scholarly journals Soil moisture active and passive microwave products: intercomparison and evaluation over a Sahelian site

2009 ◽  
Vol 6 (4) ◽  
pp. 5303-5339 ◽  
Author(s):  
C. Gruhier ◽  
P. de Rosnay ◽  
S. Hasenauer ◽  
T. Holmes ◽  
R. de Jeu ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Temporal Variations ◽  
Signal Frequency ◽  
Convective Rainfall ◽  
Ground Station ◽  
Multidisciplinary Analysis ◽  
Good Consistency ◽  
Rainfall Occurrences ◽  
Meso Scale ◽  
Good Agreement

Abstract. This paper presents a comparison and an evaluation of five soil moisture products based on satellite-based passive and active microwave measurements. Products are evaluated for 2005–2006 against ground measurements obtained from the soil moisture network deployed in Mali (Sahel) in the framework of the African Monsoon Multidisciplinary Analysis project. It is shown that the accuracy of the soil moisture products is sensitive to the retrieval approach as well as to the sensor type (active or passive) and to the signal frequency (from 5.6 GHz to 18.8 GHz). The spatial patterns of surface soil moisture are compared between the different products at meso-scale (14.5° N–17.5° N and 2° W–1° W). A general good consistency between the different satellite soil moisture products is shown in terms of meso-scale spatial distribution, in particular after convective rainfall occurrences. Soil moisture values provided by the different products are compared to ground measurements time series. Although soil moisture products obtained from satellite generally over-estimate soil moisture values during the dry season, most of them capture soil moisture temporal variations in good agreement with ground station measurements.

scholarly journals Soil moisture active and passive microwave products: intercomparison and evaluation over a Sahelian site

2010 ◽  
Vol 14 (1) ◽  
pp. 141-156 ◽  
Author(s):  
C. Gruhier ◽  
P. de Rosnay ◽  
S. Hasenauer ◽  
T. Holmes ◽  
R. de Jeu ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Temporal Variations ◽  
Signal Frequency ◽  
Ground Station ◽  
Multidisciplinary Analysis ◽  
Ground Measurement ◽  
Good Consistency ◽  
Rainfall Occurrences ◽  
Meso Scale ◽  
Good Agreement

Abstract. This paper presents a comparison and an evaluation of five soil moisture products based on satellite-based passive and active microwave measurements. Products are evaluated for 2005–2006 against ground measurements obtained from the soil moisture network deployed in Mali (Sahel) in the framework of the African Monsoon Multidisciplinary Analysis project. It is shown that the accuracy of the soil moisture products is sensitive to the retrieval approach as well as to the sensor type (active or passive) and to the signal frequency (from 5.6 GHz to 18.8 GHz). The spatial patterns of surface soil moisture are compared between the different products at meso-scale (14.5° N–17.5° N and 2° W–1° W). A general good consistency between the different satellite soil moisture products is shown in terms of meso-scale spatial distribution, in particular after convective rainfall occurrences. Comparison to ground measurement shows that although soil moisture products obtained from satellite generally over-estimate soil moisture values during the dry season, most of them capture soil moisture temporal variations in good agreement with ground station measurements.

scholarly journals Modelling Soil Moisture in Hyper-Arid Conditions

2021 ◽  
Author(s):  
Yaping Shao ◽  
Klaus Fraedrich ◽  
Masahide Ishizuka
Keyword(s):  
Soil Moisture ◽  
Land Surface ◽  
Land Surface Model ◽  
Vapour Phase ◽  
Temporal Variations ◽  
Surface Model ◽  
Arid Conditions ◽  
Surface Models ◽  
Soil Interface ◽  
Good Agreement

AbstractIn most land-surface models, the evolution of soil moisture is governed by soil-hydraulic processes. In hyper-arid soils, these processes break down, but soil moisture continues to show clear temporal variations, suggesting that other processes may be at work. We hypothesize that moisture in such soils varies due to evaporation in the soil and to vapour fluxes at the air–soil interface. To test this, we include vapour exchange between the air and soil in a land-surface model, apply the model to a desert site, and compare the simulated and observed soil moisture. The good agreement between the simulations and observations confirms our hypothesis. Using the model results, we examine the interactions between the soil-moisture and soil-vapour phases and influences of the soil-vapour phase on the surface energy balance.

