| Stations: | Bondville |
| Parameters: | Erythemal UVB |
| Dates affected: | 16-Oct-2018 through 13-May-2019 |
| Date posted: | 17 June 2019 |
Description of problem:
After the instrument exchange on 16 Oct 2018 at Bondville, the calibration constant applied to data from the newly mounted UVB radiometer was wrong. The result was that the erythemal UVB irradiance for Bondville from 16-Oct 2018 to 13-May-2019 was artificially too high by about 10%. As of 17 June 2019 all data files and related products for the Bondville SURFRAD station from 16-Oct 2018 to 13-May-2019 have been regenerated using the proper UVB calibration constant.
| Stations: | Desert Rock |
| Parameters: | Direct normal solar |
| Dates affected: | 20-July-2016 to 24-September-2017 |
| Date posted: | 26 September 2017 |
Description of problem:
After the instrument exchange on 19 Apr. 2017 at Desert Rock, the calibration constant for the newly mounted CHP1 pyrheliometer that was entered in the processing software was wrong. The result was that the direct-normal irradiance during that period was artificially low. That error also affected the “best-estimate” total solar published in the QcRad3 and RadFlux files for Desert Rock for that period. As of 26 Sept. 2017, all data files and related products from 19 Apr. to 24 Sept 2017 for Desert Rock have been regenerated using the proper calibration constant for the pyrheliometer data.
| Stations: | Penn State |
| Parameters: | Station Pressure |
| Dates affected: | 13-July-2016 to 19-September-2017 |
| Date posted: | 20 September 2017 |
Description of problem:
The atmospheric station pressure measurement at the Penn State SURRAD site was off by ~ -10 mb during the affected period (13-sep-2016 to 19-Sep-2017). When the Penn State data logger was reprogrammed during the annual instrument exchange on 13 July 2016, the wrong equation to convert the barometer’s raw signal to atmospheric station pressure was resident in the program used. We were able to reverse that mistake and accurately compute the correct pressure. On 19-20 Sept. 2017. All affected data files and products were regenerated with the corrected station pressure.
| Stations: | Fort Peck |
| Parameters: | Global Shortwave |
| Dates affected: | 25-September-2014 to 22-September-2015 |
| Date posted: | 21 December 2016 |
Description of problem:
The global pyranometer installed at the Fort Peck SURFRAD station on 25 Sept. 2014 (Spectrosun, SN 73-32) and removed on 22 Sept. 2015, may have had a bad calibration. Historically, the responsivity of that pyranometer is stable at around 8.3, with variability in the hundreths place. The responsivity given to me in 2013, which is the value I used during the period in question, was 8.516. That value, if wrong, would underestimate the global horizontal irradiance, and that is what we have seen when comparing the global measurement to the [direct x cos (SZA)]+ diffuse. Regardless, because of cosine and offset errors inherent in stand-alone single black detector pyranometer measurements, the global solar measurement is considered secondary to [direct x cos(SZA)] + diffuse. The latter should always be used for total solar if both direct and diffuse measurements are available.
| Stations: | Desert Rock |
| Parameters: | Upwelling infrared |
| Dates affected: | 22-August-2010 to 13-September-2010 |
| Date posted: | 6 July 2016 |
Description of problem:
From 22 August 2010 through 13 Sept. 2010, the upwelling infrared measurement at the Desert Rock SURFRAD site was intermittently (and mostly) bad due to corrosion on contacts at the 10-m tower. The erroneous upwelling IR values that were produced were so small that they did not reach the lower limit of the QC plot and therefore did not show up. Consequently, the SURFRAD QC analyst assumed that those data were marked as missing in the data files that were distributed. However, the bad values remained in the archived data files. On 6 July 2016, the all of the erroneous upwelling IR data from Desert Rock for that ~3 week period during late summer of 2010 were marked as missing and good data files were produced. SURFRAD data users should replace their Desert Rock data files for the affected period in 2010 with the new reprocessed files that were placed in the SURFRAD FTP archive on 6 July 2016.
| Station(s): | Table Mountain |
| Parameter(s): | Upwelling solar |
| Date(s): | 22-August-2014 to 4-September-2015 |
| Date Posted: | 17 September 2015 |
Description of Change:
From 22 August 2014 through 4 Sept. 2015, the albedo at Table Mt. was consistently low by 1-2% compared to other years. The calibration of the pyranometer that was used during that period was checked and its responsivity value was found to be too great by 0.0164. On 16 Sept. 2015, the Table Mountain calibration file was adjusted and the upwelling solar recomputed over the affected period. The new data files were written to the FTP site on 16 Sept. 2015.
| Station(s): | Goodwin Creek |
| Parameter(s): | Wind direction |
| Date(s): | 19-Nov-2014 to 11-May-2015 |
| Date Posted: | 27 May 2015 |
Description of Change:
On 19 November 2014 the wind monitor was replaced at the Goodwin Creek SURFRAD site. When the replacement wind monitor was mounted, it was rotated 128 degrees clockwise from its proper alignment. Consequently, the wind direction reported in the SURFRAD processed data files was off by +128 deg. from 19 November 2014 through 11 May 2015. On 27 May 2015 all of the wind data during that ~6-month period was corrected and new daily data files with the proper wind direction were generated.
