Image Metadata File

Person Submitting Metadata/Point of Contact:

Name: Laura Stevens
Physical Address: 151 Patton Ave Asheville, NC 28801
Organization: CICSNC
Email:
Phone:

Image Info:

Image Title:
Time series of freeze-free season anomalies
Image Description:
Time series of freeze-free season anomalies shown as the number of days per year, for the contiguous U.S. (top, green), eastern U.S. (bottom, blue) and western U.S. (bottom, red). Length of the freeze-free season is defined as the period between the last occurrence of 32°F in the spring and first occurrence of 32°F in the fall. The dashed line is a linear fit. Based on daily COOP data from long-term stations in the National Climatic Data Center’s Global Historical Climate Network data set. Only stations with less than 10% missing daily temperature data for the period 1895-2011 are used in this analysis. Freeze events are first identified for each individual station. Then, event dates for each year are averaged for 1x1° grid boxes. Finally, a regional average is determined by averaging the values for the individual grid boxes. There is an overall statistically significant upward trend for the contiguous U.S., as well as for both the eastern and western U.S.
Attributes (variables name, description and units):
Freeze-free season anomaly (days / year)
Temporal domain:
Start Time: 1895-01-01 00:00:00.0
End Time: 2011-12-31 00:00:00.0
Spatial domain:
Max latitude: 49.3125
Min latitude: 25.1875
Max longitude: -67.0625
Min longitude: -124.688
Keywords:
Contiguous U.S., Observed, USGHCN Daily, Temperature
Usage Limitations/Constraints:
Citation of image source:

Panels within image: 2

Top:
Image Description:
Coterminous U.S.
Bottom:
Image Description:
Western U.S. (red) and eastern U.S. (blue) (bottom).

Image Creation:

Who created the image:
Name: Laura Stevens
Physical Address: 151 Patton Ave Asheville, NC 28801
Organization: CICSNC
Email:
Phone:
When was image created (YYYY-MM-DD): 2012-09-05 00:00:00.0

Data Sources:

Dataset #1
Dataset Name: USGHCN Daily
Dataset Version:
Dataset Description: Global Historical Climatology Network - Daily
Dataset ID:
Dataset Release/Publication Date:
Affiliated Organization Name and Role: NOAA NCDC/Russ Vose
Date Accessed: 2011-06-06 00:00:00.0
Dataset Location (ftp, URL, etc): ftp://ftp.ncdc.noaa.gov/pub/data/ghcn/daily/
Data qualifier (QA/QC, etc):
The denominator of the scale of the source/output:
Spatial Reference system used by the source/output:
Citation to metadata:
Description of the scope of a resource, quality report, or process:
Spatial Extent of the source/output (polygon, box or region name): National
Temporal extent of the source/output: 1895-01-01 to 2011-12-31
Vertical extent of the source/output:
Identifier of the processing level of the source/input:
Spatial resolution of the source/output: 1 km

Processes:

Process #1
Input(s):
Step(s):
  • The data set is GHCN-Daily. Stations were selected by examining each station in the entire data base. Only stations with less than 10% missing daily minimum temperature data for the period 1895-2011 are used in this analysis. Days when the temperature data had a quality flag were considered missing. Freeze events are first identified for each individual station. This was done as follows. August 1 was considered the ?middle? of the year. Then, the first occurrence of a minimum temperature of less than or equal to 32 deg F after August 1 was considered the first fall freeze. The first occurrence of a minimum temperature of less than or equal to 32 deg F going backward in time from August 1 was considered the last spring freeze. For warmer climates where freezes are rare, allowance was made for situations when there is no freeze early in the year after Jan. 1 or late in the fall before Dec. 31. Specifically, the first ?fall? frost was allowed to happen as late as March 28 of the following year. Conversely, the last spring frost was allowed to happen as early as Dec. 4 of the previous year. If the first fall frost failed to occur prior to March 28 of the following year, it was set to missing. Likewise, if the last spring frost failed to occur after Dec. 4 of the previous year, it was set to missing. Missing days were taken into account in the following way. If more than 18 days of missing accumulated between August 1 and the first fall frost, the first fall frost for that year was set to missing. Likewise, if more than 18 days of missing accumulated between August 1 and the last spring frost going backward in time from August 1, the last spring frost for that year was set to missing. The freeze-free season length was set to missing if either the last spring frost or the first fall frost were set to missing. Then, average freeze-free lengths for each year are averaged for 1x1° grid boxes. Finally, a regional average is determined by averaging the values for the individual grid boxes.
Output(s):
Software:
Environment(s):
Additional Comments:

References: