Corrections were made to 2D wind speed and direction statistics in RELEASE-2022 and provisional data. Additional corrections to the quality metrics for this product are pending.
Errors were discovered in the computation of wind direction statistics (mean, variance, expanded uncertainty, and standard error of the mean) and wind speed uncertainty from NEON's 2D sonic anemometers on the tower profile (DP1.00001.001). All sites and time periods were impacted; however, please note that 3D wind data collected at the tower top (included as part of the eddy covariance data package) were not affected. The algorithm was corrected, all data were reprocessed, and corrected data are now available in provisional data and RELEASE-2022. The correction in mean wind direction was highest for northerly winds, on the order of 5-10 degrees, dropping to negligible for southerly winds. Variance in mean wind direction increased by about 50% for northerly winds, with negligible change for southerly winds. Standard error of the mean and expanded uncertainty for mean wind direction increased by approximately 1 and 2 orders of magnitude, respectively, for all wind directions. Expanded uncertainty for mean wind speed increased negligibly for 30-minute average data but increased on the order of 10% for 2-minute averages.
A separate error remains in the computation of the distorted flow quality metrics, which indicate whether or not the wind measurements were affected by tower infrastructure. Because the distorted flow quality metrics inform computation of the final quality flag, the final quality flag is also affected. The error most often results in over-flagging (indicating that the wind measurements were impacted by tower infrastructure when they were actually not), and has no impact on the wind direction statistics themselves. Only data from terrestrial sites are impacted, and mostly prior to 2018. Please see the issue log on the data product page (https://data.neonscience.org/data-products/DP1.00001.001) for a full list of impacted sites and time periods. Modifications are currently being made to correct the distorted flow quality metrics, forecasted to complete in February, 2022. At that point provisional data will be reprocessed, but any data collected prior to July, 2021 will not be updated until RELEASE-2023 is issued in January, 2023. Until the distorted flow quality metrics are corrected, we recommend that users download the expanded download package and use other quality metrics to inform data filtering. An update on this issue will be provided by March 15, 2022.