Abstract. Local spatiotemporal nonstationarity occurs in various natural
and socioeconomic processes. Many studies have attempted to introduce time
as a new dimension into a geographically weighted regression (GWR) model,
but the actual results are sometimes not satisfying or even worse than the
original GWR model. The core issue here is a mechanism for weighting the effects
of both temporal variation and spatial variation. In many geographical and
temporal weighted regression (GTWR) models, the concept of time distance has
been inappropriately treated as a time interval. Consequently, the combined
effect of temporal and spatial variation is often inaccurate in the
resulting spatiotemporal kernel function. This limitation restricts the
configuration and performance of spatiotemporal weights in many existing
GTWR models. To address this issue, we propose a new spatiotemporal weighted
regression (STWR) model and the calibration method for it. A highlight of
STWR is a new temporal kernel function, wherein the method for temporal
weighting is based on the degree of impact from each observed point to a
regression point. The degree of impact, in turn, is based on the rate of
value variation of the nearby observed point during the time interval. The
updated spatiotemporal kernel function is based on a weighted combination of
the temporal kernel with a commonly used spatial kernel (Gaussian or
bi-square) by specifying a linear function of spatial bandwidth versus time.
Three simulated datasets of spatiotemporal processes were used to test the
performance of GWR, GTWR, and STWR. Results show that STWR significantly
improves the quality of fit and accuracy. Similar results were obtained by
using real-world data for precipitation hydrogen isotopes (δ2H) in the northeastern United States. The leave-one-out cross-validation
(LOOCV) test demonstrates that, compared with GWR, the total prediction
error of STWR is reduced by using recent observed points. Prediction
surfaces of models in this case study show that STWR is more localized than
GWR. Our research validates the ability of STWR to take full advantage of
all the value variation of past observed points. We hope STWR can bring
fresh ideas and new capabilities for analyzing and interpreting local
spatiotemporal nonstationarity in many disciplines.