Constant Used In Rohwer's Formula Given Evaporation Loss Per Day Calculator

Rohwer's Formula:

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

Evaporation Loss Per Day (E):

Atmospheric Pressure (Pa):

cm Hg

Mean Wind Velocity (u):

m/s

Maximum Vapor Pressure (V):

cm Hg

Actual Vapor Pressure (v):

cm Hg

Rohwer's Formula Constant (C'):

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1. What is Rohwer's Formula Constant?

Rohwer's Formula Constant refers to an empirical coefficient used in Rohwer's equation to estimate evaporation rates, adjusting for local climatic conditions. It is a crucial parameter in hydrological and meteorological studies for accurate evaporation prediction.

2. How Does the Calculator Work?

The calculator uses Rohwer's formula:

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

Where:

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

Explanation: The formula calculates the empirical constant by considering evaporation loss, atmospheric conditions, wind velocity, and vapor pressure differences.

3. Importance of Rohwer's Formula Constant

Details: Accurate determination of Rohwer's constant is essential for precise evaporation rate estimation, which is critical in water resource management, agricultural planning, and climate studies.

4. Using the Calculator

Tips: Enter all values in the specified units. Ensure evaporation loss, atmospheric pressure, wind velocity, and vapor pressures are positive values. The difference between maximum and actual vapor pressure should not be zero.

5. Frequently Asked Questions (FAQ)

Q1: What is the typical range for Rohwer's constant?
A: The constant typically ranges between 0.3-1.2, depending on local climatic conditions and measurement accuracy.

Q2: Why is wind velocity important in evaporation calculations?
A: Wind velocity affects the rate of vapor removal from the surface, influencing the overall evaporation rate.

Q3: How does atmospheric pressure affect evaporation?
A: Lower atmospheric pressure generally increases evaporation rates as it reduces the boiling point of water.

Q4: What's the difference between maximum and actual vapor pressure?
A: Maximum vapor pressure is the saturation pressure at a given temperature, while actual vapor pressure reflects the current humidity level.

Q5: Can this formula be used for all climatic conditions?
A: While Rohwer's formula is widely applicable, local calibration may be needed for extreme climatic conditions or specific geographical regions.