Embraer EMB145 Operation Manual page 2550

NAVIGATION AND
COMMUNICATION
WEATHER RADAR NORMAL OPERATION
The weather radar is controlled through the weather radar control
panel and via the MFD Bezel Buttons. The weather radar control panel
provides control functions and operating modes management for
proper weather radar operation. The weather radar control panel may
be located on the control pedestal forward panel or on the glareshield
panel. Some airplanes may optionally be equipped with two weather
radar control panels.
INTERPRETING WEATHER RADAR IMAGES
The weather radar is a water detector. It is calibrated to best see water
in its liquid form and with an ideal raindrop diameter. The weather
radar can see rain, wet snow, wet hail and dry hail (depending on its
diameter). The radar can not see water vapor, ice crystals and small
dry hail.
At higher altitudes, there is less humidity in the air and consequently
there is less water condensation. It means that heavy precipitation and
dense cells are less likely to occur. As a result, flight level 200 (FL200)
is defined as "FREEZING LEVEL", i.e., presence of water in its liquid
form is not forecast above this level. However, CBs and other
phenomena may push humidity and water, sometimes supercooled
water, to higher altitudes due to convective activity.
WARNING: DRY HAIL CAN BE PREVALENT
ALTITUDES.
RETURN IS POOR, IT MAY NOT BE DETECTED.
Use increased gain when flying near storm tops in order to display the
normally weaker returns that could be associated with hail.
Page
4
2-18-45
AIRPLANE
OPERATIONS
MANUAL
SINCE
Code
01
ITS RADAR
AT HIGHER
REFLECTIVE
REVISION 38