esp. for FV3-LAM model based DA, eg. RRFS-DA, RRFS-3DRTMA.
(Also see the issue in EMC GSI github repository: #601
 Adding I/O for Analysis of Significant Wave Height for 3DRTMA)

(howv) in 3D analysis, based on feedbacks from code reviewers.

for significant wave height:
  1) combine two variables i_howv_in_anav and i_howv_in_data into one
variable i_howv_3dda
  2) if howv is required in analyis (as set howv in anavinfo), but if howv
is not available in firstguess, then stop GSI run.
  3) removing the code which tunes the static BE of howv in hybrid envar
run. So in hybrid run, user needs to set the corp_howv in namelist if
desired.
  4) cleaning some unnecessary comments

firstguess.

code review.

analysis of siginificant wave height.