Maximum Vapour Pressure Given Evaporation Loss Per Day Calculator

Formula Used:

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

Actual Vapour Pressure (v):

cm Hg

Evaporation Loss per Day (E):

Rohwer's Formula Constant (C'):

Atmospheric Pressure (P_a):

cm Hg

Mean Wind Velocity (u):

m/s

Maximum Vapour Pressure (V):

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1. What Is The Maximum Vapour Pressure?

The Maximum Vapour Pressure refers to the highest pressure exerted by a vapour in equilibrium with its liquid at a given temperature, often measured in cm Hg or kPa. It represents the saturation point where the air can hold no more moisture.

2. How Does The Calculator Work?

The calculator uses Rohwer's formula:

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

Where:

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

Explanation: This formula calculates the maximum vapour pressure by accounting for evaporation loss, atmospheric conditions, and wind velocity using Rohwer's empirical approach.

3. Importance Of Maximum Vapour Pressure Calculation

Details: Calculating maximum vapour pressure is essential for understanding evaporation processes, water resource management, agricultural planning, and meteorological studies. It helps determine the potential for evaporation under specific environmental conditions.

4. Using The Calculator

Tips: Enter actual vapour pressure in cm Hg, evaporation loss per day in meters, Rohwer's constant, atmospheric pressure in cm Hg, and mean wind velocity in m/s. All values must be valid positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is the difference between actual and maximum vapour pressure?
A: Actual vapour pressure measures current moisture content, while maximum vapour pressure represents the saturation point at which air can hold no more moisture at a given temperature.

Q2: How does wind velocity affect vapour pressure?
A: Higher wind velocities increase evaporation rates, which affects the calculation of maximum vapour pressure using Rohwer's formula.

Q3: What is Rohwer's Formula Constant?
A: Rohwer's Formula Constant is an empirical coefficient that adjusts the evaporation calculation for local climatic conditions and surface characteristics.

Q4: When is this calculation most useful?
A: This calculation is particularly useful in hydrology, agriculture, and environmental engineering for predicting evaporation rates from water surfaces.

Q5: Are there limitations to Rohwer's formula?
A: Yes, Rohwer's formula is empirical and may require calibration for specific local conditions. It works best for open water surfaces and may be less accurate for other surfaces.