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This paper uses an urbanized high-resolution land data assimilation system (u-HRLDAS) to parameterize the urban land surface characteristics. The u-HRLDAS model is localized and developed in order to satisfy the need of the weather forecast in Beijing, China. The remote sensing data used to localize and drive u-HRLDAS include the soil type data and MODIS retrieved leaf area index (LAI) data. The evaporation and water depth for impervious surface in urban area are developed to improve the simulation of u-HRLDAS. The result of the urban weather forecast is used for the comparison based on the rapid update cycle system at Beijing Meteorological Bureau (BJ-RUC) without coupled with u-HRLDAS. The land surface temperature, land surface fluxes, and first layer soil moisture in several single sites and urban Beijing region by BJ-RUC are compared with u-HRLDAS after localization and development. The off-line simulation results indicate that compared with BJ-RUC, after the localization and development, u-HRLDAS can improve the simulation of land surface parameters and fluxes definitely. [ABSTRACT FROM AUTHOR]

This paper studies interdecadal variations of heat waves and sultry weather (HW&SW) in Beijing City by using climatological data gathered from 1940-2000. In general, HW&SW decreased during the 1940s-1970s and increased during the 1970s-1990s. Although variation trends in the number of HW&SW days coincide with air temperature variations, the greatest number of HW&SW days occurred during the 1940s rather than during the much hotter 1990s (which had an average 1.0°C higher air temperature than during the 1940s). The synoptic situations of HW&SW and the correlation analysis between HW&SW occurrences and the Western Pacific Subtropical High (WPSH) index seem to indicate that HW&SW days during the 1990s should exceed those during the 1940s; however, that is not the case. Post-1980s interdecadal variations of the Urban Dry Island (UDI) effect in Beijing City were analyzed in order to explain this inconsistent phenomenon. Our results show that, while the probability of HW&SW occurrences in Beijing City should have been greater due to global warming and increasing summer Urban Heat Island (UHI) intensity, the UDI effect is magnified by rapid urbanization. In addition, the physical comfort index is more sensitive to relative humidity under high temperature conditions. Therefore, the occurrence of HW&SW days during the 1990s is partially offset by the enhanced UDI in Beijing City. [ABSTRACT FROM AUTHOR]