If you tap on the graph for the rain rate you’ll see those bars actually represent the “state” of the rain; light, medium, heavy, etc. The bars don’t correspond to the actual in/hr rates but simply what the system classified as “heavy” or “light” rain which is why they’re constant. The line in the graph is the cumulative qpf. Hope that helps!
Yes, I know. Many of us went through the same thing. What we have to remember is that WF is targeting a market that arent meteorologists, scientists, engineers, mathematicians, etc. I personally would like the actual rain rate graphed rather than a binned value, but then I have to remember that my Physics degree takes me out of the main target market.
I’m think you guys are obviously right, but then David’s explanation of the graph was in error when he explained to an owner:
“The left axis scale applies to both values, but you need to add “per hour” to the rate data. The time period that applies to the blue bar (rate) changes based on zoom level: 1 minute, 5 minute, 30 minute, 3 hour, 1 day. In general the further you zoom in the higher the individual rate values will be, since there is more averaging as you zoom out. Note that when you zoom all the way out, to the 1 day per time step graph, the blue bar (average rate) is not shown"
It’s that explanation that threw me because, as you guys are saying, the axis scale on the left does not apply to both values, only total rain accumulation, not rain rate. I think new owners are going to be thrown by that if they read it as I did.
Since last night, after our storm passed and a strong cold front went through, I seem to have a new issue. Previously my Sky was reporting winds that were generally higher, but very reasonably so, than my VP2 (my Sky is in the same area, but a bit higher than the VP2 anemometer). At that point things looked great. Of course this doesn’t take into account the issue I previously mentioned when Sky was reporting wind gusts of 30mph when winds were very light during the rain. I think that might have been the water ponding issue, below Sky’s sensors, some have discussed before.
Last night winds in our area were very strong with the onset of cold air advection. Yet my Sky was reporting light winds while my Davis was correctly reporting much higher wind velocities. So during and subsequent to the rain, my Sky seemed confused, reporting high winds when there were none (water ponding for several hours during the rain?) and now reporting very light winds when they’re actually significantly higher. The latter issue is continuing this morning.
Hopefully this can be corrected during the calibration process, but right now it really seems off.
The other thing I’ve noticed is that with large changes in barometric pressure and humidity as we experienced prior to and after the storm, the Air lagged actual readings by a number of hours. Sky’s barometric pressure and humidity took about 5 hours to catch up with actual readings that were displayed on my VP2 and NWS locations hours before.
I wonder if the issue with lagging barometric pressure is the result of the Air being located outside. Typically we have our barometers located inside at a relatively constant temperature. The lagging humidity I’m not sure.
Sorry to relate all these issues, but as a new owner I guess I’m at the beginning of a learning curve…or is it my Sky & Air that’s at the beginning of that curve.
The latter applies the grouping of “descriptive” intensity rates into categories with a strong bias towards users in temperate areas. This suggests a worldview of uniformity and linearity in nature that doesn’t exist.
Rainfall intensities in the humid tropics are significantly higher than in temperate areas and require different groupings. Likewise, rainfall rates in semi-arid regions are much lower.
Applying the temperate standard globally means that a significant proportion of rainfall events in, say, the humid tropics will fall into the very heavy and extreme categories. It beats me how this is helping “the average user”…
Since the categories defined aren’t universally applicable, it would be better to use the actual rain rates and show the values on a second y-axis.
To guide “the average user” in their interpretation, categories suitable for other regions (e.g. the humid tropics and semi-arid conditions) should be added to the existing temperate groupings.
See also the discussion in Change in graphing rain rate
Now that explains it perfectly, pachuquear, thanks. I kept seeing that outdated definition. David updated his post. Thanks much!
Now I just need to get my wind speeds sorted out.
I’m curious if others tend to get a long lag with between actual barometric pressure & humidity changes vs when those changes actually settle down on their Air units.
I wanted to include a screenshot of my data during the rain we had yesterday. Winds were very light, yet I got a number of high gusts in the area of 30 and above. As I described above, there definitely were no gusts like that in our area. PWS & NWS stations did not show any such data nor did my VP2 which is mounted about 1’ from the WF station at about the same height. I wonder if this isn’t the rain on plate phenomena.
Today my problem is the reverse, frequent high wind gusts in actuality, but my WF is not recording that. My Davis seems to be showing wind speeds 30-40% above what my Sky unit is showing.
- When I have wild readings in strength and direction following moist conditions I can be pretty certain it is moisture bubbles or similar at the wind sensors. It is a well known problem they are working on with coating experiments. We must be patient with that.
History is here: https://community.weatherflow.com/t/can-rain-affect-wind-readings-looks-like-frost-can-as-well-updated/2252
- When viewing and displaying wind graphs we get a more accurate idea if it is zoomed into maximum 1 min scale. And if you hover the cursor over a point on the graph we can read the scale.
