<p>I want to calculate the Madden-Julian Oscillation (MJO) phase by myself using Real-time Multivariate MJO series 1 (RMM1) and 2 (RMM2) from a data file.</p>
<p>The formula for doing so is:</p>
<p><span class="math-container">$MJO phase = \arctan\left(\frac{RMM2}{RMM1}\right)$</span></p>
<p>but that doesn’t get me to an MJO phase of 1 to 8.</p>
<p>I’ve trawled the web extensively but can’t find a solution.</p>
<p>Thanks in advance.</p>

CC BY-SA 4.0
2022-08-23T08:49:10.007Z
Given that the arctan function yields results ranging from -90 to 90 if you work with degrees, and from $-\pi/2$ to $\pi/2$ if you work with radians, I have a hard time to see how this formula will give you values ranging from 1 to 8. There must be something missing.
Jean-Marie Prival
CC BY-SA 4.0
2022-09-08T20:06:19.263Z
Jean-Marie, Thank you so very much for your response. It helped me refine my search and the answer I needed.
Markela
CC BY-SA 4.0
2022-09-09T07:35:12.267Z
You're welcome, glad it helped! If you found an answer, the best course of action would be to post it below as a self answer, so that people who would encounter the same problem in the future could find it. Now the question is closed, so you can't post an answer, but I've voted for reopening, let's see how it goes...
Jean-Marie Prival
<meteorology><climate>
How do I calculate the Madden-Julian Oscillation (MJO) phase from RMM1 & RMM2?
Markela
# How do I calculate the Madden-Julian Oscillation (MJO) phase from RMM1 & RMM2?

(Asked by: username_0 on 2022-08-19)

I want to calculate the Madden-Julian Oscillation (MJO) phase by myself using Real-time Multivariate MJO series 1 (RMM1) and 2 (RMM2) from a data file.

The formula for doing so is:

$MJO phase = \arctan\left(\frac{RMM2}{RMM1}\right)$

but that doesn’t get me to an MJO phase of 1 to 8.

I’ve trawled the web extensively but can’t find a solution.

Thanks in advance.

**Tags:** meteorology, climate

> **Comments:**
> **username_1**: Given that the arctan function yields results ranging from -90 to 90 if you work with degrees, and from $-\pi/2$ to $\pi/2$ if you work with radians, I have a hard time to see how this formula will give you values ranging from 1 to 8. There must be something missing.  
> **username_0**: username_1, Thank you so very much for your response. It helped me refine my search and the answer I needed.  
> **username_1**: You're welcome, glad it helped! If you found an answer, the best course of action would be to post it below as a self answer, so that people who would encounter the same problem in the future could find it. Now the question is closed, so you can't post an answer, but I've voted for reopening, let's see how it goes...  

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## 0 answers

