scholarly journals Intercomparison of integrated IASI and AATSR calibrated radiances at 11 and 12 μm

2009 ◽  
Vol 9 (18) ◽  
pp. 6677-6683 ◽  
Author(s):  
S. M. Illingworth ◽  
J. J. Remedios ◽  
R. J. Parker
Keyword(s):  
Weather Prediction ◽  
Radiometric Calibration ◽  
Spectral Filter ◽  
Brightness Temperatures ◽  
First Results ◽  
Data Points ◽  
The Difference ◽  
Cross Calibration ◽  
Sky Conditions

Abstract. The mission objectives of the Infrared Atmospheric Sounding Interferometer (IASI) are driven by the needs of the Numerical Weather Prediction (NWP) and climate monitoring communities. These objectives rely upon the IASI instrument being able to measure top of atmosphere radiances accurately. This paper presents a technique and first results for the validation of the radiometric calibration of radiances for IASI, using a cross-calibration with the Advanced Along Track Scanning Radiometer (AATSR). The AATSR is able to measure Brightness Temperature (BT) to an accuracy of 30 mK, and by applying the AATSR spectral filter functions to the IASI measured radiances we are able to compare AATSR and IASI Brightness Temperatures. By choosing coincident data points that are over the sea and in clear sky conditions, a threshold of homogeneity is derived. It is found that in these homogenous conditions, the IASI BTs agree with those measured by the AATSR to within 0.3 K, with an uncertainty of order 0.1 K. The agreement is particularly good at 11 μm where the difference is less than 0.1 K. These first results indicate that IASI is meeting its target objective of 0.5 K accuracy. It is believed that a refinement of the AATSR spectral filter functions will hopefully permit a tighter error constraint on the quality of the IASI data and hence further assessment of the climate quality of the radiances.

scholarly journals Intercomparison of integrated IASI and AATSR calibrated radiances

2009 ◽  
Vol 9 (2) ◽  
pp. 8101-8119 ◽  
Author(s):  
S. M. Illingworth ◽  
J. J. Remedios ◽  
R. J. Parker
Keyword(s):  
Weather Prediction ◽  
Radiometric Calibration ◽  
Spectral Filter ◽  
Filter Function ◽  
Brightness Temperatures ◽  
Data Points ◽  
Cross Calibration ◽  
Sky Conditions ◽  
Error Constraint

Abstract. The mission objectives of the Infrared Atmospheric Sounding Interferometer (IASI) are driven by the needs of the Numerical Weather Prediction (NWP) and climate monitoring communities. These objectives rely upon the IASI instrument being able to measure top of atmosphere radiances accurately. This paper presents a technique and results for the validation of the radiometric calibration of radiances for IASI, using a cross-calibration with the Advanced Along Track Scanning Radiometer (AATSR). The AATSR is able to measure Brightness Temperature (BT) to an accuracy of 30 mK, and by applying the AATSR spectral filter function to the IASI measured radiances we are able to compare AATSR and IASI Brightness Temperatures. By choosing coincidental data points that are over the sea and in clear sky conditions, a threshold of homogeneity is derived. It is found that in these homogenous conditions, the IASI BTs agree with those measured by the AATSR to within 0.5 K, with a precision of order 0.04 K. These results indicate that IASI is likely to be meeting its target objective of 0.5 K accuracy. It is believed that a refinement of the AATSR spectral filter function will hopefully permit a tighter error constraint on the quality of the IASI data and hence further assessment of the climate quality of the radiances.

scholarly journals McClear: a new model estimating downwelling solar radiation at ground level in clear-sky conditions

2013 ◽  
Vol 6 (9) ◽  
pp. 2403-2418 ◽  
Author(s):  
M. Lefèvre ◽  
A. Oumbe ◽  
P. Blanc ◽  
B. Espinar ◽  
B. Gschwind ◽  
...  
Keyword(s):  
Correlation Coefficient ◽  
Weather Prediction ◽  
Ground Level ◽  
Surface Radiation ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Clear Sky ◽  
Sky Conditions ◽  
Aerosol Properties

Abstract. A new fast clear-sky model called McClear was developed to estimate the downwelling shortwave direct and global irradiances received at ground level under clear skies. It is a fully physical model replacing empirical relations or simpler models used before. It exploits the recent results on aerosol properties, and total column content in water vapour and ozone produced by the MACC project (Monitoring Atmosphere Composition and Climate). It accurately reproduces the irradiance computed by the libRadtran reference radiative transfer model with a computational speed approximately 105 times greater by adopting the abaci, or look-up table, approach combined with interpolation functions. It is therefore suited for geostationary satellite retrievals or numerical weather prediction schemes with many pixels or grid points, respectively. McClear irradiances were compared to 1 min measurements made in clear-sky conditions at several stations within the Baseline Surface Radiation Network in various climates. The bias for global irradiance comprises between −6 and 25 W m−2. The RMSE ranges from 20 W m−2 (3% of the mean observed irradiance) to 36 W m−2 (5%) and the correlation coefficient ranges between 0.95 and 0.99. The bias for the direct irradiance comprises between −48 and +33 W m−2. The root mean square error (RMSE) ranges from 33 W m−2 (5%) to 64 W m−2 (10%). The correlation coefficient ranges between 0.84 and 0.98. This work demonstrates the quality of the McClear model combined with MACC products, and indirectly the quality of the aerosol properties modelled by the MACC reanalysis.

