This question was submitted on behalf of a User
I am attempting to compile heating degree day data for cities in North America. I recognize that the NASA ASDC is a reliable source for this information. I am using the following NASA ASDC web address to retrieve HDD information: https://email@example.com. I input the latitude-longitude information (e.g. Albany = 42.65 N, 73.75 W) and click "Submit". On the following page I select "Heating Degree Days below 18 C" in the "Meteorology (Temperature)" section and clicked "Submit". The results are an annual HDD value of 4,351 for an elevation of 1,744 m. Since the elevation of Albany is 95 m, this information is not useful. I repeat the process, but this time after selecting "Heating Degree Days below 18 C". I also input the elevation of 95 m in the section below "Meteorology (Temperature)". The result is the same: an annual HDD value of 4,351 for an elevation of 1,744 m. Am I missing something, or does the elevation-correction on the webpage not work properly? Is there a way to obtain HDD values for specific latitudes, longitudes, and elevations using NASA ASDC resources?
This response was provided by the POWER data provider: James Hoell....
It appears that the user has input the longitude as a “+” value rather than as a “-“ values. West longitudes are considered as negative values. Inputting latitude = + 42.65 and longitude = -73.75 yields the annual HDD = 3790 and the elevation 273m. Note that the spatial resolution of the values is 1-degree latitude by 1-degree longitude. The HDD and the elevations values represent averages over the 1-deg by 1-deg grid.
HDD and CDD values with a spatial resolution of 0.5-degree by 0.5-degree can be obtained at https://power.larc.nasa.gov/cgi-bin/halfdeginterann.cgi. Using this site the annual HDD = 4002 over the years 1981 – 2014 and the average elevation is 300 meters.