Methods to Estimate Surface Roughness Length for Offshore Wind Energy

Table 1

Details about the two field campaigns conducted at the Cape Wind tower in Nantucket Sound and about the NDBC data set used in this study.

Campaign	Years	Reference level	Other levels	Level of	N. of valid data
CW Historical	2003–2007	20 m	41 m, 60 m	20 m	214,458
IMPOWR	2013-2014	12 m	—	12 m	19,633
NDBC	2003–2007	5 m	—	—	202,830