scholarly journals Evaluation of Spatial and Temporal Performances of ERA-Interim Precipitation and Temperature in Mainland China

2018 ◽  
Vol 31 (11) ◽  
pp. 4347-4365 ◽  
Author(s):  
Zhengjia Liu ◽  
Yansui Liu ◽  
Sisi Wang ◽  
Xiujing Yang ◽  
Lunche Wang ◽  
...  
Keyword(s):  
Mainland China ◽  
Skill Score ◽  
Spatial And Temporal Patterns ◽  
West China ◽  
Ground Station ◽  
Lower Elevation ◽  
Good Consistency ◽  
Precipitation And Temperature ◽  
Good Agreement

Abstract ERA-Interim has been widely considered as a valid proxy for observations at global and regional scales. However, the verifications of ERA-Interim precipitation and temperature in mainland China have been rarely conducted, especially in the spatial and long-term performances. Therefore, in this study, we employed the interpolated ground station (STA) data to evaluate the spatial and temporal patterns and trends of ERA-Interim precipitation and temperature during 1980–2012. The results showed that relatively weaker performances were observed in ERA-Interim precipitation, with the skill score (S index) ranging from 0.41 to 0.50. Interannual ERA-Interim precipitation presented comparable trends with STA precipitation at the annual and seasonal scales. Spatial patterns of empirical orthogonal function (EOF) modes and corresponding principal components were evidently different between annual ERA-Interim and STA precipitation. For temperature, annual and seasonal patterns of ERA-Interim data were in good consistency with those of STA over China with the S index ranging from 0.59 to 0.70. Yet interannual STA temperature recorded stronger warming trends (from 0.37 K decade−1 of wintertime to 0.53 K decade−1 of springtime) at the annual and seasonal scales compared to corresponding periods for ERA-Interim temperature (from 0.03 K decade−1 of wintertime to 0.25 K decade−1 of summertime). Overall, ERA-Interim precipitation and temperature had good agreement with STA data in east China with lower elevation (<1000 m above sea level), but good agreements were not observed in west China with higher elevation. The findings suggest that caution should be paid when using ERA-Interim precipitation and temperature in areas with complex orography.

scholarly journals Multilayer Soil Moisture Mapping at a Regional Scale from Multisource Data via a Machine Learning Method

2019 ◽  
Vol 11 (3) ◽  
pp. 284 ◽  
Author(s):  
Linglin Zeng ◽  
Shun Hu ◽  
Daxiang Xiang ◽  
Xiang Zhang ◽  
Deren Li ◽  
...  
Keyword(s):  
Machine Learning ◽  
Soil Moisture ◽  
Regional Scale ◽  
Remotely Sensed ◽  
Temporal Variations ◽  
Training Data ◽  
Estimation Accuracy ◽  
Learning Approaches ◽  
Remotely Sensed Data ◽  
Deep Soil

Soil moisture mapping at a regional scale is commonplace since these data are required in many applications, such as hydrological and agricultural analyses. The use of remotely sensed data for the estimation of deep soil moisture at a regional scale has received far less emphasis. The objective of this study was to map the 500-m, 8-day average and daily soil moisture at different soil depths in Oklahoma from remotely sensed and ground-measured data using the random forest (RF) method, which is one of the machine-learning approaches. In order to investigate the estimation accuracy of the RF method at both a spatial and a temporal scale, two independent soil moisture estimation experiments were conducted using data from 2010 to 2014: a year-to-year experiment (with a root mean square error (RMSE) ranging from 0.038 to 0.050 m3/m3) and a station-to-station experiment (with an RMSE ranging from 0.044 to 0.057 m3/m3). Then, the data requirements, importance factors, and spatial and temporal variations in estimation accuracy were discussed based on the results using the training data selected by iterated random sampling. The highly accurate estimations of both the surface and the deep soil moisture for the study area reveal the potential of RF methods when mapping soil moisture at a regional scale, especially when considering the high heterogeneity of land-cover types and topography in the study area.

