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ADS-B and smog?

KatieB

KatieB

Well Known Member
My father-in-law and I flew up to Kentucky to pick up a plane this morning. We were cruising about 5500 feet past Nashville and he says, "Hey did you check weather?" I said, "Well yeah, it's supposed to be clear til this afternoon when the thunderstorms build up." Then he shows me this on the G3X Touch radar screen and says, "What the heck!" Looked like light to moderate rain covering the Nashville area... but the other picture is the view out the window in that direction. The METARs we got in the area all showed clear below 12,000 and good visibility.

There is an Air Quality Alert today, with a defined haze layer and a fair amount of smog. Would smog show up as moderate rain on ADS-B?

29369777095_03a1071970_b.jpg
[/url]2016-08-31_04-31-26 by jabiruchick, on Flickr[/IMG]

29336019396_1459b4e10c_b.jpg
[/url]2016-08-31_04-31-58 by jabiruchick, on Flickr[/IMG]
 
I'm not sure about smog, but I know that on a recent flight past Savannah my ADS-B showed some nasty (red) cells in the area, where myself and other pilots all saw nothing but some low fluffy clouds. I brought it up with ATC and the controller said he was seeing it on his screen as well for the last hour but multiple PIREPS indicated nothing in the area. He said it may have something to do with the amount of moisture in the air or clouds, but he wasn't very sure. I am used to the radar being a bit inaccurate due to fast moving and changing Florida weather, but never seen it be that off, and apparently for an hour or more.

Chris
 
Seen it here lately

I'm in Hopkinsville, KY and I have seen green and some yellow lately around here and nothing is out there. I've seen it at other times in the past also.
 
Same thing about 2weeks ago off the coast of San Pedro. ADSB showing lots of yellow in clear conditions.
 
Don't play "You bet your life" with it.

We were flying from St. Simons island northbound last Friday and our ADSB showed red and magenta cells just off the coast and it was CAVU. Not little cells either, 15 to 20 miles across.

Sure makes you wonder when it wn't show stuff that's really there. Just another lesson on how NOT to use it when IMC n convective areas.
 
The weather radar NEXRAD has two modes; clear air and precipitation. Sometimes in the clear air mode it will pick up just about anything in the radar return and present it as precipitation. I've seen it many times where the map has a big light green blob or streaks on it, and the air is mostly clear, maybe a whisp of moisture or maybe even smoke/smog. When it gets darker green or yellow, then maybe there might be something there weatherwise.
 
I've seen XM NEXRAD show yellow when flying into forest fire smoke (visibility maybe 7-8 miles). Strangely, later in the same flight visibility in smoke was down to 3-4 miles, but XM showed nothing.
 
bruceh said:
The weather radar NEXRAD has two modes; clear air and precipitation. Sometimes in the clear air mode it will pick up just about anything in the radar return and present it as precipitation. I've seen it many times where the map has a big light green blob or streaks on it, and the air is mostly clear, maybe a whisp of moisture or maybe even smoke/smog. When it gets darker green or yellow, then maybe there might be something there weatherwise.
Click to expand...

So in 2017 this may change. This is from the NEXRAD Wikipedia you linked, Upcoming 2017 VCP changes[edit]

In October, 2015, the National Weather Service announced[9] that an upcoming software update would eliminate multiple precipitation mode VCPs, and replace them with a single VCP intended to combine the best features of the VCPs being eliminated. An additional clear air mode will also be made available.
 
Interesting..... I'll see if it's doing anything similar Friday morning.

I should be landing in Shelbyville for fuel at 8:00am or so. SYI is about our halfway point heading south. It's also about the right amount time for restroom breaks for the wife, daughter, and dog. We'll be passing back through the other direction on Monday.
 
rleffler said:
Interesting..... I'll see if it's doing anything similar Friday morning.

I should be landing in Shelbyville for fuel at 8:00am or so. SYI is about our halfway point heading south. It's also about the right amount time for restroom breaks for the wife, daughter, and dog. We'll be passing back through the other direction on Monday.
Click to expand...

