Thornthwaite Formula Calculator

✖Adjustment Factor for the number of hours of daylight and days, in the month, related to the latitude of the place.ⓘ Adjustment Factor [L_a]			+10% -10%
✖Mean Air Temperature observed for incident solar radiation outside the atmosphere.ⓘ Mean Air Temperature [T_a]			+10% -10%
✖Total Heat Index Values of a total of twelve months.ⓘ Total Heat Index [I_t]			+10% -10%
✖An Empirical Constant used in the Thornthwaite Formula depends on the total of 12 monthly values index.ⓘ An Empirical Constant [a_Th]			+10% -10%

✖Potential Evapotranspiration in Crop Season is the potential evaporation from soils plus transpiration by plants.ⓘ Thornthwaite Formula [E_T]

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Formula

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Thornthwaite Formula

Formula

`"E"_{"T"} = 1.6*"L"_{"a"}*((10*"T"_{"a"})/"I"_{"t"})^"a"_{"Th"}`

Example

`"26.9843cm"=1.6*"1.04"*((10*"20")/"10")^"0.93"`

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Thornthwaite Formula Solution

STEP 0: Pre-Calculation Summary

Formula Used

Potential Evapotranspiration in Crop Season = 1.6*Adjustment Factor*((10*Mean Air Temperature)/Total Heat Index)^An Empirical Constant
E_T = 1.6*L_a*((10*T_a)/I_t)^a_Th
This formula uses 5 Variables

Variables Used

Potential Evapotranspiration in Crop Season - (Measured in Centimeter) - Potential Evapotranspiration in Crop Season is the potential evaporation from soils plus transpiration by plants.
Adjustment Factor - Adjustment Factor for the number of hours of daylight and days, in the month, related to the latitude of the place.
Mean Air Temperature - Mean Air Temperature observed for incident solar radiation outside the atmosphere.
Total Heat Index - Total Heat Index Values of a total of twelve months.
An Empirical Constant - An Empirical Constant used in the Thornthwaite Formula depends on the total of 12 monthly values index.

STEP 1: Convert Input(s) to Base Unit

Adjustment Factor: 1.04 --> No Conversion Required
Mean Air Temperature: 20 --> No Conversion Required
Total Heat Index: 10 --> No Conversion Required
An Empirical Constant: 0.93 --> No Conversion Required

STEP 2: Evaluate Formula

Substituting Input Values in Formula

E_T = 1.6*L_a*((10*T_a)/I_t)^a_Th --> 1.6*1.04*((10*20)/10)^0.93

Evaluating ... ...

E_T = 26.9843038157774

STEP 3: Convert Result to Output's Unit

0.269843038157774 Meter -->26.9843038157774 Centimeter (Check conversion here)

FINAL ANSWER

26.9843038157774 ≈ 26.9843 Centimeter <-- Potential Evapotranspiration in Crop Season

(Calculation completed in 00.006 seconds)

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< 8 Evapotranspiration Equations Calculators

Equation for Net Radiation of Evaporable Water

Go Net Radiation of Evaporable Water = Incident Solar Radiation Outside the Atmosphere*(1-Reflection Coefficient)*(Constant depending on Latitude+(A constant*Actual Duration of Bright Sunshine/Maximum Possible Hours of Bright Sunshine))-Stefan-Boltzmann constant*Mean Air Temperature^4*(0.56-0.092*sqrt(Actual Vapour Pressure))*(0.1+(0.9*Actual Duration of Bright Sunshine/Maximum Possible Hours of Bright Sunshine))

Net Radiation of Evaporable water given Daily Potential Evapotranspiration

Go Net Radiation of Evaporable Water = (Daily Potential Evapotranspiration*(Slope of Saturation Vapour Pressure+Psychrometric Constant)-(Parameter of Wind Velocity and Saturation Deficit*Psychrometric Constant))/Slope of Saturation Vapour Pressure

Parameter Including Wind Velocity and Saturation Deficit

Go Parameter of Wind Velocity and Saturation Deficit = (Daily Potential Evapotranspiration*(Slope of Saturation Vapour Pressure+Psychrometric Constant)-(Slope of Saturation Vapour Pressure*Net Radiation of Evaporable Water))/Psychrometric Constant

Penman's Equation

Go Daily Potential Evapotranspiration = (Slope of Saturation Vapour Pressure*Net Radiation of Evaporable Water+Parameter of Wind Velocity and Saturation Deficit*Psychrometric Constant)/(Slope of Saturation Vapour Pressure+Psychrometric Constant)

Mean Monthly Air Temperature for Potential Evapotranspiration in Thornthwaite Equation