scholarly journals On the robustness of emptying filling boxes to sudden changes in the wind

2019 ◽  
Vol 868 ◽  
Author(s):  
John Craske ◽  
Graham O. Hughes
Keyword(s):  
Thermal Stratification ◽  
Temporal Variations ◽  
Transient Dynamics ◽  
Upper And Lower Bounds ◽  
Marginal Stability ◽  
Confined Space ◽  
Forward Displacement ◽  
Previous Formulation ◽  
Instantaneous Increase ◽  
Good Agreement

We determine the smallest instantaneous increase in the strength of an opposing wind that is necessary to permanently reverse the forward displacement flow that is driven by a two-layer thermal stratification. With an interpretation in terms of the flow’s energetics, the results clarify why the ventilation of a confined space with a stably stratified buoyancy field is less susceptible to being permanently reversed by the wind than the ventilation of a space with a uniform buoyancy field. For large opposing wind strengths we derive analytical upper and lower bounds for the system’s marginal stability, which exhibit a good agreement with the exact solution, even for modest opposing wind strengths. The work extends a previous formulation of the problem (Lishman & Woods, Build. Environ., vol. 44 (4), 2009, pp. 666–673) by accounting for the transient dynamics and energetics associated with the homogenisation of the interior, which prove to play a significant role in buffering temporal variations in the wind.

scholarly journals Effects of two typical revegetation methods on soil moisture in the semi-arid Loess Plateau, China

2019 ◽  
Vol 50 (5) ◽  
pp. 1453-1462
Author(s):  
Qian Zhao ◽  
Lei Yang ◽  
Xin Wang ◽  
Runcheng Bi ◽  
Qindi Zhang
Keyword(s):  
Soil Moisture ◽  
Loess Plateau ◽  
Temporal Variations ◽  
Chinese Loess Plateau ◽  
Deep Soil ◽  
Chinese Loess ◽  
Soil Desiccation ◽  
Native Grasslands ◽  
First Choice ◽  
Natural Revegetation

Abstract Understanding the effects of vegetation on soil moisture is vital to the ecosystem restoration in water-restricted areas. For this study, the effects of introduced revegetation and natural revegetation on soil water (0–1.8 m) were investigated in the Chinese Loess Plateau, which was based on an in situ vegetation removal experiment and two years of soil moisture monitoring. The results indicated that under introduced revegetation, pasture grassland had lower soil moisture but higher temporal variations over the growing season. Compared with abandoned farmlands and native grasslands under natural revegetation, pasture grasslands revealed greater negative effects on deep soil moisture (1–1.8 m), which was difficult to recover following soil desiccation. In contrast, for abandoned farmlands and native grasslands, the surface soil moisture (0–0.4 m) was mainly impacted, which was easily replenished through rainfall events. These outcomes implied that natural revegetation, rather than introduced revegetation, should be the first choice in water-limited regions toward the rehabilitation of degraded ecosystems.

scholarly journals EARLINET evaluation of the CATS L2 aerosol backscatter coefficient product

2019 ◽  
Author(s):  
Emmanouil Proestakis ◽  
Vassilis Amiridis ◽  
Eleni Marinou ◽  
Ioannis Binietoglou ◽  
Albert Ansmann ◽  
...  
Keyword(s):  
Space Station ◽  
Backscatter Coefficient ◽  
Backscatter Signal ◽  
Evaluation Activity ◽  
Ground Station ◽  
Free Relative ◽  
Climate Studies ◽  
Aerosol Backscatter ◽  
Level 2 ◽  
Good Agreement

