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Er Lu (elu@nuist) Nanjing University of Information Science and Technology

Monitoring Droughts and Rainfall Extreme Events: The Methods We Are Developing ( 干旱和极端事件监测检测的理论和方法研究 ). Er Lu (elu@nuist.edu.cn) Nanjing University of Information Science and Technology. Collaborators. NOAA CPC Wayne Higgins

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Er Lu (elu@nuist) Nanjing University of Information Science and Technology

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  1. Monitoring Droughts and Rainfall Extreme Events: The Methods We Are Developing (干旱和极端事件监测检测的理论和方法研究) Er Lu (elu@nuist.edu.cn) Nanjing University of Information Science and Technology

  2. Collaborators NOAA CPC Wayne Higgins Mike Halpert Kingtse Mo Iowa State U Eugene Takle CMA NCC Wenyue Cai Dianxiu Ye Bing Zhou Cunjie Zhang Qiang Zhang

  3. Drought (Flood) Monitoring Considerations WAP: Day-to-day monitoring, physically-based, using P only Lu E (2009): Determining the start, duration, and strength of flood and drought with daily precipitation: Rationale. Geophysical Research Letters, 36, L12707. SWAP: Standardize the WAP Lu E, et al. (2014): The day-to-day monitoring of the 2011 severe drought in China. Climate Dynamics, 43, 1-9. WAPE: In addition to P, include E Lu E, et al. (2018): Including evaporation in the precipitation-based method for monitoring drought at daily scale. J of the Meteorological Sciences, 38, 385-391. (in Chinese)

  4. Extreme P Event Monitoring Considerations EID: For single station, find extreme event from time series Lu E, et al. (2015): Determining starting time and duration of extreme precipitation events based on intensity. Climate Research, 63, 31-41. EIDR: Temporal-spatial simultaneously, to determine both the time period and the geographic region of an extreme event Lu E, et al. (2017):Temporal-spatial monitoring of extreme precipitation event: Determining simultaneously the time period it lasts and the geographic region it affects. Journal of Climate, 30, 6123-6132.

  5. Drought (Flood) P is the most important factor Weighted Average of Precipitation (WAP) Determining the start, duration, and strength of flood and drought with daily precipitation: Rationale Lu (2009 GRL)

  6. Change from conventional understanding • SPI • It always asks for a timescale. • The scale should be at least 1 month. • Simple average is made over the time period. • We think • Drought indicates the hydro-meteorological state of the soil-land surface system. It should be an instantaneous state (quantity). No matter what method we use, once it is defined, it should have a value at each moment (like T, …). • Drought monitoring should be performed at short timescales (daily or weekly). This is required by the decision-makers.

  7. 传统观念、SPI类指标的缺陷 在“国标”CI的业务监测中，常发现当强降水移出这个时间尺度的视窗时，会发生“骤旱”的现象。 在SPI（及其它以此为基础的）指标中，由于时段（N+1)之前的降水没有予以考虑，这个时间尺度因而必须是月以上的尺度。因此，SPI类指标是不适合用于旱涝逐日监测的。 Lu (2009 GRL)

  8. A Simple Physical Model Flood extent (f)：Instantaneous state (quantity） 涝的程度（大值表示涝；小值表示旱） 降水（强迫项；使涝的程度增加） 耗散项（参数化；径流、渗漏、蒸发等使涝的程度减小的综合作用） Lu (2009 GRL)

  9. Mathematical Processing Integration 当下 前期 因 ，故有 Discrete （用逐日资料） 1天 前期第n天 由精度定 Truncate （取有限天数） Lu (2009 GRL)

  10. WAP: our index for monitoring drought (flood) 降水的加权平均 Weighted Average of Precipitation 考虑了当下涝对前期降水的记忆、及记忆随时间的衰减（遗忘） Lu (2009 GRL)

