Malheur Experiment Station Information for Sustainable Agriculture

2009 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. Start dates are the beginning of vegetative growth in the spring for perennial crops or the emergence date for row crops.  Full cover dates typically are 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.  Data are annual from January to December starting when equipment was installed.  Mid years are not counted.

2009 Weather

The total precipitation for 2009 (11 inches) was slightly higher than the 10-year (9.45 inches) and 66-year (10.03 inches) averages (Table 1).  Precipitation for June (2.27 inches) was the highest since 1943.  Total snowfall for 2009 (13.8 inches) was the same as the 10-year average (13.8 inches), but lower than the 66-year average (18.2 inches) (Table 2).

The highest air temperature for 2009 was 102°F on July 23 (Table 3).  The lowest temperature for the year was -2°F on December 10. 

March had fewer accumulated growing degree days (50° to 86°F) than the 23-year average (Table 4, Fig. 1).  April, May, June, July, and August had total growing degree days close to average.  September had a higher number and October had a lower number of  accumulated growing degree days than the 23-year average.  The total number of degree days in the above-optimal range (86° to 104°F) in 2009 was close to  the average (Table 5). 

Total wind runs for May, June, and July were lower than the 17-year average (Table 6).  Total pan-evaporation for April and September was higher than the 10-year and 61-year averages (Table 7); for June, August, and October it was lower than the 10-year average.  In 2009, total accumulated reference ET and ET_c for all crops were close to the 16-year average (Table 8).

The average monthly maximum and minimum 4-inch soil temperatures for December 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 13, 15 days later than the 33-year-average date of April 28; the first fall frost occurred on October 1, 5 days earlier than the 33-year-average date of October 6 (Table 10). 

No local weather records were broken in 2009, but June had the highest precipitation since observations were first recorded in 1943 (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, 2000-2009.

Table 2.  Annual snowfall totals (inches) at the Malheur Experiment Station, Oregon State University, Ontario, OR, 1992-2009.

Table 3. Maximum and minimum air temperatures by month,  Malheur Experiment Station, Oregon State University, Ontario, OR, 2009.

Figure 1. Cumulative growing degree days (50-86°F) over time for years with lowest (1993) and highest (2003) totals since 1990, compared to 2009 and to 19-year average (1990-2008), 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, 1991-2009. Average is from 1986 through 2008.

Table 5.  Monthly total degree days in the above-ideal (86-104°F) range, Malheur Experiment Station, Oregon State University, Ontario, OR, 1991-2009.

Table 6.  Daily wind-run and monthly totals, Malheur Experiment Station, Oregon State University, Ontario, OR, 2009.

Table  7. Daily pan-evaporation and monthly totals, Malheur Experiment Station, Oregon State University, Ontario, OR, 2009.

Table 8. Total accumulated reference evapotranspiration (ET₀) and crop evapotranspiration (ET_c) (acre-inches/acre), Malheur Experiment Station, Oregon State University, Ontario, OR, 1992-2009.

Table  9. Monthly soil temperature at 4-inch depth, Malheur Experiment Station, Oregon State University, Ontario, OR, 2009.

Table 10.  Last and first frost ([32°F) dates and number of frost-free days, Malheur Experiment Station, Oregon State University, Ontario, OR, 1990-2009.

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

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Last updated  Tuesday July 19, 2011.

Feibert, E.B.G. and C.C. Shock. 2010. 2009 Weather Report. p 1-9 In Shock C.C. (Ed.) Oregon State University Agricultural Experiment Station, Malheur Experiment Station Annual Report 2009, Department of Crop and Soil Science Ext/CrS 131.