| Station(s): | Bondville |
| Parameter(s): | PAR |
| Date(s): | 13-Jun-2014 to 13-Aug-2014 |
| Date Posted: | 27 August 2014 |
Description of Change:
The quantum sensor that measures photosynthetically active radiation (PAR) at the Bondville SURFRAD station had a calibration assigned that produces a step change in the PAR time series after its deployment on 12 Jun-2014. That sensor was replaced on 14 Aug. 2014 after which the PAR measurements increased to more normal values. On 27 Aug. 2014, a modified calibration value was computed for the sensor that was removed and all PAR measurements over the affected period (13-Jun to 13-Aug. 2014) were reprocessed using the new calibration value.
| Station(s): | Penn State |
| Parameter(s): | PAR |
| Date(s): | 22-Sep-2013 to 14-Nov-2013 |
| Date Posted: | 21 November 2013 |
Description of Change:
The quantum sensor that measures photosynthetically active radiation (PAR) at the Penn State SURFRAD station lost approximately 4% sensitivity on 22 Sept. 2013. That sensor was replaced on 14 Nov. 2013 after which the PAR measurements increased to more normal values. On 21 Nov. 2013, the QC values of the Penn State SURFRAD PAR measurements over the affected period (22-Sept to 14-Nov. 2013) were set to bad (1), however, the PAR values were kept in the data files, i.e., not set to missing.
| Station(s): | Table Mtn. |
| Parameter(s): | Time |
| Date(s): | 23-Oct-2012 to 5-May-2013 |
| Date Posted: | 30 August 2013 |
Description of Change:
The clock on the Table Mountain SURFRAD station data logger drifted by nearly four minutes between 23 –Oct-2012 and 5-May-2013. On 5 May, the clock on the TBL data logger was found to ne nearly 4 minutes fast. The data logger problem was corrected and a linear correction has been applied to the time in all Table Mountain raw data files for the affected period. The affected Table Mountain data was subsequently reprocessed. Because of the small nature of the drift over such a long period, the one-minute data began to be adjusted in late December 2012 (day 356). The time-corrected SURFRAD data files for the affected period were loaded to the SURFRAD FTP site on 15-Aug-2013.
| Station(s): | Penn State |
| Parameter(s): | Station Pressure |
| Date(s): | 11-April-2003 to 18-June-2012 |
| Date Posted: | 10 May 2013 |
Description of Change:
We recently discovered that the barometer at the Penn State station drifted linearly downward by about 4 mb from 11-April-2003 to 18-June-2012--that is about 0.4 mb/year,. Because this change was so subtle, we did not catch the problem until we had enough data to analyze deviations from the long-term mean. A correction was devised and applied to all Penn State station pressure data during the affected 10-year period. All Penn State SURFRAD daily files have been reprocessed and are now available at the SURFRAD FTP site, with corrected station pressure.
| Station(s): | All Stations |
| Parameter(s): | Global downwelling solar and upwelling solar |
| Date(s): | Listed separately for each station below |
| Date Posted: | 12 July, 2010 |
Description of Change:
During the spring of 2010, the managers of SURFRAD were informed that they were given slightly off calibration values for all pyranometers that were calibrated in 2006. Calibrations supplied at that time were between 1.5% and 2.0% higher than they should have been. All sites were adversely affected but for differing periods. Only the global solar and upwelling solar parameters were reprocessed using amended calibration values. Direct and diffuse solar measurements were not affected. Data reprocessing took place on 8,9-July 2010 using amended calibration values. The reprocessed periods for each site are listed below:
Bondville: 5-June-2007 to 11-June-2008
Fort Peck: 4-Oct-2007 to 17-Sept-2008
Goodwin Creek: 11-May-2007 to 29-April-2008
Table Mountain: 28-July-2007 to 19-Aug.-2008
Desert Rock: 11-April-2007 to 25-March-2008
Penn State: 28-June-2007 to 29-July 2008
Sioux Falls: 22-Aug.-2007 to 9-Oct.-2008
| Station(s): | Bondville |
| Parameter(s): | Direct solar |
| Date(s): | 21 May, 2003 through 7 June, 2004 |
| Date Posted: | 23 Nov, 2009 |
Description of Change:
Description of change: An inaccurate 2002 factory calibration (responsivity) value for the Bondville pyrheliometer of 7.86 was originally used for 21 May 2003 through 7 June 2004. The post deployment calibration of that pyrheliometer was performed by NREL in August 2004, 3 months after the instrument was removed from Bondville. That BORCAL procedure produced a responsivity of 7.97. As a NIP sensor ages, the responsivity usually decreases. Therefore increase from the factory value (7.86) in 2002 to the NREL value of 7.97 in 2004 does not make sense. The factory informed SURFRAD managers that the 7.86 calibration assigned to the pyrheliometer was probably too low, and should be closer to 7.91, which is consistent with all subsequent calibrations of that instrument by NREL (2004: 7.97), Factory (2005: 7.93), and Dept of Commerce (2008: 7.97). Therefore the direct solar data at Bondville from 22 May 2003 through 8 June 2004 has been reprocessed using the post-deployment NREL responsivity value of 7.97.
