The CoAgMet Network: Overview,
History and How It Works
Wendy Ryan
Colorado Climate Center
Colorado State University
History
►
►
►
In the early 1990’s, CSU extension plant pathologists and
ARS scientists decided to collaborate efforts to collect
detail agricultural weather data.
Standard instruments and data collection platform were
selected and a small network of stations was deployed in
fully irrigated agriculture.
As the network grew, the Colorado Climate Center
became increasingly interested in using the data, began
daily data collection, quality control and built a web
interface to distribute data and products to users across
the state.
CoAgMet 1992
CoAgMet 1997
CoAgMet 2002
CoAgMet Today
Overview
► Currently
there are 64 stations
► Data are collected on hourly and daily
time steps and include: temperature,
humidity, solar radiation, wind speed and
direction, and soil temperatures.
► Data and graphics are available online:
ccc.atmos.colostate.edu/~coagmet
What do the stations measure?
Cup anemometer
and wind vane:
2m
Wind speed,
direction and gusts
Temperature/Humidity
sensor in radiation
shield
Above all
else facing
South
2m
Solar panel
powers the
station
1-3 m
Pyranometer:
Solar radiation
Tipping
bucket rain
gage
Data collection
platform (DCP)
-5/-15 cm
Soil
temperatures
Data Collection Platform
Power
supply
Datalogger
Communications
device (cellular
modem)
Incoming
sensor
cables
Why these measurements?
►
►
The main goal of CoAgMet is to calculate
evapotranspiration (ET) from meteorological
measurements.
Several models exist that vary by input data and
complexity:




►
Penman-Monteith – physically based
Kimberly-Penman – physically based
Hargreaves – empirical temperature based
Standardized ASCE Equation – attempts to standardize
calculations to make them more comparable
The standard CoAgMet station collects the elements
needed to calculate evapotranspiration.
Temperature/Humidity
Temperature: During the growing
season, higher temperatures
cause the plant stoma to open
resulting in greater transpiration.
Humidity: The higher the humidity
the less transpiration will occur
(more transpiration occurs in
dryer air)
Wind Movement
► As
air moves across
plants it will cause
more transpiration as
saturated air (from
transpiration) around
the plant is mixed and
dryer air can move in.
Solar Radiation
► Alfalfa
only reflects about
25% of incoming solar
energy which leaves ample
solar energy to drive ET
rates.
► ET trends follow a similar
pattern as seasonal solar
radiation and air
temperature.
Precipitation
► While
precipitation
data is not explicitly
used in the ET
equations, it does
affect crop coefficients
used at different
locations.
► Monitoring
precipitation also
provides an idea of soil
moisture availability at
the station.
Soil Temperatures
► Having
the temperature of the soil aids in
knowing when the soil has warmed enough
to plant.
► Soil temperature also gives an indication of
the amount of ground cover at the station.
Problems with CoAgMet
► Missing
► Site
data
exposure
► Routine
maintenance
Missing/Questionable Data
► Due
to various problems that occur to
remote weather stations, missing data
causes problems for users.
► Battery failure and communications
problems are the most common.
► Even if the whole station doesn’t fail,
sensors go bad and can leave some
elements missing until the station is
serviced.
• Unfortunately, data are not complete at
all stations
Peckham, Mean Monthly Wind Run (May-Sept)
250
Missing Data
Wind Run (mi)
200
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
Mean
150
100
50
0
March
April
May
June
July
Month
August
September
October
Some Data are Questionable
CSU Fruita Experimental Station, Monthly Vapor Pressure (1992-2006)
18.00
1992
1993
1994
16.00
1995
Vapor Pressure (mb)
14.00
1996
1997
12.00
1998
10.00
1999
Avondale, Mean Monthly Solar Radiation (1992-2006)
2000
8.00
2001
700
2002
6.00
1992
2003
4.00
1994
1995
Mean
March
April
May
June
July
August
September
October
Month
Lamar 01, Mean Monthly Vapor Pressure (1998-2006)
20.00
1998
2001
2004
Mean
1999
2002
2005
2000
2003
2006
Solar Radiation (Lgly)
2006
0.00
16.00
600
2005
2.00
18.00
1993
2004
500
1996
1997
400
1998
1999
2000
300
2001
2002
200
2003
2004
100
Vapor Pressure (mb)
2005
14.00
2006
0
12.00
March
April
May
June
July
Month
10.00
8.00
6.00
4.00
2.00
0.00
March
April
May
June
Month
July
August
September October
August September October
Mean
Site Exposure
► One
of the assumptions of the evapotranspiration
equations is that water is not limited (i.e. in full
irrigation).
► Some stations are not located in ideal “reference”
conditions.
► Some stations have obstructions (buildings/crops)
that affect the amount of wind in certain
directions.
► The exposure of the site can have an impact on
the data and over/under estimate reference ET.
Siting and Exposure
The Good…
FTC01 Fort Collins AERC has
appropriate citing for reference ET
calculations
and the Not so Good
HOT01 Hotchkiss is not ideally cited
for reference ET calculations
Routine Maintenance
► Due
to the fact that CoAgMet is run by
collaborations and operates on a limited budget,
routine maintenance is difficult with such a large
network.
 There is no full time CoAgMet technician.
► Our
goal is to service a station once every 2 years.
► Data users should be cautious and thoroughly
quality control the data they are using.
Possible Solutions?
► Efforts
are being made to fill in missing data
using relationships with nearby stations.
 This data would be flagged when presented on
the website.
► Our
website now color codes stations
according to their irrigation are classified as:
full irrigation, partial irrigation and dryland.
 Making this information available to the public
allows them to know more about their data
source.
Possible Solutions?
► We
due our best with limited funds to keep
a maintenance schedule but it is very
difficult.
► If we are not able to keep high standards
for our weather stations, some current
stations may need to be discontinued in the
near future.
► If you value the CoAgMet network, consider
donating funds to help sponsor a station in
your area!
CoAgMet Website
Demonstration
The Colorado Climate Center Home
Page
http://ccc.atmos.colostate.edu/
Hourly Climate Data Plots
Click Here
Hourly Climate Data Plots
GLY03 Greely June 9, 2007 through June 15, 2007
Temperature
Relative Humidity
Daily Climatic Summary
Click Here
Daily Climatic Summary
Monthly Station Summaries
Click Here
Monthly Station Summaries
KSY01 – Kersey Aug. 2007
Daily Regional Climatic and ET
Comparison
Click Here
Daily Regional Climatic and ET
Comparison
North Central Region, May 30, 2007
Crop Specific ET Reports
Click Here
Crop Specific ET Reports
•Calculates multi-day ET for: alfalfa, corn, dry beans, small
grain, sugar beets, potatoes, onion, winter wheat, turf grass, and
reference ET, via Penman-Monteith or Kimberly-Penman
CoAgMet web access:
http://ccc.atmos.colostate.edu/~coagmet/