The statistical properties of ocean wave groups are extremely important for the analysis of resonant effects on ships and marine structures. The patterns in combined sea states have attracted increasing attention recently. This study focuses on the probability distributions of the group height and group length as defined by an envelope approach in sea states with bimodal spectra. Wave data from laboratory experiments and numerical simulations are used. The envelope spectra in combined sea states might exhibit a double-peaked structure. Although the bimodal envelope spectrum has slight effect on the group height distribution, the group length might have a multimodal and broader distribution. As a result, the joint distribution might be characterised by a multimodal shape. Further, a mixed Weibull distribution of the marginal distributions of the group parameters and a mixed copula model of their bivariate distributions are constructed. For comparison, a conventional Weibull distribution and a single copula model are also applied to fit the distributions. The results suggest that the single models can be used only to fit the group height distribution. By contrast, the mixed models can provide satisfactory descriptions of both the marginal distributions and joint distributions.

海浪群的统计特性对于分析对船舶和海洋结构的共振效应极为重要。近来，联合海州的模式引起了越来越多的关注。这项研究的重点是在具有双峰光谱的海州中，通过包络法确定的群高和群长的概率分布。使用了来自实验室实验和数值模拟的波浪数据。合并海域中的包络光谱可能显示出双峰结构。尽管双峰包络谱对组高度分布影响不大，但组长可能具有多峰分布和较宽的分布。结果，关节分布的特征可能在于多峰形状。进一步，建立了群参数的边际分布的混合威布尔分布和它们的二元分布的混合copula模型。为了进行比较，还应用了常规的威布尔分布和单个copula模型来拟合分布。结果表明，单个模型只能用于拟合组的高度​​分布。相反，混合模型可以提供令人满意的边际分布和联合分布的描述。