A phenology-based improvement for early agricultural drought detection
Abstract
The Standardized Precipitation Evaporation Index (SPEI) and the Evaporative Stress Index (ESI) are two drought indices which are popularly used for capturing agricultural drought - defined as drought events severe enough to affect plant growth. However, it remains unclear how the two drought indices reflect dynamics of agriculture drought indicators like anomalies of carbon uptake (Gross Primary Productivity: GPP), surface conductance (Gs, a proxy for stomatal conductance), soil moisture, and vapor pressure deficit (VPD). Moreover, it has not been characterized how interannual variability in phenological timing impacts and complicates early drought detection. In this study, we first compared ESI and SPEI at two broadleaf forest and two grassland flux sites and found that ESI performed better than SPEI in capturing drought onset dates from anomalies of GPP and Gs. However, we found phenology corrections largely affect decoupling of ET and PET and thus performance of ESI, especially early in the growing season. Therefore, we developed a new drought index () that accounts for phenological shifts in leaf area index (LAI). Results showed that drought onset dates indicated by are close to ( 2 weeks) the dates indicated by LAI corrected anomalies of Gs, and GPP, and the onset dates of soil water deficit or atmospheric aridity. Also, the can detect drought onsets up to 7 10 weeks earlier than SPEI and ESI, which indicates the skill of in detecting early agricultural drought signals which have been hidden or biased by earlier onset of spring leaf development.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFM.B13B..02C