Updated Normals Highlight Changing Climate

On August 1st 2011, the NOAA's National Weather Service will begin using the updated Climate Normals in daily operations. These normals, based on the 30 year period of 1981 - 2010, were recently completed and published by the National Climate Data Center in Asheville North Carolina. On balance, the new normals show subtle changes to the climate of the United States with warming in many locations. It is important to note that not all areas have warmed as fast or as much, and individual locations can show cooling.

Locally, the updated normals show a wetter climate as well. In general, spring and summer time precipitation has increased as has winter snow-fall. Below are tables of the changes from the 1971 to 2000 normals to the 1981 to 2010 normals for Fargo, Grand Forks and the University of North Dakota/National Weather Service (UND/NWS) Climate Station. In the tables below positive values denote warmer temperatures and higher amounts of rain or snow, while negative values denote cooler temepratures and less rain or snow.

For example, the 1981 - 2010 mean temperature at Fargo's Hector Field is 1.0 degree Fahrenheit warmer than the 1971 - 2000 mean temperature, while the UND/NWS Climate Station saw a slight decrease. However, at the Grand Forks Airport the mean temperature is virtually unchanged. What are the reasons for the differences in change the past 30 years?

There are several factors that impact the data presented below. Since 1981, there have been several changes in the types of instrumentation used to measure temperature. Automated Surface Observing System (ASOS) stations were implemented in the mid-1990s, largely replacing human observers. As a result, there are inhomogeneities in the 1981-2010 underlying data records due to changes in observing practices. These inhomogeneities are accounted for to the extent possible by quality control and the standardization of monthly temperature values.

Another reason why some stations are cooler is equipment location or impacts of urbanization*. The UND/NWS Climate Station data are a good example. During the 1981 to 1997 time period, the UND Climate Station was located near the center of the UND campus. Between 1981 and 1990, the environment surrounding the temperature measuring equipment changed as new construction encroached on the observation site. By the time the equipment moved from the UND Campus to the NWS, concrete sidewalks and an asphalt parking lot were close to the thermometers. The equipment was moved to the NWS location in the  University Technology Park in April 1997, an area less affected by concrete. As a result, the mean temperature is actually 0.2 degrees Fahrenheit cooler than it's previous location on campus .

 *Urbanization generally refers to the process in which an increasing proportion of a population within a certain area becomes concentrated in cities and the suburbs of cities.

Fargo Changes from old to new normals##                    
  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual
Maximum Temp. 2.5 0.9 1.0 1.3 -0.2 0.0 0.3 0.3 0.9 -0.1 2.1 1.5 1.0
Mean Temp. 2.5 0.5 0.7 0.9 -0.2 0.3 0.4 0.2 1.0 0.1 1.7 1.5 1.0
Minimum Temp. 2.4 0.3 0.5 0.5 -0.2 0.5 0.4 0.1 1.1 0.5 1.3 1.4 0.8
CDD 0 0 0 0 -6 1 4 -3 4 1 0 0 1
HDD -59 -34 -21 -20 12 0 0 0 -19 3 -45 -42 -226
Precipitation -0.11 0.02 0.13 -0.04 0.20 0.39 -0.09 0.04 0.39 0.18 -0.09 0.24 1.27
Snowfall -1.4 -0.2 0.4 0.3 0.0 0.0 0.0 0.0 0.0 0.1 -0.5 2.8 1.4
                           
Grand Forks Airport Changes from old to new normals##                  
  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual
Maximum Temp. 2.0 -0.1 0.4 0.9 -1.3 -0.7 -0.1 0.0 0.6 -0.6 1.4 1.0 0.4
Mean Temp. 1.6 -0.8 -0.3 0.0 -1.6 -0.8 -0.3 -0.3 0.3 -0.8 0.6 0.9 0.0
Minimum Temp. 1.3 -1.5 -1.0 -1.0 -2.0 -0.8 -0.5 -0.5 -0.1 -1.0 -0.4 0.6 -0.4
CDD 0 0 0 -1 -14 -12 -14 -12 -2 0 0 0 -43
HDD 326 263 551 405 245 77 -22 -217 -378 -498 -513 -180 8
Precipitation -0.13 -0.07 0.07 -0.22 0.47 0.45 0.09 0.16 0.09 0.30 -0.05 0.05 1.58
Snowfall 0.0 0.1 0.4 0.0 0.1 0.0 0.0 0.0 0.0 0.4 -0.5 2.5 2.6

 Supplemental data from the UND/NWS Climate Station.

UND/NWS Changes from old to new normals##                    
  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual
Maximum Temp. 1.1 -0.4 -0.5 -0.3 -2.8 -0.8 -0.7 -0.8 -0.4 -1.9 0.5 0.3 -0.5
Mean Temp. 1.3 -0.3 -0.6 -0.4 -2.2 -0.4 -0.2 -0.5 -0.1 -1.2 0.3 0.5 -0.2
Minimum Temp. 1.4 -0.3 -0.7 -0.4 -1.6 -0.2 0.3 -0.1 0.2 -0.7 0.2 0.7 0.2
CDD 0 0 0 0 -18 -12 -12 -18 -4 0 0 0 -74
HDD -4 -4 27 19 63 17 4 4 5 47 -3 63 165
Precipitation -0.07 -0.04 0.09 -0.14 0.71 0.47 0.32 0.19 0.1 0.41 -0.03 0.07 2.12
Snowfall 0.4 0.8 0.4 -0.2 0.1 0 0 0 0 0.2 0.3 2.5 6.1

 

## The change in annual averages may not algebraically match the change in monthly averages due to the rounding techniques used.

In general, the climate has warmed over much of the region in the past 30 years, and is certainly wetter. The above information shows that variations occur within the grand scheme due to a variety of changes. Please refer to the information provided by the National Climate Data Center for details. You may also contact Mark Ewens, Climate Services Focal Point at the Grand Forks NWS.

 




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