scholarly journals Error Estimation of Pathfinder Version 5.3 Level-3C SST Using Extended Triple Collocation Analysis

2020 ◽  
Vol 12 (4) ◽  
pp. 590
Author(s):  
Korak Saha ◽  
Prasanjit Dash ◽  
Xuepeng Zhao ◽  
Huai-min Zhang
Keyword(s):  
Signal To Noise Ratio ◽  
Global Climate ◽  
Atmospheric Models ◽  
Science And Policy ◽  
Satellite Sst ◽  
Error Characterization ◽  
Essential Input ◽  
Ocean Forecasting ◽  
Mutually Independent

Sea Surface Temperature (SST) is an essential climate variable (ECV) for monitoring the state and detecting changes in the climate. The concept of ECVs, developed by the Global Climate Observing System (GCOS) program of the World Meteorological Organization (WMO), has been broadly adopted in worldwide science and policy circles Besides being a climate change indicator, the global SST field is an essential input for atmospheric models, air-sea exchange studies, understanding marine ecosystems, operational weather, and ocean forecasting, military and defense operations, tourism, and fisheries research. It is, therefore, critical to understand the errors associated with SST measurements from both in situ measurements and satellite observations. The customary way of validating a satellite SST is to compare it with in situ measured SSTs. This method, however, will have inaccuracies due to uncertainties involving both types of measurements. A triple collocation (TC) error analysis can be implemented on three mutually independent error-prone measurements to estimate the root-mean-square error (RMSE) of each measurement. In this study, the error characterization for the Pathfinder SST version 5.3 (PF53) dataset is performed using an extended TC (ETC) method and reported to be in the range of 0.31 to 0.37 K. These values are reasonable, as is evident from corresponding very high (~0.98) unbiased signal-to-noise ratio (SNR) values.

scholarly journals Combining In Situ and Satellite Observations to Retrieve Salinity and Density at the Ocean Surface

2016 ◽  
Vol 33 (6) ◽  
pp. 1211-1223 ◽  
Author(s):  
R. Droghei ◽  
B. Buongiorno Nardelli ◽  
R. Santoleri
Keyword(s):  
Global Climate ◽  
Sea Surface ◽  
Sea Surface Salinity ◽  
Additional Parameter ◽  
Regional Study ◽  
Surface Salinity ◽  
The North ◽  
Satellite Sst ◽  
Holdout Validation

AbstractMonitoring sea surface density (SSD), sea surface salinity (SSS), and sea surface temperature (SST) allows for investigating important aspects of the earth system dynamics, with relevant implications on both local/regional short-scale processes and global climate. Different approaches combine in situ measurements and satellite data to provide gap-free SSS at regular spatial and temporal resolution, aiming to resolve ocean mesoscale. Depending on the application, however, knowing SSD would be more useful than SSS and/or SST alone. Indeed, even if density can be obtained by combining SSS and SST maps at the same nominal resolution, this procedure can lead to spurious features and larger errors when SSS and SST are obtained from different observations and interpolation techniques, especially at the mesoscale. A multidimensional covariance model is applied to interpolate either in situ salinity or in situ density measurements and to build dynamically coherent surface fields, using satellite SST differences as an additional parameter in the optimal estimate. SSS/SSD level 4 (L4) maps are reconstructed over the North Atlantic area, analyzing one month of data. The L4 data are validated using data from the first Salinity Processes in the Upper Ocean Regional Study (SPURS-1) field campaign. The root-mean-square error (RMSE) ranges between 0.03 and 0.13 for the SSS L4 data, and between 0.09 and 0.32 kg m−3 for the SSD L4 data, with improvements of up to 20% with respect to standard products. A holdout validation provides similar values for the SSS RMSE (0.13 ÷ 0.17) and the SSD RMSE (0.13 ÷ 0.17 kg m−3). The limitations and advantages of the two approaches are further discussed and analyzed by looking at spatial wavenumber spectra, showing that the multidimensional optimum interpolation (OI) method significantly increases the L4 effective resolution.

scholarly journals Detected Changes in Precipitation Extremes at Their Native Scales Derived from In Situ Measurements

2019 ◽  
Vol 32 (23) ◽  
pp. 8087-8109 ◽  
Author(s):  
Mark D. Risser ◽  
Christopher J. Paciorek ◽  
Travis A. O’Brien ◽  
Michael F. Wehner ◽  
William D. Collins
Keyword(s):  
Extreme Precipitation ◽  
Seasonal Changes ◽  
Signal To Noise Ratio ◽  
Statistical Technique ◽  
In Situ Measurements ◽  
Absolute Sense ◽  
Underlying Causes ◽  
Changes Over Time ◽  
Future Work

