ncl处理时间维度出错

anran

请问，做海温距平场，没有平均时间维数之前，数值大小都在正负0.2之间，为什么将时间维度平均之后就变成10的负9次方的数呢？
begin
year = ispan(1960, 2015, 1)
t_s =196012
t_e =201611
f    = addfile("sst.mnmean.nc","r")
time = f->time
YYYYMM  = cd_calendar(time, -1)
rec_s = ind(t_s.eq.YYYYMM)
rec_e = ind(t_e.eq.YYYYMM)
sst = f->sst(rec_s:rec_e,:,:)
sst_djf = month_to_season(sst,"JFM")
copy_VarMeta(sst(0,:,:), sst_djf(0,:,:))
sst_djf!0       = "year"
sst_djf&year = year
sst_djf = where(ismissing(sst_djf),0,sst_djf)
sst_ano = dim_rmvmean_n_Wrap(sst_djf, 0)
;sst_ano = where(ismissing(sst_ano),0,sst_ano)
x1 = dim_avg_n_Wrap(sst_ano, 2)
x1@_FillValue = -9.96921e+36
x =dim_avg_n_Wrap(x1,0)
x@_FillValue = -9.96921e+36
print(x)
exit

求大神解答！！