| Station(s): | Bondville |
| Parameter(s): | Direct and diffuse solar |
| Date(s): | 1 April through 21 July, 1999 |
| Date Posted: | 23 Nov, 2009 |
Description of Change:
There were tracker related problems from March through May 1997 for Fort Peck. Bad direct and diffuse solar data from 1600-2300 UTC in March, April, and 5-19 May 1997 had been removed in the original daily editing. However for 3 May and 20-31 May the tracker was slightly off and those data were not edited out in the original daily processing. Those data have been removed in the present archive.
| Station(s): | Fort Peck |
| Parameter(s): | Direct and diffuse solar |
| Date(s): | 3, 20-31 May 1997 |
| Date Posted: | 23 Nov, 2009 |
Description of Change:
There were tracker related problems from March through May 1997 for Fort Peck. Bad direct and diffuse solar data from 1600-2300 UTC in March, April, and 5-19 May 1997 had been removed in the original daily editing. However for 3 May and 20-31 May the tracker was slightly off and those data were not edited out in the original daily processing. Those data have been removed in the present archive.
| Station(s): | Penn State |
| Parameter(s): | Direct and diffuse solar |
| Date(s): | 26 March - 9 July, 2000 |
| Date Posted: | 23 Nov, 2009 |
Description of Change:
There was a consistent unnatural dip in the direct solar signal from about 1500 through 2200 UTC on many days during that period that was not originally removed in the daily editing. There was also an apparent moisture-related problem in the NIP data that intermittently appeared during this period in the first hour or two after sunrise on some days during that period. Those problems have been resolved in the current data set on the SURFRAD FTP site.
| Station(s): | All Stations |
| Parameter(s): | Solar zenith angle |
| Date(s): | All SURFRAD Data |
| Date Posted: | 08 Apr. 2009 |
Description of Change:
A more accurate solar zenith angle calculation has been implemented in all code that deals with SURFRAD data. That includes the solar zenith angle calculation for the basic daily data files. On 8 Apr. 2009, all SURFRAD data from the beginning of each station onward was reprocessed to include the more accurate solar zenith angle. As of 8 Apr. 2009, all SURFRAD data files have been replaced in the ftp archive. The difference between the old solar zenith angle and new, more accurate calculation is minor.on the order of 0.2 deg.
| Station(s): | All Stations |
| Parameter(s): | All Parameters |
| Date(s): | 01 Jan. 2009 - onward |
| Date Posted: | 09 Jan. 2009 |
Description of Change:
A change from 3-min. to 1-min. data collection and processing at SURFRAD stations was made on 8 Jan. 2009, and all data files back to 1 Jan. 2009 were reprocessed to report 1-min. resolution data. This was possible because parallel 3-min. and 1-min. raw data files were collected from all SURFRAD stations since mid-December 2008 in preparation for the change. The new daily SURFRAD data files, beginning on 1 Jan. 2009, have, at most, 1440 lines of data. The 3-min. data files previous to the temporal resolution change have, at most, 480 lines of data. This change was made to conform to standards set by the Baseline Surface Radiation Network, an international organization of which SURFRAD is part of the U.S. contingent. The informational README file that describes the daily SURFRAD data files, available on the SURFRAD FTP site, has been updated accordingly.
| Station(s): | Penn State |
| Parameter(s): | Photosynthetically active radiation |
| Date(s): | 11 Oct. 2006 - 28 June 2007 |
| Date Posted: | 19 July 2007 |
Description of Change:
During the post instrument exchange check of instruments returning from monitoring at Penn State, it was discovered that the PAR quantum sensor that had been used at the Penn State SURFRAD station from 11 Oct. 2006 to 28 June 2007 had a bad calibration value. The effect of the bad calibration value was to produce a PAR irradiance that was about 7% lower than it should have been. On 19 July 2007, that problem was corrected and all Penn State PAR data was recalculated for the affected period (11 Oct. 2006 - 28 June 2007).
| Station(s): | Desert Rock, Table Mountain, Goodwin Creek, Penn State and Sioux Falls |
| Parameter(s): | Aerosol Optical Depth |
| Date(s): | Entire Record |
| Date Posted: | 19 December, 2006 |
Description of Change:
The SURFRAD aerosol optical depth (AOD) product has been changed to include the Angstrom exponent. The Angstrom exponent is computed using the 500-nm and 870-nm channels and is listed in the last column of the SURFRAD AOD data file. The README_AOD.txt file and web plotting routines have been adjusted to include the addition of the Angstrom exponent. The cloud screening has also been improved. All SURFRAD AOD data files for the duration of spectral measurements at the SURFRAD stations were regenerated on Dec. 19, 2006.
