2000 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 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.

On June 1, 1992, in cooperation with the U.S. Department of the Interior, Bureau of Reclamation, a fully automated weather station, connected 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 is transmitted via satellite to the Boise computer every 4 hours and is used to calculate daily Malheur County crop water-use estimates. The AgriMet database can be accessed via computer modem or through the Internet at www.pn.usbr.gov/agrimet and is linked to the Malheur Experiment Station web page at www.cropinfo.net.

Starting on 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.

Methods

The ground under and around the weather stations had been bare, but was covered with turf grass on October 17, 1997. The grass is irrigated with subsurface drip irrigation. The weather data is recorded each day at 8:00 a.m.

Evaporation is measured from April through October as inches of water evaporated from a standard 10-inch deep by 4-ft diameter pan over 24 hours. Evapotranspiration (Et) for each crop is calculated by the AgriMet computer using data from the AgriMet weather station and the Kimberly-Penman equation (Wright, 1982). Reference Et is calculated for a theoretical 12-to 20-inch-tall crop assuming full cover for the whole season. Alfalfa peak Et is calculated assuming that the alfalfa is kept uncut during the season. Alfalfa mean Et is calculated assuming a 15 percent reduction to account for cuttings. Alfalfa peak Et would be the same as reference Et when the alfalfa reaches full cover. Evapotranspiration for all crops is calculated using the reference Et and factors for each crop that vary during the season depending on the degree of cover.

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 refer to the years preceding and up to, but not including, the current year.

2000 Weather

The year started wetter than normal, but the spring and summer were drier than normal. The total precipitation from January through March was 57 and 58 percent higher than the 10-year and 55-year averages, respectively (Table 1). The total precipitation from April through August was 1.35 inch, which was 68 and 60 percent lower than the 10-year and 55-year averages, respectively. The total precipitation for 2000 was close to the 10-year and 55-year averages.

The months of April through August had a higher number of growing degree days (50 to 86°F) than normal (Table 2). The months of September through December had a lower number of growing degree-days (50 to 86°F) than normal. The total number of growing degree-days in 2000 was close to the 10-year and 14-year averages (Table 2). The total number of growing degree-days in 2000 was close to the 10-year average. Since 1990, the year 1994 had the highest total growing degree-days and 1993 had the lowest total growing degree-days (Fig. 1). July and August combined had 17 percent more degree days in the above optimal range (86 to 104°F) than the previous 10-year average (Table 3). There were nine percent more total degree-days in the above optimal range in 2000 than the previous 10-year average.

The months of May through September had total wind runs higher than the 9-year average (Table 4). Total pan-evaporation for June through August was 13 percent higher than the 10-year average and 20 percent higher than the 50-year average (Table 5). Total pan-evaporation for 2000 was higher than the 10-year and 55-year averages.

Total Et for all crops in 2000 was higher than the 8-year mean (Table 6). Total Et for alfalfa, sugar beet, onion, potatoes, and field corn in 2000 was the highest since 1992. Reference Et in 2000 was also the highest since 1993.

Mean monthly air temperatures were close to the 10-year and 53-year average (Table 7).

From March through October the mean monthly maximum and minimum four-inch soil temperatures were lower than the 10-year and 33-year average (Table 8). The difference in soil temperature between 2000 and the mean is probably influenced by the installation of turf around the weather station in October of 1997. The soil remained warmer in winter and cooler in spring and summer. The last spring frost ([32°F) occurred on May 12, 15 days later than the 24-year average date of April 27; the first fall frost occurred on September 24, 11 days earlier than normal (Table 9).

The weather in 2000 did not exceed any record weather events recorded over the 57-year history for the Malheur Experiment Station (Table 10). The highest temperature for the year was 102°F on August 2 (Table 6). The lowest temperature for the year was 8°F on January 6. Total precipitation was 9.64-inches for the year, slightly lower than the 10-year station average and the 55-year station average (Table 1). Total pan-evaporation for April through October was 60.8 inches, slightly higher than the 10-year and 52-year average (Table 4). Total snowfall for 2000 was 13.8 inches, lower than the 10-year and 57-year average (Table 11).

Literature Cited

Wright, J.L. 1982. New evapotranspiration crop coefficients. J. Irrig. Drain. Div., ASCE 108: 57-74.

