Impacts of Fine‐Resolution Land Use Information of Beijing on a Summer Severe Rainfall Simulation

Abstract

AbstractUsing the land use data around Beijing in 2000 with a resolution of 500m, we updated the U.S. Geological Survey global land use classification data for numerical weather model, in which there are 25 types on a 30s lat‐lon equidistant grid (≈1 km resolution). And then by 24‐hour numerical experiments with the MM5V3.6 coupled with Noah LSM system, two domain two‐way nested with a resolution of 10:3.3 km, we investigated the impacts of fine‐resolution land use information incorporation on a summer severe rainfall in Beijing. Analyses show that, the new land use data can not only represent better the real characteristic of underlying surface around Beijing area, especially the rapid expanding of urban/built‐up areas since 1990's, but also help to correct the unreasonable classification of Savanna in the original USGS data for the deciduous broadleaf of middle‐latitude Asia. Furthermore, numerical experiments prove that incorporation of the fine‐resolution land use information has significant impact on the short‐range severe rainfall weather event. For the intensity and location of major rainfall centers, their difference ranges of 12 h rainfall amount are beyond 30 km, and the relative difference of the maximum rainfall amount reaches up to 30%. One important interaction mechanism between urban underlying surface and atmosphere is also revealed, that is, the urban expansion reduces natural vegetation cover, and then it can help to decrease ground evaporation and local water vapor supply, enlarge surface sensible heat flux, deepen PBL height and enhance the mixing of water vapor. Hence it is not favorable to the occurrence of the rainfall.