The evaporation-rate relation E = 0.771 (1.465 - 0.00732 B) (0.44 - 0.007375 V) (pe - pa) corresponds to which formula and unit system?

Introduction:
Pan and reservoir evaporation are often estimated using empirical mass-transfer relations that combine wind, pressure, and vapor-pressure deficit. Recognizing the correct formula and units is key to consistent evaporation computations.

Given Data / Assumptions:

• Given expression: E = 0.771 (1.465 - 0.00732 B) (0.44 - 0.007375 V) (pe - pa).
• Symbols: B = barometric pressure; V = wind speed; pe - pa = vapor-pressure deficit.

Concept / Approach:
Roohwer’s formulation explicitly includes pressure and wind corrections multiplying the vapor-pressure deficit. The numerical coefficients indicate the chosen unit system (metric vs. imperial) because they embed conversion factors.

Step-by-Step Solution:
Step 1: Identify structure: product of (pressure factor) * (wind factor) * (vapor-pressure deficit) = hallmark of Roohwer.Step 2: Check constants (0.771, 1.465, 0.44, etc.), which match the M.K.S. version after unit harmonization.Step 3: Conclude the expression corresponds to Roohwer in M.K.S.

Verification / Alternative check:
Dimensional consistency with metric inputs (e.g., V in km/h or m/s converted within the constants) aligns with M.K.S. tabulations used in reservoir studies.

Why Other Options Are Wrong:

• Roohwer in F.P.S.: Different constants; imperial versions use alternative numerical factors.
• Dalton in F.P.S. or M.K.S.: Dalton’s form is proportional to (es - ea) with a wind function but lacks this specific compound factorization with B.

Common Pitfalls:

• Mixing unit systems when applying empirical coefficients.
• Assuming all mass-transfer formulas are interchangeable without re-deriving constants.

Final Answer:
Roohwer's formula in M.K.S..