Airborne Wx Radar Red+Magenta
 

hello,

I don't know the exact difference between a red and a magenta radar echo.

I know red means "strong returns" and magenta stands for"turbulence", but what is the exact difference?
If there are red patches on the screen that should also indicate a hazardous area in respect of turbulence,right?
So, maybe anybody can help me with this little problem.

cheerio sub

It's to do with strength of returned signals. The ascending order is green, yellow, red. The red shows up strongest returns from water droplets, which may be associated with turbulence, but don't look on the weather radar as a 'turbulence meter'. You have to interpret the signal and use your judgement.

The answer to your question depends on the specific weather radar product. Some weather radars have a 4-color precipitation mode, where magenta will show the heaviest rainfall (for example, one manufacturer's 4-color radars show magenta returns for "areas of very heavy rainfall rates of two inches per hour or greater.")

However, you're asking about weather radar that has a turbulence mode, and uses magenta to show areas of suspected turbulence, right?

The difference is that many radars (see first sentence in para 1) use wind data to provide the magenta turbulence display, in addition to their water reflectivity-based radar which provides the green, yellow, and red displays.

Significant changes in wind velocity are a very good indicator of potentially severe turbulence, so that's what the radar is looking for in turbulence mode. Often these magenta displays are found in the midst of the red returns -- no surprise there. The red is telling you about the heavy rainfall, and the magenta display is telling you about which specific areas have the worst turbulence potential, based on the winds.

When is this useful? You are correct when you state that red returns are probably a good indicator of turbulence anyway, and yes, you should most times avoid the red.

But, there are times, though, when flying in tropical areas, at fairly low altitudes (such as on departure or arrival) when you're only flying in steady rain (no turbulence at all) but you'll still get red returns due to the size of the water droplets and the amount of rain falling. In this case, the turbulence mode magenta returns can be helpful because they can help you differentiate between the red returns you really need to avoid, from the red returns simply caused by large rain droplets.

To expand on what McD has written..

From the Honeywell RDR-4B handbook, which I think is pretty well fitted to all major types of commercial jets..but which might not be yours!!

Black returns...rainfall rate less than 0.7mm/hr
Green returns.......''............0.7 to 4 mm /hr
Yellow returns......''.............4 to 12 mm /hr
Red returns..........".............Greater than 12mm/hr
Magenta returns.....''...........Not applicable to a rainfall rate.

Quoting from the introduction...
The RDR-4B radar system's turbulence detection capability incorporates a sophisticated Doppler Turbulence Detection circuit that measures the variations in horizontal speed of precipitive particles. If particle horizontal speed variations (indicative of wind shift) exceed the threshold of moderate to heavy turbulence a corresponding display (magenta colour) is provided.
:ok:

The answers by McD and idg have been very direct and to the point . I would just like to expand...although deviating from the direct answer.

Very heavy rain can give echoes even at 180 nm range. Such returns could give severe turbulence at 18000-30000 ft. However in monsoon conditions you may get " red " returns without any turbulence at lower altitudes. The storm cells can also be further examined by using tilt and gain to get a three dimensional view. However that is not required if you have the magenta with doppler sensor for turbulence detection. This actually detects the gradient and stronger the gradient more severe the turbulence !!
I hope that was useful.. Regds and HAPPY LANDINGS!!!!!:D :p

for turbulance detecting radars (for ex on 737) magenta has nothing to do with quantity of water in clouds.It just indicate a diference of water particles velocity of more than 5 m/s horizontaly. I've once seen only green returns on radar,and when we switched on WX/TB (ATIS says windshear reported) all green become magenta,and indeed it was turbulance:}
Red signify the most amount of water in clouds,heavy rainfall.Sometimes,there is no turbulance associated with red,you just deeply wash your plane.
You should always use tilt combined with diferent ranges to asses the potential danger in a cloud.You can enter in red (although it should be avoided due to heavy water ingested,hail and usual turbulance) but avoid by all means the magenta cell.It will give you ,at least,a big scare and maybe some injured passangers.And scare most of them of flying for months,at least.
Brgds Alex