Abstract The gridding of daily accumulated precipitation—especially extremes—from ground-based station observations is problematic due to the fractal nature of precipitation, and therefore estimates of long period return values and their changes based on such gridded daily datasets are generally underestimated. In this paper, we characterize high-resolution changes in observed extreme precipitation from 1950 to 2017 for the contiguous United States (CONUS) based on in situ measurements only. Our analysis utilizes spatial statistical methods that allow us to derive gridded estimates that do not smooth extreme daily measurements and are consistent with statistics from the original station data while increasing the resulting signal-to-noise ratio. Furthermore, we use a robust statistical technique to identify significant pointwise changes in the climatology of extreme precipitation while carefully controlling the rate of false positives. We present and discuss seasonal changes in the statistics of extreme precipitation: the largest and most spatially coherent pointwise changes are in fall (SON), with approximately 33% of CONUS exhibiting significant changes (in an absolute sense). Other seasons display very few meaningful pointwise changes (in either a relative or absolute sense), illustrating the difficulty in detecting pointwise changes in extreme precipitation based on in situ measurements. While our main result involves seasonal changes, we also present and discuss annual changes in the statistics of extreme precipitation. In this paper we only seek to detect changes over time and leave attribution of the underlying causes of these changes for future work.

scholarly journals Ultrastructural visualization of cytoskeletal mRNAs and their associated proteins using double-label in situ hybridization.

1989 ◽  
Vol 108 (6) ◽  
pp. 2343-2353 ◽  
Author(s):  
R H Singer ◽  
G L Langevin ◽  
J B Lawrence
Keyword(s):  
In Situ Hybridization ◽  
High Resolution ◽  
Colloidal Gold ◽  
Messenger Rna ◽  
Signal To Noise Ratio ◽  
Simultaneous Detection ◽  
Gold Particles ◽  
Rna Molecules ◽  
Nucleic Acid Molecule

We have been able to visualize cytoskeletal messenger RNA molecules at high resolution using nonisotopic in situ hybridization followed by whole-mount electron microscopy. Biotinated cDNA probes for actin, tubulin, or vimentin mRNAs were hybridized to Triton-extracted chicken embryo fibroblasts and myoblasts. The cells were then exposed to antibodies against biotin followed by colloidal gold-conjugated antibodies and then critical-point dried. Identification of mRNA was possible using a probe fragmented to small sizes such that hybridization of several probe fragments along the mRNA was detected as a string of colloidal gold particles qualitatively and quantitatively distinguishable from nonspecific background. Extensive analysis showed that when eight gold particles were seen in this iterated array, the signal to noise ratio was greater than 30:1. Furthermore, these gold particles were colinear, often spiral, or circular suggesting detection of a single nucleic acid molecule. Antibodies against actin, vimentin, or tubulin proteins were used after in situ hybridization, allowing simultaneous detection of the protein and its cognate message on the same sample. This revealed that cytoskeletal mRNAs are likely to be extremely close to actin protein (5 nm or less) and unlikely to be within 20 nm of vimentin or tubulin filaments. Actin mRNA was found to be more predominant in lamellipodia of motile cells, confirming previous results. These results indicate that this high resolution in situ hybridization approach is a powerful tool by which to investigate the association of mRNA with the cytoskeleton.

Challenges in Estuarine and Coastal Science

2022 ◽  
Keyword(s):  
Anthropogenic Impacts ◽  
Global Climate ◽  
50Th Anniversary ◽  
Science And Policy ◽  
Coastal Conservation ◽  
Marine Management ◽  
Coastal Squeeze ◽  
Future Challenges ◽  
Tidal Freshwaters ◽  
Estuarine Coastal

Estuarine and coastal waters are acknowledged centres for anthropogenic impacts. Superimposed on the complex natural interactions between land, rivers and sea are the myriad consequences of human activity – a spectrum ranging from locally polluting effluents to some of the severest consequences of global climate change. For practitioners, academics and students in the field of coastal science and policy, this book examines and exemplifies current and future challenges: from upper estuaries to open coasts and adjacent seas; from tropical to temperate latitudes; from Europe to Australia. This authoritative volume marks the 50th anniversary of the Estuarine and Coastal Sciences Association, and contains a prologue by founding member Professor Richard Barnes and a short history of the Association. Individual chapters then address coastal erosion and deposition; open shores to estuaries and deltas; marine plastics; coastal squeeze and habitat loss; tidal freshwaters – saline incursion and estuarine squeeze; restoration management using remote data collection; carbon storage; species distribution and non-natives; shorebirds; Modelling environmental change; physical processes such as sediments and modelling; sea level rise and estuarine tidal dynamics; estuaries as fish nurseries; policy versus reality in coastal conservation; developments in Estuarine, coastal and marine management.

