.lrc-container {
max-width: 600px;
margin: 0 auto;
padding: 20px;
background-color: #f9f9f9;
border: 1px solid #e0e0e0;
border-radius: 8px;
font-family: Arial, sans-serif;
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
}
.lrc-title {
text-align: center;
color: #2c3e50;
margin-bottom: 20px;
}
.lrc-input-group {
margin-bottom: 15px;
}
.lrc-input-group label {
display: block;
margin-bottom: 5px;
font-weight: bold;
color: #34495e;
}
.lrc-input-group input {
width: 100%;
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
box-sizing: border-box; /* Ensures padding doesn't affect width */
}
.lrc-btn {
width: 100%;
padding: 12px;
background-color: #3498db;
color: white;
border: none;
border-radius: 4px;
cursor: pointer;
font-size: 16px;
font-weight: bold;
transition: background-color 0.3s;
}
.lrc-btn:hover {
background-color: #2980b9;
}
.lrc-result {
margin-top: 20px;
padding: 15px;
background-color: #ecf0f1;
border-radius: 4px;
text-align: center;
display: none;
}
.lrc-result h3 {
margin: 0 0 10px;
color: #2c3e50;
}
.lrc-value {
font-size: 24px;
color: #e74c3c;
font-weight: bold;
}
.lrc-note {
font-size: 0.9em;
color: #7f8c8d;
margin-top: 10px;
}
.lrc-error {
color: red;
font-size: 0.9em;
margin-top: 5px;
display: none;
}
.article-container {
max-width: 800px;
margin: 40px auto;
font-family: Arial, sans-serif;
line-height: 1.6;
color: #333;
}
.article-container h2 {
color: #2c3e50;
border-bottom: 2px solid #3498db;
padding-bottom: 10px;
}
.article-container h3 {
color: #34495e;
margin-top: 25px;
}
.article-container ul {
background: #fdfdfd;
padding: 20px 40px;
border-left: 4px solid #3498db;
}
function calculateLapseRate() {
var t1 = parseFloat(document.getElementById('lrc_temp1').value);
var z1 = parseFloat(document.getElementById('lrc_alt1').value);
var t2 = parseFloat(document.getElementById('lrc_temp2').value);
var z2 = parseFloat(document.getElementById('lrc_alt2').value);
var resultBox = document.getElementById('lrc_result');
var output = document.getElementById('lrc_output');
var status = document.getElementById('lrc_status');
var errorBox = document.getElementById('lrc_error');
// Validation
if (isNaN(t1) || isNaN(z1) || isNaN(t2) || isNaN(z2)) {
errorBox.style.display = 'block';
errorBox.innerText = "Please enter valid numeric values for all fields.";
resultBox.style.display = 'none';
return;
}
if (z1 === z2) {
errorBox.style.display = 'block';
errorBox.innerText = "Base altitude and Final altitude cannot be the same.";
resultBox.style.display = 'none';
return;
}
errorBox.style.display = 'none';
// Formula: Lapse Rate (Gamma) = – (T2 – T1) / (z2 – z1)
// Usually expressed in deg C per km.
// Convert altitude difference from meters to kilometers
var heightDiffMeters = z2 – z1;
var heightDiffKm = heightDiffMeters / 1000;
var tempDiff = t2 – t1;
// Calculate Rate: -(change in temp) / (change in height)
// A positive lapse rate means temperature DECREASES with height.
var lapseRate = -(tempDiff) / heightDiffKm;
output.innerText = lapseRate.toFixed(2) + " °C/km";
// Determine stability context
var stabilityText = "";
if (lapseRate 0 && lapseRate = 5 && lapseRate 9.8) {
stabilityText = "Condition: Unstable (Greater than dry adiabatic rate)";
}
status.innerText = stabilityText;
resultBox.style.display = 'block';
}
Understanding Lapse Rate Calculation
In atmospheric science and meteorology, the lapse rate is the rate at which an atmospheric variable, normally temperature, falls with altitude. Calculating the lapse rate is crucial for pilots, meteorologists, and mountaineers to understand atmospheric stability, cloud formation, and potential turbulence.
The Lapse Rate Formula
The environmental lapse rate (ELR) is calculated by measuring the difference in temperature between two different altitudes and dividing it by the difference in height. The formula is typically expressed as:
Γ = – (T2 – T1) / (z2 – z1)
Where:
- Γ (Gamma): The Lapse Rate (°C/km)
- T1: Temperature at the lower altitude (°C)
- T2: Temperature at the higher altitude (°C)
- z1: Lower altitude (converted to km)
- z2: Higher altitude (converted to km)
Interpreting the Results
The standard result is expressed in degrees Celsius per kilometer (°C/km). A positive number indicates that the air gets colder as you go higher, which is the standard behavior of the troposphere.
- Positive Lapse Rate (> 0): Temperature decreases with height. This is normal. The global average is approximately 6.5 °C/km.
- Negative Lapse Rate (< 0): Temperature increases with height. This is known as a Temperature Inversion. Inversions trap pollutants and fog near the ground.
- Zero Lapse Rate: Temperature remains constant with height, known as Isothermal conditions.
Types of Lapse Rates
When analyzing atmospheric stability, your calculated Environmental Lapse Rate (ELR) is often compared to two theoretical constants:
- Dry Adiabatic Lapse Rate (DALR): Approximately 9.8 °C/km. This is the rate at which a parcel of dry air cools as it rises.
- Saturated (Wet) Adiabatic Lapse Rate (SALR): Varies, but typically around 5 °C/km to 9 °C/km. This is the rate for air saturated with moisture (clouds).
If your calculated rate is higher than the DALR (> 9.8 °C/km), the atmosphere is considered unstable, which often leads to the development of thunderstorms. If the rate is low, the air is stable and resists vertical movement.