Data Sources

Summary of Global Data Sources and Processing Models

Input Data Normal Baseline Data Additional Output Data Products

(Further description of products, acronyms and references are provided in the conference paper shown below.)

Agrometeorological Parameters Coverage Spatial Resolution Temporal Resolution Update Frequency Source Processing Agency

 Input Data

Precipitation (mm)
Min/Max Temperature (°C)
Global Station Daily Daily Stations WMO
Precipitation (mm)
Min/Max Temperature
Snow Depth (cm)
Shortwave & Longwave Radiation
Actual & Potential Evapotranspiration (mm)
Global 1/8-mesh grids Daily Daily
USAF 557th WW

 Normal Baseline Data

Precipitation (mm)
Avg. Temperature (°C)
Global Station Monthly Dekadal
& Daily
N.A. Stations WMO and NOAA
Precipitation (mm)
Temperature (°C)
Global 1/8-mesh grids Monthly Dekadal
& Daily
N.A. Stations extrapolated
to 1:5 M Scale
(~10-km pixels)
Soil Water-holding Capacity (mm)
Global 1/8-mesh grids N.A. N.A. FAO/UNDP Digital Soil
Map of the World
(1:5M Scale)
Digital Elevation Model (DEM) (meters)
Global 1/8-mesh grids N.A. N.A. 1:5 M Scale (or 5-minute resolution, ~10-km pixels) UNEP GRID

 Additional Output Data Products (Agrometeorological, Soil Moisture & Crop Models)

Avg Temperature
PET (from FAO-56 Penman Monteith equation)
Global Stations &
1/8-mesh grids
Daily Dekadal Stations &
1/8-mesh grids input data
Top- & sub-layer soil moisture (mm)
Percent soil moisture (%)
Global Stations &
1/8-mesh grids
Daily Dekadal Stations &
1/8-mesh grids input data
Crop Calendars
Global Stations &
1/8-mesh grids
Daily Dekadal Stations &
1/8-mesh grids input data
Crop Stress and Alarms
Global Stations &
1/8-mesh grids
Daily Dekadal Stations &
1/8-mesh grids input data
Automated Maps & Graphs
Global Stations &
1/8-mesh grids
Daily Dekadal Stations &
1/8-mesh grids input data

Input Data Sources, Climate Normals, Crop Models, and Data Extraction Routines Utilized by GMA/IPAD


United States Department of Agriculture (USDA), Foreign Agricultural Service (FAS),
Global Market Analysis (GMA)
Submitted to the Third International Conference on Geospatial Information in Agriculture and Forestry,
Denver, Colorado, November 5-7, 2001


The U.S. Department of Agriculture’s (USDA), Foreign Agricultural Service (FAS), Global Market Analysis (GMA), International Production Assessment Division (IPAD) displays near real-time agrometeorology and vegetation condition data to the public through Crop Explorer. Several different input databases, climate normals, crop models, and data extraction routines are utilized to produce these images on Crop Explorer. The data sources and models are briefly described with references to their original sources. The main data output products provided by Crop Explorer include spatial images for estimated precipitation and temperature; cumulative precipitation; percent normal of precipitation; temperature departures from normal; and top- and sub-layer soil moisture. Future outputs envisaged include: crop stage and crop stress for wheat and corn; relative yield reductions for corn, wheat, and soybeans; and NDVI anomalies for most major agricultural regions in the world. It is anticipated that most of these output products will be made available on the Internet in the near future.


GMA/IPAD relies on several different data sources to monitor weather anomalies that affect crop production and quality of agricultural commodities. The two main agrometeorological input data sources are:
  • Ground meteorological station measurements from the World Meteorological Organization (WMO), and
  • Gridded weather data that integrates the WMO ground station data with satellite imagery.

Both these data sets are entered and stored in GMA/IPAD’s CADRE (Crop Condition Data Retrieval and Evaluation) database management system (DBMS) on a daily basis. After the agrometeorological data is downloaded, several data extraction routines are executed to display the following spatial data for different regions in the world:

  • Actual and cumulative precipitation (in mm)
  • Average, minimum, and maximum temperatures (in ºC)
  • Precipitation and temperature comparisons to long-term normals
  • Temperature departures from normal (in ºC)
  • Percent normal of precipitation (in %)
  • Snow depth (in cm)

In addition, several crop models and data reduction algorithms are executed for both the station and satellite agrometeorological data sets. These models include crop calendars, crop hazards, and several different crop yield reduction models to assess crop conditions. Most of these crop models and computer tools were developed by researchers from various U.S. universities, government agencies, and private contractors.