scholarly journals Synergistic effects of UVR and simulated stratification on commensalistic phytoplankton–bacteria relationship in two optically contrasting oligotrophic Mediterranean lakes

2015 ◽  
Vol 12 (3) ◽  
pp. 697-712 ◽  
Author(s):  
P. Carrillo ◽  
J. M. Medina-Sánchez ◽  
C. Durán ◽  
G. Herrera ◽  
V. E. Villafañe ◽  
...  
Keyword(s):  
Global Climate Change ◽  
Bacterial Communities ◽  
Bacterial Production ◽  
Synergistic Effects ◽  
Global Climate ◽  
Oligotrophic Lakes ◽  
Carbon Demand ◽  
In Situ Experiments ◽  
Upper Mixed Layer

Abstract. An indirect effect of global warming is a reduction in the depth of the upper mixed layer (UML) causing organisms to be exposed to higher levels of ultraviolet (UVR, 280–400 nm) and photosynthetically active radiation (PAR, 400–700 nm). This can affect primary and bacterial production as well as the commensalistic phytoplankton–bacteria relationship. The combined effects of UVR and reduction in the depth of the UML were assessed on variables related to the metabolism of phytoplankton and bacteria, during in situ experiments performed with natural pico- and nanoplankton communities from two oligotrophic lakes with contrasting UVR transparency (high-UVR versus low-UVR waters) of southern Spain. The negative UVR effects on epilimnetic primary production (PP) and on heterotrophic bacterial production (HBP), intensified under increased stratification, were higher in the low-UVR than in the high-UVR lake, and stronger on the phytoplanktonic than on the heterotrophic bacterial communities. Under UVR and increased stratification, the commensalistic phytoplankton–bacteria relationship was strengthened in the high-UVR lake where excretion of organic carbon (EOC) rates exceeded the bacterial carbon demand (BCD; i.e., BCD : EOC(%) ratio < 100). This did not occur in the low-UVR lake (i.e., BCD : EOC(%) ratio > 100). The greater UVR damage to phytoplankton and bacteria and the weakening of their commensalistic interaction found in the low-UVR lake indicates that these ecosystems would be especially vulnerable to UVR and increased stratification as stressors related to global climate change. Thus, our findings may have important implications for the carbon cycle in oligotrophic lakes of the Mediterranean region.

scholarly journals Atmospheric CO<sub>2</sub> modeling at the regional scale: an intercomparison of 5 meso-scale atmospheric models

2007 ◽  
Vol 4 (3) ◽  
pp. 1923-1952 ◽  
Author(s):  
C. Sarrat ◽  
J. Noilhan ◽  
A. J. Dolman ◽  
C. Gerbig ◽  
R. Ahmadov ◽  
...  
Keyword(s):  
Regional Scale ◽  
Potential Temperature ◽  
Surface Fluxes ◽  
Systematic Evaluation ◽  
Atmospheric Models ◽  
Experimental Protocol ◽  
Intercomparison Exercise ◽  
Meteorological Models ◽  
Meso Scale

Abstract. Atmospheric CO2 modeling in interaction with the surface fluxes, at the regional scale is developed within the frame of the European project CarboEurope-IP and its Regional Experiment component. In this context, five meso-scale meteorological models participate in an intercomparison exercise. Using a common experimental protocol that imposes a large number of rules, two days of the CarboEurope Regional Experiment Strategy (CERES) campaign are simulated. A systematic evaluation of the models is done in confrontation with the observations, using statistical tools and direct comparisons. Thus, temperature and relative humidity at 2 m, wind direction, surface energy and CO2 fluxes, vertical profiles of potential temperature as well as in-situ CO2 concentrations comparisons between observations and simulations are examined. This intercomparison exercise shows also the models ability to represent the meteorology and carbon cycling at the synoptic and regional scale in the boundary layer, but also points out some of the major shortcomings of the models.

