Knowing the exact sampling depth of microwave radiometry is essential for quantifying the performance and appreciation of the applicability of satellite soil moisture products. We investigate in this ...study the sampling depth (δSM) of the L-band microwave emission under frozen and thawed soil conditions on the Tibetan Plateau. Two years of diurnal brightness temperature (TBp) measurements at a time interval of 30 min are collected by the ELBARA-III radiometer deployed at a Tibetan meadow site. Vertical profiles of soil temperature and volumetric liquid water content (θliq) are measured simultaneously at soil depths up to 1 m below the surface. The impact of the θliq measured at different depths on the microwave emission simulations is assessed using the τ-ω emission model, whereby the permittivity of frozen and thawed soil is estimated by the four-phase dielectric mixing model. It is found that: 1) the sampling depth for the effective temperature depends on the magnitude of θliq, and is estimated to be, on average, about 50 and 15 cm for the cold dry and wet warm period, respectively, because of the seasonality in θliq; 2) the δSM is determined at 2.5 cm for both frozen and thawed soil conditions during both cold and warm periods, which is shallower than the commonly used θliq measurement depth (i.e. 5 cm) adopted for the in-situ monitoring networks across the globe; 3) the TBp simulations performed with the θliq measurements taken at the estimated δSM of 2.5 cm result in lower unbiased root mean squared errors, about 14% (3.16 K) and 22% (3.36 K) for the horizontal and vertical polarizations respectively, in comparison to the simulations with the θliq measurements taken from 5 cm soil depth; and 4) the θliq retrieved with the single channel algorithm from the ELBARA-III measured vertically polarized TBp are in better agreement with the θliq measured at 2.5 cm than the one measured at 5 cm. These findings are crucial for developing strategies for the calibration/validation as well as the application of satellite based soil moisture products relying on the L-band radiometry.
•Sampling depth is about 2.5 cm for L-band radiometry of frozen and thawed soils.•Sampling depth for effective temperature depends on liquid water contents.•Sampling depth of liquid water content is smaller than that for effective temperature.•Emission simulation is improved with the liquid water content taken at sampling depth.•Retrievals of liquid water content are closest to these measured at a depth of 2.5 cm.
Active and passive microwave characteristics of diurnal soil freeze-thaw transitions and their relationships are crucial for developing retrieval algorithms of the soil liquid water content ...(<inline-formula> <tex-math notation="LaTeX">\theta _{\mathrm {liq}} </tex-math></inline-formula>) and freeze/thaw state, which, however, have been less explored. This study investigates these microwave characteristics and relationships via analysis of ground-based measurements of brightness temperature (<inline-formula> <tex-math notation="LaTeX">T_{B} </tex-math></inline-formula>) and backscattering coefficients (<inline-formula> <tex-math notation="LaTeX">\sigma ^{0} </tex-math></inline-formula>) in combination with simulations performed with the Tor Vergata discrete radiative transfer model. Both an L-band (1.4 GHz) radiometer ELBARA-III and a wide-band (1-10 GHz) scatterometer are installed in a seasonally frozen Tibetan meadow ecosystem to measure diurnal variations of <inline-formula> <tex-math notation="LaTeX">T_{B} </tex-math></inline-formula> and copolarized <inline-formula> <tex-math notation="LaTeX">\sigma ^{0} </tex-math></inline-formula> at both hh (<inline-formula> <tex-math notation="LaTeX">\sigma _{\mathrm {hh}}^{0} </tex-math></inline-formula>) and vv (<inline-formula> <tex-math notation="LaTeX">\sigma _{\mathrm {vv}}^{0} </tex-math></inline-formula>) polarizations. Analysis of measurements collected between December 2017 and March 2018 shows that 1) diurnal cycles are observed in both <inline-formula> <tex-math notation="LaTeX">T_{B} </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">\sigma ^{0} </tex-math></inline-formula> due to the change in surface <inline-formula> <tex-math notation="LaTeX">\theta _{\mathrm {liq}} </tex-math></inline-formula> caused by diurnal soil freeze-thaw transitions; 2) a negatively linear relationship is found between <inline-formula> <tex-math notation="LaTeX">e </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">\sigma ^{0} </tex-math></inline-formula> regardless of frequency, polarization combinations, and observation angles; 3) slopes (<inline-formula> <tex-math notation="LaTeX">\beta </tex-math></inline-formula>) of linearly fit equations between <inline-formula> <tex-math notation="LaTeX">e^{H} </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">\sigma _{\mathrm {hh}}^{0} </tex-math></inline-formula> decrease with increasing observation angles of ELBARA-III, while the ones between <inline-formula> <tex-math notation="LaTeX">e^{V} </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">\sigma _{\mathrm {vv}}^{\mathrm {0 {}}} </tex-math></inline-formula> increase with increasing observation angles; and 4) correlations between <inline-formula> <tex-math notation="LaTeX">e </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">\sigma ^{0} </tex-math></inline-formula> increase with decreasing microwave frequency of <inline-formula> <tex-math notation="LaTeX">\sigma ^{0} </tex-math></inline-formula> measurements and ELBARA-III observation angles, and magnitudes of diurnal <inline-formula> <tex-math notation="LaTeX">\sigma ^{0} </tex-math></inline-formula> cycles also increase with decreasing microwave frequency. Moreover, the calibrated Tor Vergata model shows capability to reproduce both diurnal <inline-formula> <tex-math notation="LaTeX">e </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">\sigma ^{\mathrm {0 {}}} </tex-math></inline-formula> variations as well as to quantify their relationships at different frequencies and observation angles.
