Challenge	Met. no	KNMI	EMHI	FMI	Swe rad	DWD	
Vertical reflectivity profile	***	***	***	***	***	***+	
Attenuation by precip. 	** 1	***	***	**	**	***+	
Total beam overshooting 	***	**	**	***	**	**	
Sea clutter	***2	***	**	**	***	**	
Ground clutter	**-***	*	**	*	**	***+	
AP clutter	***	**	**	*	***	***	
Hail	**	**	**	*	**	**	
Propagation changes	**	*	**	*	**	*	
Beam blockage	***	***	***+	*	***	***+	
Gauge adjustment	**	***	***	*	***	**	
Radar siting	***	*	***+	o	***	***	
Suboptimal compositing algorithms	***	*	?	**	**	***	
Availability of polar data	*	**	* ?	o	***	* 12	
Orographic enhancement and lee effects	**	o	?	*?	*	*	
Hardware	*-*** 3	*	** 6	*	**	* 13	
Absence of metadata	*	*	*	**	*	**	
Meteorological algorithms	?	***	**?	***	***	* 14	
Data assimilation to models	?	***	***+	*	***	** 15	
Birds	*	*	*	**	**	*	
Overhanging precipitation	***	***	**	**	***	**	
Interfering emitters, jamming	*	*	*?	*	**	** 15	
Wet radome attenuation	**	**	*? 7	**	**	**	
Attenuation by icy, sleety, salty or dirty radome	**	*	*? 7	*	**	**	
Infrastructure: electricity, tower structure	* 4	o	* or 
***+ 8	* 4	***	*	
Water phase	**	*	**	**	**	*** 16	
Miscalibration	*	**	?	**	*	*	
Pointing error (elevation)	* 5	**	?	**	*	17	
Z (R, S)	?	***	?	**	**	**	
Ships	?	*	*?	*	*	**	
Scan strategy	***	**	***+	*	**	***	
Second trips (Cb + AP)	*	*	**?	*	**	**	
Sidelobes	*	*	*	*	*	* 18	
Chaff	o	*	?	*	**	* 	
Windmills	o	**	o 9	o	*	* 19	
Dry radome attn	*	*	*? 7	o	*	**	
Attn. by gases	o	*	* 7	*	*	*	
Attn. by clouds	o	*	* 7	*	*	*	
Insects	?	*	*	*	*	*	
Sun	*	*	* 10	*	*	*	
Specular reflections (Neighbours)	*	**	o	o	*	o?	
Forest fires, volcanic ash	o	o	o 11	o	*	o	
Bragg scattering from clear air	o	*	*?	o	*	o?	
Clouds	o	*	**?	?	*	?	
Aircraft in noise samples	o	*	*	o	*	*	
Flare echo	o	o	*	o	*	o	

Stars on scale * to ***, numbers refer to footnotes below. ”O” stands for question not applicable, phenomena not seen as a problem etc. "+" is short for "even more".
Footnotes

Met.no Comments:
1)Attenuation by precip. severe in sleet
2)Sea clutter is more problematic than ground clutter for the Doppler radars
3)Hardware problems occur seldom, but serious since some radars are at remote locations
4)Infrasturcture: tower structure no problem
5)Pointing error (elevation): serious when it happens, but elevation is stable and controlled twice a year
EMHI comments
6)this was a problem first half of 2000
7)no own research
8)infrastructure OK but no tower !
9)growing
10)We see it very well, but we don't think that it's a problem
11) Seen once, but we don't think that it's a problem
DWD comments
12) stars given for user needs, more important in research
13) *** if designed
14) for users anything is better than nothing, for research this is ***
15) for models *** or more
16) nowcasting + hydromet ***, model * presently
17) mostly * to **, *** for blocking correction
18) *, ** to *** for pol
19) for model **+