Mapping the aerodynamic roughness of the Greenland ice sheet surface using ICESat-2

2021 ◽  
Author(s):  
Maurice van Tiggelen ◽  
Paul C.J.P. Smeets ◽  
Carleen H. Reijmer ◽  
Bert Wouters ◽  
Jakob F. Steiner ◽  
...  
Keyword(s):  
Eddy Covariance ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Surface Elevation ◽  
Spatiotemporal Variability ◽  
Atmospheric Models ◽  
Laser Altimeter ◽  
Eddy Covariance Measurements ◽  
Aerodynamic Roughness

&lt;p&gt;The roughness of a natural surface is an important parameter in atmospheric models, as it determines the intensity of turbulent transfer between the atmosphere and the surface. Unfortunately, this parameter is often poorly known, especially in remote areas where neither high-resolution elevation models nor eddy-covariance measurements are available.&lt;/p&gt;&lt;p&gt;In this study, we take advantage of the measurements of the ICESat-2 satellite laser altimeter. We use the geolocated photons product (ATL03) to retrieve a 1-m resolution surface elevation product over the K-transect (West Greenland ice sheet). In combination with a bulk drag partitioning model, the retrieved surface elevation is used to estimate the aerodynamic roughness length (z&lt;sub&gt;0m&lt;/sub&gt;) of the surface.&lt;/p&gt;&lt;p&gt;We demonstrate the high precision of the retrieved ICESat-2 elevation using co-located UAV photogrammetry, and then evaluate the modelled aerodynamic roughness against multiple in situ eddy-covariance observations. The results point out the importance to use a bulk drag model over a more empirical formulation.&lt;/p&gt;&lt;p&gt;The currently available ATL03 geolocated photons are used to map the aerodynamic roughness along the K-transect (2018-2020). We find a considerable spatiotemporal variability in z&lt;sub&gt;0m&lt;/sub&gt;, ranging between 10&lt;sup&gt;&amp;#8722;4&lt;/sup&gt; m for a smooth snow surface to more than 10&lt;sup&gt;&amp;#8722;1&lt;/sup&gt; m for rough crevassed areas, which confirms the need to incorporate a variable aerodynamic roughness in atmospheric models over ice sheets.&lt;/p&gt;

scholarly journals An Effective Similar-Pixel Reconstruction of the High-Frequency Cloud-Covered Areas of Southwest China

2019 ◽  
Vol 11 (3) ◽  
pp. 336 ◽  
Author(s):  
Wenping Yu ◽  
Junlei Tan ◽  
Mingguo Ma ◽  
Xiaolu Li ◽  
Xiaojun She ◽  
...  
Keyword(s):  
Land Surface ◽  
High Frequency ◽  
Southwest China ◽  
Global Climate ◽  
Average Error ◽  
Balance Theory ◽  
High Temporal Resolution ◽  
Retrieval Accuracy ◽  
Southwest Region

With advantages of multispatial resolutions, a high retrieval accuracy, and a high temporal resolution, the satellite-derived land surface temperature (LST) products are very important LST sources. However, the greatest barrier to their wide application is the invalid values produced by large quantities of cloudy pixels, especially for regions frequently swathed in clouds. In this study, an effective method based on the land energy balance theory and similar pixels (SP) method was developed to reconstruct the LSTs over cloudy pixels for the widely used MODIS LST (MOD11A1). The southwest region of China was selected as the study area, where extreme drought has frequently occurred in recent years in the context of global climate change and which commonly exhibits cloudy and foggy weather. The validation results compared with in situ LSTs showed that the reconstructed LSTs have an average error < 1.00 K (0.57 K at night and -0.14 K during the day) and an RMSE < 3.20 K (1.90 K at night and 3.16 K in the daytime). The experiment testing the SP interpolation indicated that the spatial structure of the LST has a greater effect on the SP performance than the size of the data-missing area, which benefits the LST reconstruction in the area frequently covered by large clouds.

A Study of Membrane Impact on Spatial Resolution of Liquid In Situ Transmission Electron Microscope

2020 ◽  
Vol 26 (1) ◽  
pp. 126-133
Author(s):  
Ming Li ◽  
Ruth Knibbe
Keyword(s):  
Electron Microscope ◽  
Spatial Resolution ◽  
Transmission Electron Microscope ◽  
Signal To Noise Ratio ◽  
Chromatic Aberration ◽  
Membrane Thickness ◽  
Additional Material ◽  
Transmission Electron ◽  
The Impact

AbstractMicrochip technology with electron transparent membranes is a key component for in situ liquid transmission electron microscope (TEM) characterization. The membranes can significantly influence the TEM imaging spatial resolution, not only due to introducing additional material layers but also due to the associated bulging. The membrane bulging is largely defined by the membrane materials, thickness, and short dimension. The impact of the membrane on the spatial resolution, especially the extent of its bulging, was systematically investigated through the impact on the signal-to-noise ratio, chromatic aberration, and beam broadening. The optimization of the membrane parameters is the key component when designing the in situ TEM liquid cell. The optimal membrane thickness of 50 nm was found which balances the impact of membrane bulging and membrane thickness. Beyond this, the short membrane window dimension and the chip nominal spacing should be minimized. However, these two parameters have practical limitations in regards to chip handling.

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