Malheur Experiment Station Information for Sustainable Agriculture

2007 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 the Boise computer 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.

2007 Weather

The total precipitation for 2007 (7.47 inches) was lower than the 10-year (10.41 inches) and 64-year (10.11 inches) averages (Table 1). Total snowfall for 2007 (3.8 inches) was lower than the 10-year (14.0 inches) and 64-year averages (18.2 inches) (Table 2).

The highest air temperature for 2007 was 105°F on July 7 (Table 3). The lowest temperature for the year was 6°F on January 15.

The months of February, March, May, June, and July had a higher number of growing degree days (50° to 86°F) than the 21-year average (Table 4, Fig. 1). Compared to 2003, which had the highest total growing degree days and compared to the average, the pattern of growing degree day accumulation in 2007 showed a higher accumulation earlier in the season (Fig. 1). The total number of degree days in the above-optimal range (86° to 104°F) in 2007 was higher than the average (Table 5).

Monthly total wind runs were close to the 10-year and 59-year averages (Table 6). Windy weather in late March had peak wind gusts of 34, 45, 37, and 42 mph on March 25, 26, 27, and 28, respectively. This windy weather event was associated with displacement of planted onion and sugar beet seed. Total pan-evaporation for April, May, June, and July was higher than the 10-year and 59-year averages (Table 7). Total accumulated reference ET and ET_c for onions and dry beans in 2007 were the highest since data collection started in 1992 (Table 8).

The average monthly maximum and minimum 4-inch soil temperatures in 2007 were close to the 10-year and 40-year averages (Table 9).

The last spring frost ([32°F) occurred on May 4, 6 days later than the 31-year-average date of April 28; the first fall frost occurred on October 11, 5 days later than the 31-year-average date of October 6 (Table 10).

The year 2007 had the highest reference evapotranspiration since 1992, when the AgriMet station was installed at the Malheur Experiment Station (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, 1991-2007.

Table 2. Annual snowfall totals at the Malheur Experiment Station, Oregon State University, Ontario, OR, 1991-2007.

Table 3. Monthly air temperature, Malheur Experiment Station, Oregon State University, Ontario, OR, 2007.

Figure 1. Cumulative growing degree days (50-86°F) over time for years with lowest (1993) and highest (2003) totals compared to 2007 and to 17-year average (1990-2006), 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, 1991-2007.