Calculator
Use measured temperatures and altitudes, or switch to prediction mode for forward and inverse lapse-rate calculations.
Example Data Table
This sample profile shows how temperature commonly decreases with altitude in a simple mid-tropospheric example.
| Observation | Altitude (m) | Temperature (°C) | Interval Lapse Rate (K/km) |
|---|---|---|---|
| Station A | 0 | 24.0 | — |
| Station B | 500 | 20.8 | 6.4 |
| Station C | 1000 | 17.5 | 6.6 |
| Station D | 1500 | 14.3 | 6.4 |
| Station E | 2000 | 11.0 | 6.6 |
Formula Used
Γ = - (T2 - T1) / (z2 - z1)
Here, Γ is the lapse rate, T is temperature, and z is altitude. The negative sign keeps the result positive when temperature decreases with height.
Ttarget = Tbase - Γ × Δz
Use this form when you know the lapse rate and altitude difference. Keep Γ in K/km and Δz in km for consistent units.
ztarget = zbase + (Tbase - Ttarget) / Γ
This inverse form solves the elevation where a chosen temperature should occur for a fixed lapse rate.
Standard atmosphere ≈ 6.5 K/km, dry adiabatic ≈ 9.8 K/km, moist adiabatic ≈ 4 to 7 K/km
Moist adiabatic lapse rate is approximate because humidity, pressure, and condensation vary with atmospheric conditions.
How to Use This Calculator
- Choose a calculation mode based on your task: measured profile, forward prediction, or inverse altitude solving.
- Select your preferred temperature and altitude units before entering data.
- Enter the known temperatures, altitudes, and lapse rate inputs. Use positive lapse rates in K/km.
- Press Calculate to display the result above the form, review the graph, and export the profile as CSV or PDF.
- Compare your computed value with standard, dry adiabatic, and moist adiabatic references to judge atmospheric stability.
FAQs
1) What is atmospheric lapse rate?
Atmospheric lapse rate is the rate at which air temperature changes with altitude. In most tropospheric situations, temperature decreases as height increases, so the lapse rate is reported as a positive value in K/km.
2) What is the standard atmospheric lapse rate?
A common reference is 6.5 K/km. It is a convenient average used in standard-atmosphere models, aviation, and teaching. Real weather conditions often differ from this value.
3) What is the dry adiabatic lapse rate?
The dry adiabatic lapse rate is about 9.8 K/km. It describes how unsaturated air cools as it rises without exchanging heat with its surroundings.
4) What is the moist adiabatic lapse rate?
The moist adiabatic lapse rate is lower than the dry rate, usually around 4 to 7 K/km. Condensation releases latent heat, which slows the cooling of rising saturated air.
5) Why can a lapse rate become negative?
A negative value means temperature increases with altitude over that layer. This is a temperature inversion and usually indicates a very stable atmosphere with suppressed vertical mixing.
6) Can I use Celsius, Fahrenheit, and Kelvin?
Yes. The calculator converts all selected temperature units internally, performs the physics in consistent units, and then returns answers in the unit you selected.
7) How accurate is the moist adiabatic comparison?
It is a practical approximation, not a full thermodynamic model. The actual moist adiabatic rate changes with humidity, pressure, and temperature, so the reference should be used for comparison rather than exact forecasting.
8) What do the CSV and PDF downloads contain?
They include the key summary values and the sampled profile table used for the graph. This makes it easy to document results, share outputs, or continue analysis in other tools.