ncl 我的程序是这样，出图后单位是mm/year，我需要的结果是mm/month，怎么处理

LAVINE

begin
a=addfile ("/mnt/f/paper/num/CESM2_evspsbl_historical_r1i1p1f1_1980_2014.nc", "r")
t=a->evspsbl(0:419,:,:)
a_t=clmMonTLL(t)
a_t!1="lat"
a_t!2="lon"
a_t&lat=fspan(-90,90,192)
a_t&lon=fspan(-180,178.75,288)
a_t&lat@units="degree_north"
a_t&lon@units="degree_east"
MAM_t=new((/3,192,288/),float)
JJA_t=new((/3,192,288/),float)
SON_t=new((/3,192,288/),float)
DJF_t=new((/3,192,288/),float)
do i=0,2
MAM_t(i,:,:)=a_t(i+2,:,:)
JJA_t(i,:,:)=a_t(i+5,:,:)
SON_t(i,:,:)=a_t(i+8,:,:)
end do
DJF_t(0,:,:)=a_t(11,:,:)
DJF_t(1,:,:)=a_t(0,:,:)
DJF_t(2,:,:)=a_t(1,:,:)
MAM_a_t=new((/192,288/),float)
JJA_a_t=new((/192,288/),float)
SON_a_t=new((/192,288/),float)
DJF_a_t=new((/192,288/),float)
MAM_a_t=dim_avg_n(MAM_t,0)
JJA_a_t=dim_avg_n(JJA_t,0)
SON_a_t=dim_avg_n(SON_t,0)
DJF_a_t=dim_avg_n(DJF_t,0)
MAM_a_t!0="lat"
MAM_a_t!1="lon"
MAM_a_t&lat=fspan(-90,90,192)
MAM_a_t&lon=fspan(-180,178.75,288)
MAM_a_t&lat@units="degree_north"
MAM_a_t&lon@units="degree_east"
copy_VarCoords(MAM_a_t,JJA_a_t)
copy_VarCoords(MAM_a_t,SON_a_t)
copy_VarCoords(MAM_a_t,DJF_a_t)


wks1=gsn_open_wks("png","/mnt/f/paper/pic/CESM2_evspsbl1")


ypts =(/9,14,14,9,9/)      ;研究区域
xpts =(/-8,-8,36,36,-8/)
resp= True
resp@gsLineThicknessF=6.0
resp@gsLineColor="black"
resp@gsLineLabelString=""