Geology topics

F. Chen

Publications and source records attributed to F. Chen.

4 recordsLinked to original sources

USGS2023

CONUS404: The NCAR-USGS 4-km long-term regional hydroclimate reanalysis over the CONUS

A unique, high-resolution, hydroclimate reanalysis, 40-plus-year (October 1979–September 2021), 4 km (named as CONUS404), has been created using the Weather Research and Forecasting Model by dynamically downscaling of the fifth-generation European Centre for Medium-Range Weather Forecasts (ECMWF) atmospheric reanalysis of the global climate dataset (ERA5) over the conterminous United States. The paper describes the approach for generating the dataset, provides an initial evaluation, including biases, and indicates how interested users can access the data. The motivation for creating this National Center for Atmospheric Research (NCAR)–U.S. Geological Survey (USGS) collaborative dataset is to provide research and end-user communities with a high-resolution, self-consistent, long-term, continental-scale hydroclimate dataset appropriate for forcing hydrological models and conducting hydroclimate scientific analyses over the conterminous United States. The data are archived and accessible on the USGS Black Pearl tape system and on the NCAR supercomputer Campaign storage system.

Continental United States↗

USGS2010

Distribution and trends in reference evapotranspiration in the North China plain

The distribution and trends in reference evapotranspiration (ET(o)) are extremely important to water resources planning for agriculture, and it is widely believed that rates of ET(o) will increase with global warming. This is a big concern in China, where water deficits are common in the North China Plain (NCP). In this study, Penman-Monteith reference evapotranspiration at 26 meteorological stations during 1961-2006 in and around the NCP was calculated. The temporal variations and spatial distribution of ET(o) were analyzed and the causes for the variations were discussed. The results showed that: (1) the NCP was divided into two climatic regions based on aridity values: a semiarid region that accounts for 69% of the area and subhumid regions that made of the remaining area; (2) over the entire NCP, the highest annual ET(o) occurred in the central and western areas and the lowest total ET(o) was observed in the east. Comparing the mean monthly ET(o) and annual ET(o) distributions, the high ET(o) values from May through July mainly determined the annual ET(o) distribution; (3) for the whole NCP, annual ET(o) showed a statistically significant decrease of 11.92 mm/decade over the 46 years of data collection in the NCP or approximately a 5% total decrease compared to the ET(o) values in 1961; (4) to determine which variable has the greatest effect on the decrease in ET(o), decadal changes were observed for daily values of maximum air temperature (+0.16 degrees C), minimum air temperature (+0.35 degrees C), net radiation (-0.13 MJ m(-2)), and mean wind speed (-0.09 m s(-1)). These results indicate that the decreasing net radiation and wind speed had a bigger impact on ET(o) rates than the increases observed by the maximum and minimum temperatures.

North China Plain↗

USGS2004

Assembly of the Pamirs: Age and origin of magmatic belts from the southern Tien Shan to the southern Pamirs and their relation to Tibet

