<p>On the east side of the Pacific Ocean, there are cold currents coming the poles going towards the equator. The cold currents makes it so there is almost a permanent cold air mass above the eastern portion of the ocean. As warmer air is blown over this colder air, it must go above the colder air. The warmer air expands, temperature decreases, becomes saturated and the stratus clouds form!</p>

<p>The cold currents are there because of the semi-permanent high pressure system in the mid-latitudes of the ocean. The winds are equator-ward on the east side of high pressure systems. This drives the ocean currents to be equator-ward on the east side of the ocean.</p>

CC BY-SA 3.0
2014-07-23T16:55:25.580Z
How would you then explain the feature in the middle of Australia, [supposedly a desert](https://en.wikipedia.org/wiki/File:Australia-climate-map_MJC01.png)? Part of it is the [Simpson Desert](https://en.wikipedia.org/wiki/Simpson_Desert).
Peter Mortensen
CC BY-SA 3.0
2014-07-17T17:32:42.933Z
2014-07-17T19:57:27.913Z
2014-07-17T19:57:27.913Z
Matthew
<p>They can be seen in the diagram below (of the CERES radiation dataset - supposedly they contribute a lot to the total variance in net radiation, which is the sum of SW and LW) - just west of Peru and Mexico (my supervisor, Dargan Frierson, said these are stratocumulus regions). I'm just wondering - why are stratocumulus clouds so abundant there?</p>

<p>(the diagram is taken after taking the 12-month running mean of the dataset, which smoothes out a lot of features).</p>

<p><img src="https://i.sstatic.net/wguOB.jpg" alt="enter image description here"></p>

CC BY-SA 3.0
2016-05-08T13:41:35.783Z
Any update on the sources and date information?
Peter Mortensen
CC BY-SA 3.0
2014-07-23T16:52:09.440Z
What year is the 12-month running mean from?
Peter Mortensen
CC BY-SA 3.0
2014-08-28T22:02:28.137Z
2011? 2012? 2013? 2014?
Peter Mortensen
CC BY-SA 3.0
2014-11-20T22:02:22.233Z
What year is it from?
Peter Mortensen
CC BY-SA 3.0
2014-11-20T22:03:48.157Z
Or even better, a source for the data/image.
Peter Mortensen
<atmosphere>
Why is the eastern Pacific full of stratocumulus clouds, and why do they have so much variation in net radiation?
InquilineKea
# Why is the eastern Pacific full of stratocumulus clouds, and why do they have so much variation in net radiation?

(Asked by: username_0 on 2014-05-22)

They can be seen in the diagram below (of the CERES radiation dataset - supposedly they contribute a lot to the total variance in net radiation, which is the sum of SW and LW) - just west of Peru and Mexico (my supervisor, Dargan Frierson, said these are stratocumulus regions). I'm just wondering - why are stratocumulus clouds so abundant there?

(the diagram is taken after taking the 12-month running mean of the dataset, which smoothes out a lot of features).

![enter image description here](https://i.sstatic.net/wguOB.jpg)

**Tags:** atmosphere

> **Comments:**
> **username_1**: What year is the 12-month running mean from?  
> **username_1**: 2011? 2012? 2013? 2014?  
> **username_1**: What year is it from?  
> **username_1**: Or even better, a source for the data/image.  
> **username_1**: Any update on the sources and date information?  

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## 1 answers

### Answer by username_2 on 2014-07-17. Score: 4 | Accepted answer

On the east side of the Pacific Ocean, there are cold currents coming the poles going towards the equator. The cold currents makes it so there is almost a permanent cold air mass above the eastern portion of the ocean. As warmer air is blown over this colder air, it must go above the colder air. The warmer air expands, temperature decreases, becomes saturated and the stratus clouds form!

The cold currents are there because of the semi-permanent high pressure system in the mid-latitudes of the ocean. The winds are equator-ward on the east side of high pressure systems. This drives the ocean currents to be equator-ward on the east side of the ocean.

> **Comments:**
> **username_1**: How would you then explain the feature in the middle of Australia, [supposedly a desert](https://en.wikipedia.org/wiki/File:Australia-climate-map_MJC01.png)? Part of it is the [Simpson Desert](https://en.wikipedia.org/wiki/Simpson_Desert).  

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