Launched in January 2015, the National Aeronautics and Space Administration (NASA) Soil Moisture Active Passive (SMAP) observatory was designed to provide frequent global mapping of high-resolution ...soil moisture and freeze-thaw state every two to three days using a radar and a radiometer operating at L-band frequencies. Despite a hardware mishap that rendered the radar inoperable shortly after launch, the radiometer continues to operate nominally, returning more than two years of science data that have helped to improve existing hydrological applications and foster new ones.
Beginning in late 2016 the SMAP project launched a suite of new data products with the objective of recovering some high-resolution observation capability loss resulting from the radar malfunction. Among these new data products are the SMAP Enhanced Passive Soil Moisture Product that was released in December 2016, followed by the SMAP/Sentinel-1 Active-Passive Soil Moisture Product in April 2017.
This article covers the development and assessment of the SMAP Level 2 Enhanced Passive Soil Moisture Product (L2_SM_P_E). The product distinguishes itself from the current SMAP Level 2 Passive Soil Moisture Product (L2_SM_P) in that the soil moisture retrieval is posted on a 9km grid instead of a 36km grid. This is made possible by first applying the Backus-Gilbert optimal interpolation technique to the antenna temperature (TA) data in the original SMAP Level 1B Brightness Temperature Product to take advantage of the overlapped radiometer footprints on orbit. The resulting interpolated TA data then go through various correction/calibration procedures to become the SMAP Level 1C Enhanced Brightness Temperature Product (L1C_TB_E). The L1C_TB_E product, posted on a 9km grid, is then used as the primary input to the current operational SMAP baseline soil moisture retrieval algorithm to produce L2_SM_P_E as the final output. Images of the new product reveal enhanced visual features that are not apparent in the standard product. Based on in situ data from core validation sites and sparse networks representing different seasons and biomes all over the world, comparisons between L2_SM_P_E and in situ data were performed for the duration of April 1, 2015–October 30, 2016. It was found that the performance of the enhanced 9km L2_SM_P_E is equivalent to that of the standard 36km L2_SM_P, attaining a retrieval uncertainty below 0.040m3/m3 unbiased root-mean-square error (ubRMSE) and a correlation coefficient above 0.800. This assessment also affirmed that the Single Channel Algorithm using the V-polarized TB channel (SCA-V) delivered the best retrieval performance among the various algorithms implemented for L2_SM_P_E, a result similar to a previous assessment for L2_SM_P.