Magmatic rocks and depositional setting of associated volcaniclastic strata along a north-south traverse spanning the southern Tien Shan and eastern Pamirs of Kyrgyzstan and Tajikistan constrain the tectonics of the Pamirs and Tibet. The northern Pamirs and northwestern Tibet contain the north facing Kunlun suture, the south facing Jinsha suture, and the intervening Carboniferous to Triassic Karakul-Mazar subduction accretion system; the latter is correlated with the Songpan-Garze-Hoh Xi system of Tibet. The Kunlun arc is a composite early Paleozoic to late Paleozoic-Triassic arc. Arc formation in the Pamirs is characterized by ???370-320 Ma volcanism that probably continued until the Triassic. The cryptic Tanymas suture of the southern northern Pamirs is part of the Jinsha suture. A massive ??????227 Ma batholith stitches the Karakul-Mazar complex in the Pamirs. There are striking similarities between the Qiangtang block in the Pamirs and Tibet. Like Tibet, the regional structure of the Pamirs is an anticlinorium that includes the Muskol and Sares domes. Like Tibet, the metamorphic rocks in these domes are equivalents to the Karakul-Mazar-Songpan-Garze system. Granitoids intruding the Qiangtang block yield ???200-230 Ma ages in the Pamirs and in central Tibet. The stratigraphy of the eastern Pshart area in the Pamirs is similar to the Bangong-Nujiang suture zone in the Amdo region of eastern central Tibet, but a Triassic ocean basin sequence is preserved in the Pamirs. Arc-type granitoids that intruded into the eastern Pshart oceanic-basin-arc sequence (???190-160 Ma) and granitoids that cut the southern Qiangtang block (???170-160 Ma) constitute the Rushan-Pshart arc. Cretaceous plutons that intruded the central and southern Pamirs record a long-lasting magmatic history. Their zircons and those from late Miocene xenoliths show that the most distinct magmatic events were Cambro-Ordovician (???410-575 Ma), Triassic (???210-250 Ma; likely due to subduction along the Jinsha suture), Middle Jurassic (???147-195 Ma; subduction along Rushan-Pshart suture), and mainly Cretaceous. Middle and Late Cretaceous magmatism may reflect arc activity in Asia prior to the accretion of the Karakoram block and flat-slab subduction along the Shyok suture north of the Kohistan-Ladakh arc, respectively. Before India and Asia collided, the Pamir region from the Indus-Yarlung to the Jinsha suture was an Andean-style plate margin. Our analysis suggests a relatively simple crustal structure for the Pamirs and Tibet. From the Kunlun arc in the north to the southern Qiangtang block in the south the Pamirs and Tibet likely have a dominantly sedimentary crust, characterized by Karakul-Mazar-Songpan-Garze accretionary wedge rocks. The crust south of the southern Qiangtang block is likely of granodioritic composition, reflecting long-lived subduction, arc formation, and Cretaceous-Cenozoic underthrusting. Copyright 2004 by the American Geophysical Union.

Tectonics↗

USGS1997

Cabauw experimental results from the Project for Intercomparison of Land-Surface Parameterization Schemes

In the Project for Intercomparison of Land-Surface Parameterization Schemes phase 2a experiment, meteorological data for the year 1987 from Cabauw, the Netherlands, were used as inputs to 23 land-surface flux schemes designed for use in climate and weather models. Schemes were evaluated by comparing their outputs with long-term measurements of surface sensible heat fluxes into the atmosphere and the ground, and of upward longwave radiation and total net radiative fluxes, and also comparing them with latent heat fluxes derived from a surface energy balance. Tuning of schemes by use of the observed flux data was not permitted. On an annual basis, the predicted surface radiative temperature exhibits a range of 2 K across schemes, consistent with the range of about 10 W m -2 in predicted surface net radiation. Most modeled values of monthly net radiation differ from the observations by less than the estimated maximum monthly observational error (±10 W m -2 ). However, modeled radiative surface temperature appears to have a systematic positive bias in most schemes; this might be explained by an error in assumed emissivity and by models' neglect of canopy thermal heterogeneity. Annual means of sensible and latent heat fluxes, into which net radiation is partitioned, have ranges across schemes of 30 W m -2 and 25 W m -2 , respectively. Annual totals of evapotranspiration and runoff, into which the precipitation is partitioned, both have ranges of 315 mm. These ranges in annual heat and water fluxes were approximately halved upon exclusion of the three schemes that have no stomatal resistance under non-water-stressed conditions. Many schemes tend to underestimate latent heat flux and overestimate sensible heat flux in summer, with a reverse tendency in winter. For six schemes, root-mean-square deviations of predictions from monthly observations are less than the estimated upper bounds on observation errors (5 W m -2 for sensible heat flux and 10 W m -2 for latent heat flux). Actual runoff at the site is believed to be dominated by vertical drainage to groundwater, but several schemes produced significant amounts of runoff as overland flow or interflow. There is a range across schemes of 184 mm (40% of total pore volume) in the simulated annual mean root-zone soil moisture. Unfortunately, no measurements of soil moisture were available for model evaluation. A theoretical analysis suggested that differences in boundary conditions used in various schemes are not sufficient to explain the large variance in soil moisture. However, many of the extreme values of soil moisture could be explained in terms of the particulars of experimental setup or excessive evapotranspiration.

Journal of Climate↗