| Station(s): | Penn State |
| Parameter(s): | PAR |
| Date(s): | 3 September 2006 to 11 October 2006 |
| Date Posted: | 12 October, 2006 |
Description of Problem:
The PAR Quantum sensor at Penn State slowly lost sensitivity over the period from 3 September through 11 October 2006. That sensor was replaced at 1500 UTC on 11 October 2006. All Penn State PAR data for the affected period were marked with a bad quality control value and rewritten to the archive on 12 October 2006.
| Station(s): | Fort Peck, MT |
| Parameter(s): | Upwelling Infrared |
| Date(s): | 13 October 1999 to 27 September 2006 |
| Date Posted: | 04 October, 2006 |
Description of Problem:
On 27 September 2006 it was discovered that during the annual instrument exchange at the Fort Peck station on 13 October 1999, the upwelling pyrgeometer case and dome temperature connections at the data logger were swapped, but the processing code was not changed to accommodate that switch. On 4 October 2006, this problem was corrected and the Fort Peck data for the affected period were reprocessed. As of 4 October 2006, the Fort Peck upwelling infrared data from 13 October 1999 through 27 September 2006 are correct. (Previously, this same error was found with the downwelling thermal infrared irradiance at Fort Peck and was corrected in January 2005.) As of 4 October 2006, all historical Fort peck infrared data in the SURFRAD data archive are correct.
Errors in the Fort Peck upwelling thermal infrared irradiance that resulted from the reversal of the case and dome temperatures vary with the strength of the irradiance. The average case-dome temperature difference of the tower-mounted pyrgeometer is on the order of 0.1 degrees K, with the dome typically being warmer than the case. During the period that case and dome temperatures of the tower-mounted PIR were reversed, the computed upwelling infrared irradiance was, in most cases, erroneously high.
For example, for a typical summertime upwelling irradiance of 500 Wm^-2, the reversal of the case and dome temperatures would result in an error of +5 Wm^-2. For a 0.2 degree difference, the error would be +10 Wm^-2. For a typical wintertime upwelling irradiance of 300 Wm^-2, the errors for 0.1 and 0.2 degree case-dome temperature differences would be +3 and +6 Wm^2, respectively. Generally, the errors for 0.1 and 0.2 degree case-dome differences are +1% and +2%, respectively.
| Station(s): | All |
| Parameter(s): | Interpolated rawinsonde soundings file names |
| Date(s): | Entire record |
| Date Posted: | 11 Sept., 2006 |
Description of Problem:
On 7 Sept. 2006, the naming convention for the interpolated rawinsonde soundings file for SURFRAD was changed from dd-mmm-yyyy_hh.int (e.g. 07-sep-2006_12.int) to yyyymmdd_hh.int (e.g. 20060907_12.int for 7 Sept. 2006). The purpose of this change was to make the file name more easily manipulated in programming applications and for chronological file listing. All interpolated sounding files for dates before 7 Sept. 2006 have been renamed according the new filename convention.
Files generated after this date can only be downloaded using the new file name. For soundings predating September 7, the old file names will remain available through then end of December, 2006, at which time all historical and current data will be offered in the new file name structure only.
| Station(s): | All |
| Parameter(s): | Interpolated rawinsonde soundings' near-surface temperature |
| Date(s): | Entire record |
| Date Posted: | 11 Jan, 2006 |
Description of Problem:
In early January 2006, a problem was discovered in the near-surface temperature in the interpolated soundings at SURFRAD locations. Owing to variations in the surface elevation over North America, below-surface extrapolation of the input NWS sounding measurements is necessary to allow for stable horizontal interpolations at the lowest levels. It was discovered that under very stable low-level atmospheric conditions, too much flexibility was allowed in extrapolating below surface temperatures in the NWS soundings. Subsequently, extrapolated below-surface temperatures had the potential be too low. Because the problem occurred only in very stable surface conditions, it primarily affected 1200 UTC soundings. On 11 Jan. 2006, the problem was corrected and the entire SURFRAD interpolated sounding data set was recomputed and replaced in the ftp location.
| Station(s): | Penn State |
| Parameter(s): | PAR |
| Date(s): | 25 July to 12 September, 2005 |
| Date Posted: | 14 Sept, 2005 |
The Quantum sensor at Penn State slowly lost sensitivity over the period from 25 July through 12 September 2005. That sensor was replaced on 13 September 2005. All Penn State PAR data for the affected period were marked with a bad quality control value and rewritten to the archive on 14 September 2005.
| Station(s): | All |
| Parameter(s): | UVB |
| Date(s): | Entire record |
| Date Posted: | 20 June, 2005 |
Description of Problem:
The calibration of a UVB broadband instrument depends on the solar zenith angle, Rayleigh scattering and, the total column ozone overhead. To understand why that is so, refer to the article: "Methodology for deriving clear-sky erythemal calibration factors for UV broadband radiometers of the U.S. Central UV Calibration Facility," by Lantz et al., 1999, published in the Journal of Atmospheric and Oceanic Technology, vol. 16, 1736-1752. Figure 10a of that paper shows a family of erythemal calibration curves (as a function of the solar zenith angle) for Yankee UVB-1 instruments, with each curve representing differing total ozone amounts. Because we generally don't know the total ozone over a SURFRAD station at the time of the measurements, a nominal value of 300 Dobson units (DU) is assumed in the daily processing. Therefore UVB erythemal data in SURFRAD data files are correct only if the total ozone at the time of the measurement is 300DU. However, total ozone can vary between < 200DU to > 400DU.