Abstract. We present the evaluation activity of the European Aerosol Research Lidar Network (EARLINET) for the quantitative assessment of the Level 2 aerosol backscatter coefficient product derived by the Cloud-Aerosol Transport System (CATS) onboard the International Space Station (ISS). The study employs correlative CATS and EARLINET backscatter measurements within 50 km distance between the ground station and the ISS overpass and as close in time as possible, typically within 90 min, from February 2015 to September 2016. The results demonstrate the good agreement of CATS Level 2 backscatter coefficient and EARLINET. Three ISS overpasses close to the EARLINET stations of Leipzig-Germany, Évora-Portugal and Dushanbe-Tajikistan are analysed here to demonstrate the performance of CATS lidar system under different conditions. The results show that under cloud-free, relative homogeneous aerosol conditions CATS is in good agreement with EARLINET, independently of daytime/nighttime conditions. CATS low negative biases, partially attributed to the deficiency of lidar systems to detect tenuous aerosol layers of backscatter signal below the minimum detection thresholds, may lead to systematic deviations and slight underestimations of the total Aerosol Optical Depth (AOD) in climate studies. In addition, CATS misclassification of aerosol layers as clouds, and vice versa, in cases of coexistent and/or adjacent aerosol and cloud features, may lead to non-representative, unrealistic and cloud contaminated aerosol profiles. The distributions of backscatter coefficient biases show the relatively good agreement between the CATS and EARLINET measurements, although on average underestimations are observed, 22.3 % during daytime and 6.1 % during nighttime.

scholarly journals Contributions of Trans-boundary Transport to the Summertime Air Quality in Beijing, China

2016 ◽  
Author(s):  
Jiarui Wu ◽  
Guohui Li ◽  
Junji Cao ◽  
Naifang Bei ◽  
Yichen Wang ◽  
...  
Keyword(s):  
Air Quality ◽  
Control Strategies ◽  
Dominant Role ◽  
Fine Particulate Matter ◽  
Temporal Variations ◽  
Pollutant Emissions ◽  
Beijing China ◽  
Local Emissions ◽  
Factor Separation ◽  
Good Agreement

Abstract. In the present study, the WRF-CHEM model is used to evaluate the contributions of trans-boundary transport to the air quality in Beijing during a persistent air pollution episode from 5 to 14 July 2015 in Beijing-Tianjin-Hebei (BTH), China. Generally, the predicted temporal variations and spatial distributions of PM2.5 (fine particulate matter), O3 (ozone), and NO2 are in good agreement with observations in BTH. The WRF-CHEM model also reproduces reasonably well the temporal variations of aerosol species compared to measurements in Beijing. The factor separation approach is employed to evaluate the contributions of trans-boundary transport of emissions outside of Beijing to the PM2.5 and O3 levels in Beijing. On average, in the afternoon during the simulation episode, the pure local emissions contribute 22.4 % to the O3 level in Beijing, less than 36.6 % from pure emissions outside of Beijing. The O3 concentrations in Beijing are decreased by 5.1 % in the afternoon due to interactions of local emissions with those outside of Beijing. The pure emissions outside of Beijing play a dominant role in the PM2.5 level in Beijing, with a contribution of 61.5 %, much more than 13.7 % from pure Beijing local emissions. The emissions interactions enhance the PM2.5 concentrations in Beijing, with a contribution of 5.9 %. Therefore, the air quality in Beijing is primarily determined by the trans-boundary transport of emissions outside of Beijing during summertime, showing that the cooperation with neighboring provinces to mitigate pollutant emissions is a key for Beijing to improve air quality. Considering the uncertainties in the emission inventory and the meteorological field simulations, further studies need to be performed to improve the WRF-CHEM model simulations to reasonably evaluate trans-boundary transport contributions to the air quality in Beijing for supporting the design and implementation of emission control strategies.