That's funny-- I should be fueling up the Jabiru about 8 tomorrow to head north to Wisconsin for the weekend! Maybe I'll see you on the ramp! :p

I've been doing a lot of VFR cross-country flying around TN-KY-IN-IL-MO this summer, and the weather pattern has blessed (cursed?) me with air-mass thunderstorms every time. Sometimes I am amazed at how accurate this FIS-B weather presentation is, and other times I am just baffled at how wrong it is. You absolutely need a visual confirmation to locate areas of precipitation-- Like Widget said, I would never, ever trust it enough to go around thunderstorms embedded in clouds if I were in IMC.

BUT-- When I fly a plane that doesn't have ADS-B or XM weather in this type of weather pattern, I feel handicapped. I like being able to look at METARs along my general direction of flight (all are time-stamped). When conditions can change so fast, it's a great tool if you know and respect its limitations.
 
looks typical

KatieB said:
My father-in-law and I flew up to Kentucky to pick up a plane this morning. We were cruising about 5500 feet past Nashville and he says, "Hey did you check weather?" I said, "Well yeah, it's supposed to be clear til this afternoon when the thunderstorms build up." Then he shows me this on the G3X Touch radar screen and says, "What the heck!" Looked like light to moderate rain covering the Nashville area... but the other picture is the view out the window in that direction. The METARs we got in the area all showed clear below 12,000 and good visibility.

There is an Air Quality Alert today, with a defined haze layer and a fair amount of smog. Would smog show up as moderate rain on ADS-B?

29369777095_03a1071970_b.jpg
[/url]2016-08-31_04-31-26 by jabiruchick, on Flickr[/IMG]

29336019396_1459b4e10c_b.jpg
[/url]2016-08-31_04-31-58 by jabiruchick, on Flickr[/IMG]
Click to expand...

The air is cleaner where you live, yet this looks like a very typical day in the DC area.
No distinct horizon. This is what can be expected all summer here.
Daddy man
 
KatieB said:
That's funny-- I should be fueling up the Jabiru about 8 tomorrow to head north to Wisconsin for the weekend! Maybe I'll see you on the ramp! :p

I've been doing a lot of VFR cross-country flying around TN-KY-IN-IL-MO this summer, and the weather pattern has blessed (cursed?) me with air-mass thunderstorms every time. Sometimes I am amazed at how accurate this FIS-B weather presentation is, and other times I am just baffled at how wrong it is. You absolutely need a visual confirmation to locate areas of precipitation-- Like Widget said, I would never, ever trust it enough to go around thunderstorms embedded in clouds if I were in IMC.

BUT-- When I fly a plane that doesn't have ADS-B or XM weather in this type of weather pattern, I feel handicapped. I like being able to look at METARs along my general direction of flight (all are time-stamped). When conditions can change so fast, it's a great tool if you know and respect its limitations.
Click to expand...

I have not used it much for real weather avoidance, except my trip to OSH. I decided to divert around a relatively small green sounding on the foreflight map (via ADSB) near Madison. Just as the map shows me passing by it several miles away, the sky becomes dark and rain appears (of course there was no cloud on my right where my map said it was). What's interesting, is that the clouds were moving from West to East and I was passing directly South of it's location on the map, so it wasn't a timing/delay issue; simply bad coordinates data in the Nexrad interface. Made me think twice about ever using it to dodge significant weather.

Larry
 
Y'all be careful using NEXRAD for tactical decision making. The info is anywhere from approx 6-15 min old regardless of the transmission mode (XM or ADS-B). This is because it takes the NEXRAD site 5 min to complete its airspace scan. You then have to add on top of that the time it takes for the providers to get the image and transmit it: 1-2 min best case, but could be more depending on the update cycle. Bottom line take the NEXRAD image with a grain a salt, especially if you're in IMC.
 
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Auburntsts said:
Y'all be careful using NEXRAD for tactical decision making. The info is anywhere from approx 6-15 min old regardless of the transmission mode (XM or ADS-B). This is because it takes the NEXRAD side 5 min to complete its airspace scan. You then have to add on top of that the time it takes for the providers to get the image and transmit it: 1-2 min best case, but could be more depending on the update cycle. Bottom line take the NEXRAD image with a grain a salt, especially if you're in IMC.
Click to expand...

Good point-- the image says it's only 1 or 2 minutes old, but that's the time your box received the packet, not the time of the radar sweep.
 
