. Areas of lower salinity (river runoff, ice edge) will reduce the conductivity of the water and overall effectiveness  of  MIW  operations.  Conductivity  is directly  proportional  to  salinity  and  temperature. . In coastal environments with a large input of fresh  water  from  river  runoff,  a  strong  positive  sound velocity  gradient  can  form  causing  upward  refraction  of the sonar beam. Meteorology There are several METOC considerations that must be  addressed  in  the  planning  and  conducting  of  MIW operations. l Surface winds — If they are too strong, can we have an effective operation? l Wave action —  Affects  underwater  visibility, burial and movement of mines, accuracy of navigation, sound velocity profiles, deployment of MNVs, sweep gear, and divers. .  Prevailing  visibility  —  If   obstructions   to visibility are present, navigation, minehunting and sweep  effectiveness  is  decreased. . Hours of daylight —  Airborne  minehunting, minesweeping,  and  EOD  diver  operations  are  primarily conducted  during  daylight  hours. Now let’s discuss the environmental amphibious  warfare  (AMW)  operations. support  for BRIEFING OF METOC SUPPORT FOR AMW OPERATIONS LEARNING    OBJECTIVES: Brief   the Commander,  Amphibious  Task  Force  (CATF), and  all  interested  personnel  on  expected METOC   conditions   during   the   planning, embarkation,  rehearsal,  movement,  and  assault phases  of  AMW  operations. In this discussion of AMW operations we will be discussing environmental support during the Planning phase,  followed  by  the  Embarkation  phase,  Rehearsal phase, Movement phase, and lastly the Assault phase (PERMA). THE PLANNING PHASE The  Aerographer  must  first  become  familiar  with the  initial  operation  plans  (OPPLANs)  and  operation orders   (OPORDs),   and   must   attend   pre-mission briefings  and  conferences  so  that  environmental  factors affecting the various aspects of the mission can be addressed.  In  addition,  the  Aerographer  must  be prepared  to  provide  the  following: . Long-range climatological and historical data. During the planning phase this can prove critical to mission success. Determine conditions that will most likely  influence  the  location  and  time  of  landing including: — — — Weather. Emphasis should be given to cloud ceiling height, visibility, and winds. This also  includes  local  effects. Sea, swell, and surf conditions. Sea  surface  temperatures. .  Astronomical  data  (sunrise/sunset,  moonrise/ moonset,  and  percent  of  illumination),  tidal  data  that affects local anchorages, as well as surf conditions to include: — — — Character of surf zone. Degree of exposure of potential obstacles in the surf zone. Beach  slope/s. — Wave oscillation in harbor/s. .  Hydrographic  data  for  inshore  navigation  of landing  craft. —  Treacherous  regions  of  bays,  harbors,  etc. —  Sandbars. —  Reefs. THE  EMBARKATION  PHASE During  this  phase,  equipment  and  troops  are embarked   in   assigned   ships. Load   out   is accomplished. .  Amphibious  operations  are  keyed  to  sequential events. .  Environmental  support  may  include  both mid-range  and  short-range  forecasts. l  The  OA  division  aboard  the  LHA/LHD/LPH becomes the focal point of the operation. 13-7