Weather Radar interpretation
Join Date: Jun 2002
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Fundamentally, the reason the Wx radar is fitted is so we can avoid turbulence associated with Cbs. So, the first thing you should determine (from the met briefing pack) is the likelihood of their presence. Also, you have don't have to have rain to get a ride that will make your eyeballs hit their limit switches.
So, moving on it's not the colour per se that determines the movement of the air around the water that is displayed on the display. I'll give you that white/magenta or what ever colour is designated to the highest return, is probably due to rainfall from Cb, which are probably best avoided, but not always. What you need to avoid are the areas containing sudden and abrupt transitions in the patterns displayed. Avoiding an area purely due to colour alone may only add to track miles and give no smoother ride. Hooks, swirls, solid lines and areas with high contrast are also best given a wide berth. And here's the weird one, not all Cb's give a rough ride. But I'll be buggered if I can tell which ones are the friendly ones in advance.
PM
So, moving on it's not the colour per se that determines the movement of the air around the water that is displayed on the display. I'll give you that white/magenta or what ever colour is designated to the highest return, is probably due to rainfall from Cb, which are probably best avoided, but not always. What you need to avoid are the areas containing sudden and abrupt transitions in the patterns displayed. Avoiding an area purely due to colour alone may only add to track miles and give no smoother ride. Hooks, swirls, solid lines and areas with high contrast are also best given a wide berth. And here's the weird one, not all Cb's give a rough ride. But I'll be buggered if I can tell which ones are the friendly ones in advance.
PM
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From the Airbus document on weather radar use:
I'm not following. Shouldn't that need excessive negative tilt and would set the radar to scan what the aircraft is leaving below instead of scanning what one is going to fly through up above? Or is it because the radar will give a better indication of what is above by showing what is below (the lower the moister)?
Escape Path
Climb: Select negative tilt, maintain ground returns on top of ND as the aircraft climbs
Escape Path
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by tilting down, you insure that the radar will paint a bit of the ground at the farthest range. in this way you know you are getting something. what if you had tilted so high that you got nothing...and smacked into a cell/
next time you fly on a nice day, ask the captain if you may experiment with the wx radar...tilt it, paint the ground, try different gain settings on distant , visually observed cells,
and please, look at the boundries between colors...it is the boundries which are often the most turbulent.
next time you fly on a nice day, ask the captain if you may experiment with the wx radar...tilt it, paint the ground, try different gain settings on distant , visually observed cells,
and please, look at the boundries between colors...it is the boundries which are often the most turbulent.
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Escape Path: By setting your radar so that ground returns are shown on the top of the ND (ie. at extreme range) means that anything showing before that return will be a valid "sky" return. It's one method of optimising the tilt, valid for each range setting.
PM
PM
I'll probably get shot down, but I reckon most of the Archie stuff is a WOFTAM. I do exactly as Scarebus does; put the ND on a reasonable scale eg cruise 160nm and put the inner edge of the groundline on the 80nm ring, full gain. Any return that comes inside 80nm is not ground, could be nasty and is dealt with. On climb and descent, at lower ranges, ground return on on the top edge of ND, for the reason Piltdown Man said. No need for mind-numbing tilt calculations.
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all of this is fine, painting the ground at the edge is the right thing to do with the tilt.
Once you see a return/cell you can tilt up to see how high the cell might be.
now, using the gain. instead of the real reason to use the gain, think of it as an old time ''fine tuner'' on an ancient analog tv set. twist the gain slowly back and forth till the ''best'' image results. Especially with the most contrast (different color levels) between portions of the cell.
I am still convinced that the difference in colors at the boundries is the roughest spot. Why? The difference between the two boundries can almost be thought of as change in velocity of hydrometeors (raindrops). Its the difference that makes the bumps...some of the time.
oh well, back to sleep
me, I'm in the DCA tower on night duty...HA!
Once you see a return/cell you can tilt up to see how high the cell might be.
now, using the gain. instead of the real reason to use the gain, think of it as an old time ''fine tuner'' on an ancient analog tv set. twist the gain slowly back and forth till the ''best'' image results. Especially with the most contrast (different color levels) between portions of the cell.
I am still convinced that the difference in colors at the boundries is the roughest spot. Why? The difference between the two boundries can almost be thought of as change in velocity of hydrometeors (raindrops). Its the difference that makes the bumps...some of the time.
oh well, back to sleep
me, I'm in the DCA tower on night duty...HA!
Psychophysiological entity
Then there are the times that you may as well turn it off:
Briefly...North of Mont Blanc, in the stars way above some stratus. 5k' at least. Quite a light show showing trough the clouds. One core painting ahead.
Altered course to pass more than 10NM from the core. Suddenly, we fell down a series of concrete steps - each one having a thousand foot tread. My jacket floated on its hangar each drop.
There was no significant upper wind or orographic effect, just the storm a mile below.
Briefly...North of Mont Blanc, in the stars way above some stratus. 5k' at least. Quite a light show showing trough the clouds. One core painting ahead.
Altered course to pass more than 10NM from the core. Suddenly, we fell down a series of concrete steps - each one having a thousand foot tread. My jacket floated on its hangar each drop.
There was no significant upper wind or orographic effect, just the storm a mile below.
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Back to the OP's question - can it be said that stratiform rain clouds - oops, I mean nimbostratus - are not as likely to have the strong gradients and irregular contours?
[funny/] I had a Captain last summer ask me to request a heading to go around one of the two cells that was in front of us. At our 11 o'clock and 1 o'clock. That were moving with us. In a clear sky.
"Uh, Captain, I think those are cat eyes from the radome. . . "
[funny/] I had a Captain last summer ask me to request a heading to go around one of the two cells that was in front of us. At our 11 o'clock and 1 o'clock. That were moving with us. In a clear sky.
"Uh, Captain, I think those are cat eyes from the radome. . . "
