<p>The absolute accuracy for GOES-13 visible channel is 5%, so 2% is well within the noise. <a href="http://noaasis.noaa.gov/NOAASIS/ml/imager.html" rel="nofollow">http://noaasis.noaa.gov/NOAASIS/ml/imager.html</a></p>

CC BY-SA 3.0
2016-04-11T03:57:00.417Z
2016-04-11T03:57:00.417Z
kwknowles
<p>In the GOES-13 Visible channel, there seems to be a morning/afternoon asymmetry in the data. I'm wondering what might cause this. </p>

<p>In this example data, the morning is the lower branch, and the afternoon is the upper branch. The y-axis is the pixel level (0..255), the x-axis is the Sun's local altitude above the horizon. The location is the Gulf of St. Lawrence, on the east coast of Canada. </p>

<p>Latitude +46.94N, longitude -63.21W (not far from the center of the images below.)</p>

<p><img src="https://i.sstatic.net/0LhDf.png" alt="GOES Visible Channel"></p>

<p>Morning, 10am local time:
<img src="https://i.sstatic.net/rOyca.png" alt="Morning, 10am local time"></p>

<p>Afternoon, 4pm local time:
<img src="https://i.sstatic.net/SVIhq.png" alt="enter image description here"></p>

CC BY-SA 3.0
2014-09-26T15:47:45.403Z
It is hard to say based only on this figure. It could be sun reflection of the water surface or difference in cloud water in the atmosphere. Could you include two visible snapshots - one from the morning and one from the afternoon?
milancurcic
CC BY-SA 3.0
2014-09-26T16:35:25.147Z
Changes made...
John
CC BY-SA 3.0
2014-09-26T16:50:28.193Z
The difference is very subtle, around 2% based on the scatter above. I would recommend looking for the persistence of the behavior over a longer period of time (say, last month or so). If the amplitude of the difference varies from day to day, the effect could be atmospheric (water vapor/droplets).
milancurcic
<remote-sensing>
GOES Visible Channel - asymmetry between morning and afternoon
John
# GOES Visible Channel - asymmetry between morning and afternoon

(Asked by: username_0 on 2014-09-26)

In the GOES-13 Visible channel, there seems to be a morning/afternoon asymmetry in the data. I'm wondering what might cause this.

In this example data, the morning is the lower branch, and the afternoon is the upper branch. The y-axis is the pixel level (0..255), the x-axis is the Sun's local altitude above the horizon. The location is the Gulf of St. Lawrence, on the east coast of Canada.

Latitude +46.94N, longitude -63.21W (not far from the center of the images below.)

![GOES Visible Channel](https://i.sstatic.net/0LhDf.png)

Morning, 10am local time:
![Morning, 10am local time](https://i.sstatic.net/rOyca.png)

Afternoon, 4pm local time:
![enter image description here](https://i.sstatic.net/SVIhq.png)

**Tags:** remote-sensing

> **Comments:**
> **username_1**: It is hard to say based only on this figure. It could be sun reflection of the water surface or difference in cloud water in the atmosphere. Could you include two visible snapshots - one from the morning and one from the afternoon?  
> **username_0**: Changes made...  
> **username_1**: The difference is very subtle, around 2% based on the scatter above. I would recommend looking for the persistence of the behavior over a longer period of time (say, last month or so). If the amplitude of the difference varies from day to day, the effect could be atmospheric (water vapor/droplets).  

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## 1 answers

### Answer by username_2 on 2016-04-11. Score: 3

The absolute accuracy for GOES-13 visible channel is 5%, so 2% is well within the noise. <http://noaasis.noaa.gov/NOAASIS/ml/imager.html>


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