Retrieve and Display CRN Insolation Data

This application provides access to insolation data from NOAA's Climate Reference Network (CRN). All the CRN data are available online, but the online files do not include calculated standard deviations for the hourly-averaged insolation data. We thank the staff at NOAA's Satellite and Information Service, National Environmental Satellite, Data, and Information Service (NESDIS) for providing insolation data files including the standard deviations.

The data are in comma-delimited ASCII text format, with one file for each CRN site that reports pyranometer data:

	Avondale, PA 03761 360320 85 m zone 5 6 2 2006 16
	Station,Latitude,Longitude,SOLARAD,SR_STD,SOLRAD_MX,SOLRAD_MN 
  	PA Avondale 2 N,39.8593,-75.7861,06/02/06 16:00 UTC,475.5,156.4,908,271.4,	
    ...

This format is not the same as the online CRN data, which contains all parameters from each site, but without the calculated standard deviations for the insolation.
The insolation values are in units of W/m². Missing data are indicated by negative values, but these negative values are not consistent for all the files. Missing data values include -99, -999, and -9999, but there are occasionally other negative values, too. Very rarely there may be very small negative values, much less in absoluate value than 1; the source of these values is unknown, but may reflect some glitches in the data logger conversion from volts to W/m². The lack of consistency in how missing values are indicated is not a serious problem, as any negative value of insolation can be counted as missing except perhaps for the occasions where very small values are given. A test such as "if (insolation < -1)..." will work to search for missing values, and it will not flag the occasional very small negative values which make no physical sense but are not actually missing (and can perhaps be assumed to be the same as 0).
The "standard deviation" value deserves additional explanation. This value is calculated by the CRN data logger software in the usual way for measurements within each hour. But, a standard deviation calculation is always premised on the assumption that it is applied to a set of values normally distributed about a mean. This is certainly not the case for the insolation values during an hour. Hence, this value is more accurately interpreted as a measure of the range of measurements during an hour. As a result, the standard deviation (for a clear sky) is always greatest during the mid-morning or mid-afternoon when insolation is changing most quickly. It is close to 0 around noon, but is never actually 0.
Display options in this application include:

Preview first and last records for selected site.

Header lines with first and last data lines for this site
Avondale, PA 03761 360320 85 m zone 5 6 2 2006 16
Station,Latitude,Longitude,SOLARAD,SR_STD,SOLRAD_MX,SOLRAD_MN
PA Avondale 2 N,39.8593,-75.7861,06/02/06 16:00 UTC,475.5,156.4,908,271.4,
...
PA Avondale 2 N,39.8593,-75.7861,05/10/11 01:00 UTC,0,0.2,2,0,

This option provides a quick look at the range of data available for a specified site.

Display all hours with missing data for selected site.

List of missing hours for this site.
Avondale, PA 03761 360320 85 m zone 5 6 2 2006 16
Latitude, Longitude, Date, Time, S_avg, S_std, S_max, S_min
39.8593 -75.7861 02 17 07 08 00 UTC -99 -99 -99 -99
39.8593 -75.7861 02 17 07 09 00 UTC -99 -99 -99 -99
39.8593 -75.7861 02 17 07 10 00 UTC -99 -99 -99 -99
39.8593 -75.7861 02 17 07 11 00 UTC -99 -99 -99 -99
39.8593 -75.7861 02 17 07 12 00 UTC -99 -99 -99 -99
39.8593 -75.7861 02 17 07 13 00 UTC -99 -99 -99 -99
39.8593 -75.7861 12 05 07 09 00 UTC -99 -99 -99 -99
39.8593 -75.7861 12 14 07 04 00 UTC -99 -99 -99 -99
39.8593 -75.7861 12 14 07 05 00 UTC -99 -99 -99 -99
39.8593 -75.7861 12 14 07 06 00 UTC -99 -99 -99 -99
39.8593 -75.7861 12 14 07 07 00 UTC -99 -99 -99 -99
39.8593 -75.7861 12 14 07 08 00 UTC -99 -99 -99 -99
39.8593 -75.7861 12 14 07 09 00 UTC -99 -99 -99 -99
39.8593 -75.7861 12 14 07 10 00 UTC -99 -99 -99 -99
39.8593 -75.7861 12 14 07 11 00 UTC -99 -99 -99 -99
39.8593 -75.7861 12 14 07 12 00 UTC -99 -99 -99 -99
39.8593 -75.7861 11 09 08 15 00 UTC -99 -99 -99 -99
39.8593 -75.7861 11 09 08 17 00 UTC -99 -99 -99 -99
39.8593 -75.7861 09 29 09 16 00 UTC -99 -99 -99 -99
39.8593 -75.7861 10 24 10 15 00 UTC -99 -99 -99 -99
39.8593 -75.7861 10 24 10 18 00 UTC -99 -99 -99 -99
39.8593 -75.7861 10 27 10 14 00 UTC -99 -99 -99 -99
39.8593 -75.7861 10 27 10 15 00 UTC -99 -99 -99 -99

