NCL参考线绘制

何源

请问，有朋友遇见过，NCL折线图中，在画参考线之后，出现参考线遮蔽部分线段的问题嘛？是如何解决的呢？谢谢作图代码如下：
;---------------------Draw the plot----------------
res=True
res@gsnDraw=False
res@gsnFrame=False
res@vpHeightF=0.3
res@vpWidthF=0.7
res@trXMaxF=2011
res@trXMinF=1965
res@tiXAxisString="Year"
res@tiYAxisFontHeightF=0.018
res@tiXAxisFontHeightF=0.018
res@gsnYRefLine=0
res@gsnYRefLineThicknessF=1.5
res@tmYROn=False
res@tmXTOn=False
res@tmXBMode="Manual"
res@tmXBLabels=year
res@xyLineColor="red"
res@xyLineThicknessF=2.0
res@xyMarkLineMode="MarkLines"
res@xyMarker=1
res@xyMarkerSizeF=0.025
res@gsnYRefLine=0
res@gsnYRefLineThicknesse=1.5
res@xyMarkerColor="black"

wks=gsn_open_wks("eps", get_script_prefix_name())
plot=new(2,graphic)

do i=0,1
    if(i.eq.0)then
        data=ipr
        res1=res
        res1@tiYAxisString="Precipitation anomaly/mm"
        res1@xyLineColor="blue"
        res1@xyMarkerColor="blue"
        plot(i)=gsn_csm_xy(wks,year,data,res1)
    end if
    if(i.eq.1)then
        data=itm
        res2=res
        res2@xyMarkerColor="red"
        res2@tiYAxisString="Temperature anomaly/~S~o~N~C"  
         plot(i)=gsn_csm_xy(wks,year,data,res2)
    end if
    delete(data)
end do

resP                    = True                 ; modify the panel plot
  resP@gsnFrame           = False                ; don't advance panel plot
  resP@gsnPanelLabelBar   = False                 ; add common colorbar
  resP@gsnPanelBottom     = 0.05
  resP@lbOrientation="Vertical"  
  resP@pmLabelBarWidthF=0.04  
  resP@pmLabelBarHeightF=0.6
  resP@gsnPanelFigureStrings=(/"(a)","(b)"/)
  resP@gsnPanelFigureStringsFontHeightF=0.01
  resP@gsnPanelFigureStringsPerimOn=False
  resP@amJust="TopLeft"
  gsn_panel(wks,plot,(/2,1/),resP)               ; now draw as one plot
  frame(wks)