- If we include our station number others can go in and examine the data in more detail.
This is how I highlight my scale and readings I might be concerned about:
Thanks much, Ian! I kind of assumed the issue was the ponding of water, but it’s good to hear you confirm that. This morning I noticed frost on the surface too with our single digit temps, so it makes sense that this too can mess with the winds. Has anyone tried a coating of car wax? I’d think that would make the surface quite slick. I’m not sure if that would prevent frost buildup or dew (although dew often occurs with light or calm winds, so the wind accuracy impact might be moot in many cases), but I wonder if it would make it less likely for water droplets to hang around in a rain event. Maybe we need a drain hole!
Ian, have you noticed the issue I mentioned with a long lag time for humidity and pressure to stabilize after significantly large changes, like some frontal passages? My Davis settled down much more quickly. It took the Air hours to settle in after my VP2. The VP2 has 24/7 fan aspiration, so I assume that played a role. Since the barometer is indoors and not subject to temperature change, I’d assume that might impact that measurement too.
One fascinating thing I noticed today was the impact on wind velocities as I rotated the pole my Sky sits on. When I rotated it 90-180 degrees from the correct N orientation, my wind speeds increased somewhat. It seemed as if the sensors preferred a different orientation which wasn’t correct in terms of wind direction. Weird. I eventually brought it back to the correct orientation at the sacrifice of some wind speed, hoping a calibration would eventually fix this.
BTW, my station # is 6187. Thanks again.
There are several tests going on with different coatings. I put R1 coatings (a hydrophobic ceramic nano-coating) on one of mine and it sometimes helps and sometimes hurts. There are times my stock one does better and times the coated one does better. For example, here is a polar wind graph of the one with the R1 coating. Everything was normal until around 1900 when the wind direction shown changed nearly 180 degrees. My other stations indicated that the wind was still from the SSW direction. When I inspected the unit I noticed that there was a water droplet on the S sensor and a small one on the E sensor besides several on the reflecting plate. After cleaning off just the droplets on the sensors, leaving the ones on the reflector plate, you can see that next few directions were back in the SSW direction, in line with the actual wind direction.
Here are links to the topics that discuss your questions:
I have not witnessed or read about anyone having a delay with their pressure reading. But I believe it does adjust itself to your local area so it may have been calibrating itself.
Many questions and answers have been discussed in this forum with no easy way to find a complete FAQ. Because this station is continually evolving and changing, even your own station will be automatically updated and calibrations will change and you wouldnt know it unless you read it here somewhere. I use the search bar a lot to find things out.
Gizmoev, in the case you cite, the issue seems to be less with the flat area under the sensors as opposed to water collection on the sensors themselves. I wonder if that was the causative factor in my increased wind velocities as I rotated the Sky unit’s mounting. I looked at the flat area and it was clean (I had previously cleaned it), but I didn’t focus on the sensors themselves. I wonder how the pricey units deal with this?
It would seem that no matter how slick the flat area is, unless something is changed to the sensors themselves, the example you gave will continue.
Ian, thanks much. I have tried using the search tool, but it often didn’t come up with the answers. I’ll definitely dig into your links.
Welcome @vidguy7 . Great to have another met / scientist aboard. You’re in very good and helpful company here with the other owners. A few observation which may or may not have been addressed:
when viewing graphs, make sure to zoom into the 1min resolution to see the finest data. See Data archive buckets explained.
Rotate your phone to landscape when viewing graphs.
Your observed issue with wind spikes during rain events is due to drops in the sonic path. We are experimenting with various coatings. So far the super hydrophobic nano-particle varieties are performing the best. Many of the pricey sonic anemometers use similar. We’ll solve it, have patience.
To ensure data integrity across the entire network, we believe in in-situ calibration and ongoing dynamic QC. To that end, we have/are deploying a Continuous Learning (CL) system for various parameters. In short, we compare data from your station to reference data sources in your immediate area and apply daily calibrations when warranted. For example see CL for Humidity explained As of 23 Jan, your station has received an initial calibration for Humidity on 23Jan. The system is still collecting and certifying comparison data for Pressure, UV, and Rain before initial corrections are applied.
We’re glad you found us. Welcome.
PS - Make sure to read this regarding wind : initial sensor balance routines…which would explain your rotation on the pole description. SKY: wind sensor initial self balancing
Thanks much for this info, you guys are great!
WF staff, is there a set time of day that calibrations are applied, if necessary?
It varies dependent on run times, comparison data availability, modeling, etc, etc. Humidity, Pressure, and UV are now run daily. Rain will likely run hourly in CONUS to start. After the first couple calibrations, the subsequent tweaks become more and more subtle.
I have noticed similar behavior with the graphs but found that at least sometimes it seems to be a function of granularity. Some of the numbers change significantly when you zoom in or zoom out in the graph. As I zoom in deeper, the graph gets ever closer to the raw numbers.