The ESRL website will be unavailable for 24 hours starting Friday, March 6th at 5:00pm MT due to building maintenance.
Glossary of Terms
- Definition of "Climatology"
- What is shown in all the plots is what the weather was from 1961-1990. It is NOT technically a climatology. The difference is that a climatology attempts to take into account the variability of the data due to small sample sizes and smoothed accordingly. The plots I have show the variability of the data through the years. If I had enough years AND the "climate" didn't change, then I would get a smooth climatology. I chose to show the nonsmoothed data to display the yearly variations in "climate".
- Maximum daily temperature
- The highest temperature reached at any point during a 24 hour period defined as midnight to midnight local standard time rounded to the nearest whole degree.
- Minimum daily temperature
- The lowest temperature reached at any point during a 24 hour period defined as midnight to midnight local standard time rounded to the nearest whole degree.
- The total of daily rainfall and melted frozen precipitation in hundredth-s of inches during a 24 hour period defined as midnight to midnight local standard time.
- The total depth of daily snowfall in tenths of inches during a 24 hour period defined as midnight to midnight local standard time. Hail is included from 1989-1990.
- Chance of precipitation
- This is the chance that there is measurable (greater or equal to .1 inches) precipitation on a particular day. All possible years are used. It differs from the total precipitation plot. The smoothed line is the same plot that is smoothed by fitting the first 6 harmonics to the data. Since the chance of rain is highly variable for 30 years, especially in regions of low rainfall, it is probably better to look at.
- Difference between a value and the average value. For the January 1989 monthly mean temperature anomaly, that would be the difference between the January 1989 temperature and the average January temperature for all years from 1961-1990.
- Daily wind speed
- The daily average wind speed is calculated for all years available. In many cases, this information is not recorded. For stations where it is, it is only available from 1984 onwards. For these plots, only 1984-1990 was used so there is just 7 years of data. The smoothed line is the same plot that is smoothed by fitting the first 6 harmonics to the data.
- Percentage of possible sunshine
- The percentage of sun is the daily amount of sunshine divided by the total available at the site. So, for a winter day with 8 hours of sunshine available that had 6 hours of sunshine, the percentage would be 75%. For a summer day with 8 hours of sunshine out of 16 possible, the percentage would be 50.T his number is averaged for all years available which is either none or the years 1984-1990.
- Rankings were calculated by sorting all the monthly values for years where data was available and listing the data and the years in decreasing order of magnitude. Ties are not handled. For the ranked data, the data was included through June 1996, where available. For precipitation, data starts in 1948 and goes through June 1996.
Comments on Web Page Design
- Data description:
- Data were obtained from the National Climate Data Center (NCDC) first order stations. Only the data from 1961-1990 were used. This was done so that the different plots could be compared correctly. Most stations have complete data but some do not (including almost all military bases which have only 10 years). There were some quality control checks done on the data including checks for range and standard deviations. Some incorrect data still might have gotten through, though. Averages were done for the 1961-1990 time period and only stations with at least 10 out of the 30 years possible were included.
- The shaded state relief maps used were provided by Ray Sterner and are used with his permission (they are copyrighted!). City names were positioned on the maps using IDL except in cases where they were hand drawn. Pixel coordinates of the city names were done by hand using xv. Supporting CGI processes are written in PERL. E-mail me for more details.
- The simple state maps maps were created using IDL. The maps used a cylindrical projection and high resolution state/river boundaries. City names were positioned on the maps using IDL.. Pixel coordinates of the city names were determined with IDL as well. Supporting code to process the inputs was done in PERL.
- Basic climate plots were created using GrADS and were generally stored as prepared GIFS. Some files are created on-the-fly using the grads software (in batch mode) and a virtual window buffer.
- Ranking tables
- Ranked values were computed on-the-fly and printed out using tables for browsers that can handle tables. Code used for computing the rankings was fortran and included sorting code from numerical recipes.
- Ranking Histograms
- The method currently used for the histograms consisted of assuming 8 bins and dividing the data to fit those bins. For temperatures, bins were determined by obtaining the mean and
standard deviation of the data. Bin 1 was less than or equal to the mean -(4*std) . Bin 2
was less then or equal to mean-(3*std) and greater than bin 1 and so forth. Bins edges were rounded to the nearest decimal place.
For precipitation and snowfall, because negative precip is impossible, bins were chosen
so that the first bin was not less than 0. For data where the mean-(4*std) was greater than
0, then the bins were chosen as for temperature. For bins where that was not true,
bins were determined by calculating the range of the data and then dividing the data into
Histograms were plotted in grads by using the bin edges as time (8 "time" points) and the different stations as levels. Plots were created 'on-the-fly' with a grads script. GIFS were created by using a virtual window buffer which was written into and then converted to GrADS.