Calculate the dew point temperature based on current temperature and relative humidity.
Dew Point: — °C
Understanding Dew Point
The dew point is the temperature to which air must be cooled, at constant pressure and water content, to reach saturation (i.e., to the point where water vapor begins to condense and form dew).
Understanding the dew point is crucial in various fields, including meteorology, agriculture, HVAC system design, and industrial processes. It's a more direct indicator of the actual amount of moisture in the air than relative humidity. For instance:
Comfort Level: Higher dew points (above 65°F or 18°C) feel muggy and uncomfortable. Dew points below 55°F (13°C) generally feel comfortable.
Fog and Dew Formation: When the air temperature cools to the dew point, dew or fog can form.
HVAC Systems: Air conditioners work by cooling air below its dew point, removing moisture, and then reheating it to a comfortable temperature.
Agriculture: Dew point influences the risk of frost, dew formation on crops, and potential fungal growth.
How to Calculate Dew Point
There are several formulas to approximate the dew point. A widely used and relatively accurate empirical formula is the Magnus-Tetens approximation. A common form of this formula is:
$$T_d = T – \frac{100 – RH}{5}$$
Where:
T_d is the Dew Point temperature in degrees Celsius (°C).
T is the current air temperature in degrees Celsius (°C).
RH is the current Relative Humidity in percent (%).
This is a simplified version. A more refined version (often referred to as the Arden Buck equation or similar) provides better accuracy across a wider range of temperatures and humidities:
Let T be the temperature in Celsius and RH be the relative humidity in percent.
Note: The accuracy of these formulas depends on atmospheric pressure, which is assumed to be standard sea-level pressure for simplicity. Small variations in pressure have a minor effect on the dew point.
function calculateDewPoint() {
var tempInput = document.getElementById("temperature");
var rhInput = document.getElementById("relativeHumidity");
var resultDiv = document.getElementById("result");
var temperature = parseFloat(tempInput.value);
var relativeHumidity = parseFloat(rhInput.value);
if (isNaN(temperature) || isNaN(relativeHumidity)) {
resultDiv.innerHTML = "Please enter valid numbers.";
resultDiv.style.backgroundColor = "#dc3545"; // Red for error
return;
}
if (relativeHumidity 100) {
resultDiv.innerHTML = "Relative Humidity must be between 0 and 100%.";
resultDiv.style.backgroundColor = "#dc3545"; // Red for error
return;
}
// Arden Buck equation for Dew Point calculation
var a = 17.27;
var b = 237.7;
var gamma = ((a * temperature) / (b + temperature)) + Math.log(relativeHumidity / 100.0);
var dewPoint = (b * gamma) / (a – gamma);
resultDiv.innerHTML = "Dew Point: " + dewPoint.toFixed(1) + " °C";
resultDiv.style.backgroundColor = "var(–success-green)"; // Green for success
}