Most of these models use daily potential evapotranspiration (PET) which is first calculated from minimum and maximum temperatures and station location (latitude, longitude, and elevation) according to the FAO 56 Penman-Monteith equation (Allen, et al, 1998). Precipitation, PET, and soil water-holding capacity are then utilized to run a two-layer soil moisture model within in CADRE to estimate:

  • Top- and sub-layer soil moisture (in mm)
  • Percent soil moisture in both soil layers (in %)

Many of the data sets produced by the crop models are not yet on-line, but GMA/IPAD in the near future plans to provide output data from these models. Future output products provided by GMA/IPAD will include the following:

  • Crop stage and crop stress for wheat and corn,
  • Relative yield reductions for corn, wheat, and soybeans,
  • Normalized Difference Vegetation Index (NDVI) images and anomalies.

Over the past twenty years, most of these agrometeorological variables and crop models were not made available to the public. However, current efforts are being made to display these spatial databases on a nearly real-time basis (every ten-days). The maps and graphs provided are specifically designed to monitor adverse weather conditions over the main agriculture regions in the world. Regional GMA/IPAD analysts then utilize this agrometeorological data, other high-resolution satellite imagery, FAS attaché crop reports, in-county sources, wire services, and personal knowledge to estimate national crop production by the 12th of each month.

Some basic information about the agrometeorological input data, climate normals, crop models, and data extraction routines are described below.

Ground Station and Satellite Data

Daily station data are originally from the Global Telecommunication System (GTS) of the WMO, which is a global network of more than 6000 stations (refer to Figure 1).

Figure 1. WMO Station Locations
Figure 1. WMO Station Locations

USDA’s Joint Agricultural Weather Facility (JAWF) receives the WMO station data from NOAA and provides GMA/IPAD with the following daily station data:

  • Minimum and maximum temperature
  • Precipitation

After downloading the WMO station data, GMA/IPAD then runs additional data reduction algorithms, soil moisture, crop stress, and relative crop yield reduction models, as well as CADRE extraction routines for the station data. The station data and output products are then compared to the satellite data to screen the satellite and station data sets for obvious errors.

Satellite Data & Grid Cell Size

The U.S. Air Force 557th Weather Wing (Formerly 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 CADRE 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).

Figure 2. 1/8-Mesh Grid Reference System for the Northern Hemisphere (from Hoke, et al, 1981)
Figure 2. 1/8-Mesh Grid Reference System for the Northern Hemisphere (from Hoke, et al, 1981)

Figure 3 illustrates the distribution of agrometeorological grid cells downloaded and archived by GMA/IPAD on a daily basis.

Figure 3 illustrates the distribution of agrometeorological grid cells downloaded and archived by GMA/IPAD on a daily basis.

The agrometeorology data sets downloaded daily for the grid cells in Figure 3 include the following:

  • Minimum and maximum temperature (Kopp, 1995)
  • Precipitation (Hollinger, 1989, and Kiess and Cox, 1988)
  • Snow depth (Luces, et al, 1986)
  • Solar and longwave radiation (Shapiro, 1987, Idso, 1981, and Watchmann, 1975)
  • Potential and actual evapotranspiration (Mahrt and Ek, 1984, and Ek and Mahrt, 1991)

The references for derivation of these agrometeorological variables are indicated above. After downloading the above agrometeorology data sets, soil moisture, crop stress, and relative crop yield reduction models as well as CADRE extraction routines are executed to display the various maps and graphs on the Internet.

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 and final data sources utilize WMO ground station data and geostationary satellites.

CADRE Baseline Data Sets

Development of the CADRE’s DBMS began in 1979 (Tingley, 1988) and it was one of the first GIS (Geographic Information Systems) DBMS designed specifically for global agricultural monitoring. CADRE is the operational outgrowth of the LACIE (Large Area Crop Inventory Experiment) and AgRISTARS (Agriculture and Resources Inventory Surveys Through Aerospace Remote Sensing) programs which began in 1974 and 1980, respectively (Boatwright and Whitefield, 1986). The main cooperating agencies for the LACIE and AgRISTARS programs were the National Oceanic and Atmospheric Administration (NOAA), National Aeronautics and Space Administration (NASA), and U.S. Department of Agriculture (USDA). These programs were the first joint effort by the U.S. government to use satellite imagery to continuously monitor and assess crop production over selected areas of the world. The AgRISTARS program followed the LACIE program and it developed many operational models and NOAA-AVHRR processing procedures currently used by GMA/IPAD and CADRE.

Twenty years ago, the original developers of CADRE had a unique geospatial vision although FORTRAN card readers were still used, storage capacity of computers were limited, and GIS (Geographic Information Systems) software were not yet available. CADRE’s current DBMS is essentially the same DBMS of twenty years ago. A flow chart of CADRE’s data stream is shown in Figure 4. Changes in operating systems and upgrading the baseline datasets are the main differences between the CADRE’s old and current systems. For example, CADRE was originally loaded in a DEC mainframe, later transferred to a DEC VAX system, and currently resides on a DEC UNIX server. Switching to different operating systems also entailed converting CADRE’s data archive, data extraction routines, and crop models into different operating environments. The latest switch to a UNIX environment made it possible to display output data from CADRE on the Internet and on a nearly real-time basis (every ten days).

