Reconstructing climate trends adds skills to seasonal reference crop evapotranspiration forecasting

[摘要] Evapotranspiration plays an important role in the terrestrial water cycle. Reference crop evapotranspiration (ET o ) has been widely used to estimate water transfer from vegetation surface to the atmosphere. Seasonal ET o forecasting provides valuable information for effective water resource management and planning. Climate forecasts from general circulation models (GCMs) have been increasingly used to produce seasonal ET o forecasts. Statistical calibration plays a critical role in correcting bias and dispersion errors in GCM-based ET o forecasts. However, time-dependent errors resulting from GCM misrepresentations of climate trends have not been explicitly corrected in ET o forecast calibrations. We hypothesize that reconstructing climate trends through statistical calibration will add extra skills to seasonal ET o forecasts. To test this hypothesis, we calibrate raw seasonal ET o forecasts constructed with climate forecasts from the European Centre for Medium-Range Weather Forecasts (ECMWF) SEAS5 model across Australia, using the recently developed Bayesian joint probability trend-aware (BJP-ti) model. Raw ET o forecasts demonstrate significant inconsistencies withobservations in both magnitudes and spatial patterns of temporal trends,particularly at long lead times. The BJP-ti model effectively correctsmisrepresented trends and reconstructs the observed trends in calibratedforecasts. Improving trends through statistical calibration increases thecorrelation coefficient between calibrated forecasts and observations ( r ) by up to 0.25 and improves the continuous ranked probability score (CRPS) skill score by up to 15 (%) in regions where climate trends are misrepresented by raw forecasts. Skillful ET o forecasts produced in this study could be used for streamflow forecasting, modeling of soil moisture dynamics, and irrigation water management. This investigation confirms the necessity of reconstructing climate trends in GCM-based seasonal ET o forecasting and provides an effective tool for addressing this need. We anticipate that future GCM-based seasonal ET o forecasting will benefit from correcting time-dependent errors through trend reconstruction.

[学科分类] 妇产科学