Soil moisture (SM) is critical for various hydro-meteorological applications. Land surface models (LSMs) can produce global spatio-temporal continuous SM estimates. Recently, NASA and ECMWF released ...GLDAS-2.1 and ERA5-Land datasets, respectively, which contain newly produced LSM-based global SM products, and these have not been thoroughly evaluated in China. To better understand the two products, we decomposed them into SM climatology (i.e., mean seasonal cycle) and SM anomaly (i.e., short-term variability) components and evaluated them separately in China. In particular, the evaluation was conducted considering ground-based SM observations obtained from 1411 stations and two remotely sensed SM products. The following key results were obtained: (a) In the SM climatology evaluation, ERA5-Land showed a larger bias in (semi-) humid areas (0.06 m
3
/m
3
on an average), while GLDAS-2.1 was generally unbiased. GLDAS-2.1 showed higher temporal precision (temporal mean R = 0.47 -) than ERA5-Land (temporal mean R = 0.17 -) in northern arid areas, while ERA5-Land exhibited better performance (temporal mean R = 0.64 -) than GLDAS-2.1 (temporal mean R = 0.34 -) in southern humid areas. (b) For the SM anomaly evaluation, ERA5-Land and GLDAS-2.1 performed similarly, and ERA5-Land (temporal mean R = 0.45 -) marginally outperformed GLDAS-2.1 (temporal mean R = 0.40 -). (c) For the raw SM, GLDAS-2.1 and ERA5-Land had higher temporal precision in the northern and southern areas, respectively, which are mostly determined by their SM climatology. Our findings highlight the important role of SM climatology and provide an important reference for improving the aforementioned SM products.
► A model for the performances of volumetric solar air receiver was developed. ► Sensitivity studies show the thermal non-equilibrium phenomena are distinct locally. ► The mean cell size has a ...dominant effect on the performances of solar air receiver. ► The solid thermal conductivity of absorber is not important to the air receiver. ► The desired temperature distribution of the absorber is realizable.
Ceramic foams are promising materials for the absorber of volumetric solar air receivers in concentrated solar thermal power (CSP) receivers. The macroscopic temperature distribution in the volumetric solar air receiver is crucial to guarantee that volumetric solar air receivers work steadily, safely and above all, efficiently. This study analyzes the temperature distribution of the fluid and solid phases in volumetric solar air receivers. The pressure drop in the ceramic foams and the interfacial heat transfer between the flowing fluid and solid are included in the model. The radiative heat transfers due to concentrated solar radiation absorption by the ceramic foam and the radiation transport in the media were modeled with the P
1 approximation. The energy fields of the fluid and solid phases were obtained using the local thermal non-equilibrium model (LTNE). Comparison of the macroscopic model with experimental results shows that the macroscopic model can be used to predict the performance of solar air receivers. Sensitivity studies were conducted to analyze the effects of velocity, porosity, mean cell size and the thermal conductivity of the solid phase on the temperature fields. The results illustrate that the thermal non-equilibrium phenomena are locally important, and the mean cell size has a dominant effect on the temperature field.
Porous ceramic foams are used to achieve high performance in solar heat recovery systems. Understanding the convective heat transfer between the air flow and the ceramic foam is of great importance ...when optimising the volumetric air receiver. In this work, the convective heat transfer was numerically studied. The present approach was designed to compute the local convective heat transfer coefficient between the air flow and a porous ceramic foam. For that purpose, the energy balance and the flow inside the porous ceramic foam were solved. In addition, a detailed geometry of the porous ceramic foam was considered. The ceramic foams were represented by idealised packed tetrakaidecahedron structures. The numerical simulations were based on the three dimensional Reynolds-averaged Navier–Stokes (RANS) equations. A sensitivity study on the heat transfer coefficient was conducted with the porosity, velocity and mean cell size as parameters. Based on the numerical simulation results, a correlation for the volumetric local convective heat transfer coefficient between air and ceramic foams was developed. The resulting correlation covers a wide range of porosities, velocities, cell sizes and temperatures. The correlation results were compared with experimental data from the literature, and the comparison shows good agreement. The correlation is intended to be used in the design of volumetric solar air receivers.
Martian mini‐magnetospheres contain whistler‐mode chorus waves potentially contributing to atmospheric escape, analogous to the Earth's inner magnetosphere. At Earth, the chorus waves have been found ...to originate from the near‐equatorial region spanning approximately 2% of the entire magnetic field line length. However, because of the lack of wave Poynting flux measurements, the Martian chorus source region remains unclear. By comparing the frequency dependence between observed wave power and modeled linear growth rates, we present the first attempt to explore the chorus wave source distribution along the Martian mini‐magnetospheric field lines. Our data‐to‐model comparisons support that these waves are not generated by a single source tightly confined near the magnetic strength minimal location but by intermittent or continuous sources spanning up to 40% of the entire field line length. These results imply that the Martian mini‐magnetospheres could have more active energy transfer processes mediated by whistler‐mode chorus waves than the expectation.
