## 3 Results
### Hydroclimate and Wind Regimes at the Focus Sites
Despite the large degree of site-to-site variability for mean DSD at a given RR (Figure 4d) and the variability at a given site in different RR classes (e.g., Figure 5a), the slope of all DSD curves (number density as a function of droplet diameter) from all sites exhibit a shallower gradient with \(D\) than are manifest in either the Best or Marshall-Palmer approximations especially at high RR. This is particularly important given the relevance of high RR and the associated larger droplet diameters to potential kinetic energy to the rotating blades. The implication of these analyses is that if whirling-arm experiments are sampling DSD from Best rain droplet distribution they are not fully representing atmosphere-relevant DSD. Such experiments may be under-sampling the abundance of larger droplets (\(D>0.5\) mm) that are likely to induce the largest material stresses [140]. For this reason, we recommend that RR and DSD considered in whirling-arm experiments be greatly expanded to cover a wider range of conditions. It is also noted that the highly accelerated RET do not realistically represent operational modes for wind turbines and have the drawback that for viscoelastic coatings other damage types may be observed. Thus, use of lower speeds to better reflect real-life wind turbine blades in service may be advantageous. Furthermore, we recommend use of a broad-spectrum of droplet sizes (similar to the spray mode used in [PERSON] et al. [140]) rather than a nearly uniform \(D\) currently used for the testing, and that the suggestion to confine the range of droplet D to \(<6\) mm as recommended in the DNV Recommended Practice be reconsidered. Data from the North Sea offshore wind farm indicate a DSD that deviates substantially from the other locations from which data are presented and also from theoretical expectations (Figure 8). DSD from this dishormeter may reflect the presence of a mixed droplet distributions due to both hydrometeors and sea spray. Sea spray droplets range in diameters from \(<\)1 \(\upmu\)m (film droplets, generated by biogeochemistry and bubble bursting), to 1-50 \(\upmu\)m (jet droplets, generated by bubble bursting and the impact of rain droplets on the sea surface), to spume droplets that have diameters up to a few mm and are generated by wave tearing and wave breaking on structures/vessels [141; 142]. Such mixed DSD have been previously demonstrated in data collected using a dishormeter at 16 m ASL on an offshore marine tower in Japan [105]. In light of this issue, we do not consider the North Sea data set further. Nevertheless, production of high-quality hydrometeor size distributions and precipitation intensity datasets from dishorometers or other sensors installed on offshore platforms (e.g., buoys and/or meteorological masts, transformer platforms) is essential to quantifying LEE potential for offshore wind turbines. We recommend that either; (i) hydrometeor DSD measurements at offshore wind farms for the purpose of LEE analyses be performed preferentially using remote sensing devices (e.g., MRR). By virtue of sampling higher above the surface, they may be less vulnerable to sea spray contamination. Or alternatively, (ii) studies be conducted to investigate and quantify the influence of sea spray on such measurements and develop filtering methods for data quality control based on wind speed, wave properties, etc. When the mean DSD from optical dishorometers at four of the sampling sites are compared for the same fixed RR interval, the results indicate important differences (Figure 4d). Some of these differences may derive from the relatively small sample size at some locations and/or differences in measurement technology (at coastal UK). It is noteworthy that the DSD reported above for our selected study sites are in contrast to a year of data collected using a PWS100 dishormeter deployed 5.5 km off the east coast of the UK [143]. Analyses of those data indicated \"the Best DSD significantly overestimates the diameter of droplets\" [143].