Change In Vapour Pressure Given Evaporation Loss Per Day Calculator

Formula Used:

\[ \delta V = \frac{E}{C' \times (1.465 - (0.00732 \times P_a)) \times (0.44 + (0.0732 \times u)))} \]

Evaporation Loss Per Day:

Rohwer's Formula Constant:

Atmospheric Pressure:

cmHg

Mean Wind Velocity:

m/s

Change In Vapour Pressure:

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1. What is Change In Vapour Pressure?

Change In Vapour Pressure refers to the difference between maximum vapour pressure and actual vapour pressure. It is a crucial parameter in evaporation studies and meteorological calculations.

2. How Does the Calculator Work?

The calculator uses Rohwer's formula:

\[ \delta V = \frac{E}{C' \times (1.465 - (0.00732 \times P_a)) \times (0.44 + (0.0732 \times u)))} \]

Where:

\( \delta V \) — Change in Vapour Pressure (cmHg)
\( E \) — Evaporation Loss Per Day (m)
\( C' \) — Rohwer's Formula Constant
\( P_a \) — Atmospheric Pressure (cmHg)
\( u \) — Mean Wind Velocity (m/s)

Explanation: The formula calculates the change in vapour pressure based on evaporation loss, atmospheric conditions, and wind velocity using Rohwer's empirical approach.

3. Importance of Vapour Pressure Calculation

Details: Accurate vapour pressure calculation is essential for evaporation rate estimation, hydrological studies, agricultural water management, and climate modeling.

4. Using the Calculator

Tips: Enter evaporation loss in meters, Rohwer's constant, atmospheric pressure in cmHg, and mean wind velocity in m/s. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is Rohwer's Formula Constant?
A: Rohwer's Formula Constant is an empirical coefficient used in Rohwer's equation to estimate evaporation rates, adjusting for local climatic conditions.

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

Q3: What are typical values for atmospheric pressure?
A: Atmospheric pressure typically ranges from 74-76 cmHg at sea level, decreasing with altitude.

Q4: How does temperature affect vapour pressure?
A: While not directly in this formula, temperature significantly affects evaporation rates and maximum vapour pressure capacity of air.

Q5: What are the limitations of Rohwer's formula?
A: The formula is empirical and may require local calibration. It may be less accurate in extreme weather conditions or for very small water bodies.