Figure 4. Input Data Sets, Models, and Extraction Tools for CADRE
Figure 4. Input Data Sets, Models, and Extraction Tools for CADRE

The most recent upgrades to CADRE involved transferring new digital baseline databases developed by other agencies into CADRE’s 1/8-mesh grid reference system. For example, monthly grid cell normals for rainfall and temperature were recently extracted and imported into CADRE by utilizing the Leemans and Cramer (1991) 16-bit global climate images. These images also are available in 8-bit format from the FAO Climate Maps. These grid cell normal values are utilized in the precipitation and temperature time series graphs provided on-line by GMA/IPAD.

Other baseline normal data sets were improved by incorporating monthly station normals (from 1960-1990) provided by the WMO and NOAA. The soil water-holding capacities in CADRE were also upgraded by extracting values derived by the FAO (1996) Digital Soil Map of the World (DSMW). In addition, elevation and monthly potential evapotranspiration normals for the grid cells were derived from digital datasets developed by Row and Hastings (1997), and Ahn and Tateishi (1994), respectively.

Crop information within CADRE was also updated by compiling provincial crop yield and production data for most countries monitored by GMA/IPAD. Administration units at level-2 were utilized to store historical crop information because most national crop statistics are reported at this scale. These national crop statistics were then converted into ARCVIEW shape files and imported into CADRE’s 1/8-mesh grid cell format. Crop information updates are continuously required (average yield over the last five years) in efforts to make the relative crop yield reduction models more effective.

CADRE Soil Moisture and Crop Models

GMA/IPAD continuously assess and test operational crop models over large areas for accuracy and improvements. The crop models desired, chosen, and developed by GMA/IPAD over the years are those with minimum regression coefficients so that they have global applications. For example, some models deemed to have good results by the U.S. scientific community will not produce satisfactory results when implemented globally because these models use too many localized regression coefficients or were tested within limited number of areas.

The original soil moisture and crop models used by CADRE began development in 1978 and were implemented by the AgRISTARS program in the early 1980s, (Boatwright and Whitefield, 1986). These models are FORTRAN programs which extract daily station and gridded agrometeorological data described above. Personnel from the USDA, NOAA, NASA, and private contractors wrote the original crop models. The initial focus of crop model development was for the U.S. and Former Soviet Union (FSU). However, many of these models are currently being expanded for other counties throughout the world.

The two-layer soil moisture algorithm developed by the AgRISTARS program is the backbone algorithm that runs the crop calendar (growth stage) and crop stress (alarm) models. The two-layer soil moisture model is a bookkeeping method that accounts for the water gained or lost in the soil profile by recording the amount of water withdrawn by evapotranspiration and replenished by precipitation. The final aim of the soil moisture model is to estimate if soil moisture storage between dry spells was adequate for maximum plant growth.

Crop calendar models developed by the AgRISTARS program are accretion models that model the crop growth incrementally, based on growing degree-days (or thermal units) for several different types of crops and crop varieties. The crop calendar is a growing degree-day algorithm that uses daily minimum and maximum temperature measurements, as well as threshold temperatures defined by the particular crop type. The current crop calendar models are initialized by average start of season data derived from national crop reports. Future efforts will be made to initialize the crop models from start of season data derived from agrometeorological data or vegetation index numbers (VIN) stored in CADRE. The VIN database in CADRE is derived from the red and near-infrared channels from the NOAA-AVHRR satellite series as described by Bethel and Doorn, (1998).

Crop-stress models developed by the AgRISTARS programs use both the soil moisture and crop calendar algorithms, as well as a hazard algorithm to alert analysts of abnormal temperature or moisture stresses that may affect yields. These hazard algorithms are based on temperature and soil moisture thresholds known to be outside the optimal range of growing conditions and which may cause crop damage at various crop stages. For example, optimal growing conditions for corn is critical during the reproductive phase and the soil moisture and temperature thresholds are most sensitive during this stage. Therefore, if the plant experiences extreme water deficits or temperature conditions during the reproductive phase, the alarm model alerts the analysts of the crop stress in the region.

In addition, new crop models are constantly reviewed for possible integration into the operational systems of CADRE. For example, other crop models written by USDA and university researchers have been modified to run specifically from CADRE input data. In these cases, GMA/IPAD has work directly with the author of the crop model so that the model is running in-house with CADRE input data. These in-house models need a full growing season to get results and analysts will not use the models unless they feel the model agrees with ground conditions.

