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The Gengma-Lancang-Menghai seismic belt, the southernmost part of the North-South seismic belt, is controlled by four active faults: the Nantinghe fault (NTHF), the Sanjianshan fault (SJSF), the Hanmuba-Lancang fault (HMB-LCF), and the Heihe fault (HHF), from northwest to southeast. However, the tectonic activity of the faults in the Gengma-Lancang-Menghai seismic belt has not been fully studied yet. In the present work, we conducted tectonic geomorphic indices to analyze the relative tectonic activity along the faults in the seismic belt based on the digital elevation model. We interpreted asymmetric factor, index of drainage basin shape, hypsometric integral, normalized stream-length gradient, valley floor-to-width to height ratio, and longitudinal profiles to show that the relative tectonic activity is higher in the north and lower in the south, and is strong in the region from Shanjia to Huimin in the center of the seismic belt. [ABSTRACT FROM AUTHOR]

The closure time of the Jinshajiang Ocean (a branch ocean of the Paleo-Tethys) has been widely debated due to the complex structure and strong deformation of the northern-central Tibetan Plateau. In this paper, the U-Pb-Hf isotope compositions of detrital zircons from Tongtian River sand sediments from the northern-central Tibetan Plateau were analyzed via laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The U Pb ages of the detrital zircons from Tongtian River sand sediments were distributed in six major groups: 2685–2346 Ma, 2035–1676 Ma, 1220–580 Ma, 544–407 Ma, 297–157 Ma, and 46–20 Ma. The ε Hf (t) values (range from −30 to +19) of the detrital zircons varied within a wide range from negative to positive, indicating that the zircons were sourced from diverse host magmas. The 46–20 Ma zircons and their Hf isotope compositions reveal that the far-field effect of the Cenozoic India-Eurasia plate collision triggered reworking of the Neoproterozoic basement of the North Qiangtang terrane. The U-Pb-Hf isotope compositions of these detrital zircons indicate that the Tongtian River sand sediments are composed of a mixture of materials from the Bayan Har-Songpan Ganzi terrane and the North Qiangtang terrane, with a contribution ratio of 3:7. The U Pb ages and Hf isotope compositions of the zircons from the Tongtian River sediments and regional igneous rocks suggest that the ε Hf (t) values of the Permian zircons are predominantly positive while those of the Triassic, especially the Late Triassic, are negative. This marked shift most likely indicates that the closure of the Jinshajiang Ocean occurred by at least the Late Triassic. [Display omitted] • Fluvial sediments in the Tongtian River are contributed by the BST and the NQT in a ratio of 3:7. • Far-field effect of the India-Eurasia plate collision triggered the reworking of the NQT basement. • The closure time of the Jinshajiang Ocean occurred at least in the Late Triassic. [ABSTRACT FROM AUTHOR]

This study assesses the performance of temperature extremes over China in two regional climate models (RCMs), RegCM4 and WRF, driven by the ECMWF's 20th century reanalysis. Based on the advice of the Expert Team on Climate Change Detection and Indices (ETCCDI), 12 extreme temperature indices (i.e., TXx, TXn, TNx, TNn, TX90p, TN90p, TX10p, TN10p WSDI, ID, FD, and CSDI) are derived from the simulations of two RCMs and compared with those from the daily station-based observational data for the period 1981-2010. Overall, the two RCMs demonstrate satisfactory capability in representing the spatiotemporal distribution of the extreme indices over most regions. RegCM performs better than WRF in reproducing the mean temperature extremes, especially over the Tibetan Plateau (TP). Moreover, both models capture well the decreasing trends in ID, FD, CSDI, TX10p, and TN10p, and the increasing trends in TXx, TXn, TNx, TNn, WSDI, TX90p, and TN90p, over China. Compared with observation, RegCM tends to underestimate the trends of temperature extremes, while WRF tends to overestimate them over the TP. For instance, the linear trends of TXx over the TP from observation, RegCM, and WRF are 0.53°C (10 yr)−1, 0.44°C (10 yr)−1, and 0.75°C (10 yr)−1, respectively. However, WRF performs better than RegCM in reproducing the interannual variability of the extreme-temperature indices. Our findings are helpful towards improving our understanding of the physical realism of RCMs in terms of different time scales, thus enabling us in future work to address the sources of model biases. [ABSTRACT FROM AUTHOR]

Concentrations of organic carbon (OC), elemental carbon (EC), selected trace elements and water-soluble (WS) ions were determined for samples collected from August 2004 to February 2005 to assess the aerosol background at two remote sites in China. The OC and EC concentrations in PM10 from near the Tibetan Plateau at Zhuzhang (ZUZ) were comparable with other background sites, averaging 3.1 and 0.34 μg m−3, respectively, with no pronounced seasonality. At Akdala (AKD) on northern margin of the Zhungaer Basin, the average concentrations were similar (mean OC = 2.9 μg m−3 and EC = 0.35 μg m−3), but the concentrations were higher in winter. The aerosol mass at both sites was dominated by OC and SO42−, but a stronger contribution from soil dust was observed at AKD. At ZUZ, NO3− showed a unique weather-related fluctuation in PM10 with a periodicity of ∼1 week. Anthropogenic sources in the Sichuan Basin and southeastern Yunnan Province evidently influence ZUZ in summer and autumn while pollutants from Russia and the China–Mongolia border affect AKD nearly all year. The identification of these upwind sources demonstrates that transboundary transport needs to be taken into account when assessing air quality in remote parts of China. [ABSTRACT FROM AUTHOR]

The diurnal cycle of convection and precipitation is an important atmospheric feature. It also poses a great challenge to global numerical atmospheric modeling. Over continental East Asia, most global models cannot well capture the nocturnal and early morning peaks of summer rainfall. This problem may lead to dry biases and limit the modeling skills. This study investigates this problem using a global multiscale modeling framework (Super-Parameterized CAM5; SPCAM5). The nocturnal and early morning peaks, which are almost absent in CAM5 and a coarser-resolution SPCAM5, can be successfully captured by SPCAM5 with a moderate increase in the horizontal resolution. On the lee side of the Tibetan Plateau, SPCAM5 generates robust eastward propagating rainfall signals, which correspond to the moving convective systems, as revealed by the heating and drying profiles. Over the eastern plain of China, the early morning peaks become more evident, corresponding to a stratiform-type heating structure in the midlevel. A sensitivity experiment with altered grid-scale forcing also suggests the important preconditioning role of the vertical moisture advection in regulating the early morning peaks. These results highlight the added value of representing multiscale processes to the successful simulation of the diurnal cycle over continental East Asia. [ABSTRACT FROM AUTHOR]