Effects of Initial Drivers and Land Use on WRF Modeling for Near-Surface Fields and Atmospheric Boundary Layer over the Northeastern Tibetan Plateau

To improve the simulation performance of mesoscale models in the northeastern Tibetan Plateau, two reanalysis initial datasets (NCEP FNL and ERA-Interim) and two MODIS (Moderate-Resolution Imaging Spectroradiometer) land-use datasets (from 2001 and 2010) are used in WRF (Weather Research and Forecasting) modeling. The model can reproduce the variations of 2 m temperature (T2) and 2 m relative humidity (RH2), but T2 is overestimated and RH2 is underestimated in the control experiment. After using the new initial drive and land use data, the simulation precision in T2 is improved by the correction of overestimated net energy flux at surface and the RH2 is improved due to the lower T2 and larger soil moisture. Due to systematic bias in WRF modeling for wind speed, we design another experiment that includes the Jimenez subgrid-scale orography scheme, which reduces the frequency of low wind speed and increases the frequency of high wind speed and that is more consistent with the observation. Meanwhile, the new drive and land-use data lead to lower boundary layer height and influence the potential temperature and wind speed in both the lower atmosphere and the upper layer, while the impact on water vapor mixing ratio is primarily concentrated in the lower atmosphere

Monsoon variability in Himalayas under the condition of global warming

An ice core-drilling program was carried out at the accumulation area of Dasuopu glacier (28°23\u27N, 85°43\u27E, 7100m a.s.1.) in the central Himalayas in 1997. The ice core was analyzed continuously for stable isotopes (δ18O) and major ions throughout the core. Cycles indicated by δ18O, cations were identified and counted as seasonal fluctuations as annual increment from maximum to maximum values. Reconstructed 300・year annual net accumulation (water equivalent) from the core, with a good correlation to Indian monsoon, reflects a major precipitation trend in the central Himalayas. The accumulation trend, separated from the time series, shows a strong negative correlation to Northern Hemisphere temperature. Generally，as northern hemisphere temperature increases 0.1・C, the accumulation decreases about 80mm, reflecting monsoon rainfall in central Himalayas has decreased over the past decades in the condition of global warming

Comparison of cations recorded in Antarctica and the Qinghai-Tibetan Plateau ice core by using fuzzy cluster analysis

A new approach of glacier classification is suggested on the basis of fuzzy cluster analysis of cations in ice cores. Cations in an ice core act as a synthetic index to reflect both the local and the global climate. Fuzzy cluster analysis of long time series data of cations in ice cores from five representative glacial ice cores (from south to north) has been used to create a similarity scale matrix R among these glaciers. Accordingly, any change in R represents a change in environment and climate. This type of analysis can determine the relativity of samples (glaciers) according to a cluster level (λ). Fuzzy cluster analysis of cations in ice cores collected from Antarctica and the Qinghai-Tibetan Plateau indicates drastic difference between glaciers of these two regions

Urbanization Effects on Human-Perceived Temperature Changes in the North China Plain

Urbanization and associated land use changes significantly alter the energy and radiation balance, land surface characteristics, and regional climates, posing challenges to natural ecosystems and human society. The combined effects of changes in air temperature (T), relative humidity (RH), and wind speed (WS) profoundly influence human-perceived temperature and the corresponding human thermal comfort, especially in urban areas with large population. This study analyzes the spatiotemporal changes in human-perceived temperatures in the North China Plain, represented by heat index (HI) in summer and wind chill temperature (WCT) in winter, and quantifies the effects of urbanization on temperature changes, based on the observational data of 56 meteorological stations during 1976–2016. The results show a significant warming trend, with human-perceived temperatures increasing faster than T. The warming trend in WCT is higher than that in HI, indicating more thermal discomfort in summer and more thermal comfort in winter. However, the warming trend moderately slows after 1996, partly due to the global surface warming hiatus. Urban areas experience stronger warming trends than non-urban areas, demonstrating the notable effects of urbanization. For the entire study area, urbanization and associated urban land expansion accelerate the increase in HI by 26% and the increase in WCT by 17%