scholarly journals The Role of NWP Filter for the Satellite Based Detection of Cumulonimbus Clouds

2017 ◽  
Author(s):  
Richard Mülller ◽  
Stephane Haussler ◽  
Matthias Jerg
Keyword(s):  
Weather Prediction ◽  
Convective Available Potential Energy ◽  
Probability Of Detection ◽  
False Alarms ◽  
Brightness Temperatures ◽  
Critical Success ◽  
High Clouds ◽  
Cumulonimbus Clouds

The study investigates the role of NWP filtering for the remote sensing of Cumulonimbus Clouds (Cbs) by implementation of 14 different experiments, covering Central Europe. These experiments compiles different stability filter settings as well as the use of different channels for the InfraRed (IR) brightness temperatures. As stability filter parameters from Numerical Weather Prediction (NWP) are used. The brightness temperature information results from the IR SEVIRI instrument on-board of Meteosat Second Generation satellite and enables the detection of very cold and high clouds close to the tropopause. The satellite only approaches (no NWP filtering) result in the detection of Cbs with a relative high probability of detection, but unfortunately combined with a large False Alarm Rate (FAR), leading to a Critical Success Index (CSI) below 60 %. The false alarms results from other types of very cold and high clouds. It is shown that the false alarms can be significantly decreased by application of an appropriate NWP stability filter, leading to the increase of CSI to about 70 % . A brief review and reflection of the literature clarifies that the this function of the NWP filter can not be replaced by MSG IR spectroscopy. Thus, NWP filtering is strongly recommended to increase the quality of satellite based Cb detection. Further, it has been shown that the well established convective available potential energy (CAPE) and the convection index (KO) works well as stability filter.

scholarly journals Long-term stability of TES satellite radiance measurements

2011 ◽  
Vol 4 (7) ◽  
pp. 1481-1490 ◽  
Author(s):  
T. C. Connor ◽  
M. W. Shephard ◽  
V. H. Payne ◽  
K. E. Cady-Pereira ◽  
S. S. Kulawik ◽  
...  
Keyword(s):  
Optical Depth ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Radiometric Calibration ◽  
Cloud Optical Depth ◽  
Brightness Temperatures ◽  
The Difference ◽  
The Stability ◽  
Reference Measurements

Abstract. The utilization of Tropospheric Emission Spectrometer (TES) Level 2 (L2) retrieval products for the purpose of assessing long term changes in atmospheric trace gas composition requires knowledge of the overall radiometric stability of the Level 1B (L1B) radiances. The purpose of this study is to evaluate the stability of the radiometric calibration of the TES instrument by analyzing the difference between measured and calculated brightness temperatures in selected window regions of the spectrum. The Global Modeling and Assimilation Office (GMAO) profiles for temperature and water vapor and the Real-Time Global Sea Surface Temperature (RTGSST) are used as input to the Optimal Spectral Sampling (OSS) radiative transfer model to calculate the simulated spectra. The TES reference measurements selected cover a 4-year period of time from mid 2005 through mid 2009 with the selection criteria being; observation latitudes greater than −30° and less than 30°, over ocean, Global Survey mode (nadir view) and retrieved cloud optical depth of less than or equal to 0.01. The TES cloud optical depth retrievals are used only for screening purposes and no effects of clouds on the radiances are included in the forward model. This initial screening results in over 55 000 potential reference spectra spanning the four year period. Presented is a trend analysis of the time series of the residuals (observation minus calculations) in the TES 2B1, 1B2, 2A1, and 1A1 bands, with the standard deviation of the residuals being approximately equal to 0.6 K for bands 2B1, 1B2, 2A1, and 0.9 K for band 1A1. The analysis demonstrates that the trend in the residuals is not significantly different from zero over the 4-year period. This is one method used to demonstrate that the relative radiometric calibration is stable over time, which is very important for any longer term analysis of TES retrieved products (L2), particularly well-mixed species such as carbon dioxide and methane.

scholarly journals Characterizing glitches and timing irregularities in pulsars and magnetars

