# WXforum.net

## General Weather/Earth Sciences Topics => Other Weather Topics => Topic started by: attherubicon on March 28, 2021, 09:38:29 PM

Title: Formula for estimating cloud base. Explanation please
Post by: attherubicon on March 28, 2021, 09:38:29 PM
I’v see this formula in several places for estimating the height of cloud bases:

CB ≈ (T - Td)*1000/4.4

I’m puzzled by the 4.4. I would expect a number for the dry adiabatic lapse rate, but Not 4.4
Title: Re: Formula for estimating cloud base. Explanation please
Post by: sky_watcher on March 28, 2021, 09:55:31 PM
I’v see this formula in several places for estimating the height of cloud bases:

CB ≈ (T - Td)*1000/4.4

I’m puzzled by the 4.4. I would expect a number for the dry adiabatic lapse rate, but Not 4.4
From the Cloud Base Calculator site:

Quote from: https://www.omnicalculator.com/physics/cloud-base
The rate at which air cools is estimated at 5.4°F per 1000 feet of altitude. The dew point decreases slower - at about 1.0°F per 1000 feet. That means that per 1000 feet, the spread decreases by 4.4°F.
Title: Re: Formula for estimating cloud base. Explanation please
Post by: attherubicon on March 28, 2021, 09:56:46 PM
Thank you.
Title: Re: Formula for estimating cloud base. Explanation please
Post by: CW2274 on March 28, 2021, 10:16:25 PM
I’v see this formula in several places for estimating the height of cloud bases:

CB ≈ (T - Td)*1000/4.4

I’m puzzled by the 4.4. I would expect a number for the dry adiabatic lapse rate, but Not 4.4
The rate at which air cools is estimated at 5.4°F per 1000 feet of altitude.
Just as an FYI, known as "standard lapse rate".