Dry Adiabatic Lapse Rate Calculator

Calculator Inputs

Reference Temperature

Temperature Unit

Start Altitude

End Altitude

Altitude Unit

Gravity, g (m/s²)

Specific Heat Capacity, c_p (J/kg·K)

Graph Points

Formula Used

Dry adiabatic lapse rate:

Γ_d = g / c_p

Parcel temperature at a new altitude:

T₂ = T₁ − Γ_d(z₂ − z₁)

Where:

Γ_d = dry adiabatic lapse rate
g = local gravitational acceleration
c_p = specific heat at constant pressure
T₁ and T₂ = parcel temperatures
z₁ and z₂ = initial and final altitudes

For standard near-Earth conditions, the dry adiabatic lapse rate is about 9.77 to 9.8 K/km. This calculator lets you use custom gravity and heat capacity values for more advanced scenarios.

How to Use This Calculator

Enter the parcel’s reference temperature and select its unit.
Provide the starting altitude and ending altitude.
Choose the altitude unit that matches your values.
Enter gravity and specific heat capacity. Standard Earth defaults are already filled in.
Set the number of graph points for the plotted parcel path.
Click the calculate button to show the result above the form.
Use the CSV button for spreadsheet-friendly data export.
Use the PDF button to save a printable summary with the chart.

Example Data Table

Reference Temp	Start Altitude	End Altitude	g	c_p	DALR	Final Temp
15 °C	0 m	1000 m	9.80665 m/s²	1004 J/kg·K	9.77 K/km	5.23 °C
20 °C	500 m	2500 m	9.80665 m/s²	1004 J/kg·K	9.77 K/km	0.46 °C
25 °C	2000 m	500 m	9.80665 m/s²	1004 J/kg·K	9.77 K/km	39.65 °C
288.15 K	0 km	3 km	9.80665 m/s²	1004 J/kg·K	9.77 K/km	258.85 K

Frequently Asked Questions

1. What is the dry adiabatic lapse rate?

It is the rate at which an unsaturated air parcel changes temperature as it moves vertically without exchanging heat with its surroundings. Near Earth, it is roughly 9.8 K per kilometer.

2. Why does rising dry air cool?

As the parcel rises, surrounding pressure decreases. The parcel expands and does work on its environment. That expansion lowers internal energy, so temperature drops even when no heat enters or leaves.

3. Why does descending dry air warm?

During descent, pressure increases and the parcel compresses. Compression raises internal energy, so the parcel warms adiabatically. This is the same principle behind warming in downslope wind events.

4. When should this calculator be used?

Use it for unsaturated parcels, basic atmospheric profiling, meteorology exercises, and conceptual physics work. It is best when condensation, latent heat release, and strong moisture effects are not part of the model.

5. Why can gravity and specific heat be changed?

Changing gravity or specific heat lets you model nonstandard conditions, alternate gases, or sensitivity studies. Since Γd = g/cp, either variable directly changes the computed lapse rate.

6. Is Celsius acceptable for this calculation?

Yes. Temperature differences in Celsius and Kelvin have the same size, so lapse-rate calculations work cleanly. The code internally protects the physics and then returns results in your chosen temperature unit.

7. What happens if my ending altitude is lower?

The calculator treats that as descent. The parcel then warms, so the final temperature becomes higher than the reference temperature. The plotted line will also show temperature increasing with lower altitude.

8. Does this include moisture or condensation?

No. This page is for dry adiabatic behavior only. Once air becomes saturated, latent heat matters and the moist adiabatic lapse rate should be used instead.