ERA5-Land降水产品在黄河流域干旱监测中的适用性研究

doi:10.11755/j.issn.1006-7639(2023)-05-0677

摘要/Abstract

摘要：

ERA5-Land再分析产品作为全球重要的地表要素数据，其在干旱监测中的误差评估对进一步提升干旱预警能力和降低灾害风险具有重要意义。利用1981—2020年国家气象信息中心逐日降水格网数据，结合标准化降水指数（Standardized Precipitation Index， SPI），定量评价欧洲中期天气预报中心（European Centre for Medium-Range Weather Forecasts， ECMWF）的第五代再分析陆地产品（Land component of the Fifth Generation of European Reanalysis， ERA5-Land）降水资料在黄河流域及其子流域干旱监测中的误差特征，探讨ERA5-Land降水产品在不同地区和不同时间尺度下对降水的高（低）估以及对干旱特征的描述能力。结果表明：ERA5-Land降水产品在黄河流域对降水量存在明显高估现象，上游地区降水量高估误差最大，中游次之，而下游相对较低。在不同时间尺度下，ERA5-Land降水产品对干湿状况的反映能力存在明显差异，并随时间尺度的增加，差异也增加。针对黄河流域干旱事件，ERA5-Land降水产品存在明显的干旱频次高估和干旱历时低估。上游地区主要以干旱烈度和严重度高估为主，中下游则存在明显的干旱烈度和严重度低估现象。虽然ERA5-Land降水产品能够有效捕获典型干旱事件的空间分布，但对不同等级干旱面积的描述并不准确。因此，使用ERA5-Land降水产品数据进行干旱监测时，需特别注意其高估或低估现象。

关键词: ERA5-Land, 降水产品, 黄河流域, 干旱监测, 应用评价

Abstract:

The ERA5-Land reanalysis product is an important global data for surface variables, and its error assessment in drought monitoring is of great significance for further improving drought early warning ability and reducing disaster risk. Based on daily precipitation grid data from the National Meteorological Information Center during 1981-2020, combined with the standardized precipitation index (SPI), the error characteristics of the Land component of the Fifth Generation of European Reanalysis (ERA5-Land) precipitation data from the European Centre for Medium-Range Weather Forecasts (ECMWF) in monitoring drought in the Yellow River Basin and its sub-basins were evaluated quantitatively, and overestimate or underestimate of precipitation and the ability of describing drought characteristics of ERA5-Land precipitation products in different regions on different time scales were explored. The results show that the ERA5-Land precipitation products are obviously overestimated in the Yellow River Basin, especially in the upper reaches, followed by the middle reaches, and in the lower reaches errors are relatively small. At different time scales, the ability of ERA5-Land precipitation products to reflect dry and wet conditions is obviously different, and the difference increases with the increase of time scale. For drought events in the Yellow River Basin, the ERA5-Land precipitation products have obvious overestimation of drought frequency and underestimation of drought duration. In the upper reaches, drought intensity and severity are mainly overestimated, while in the middle and lower reaches, drought intensity and severity are obviously underestimated. Although the ERA5-Land precipitation products can effectively capture the spatial distribution of typical drought events, the description of drought areas of different grades is not accurate. Therefore, when using ERA5-Land precipitation products for drought monitoring, it is necessary to pay special attention to its overestimation or underestimation.

Key words: ERA5-Land, precipitation product, the Yellow River Basin, drought monitoring, applicability evaluation

中图分类号:

P426.616

朱丽, 吕潇雨, 郭浩, 孟翔晨, 田芸菲. ERA5-Land降水产品在黄河流域干旱监测中的适用性研究[J]. 干旱气象, 2023, 41(5): 677-687.

ZHU Li, LYU Xiaoyu, GUO Hao, MENG Xiangchen, TIAN Yunfei. Suitability study of ERA5-Land precipitation product for drought monitoring in the Yellow River Basin[J]. Journal of Arid Meteorology, 2023, 41(5): 677-687.