The new README file for SURFRAD data files lists an ftp site from which SURFRAD data users can download a file (fit_ystECF_norm_surfrad.txt) that lists a table of coefficients for a third-order polynomial-fit correction equation, as a function of solar zenith angle. The polynomial fit can be used to correct the 300DU-based UVB values reported in SURFRAD data files to the UVB values appropriate the actual total ozone (if known). The table has 89 rows of (4) coefficients; each row corresponds to an integer solar zenith angle from 1 to 89. The table is "normalized" and can be applied to all SURFRAD UVB data. The header records of the file show, in an abbreviated way, how to use the table. Basically, select the row of coefficients corresponding to the solar zenith angle of the measurement, compute the correction factor by applying those coefficients and the actual total ozone, in DU, to the polynomial fit equation, and multiply the resultant correction factor times the 300 DU-based UVB value reported in the SURFRAD data file. Tests have shown that these corrections range between 0 and 5%.
| Station(s): | Fort Peck, MT |
| Parameter(s): | Downwelling Infrared |
| Date(s): | 13 October 1999 to 19 January 2005 |
Description of Problem:
On 18 May 2004 it was discovered that during the annual instrument exchange at the Fort Peck station on Oct 13 1999, the downwelling pyrgeometer case and dome temperature connections at the data logger were swapped, but the processing code was not changed to accommodate that switch. On 19 January 2005, this problem was corrected and the Fort Peck data for the affected period were reprocessed. As of 19 January 2005, the Fort Peck downwelling infrared from 13 October 1999 to 18 May 2004 are correct. Errors in the previously reported data (when the case temperature was used as the dome temperature, and vice verse) were on the order of 18 watts per square meter, depending on the dome and case temperatures.
While assessing the extent of the downwelling infrared problem caused by the case-dome swap, an oddity was discovered in the downwelling infrared data at Fort Peck between 10 December 2000 and 24 July 2001 where the case thermistor of the downwelling pyrgeometer lost sensitivity. A comprehensive analysis of the case and dome temperatures of the downwelling pyrgeometer showed that during that 8-month period the dome temperature was correct and the case thermistor was reading about 3-5 deg. K low. The case temperatures during that period were discarded. Using periods when the case and dome temperatures were known to be good, a linear relationship was established between the case-dome temperature difference and the thermopile reading of the affected downwelling pyrgeometer. That relationship was applied to the dome temperature and thermopile reading of the pyrgeometer during the erroneous 8-month period to compute artificial case temperatures. The corrected case temperatures were then used to recompute the downwelling thermal infrared for the period that the case temperature was bad. Comparisons with downwelling infrared data before and after this correction showed no discontinuity. Errors in the downwelling infrared associated with the use of artificially generated case temperatures were computed to be less than +/- 0.1 W/m2 at the 95% confidence level. The data from this 8-month period (10 December 2000 and 24 July, 2001) were also corrected and entered into the data record on January 19th, 2005.
| Station(s): | All |
| Parameter(s): | UVB (improved) |
| Date(s): | 24 Sept. 1997 to 2 Sept. 2004 |
Description of Problem:
The SURFRAD processing code has been improved to interpolate UVB calibration values to the date being processed.
Field UVB instruments are calibrated by transferring an ensemble calibration of three standard UVB broadband instruments, as a function of the solar zenith angle, to the field instrument. Particular field instruments are related to the ensemble UVB standards' triad through a scale factor that is determined before an instrument is deployed. The three UVB standard instruments are calibrated opportunistically when a UV spectroradiometer intercomparison is held at Table Mountain.about every three years. The standards' calibration applied to a particular field instrument, for a particular day, is now interpolated using the standards' calibrations from the two nearest intercomparisons. Prior to the use of interpolation, the most recent UVB standards' calibration before the day being processed was used for that day.
