I need to have in the graphics the contour lines hidden behind the gray topography: 
I use following code:
Show[ContourPlot[
pa[y, x] - p[y] //. anstrom //. {h -> 1000, a -> 1500,
u -> 15}, {x, -50000, 50000}, {y, 0, 10000},
ContourShading -> None, ImageSize -> Large,
FrameLabel -> {{HoldForm[y[m]], None}, {HoldForm[x[m]], None}},
PlotPoints -> 50, Contours -> 10, ContourLabels -> True],
Plot[contour2 //. {a -> 1500, h -> 1000}, {x, -50000, 50000},
PlotRange -> {Full, {0, 10000}}, PlotStyle -> Black,
ImageSize -> Large, AxesOrigin -> {-50000, 0}, Filling -> {Axis},
FillingStyle -> {Opacity[1.0, Gray]}]]
where the normal Plot is just the lower gray topography.
I tried to change the order and vary options like opacity, nothing helps.
Thanks for every help.