  11. SPI: a special case of the WAP SPI是WAP的一个特例（当a1时） 等权重（权重不再随n衰减）：这是SPI总是需要一个时间尺度的原因 这里（N+1）即为SPI的时间尺度 Lu (2009 GRL)

  12. Suggested form for operational use Lu (2009 GRL)

  13. The day-to-day monitoring of the 1988 Drought and 1993 Flood over the Central US (using WAP) Lu (2009 GRL)

  14. Flood and drought can be well separated by the multi-year average 干旱过程和雨涝过程的确定对参数a的变化（从0.8到0.9）不敏感 1988年的干旱过程和1993年的雨涝过程能被多年平均区分开 雨涝 多年平均 WAP 干旱 Lu (2009 GRL)

  15. The day-to-day monitoring of the 2011 Spring Severe Drought over China with Standardized WAP (SWAP) Lu et al. (2014 CD)

  16. Standardization: from WAP to SWAP WAP是降水的线性求和，其概率密度也呈Gamma分布 将WAP正态化成SWAP，用两者的概率相等来求解 由WAP求解SWAP Gamma 正态 Lu et al. (2014 CD)

  17. Calculation Procedures P  WAP 2011 多年平均 WAP  SWAP 2011 春季每天都旱 中后期呈重旱 Lu et al. (2014 CD)

  18. The day-to-day monitoring of the 2011 spring drought Lu et al. (2014 CD)

  19. Including Evaporation in the method to provide more details (WAPE) Lu et al. (2017 JMS)

  20. As second step, E also needs to be considered A: no influence from P; soil is wet. B: no influence from P; soil is dry. Lu et al. (2017 JMS)

  21. Including E explicitly in the physical model Lu et al. (2017 JMS)

  22. Weighted Average of P-E (WAPE) Lu et al. (2017 JMS)

  23. Comparing WAPE with WAP Hangzhou, 2013 (ERA-interim) Lu et al. (2017 JMS)

  24. Extreme P Event For single station, find from time series “Extreme” Intensity – Duration (EID) Determining starting time and duration of extreme precipitation events based on intensity Lu et al. (2015 CR)

  25. Change from conventional understanding • How to deal with the “light rain” and the “break”? • We derive a “baseline” relation, and calculate the “relative intensity”. Lu et al. (2015 CR)

  26. The Binded Event (multi-day consecutive P) The “Size Effect”, or “Scale Effect” Lu et al. (2015 CR)

  27. Mathematical Model based on “Size Effect” Discount rates: unit price, pieces, total payment Buyer Seller Lu et al. (2015 CR)

  28. Equation and Parameter Lu et al. (2015 CR)

  29. Constraint Relation “Extreme” Intensity – Duration (EID) integration Lu et al. (2015 CR)

  30. Comparison among Durations ”Relative Intensity” Lu et al. (2015 CR)

  31. Sensitivity to the Parameter a= 0.6 a= 0.5 a= 0.4 Lu et al. (2015 CR)

  32. Heavy Rain during 21 July 2012 around Beijing Lu et al. (2015 CR)

  33. Apply the Principle of EID to Space “Extreme” Intensity – Region (EIR) The “binded event” in space: Compare the areas of different contours Lu et al. (2017 JC)

  34. Relation of “Extreme” Intensity with Region (EIR) Lu et al. (2017 JC)

  35. Simultaneous: Intensity with both Period and Region “Extreme” Intensity ~ (Duration & Region) Lu et al. (2017 JC)

  36. Over which Period and over which Region, the Event is most Extreme ? Temporal-spatial monitoring of extreme precipitation event: Determining simultaneously the time period it lasts and the geographic region it affects Lu et al. (2017 JC)

  37. Find Extreme Event from the Heavy Rainfall during May-July 1991 over East China Compare all the “relative intensities”, which are for all the “time periods” and “geographical contours”. Find the maximum. Lu et al. (2017 JC)

  38. The Geographical Region of the extreme event Averaged over the period of June 30 – July 11. Lu et al. (2017 JC)

  39. The Time Period of the Extreme Event June 30 – July 11 Averaged over the grid points embraced by the contour of 31. Lu et al. (2017 JC)

  40. Summary and Discussion We proposed a method to monitor drought at a daily scale, and a method to detect the extreme event’s region and time period. These methods are obtained from physical and mathematical models, based upon our understandings that are different from the conventional ones. Both methods contain only one parameter, which is adjustable and is a fractional number. For drought and extreme event, there is no “real” value that can be observed or measured. We realize that although whether it is drought and whether it is extreme are fairly objective, they may to some extent be subjective. The adjustable parameters contained in the two methods leave space for such uncertainties.

