Global maps of seasonality indices

The global distribution hydroclimatic seasonality was evaluated using seven existing metrics (Maps_seasonality_indices.pdf). Each .txt file contains the metric values calculated from the mean monthly climatological precipitation (P) and/or potential evapotranspiration (PET) data within the CRU TS dataset version 4.03 (Harris et al. 2014), at 0.5 degree grid resolution. More information on how each metric value was calculated can be found in the included Table_seasonality_indices.pdf. The Python code simulate_sinusoid_P_PET.py produces different synthetic variations of sinusoidal seasonal distributions of P and PET that vary in terms of their relative amplitudes and phases, and calculates their associated asynchronicity index values.

1. Asynchro.txt: the asynchronicity index proposed in Feng et al. (2019).
2. dCentroid: the centroid difference (in months) between the seasonal precipitation and PET pmfs
3. WalshS.txt: seasonality index of Walsh & Lawler (1981)
4. MillyS.txt: seasonality index of Milly (1994)
5. dP*.txt: seasonality index of Woods (2009)
6. SI.txt: seasonality index of Feng et al. (2013)
7. Imr.txt: seasonality index of Knoben et al. (2018)

References:
Feng, X., Porporato, A., & Rodriguez-Iturbe, I. (2013). Changes in rainfall seasonality in the tropics. Nature Climate Change, 3(9), 811–815. https://doi.org/10.1038/nclimate1907

Feng, X. Thompson, S.E., Woods, R., & Porporato, I. (2019). Quantifying asynchronicity of precipitation and potential evapotranspiration in Mediterranean climates. Geophysical Research Letters.

Harris, I., Jones, P. D., Osborn, T. J., & Lister, D. H. (2014). Updated high-resolution grids of monthly climatic observations - the CRU TS3.10 Dataset. International Journal of Climatology, 34(3), 623–642. https://doi.org/10.1002/joc.3711

Knoben, W. J. M., Woods, R. A., & Freer, J. E. (2018). A Quantitative Hydrological Climate Classification Evaluated With Independent Streamflow Data. Water Resources Research, 54(7), 5088–5109. https://doi.org/10.1029/2018WR022913

Milly, P. C. D. C. D. (1994). Climate, interseasonal storage of soil water, and the annual water balance. Advances in Water Resources, 17(1–2), 19–24. https://doi.org/10.1016/0309-1708(94)90020-5

Walsh, R. P. D., & Lawler, D. M. (1981). Rainfall Seasonality: Description, Spatial Patterns and Change Through Time. Weather, 36(7), 201–208. https://doi.org/10.1002/j.1477-8696.1981.tb05400.x

Woods, R. A. (2009). Analytical model of seasonal climate impacts on snow hydrology: Continuous snowpacks. Advances in Water Resources, 32(10), 1465–1481. https://doi.org/10.1016/j.advwatres.2009.06.011

本数据集针对全球水文气候季节特征分布展开评估，采用7项现有指标（详见Maps_seasonality_indices.pdf）。所有.txt格式文件均存储了基于CRU TS 4.03版本数据集（Harris等，2014）的月平均气候态降水（Precipitation, P）和/或潜在蒸散发（Potential Evapotranspiration, PET）数据计算得到的指标值，空间分辨率为0.5度网格。各项指标的具体计算方法可参阅附件Table_seasonality_indices.pdf。Python脚本simulate_sinusoid_P_PET.py可生成降水与潜在蒸散发的正弦型季节分布的多种合成变体，其相对振幅与相位均存在差异，并可计算对应的异步性指数值。

各数据文件说明如下：
1. Asynchro.txt：对应Feng等（2019）提出的异步性指数
2. dCentroid：季节尺度降水与潜在蒸散发概率质量函数（Probability Mass Functions, PMFs）之间的质心差异（单位：月）
3. WalshS.txt：Walsh与Lawler（1981）提出的季节指数
4. MillyS.txt：Milly（1994）提出的季节指数
5. dP*.txt：Woods（2009）提出的季节指数
6. SI.txt：Feng等（2013）提出的季节指数
7. Imr.txt：Knoben等（2018）提出的季节指数

参考文献：
Feng, X., Porporato, A., & Rodriguez-Iturbe, I. (2013). 热带降雨季节特征的变化. 自然·气候变化, 3(9), 811–815. https://doi.org/10.1038/nclimate1907
Feng, X., Thompson, S.E., Woods, R., & Porporato, I. (2019). 地中海气候下降水与潜在蒸散发异步性的量化. 地球物理研究通讯.
Harris, I., Jones, P. D., Osborn, T. J., & Lister, D. H. (2014). 高分辨率月度气候观测格点数据集更新——CRU TS3.10数据集. 国际气候学杂志, 34(3), 623–642. https://doi.org/10.1002/joc.3711
Knoben, W. J. M., Woods, R. A., & Freer, J. E. (2018). 基于独立径流数据验证的定量水文气候分类系统. 水资源研究, 54(7), 5088–5109. https://doi.org/10.1029/2018WR022913
Milly, P. C. D. C. D. (1994). 气候、土壤水季节间存储与年度水量平衡. 水科学进展, 17(1–2), 19–24. https://doi.org/10.1016/0309-1708(94)90020-5
Walsh, R. P. D., & Lawler, D. M. (1981). 降雨季节特征：描述、空间格局与时间变化. 天气, 36(7), 201–208. https://doi.org/10.1002/j.1477-8696.1981.tb05400.x
Woods, R. A. (2009). 季节气候对积雪水文影响的解析模型：连续积雪层. 水科学进展, 32(10), 1465–1481. https://doi.org/10.1016/j.advwatres.2009.06.011