Table 1. Monthly precipitation at the Malheur Experiment Station, Oregon State University, Ontario, OR, 1990-2000.
Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total
  ----------------------------------------- inches -----------------------------------------------
1990 0.44 0.35 0.72 1.52 1.70 0.36 0.04 0.61 0.00 0.49 0.69 0.29 7.21
1991 0.59 0.44 0.88 0.81 1.89 1.09 0.01 0.04 0.35 1.01 1.71 0.43 9.25
1992 0.58 1.36 0.25 0.74 0.21 1.43 0.36 0.01 0.09 0.95 1.15 1.51 8.64
1993 2.35 1.02 2.41 2.55 0.70 1.55 0.18 0.50 0.00 0.80 0.64 0.60 13.30
1994 1.20 0.57 0.05 1.02 1.62 0.07 0.19 0.00 0.15 1.23 2.46 1.49 10.05
1995 2.67 0.28 1.58 1.16 1.41 1.60 1.10 0.13 0.07 0.57 0.88 2.56 14.01
1996 0.97 0.86 1.03 1.19 2.39 0.12 0.32 0.31 0.59 0.97 1.18 2.76 12.69
1997 2.13 0.17 0.25 0.66 0.67 0.86 1.40 0.28 0.40 0.43 1.02 0.94 9.21
1998 2.26 1.45 0.95 1.43 4.55 0.36 1.06 0.00 1.00 0.04 1.07 1.11 15.28
1999 1.64 2.50 0.59 0.23 0.28 1.02 0.00 0.09 0.00 0.40 0.49 0.73 7.97
2000 2.01 2.14 0.97 0.72 0.28 0.26 0.03 0.06 0.39 1.74 0.38 0.66 9.64
10-yr avg 1.48 0.90 0.87 1.13 1.54 0.85 0.47 0.20 0.27 0.69 1.15 1.25 10.80
55-yr avg 1.35 0.96 0.95 0.81 1.08 0.80 0.26 0.41 0.50 0.69 1.19 1.33 10.33

Figure 1. Cumulative growing degree-days (50 to 86°F) for selected years, Malheur Experiment Station, Oregon State University, Ontario, OR, 2000.

Table 2. Monthly total growing degree-days (50-86°F), Malheur Experiment Station, Oregon State University, Ontario, OR, 1990-2000.
Year
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total
1990 79  239  261  497  734  635  585  38  3,077
1991 13  16  124  212  389  776  718  436  194  2,879
1992 13  106  202  482  574  639  704  385  174  3,283
1993 23  81  423  358  464  524  408  252  2,539
1994 92  189  369  523  794  774  509  144  3,398
1995 29  32  106  293  433  680  588  472  101  10  2,747
1996 53  135  243  446  805  658  364  194  18  2,923
1997 81  117  419  509  661  706  481  157  20  3,154
1998 52  112  68  571  802  749  515  151  16  3,042
1999 43  72  329  459  683  703  416  184  30  2,921
2000 36  194  342  536  751  743  368  133  3,109
14-year avg  58  138  310  476  704  676  457  159  10  3,049

Table 3. Monthly total degree-days (86 -104°F), Malheur Experiment Station, Oregon State University, Ontario, OR, 1990-2000.
Year Apr May Jun Jul Aug Sep Oct Total
1990 0 0 13 56 41 14 0 124
1991 0 0 2 41 36 4 0 83
1992 0 5 20 23 54 2 0 104
1993 0 4 4 2 11 5 0 26
1994 0 2 16 68 54 7 0 147
1995 0 0 4 23 22 7 0 56
1996 0 0 5 54 32 4 0 95
1997 0 4 0 27 31 5 0 67
1998 0 0 0 63 45 14 0 122
1999 0 1 2 21 16 1 0 41
2000 0 0 7 41 43 4 0 95
10-yr avg 0 2 7 38 34 6 0 87

Table 4. Daily wind-run totals and monthly totals, Malheur Experiment Station, Oregon State University, Ontario, OR, 2000.
Daily Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
  ------------------------------------ miles-------------------------------------------
Max. 113 235 138 196 218 157 110 122 182 169 119 114
Min. 16 17 25 38 30 33 29 32 21 11 7 9
Average 43 70 75 81 83 75 68 66 66 49 39 37
Annual total -------------------------------------- miles ----------------------------------------------
2000 1,326 2,032 2,329 2,422 2,565 2,244 2,099 2,051 1,979 1,513 1,158 1,159
9-yr average 1,603 1,752 2,384 2,487 2,315 1,959 1,774 1,665 1,602 1,830 1,644 1,740
52-yr average        2,138 1,912 1,547 1,461 1,311 1,243 1,279    

Table 5. Pan-evaporation totals, Malheur Experiment Station, Oregon State University, Ontario, OR, 2000.
Totals Apr May Jun Jul Aug Sep Oct Total
Daily  -------------------------------------- inches ---------------------------------------
Mean 0.22 0.28 0.35 0.41 0.39 0.23 0.11 1.99
Max. 0.38 0.5 0.53 0.56 0.58 0.4 0.24 3.19
Min. 0.1 0.13 0.09 0.11 0.25 0.1 0.01 0.79
Annual  ---------------------------------------- inches ------------------------------------
2000 6.42 8.68 10.64 12.68 11.95 6.95 3.44 60.76
10-yr avg 6.10 8.78 9.31 11.41 10.40 7.70 4.43 58.13
52-yr avg 5.57 7.62 8.82 11.09 9.56 6.26 3.19 52.11