Most yield reduction models used by GMA/IPAD were written by other individuals outside of the AgRISTARS project and their models were customized to run from agrometeorological data extracted from CADRE. Yield reduction models begin with the assumption of perfect conditions and decrease yield predictions based on crop stresses. The goal of these crop models is to provide a yield estimate quantified as tons per hectare. Most of these models have a crop water production function algorithm which compares the crop yield with optimal water requirements to the actual water (rainfall) received by the crop.

Since no model is correct at all times for all geographic areas, analysts often run several models at once to reduce reliance on one particular model. The most recent trusted yield reduction models (used for lock-up analysis) are the Sinclair soybean (Sinclair, et al, 1991) and CERES wheat models (Richtie, et al, 1998). Of course, other information from other sources such as satellite imagery, in-county sources, FAS attaché reports, wire services, and personal knowledge are also used to decide how adverse weather conditions might have a significant impact on crop production.


GMA/IPAD has over two decades of experience in monitoring global weather data to maintain an early alert status of agricultural conditions that may alter regional yield potentials or effect international markets. During these two decades, GMA/IPAD has developed numerous algorithms to monitor agrometeorological variables and crop conditions throughout the world.

The most recent additions to CADRE have been introducing JAVA and PERL extraction routines to automatically generate maps and graphs. These images are then displayed on the Internet and are automatically updated on a dekadal basis. These improvements should allow more users and professionals (both inside and outside of GMA/IPAD) to view CADRE’s invaluable agricultural monitoring data sets.

On-going modifications include upgrading all crop models for global coverage because many of the original crop models were only designed for a few specific countries. The final result will be an upgraded geospatial information system with global coverage that will display agrometeorological and crop monitoring information on a nearly real-time basis. In summary, CADRE is a geospatial DBMS which stores numerous data sets and performs various modeling functions. A brief list of input data, climate normals, crop information and models, and data extraction routines performed within CADRE include:

Time-series data sets

  • Daily WMO station data (precipitation, min. and max. temperatures)
  • Daily agrometeorological data derived from station and satellite data, and imported into 1/8-mesh grid cells (precipitation; min and max temperatures; snow depth; solar and longwave radiation; potential and actual evapotranspiration).
  • Dekadal VINs (vegetation index numbers) derived from LAC (Local Area Coverage, approx 1.1-km pixels) data of the NOAA-AVHRR satellite series and imported into 1/8-mesh grid cells.
  • Biweekly VINs (vegetation index numbers) derived from GAC (Global Area Coverage, approx 8-km pixels) data of the NOAA-AVHRR satellite series and imported into 1/8-mesh grid cells.

Normal baseline data sets

  • Normal precipitation and temperature values for WMO stations (from WMO and NOAA)
  • Normal precipitation, temperature, potential evaporation, and elevation values imported into 1/8-mesh grid cells
    (from GRID Geneva)
  • Soil-water holding capacity imported into 1/8-mesh grid cells (from FAO’s DSMW, 1996)
  • Biweekly VIN normals for the GAC data set.

Crop Information and Models (for wheat, corn, and soybeans)

  • Crop type and average start of season
  • Average yield and area planted
  • Percent crop production within a country
  • Two-layer soil moisture algorithm
  • Crop calendars (based on growing-degree days)
  • Crop stress or alarm models for corn and wheat (based on soil moisture and temperature thresholds)
  • Crop water production functions to estimate relative yield reductions
  • Crop models by Ricthie

CADRE extraction routines

  • Automated maps and graphs generated every 10-days for display on Internet
  • Interactive ARCVIEW 3.2 scripts for displaying station and grid cell data
  • Interactive CADRE X-tract program for displaying graphs



USAF 557th WW U.S. Air Force 557th Weather Wing (Formerly AFWA)
AGREMET Agricultural Meteorology Model
AgRISTARS Agriculture and Resources Inventory Surveys Through Aerospace Remote Sensing
AVHRR Advanced Very High Resolution Radiometer
CADRE Crop Condition Data Retrieval and Evaluation
COTS Commercial Off-the Shelf Software
DBMS Database management system
DSMW Digital Soil Map of the World
EUMETSAT Europe's Meteorological Satellite Organization
FAO Food and Agriculture Organization
FAS Foreign Agricultural Service
FSU Former Soviet Union
GIS Geographic Information Systems
GMS Geostationary Meteorological Satellite
GOES Geostationary Operational Environmental Satellites
GTS Global Telecommunication System
IIASA International Institute for Applied Systems Analysis
JAWF Joint Agricultural Weather Facility
LACIE Large Area Crop Inventory Experiment
NASDA National Space Development Agency of Japan
NDVI Normalized Difference Vegetation Index
NOAA National Oceanic and Atmospheric Administration
GMA Global Market Analysis
PET Potential evapotranspiration
RTNEPH Real Time Nephanalysis Cloud Model
SSM/I Special Sensor Microwave/Imager)
USDA United States Department of Agriculture
VIN Vegetation index numbers
WMO World Meteorological Organization



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