30 Jan

Map of the Week: Where Dreary Weather Occurs in the U.S.

Most citizens in the United States have experienced dreary weather at least once in their lives. Whether that person lives in the hot and dry climate of the Southwest, or the cold and wet climate of the Northeast, instances of dreary weather are nearly inescapable in any ecosystem. Although inescapable, some regions of the country experience dreary weather patterns more frequently than others. For example, the arid climate of the  Southwest U.S. typically experiences less rainy days or cloud covered days than the Pacific Northwest or the Northeast.

This map shows dreary day frequency in the United States

To understand this map, one must first know how dreary weather is defined. While there is no clear definition of a “dreary day”, this map from the US Climate Blog, incorporates data such as total rainfall (in), number of wet days, and cloud covered days in a year to determine the overall “dreariness” of an area. It is evident that the degree of dreary weather experienced is highly dependent on where you live geographically.

Appropriate variables were meticulously selected to ensure that an accurate map would be curated. These variables were used to determine which areas are shaded and what color they are. Detailed explanations for the variables are as follows:

Variable 1: Total annual precipitation. This was generated directly from the National Climate Data Center’s (NCDC) published normal values for the 1981-2010 climate normal period. A total of 8,526 stations were used in this analysis.

Variable 2: Days per year with measurable precipitation. This was calculated from Global Climate Historical Network (GHCN) daily climate data. All days between 1981 and 2010 for the 1,751 “first order” stations in the U.S. were evaluated on whether or not measurable precipitation was observed. Stations with 15 or more complete years of data were utilized. A total of 952 stations met this criteria.

Variable 3: Annual cloud coverage. This data were obtained by analyzing 31 years of GHCN daily climate data (1966-1996) that contain entries for daily cloud coverage. A much smaller number of stations had a sufficiently robust (10 or more years) level of data coverage to use in the analysis. A total of 221 stations met the minimum data criteria. Because of the small number of stations, the gridded data are more generalized than for either Variable 1 or Variable 2.

Only a few places on the map received a maximum index score (indicated in red) in the final product. Areas such as the Pacific Northwest and a small portion of the North East can be seen shaded this color in some areas.

While it’s unsurprising the dreariest areas exist in the Northwest and Northeast, the size of the area characterized by dreary weather is surprising.  The region spans from Western Virginia all the way up to Maine and experiences some of the most dreary weather in the country. Another unsurprising take away from the data displayed in this map is the lack of dreariness in the Southwestern United States. According to the blog post: “Several areas in Arizona, Nevada, and California had a score of 3 – the lowest value possible. Both Las Vegas and Phoenix achieved this “perfect” score.” (USCB)

The average dreariness score for the U.S., according to the US climate blogspot is 16.5. Buffalo and Seattle tied with a score of 27 as the most dreary cities in the US. Immediately behind them are Pittsburgh and Portland. New York scores a 24 for dreariness, and Newark, New Jersey does as well.

This map reflects the combined characteristics of a dreary day and aggregates these statistics to create one easy to read diagram. The methodology used to create this map reflects data that would characterize a place as being “wet and gray.” Although the map is not perfect, this visualization is a good tool for showing people where dreary weather is most common in the U.S. It can also help them choose where to live depending on what kind of weather they prefer.

Source: Brian B’s Climate Blog

Written by: Sean Halpin