AZMET : The Arizona Meteorological Network : A Brief Overview
by Bruce Russell ; AZMET Program Coordinator
As a Land Grant institution, the University of Arizona has had a long and proud history of
managing a wide array of Cooperative Extension projects which benefit the state of Arizona.
During the mid-1980s the College of Agriculture experienced a dramatic increase in the number
outreach programs and personnel. One of these projects was the establishment of an automated
weather data collection network to monitor conditions in the state. The Arizona Meteorological
Network (AZMET) began full operation in January of 1986 with the mission to provide
meteorological data and weather-based information for agricultural and horticultural
interests operating in southern and central Arizona. For more than 25 years, AZMET has worked
in partnership with Arizona communities, assisted state and federal agencies, provided education
programs and has conducted many fundamental and applied research projects.
The meteorological data collected by AZMET include temperature (air and soil), humidity, solar
radiation, wind (speed and direction), and precipitation. AZMET also provides a variety of
computed variables, including heat units (degree-days), chill hours, dew point and reference crop
evapotranspiration (ETo). AZMET data are summarized in a variety of formats, including several
ready-to-use summaries and comma-delimited (raw) ASCII text files that can be imported
into most database and spreadsheet programs. Special reports generated by AZMET include
daily Turf Water Use Reports and Weekly Cotton Advisories.
Currently, the AZMET network has 27 stations operating in a variety of rural and urban
production settings. Each station is a solar-powered, self-contained unit. A ten foot tower
supports the wind instruments and other sensors. The heart of the station is an electronic data
storage module, known as a datalogger, which continuously reads the sensors.
These measurements are stored in memory every hour. Just after midnight, a computer in the
AZMET offices on the University of Arizona campus automatically calls each station's datalogger
and downloads the previous day's data. This raw data is evaluated by a series programs which
process the raw values into various user-friendly reports. It is during this procedure that derived
values such as heat units, dew point and evapotranspiration are generated. These files are then
transferred onto a web server and are usually available to the public by about 1 am each day.
Preventative maintenance of the station instrumentation is essential to collecting accurate data.
An AZMET technician visits each station at least every three months. During these visits, a
separate set of laboratory-standard sensors is set up next to the existing station and a comparison
is made. Wind speed and solar sensors are removed and recalibrated once per year. The sensor
that measures temperature and humidity is recalibrated every two years.
Due to inconsistent yields and limited water, the state's cotton industry has had a several rough
seasons in past years. However, during the 2002 season, the value of cotton production in
over $167 million dollars. Cotton remains a major segment of Arizona agriculture and an
important part of the state economy. Every Monday from March through August, AZMET
generates nineteen different Cotton Advisories for various cotton production regions across
The life cycles of many plant and insects are driven by changes in temperature. The heat units
(aka: degree days) which AZMET calculates, allow growers and researchers to track the stages
of development in cotton plants and aid in predicting the outbreak of pests such as the
infamous pink bollworm. Preventative pesticides can then be targeted at specific time, thus
limiting the amount of chemicals released into the environment and saving money.
Early in the season, the AZMET Planting Advisory provides information about soil temperatures
for seed germination. By adjusting the planting date, growers can avoid having the crop
reach a susceptible stage of development during a projected hatching of pink bollworms.
After planting, the advisories use heat units to track the cotton plants through their life cycle.
The current year's temperatures, dew point and rainfall are compared to historical data; present
conditions are reported as being ahead or behind past climate normals. A brief forecast describes
the possible effect of weather systems that are entering the state. Also included are crop water use
estimates and crop stress values. This information is critical to maintain boll retention and
produce a marketable crop.
Evapotranspiration (ET) is the water that is lost to the atmosphere from surface evaporation and
from plant transpiration. This process is largely driven by solar energy and wind speed.
Evapotranspiration is a major component of the earth's water cycle. In most continental areas,
evapotranspiration accounts for about 60% of the hydrologic activity in a basin. Here in the
southwest, due to the lack of cloud cover, ET has an even larger role in the hydrologic budget.
Because it is less tangible than other meteorological parameters, evapotranspiration is often not
given proper attention in water budgets, if it is included at all. The monitoring of precipitation,
snowpack, lakes, streams, reservoirs and groundwater levels tells us how much water is entering
and being held in a basin. ETo give us the other side of the hydrologic cycle; it tracks the amount
water that can potentially be lost from a basin and returned to the atmosphere. In the southern
part of the state, an open body of water, such as a lake, canal or uncovered swimming pool,
can lose about 80 inches of water to evaporation each year. Normal rainfall during the same
period, only averages around 8 to 10 inches. During periods of drought, the significance of ETo in
the hydrologic cycle is further accentuated. A census of data collection organizations indicates
that AZMET is the only group which has been continuously monitoring ETo in Arizona.
