Intra‐annual differences of 3‐month Standardized Precipitation‐Evapotranspiration Index dryness/wetness sensitivity over southwest China

• Published in: Atmospheric science letters 2018-08, Vol.19 (8), p.n/a
• Main Authors: Sun, Shanlei, Ren, Yongjian, Li, Qingqing, Zhou, Shujia, Zhao, Changyu, Chai, Rongfan, Deng, Peng, Wang, Jie
• Format: Article
• Language: English
• Subjects: Annual; Annual precipitation; Anomalies; Atmospheric sciences; Climatology; Dependent variables; Drought; Drought forecasting; dryness/wetness sensitivity; Emergency preparedness; Evapotranspiration; Evapotranspiration-precipitation relationships; Independent variables; intra‐annual differences; Moisture content; Monthly; Monthly precipitation; Precipitation; Sensitivity; southwest China; Standardized Precipitation‐Evapotranspiration Index
• ISSN: 1530-261X; 1530-261X
• DOI: 10.1002/asl.830

The monthly 3‐month Standardized Precipitation‐Evapotranspiration Index (SPEI‐3) over southwest China (SWC) shows obvious inter‐annual and inter‐decadal variability during 1961–2012. By examining the isolated contributions of precipitation and reference evapotranspiration (ET0) alone to the monthly SPEI‐3 anomalies, we find out that although anomalous precipitation plays a predominant role, ET0 impacts cannot be neglected, particularly during February–May. The monthly dryness/wetness sensitivity to precipitation (Sp; Set0 for ET0), that is, SPEI‐3 changes by per millimetre of precipitation (ET0) anomalies, is quantified as the slope of a linear regression, which has precipitation (ET0) contributions and anomalies during 1961–2012 as the dependent and the independent variables, respectively. Both SWC Sp and Set0 have evident intra‐annual differences, decreasing during February–August and increasing afterwards. Moreover, their magnitudes are dependent on climatological precipitation and generally decrease with precipitation increase. To sum up, the estimated respective contributions of monthly precipitation and ET0 anomalies are favourable for thoroughly understanding SWC dry/wet condition evolutions during the past 52 years. More importantly, Sp and Set0 are of significance for drought forecasting and emergency system over SWC. Over southwest China (SWC), determinants (i.e., precipitation and reference evapotranspiration [ET0]) of monthly dryness/wetness anomalies are identified. Monthly dryness/wetness sensitivity to precipitation (ET0) has evident intra‐annual differences and decreases during February–August and afterwards increases. Dryness/wetness sensitivity is dependent on monthly climatological precipitation.