区域性极端骤发干旱与传统干旱事件形成过程的对比

doi:10.12006/j.issn.1673-1719.2021.212

摘要/Abstract

摘要：

2009/2010年云贵地区（YGR）和2013年夏季中南地区（CSC）发生了近几十年以来最严重的干旱事件。文中对比了两次干旱事件的发展速度,基于水分收支原理,诊断影响干旱发展的物理过程。结果显示,CSC干旱发展前,温度升高,蒸散发增加,土壤湿度减少,高温和降水减少对干旱有触发作用;而YGR的降水减少使干旱开始发展。CSC干旱事件发展迅速,YGR干旱事件发展缓慢,同时前者干旱的维持和恢复时间也短于后者,这些差异与蒸散发过程强弱有关。CSC干旱事件发展阶段,蒸散发过程强,平均为4.7 mm/d,8 d时间,土壤湿度从45%减少到20%,促使干旱快速形成（典型骤发干旱）。YGR干旱发展阶段,蒸散发过程弱,平均为1.7 mm/d,土壤湿度从45%减少到20%历时2个多月（传统干旱）。蒸散发的强弱主要与区域大气柱的水汽净辐散有关。CSC干旱发展阶段,其大气柱水汽净辐散达每天3.1 kg/m²,增强了陆气水分交换,使蒸散发远大于降水,土壤湿度快速下降,加快干旱发展速度。YGR的区域大气柱水汽净辐散为每天1.1 kg/m²,只有CSC的1/3,使干旱发展缓慢。两个干旱事件的大气柱水汽净辐散主要发生在经向方向,即由区域北界相对较强的经向水汽输送引起。

关键词: 骤发干旱, 传统干旱, 土壤湿度, 蒸散发, 大气柱水汽净辐散

Abstract:

The unprecedented drought on record occurred in the Yunnan-Guizhou region of China (YGR) during 2009/2010 and the central-south region of China (CSC) during the summer of 2013 in recent decades. The developing speed of the two drought events was analyzed. Based on the principle of water budget, the physical process that affects the development of drought was diagnosed. The results showed that before the development of CSC drought, temperature increased, evapotranspiration enhanced, soil moisture decreased, and high temperature and precipitation decrease had a triggering effect on the drought; while the decrease of precipitation in YGR caused the drought to develop. The CSC drought event developed rapidly, while the YGR drought event developed slowly. At the same time, the maintenance and recovery time of drought in the former is shorter than that in the latter. These differences are related to the strength of the evapotranspiration process. During the developing stage of the CSC drought event, the evapotranspiration process was strong, with an average of 4.7 mm/d and within 8 days, the soil moisture decreased from 45% to 20%, prompting the rapid formation of drought (flash drought). During the YGR drought developing stage, the evapotranspiration process was weak, with an average of 1.7 mm/d, and the reduction of soil moisture from 45% to 20% lasted more than 2 months (traditional drought). The strength of evapotranspiration is mainly related to the net divergence of water vapor in the regional atmospheric column. During the drought developing stage of CSC, its water vapor net divergence in the atmospheric column reached 3.1 kg/m² per day, which enhanced the land-atmosphere water exchange, making the evapotranspiration much greater than precipitation, and the rapid decline of soil moisture, accelerating the development of drought. The net divergence of water vapor in the regional atmospheric column of YGR was 1.1 kg/m² per day, which was only 1/3 of that of CSC, which slowed the development of drought. The net divergence of atmospheric column water vapor of the two drought events mainly occurred in the meridional direction, that is, caused by the relatively strong meridional water vapor outflow at the northern boundary of the region.

Key words: Flash drought, Traditional drought, Soil moisture, Evapotranspiration, Net divergence of atmospheric column water vapor

叶天, 余锦华, 施欣池. 区域性极端骤发干旱与传统干旱事件形成过程的对比[J]. 气候变化研究进展, 2022, 18(3): 319-327.

YE Tian, YU Jin-Hua, SHI Xin-Chi. Comparison in developing process between extreme regional flash drought and traditional drought events[J]. Climate Change Research, 2022, 18(3): 319-327.

图/表 7

图1 1979—2020年CSC 7—8月份和YGR 1—4月份平均SPEI和土壤湿度的时间序列注：竖线表示干旱事件所在年份;r为两序列的相关系数。

Fig. 1 The time series of the averaged SPEI and soil moisture over the central-south region of China (CSC) from July to August (a) and the Yunnan-Guizhou region (YGR) from January to April (b) during 1979-2020

图2 2013年CSC 和2009/2010年YGR干旱事件土壤湿度的演变和各阶段持续天数

Fig. 2 The temporal evolution of the soil moisture averaged over the CSC in 2013 (a) and the YGR from 2009 to 2010 (b)

图3 2013年CSC 和2009/2010年YGR干旱各个阶段的日最高气温、土壤湿度变化、蒸散发和降水的5 d滑动平均值的演变

Fig. 3 The temporal evolution of the 5-day running mean of observed daily maximum temperature, evapotranspiration, soil moisture change and precipitation during drought development, maintenance and recovery stage over the CSC in 2013 (a) and the YGR from 2009 to 2010 (b)

表1 CSC和YGR干旱事件各物理量在各阶段的相关系数

Table 1 Correlation coefficients between physical quantities for CSC drought event in pre-development (26/6-3/7 2013), development(4/7-11/7 2013), maintenance (12/7-12/8 2013) and recovery stage (13/8-20/8 2013) and YGR one in pre-development (1/8-2/9 2009), development (3/9-14/11 2009), maintenance (15/11 2009-21/3 2010) and recovery stage (22/3-21/4 2010). (The asterisk in the upper right corner indicates that the significance reaches the 95% confidence level)

图4 同图3,但为大气柱水汽净辐散、大气柱水汽变化,以及蒸散发与降水之差的演变

Fig. 4 Same as Fig. 3, except for the curve of net divergence of atmospheric column water vapor, atmospheric column water vapor change, and the difference between evapotranspiration and precipitation

表2 2013年CSC干旱事件和2009/2010年YGR干旱事件的对比

Table 2 Comparison of the CSC drought event and the YGR drought event

图5 2013年CSC和2009/2010 YGR干旱发展阶段区域四个边界整层大气的水汽输送通量

Fig. 5 The water vapor transport flux of the entire atmosphere at the four boundaries of the region during the drought development stage over the CSC in 2013 (a) and the YGR from 2009 to 2010 (b)

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