Same here

Hi Katie,
I flew the Highlander over to Wisconsin on Monday afternoon. The Radar was showing large areas of light green, green and some yellow. It was a hazy day but I never saw any weather on the flight. My friend picked me up in Door County and we had the same light green through Yellow on the display but nothing actual.

First time I really remember that much on the radar including large areas of yellow with nothing actual.

Gary
 
Like a low cost miracle

Just a point of reference from out west. Our weather people call it the monsoon season. Pilots living where they actually have a monsoon would laugh... but anyway.
With multiple T storm buildups for several weeks now... I have seen the accuracy of ADS-B. It is perfectly fine for avoidance. The movement, size and intensity has been remarkably accurate for us in AZ, CA UT, NV. etc.
It is a tool I won't fly without now. I keep a Garmin GDL39 and 696 in a bag with a battery. Took a C210 to Palm Springs this week and used the WX and traffice the whole way... there and back. Funny think I noticed though... the GMX 200 shows terrain with exactly the same colors as NEXRAD. Garmin did not think that one through very well back when MX20 and 200's were being coded. For a few moments I was trying to figure out why severe T storms were on the GMX200 and not on ADS-B. Then I could see it was high terrain around Flagstaff. I learn something every flight.
 
KatieB said:
Would smog show up as moderate rain on ADS-B?
Click to expand...
I had the opposite problem over Tennessee last year. The ADS-B showed nothing, but I flew into a huge cloud of smoke from Canadian wildfires at 10,000'. I was basically IFR for about 30 minutes.
 
KatieB said:
That's funny-- I should be fueling up the Jabiru about 8 tomorrow to head north to Wisconsin for the weekend! Maybe I'll see you on the ramp! :p .
Click to expand...

We didn't get in about 8:30 due to a late start. I suspect you were long gone by the time we got there. It took us 30 minutes to find the FBO staff to get fuel, which put us even further behind in schedule.

With clear skies, we didn't observe your adsb anomaly.
 
rleffler said:
We didn't get in about 8:30 due to a late start. I suspect you were long gone by the time we got there. It took us 30 minutes to find the FBO staff to get fuel, which put us even further behind in schedule.

With clear skies, we didn't observe your adsb anomaly.
Click to expand...

30 minutes!! WTH. I will have to complain about that. I was running behind too, and got to the ramp just in time to see you take off.

I did observe the FIS-B anomoly again near Nashville. It wasn't as wide spread as last time, but it showed some green, yellow and even red echoes where the sky was perfectly clear. This was about 9:45 yesterday morning with all new G3X Touch software. Very weird.
 
Green and yellow returns when weather clear

Years ago, when I was flying a lot of international flying, we ran into things like this all the time.

We flew into places like Malaysia and Indonisia, where the humidity was like 99.9 % on perfectly clear days. This was due to the high humidity, so we just turned the gain down to where the returns disappeared.

So yes, radar can give false returns due to high humidity. With the radar returns displaying high humidity, it is all possiabe that is what is showing on ADSB.

Only time will tell, but is it better to display weather that is not there, than not displaying weather that is.

Remember this, the weather you see now on ADSB is 5 to 20 min old, so please don't rely of it to help you fly through it.

Fly safe.
 
Pdtofly said:
Years ago, when I was flying a lot of international flying, we ran into things like this all the time.

We flew into places like Malaysia and Indonisia, where the humidity was like 99.9 % on perfectly clear days. This was due to the high humidity, so we just turned the gain down to where the returns disappeared.

So yes, radar can give false returns due to high humidity. With the radar returns displaying high humidity, it is all possiabe that is what is showing on ADSB.

Only time will tell, but is it better to display weather that is not there, than not displaying weather that is.

Remember this, the weather you see now on ADSB is 5 to 20 min old, so please don't rely of it to help you fly through it.

Fly safe.
Click to expand...

Do you mean "radar" radar? Or Nexrad ADS B. You said you turned down the "gain", so I assume you mean "radar" radar.
 
donaziza said:
Do you mean "radar" radar?
Click to expand...

Ground based radar installations are used to feed info to the ADS-B system. If the radar is picking up the false echoes due to the humidity (or smog, etc), it will show up on the ADS-B system.
 
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