Yes, you read the title correctly. We have 3D visible imagery from the GOES-16/17 satellites in the Advanced Weather Interactive Processing System (AWIPS) at the Weather Forecast Office in Huntsville! So, how did we do this? I’ll explain.
Several days ago, Kevin McGrath at NASA SPoRT created Facebook and Twitter posts detailing the capability of generating 3D imagery when using both the GOES-16 and GOES-17 satellites in one image. This is made possible by taking advantage of the slightly different viewing angles by the two satellites in their current GOES East and Center positions. Yesterday, we explored the possibility of doing this in AWIPS here at the Huntsville WFO and were successful. I’ll tell you how we did it (which is actually not that difficult), but first I’ll show some 3D imagery from around the Southeast U.S. region this morning. By the way, to view the imagery in its full 3D glory, you’ll need some standard red/cyan 3D glasses. Let us also add that the original imagery appears much better in AWIPS as there is always some loss of fidelity when generating images in .gifs and then transferring and viewing these from other platforms. Anyway, hopefully you’ll get a good sense of the 3D aspects contained within the image loops, and I’ll add it’s better to view with your screen brightness turned up and under darker ambient conditions.
Image 1. GOES-16/17 3D Visible image loop (0.64 µm), 1307-1442 UTC, 14 Sep 2018
Next, we’ll take a closer look at some of these cloud scenes. First, here’s a look at Hurricane Florence as it churns along the N. Carolina coast. You may notice (as we did) that it is much easier to observe the differential motion and distinguish among the various cloud layers in this type of imagery. Unfortunately, some of the image fidelity is lost when saving as a .gif, as observed particularly in the cirrus cloud layer in the image loop.
Image 2. GOES-16/17 3D visible image loop (0.64 µm) of Hurricane Florence, 1317-1452 UTC, 14 Sep 2018
It is rather extraordinary to view developing convection in 3D. This convective cloud scene in the NW Gulf of Mexico details this capability well (Image 3).
Image 3. GOES-16/17 3D visible image loop (0.64 µm) centered over the NW Gulf of Mexico, 1317-1452 UTC, 14 Sep 2018
This next cloud scene is not as active, however, it is interesting how one can get a sense of the differences in cloud depth between the fog hugging some of the southern Appalachian valleys and the outer cirrus band extending far west of Hurricane Florence.
Image 4. GOES-16/17 3D visible image loop (0.64 µm) centered over the Southern Appalachian region, 1222-1357 UTC, 14 Sep 2018
Lastly, to demonstrate the advantage of this type of imagery, we thought we’d show a simple GOES-16 visible loop (Image 5) compared to a 3D visible loop (Image 6).
Image 5. GOES-16 Visible image loop (0.64 µm) centered over south TX, 1447-1627 UTC 14 Sep 2018
Image 6. GOES-16/17 3D visible image loop (0.64 µm) centered over south TX,
Now, you may notice a lack of “brightness” in the 3D imagery, which is due to the layering process. But, perhaps you can get a better sense of the complex layered cloud scene over southern portions of TX in the 3D loop as we did. Of course, as stated previously, there’s generally something lost in translation when moving and viewing graphics between various screens and viewing platforms.
So, now to answer the question…how did we do this? Well, it was somewhat simple actually. As you can see in the images, the GOES-17 image is layered on top and GOES-16 on the bottom. Now, it doesn’t actually matter which satellite image is layered on top. But, whichever one that is, it will need to be set to 50% transparency. Then, we modified the color map in AWIPS, applying a pure black to red color curve for the GOES-17 reflectivity values, and black to cyan (or equal contributions of blue and green) for GOES-16. When doing this initially, we used a simple linear stretch to the color map. However, we realized a more appropriate methodology utilizes the default non-linear ABI VIS gray scale color map. So, we simply modified that color map by changing all of the blue and green color values to 0.0, saving this as a new color map and applying this to GOES-17 imagery. Taking the original color map again, we changed all of the red color values to 0.0 for the GOES-16 imagery. Voila! When viewing through the standard red (left eye), cyan (right eye) 3D colored glasses, the left and right eye will see the two GOES images from their respective viewing angles and the imagery appears in 3D.
The lingering question may be…so this is cool and all, but what is the application? As suggested, this type of imagery does offer a more realistic depiction of the atmosphere and helps to differentiate different cloud layers. Sure, there are some fantastic RGBs now that can aid in this too. But, this is another tool in the forecaster toolbox, so to speak. Additionally, I noticed yesterday and today that it is easier to get a sense of shear in tilted convective updrafts, and when speaking with forecasters at the WFO here, it helps provide them a more thorough and realistic conceptual model of the troposphere. So, these are some things to consider. We’ll be exploring more use of this imagery over the coming days/weeks. The are some caveats to all of this. First, people with significant red/green color deficiencies may not be able to view the 3D imagery as intended. Second…we don’t know if this will still work once GOES-17 gets shifted to its eventual GOES-West position later this year. There may be too great of a difference in the viewing angles. A quick inspection of GOES-15/16 imagery using this same format seemed to indicate an issue there. We’ll see. Anyway, for now, this is a fascinating way to view the visible cloud scene.
-Kris White & Kevin McGrath