# Presentation: 201926

## Creation of Gridded MOS Land Water Mask

- Statistical Modeling Branch
- Meteorological Development Lab
- November 9, 2007

## Current GMOS Land Water Mask

- Coarse U.S. shapefile  from ESRI media DVD
- Manual editing tailored to analysis technique
- coastline was adjusted to match station location
- Grid point location not considered in edits

## Purpose of Regenerating Land Water Mask 

- Common land water mask for GMOS and verification software
- Poor Gridded MOS verifications in coastal areas when compared to NDFD
- GMOS users expressed concern along the east coast
- Barrier islands
- Harbor and Bay sizes not accurate

## Current GMOS Land Water Mask

## AWIPS High Resolution Shapefiles

- Marine Zones only consider US territory
- Mexico & Cuba not available
- Includes all US lakes
- Gaps between US and Canada where water exists

## AWIPS High Resolution Shapefiles

## Modified AWIPS High Resolution Shapefiles for GMOS

- AWIPS States Shapefile
- Removed Lake Okeechobee due to lack of MOS station guidance in the lake
- No Mexico AWIPS shapefile
- Used ESRI Media States file
- Drew polygon to “fill in” holes left due to differing resolution with AWIPS states shapefile
- Inland Water
- AWIPS Lakes Shapefile
- Selected Great Lakes, Great Salt Lake, & Lake St. Claire
- AWIPS Canadian Province Shapefile
- More coarse than AWIPS states shapefile
- Drew polygon to “fill in” holes left due to differing resolutions
- Ocean
- No Ocean Shapefiles existed
- Used a rectangular polygon bigger than the coverage area and erased all of the aforementioned shapefiles, so the remaining area became ocean

## Removing Lake Okeechobee

- Take care to delete entire sketch, so no residual evidence of the lake is left.

## Shapefile Edits for Land Water Mask

- Polygons were dissolved to eliminate holes and boundaries
- Inland water, Ocean, and Land shapefiles were merged to form a single shapefile
- Attribute field indicates land or water
- Ocean = 0
- Inland Water = 3
- Land = 9

## Land Water Mask Shapefile

## Land Water Mask Shapefile

- Polygon Shapefile converted to Raster GRID
**Raster cell given value of polygon directly under the CENTER of the grid cell**
- Check was made by assigning polygon value to NDFD points
- Grid values were extracted to points

## New Land Water Mask

## New Land Water MaskAreas of Forecaster Concern

- KMLB

- KBOX

- KOKX

- KILM

- KGYY

## Difference in Current GMOS and New Land Water - KGYY

## Temperature F24 November 4, 2007 12Z Cycle Proposed Land Water Mask

- maps are available on web site as *.pdf files with zoom capability

## Temperature F24 November 4, 2007 12Z Cycle Operational Land Water Mask

- Temperature F24 November 4, 2007 12Z Cycle Operational Land Water Mask

- maps are available on web site as *.pdf files with zoom capability

## Resources and Contact Information

- _[Web Based Land Water Mask Comparison](http://www.weather.gov/mdl/synop/gmos/landwater.html)_
- _[AWIPS Map Database ](http://www.weather.gov/geodata)_– shapefile source
- ESRI’s ArcInfo 9.2 was used to create the land water mask
- For Further information
- Kari Sheets, SMB GIS team lead
- 301-713-0023 ext 125
- _[Kari.sheets@noaa.gov](mailto:Kari.sheets@noaa.gov)_