Each species of plant has it's own unique water requirements; the evapotranspiration must be
adjusted for different crops. By using AZMET crop water use values, a grower can apply
the necessary amount of water which meets the plant's demand. Under watering will stress the
plant and cause low yields; while over watering would waste a limited resource.
Turf and Lawn
Although it is not considered as traditional agriculture, turf horticulture plays an important role in
the state's economy. A recent study of the Arizona golf industry provides some interesting
statistical insights. There are more than 330 golf courses in Arizona. Over 2 million visitors play
golf in Arizona. Golf produces $45 million in state taxes; $24 million in local taxes.
Since it's inception in 1987, AZMET has worked closely with the turf industry in an effort
conserve water. Three stations in the Phoenix area are located on golf courses and are supported
by the City of Phoenix Water Conservation Dept. AZMET has done extensive research to
determine the water requirements of both warm and cool season grasses in Arizona's desert
environment. Each day, AZMET generates Turf Water Use Reports for the Tucson and Phoenix
areas. These reports track the water requirements over the most recent seven days.
Also included are the totals of any precipitation. By using this information, an irrigation manager
can apply the correct amount of water on a turf surface. AZMET also provides lawn watering
values to homeowners in the Phoenix area. In November 2003, the three new stations were added
to the network. These stations are located on turf facilities in Flagstaff, Prescott and Payson to aid
in the water conservation efforts of these northern communities.
During the spring of each year, AZMET generates a twice daily frost report for the apple
producers in the Bonita area north of Willcox. Among the causalities of the 1995/96 federal
budget crisis was the closing of the National Weather Service office in Yuma Arizona.
Citrus growers and related agribusiness interests were left without any source of local
information. AZMET stepped forward and filled the gap; supplying critical frost updates several
times per day. The experimental farm in Yuma is currently using AZMET's chill hours to do
research on citrus trees which require a certain number of winter hours below 68 degrees to
properly bud and produce fruit.
AZMET has provided data and information to assist agriculturalists growing other crops as well.
In the spring and summer, AZMET reports water-use recommendations for corn and alfalfa.
A special corn heat-stress report is provided when needed.
A small grains advisory uses AZMET data to track the development of wheat and barley crops.
These reports also provide current and projected water use. The efficiency of melon and
vegetable harvesting has been increased by the use of heat units. Grapes are a crop that is
susceptible to extreme temperatures, and AZMET offers recommendations based on climate to
the vineyard industry.
Dairies have utilized AZMET data to reduce heat stress on cattle and thus increase milk
production. The growing aquaculture industry has requested information on temperature,
humidity, wind speed and wind direction. AZMET data has even been used for non-agricultural
purposes, including calculating environmental cooling-system design, building alignment, and
Throughout it's history, AZMET has worked with many different organizations. These include
Arizona Department of Water Resources (ADWR), Arizona Municipal Water Users Association
(AMWUA), the Bureau of Reclamation, USGS, university departments, water conservation
programs, and city water companies. AZMET's major responsibility is to provide outreach
to the agricultural, horticultural and other water-related interests. Stakeholders include irrigation
districts, turf facilities, golf courses, cotton growers, fertilizer and pesticide companies,
citrus growers, vegetable producers and other agribusiness organizations.
These cooperative partnerships have resulted in both applied research and beneficial outreach
programs. During 2003 there were over 137,000 visits to the AZMET website, with users
accessing the data files more than 530,000 times; over 1450 requests per day.
The original 1986 start-up funds allowed for the purchase of 10 weather stations and hiring of
two people. Currently, the AZMET network has 27 stations operating in a variety of rural and
urban production settings. Due to recent state budget cuts, AZMET is currently relying on
private donations to support it's operations. These funding uncertainties make long-range planning
difficult at best; it might be necessary to remove or relocate stations as funding and logistical
The ongoing drought and population growth will necessitate close monitoring of the limited water
resources throughout the Southwest. Due to the changing role of agriculture and increasing
degree of urbanization, AZMET has an obligation to modify and expand its mission in an effort to
meet the evolving needs of our state. By strengthening past partnerships, forging new allegiances,
and addressing future problems through applied research, AZMET will continue to be important
and reliable source of weather data and information for the people of Arizona.
All available AZMET weather data and more information
about the Arizona Meteorological Network can be found on the website :