Malheur Experiment Station Information for Sustainable Agriculture

2008 WEATHER REPORT

Erik B. G. Feibert and Clinton C. Shock

Malheur Experiment Station

Oregon State University

Ontario, OR

Introduction

Air temperature and precipitation have been recorded daily at the Malheur Experiment Station since July 20, 1942. Installation of additional equipment in 1948 allowed for evaporation and wind measurements. A soil thermometer at 4-inch depth was added in 1967. A biophenometer, to monitor degree days, and pyranometers, to monitor total solar and photosynthetically active radiation, were added in 1985.

Since 1962, the Malheur Experiment Station has participated in the Cooperative Weather Station system of the National Weather Service. The daily readings from the station are reported to the National Weather Service forecast office in Boise, Idaho.

Starting in June 1997, the daily weather data and the monthly weather summaries have been posted on the Malheur Experiment Station web site on the internet at www.cropinfo.net.

On June 1, 1992, in cooperation with the U.S. Department of the Interior, Bureau of Reclamation, a fully automated weather station, linked by satellite to the Northwest Cooperative Agricultural Weather Network (AgriMet) computer in Boise, Idaho, began transmitting data from Malheur Experiment Station. The automated station continually monitors air temperature, relative humidity, dew point temperature, precipitation, wind run, wind speed, wind direction, solar radiation, and soil temperature at 8-inch and 20-inch depths. Data are transmitted via satellite to a computer in Boise every 4 hours and are used to calculate daily Malheur County crop water-use estimates. The AgriMet database can be accessed through the internet at www.usbr.gov/pn/agrimet and from links on the Malheur Experiment Station web page at www.cropinfo.net.

Methods

The ground under and around the weather stations was bare until October 17, 1997, when it was covered with turfgrass. The grass is irrigated with subsurface drip irrigation. The weather data are recorded each day at 8:00 a.m. Consequently, the data in the tables of daily observations refer to the previous 24 hours.

Evaporation is measured from April through October as inches of water evaporated from a standard class A pan (10 inches deep by 4-ft diameter) over 24 hours. Evapotranspiration (ET_c) for each crop is calculated by the AgriMet computer using data from the AgriMet weather station and the Kimberly-Penman equation (Wright 1982). Reference evapotranspiration (ET₀) is calculated for a theoretical 12- to 20-inch-tall crop of alfalfa assuming full cover for the whole season. Evapotranspiration for all crops is calculated using ET₀ and crop coefficients for each crop. These crop coefficients vary throughout the growing season based on the plant growth stage. The crop coefficients are tied to the plant growth stage by three dates: start, full cover, and termination dates. Start dates are the beginning of vegetative growth in the spring for perennial crops or the emergence date for row crops. Full cover dates are typically when plants reach full foliage. Termination dates are defined by harvest, frost, or dormancy. Alfalfa mean ET_c is calculated for an alfalfa crop assuming a 15 percent reduction to account for cuttings.

Wind run is measured as total wind movement in miles over 24 hours at 24 inches above the ground. Weather data averages in the tables, except evapotranspiration, refer to the years preceding and up to, but not including, the current year.

2008 Weather

The total precipitation for 2008 (7.62 inches) was lower than the 10-year (10.21 inches) and 65-year (10.07 inches) averages (Table 1). Total snowfall for 2008 (26.0 inches) was higher than the 10-year (14.0 inches) and 65-year averages (18.2 inches) (Table 2).

The highest air temperature for 2008 was 100°F on June 30 and July 4 (Table 3). The lowest temperature for the year was -4°F on January 24.

March and April had fewer accumulated growing degree days (50° to 86°F) than the 22-year average (Table 4, Fig. 1). Growing degree days accumulated in March were 22 percent of average, and the lowest since 1991 when records began. Growing degree days accumulated in April were 57 percent of average. May, June, July, and August had total growing degree days close to average. The total number of degree days in the above-optimal range (86°to 104°F) in 2008 was close to the average (Table 5).

Total wind runs for May and June were 28 percent and 19 percent above the 17-year average (Table 6). Total pan-evaporation for May and June was 14 percent and 13 percent higher, respectively, than the 10-year average (Table 7). In 2008, total accumulated reference ET and ET_c for all crops except poplar were higher than the 16-year average (Table 8).

The average monthly maximum and minimum 4-inch soil temperatures from January through April were lower than the 10-year average (Table 9). Four-inch soil temperatures for the other months were close to the average.

The last spring frost ([32°F) occurred on May 2, 4 days later than the 32-year-average date of April 28; the first fall frost occurred on October 13, 7 days later than the 32-year-average date of October 6 (Table 10).

No local weather records were broken in 2008, but March had the fewest growing degree days since observations were first recorded in 1991 (Table 11).

References

Wright, J.L. 1982. New evapotranspiration crop coefficients. Journal of Irrigation and Drainage Division, American Society of Civil Engineers 108:57-74.

Table 1. Monthly precipitation at the Malheur Experiment Station, Oregon State University, Ontario, OR, 1991-2008.

Table 2. Annual snowfall totals at the Malheur Experiment Station, Oregon State University, Ontario, OR, 1991-2008.

Table 3. Maximum and minimum air temperatures by month, Malheur Experiment Station, Oregon State University, Ontario, OR, 2008.

Figure 1. Cumulative growing degree days (50-86°F) over time for years with lowest (1993) and highest (2003) totals compared to 2008 and to 18-year average (1990-2007), Malheur Experiment Station, Oregon State University, Ontario, OR.

Table 4. Monthly total growing degree days (50-86°F), Malheur Experiment Station, Oregon State University, Ontario, OR, 1991-2008.

Table 5. Monthly total degree days in the above-ideal (86-104°F) range, Malheur Experiment Station, Oregon State University, Ontario, OR, 1991-2008.

Table 6. Daily wind-run and monthly totals, Malheur Experiment Station, Oregon State University, Ontario, OR, 2008.

Table 7. Daily pan-evaporation and monthly totals, Malheur Experiment Station, Oregon State University, Ontario, OR, 2008.

Table 8. Total accumulated reference evapotranspiration (ET₀) and crop evapotranspiration (ET_c) (acre-inches/acre), Malheur Experiment Station, Oregon State University, Ontario, OR, 1992-2008.

Table 9. Monthly soil temperature at 4-inch depth, Malheur Experiment Station, Oregon State University, Ontario, OR, 2008.

Table 10. Last and first frost ([32°F) dates and number of frost-free days, Malheur Experiment Station, Oregon State University, Ontario, OR, 1990-2008.

Table 11. Record weather events at the Malheur Experiment Station, Oregon State University, Ontario, OR.

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Last updated  Tuesday June 28, 2011.