•SMAP enhanced passive product validation covered diversified spatial scales.•Product retrieval accuracy is found to be below 0.040m3/m3 with good correlation.•Single channel algorithm using v-polarized TB channel showed the best performance.•Descending 6:00am retrieval is more accurate than ascending 6:00pm retrieval.•First project-level publication on this new product
This is the first part of a study focusing on evaluating the performance of the Noah land surface model (LSM) in simulating surfacewater and energy budgets for the high-elevation source region of the ...Yellow River (SRYR). A comprehensive dataset is utilized that includes in situ micrometeorological and profile soil moisture and temperature measurements as well as laboratory soil property measurements of samples collected across the SRYR. Here, the simulation of soil water flow is investigated, while Part II concentrates on the surface heat flux and soil temperature simulations. Three augmentations are proposed: 1) to include the effect of organic matter on soil hydraulic parameterization via the additivity hypothesis, 2) to implement the saturated hydraulic conductivityK
sas an exponentially decaying function with soil depth, and 3) to modify the vertical root distribution to represent the Tibetan conditions characterized by an abundance of roots in the topsoil. The diffusivity form of Richards’ equation is further revised to allow for the simulation of soil water flow across soil layers with different hydraulic properties. Usage of organic matter for calculating the porosity and soil suction improves the agreement between the estimates and laboratory measurements, and the exponential function together with the Kozeny–Carman equation best describes the in situK
s. Through implementation of the modified hydraulic parameterization alone, the soil moisture underestimation in the upper soil layer under wet conditions is resolved, while the soil moisture profile dynamics are better captured by also including the modified root distribution.
This is the second part of a study on the assessment of the Noah land surface model (LSM) in simulating surface water and energy budgets in the high-elevation source region of the Yellow River. Here, ...there is a focus on turbulent heat fluxes and heat transport through the soil column during the monsoon season, whereas the first part of this study deals with the soil water flow. Four augmentations are studied for mitigating the overestimation of turbulent heat flux and underestimation of soil temperature measurements: 1) the muting effect of vegetation on the thermal heat conductivityκ
his removed from the transport of heat from the first to the second soil layer, 2) the exponential decay factorβ
vegimposed onκ
his calculated using the ratio of the leaf area index (LAI) over the green vegetation fraction (GVF), 3) Zilitinkevich’s empirical coefficientC
zilfor turbulent heat transport is computed as a function of the momentum roughness lengthz
0,m, and 4) the impact of organic matter is considered in the parameterization of the thermal heat properties. Although usage of organic matter for calculatingκ
himproves the correspondence between the estimates and laboratory measurements of heat conductivities, it is shown to have a relatively small impact on the Noah LSM performance even for large organic matter contents. In contrast, the removal of the muting effect of vegetation onκ
hand the parameterization ofβ
veggreatly enhances the soil temperature profile simulations, whereas turbulent heat flux and surface temperature computations mostly benefit from the modifiedC
zilformulation. Further, the nighttime surface temperature overestimation is resolved from a coupled land–atmosphere perspective.
Heart failure (HF) is a leading cause of mortality in the western world. Despite advances in the treatment of HF, like the use of angiotensin-converting enzyme (ACE) inhibitors, β-blockers, ...angiotensin receptor blockers (ARBs), mineralocorticoid receptor antagonists (MRAs), and implantable cardiac defibrillators, prognosis of HF patients remains poor. For clinicians dealing with HF patients, risk prediction in both acute, chronic, and new onset HF remains a challenge. Biomarkers might help in risk stratification and may guide the proper use of limited resources and therapy. Galectin-3 is an emerging biomarker which has been linked to tissue fibrosis, a hallmark in cardiac remodeling and HF. Galectin-3 can reliably be measured in the circulation, and several recent studies have shown the prognostic value of galectin-3 in acute and chronic HF, and its potential utility in the general population. The purpose of this review was to summarize the literature and explore the potential role of galectin-3 as a biomarker in HF.
We examine soil drying rates by comparing surface soil moisture observations from the NASA Soil Moisture Active Passive (SMAP) mission to those from networks of in situ probes upscaled to SMAP's ...sensing footprint. SMAP and upscaled in situ probes record different soil drying dynamics after rainfall. We modeled this process by fitting an exponential curve to 63 drydown events: the median SMAP drying timescale is 44% shorter and the magnitude of drying is 35% greater than in situ measurements. We also calculated drying rates between consecutive observations from 193 events. For 6 days after rainfall, soil moisture from SMAP dries at twice the rate of in situ measurements. Restricting in situ observations to times of SMAP observations does not change the drying timescale, magnitude, or rate. Therefore, observed differences are likely due to differences in sensing depths: SMAP measures shallower soil moisture than in situ probes, especially after rainfall.