Plain Language Summary
Atmospheric escape is a critical process for the evolution of the surface habitability of terrestrial planets in our solar system or beyond. Analogous to the Earth's inner magnetosphere, the Martian mini‐magnetospheres formed by crustal magnetic fields contain whistler‐mode chorus waves which have the potential to contribute to atmospheric escape. However, because of the lack of wave Poynting flux measurements, where the Martian chorus waves are generated remains unclear. By comparing the frequency dependence between the observed wave power spectral densities and the modeled linear growth rates, we present the first attempt to explore the distribution of chorus wave sources along the magnetic field lines of the Martian mini‐magnetospheres. We show that these Martian chorus waves are generated by intermittent or continuous sources spanning up to 40% of the entire magnetic field line length, in contrast to the Earth's inner magnetospheric chorus waves with a single near‐equatorial source spanning approximately 2% of the entire field line length. These results imply that the Martian mini‐magnetospheres could have more active energy transfer processes mediated by whistler‐mode chorus waves than the expectation from analogy to the Earth's magnetosphere.
Key Points
Chorus wave sources are located by matching the frequency dependence between the modeled linear growth rates and the observed power
Martian mini‐magnetospheres contain continuous or intermittent wave sources spanning up to 40% of the entire magnetic field line length
Martian mini‐magnetospheres could have more active energy transfer processes mediated by chorus than the expectation
Magnetosonic waves inside and outside the plasmasphere differ statistically in occurrence rate, frequency, and intensity. How the density interface separates magnetosonic waves inside and outside the ...plasmasphere remains not fully understood. Here we report an experimental test made with the Van Allen Probes mission from the plasmaspheric plume through the low‐density channel to the plasmaspheric core. Our linear instability analysis and two‐dimensional full‐wave modeling support that the magnetosonic waves propagate from elsewhere to the channel, undergo reflection and transmission at the flanking plasmaspheric density interfaces and eventually exhibit drastic differences in intensity and frequency coverage between neighboring regions. Such a mesoscale (tens of wavelength wide) interface with a strong refractive index gradient allows the transformation of incident waves to surface waves and consequently filters waves in both frequency and orientation. This unexpected filtering pattern could commonly occur at the plasmaspheric boundary and eventually affect the global distribution of magnetosonic waves.
Plain Language Summary
Magnetosonic waves play an important role in the coupling between the ionosphere and magnetosphere and the evolution of the magnetospheric radiation environment. Previous global surveys have shown that magnetosonic waves inside and outside the plasmasphere differ significantly in occurrence rate, frequency, and intensity. In fact, magnetosonic waves are not confined near the source region but are able to propagate over a broad range of radial distances and magnetic local times. An obvious question arises as to how the density interface separates magnetosonic waves inside and outside the plasmasphere. Previous modeling and analysis suggested that the mesoscale (tens of wavelengths) density interface allowed the free penetration of magnetosonic waves from outside to inside the plasmasphere. In contrast, our data and modeling here show that such a mesoscale interface with a strong refractive index gradient allows the transformation of incident waves to surface waves and consequently filters waves in both frequency and incident angle. This unexpected filtering pattern could commonly occur at the plasmaspheric boundary and eventually affect the global distribution of magnetosonic waves.
Key Points
A tens of wavelength wide plasmaspheric density interface separated the magnetosonic waves with differing intensity and frequency coverage
The local proton Bernstein instabilities are unable to explain the drastic differences between magnetosonic waves in neighboring regions
The mesoscale plasmaspheric density interfaces can filter the inward penetrating magnetosonic waves in both frequency and incident angle
► A coupled transient model for volumetric solar air receiver was developed. ► Under sudden heat flux changes, transient behaviors of volumetric solar air receiver are studied. ► Volumetric solar air ...receiver’s reaction time to heat flux step is about 30–70s. ► Volumetric solar air receiver reacts to heat flux changes smoothly.
Ceramic foam is a promising material for the absorber of volumetric solar air receiver in concentrated solar thermal power (CSP) plant. The transient behaviors of volumetric solar air receiver are crucial to the receiver’s controllability, and to some extent, the plant’s safety. This study numerically analyzes the transient behaviors of volumetric solar air receiver under various working conditions. A fully coupled transientmodel of the volumetric solar air receiver is developed in this paper. The pressure drop of the absorber, the interfacial heat transfer between the flowing fluid and solid, and the radiative heat transfer due to concentrated solar radiation absorption by ceramic foam and the radiation transport inside the media were included together in this transientmodel. In addition, the temperature fields of the fluid and solid phases were obtained by using the local thermal non-equilibrium model. A comparison of the computed results with experimental data shows that this coupled transient model can be used to predict the performance of volumetric solar air receiver. Based on this model, the transient behaviors of the solar air receiver under a sudden heat flux, a sudden loss of heat flux, and a step change of heat flux were studied. The results of this study are very helpful in designing and controlling volumetric solar air receivers.