Table 6. Total Et (acre-inches/acre), Malheur Experiment Station, Oregon State University, Ontario, OR, 1992-2000.
Year Reference Et Alfalfa (peak) Alfalfa (mean) Spring grain Sugar beet Onion Potato - Shepody Potato Field

corn

1992 na 51.8 44.5 28.6 34.8 30.6 32.6 27.6 29.2
1993 44.0 42.5 36.7 22.4 29.5 24.2 22.4 22.9 24.5
1994 49.9 47.4 40.7 23.2 34.5 29.6 22.5 28.0 28.6
1995 44.7 43.4 37.2 23.1 29.0 25.6 24.7 24.1 24.3
1996 47.5 46.4 39.8 23.7 33.0 28.0 25.1 27.1 26.7
1997 49.6 48.3 41.6 25.8 33.4 28.0 24.7 28.3 26.2
1998 48.9 47.4 40.6 24.6 32.5 28.2 25.1 27.1 27.9
1999 53.0 51.3 44.0 25.7 33.8 29.5 26.7 28.0 28.6
2000 54.8 53.2 45.6 25.8 38.3 32.5 27.3 30.4 29.7
8-year avg   48.0 41.2 24.8 33.2 28.5 25.7 27.1 27.3

Table 7. Monthly air temperature, Malheur Experiment Station, Oregon State University, Ontario, OR, 2000.
  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
  Max Min Max Min Max Min Max Min Max Min Max Min Max Min Max Min Max Min Max Min Max Min Max Min
  -------------------------------------------------------°F ---------------------------------------------------------
Max. 54 34 59 40 68 40 83 50 89 57 94 59 101 71 102 65 94 62 85 65 57 37 46 36
Min. 25 8 39 23 45 26 61 31 55 31 67 39 77 47 81 47 64 30 51 30 28 15 29 19
2000 avg 38 26 49 33 55 32 69 41 74 47 83 52 92 59 93 56 77 46 64 40 42 26 36 26
10-yr avg 38 23 45 26 57 32 64 37 73 46 80 51 90 57 90 54 82 47 66 35 48 28 37 21
53-yr avg 35 20 43 25 55 31 64 37 73 45 82 52 91 57 90 55 80 46 66 36 48 28 37 22

Table 8. Monthly 4-inch soil temperature, Malheur Experiment Station, Oregon State University, Ontario, OR, 2000.
  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
  Max Min Max Min Max Min Max Min Max Min Max Min Max Min Max Min Max Min Max Min Max Min Max Min
  ------------------------------------------------------------°F ------------------------------------------------------
Max. 37 35 42 40 49 45 62 53 67 62 74 68 79 72 77 72 69 65 61 59 47 46 37 36
Min. 31 29 33 32 40 38 48 43 54 49 61 57 66 61 70 65 59 54 49 47 34 34 32 31
2000 mean 33 32 38 37 44 41 55 50 61 56 68 62 73 67 73 68 64 60 55 52 40 39 34 34
10-yr mean 34 33 39 35 50 42 60 49 70 58 78 65 85 72 84 73 76 66 60 53 45 41 35 34
33-yr mean 33 32 38 34 50 41 61 48 73 58 82 67 89 74 88 73 77 64 61 51 44 39 34 33

Table 9. Last and first frost ([32°F) dates and number of frost-free days, Malheur Experiment Station, Oregon State University, Ontario, OR, 1990-2000.

Year Date of last frost Date of first frost Total frost-free days
Spring Fall
1990 May 8 Oct 7 152
1991 Apr 30 Oct 4 157
1992 Apr 24 Sep 14 143
1993 Apr 20 Oct 11 174
1994 Apr 15 Oct 6 174
1995 Apr 16 Sep 22 159
1996 May 6 Sep 23 139
1997 May 3 Oct 8 158
1998 Apr 18 Oct 17 182
1999 May 11 Sep 28 140
2000 May 12 Sep 24 135
1976-1999 Avg April 27  October 4 160

Table 10. Record weather events at the Malheur Experiment Station, Oregon State University, Ontario, OR, from 1943 through 2000.
Record event Measurement Date
Greatest annual precipitation 16.87 in 1983
Greatest monthly precipitation 4.55 in May 1998
Greatest 24-hour precipitation 1.52 in Sep 14, 1959
Greatest annual snowfall 40 in 1955
Greatest 24-hour snowfall 10 in Nov 30, 1975
Earliest snowfall 1 in Oct 25, 1970
Highest air temperature 108°F Aug 4, 1961
Total days with maximum air temp. m100°F 17 days 1971
Lowest air temperature -26°F Jan 21 and 22, 1962
Total days with minimum air temp. [0°F 35 days 1985
Lowest 4-in soil temperature 12°F Dec 24, 25, and 26, 1990

Table 11. Annual snowfall totals at the Malheur Experiment Station, Oregon State University, Ontario, OR, 1990-2000.
1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 10-yr avg 57-yr

avg

----------------------------------------------- inches -----------------------------------------------
5.7 7.5 15.5 36.0 32.0 15.0 14.5 5.8 14.6 13.2 13.8 16.0 18.7