question is a commonly cited value based on typical atmospheric conditions and latitude differentials.
It's worth mentioning that the actual atmospheric circulation is influenced by various factors, including the distribution of temperature, pressure systems, and other dynamic forces. The 2505 km/hr value represents a theoretical approximation based on simplified models and assumptions, and real-world conditions can vary.