Wetland Symposium
Climate of the Cottonwood Lake Area, Stutsman County, North Dakota
DONALD O. ROSENBERRY
U.S. Geological Survey, Water Resources Division, Mailstop 413, Building 53, Lakewood, CO 80225
The climate of central North Dakota, which includes the Cottonwood Lake area, is continental, typically with large annual and daily temperature changes, light to moderate precipitation, low relative humidity, and moderate to high numbers of clear and partly cloudy days. Average annual temperature is 4oC and average annual precipitation is 440 mm. The region receives an average of 59% of possible sunshine. Windspeed averages 16 km/hr from the northwest. Relative humidity is typically high at night and reaches an average daily nadir of 63%.
Day length ranges from less than nine hours in December to over 16 hours in June. This large range in day length contributes to large seasonal temperature changes; extreme temperatures range from -47 to 48oC. Winter is typically cold and dry; normally 56 days each year have temperatures below -18oC and 195 days have temperatures below 0oC. November through February are the driest months, with average precipitation from 12 to 13 mm/month. Average annual snowfall is 865 mm, average maximum snow depth is 300 mm, and on average there are 105 days with a snow depth of 25 mm or more. Snow normally covers the site from 4 December to 24 March. Summer is warm with the maximum monthly mean temperature of 20.5oC occurring in July. In average, on a normal year, 17 days have temperatures that exceed 32oC. June is normally the wettest month of the year, averaging 91 mm of rainfall. Thunderstorms produce most of the rainfall during summer months.
Climatic characteristics have been monitored at wetland P1 at the Cottonwood Lake area during the open-water seasons from 1978 to the present. Collection of onsite climatic data allows accurate estimation of evaporation and precipitation, which provides information for determination of hydrologic budgets of wetlands in the Cottonwood Lake study area. Climatic variables that have been monitored, some for part of the period and some for the entire period, include air temperature, wetland surface-water temperature, wetland bottom-sediment temperature, humidity, wind speed, incident short-wave solar radiation, incident long-wave atmospheric radiation, and precipitation. These data were recorded by a digital data logger and exist as hourly and daily averages or totals of scans made at one-minute intervals.
On-site data collection also provides information about changes in the climate relative to conditions normal for the region. Conditions have been drier than normal during the late 1980's and early 1990's at the Cottonwood Lake area study site.
Precipitation has been above average during only three of the 14 years from 1978 to 1991, and about average conditions occurred during another two years of the period. During the rest of the years precipitation has been below normal, resulting in a cumulative departure from average precipitation of -540 mm. During 114 of 168 months precipitation at the study site has been below normal.
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