Atmospheric Pressure Given Evaporation Loss Per Day Calculator

Atmospheric Pressure Formula:

\[ P_a = \frac{1.456 - \left( \frac{E}{C' \times (0.44 + 0.0732 \times u) \times (V - v)} \right)}{0.00732} \]

Evaporation Loss Per Day (E):

Rohwer's Formula Constant (C'):

Mean Wind Velocity (u):

m/s

Maximum Vapour Pressure (V):

cm Hg

Actual Vapour Pressure (v):

cm Hg

Atmospheric Pressure (P_a):

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1. What is the Atmospheric Pressure Formula?

The Atmospheric Pressure formula estimates atmospheric pressure based on evaporation loss, wind velocity, and vapour pressure differences using Rohwer's empirical approach. It provides a method to calculate atmospheric pressure from measurable environmental parameters.

2. How Does the Calculator Work?

The calculator uses the Atmospheric Pressure formula:

\[ P_a = \frac{1.456 - \left( \frac{E}{C' \times (0.44 + 0.0732 \times u) \times (V - v)} \right)}{0.00732} \]

Where:

\( P_a \) — Atmospheric Pressure (cm Hg)
\( E \) — Evaporation Loss Per Day (m)
\( C' \) — Rohwer's Formula Constant
\( u \) — Mean Wind Velocity (m/s)
\( V \) — Maximum Vapour Pressure (cm Hg)
\( v \) — Actual Vapour Pressure (cm Hg)

Explanation: The equation accounts for the relationship between evaporation rate, wind speed, and vapour pressure difference to estimate atmospheric pressure.

3. Importance of Atmospheric Pressure Calculation

Details: Accurate atmospheric pressure estimation is crucial for meteorological studies, evaporation rate predictions, and understanding environmental processes related to water cycle and climate patterns.

4. Using the Calculator

Tips: Enter evaporation loss in meters, Rohwer's constant, wind velocity in m/s, and vapour pressures in cm Hg. All values must be valid (positive values, V > v).

5. Frequently Asked Questions (FAQ)

Q1: What is Rohwer's Formula Constant?
A: Rohwer's Formula Constant is an empirical coefficient that adjusts for local climatic conditions and surface characteristics in evaporation calculations.

Q2: Why is wind velocity important in this calculation?
A: Wind velocity affects evaporation rates by removing saturated air from the surface and replacing it with drier air, thus influencing the evaporation process.

Q3: What are typical values for vapour pressure?
A: Vapour pressure values depend on temperature and humidity. Maximum vapour pressure increases with temperature, while actual vapour pressure reflects current humidity conditions.

Q4: Are there limitations to this equation?
A: This is an empirical equation and may be less accurate in extreme conditions or for surfaces with different evaporation characteristics than those used to derive the constants.

Q5: Can this formula be used for all surfaces?
A: The formula was developed for water surfaces. Different constants may be needed for other surfaces like soil or vegetation.