图/表 12

图1 黄河流域地形及气象站点空间分布

Fig.1 The terrain and spatial distribution of the meteorological stations in the Yellow River Basin

表1 基于标准化降水指数（SPI）的干旱等级划分

Tab.1 The classification of drought grades based on standardized precipitation index

SPI	干旱等级
SPI≥2.0	极端湿润
1.5≤SPI<2.0	严重湿润
1.0≤SPI<1.5	中度湿润
0.0≤SPI<1.0	轻微湿润
-1.0≤SPI<0.0	轻微干旱
-1.5≤SPI<-1.0	中度干旱
-2.0≤SPI<-1.5	严重干旱
SPI<-2.0	极端干旱

图2 干旱特征示意图

Fig.2 The sketch of drought characteristics

图3 1981—2020年黄河流域CPAP（a）和ERA5-Land降水产品（b）多年平均月降水量空间分布（单位：mm）

Fig.3 The spatial distribution of multiyear mean monthly precipitation of CPAP （a） and ERA5-Land precipitation products （b） in the Yellow River Basin during 1981-2020 （Unit： mm）

图4 1981—2020年黄河流域CPAP和ERA5-Land降水量月际变化

Fig.4 The monthly variation of precipitation of CPAP and ERA5-Land from 1981 to 2020 in the Yellow River Basin during 1981-2020

图5 1981—2020年黄河流域不同区域CPAP和ERA5-Land降水产品多年平均月降水量散点图（a）全流域，（b）上游，（c）中游，（d）下游

Fig.5 The scatterplots of multiyear mean monthly precipitation between CPAP and ERA5-Land precipitation products in different areas of the Yellow River Basin during 1981-2020 （a） the whole basin，（b） the upper reaches，（c） the middle reaches，（d） the lower reaches

图6 1981—2020年黄河流域不同区域CPAP和ERA5-Land平均降水量逐月变化（a）全流域，（b）上游，（c）中游，（d）下游

Fig.6 The monthly variations of mean precipitation in different areas of the Yellow River Basin of CPAP and ERA5-Land during 1981-2020 （a） the whole basin，（b） the upper reaches，（c） the middle reaches，（d） the lower reaches

图7 1981—2020年黄河流域不同时间尺度基于CPAP和ERA5-Land降水产品的区域平均SPI对比（a）SPI1，（b）SPI3，（c）SPI6，（d）SPI12

Fig.7 The comparison of regional mean SPI with different time scales in the Yellow River Basin during 1981-2020 （a） SPI1，（b） SPI3，（c） SPI6，（d） SPI12

图8 1981—2020年黄河流域基于CPAP（a、c、e、g）和ERA5-Land降水产品（b、d、f、h）的干旱频次（a、b，单位：次）、平均干旱历时（c、d，单位：月）、平均干旱严重度（e、f）及平均干旱烈度（g、h）空间分布

Fig.8 The spatial distribution of drought frequency （a， b， Unit： times）， average drought duration （c， d， Unit： month number）， average drought severity （e， f） and average drought intensity （g， h） based on CPAP and ERA5-Land precipitation products in the Yellow River Basin during 1981-2020

表2 1986—2013年黄河流域典型干旱事件特征

Tab.2 Characteristics of typical drought events in the Yellow River Basin from 1986 to 2013

事件	起止时间	峰值月份	干旱历时/月	烈度	峰值	严重度
D1	1986年7月至1987年4月	1986年11月	10	0.52	1.23	5.19
D2	1995年3—7月	1995年5月	5	1.15	1.64	5.75
D3	1998年9月至1999年6月	1999年2月	10	0.88	2.27	8.81
D4	2013年2—5月	2013年3月	4	0.70	1.41	2.79

图9 1986年11月（a、b）、1995年5月（c、d）、1999年2月（e、f）及2013年3月（g、h）黄河流域基于CPAP（a、c、e、g）和ERA5-Land降水产品（b、d、f、h）的不同等级干旱空间分布

Fig. 9 The spatial distribution of drought with different grades based on CPAP （a， c， e， g） and ERA5-Land precipitation products （b， d， f， h） in the Yellow River Basin in November 1986 （a， b）， May 1995 （c， d）， February 1999 （e， f） and March 2013 （g， h）

表3 The area ratio of drought with different grades at drought peak stage of typical drought events 单位：%

Tab.3

	事件	峰值月份	无干旱	轻微干旱	中度干旱	重度干旱	极端干旱
CPAP	D1	1986年11月	5	30	29	26	9
	D2	1995年5月	5	12	24	23	36
	D3	1999年2月	2	13	16	11	58
	D4	2013年3月	1	21	34	31	12
ERA5-Land	D1	1986年11月	3	32	39	21	5
	D2	1995年5月	10	25	27	22	16
	D3	1999年2月	16	13	10	20	41
	D4	2013年3月	1	6	25	37	31

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