There are almost always some missing data at any of these CRN sites and this option provides a complete list of missing hours for the selected site, using this test: if (average insolation < -1) then the data are missing. Note that in some cases, dating back to the earlier years of reporting these data and for reasons unknown, the average insolation and standard deviation will be present, but not the maximum and minimum insolation.

Retrieve all data for the specified year and location, in text format.

Avondale, PA 03761 360320 85 m zone 5 6 2 2006 16
Station,Latitude,Longitude,SOLARAD,SR_STD,SOLRAD_MX,SOLRAD_MN
PA Avondale 2 N,39.8593,-75.7861,06/02/06 16:00 UTC,475.5,156.4,908,271.4,
PA Avondale 2 N,39.8593,-75.7861,06/02/06 17:00 UTC,375.7,27.7,425.1,335.3,
PA Avondale 2 N,39.8593,-75.7861,06/02/06 18:00 UTC,490.2,140.3,898,310.5,
PA Avondale 2 N,39.8593,-75.7861,06/02/06 19:00 UTC,44.5,24.7,91,8.1,
PA Avondale 2 N,39.8593,-75.7861,06/02/06 20:00 UTC,51.1,43.8,189.6,0,
PA Avondale 2 N,39.8593,-75.7861,06/02/06 21:00 UTC,514.5,205.2,903,164.8,
PA Avondale 2 N,39.8593,-75.7861,06/02/06 22:00 UTC,190.3,59.2,426.5,41.9,
PA Avondale 2 N,39.8593,-75.7861,06/02/06 23:00 UTC,18.1,15.3,43.7,0,
PA Avondale 2 N,39.8593,-75.7861,06/03/06 00:00 UTC,0,0,0,0,
...

This option simply echoes every line in the file for a selected site and year.

Generate table of kWh/m2/day for the selected year and location, including calculated clear-sky values. (This option will take a while!)
```
file position: PA Avondale 2 N,39.8593,-75.7861,01/01/10 05:00 UTC,0,0,0,0,
site elevation 85
Date kWhr/day MJ/day Clear sky kWhr/day Clear sky MJ/day
5 2455197.75, 1, 1, 2010, 1.57, 5.64, 2.45, 8.83
5 2455198.75, 1, 2, 2010, 2.31, 8.32, 2.47, 8.88
5 2455199.75, 1, 3, 2010, 1.56, 5.60, 2.48, 8.93
5 2455200.75, 1, 4, 2010, 1.29, 4.65, 2.49, 8.98
5 2455201.75, 1, 5, 2010, 1.55, 5.56, 2.51, 9.04
5 2455202.75, 1, 6, 2010, 1.11, 4.00, 2.53, 9.10
5 2455203.75, 1, 7, 2010, 2.60, 9.35, 2.55, 9.17
...
```
This option sums observed insolation over each day and also calculates clear-sky insolation integrated for every day for the specified year and site. The "day" is always a local time day, not a UT day. Various options have been used to account for days with missing hours, depending on how many hours are missing.
The modeled clear-sky values are calculated by summing one-minute modeled values over each hour. This is a calculation-intensive option that may take several tens of seconds to complete.
Generate bar chart of kWh/m2/day for the selected year, month, and location.

Generate line graphs of insolation for selected year, specified days, and location.

This option displays the CRN data along with clear-sky insolation for the specified site, year, and range of dates, for 1, 2, 4, or 8 days. The starting date can be any date in the month. If the starting date is near the end of the month, the day labels will start with day 1 on the next month.