In situ adaptive timestep control and visualization based on the spatio-temporal variations of the simulation results

Monitoring of water quality changes in highly dynamic inland lakes is frequently impeded by insufficient spatial and temporal coverage, for both field surveys and remote sensing methods. To track short-term variations of chlorophyll fluorescence and chlorophyll-a concentrations in Poyang Lake, the largest freshwater lake in China, high-frequency, in-situ, measurements were collected from two fixed stations. The K-mean clustering method was also applied to identify clusters with similar spatio-temporal variations, using remote sensing Chl-a data products from the MERIS satellite, taken from 2003 to 2012. Four lake area classes were obtained with distinct spatio-temporal patterns, two of which were selected for in situ measurement. Distinct daily periodic variations were observed, with peaks at approximately 3:00 PM and troughs at night or early morning. Short-term variations of chlorophyll fluorescence and Chl-a levels were revealed, with a maximum intra-diurnal ratio of 5.1 and inter-diurnal ratio of 7.4, respectively. Using geostatistical analysis, the temporal range of chlorophyll fluorescence and corresponding Chl-a variations was determined to be 9.6 h, which indicates that there is a temporal discrepancy between Chl-a variations and the sampling frequency of current satellite missions. An analysis of the optimal sampling strategies demonstrated that the influence of the sampling time on the mean Chl-a concentrations observed was higher than 25%, and the uncertainty of any single Terra/MODIS or Aqua/MODIS observation was approximately 15%. Therefore, sampling twice a day is essential to resolve Chl-a variations with a bias level of 10% or less. The results highlight short-term variations of critical water quality parameters in freshwater, and they help identify specific design requirements for geostationary earth observation missions, so that they can better address the challenges of monitoring complex coastal and inland environments around the world.

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In situ relationships between spatio-temporal variations in diuron concentrations and phototrophic biofilm tolerance in a contaminated river

Water Research ◽

10.1016/j.watres.2009.11.053 ◽

2010 ◽

Vol 44 (6) ◽

pp. 1941-1949 ◽

Cited By ~ 57

Author(s):

Stéphane Pesce ◽

Christelle Margoum ◽

Bernard Montuelle

Keyword(s):

Temporal Variations ◽

Phototrophic Biofilm ◽

Spatio Temporal

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Assessing spatio-temporal variations of precipitation-use efficiency over Tibetan grasslands using MODIS and in-situ observations

Frontiers of Earth Science ◽

10.1007/s11707-016-0566-3 ◽

2016 ◽

Vol 10 (4) ◽

pp. 784-793 ◽

Cited By ~ 2

Author(s):

Zhengjia Liu ◽

Mei Huang

Keyword(s):

Temporal Variations ◽

Use Efficiency ◽

In Situ Observations ◽

Spatio Temporal ◽

Precipitation Use Efficiency

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Spatio-Temporal Variations of Atmospheric NH3 over East Asia by Comparison of Chemical Transport Model Results, Satellite Retrievals and Surface Observations

Atmosphere ◽

10.3390/atmos11090900 ◽

2020 ◽

Vol 11 (9) ◽

pp. 900 ◽

Cited By ~ 1

Author(s):

Zhe Wang ◽

Itsushi Uno ◽

Kazuo Osada ◽

Syuichi Itahashi ◽

Keiya Yumimoto ◽

...

Keyword(s):

High Resolution ◽

East Asia ◽

Temporal Variations ◽

Central China ◽

Model Simulations ◽

Satellite Retrievals ◽

In Situ Observations ◽

Spatio Temporal ◽

Surface Observations

Atmospheric ammonia (NH3) plays an important role in the formation of secondary inorganic aerosols, the neutralization of acid rain, and the deposition to ecosystems, but has not been well understood yet, especially over East Asia. Based on the GEOS-Chem model results, the IASI satellite retrievals, the in-site surface observations of a nationwide filter pack (FP) network over Japan and the long-term high resolution online NH3 measurements at Fukuoka of western Japan, the spatio-temporal distributions of atmospheric NH3 over East Asia was analyzed comprehensively. A significant seasonal variation with a summer peak was found in all datasets. Comparison between the satellite retrievals and model simulations indicated that the IASI NH3 vertical column density (VCD) showed good consistency with GEOS-Chem results over North and central China, but had large differences over South China due to the effect of clouds. Over the Japan area, GEOS-Chem simulated NH3 concentrations successfully reproduced the spatio-temporal variations compared with in-situ observations, while IASI NH3 VCD retrievals were below or near the detection limit and difficult to obtain a reasonable correlation for with model results. The comprehensive analysis indicated that there were still some differences among different datasets, and more in-situ observations, improved satellite retrievals, and high-resolution model simulations with more accurate emissions are necessary for better understanding the atmospheric NH3 over East Asia.

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Matching high resolution satellite data and flux tower footprints improves their agreement in photosynthesis estimates

10.31223/x5nw55 ◽

2022 ◽

Author(s):

Juwon Kong ◽

Youngryel Ryu ◽

Jiangong Liu ◽

Benjamin Dechant ◽

Camilo Rey-Sanchez ◽

...

Keyword(s):

Temporal Resolution ◽

Near Infrared ◽

Temporal Variations ◽

High Temporal Resolution ◽

Canopy Photosynthesis ◽

Flux Tower ◽

Combining Data ◽

Spatio Temporal ◽

Study Sites

Mapping canopy photosynthesis in both high spatial and temporal resolution is essential for carbon cycle monitoring in heterogeneous areas. However, well established satellites in sun-synchronous orbits such as Sentinel-2, Landsat and MODIS can only provide either high spatial or high temporal resolution but not both. Recently established CubeSat satellite constellations have created an opportunity to overcome this resolution trade-off. In particular, Planet Fusion allows full utilization of the CubeSat data resolution and coverage while maintaining high radiometric quality. In this study, we used the Planet Fusion surface reflectance product to calculate daily, 3-m resolution, gap-free maps of the near-infrared radiation reflected from vegetation (NIRvP). We then evaluated the performance of these NIRvP maps for estimating canopy photosynthesis by comparing with data from a flux tower network in Sacramento-San Joaquin Delta, California, USA. Overall, NIRvP maps captured temporal variations in canopy photosynthesis of individual sites, despite changes in water extent in the wetlands and frequent mowing in the crop fields. When combining data from all sites, however, we found that robust agreement between NIRvP maps and canopy photosynthesis could only be achieved when matching NIRvP maps to the flux tower footprints. In this case of matched footprints, NIRvP maps showed considerably better performance than in situ NIRvP in estimating canopy photosynthesis both for daily sum and data around the time of satellite overpass (R 2 = 0.78 vs. 0.60, for maps vs. in situ for the satellite overpass time case). This difference in performance was mostly due to the higher degree of consistency in slopes of NIRvP -canopy photosynthesis relationships across the study sites for flux tower footprint-matched maps. Our results show the importance of matching satellite observations to the flux tower footprint and demonstrate the potential of CubeSat constellation imagery to monitor canopy photosynthesis remotely at high spatio-temporal resolution.

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