•Response of hydrological drought to large-scale climate index was revealed.•The drought character was greatly influenced by the reservoir operation.•The delayed effect of hydrological drought on ...vegetation cover was investigated.
The Xijiang River is known as the Golden Watercourse because of its role in the development of the Pearl River Delta Regional Economic System in China, which was made possible by its abundant water resources. At present, the hydrological regime of the Xijiang River has now become complicated, the water shortages and successive droughts pose a threat to regional economic development. However, the complexity of hydroclimatological processes with emphasizes on drought has not been comprehended. In order to effectively predict and develop the adaptation strategies to cope with the water scarcity damage caused by hydrological droughts, it is essential to thoroughly analyze the relationship between hydrological droughts and pre/post-dependent hydroclimatological factors. To accomplish this, the extreme-point symmetric mode decomposition method (ESMD) was utilized to reveal the periodic variation in hydrological droughts that is characterized by the Standardized Drought Index (SDI). In addition, the cross-wavelet transform method was applied to investigate the correlation between large-scale climate indices and drought. The results showed that hydrological drought had the most significant response to spring ENSO (El Niño-Southern Oscillation), and the response lags in sub-basins were mostly 8–9months except that in Yujiang River were mainly 5 or 8months. Signal reservoir operation in the Yujiang River reduced drought severity by 52–95.8% from January to April over the 2003–2014 time period. Similarly, the cascade reservoir alleviated winter and spring droughts in the Hongshuihe River Basin. However, autumn drought was aggravated with severity increased by 41.9% in September and by 160.9% in October, so that the land surface models without considering human intervention must be used with caution in the hydrological simulation. The response lags of the VCI (Vegetation Condition Index) to hydrological drought were different in the sub-basins. The response lag for the Hongshuihe, Yujiang, and Liujiang River Basins were mostly 0–4months, 0–1months, and 2–3months, respectively, but there was no obvious regular change pattern in the Guijiang River Basin.
Prior to their application in a land surface data assimilation (DA) system, remotely sensed (RS) soil moisture (SM) products are typically rescaled to remove systematic differences with respect to ...comparable SM estimates obtained from a land surface model (LSM). This preprocessing of RS SM data—commonly referred to as bias correction—implicitly discards spatial information present in the RS SM retrievals. Here, based on dense SM network measurements obtained within the Huai River Basin of China, we demonstrate that L‐band Soil Moisture Active Passive (SMAP) L3 surface SM retrievals provide a better representation of spatial variability in time‐averaged SM fields than a LSM—suggesting that, as typically applied, bias correction is neglecting important spatial information present in RS SM products. To maximally use RS information, we propose an alternative bias correction approach for SM DA that provides the benefits of traditional rescaling while also improving modeled SM spatial patterns. Specifically, the regional mean of SMAP SM is first corrected using modeled SM of the Variable Infiltration Capacity (VIC) model. Then, two key VIC soil parameters (EXPT and BULKD) are calibrated to match the relative subregional spatial variability captured by the SMAP SM product. Results show that our model calibration method successfully improves VIC SM spatial patterns and pixel‐wise time series. Furthermore, these SM improvements translate into enhanced VIC streamflow estimates. Overall, results suggest that the proposed bias correction framework can improve current land surface DA systems by maximally utilizing spatial information contained in RS SM products.
Key Points
Spatial information contained in the SMAP L3 SM product is used for VIC model calibration
The model calibration improves VIC SM spatial patterns for the surface and second soil layers
The model calibration also enhances VIC streamflow estimates
Obese individuals are apt to develop Stanford A acute aortic dissection (AAD) complicated with acute lung injury (ALI), but the mechanism is still not well defined. We aim to investigate whether ...oxidative stress and inflammatory are involved in the aortic dissection lung injury caused by obesity.Seventy-nine patients were categorized into AAD with obesity group (n = 17) and AAD without obesity group (n = 62) according to body mass index (BMI). Inflammatory reactions including interleukin 1β (IL-1β), tumor necrosis factor-α (TNF-α), IL-6, C-reactive protein (CRP) and white blood cell (WBC) count, and oxidative stress including malondialdehyde (MDA), superoxide dismutase were determined using enzyme-linked immunosorbent assays and chemiluminescence. All the patients received ascending aorta replacement combined with total arch replacement and stented elephant trunk. The postoperative complications were recorded.The incidence of preoperative hypoxemia (94.1% vs 35.5%, P < .01) and postoperative ALI (88.2% vs 40.3%, P < .01) in obese patients was significantly higher than that in non-obese patients. Besides, the ICU stay (119.2 ± 59.2 vs 87.8 ± 31.2 h, P < .01) and hospitalization duration (18.8 ± 8.5 vs 14.3 ± 8.1d, P = .048) were increased in the obese patients with AAD. The expression of IL-1β, TNF-α, IL-6, CRP, and WBC was remarkably increased (P < .01) in obese group compared with non-obese group.Oxidative stress and inflammatory response may be involved in the process of ALI of aortic dissection caused by obesity, which provides new ideas for the treatment of ALI of the aortic dissection.
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