Theoretical and Applied Climatology ( IF 3.4 ) Pub Date : 2020-07-10 , DOI: 10.1007/s00704-020-03287-0 Haim Kutiel , Jim Salinger , Daniel G. Kingston
The present study analyzes the spatial and temporal distributions of rain-spells and their characteristics in New Zealand. Various rain-spell parameters such as their average number (NRS), average yield (RSY), average intensity (RSI), and average duration (RSD) and the inter-correlations among all variables are analyzed. Intra-annual variability and the rain-spell characteristics during dry and wet years are presented. Daily rainfall totals from 19 stations on both islands for the period 1965–2017 were used. Rain-spell characteristics were defined using a daily rainfall threshold (DRT) of 1.0 mm. Various functions were fitted to represent the relationship between rain-spell characteristics and their duration-RSD. Dry and wet years were defined according to their standardized departures from the long-term mean:
Very dry (VD) when z < − 1.0
Dry (D) when − 1.0 ≤ z < − 0.5
Normal (N) when − 0.5 ≤ z ≤ 0.5
Wet (W) when 0.5 < z ≤ 1.0
Very wet (VW) when 1.0 < z
Rainfall totals in the different years were subject to cluster analysis (CA) and the various clusters were mapped. Temporal intra-annual uncertainty was estimated in two ways: (1) by calculating the mid-season date (MSD) and the variability from year to year around this date and (2) by calculating the range of percentages accumulated by the MSD.
The main results can be summarized as follows:
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RSY is the main factor that differentiates between dry and wet years, whereas NRS has only a very limited impact on the annual rainfall.
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The relationship between NRS and RSD is best described by an exponential curve, between the RSY and the RSD by a linear function and by a power function for the relationship between RSI and RSD.
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The coefficients of the various correlations in all stations serve to prepare charts of iso-lines of equal NRS, RSY, and RSI respectively for various selected RSDs.
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Most years were clustered into five different clusters according to their spatial distribution and their return period were calculated. Each cluster presents a different spatial distribution. For each cluster, the appropriate synoptic type according to Kidson classification was attributed.
中文翻译:
新西兰降雨法的时空特征
本研究分析了新西兰雨灾的时空分布及其特征。分析了各种降雨拼写参数,例如它们的平均值(NRS),平均产量(RSY),平均强度(RSI)和平均持续时间(RSD)以及所有变量之间的相互关系。给出了干旱和潮湿年份的年内变化和降雨法特性。使用了1965-2017年期间两个岛上19个气象站的日降水总量。使用1.0毫米的每日降雨阈值(DRT)定义了降雨法特性。拟合了各种功能以表示雨拼特征与其持续时间-RSD之间的关系。干燥和潮湿的年份是根据它们与长期平均值的标准偏差定义的:
当z <− 1.0时非常干燥(VD)
当-1.0≤z <-0.5时干燥(D)
正常(N)时- 0.5≤ ž ≤0.5
湿(W)时,0.5 < ž ≤1.0
1.0 < z时非常湿(VW)
对不同年份的降雨总量进行聚类分析(CA),并对各个聚类进行映射。年度时间内的不确定性有两种估算方法:(1)通过计算季节中日期(MSD)和该日期前后年份之间的变异性;(2)通过计算MSD累积百分比的范围。
主要结果可以总结如下:
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RSY是区分干湿年的主要因素,而NRS对年降雨量的影响非常有限。
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NRS和RSD之间的关系最好通过指数曲线来描述,RSY和RSD之间的关系可以通过线性函数以及RSI和RSD之间的关系的幂函数来最好地描述。
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所有站中各种相关系数用于分别为各个选定的RSD准备等值NRS,RSY和RSI的等值线图。
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根据年份的空间分布,将大多数年份分为五个不同的群集,并计算其返回期。每个群集呈现不同的空间分布。对于每个聚类,根据Kidon分类归类为适当的天气类型。