Key Points
SMAP and networks of in situ probes observe soil drying after rainfall
SMAP observes soil drying to occur over a 44% shorter timescale than in situ
SMAP observes soil drying to occur at twice the rate as in situ
Previous studies have reported an association between ABO type blood group and cardiovascular (CV) events and outcomes. The precise mechanisms underpinning this striking observation remain unknown, ...although differences in von Willebrand factor (VWF) plasma levels have been proposed as an explanation. Recently, galectin-3 was identified as an endogenous ligand of VWF and red blood cells (RBCs) and, therefore, we aimed to explore the role of galectin-3 in different blood groups. Two in vitro assays were used to assess the binding capacity of galectin-3 to RBCs and VWF in different blood groups. Additionally, plasma levels of galectin-3 were measured in different blood groups in the Ludwigshafen Risk and Cardiovascular Health (LURIC) study (2571 patients hospitalized for coronary angiography) and validated in a community-based cohort of the Prevention of Renal and Vascular End-stage Disease (PREVEND) study (3552 participants). To determine the prognostic value of galectin-3 in different blood groups, logistic regression and cox regression models were used with all-cause mortality as the primary outcome. First, we demonstrated that galectin-3 has a higher binding capacity for RBCs and VWF in non-O blood groups, compared to blood group O. Additionally, LURIC patients with non-O blood groups had substantially lower plasma levels of galectin-3 (15.0, 14.9, and 14.0 μg/L in blood groups A, B, and AB, respectively, compared to 17.1 μg/L in blood group O,
< 0.0001). Finally, the independent prognostic value of galectin-3 for all-cause mortality showed a non-significant trend towards higher mortality in non-O blood groups. Although plasma galectin-3 levels are lower in non-O blood groups, the prognostic value of galectin-3 is also present in subjects with a non-O blood group. We conclude that physical interaction between galectin-3 and blood group epitopes may modulate galectin-3, which may affect its performance as a biomarker and its biological activity.
In this paper, we analyze the standardized anomalies of land surface temperature (LST) retrieved from the Special Sensor Microwave Imager (SSM/I) vertically polarized 37 GHz (
) brightness ...temperature over the Tibetan Plateau for the period 1987 to 2008. A radiative transfer model is used to derive LST from SSM/I
, which is calibrated and validated using time series of field measured soil surface temperatures. Additional Plateau-scale verification is performed with monthly LST products from the Moderate Resolution Imaging Spectroradiometer, the Noah land surface model and air temperature measured by Chinese Meteorological Administration. Trend analysis shows that the annual and monthly standardized anomalies are increasing at an averaged rate of 0.5 decade
− 1
. The highest positive trends are noted over the central part of the Plateau, which is on average 0.80 decade
− 1
with a maximum of 1.44 decade
− 1
. Conversely, a negative trend in the anomalies is found for the Taklamakan desert and the Himalayan foothills with a rate of −0.27 decade
− 1
and reaching a maximum of −1.4 decade
− 1
. In addition, we find that LST anomaly trends on the Plateau are seasonally dependent and increase with the elevation. These observed trends are in agreement with previous studies conducted with in-situ measurements, which demonstrates the use of long-term earth observation programmes for climate studies as has also been articulated in the 2007 IPCC report.
The Twente region in the east of the Netherlands has a network with twenty soil monitoring stations that has been utilized for validation of the Soil Moisture Active/Passive (SMAP) passive-only soil ...moisture products. Over the period from April 2015 until December 2018, seven stations covered by the SMAP reference pixels 15 have fairly complete data records. Spatially distributed soil moisture simulations with the Dutch national hydrological model have been utilized for the development of upscaling functions to translate the spatial mean of point measurements to the domain of the SMAP reference pixels. The native and upscaled spatial soil moisture means computed using the in-situ measurements have been adopted as references to assess the performance of the SMAP i) Single Channel Algorithm at Horizontal Polarization (SCA-H), ii) Single Channel Algorithm at Vertical Polarization (SCA-V), and iii) Dual Channel Algorithm (DCA) soil moisture estimates. In the case of the Twente network it was found that the SCA-V soil moisture retrieved SMAP observations collected in the afternoon had the best agreement with the native spatial mean leading to an unbiased Root Mean Squared Error (uRMSE) of 0.059 m3 m-3, whereas for the upscaled in-situ references primarily larger biases were found. These error levels are larger than the mission’s target accuracy of 0.04 m3 m-3, which can be attributed to large over- and underestimation errors (>0.08 m3 m-3) in particular at the end of dry spells and during freezing, respectively. The strong vertical dielectric gradients associated with rapid soil freezing and wetting causes the disparity in soil depth characterized by SMAP and in situ that leads to the large mismatches. Once filtered for frozen conditions and antecedent rainfall the uRMSE improves to 0.043 m3 m-3.
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