On September 2, 2004, the SURFRAD data set from 24 Sept. 1997 to 2 Sept. 2004 was reprocessed using the improved UVB data processing algorithm. If you use SURFRAD UVB data, please download the improved daily data files.
| Station(s): | Bondville, IL |
| Parameter(s): | Photosynthetically Active Radiation (PAR) |
| Date(s): | 14 July 2004 through 23 August, 2004 |
Description of Problem:
After a period of power problems and extended rain in mid-July at the Bondville, IL SURFRAD station, the sensitivity of the PAR instrument slowly dropped. This subtle decline was noticed by examining the behavior of the global SW to PAR ratio. It is suspected that the persistent rain caused the inside of the instrument to get wet. On August 24, the quantum sensor at Bondville was replaced, and the diagnostic ratio returned to normal values. On 27 August, 2004, the Bondville data from 14 July through 23 August, 2004, was reprocessed to change the quality control parameter of the PAR data to "bad" for the affected five-week period.
| Station(s): | Goodwin Creek, MS |
| Parameter(s): | All Data |
| Date(s): | 16 July 2004 to 26 August 2004 |
Description of Problem:
In mid-July, 2004, a power problem at the Goodwin Creek SURFRAD station prevented communication and data logging. After several failed attempts to fix the problem remotely by exchanging power supply, data logging and communication components on a piecemeal basis, SRRB personnel traveled to Mississippi to troubleshoot the problem. The culprit was found to be a short circuit (caused by a lightning strike) in the temperature and RH probe that caused the probe to drain the data logger's power. Because that instrument had been replaced earlier in the summer, it was not suspected during the remote troubleshooting. After the temperature and RH probe was replaced, stable power returned to the data logger and normal data collection resumed on 26 August 2004.
| Station(s): | Fort Peck, MT |
| Parameter(s): | Downwelling Infrared |
| Date(s): | 24 July, 2001 to 18 May, 2004 |
Description of Problem:
After a lightning strike in July, 2001, during repairs to the Fort Peck station, the downwelling pyrgeometer case and dome temperature connections at the data logger were accidentally swapped. The problem was discovered on May 18th, 2004. The data from the affected period were corrected and entered into the data record on May 19th, 2004. Errors in the previously reported data were on the order of 18 watts per square meter, depending on the dome and case temperatures.
| Station(s): | All |
| Parameter(s): | Diffuse solar, net solar, UVB |
| Date(s): | Entire Record |
Description of Problem:
All SURFRAD data from the beginning of each station.s tenure through February 19, 2004 have been reprocessed. New daily data files for this period are now in the anonymous FTP directories. The monthly averages and daily clear-sky identification files for each station.s tenure have also been recomputed. Several improvements have been made.
First, all diffuse data prior to the use of Eppley 8-48 pyranometers for the diffuse measurement in 2001, have been corrected for an offset that results from infrared cooling of the thermopile sensor that produces an erroneous negative value at night and an analogous offset during the day. The correction scheme followed the logic documented in Dutton et al., 2001, J. Atmos. and Ocean Tech., 18, 297-314, where a relationship is developed that relates the nighttime diffuse solar offset to the thermopile output of a collocated pyrgeometer. That relationship was then applied to all of the data, including daytime, for the duration of diffuse instrument.s tenure. The global solar measurement has a similar offset, but a reliable way to correct that data has yet to be determined. Therefore, the best estimate of total solar downward radiation flux from SURFRAD data is the component sum (direct*cos(SZA) + diffuse). The global solar measurement from the single pyranometer is considered redundant to that and should only be used if the direct and diffuse measurements are not available.
Second, the way that net solar radiation is computed has been improved to include twilight measurements of diffuse radiation. For the prior net solar calculation, all downward solar radiation was set to zero after the solar zenith angle exceeded 90 degrees. In the improved method, direct is set to zero for +90 degree solar zenith angles, but the diffuse value is zeroed after civil twilight ends. Again, this modification of the data is only done for the net solar calculation, and not to the recorded direct and diffuse data.
Third, the way that the SURFRAD broadband UVB instruments are calibrated has been improved. Before going to the field, the SURFRAD UVB instruments are calibrated by comparing them to three UVB standards at our Table Mountain Calibration Facility. Those standards are carefully calibrated using data from UV spectroradiometer intercomparisons held at Table Mountain. Before, only standards. calibrations for 1994 and 1997 were available. Therefore the 1997 calibrations were applied to all SURFRAD UVB data from 1997 through the present. Recently, the standards. calibrations for the 2003 intercomparison were released. A routine that interpolates the UV calibration values between the standards. calibration benchmarks was added to the SURFRAD data processing algorithm. The result is that all SURFRAD UVB data from 1995 to the present has the best possible calibrations applied, resulting in more accurate UVB SURFRAD data.
Last, a small error in file handling that resulted in one three-minute period to be missing from each daily SURFRAD data file has been fixed.
| Station(s): | Penn State |
| Parameter(s): | upwelling IR, net IR |
| Date(s): | Dec. 5 2000 to Jul. 16, 2001, and Jul. 26, 2001 to Aug. 29, 2001 |
Description of Problem:
The case temperature of the tower pyrgeometer was found to be bad during these periods. This resulted in a bad upwelling infrared calculation. To fix the problem, we set the case temperature equal to the dome temperature in the processing code for these periods. We then reprocessed the Penn State data on Oct. 28, 2002, and inserted the reprocessed data into the SURFRAD ftp archive.
| Station(s): | Bondville, Fort Peck, Goodwin Creek, Table Mt., Desert Rock, Penn State |
| Parameter(s): | net solar, total net |
| Date(s): | Entire record |
Description of Problem:
Improvements to the processing code that enable a better calculation of net solar radiation have been implemented. Before this change, net solar radiation was computed using the global solar measurement as the downwelling component. If that parameter was missing, net solar, and thus total net radiation, was reported as missing. Now, net solar is computed using total solar (direct + diffuse) as the primary downwelling solar quantity, and if either direct or diffuse is missing, the global solar measurement is then used to compute net solar calculation.