  41. Methods for Drought and Extreme Event • Drought / Flood: Monitoring at Daily Scale • Lu E (2009): Determining the start, duration, and strength of flood and drought with daily precipitation: Rationale. Geophysical Research Letters, 36, L12707. • Lu E, et al. (2014): The day-to-day monitoring of the 2011 severe drought in China. Climate Dynamics, 43, 1-9. • Extreme Event: Temporal-Spatial Monitoring • Lu E, et al. (2015): Determining starting time and duration of extreme precipitation events based on intensity. Climate Research, 63, 31-41. • Lu E, et al. (2017):Temporal-spatial monitoring of extreme precipitation event: Determining simultaneously the time period it lasts and the geographic region it affects. Journal of Climate, 30, 6123-6132.

  42. Methods for Monsoon Onset and Strength • Winter-Summer Unified Monsoon Onset Index • Lu E, Chan JCL (1999): A unified monsoon index for South China. Journal of Climate, 12, 2375-2385. • Globally Unified Monsoon Strength Index • Zeng X, Lu E (2004): Globally unified monsoon onset and retreat indexes. Journal of Climate, 17, 2241-2248.

  43. Methods for Dominance Analysis • Statistical Method • Lu E, et al. (2010): The relationships between climatic and hydrological changes in the Upper Mississippi River Basin: A SWAT and multi-GCM study. Journal of Hydrometeorology, 11, 437-451. • Lu E, et al. (2016): Is the interannual variability of summer rainfall in China dominated by precipitation frequency or intensity? An analysis of relative importance. Climate Dynamics, 47, 67-77. • Physical Method • Lu E, Takle ES (2010): Concurrent variations of water vapor and temperature corresponding to the interannual variation of precipitation in the North American Regional Reanalysis, Journal of Geophysical Research, 115, D11101. • Lu E, et al. (2011): Regional atmospheric anomalies responsible for the 2009–2010 severe drought in China. Journal of Geophysical Research, 116, D21114.

  44. Climate Monitoring and Analysis Tools Lu E (2009): Determining the start, duration, and strength of flood and drought with daily precipitation: Rationale. Geophysical Research Letters, 36, L12707. Lu E, et al. (2014): The day-to-day monitoring of the 2011 severe drought in China. Climate Dynamics, 43, 1-9. Lu E, et al. (2015): Determining starting time and duration of extreme precipitation events based on intensity. Climate Research, 63, 31-41. Lu E, et al. (2017):Temporal-spatial monitoring of extreme precipitation event: Determining simultaneously the time period it lasts and the geographic region it affects. Journal of Climate, 30, 6123-6132. Lu E, Chan JCL (1999): A unified monsoon index for South China. Journal of Climate, 12, 2375-2385. Zeng X, Lu E (2004): Globally unified monsoon onset and retreat indexes. Journal of Climate, 17, 2241-2248. Lu E, et al. (2010): The relationships between climatic and hydrological changes in the Upper Mississippi River Basin: A SWAT and multi-GCM study. Journal of Hydrometeorology, 11, 437-451. Lu E, et al. (2016): Is the interannual variability of summer rainfall in China dominated by precipitation frequency or intensity? An analysis of relative importance. Climate Dynamics, 47, 67-77. Lu E, Takle ES (2010): Concurrent variations of water vapor and temperature corresponding to the interannual variation of precipitation in the North American Regional Reanalysis, Journal of Geophysical Research, 115, D11101. Lu E, et al. (2011): Regional atmospheric anomalies responsible for the 2009–2010 severe drought in China. Journal of Geophysical Research, 116, D21114.

  45. Thanks ！ elu@nuist.edu.cn

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