2012 ◽  
Vol 8 (S291) ◽  
pp. 381-381
Author(s):  
Cristobal Espinoza ◽  
Danai Antonopoulou ◽  
Alessandro Patruno ◽  
Ben Stappers ◽  
Anna Watts
Keyword(s):  
Small Sample ◽  
Radio Pulsars ◽  
Physical Mechanisms ◽  
Timing Data ◽  
First Results ◽  
Different Populations ◽  
Timing Noise ◽  
Error Bars ◽  
The Difference

AbstractAs the quantity and quality of timing data improves, we have reached the point at which the difference between timing noise and small glitches is unclear. As a consequence, the number of events reported as glitches which show unusual properties, quite different to those of giant glitches, has increased. For example, there is now a substantial population of glitches that apparently involve a decrease in spin-down rate rather than an increase. Motivated by the theoretical implications of such a result, we are conducting a detailed review of how glitches are detected and characterised. We have focused on three main questions: the observational biases affecting glitch detection; the methods used to characterise error bars on changes in spin and spin derivatives; and the physical mechanisms that could potentially explain the different populations of timing irregularities, in the light of improved characterisation. While glitches are thought to be a consequence of the internal dynamics of the star, magnetospheric processes may be responsible for other irregularities, as timing noise and peculiar glitch recoveries. We report the first results from this study, using a small sample of radio pulsars that exhibit a wide variety of glitching behaviour.

scholarly journals Global carbon monoxide as retrieved from SCIAMACHY by WFM-DOAS

2004 ◽  
Vol 4 (7) ◽  
pp. 1945-1960 ◽  
Author(s):  
M. Buchwitz ◽  
R. de Beek ◽  
K. Bramstedt ◽  
S. Noël ◽  
H. Bovensmann ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Near Infrared ◽  
Weighting Function ◽  
Constant Factor ◽  
Retrieval Algorithm ◽  
First Results ◽  
Infrared Spectral ◽  
The Difference ◽  
Global Carbon

Abstract. First results concerning the retrieval of tropospheric carbon monoxide (CO) from satellite solar backscatter radiance measurements in the near-infrared spectral region (~2.3µm) are presented. The Weighting Function Modified (WFM) DOAS retrieval algorithm has been used to retrieve vertical columns of CO from SCIAMACHY/ENVISAT nadir spectra. We present detailed results for three days from the time periode January to October 2003 selected to have good overlap with the daytime CO measurements of MOPITT onboard EOS Terra. Because the WFM-DOAS Version 0.4 CO columns presented in this paper are scaled by a constant factor of 0.5 to compensate for an obvious overestimation we focus on the variability of the retrieved columns rather than on their absolute values. It is shown that plumes of CO resulting from, e.g. biomass burning in Africa, are detectable with single overpass SCIAMACHY data. Globally, the SCIAMACHY CO columns are in reasonable agreement with the Version 3 CO column data product of MOPITT. For example, for measurements over land, where the quality of the data is typically better than over ocean due to higher surface reflectivity, the standard deviation of the difference with respect to MOPITT is in the range 0.4-0.6x1018 molecules/cm2 and the linear correlation coefficient is between 0.4 and 0.7. The level of agreement between the data of both sensors depends on time and location but is typically within 30% for most latitudes. In the southern hemisphere outside Antarctica SCIAMACHY tends to give systematically higher values than MOPITT. More studies are needed to find out what the reasons for the observed differences with respect to MOPITT are and how the algorithm can be modified to improve the quality of the CO columns as retrieved from SCIAMACHY.

scholarly journals McClear: a new model estimating downwelling solar radiation at ground level in clear-sky conditions

2013 ◽  
Vol 6 (2) ◽  
pp. 3367-3405 ◽  
Author(s):  
M. Lefèvre ◽  
A. Oumbe ◽  
P. Blanc ◽  
B. Espinar ◽  
B. Gschwind ◽  
...  
Keyword(s):  
Weather Prediction ◽  
Physical Modelling ◽  
Ground Level ◽  
Surface Radiation ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Clear Sky ◽  
Sky Conditions ◽  
Aerosol Properties

Abstract. A new fast clear-sky model called McClear was developed to estimate the downwelling shortwave direct and global irradiances received at ground level under clear skies. McClear implements a fully physical modelling replacing empirical relations or simpler models used before. It exploits the recent results on aerosol properties, and total column content in water vapor and ozone produced by the MACC project (Monitoring Atmosphere Composition and Climate). It accurately reproduces the irradiance computed by the libRadtran reference radiative transfer model with a computational speed approximately 105 times greater by adopting the abaci, or look-up tables, approach combined with interpolation functions. It is therefore suited for geostationary satellite retrievals or numerical weather prediction schemes with many pixels or grid points, respectively. McClear irradiances were compared to 1 min measurements made in clear-sky conditions in several stations within the Baseline Surface Radiation Network in various climates. For global, respectively direct, irradiance, the correlation coefficient ranges between 0.95 and 0.99, resp. 0.86 and 0.99. The bias is comprised between −14 and 25 W m−2, resp. −49 and +33 W m−2. The RMSE ranges between 20 W m−2 (3% of the mean observed irradiance) and 36 W m−2 (5%), resp. 33 W m−2 (5%) and 64 W m−2 (10%). These results are much better than those from state-of-the-art models. This work demonstrates the quality of the McClear model combined with MACC products, and indirectly the quality of the aerosol properties modeled by the MACC reanalysis.

