速度势叠加辐散风时风场有一条条线连起来，想请教一下各位怎么解决

xylxylll

画速度势叠加辐散风时图a和c都是正常的，就图b的风场有线条连起来，这是为什么啊？我a和b的设置都是一样的，就图b出问题了，想请教一下各位这是图b的gs，图a和图b是一样的
'set parea 6.0 10.0 5.0 8.0'
'set lev 200'
'set lat -90 90'
'set lon 0 360'
'chi2=fish_chi(du2,dv2)'
'chi2=chi2-aave(chi2,global)'
'set lat -60 60'
'set lon 0 180'
'set map 1 1 5'
'draw map'
'set xlopts 1 4 0.15'
'set ylopts 1 4 0.15'
'set xlint 20'
'set ylint 20'
'one=1+0*lat'
'uchi2=-muadv(one,chi2)'
'vchi2=-mvadv(one,chi2)'
'define ttest2=dv2/(sqrt(ddv2)*sqrt(1/16))'
'set gxout shaded'
'set clevs -0.69 0.69'
'set ccols 15 0 15'
'd ttest2'
'set gxout contour'
'set clevs -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8'
'set ccols 24 25 26 27 28 32 33 34 35 36'
'set strmden 1'
'set cthick 10'
'd chi2/1.e6'
'set gxout vector'
'set cthick 5'
'set ccolor 1'
'set arrscl 0.5 2'
'set arrlab on'
'd skip(uchi2,3);skip(vchi2,3)'