2006 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

Evaporation is measured from April through October as inches of water evaporated from a standard class A pan (10-inch-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.

2006 Weather

The total precipitation for 2006 (12.79 inches) was higher than the 10-year (10.38 inches) and 63-year (10.07 inches) averages (Table 1). Precipitation in March (3.33 inches) was over three times higher than the 10-year and 63-year averages, whereas April (2.0 inches) was two and a half times higher. Total snowfall for 2006 (12 inches) was lower than the 10-year (14.0 inches) and 63-year (18.2 inches) averages (Table 2).

The highest temperature for 2005 was 106°F on July 23 (Table 3). The lowest temperature for the year was 10°F on February 18,19, and 20.

March and April had fewer growing degree days (50° to 86°F) than the 20-year average (Table 4, Fig. 1). May, June, and August had more growing degree days (50° to 86°F) than the 20-year average. The total number of degree days in the above-optimal range (86^o to 104^oF) in 2006 was higher than the average (Table 5). July had twice as many above-optimal degree days as the 16-year average.

June and July had total wind runs higher than the 10-year and 58-year averages (Table 6). Total pan-evaporation for June and July was higher than the 10-year and 58-year averages (Table 7). Total accumulated ET_c for most crops in 2006 was higher than the 14-year average (Table 8).

The average monthly maximum and minimum 4-inch soil temperatures in 2006 were close to the 10-year and 39-year averages (Table 9).

The last spring frost (32°F) occurred on April 19, 9 days earlier than the 29-year average date of April 28; the first fall frost occurred on October 22, 17 days later than the 29-year average date of October 5 (Table 10). No weather records were broken in 2006 (Table 11).

References

Table 1. Monthly precipitation at the Malheur Experiment Station, Oregon State University, Ontario, OR, 1991-2006.

Table 2. Annual snowfall totals at the Malheur Experiment Station, Oregon State University, Ontario, OR, 1991-2006.

Figure 1. Cumulative growing degree days (50-86°F) over time for selected years compared to 16-year average, 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, 1991-2006.