scholarly journals Repeatability of the Universiti Teknologi MARA reading charts

2015 ◽  
Vol 14 (3) ◽  
pp. 236-240 ◽  
Author(s):  
Noor Halilah Buari ◽  
Nur Hidayah Yusuf ◽  
Adib Mohd Satali ◽  
Ai Hong Chen
Keyword(s):  
Random Sequence ◽  
Medical Science ◽  
Reading Rate ◽  
Read Aloud ◽  
Intra Class Correlation ◽  
Significant Difference ◽  
Good Consistency ◽  
Reading Charts ◽  
Intra Class Correlation Coefficient ◽  
Good Agreement

Objective: This study was done to investigate the repeatability measurements in reading rate using the Universiti Teknologi MARA Malay related words (UiTM-Mrw) reading chart and Universiti Teknologi MARA Malay unrelated words (UiTM-Muw) reading chart. Methodology: Thirty normally sighted participants were randomly recruited through randomised sampling (mean age =21.5±1.1 years). Participants were instructed to read aloud, clearly and as quickly as possible at 2 different sessions using two different charts. The two charts were selected at random sequence. A minimum of 7 days interval was used to minimize the learning affect. The time taken to read each chart was recorded and any errors while reading was noted. Reading performance was quantified as reading rate in words per minute (wpm). Results: Comparison of reading rate between session 1 and session 2 was not significantly different (p=0.894, df=1, F=0.018) for UiTM-Mrw reading chart. The reading rate between session 1 and 2 also showed no significant difference (p=0.99, df=1, F=2.811) in UiTM-Muw reading chart. Intra-class correlation coefficient (ICC) showed a good consistency in repeatability for both UiTM-Mrw reading chart and UiTM-Muw reading chart with ICC values of 0.849 and 0.814 respectively. The Bland and Altman plot between measurement of reading rate in session 1 and session 2 showed a good agreement in UiTM-Mrw reading chart and UiTM-Muw reading chart. Conclusion: Both UiTM-Mrw reading chart and UiTM-Mur reading chart showed a good consistency and good agreement in repeated measurement of reading rate.Bangladesh Journal of Medical Science Vol.14(3) 2015 p.236-240

scholarly journals An improved transmitter system to accurately measure wet-bulb temperature of air

2019 ◽  
Vol 52 (7-8) ◽  
pp. 1002-1007
Author(s):  
Liangwen Yan ◽  
Peng Yu ◽  
Sijung Hu ◽  
Qiu Gao ◽  
Wei Li ◽  
...  
Keyword(s):  
Real Time ◽  
Latent Heat ◽  
Measurement Accuracy ◽  
Cost Effective ◽  
Mean Value ◽  
Experimental Results ◽  
Iteration Algorithm ◽  
Good Consistency ◽  
The Mean ◽  
Good Agreement

A cost-effective measurement of wet-bulb temperature of air has great benefits to fulfill a growing demand of industry, cultivation agriculture, and medication. Applying an appropriate algorithm to wet-bulb temperature of air measurement can effectively improve the accuracy and speed of its measurement. The study aims to research how an improved transmitter system along with the latent heat–based iteration algorithm is used to precisely measure wet-bulb temperature of air. The work consists of (1) simulation of the iteration algorithm and (2) validation via experimental protocol. The simulation results through latent heat–based iteration algorithm were in good agreement ( R2≥ 0.99) with the reference. The performance of the improved wet-bulb temperature of air transmitter system was tested by a latent heat–based iteration algorithm experimental setup. The experimental results demonstrate that the improved wet-bulb temperature of air in a good consistency with commercial wet-bulb temperature of air in a range of temperature (15°C–34°C) and relative humidity (28.8%–76.2%). The Bland–Altman plot also shows that the mean value and the standard deviation of the differences between these two systems are 0.14°C and 0.29°C, respectively, which indicates that the improved wet-bulb temperature of air has a good agreement as well. Compared with the commercial wet-bulb temperature of air transmitter system, an advanced processor (STM32F103C8T6) and real-time operating system was applied in the improved wet-bulb temperature of air transmitter system. The experimental results show that its measurement accuracy is closer to the previous study. This study provides an alternative and cost-effective solution to accurately and real-time measure wet-bulb temperature of air.

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