Go Mean Air Temperature = (Potential Evapotranspiration in Crop Season/(1.6*Adjustment Factor))^(1/An Empirical Constant)*(Total Heat Index/10)

Adjustment related to Latitude of Place given Potential Evapotranspiration

Go Adjustment Factor = Potential Evapotranspiration in Crop Season/(1.6*((10*Mean Air Temperature)/Total Heat Index)^An Empirical Constant)

Thornthwaite Formula

Go Potential Evapotranspiration in Crop Season = 1.6*Adjustment Factor*((10*Mean Air Temperature)/Total Heat Index)^An Empirical Constant

Equation for Blaney Criddle

Go Potential Evapotranspiration in Crop Season = 2.54*An Empirical Coefficient*Sum of Monthly Consumptive Use factors

Thornthwaite Formula Formula

Potential Evapotranspiration in Crop Season = 1.6*Adjustment Factor*((10*Mean Air Temperature)/Total Heat Index)^An Empirical Constant
E_T = 1.6*L_a*((10*T_a)/I_t)^a_Th

What is Thornthwaite Equation?

The Thornthwaite (1948) equation is a widely used empirical method for estimating potential evapotranspiration (PET). The equation only requires the mean monthly air temperature and mean daily daylight hours for each month, which can be calculated from latitude.

What is Thornthwaite Method?

Potential evapotranspiration (PET) is estimated via the method of Thornthwaite. The only variable used is monthly temperature [t (C)]. Generally, the Thornthwaite method underestimates PET in the arid areas and overestimates PET in the humid areas.

How to Calculate Thornthwaite Formula?

Thornthwaite Formula calculator uses Potential Evapotranspiration in Crop Season = 1.6*Adjustment Factor*((10*Mean Air Temperature)/Total Heat Index)^An Empirical Constant to calculate the Potential Evapotranspiration in Crop Season, The Thornthwaite Formula formula is defined as the empirical method for estimating potential evapotranspiration (PET). The equation only requires the mean monthly air temperature and mean daily daylight hours for each month, which can be calculated from latitude. Potential Evapotranspiration in Crop Season is denoted by E_T symbol.

How to calculate Thornthwaite Formula using this online calculator? To use this online calculator for Thornthwaite Formula, enter Adjustment Factor (L_a), Mean Air Temperature (T_a), Total Heat Index (I_t) & An Empirical Constant (a_Th) and hit the calculate button. Here is how the Thornthwaite Formula calculation can be explained with given input values -> 2698.43 = 1.6*1.04*((10*20)/10)^0.93.

FAQ

What is Thornthwaite Formula?

The Thornthwaite Formula formula is defined as the empirical method for estimating potential evapotranspiration (PET). The equation only requires the mean monthly air temperature and mean daily daylight hours for each month, which can be calculated from latitude and is represented as E_T = 1.6*L_a*((10*T_a)/I_t)^a_Th or Potential Evapotranspiration in Crop Season = 1.6*Adjustment Factor*((10*Mean Air Temperature)/Total Heat Index)^An Empirical Constant. Adjustment Factor for the number of hours of daylight and days, in the month, related to the latitude of the place, Mean Air Temperature observed for incident solar radiation outside the atmosphere, Total Heat Index Values of a total of twelve months & An Empirical Constant used in the Thornthwaite Formula depends on the total of 12 monthly values index.

How to calculate Thornthwaite Formula?

The Thornthwaite Formula formula is defined as the empirical method for estimating potential evapotranspiration (PET). The equation only requires the mean monthly air temperature and mean daily daylight hours for each month, which can be calculated from latitude is calculated using Potential Evapotranspiration in Crop Season = 1.6*Adjustment Factor*((10*Mean Air Temperature)/Total Heat Index)^An Empirical Constant. To calculate Thornthwaite Formula, you need Adjustment Factor (L_a), Mean Air Temperature (T_a), Total Heat Index (I_t) & An Empirical Constant (a_Th). With our tool, you need to enter the respective value for Adjustment Factor, Mean Air Temperature, Total Heat Index & An Empirical Constant and hit the calculate button. You can also select the units (if any) for Input(s) and the Output as well.

How many ways are there to calculate Potential Evapotranspiration in Crop Season?

In this formula, Potential Evapotranspiration in Crop Season uses Adjustment Factor, Mean Air Temperature, Total Heat Index & An Empirical Constant. We can use 1 other way(s) to calculate the same, which is/are as follows -

Potential Evapotranspiration in Crop Season = 2.54*An Empirical Coefficient*Sum of Monthly Consumptive Use factors

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