All data from the time shaded pyranometers were added to the SURFRAD stations to July 4, 2002 (the date when the improved code became operational) were reprocessed. This was finished on July 22, 2002. The only effects on the data files are that the net solar and net radiation have been changed. No other variables have been affected.
| Station(s): | Fort Peck, Penn State, Desert Rock, Table Mt. |
| Parameter(s): | various |
| Date(s): | July 6,7,8, 2001 |
Description of Problem:
On the weekend of July 6-8, lightning struck the Fort Peck, Desert Rock, and Table Mountain SURFRAD stations. Lightning also struck the Penn State station on June 30. Fort Peck sustained major damage to the data logging system, communications, and several instruments. The TSI and NIP at Desert Rock were damaged, and the upwelling PIR at Penn State was lost. There was only a power outage at Table Mountain--no instruments were damaged. All stations were back to normal operations by July 25, 2001
| Station(s): | All stations |
| Parameter(s): | Upwelling infrared |
| Date(s): | Beginning of each station to Dec. 6, 2000 |
Description of Problem:
On Dec. 6, 2000, we discovered that the downwelling pyrgeometer calibration factors were being applied to the upwelling pyrgeometer as well as the downwelling pyrgeometer. Since the temperature of the instrument is the largest signal, and the calibration factors for the thermopile and dome correction do not vary much among PIR instruments, the effect of this error in the upwelling PIR processing has only a very small impact. However, this problem was corrected, and all data from the beginning of the network to Dec. 6, 2000 were reprocessed with the correct calibration sequence. As of Dec. 22, 2000, all of the ftp directories have corrected SURFRAD data files.
| Station(s): | Desert Rock |
| Parameter(s): | Upwelling infrared |
| Date(s): | Sept. 18, 1999 to May 1, 2000 |
Description of Problem:
A severe electrical storm on Sept 18, 1999 ruined the thermopile on the tower-mounted pyrgeometer (that measures upwelling infrared irradiance) at Desert Rock, NV. The case and dome thermistors survived the strike. Since the thermopile signal of a pyrgeometer is small relative to that contributed by the instrument's thermistors, the erroneous upwelling infrared data were not noticed by the SURFRAD network operators. Thus the upwelling infrared data from Desert Rock from Sept. 18, 1999 to May 1, 2000 had to be flagged.
This change was made on May 10, 2000. As of that date, updated files have been resident on the SRRB ftp site. Please replace any Desert Rock files from Sept. 18, 1999 through May 1, 2000 (that you may have downloaded prior to May 10, 2000) with those currently on the ftp site.
| Station(s): | Bondville, Fort Peck, Goodwin Creek, Table Mountain |
| Parameter(s): | UVB |
| Date(s): | Jan. 1 to Apr. 24, 2000 |
Description of Problem:
On April 26, 2000, a problem was discovered with the operational UVB data processing for the Bondville, Fort Peck, Goodwin Creek, and Table Mountain SURFRAD stations from January 1, 2000 through April 24, 2000. The UVB irradiance values reported during that period for those stations were twice as large as they should have been. This has been corrected. On April 27, 2000, all data files from Jan. 1 through Apr. 24, 2000 for the four affected stations, were replaced with corrected files.
| Station(s): | Table Mountain |
| Parameter(s): | upwelling infrared |
| Date(s): | Feb. 28 to Apr. 14, 2000 |
Description of Problem:
On April 14, 2000, it was noticed that the tower pyrgeometer (that measures upwelling IR irradiance) at the Table Mountain SURFRAD station had been having intermittent problems for over a month. The upwelling IR for the period from Feb. 28 to April 14 were checked and edited appropriately on April 14. All necessary changes to the SURFRAD data files were made on that day and replaced in the archive. Also, the tower pyrgeometer was replaced on April 14.
| Station(s): | Bondville |
| Parameter(s): | upwelling PSP, UVB, temperature, RH, and pressure |
| Date(s): | July 26, 1999 |
Description of Problem:
During the annual instrument exchange at the Bondville SURFRAD station, which took place on July 20-22, 1999, all problems caused by the June 4, 1999 lightning strike were fixed. Many of these problems were traced to the data logger. As part of this year's instrument exchange, the entire data logging and communication system was replaced. The solar tracker was also found to be out of alignment and that was corrected during the exchange. Now all instruments at the Bondville station are reporting correctly.
