<p>Under a hydrostatic assumption the basic equation is <code>p=/rho R T</code>. So under this easy equation the pressure depends to the air density and the air temperature. As you may know diabatic processes during rain yield to a decreasing temperature. but the magnitude in change of pressure against the synoptic scale forcing is low. </p>

<p>Please be aware of mixing stuff together answering this questions. The question was not to answer how precipitation is forming. It was just the question about the rain influencing the pressure. </p>

CC BY-SA 4.0
2019-08-29T17:45:14.460Z
2019-08-29T17:45:14.460Z
dl.meteo
<p>No. Low pressure affects the rain, not the other way around. Air at high pressure/density can hold more moisture than air at low pressure, so when there is a reduction in pressure the moisture content, or some of it, condenses and is precipitated. Reduction of temperature can also cause precipitation, because cold air holds less moisture than warm air. Reduction of temperature can be brought about by lowering of pressure.</p>

CC BY-SA 4.0
2019-08-27T06:33:23.890Z
Until now I never heard of the pressure being a significant influence on the moisture capacity of the air. Could you please elaborate sufficiently? As far as I know, low pressure systems are connected with rainfall due to the lower temperatures compared to high pressure systems, which leads to the forming of clouds as the air cools and excessive moisture being rained down.
Erik
CC BY-SA 4.0
2019-08-27T06:51:52.447Z
@ Erik  Just as increasing the pressure of air has a warming effect, reducing the pressure has a cooling effect, so both pressure and temperature influence condensation.
Michael Walsby
CC BY-SA 4.0
2019-08-27T06:53:35.367Z
Please, hit me with the calculations, that this is a significant effect.
Erik
CC BY-SA 4.0
2019-08-27T07:09:11.430Z
*"Just as increasing the pressure of air has a warming effect"* I think it's the other way around, Michael. Temperature fluctuations cause pressure fluctuations, not the other way around.
arkon
CC BY-SA 4.0
2019-08-27T07:19:38.563Z
You're right, but I think both mechanisms operate. Changes in pressure affect temperature and changes in temperature affect pressure.
Michael Walsby
CC BY-SA 4.0
2019-09-04T14:24:05.033Z
Just take a look to hydrostatic equation. It is a linear correlation between pressure density and air temperature.
dl.meteo
CC BY-SA 4.0
2019-08-27T06:20:06.330Z
2019-08-27T06:59:43.283Z
2019-08-27T06:59:43.283Z
Michael Walsby
<p>I understand how and why low pressure systems are often associated with rain, but does the rain itself (both during and after) alter barometric pressure in any meaningful way?</p>

CC BY-SA 4.0
2019-08-29T16:28:39.053Z
@gansub Thanks for that link. My hunch was that it must have *some* impact, since relative humidity increases after a rain which I assumed would alter the air density and pressure.
arkon
<meteorology>
Does rain itself affect barometric pressure?
arkon
# Does rain itself affect barometric pressure?

(Asked by: username_0 on 2019-08-27)

I understand how and why low pressure systems are often associated with rain, but does the rain itself (both during and after) alter barometric pressure in any meaningful way?

**Tags:** meteorology

> **Comments:**
> **username_0**: @gansub Thanks for that link. My hunch was that it must have *some* impact, since relative humidity increases after a rain which I assumed would alter the air density and pressure.  

---

## 2 answers

### Answer by username_1 on 2019-08-29. Score: 1

Under a hydrostatic assumption the basic equation is `p=/rho R T`. So under this easy equation the pressure depends to the air density and the air temperature. As you may know diabatic processes during rain yield to a decreasing temperature. but the magnitude in change of pressure against the synoptic scale forcing is low.

Please be aware of mixing stuff together answering this questions. The question was not to answer how precipitation is forming. It was just the question about the rain influencing the pressure.


---

### Answer by username_2 on 2019-08-27. Score: 0

No. Low pressure affects the rain, not the other way around. Air at high pressure/density can hold more moisture than air at low pressure, so when there is a reduction in pressure the moisture content, or some of it, condenses and is precipitated. Reduction of temperature can also cause precipitation, because cold air holds less moisture than warm air. Reduction of temperature can be brought about by lowering of pressure.

> **Comments:**
> **username_3**: Until now I never heard of the pressure being a significant influence on the moisture capacity of the air. Could you please elaborate sufficiently? As far as I know, low pressure systems are connected with rainfall due to the lower temperatures compared to high pressure systems, which leads to the forming of clouds as the air cools and excessive moisture being rained down.  
> **username_2**: @ username_3  Just as increasing the pressure of air has a warming effect, reducing the pressure has a cooling effect, so both pressure and temperature influence condensation.  
> **username_3**: Please, hit me with the calculations, that this is a significant effect.  
> **username_0**: *"Just as increasing the pressure of air has a warming effect"* I think it's the other way around, username_2. Temperature fluctuations cause pressure fluctuations, not the other way around.  
> **username_2**: You're right, but I think both mechanisms operate. Changes in pressure affect temperature and changes in temperature affect pressure.  
> **username_1**: Just take a look to hydrostatic equation. It is a linear correlation between pressure density and air temperature.  

---

