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Global Change Master Directory (GCMD)
Soil Moisture - Percent Soil Moisture for 10 Day Period
Entry ID: USDA_FAS_Percent_Soil_Moisture


Summary
Abstract: Percent soil moisture is the available water for the plant divided by the total
water holding capacity of the soil profile. The available water is calculated
by the two-layer soil moisture model which accounts for the daily amount of
water withdrawn by evapotranspiration and replenished by precipitation. The
total water holding capacity for each grid cell was derived from the FAO
Digital Soil Map of the World and it is dependent on soil texture and depth of
the soil profile. For grid cells with soil depths greater than 1-meter, a
maximum soil depth of 1-meter was assumed to approximate the maximum root depth
for most plants. Inputs to the soil moisture model are acquired on a daily
basis by USDA-FAS from the U.S. Air Force Weather Agency . Data is aggregated
on a regular 10-day (dekadal) cycle at a resolution of approximately 40km using
the 1/8 mesh-grid reference system. Each grid cell contains a value for the
most recent dekadal period. The date attribute indicates the end date of the
dekadal period. Historical data archived by growing season can be viewed at
USDA'S Crop Explorer web site: "http://www.pecad.fas.usda.gov/cropexplorer".

Global percent soil moisture values are used as crop condition indicators in
analysis of commodity production and yield estimates.The final aim of the soil
moisture model is to estimate if soil moisture storage between dry spells was
adequate for maximum plant growth.

The soil moisture within two soil layers is calculated in daily time increments
(mm/day of precipitation or evapotranspiration). The top-layer soil moisture is
assumed to hold a maximum of one inch (or 25-mm) of available water, and the
sub-layer soil moisture may hold 0-400 mm/m of water depending on the soil????s
water-holding capacity (based on soil texture and soil depth) for the grid
cell. The soil moisture model assumes precipitation enters the two soil layers
by first filling the surface soil layer and then filling the lower soil layer.
Moisture is extracted from the two soil layers by evapotranspiration, whereby
water is first depleted from the top layer and then extracted from the
sub-surface layer. When the water-holding capacity of both soil layers is
reached, excess precipitation is lost from the model and treated as runoff or
deep percolation. Daily evapotranspiration for the two-layer soil moisture
model is calculated by the FAO 56 Penman-Monteith equation and daily
precipitation is estimated from both surface observations and satellite data.
The water-holding capacities for both layers were derived from the FAO Digital
Soil Map of the World. The U.S. Air Force Weather Agency (AFWA) began to
develop the Agricultural Meteorology Model (AGRMET) in 1981 (Cochrane, 1981).
The AGRMET algorithms have evolved over several decades of work and they are
constantly changing. The AGRMET model basically converts satellite data into
spatial agrometeorological information and utilizes WMO ground station data in
the algorithms whenever possible. These spatial agrometeorological data sets
are then stored in a geodatabase as 1/8-mesh grid cells. The coordinate system
for the 1/8-mesh grid cells is a 512 by 512 grid laid on a polar stereographic
projection for the northern and southern hemispheres (refer to Figure 2). The
projection is true at 60-degree latitude, with the grid cell resolution ranging
from 51-km at the poles to 25-km near the equator. More information on the
1/8-mesh grid reference system can be found in Hoke, et al., (1981). The
current global precipitation is estimated by blending four different data
sources together. The SSM/I (Special Sensor Microwave /Imager) is the first
source. Rain rates are formulated from the brightness temperatures as
documented by Hollinger (1989). The second source uses the Real Time
Nephanalysis Cloud Model (RTNEPH) described by Kiess and Cox (1988). The third
sources uses World Meteorological Organzation (WMO) ground station data.
Geostationary satellites such as GOES, Meteosat, and GMS comprise the fourth
source used to estimate global precipitation on a regular 10-day (dekadal)
cycle.

Related URL
Link: View Related Information
Description: USDA Foreign Agricultural Service Metadata Explorer.


Link: View Related Information
Description: Map Service: USDA_FAS_Percent_Soil_Moisture

Geographic Coverage
 N: 90.0 S: -90.0  E: 180.0  W: -180.0

Data Set Citation
Dataset Creator: USDA, Foreign Agricultural Service Crop Explorer Web Service
Dataset Title: Soil Moisture - Percent Soil Moisture for 10 Day Period
Dataset Series Name: Crop Explorer
Dataset Release Date: 2004-01-01T00:00:00.000Z
Dataset Release Place: Washington, DC
Dataset Publisher: USDA, Foreign Agricultural Service
Version: Not provided
Data Presentation Form: GIS


Temporal Coverage
Start Date: 1970-01-01


Location Keywords
GEOGRAPHIC REGION > GLOBAL LAND


Science Keywords
AGRICULTURE >SOILS >SOIL CLASSIFICATION    [Definition]
AGRICULTURE >SOILS >SOIL DEPTH    [Definition]
AGRICULTURE >SOILS >SOIL MOISTURE/WATER CONTENT    [Definition]
AGRICULTURE >SOILS >SOIL TEXTURE    [Definition]
AGRICULTURE >SOILS >SOIL WATER HOLDING CAPACITY    [Definition]
LAND SURFACE >SOILS >SOIL CLASSIFICATION    [Definition]
LAND SURFACE >SOILS >SOIL DEPTH    [Definition]
LAND SURFACE >SOILS >SOIL MOISTURE/WATER CONTENT    [Definition]
LAND SURFACE >SOILS >SOIL TEXTURE    [Definition]
LAND SURFACE >SOILS >SOIL WATER HOLDING CAPACITY    [Definition]
AGRICULTURE >SOILS >SOIL ROOTING DEPTH    [Definition]
LAND SURFACE >SOILS >SOIL ROOTING DEPTH    [Definition]


Platform
FIELD SURVEYS    [Information]


Access Constraints
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Keywords
ArcIMS Metadata Server
Soil Moisture
Crop Assessment
Remote Sensing


Data Set Progress
ACTIVE


Data Center
Production Estimates and Crop Assessment Division, Foreign Agricultural Service, U.S. Department of Agriculture    [Information]
Data Center URL: http://www.pecad.fas.usda.gov/

Data Center Personnel
Name: USDA PRODUCTION ESTIMATES AND CROP ASSESSMENT DIVISION
Phone: (202) 720-0888
Fax: (202) 720-8880
Email: pecad at fas.usda.gov
Contact Address:
U.S. Department of Agriculture
Room 6053, South Building Stop 1045
City: Washington D.C.
Postal Code: 20250
Country: USA



Distribution
Distribution_Media: Online


Personnel
BOB BALDWIN
Role: METADATA AUTHOR
Role: TECHNICAL CONTACT
Phone: 1-202-720-1860
Fax: 1-202-720-1295
Email: bob.baldwin at usda.gov
Contact Address:
USDA
Foreign Agricultural Service
CMP-PECAD, MS 1045-S
1400 Independence Avenue, SW
City: Washington
Province or State: DC
Postal Code: 20250
Country: USA


Extended Metadata Properties
(Click to view more)

Creation and Review Dates
DIF Creation Date: 2005-02-16
Last DIF Revision Date: 2018-11-08



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