| Station(s): | Bondville |
| Parameter(s): | upwelling PSP, UVB, temperature, RH, and pressure |
| Date(s): | June 4 - July 22, 1999 |
Description of Problem:
June 11, 1999
All data after the lightning strike on June 4, through June 7 were lost. By shifting connections on the data logger from blown channels to good ones, we were able to record data from all of the instruments. At that point it was determined that the pyranometer on the tower (measuring upwelling solar radiation) was damaged, and the barometer and temperature and relative humidity probe were destroyed. The UVB radiometer is now not heating properly, however the data are being recorded. Since the instrument is not at the correct temperature, the UVB irradiance values are being assigned bad QC flags. The station will be brought back to normal as soon as possible.
| Station(s): | ALL six stations |
| Parameter(s): | all UVB, 1 PSP at GWN, 1 PAR at BON |
| Date(s): | 1 Jan. 1995 through 12 April 1999 |
Description of Problem:
April 23, 1999
The entire SURFRAD data set has been reprocessed and new files have been generated. Changes include an improvement of the UVB algorithm and corrections of two calibration factors that were mistakenly used for two instruments, a PAR at Bondville (5/21/97-6/19/98), and a Goodwin Creek upwelling pyranometer (1/1/95-4/10/96).
As of the date of this notice (4/23/99), all SURFRAD data files in the ftp directories have been replaced with reprocessed data, and the README files have been updated.
Background information:
The UVB processing has been improved to compute UVB Diffey-weighted irradiance as a function of solar zenith angle. Also, calibration factors derived annually from standard instruments at SRRB's Central UV Calibration Facility have been retroactively applied to the network UVB instruments. Prior to this, a factory supplied calibration calibration factor for a representative solar zenith angle (40 degrees) was applied to the entire day's data.
It was discovered that the wrong calibration factor was applied to the PAR at Bondville for the period 5/21/97 to 6/19/98. The calibration factor mistakenly applied to the data was -274.54. The correct factor is -281.13; this value was applied in the reprocessing of the data.
A similar problem was found regarding the first upwelling pyranometer deployed at Goodwin Creek. The sensitivity factor mistakenly used was 8.620. It should have been entered as 8.260. The affected period is from Jan. 1, 1995 to April 10, 1996. This too has been fixed.
The entire reprocessed SURFRAD data set is now available from the SURFRAD ftp directories. All of the old files have been replaced. In the process of doing this exercise, all other calibration factors applied over the history of the SURFRAD Network have been verified to be correct.
| Station(s): | Fort Peck |
| Parameter(s): | UVB |
| Date(s): | 24 Sept 1997 through 26 Oct 1997 |
Description of Problem:
Fort Peck UV data have been reprocessed for the period Sept. 24, 1997 through Oct. 26, 1997, inclusive. The UV data during that period were erroneously reported as twice the magnitude that it should have been. The voltage divider circuit formerly used on this signal was removed on Sept. 23, 1997 during the annual instrument exchange. The real-time processing code for Fort Peck was not changed until October 27, 1997. This has been corrected as of 13 November 1998.
| Station(s): | Goodwin Creek only |
| Parameter(s): | Relative Humidity |
| Date(s): | 20 July 1997 through 02 June 1998 |
Description of Problem:
The replacement relative humidity (RH) chip installed at Goodwin during the 1997 maintenance and instrument exchange (on 7/10/97) was found to be faulty. All RH data from July 10, 1997 through June 2, 1998 (date of the 1998 instrument exchange) are erroneously low. Goodwin Creek data for this period were reprocessed and re-inserted into the archive on October 5, 1998. The RH values were retained in the processed data files, but they were flagged with bad QC values.
Background information on this problem:
The Campbell Scientific 207 temperature and RH sensor was originally installed at the first four SURFRAD stations. Subsequently, it was learned that the RH measuring ability of these sensors degraded within a year, and in regions of high humidity, the degradation rate was greatest. This presented a problem because SURFRAD stations are typically visited by SRRB representatives only once per year for the annual maintenance and instrument exchange. To remedy this, the 207 sensors were replaced with Campbell Scientific CS500 sensors, which have RH chips that are designed to last for two years. Those for Table Mountain and Fort Peck were replaced on 8/26/97 and 9/23/97, respectively. Those at Bondville and Goodwin Creek were replaced on 6/19/98 and 6/2/98, respectively. The two new stations at Desert Rock and Penn State were originally equipped with the CS500 probes.
For added quality assurance, the CS500 RH chips will be replaced annually, even though they are designed for a two-year deployment.
| Station(s): | Desert Rock, Penn State |
| Parameter(s): | Calculated Solar Zenith Angles |
| Date(s): | Installation through 04 August 1998 |
Description of Problem:
An error was found in the solar zenith angle calculation in the processing programs for the new PENN STATE and DESERT ROCK SURFRAD stations. Any data files from these stations downloaded before August 4, 1998 have erroneous solar zenith angles. No irradiance or meteorological parameters were affected by this error. The Desert Rock SURFRAD record started on March 16, 1998, and the Penn State SURFRAD record began on June 29, 1998.
As of August 4, 1998, all affected files have been replaced by corrected files in the SURFRAD anonymous FTP directories. If you downloaded any of these files before August 4, please download the files again.