pro write_dz_twaters, fname, hgt_bins, log_total_water_bins, dz_twater_total

; check to see if the file exists

OPENR, 1, fname, ERROR = err

if err eq 0 then begin
close, 1

; file exists, read the data
cdfid=ncdf_open(fname,/write)

print, 'writing to ',fname

dz_twater_total_id=ncdf_varid(cdfid, 'dz_twater_total')

ncdf_varput, cdfid, dz_twater_total_id, dz_twater_total

endif else begin	;OPENR, 1, fname, ERROR = err

; file does not exist, create it
cdfid=ncdf_create(fname,/clobber)
print, 'created ',fname
base_bins_did=ncdf_dimdef(cdfid,'base_bins',n_elements(hgt_bins))
top_bins_did=ncdf_dimdef(cdfid,'top_bins',n_elements(hgt_bins))
log_total_water_bins_did=ncdf_dimdef(cdfid,'log_total_water_bins',n_elements(log_total_water_bins))

hgt_bins_id=ncdf_vardef(cdfid,'hgt_bins',$
	[base_bins_did],/float)
log_total_water_bins_id=ncdf_vardef(cdfid,'log_total_water_bins',$
	[log_total_water_bins_did],/float)
dz_twater_total_id=ncdf_vardef(cdfid,'dz_twater_total',$
	[base_bins_did,top_bins_did,log_total_water_bins_did],/long)


ncdf_control, cdfid, /endef
ncdf_varput, cdfid, hgt_bins_id, hgt_bins
ncdf_varput, cdfid, log_total_water_bins_id, log_total_water_bins

ncdf_varput, cdfid, dz_twater_total_id, dz_twater_total

endelse		;OPENR, 1, fname, ERROR = err


NCDF_CLOSE, cdfid

return
end