An investigation into the effect of spatial scale on the performance of a one-dimensional water balance model

✍ Scribed by T. J. Jolley; H. S. Wheater

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 294 KB
• Volume: 11
• Category: Article
• ISSN: 0885-6087
• DOI: 10.1002/(sici)1099-1085(199712)11:15<1927::aid-hyp540>3.0.co;2-k

✦ Synopsis

Land surface parameterizations used in atmospheric general circulation models (AGCMs) are one dimensional representations of the transfer of energy and water vapour at the earth's surface over grid squares that are typically of the order of 10 4 km 2 . It is known, however, that climate variables and land surface characteristics vary over scales of orders of magnitude less than this. It is therefore important that the eects of grid-scale aggregation are understood and appropriate methodologies for incorporating the signi®cant eects are developed. In this paper, an established two-layer bucket scheme is used as a vehicle to investigate the eects of aggregating spatially variable rainfall and soil moisture ®elds. The model is applied to two large UK catchments, the rivers Severn and Thames, at a daily time-scale using a grid scale of 40 km. A comparison with the observed river discharges for the period 1981 to 1990 shows that the model can simulate runo to within 1 and 13% for the Severn and Thames catchments, respectively. Distribution functions were introduced into the model to represent sub-grid variability of rainfall and available soil water capacity and so remove the bias associated with spatial averaging. Distribution functions also proved to be a useful tool for analysing the key controls on runo generation at the grid scale and so aid the development of large scale grid-based models.