scholarly journals Orbital Lifetime (2008–2017) Radiometric Calibration and Evaluation of the HJ-1B IRS Thermal Infrared Band

2020 ◽  
Vol 12 (15) ◽  
pp. 2362
Author(s):  
Wanyue Liu ◽  
Jiaguo Li ◽  
Qijin Han ◽  
Li Zhu ◽  
Hongyan Yang ◽  
...  
Keyword(s):  
Thermal Infrared ◽  
Radiometric Calibration ◽  
Infrared Sensor ◽  
Annual Change ◽  
Field Validation ◽  
Lake Qinghai ◽  
Infrared Band ◽  
The Difference ◽  
Cross Calibration ◽  
Calibration Coefficients

The infrared sensor (IRS) is a payload on the HJ-1B satellite and includes a thermal infrared band (B08). In order to obtain radiometric calibration coefficients and evaluate annual change, this study performed an analysis covering its 10-year orbital lifetime (2008–2017). The cross-calibration of IRS B08 with MODIS was performed using near-simultaneous images over Lake Qinghai, China. The results reveal that the radiometric response of IRS B08 notably changed during its orbital lifetime from year-to-year. The offsets fluctuated more than the gain. The top-of-atmosphere (TOA) radiance obtained by calibration coefficients in this study was generally in agreement with those obtained by onboard calibrator, within an error range of ±4.00% from 2008 to 2012. The percent difference compared with field validation was within 1.63%. The difference between IRS and MODIS radiance over field validation sites was within ±5%. Approximately a 1% difference occurred between the TOA temperature of IRS and MODIS. The radiometric response of IRS B08 continuously decreased from 2008 to 2013, whereas it fluctuated from 2014 to 2017. Moreover, the DN fluctuated more when the at-aperture radiance was low, although it was more stable at higher radiance.

scholarly journals Long-term stability of TES satellite radiance measurements

2011 ◽  
Vol 4 (2) ◽  
pp. 1723-1749
Author(s):  
T. C. Connor ◽  
M. W. Shephard ◽  
V. H. Payne ◽  
K. E. Cady-Pereira ◽  
S. S. Kulawik ◽  
...  
Keyword(s):  
Optical Depth ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Radiometric Calibration ◽  
Cloud Optical Depth ◽  
Brightness Temperatures ◽  
The Difference ◽  
The Stability ◽  
Reference Measurements

Abstract. The utilization of Tropospheric Emission Spectrometer (TES) Level 2 (L2) retrieval products for the purpose of assessing long term changes in atmospheric trace gas composition requires knowledge of the overall radiometric stability of the Level 1B (L1B) radiances. The purpose of this study is to evaluate the stability of the radiometric calibration of the TES instrument by analyzing the difference between measured and calculated brightness temperatures in selected window regions of the spectrum. The Global Modeling and Assimilation Office (GMAO) profiles for temperature and water vapor and the Real-Time Global Sea Surface Temperature (RTGSST) are used as input to the Optimal Spectral Sampling (OSS) radiative transfer model to calculate the simulated spectra. The TES reference measurements selected cover a 4-year period of time from mid 2005 through mid 2009 with the selection criteria being; observation latitudes greater than −30° and less than 30°, over ocean, Global Survey mode (nadir view) and retrieved cloud optical depth of less than 0.01. The TES cloud optical depth retrievals are used only for screening purposes and no effects of clouds on the radiances are included in the forward model. This initial screening results in over 55 000 potential reference spectra spanning the four year period. Presented is a trend analysis of the time series of the residuals (observation minus calculations) in the TES 2B1, 1B2, 2A1, and 1A1 bands which demonstrates that the trend in the residuals is not significantly different from zero over the 4-year period. This is one method used to demonstrate that the relative radiometric calibration is stable over time, which is very important for any longer term analysis of TES retrieved products (L2) particularly well-mixed species such as carbon dioxide and methane.

scholarly journals The Analysis of The Process of Barley Grain Separation from Undesirable Particles

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Jiří ZEGZULKA ◽  
Lucie JEZERSKA ◽  
HETCLOVA Vladimíra ◽  
PROKES Rostislav ◽  
RUTTKAY Vaclav
Keyword(s):  
Friction Angle ◽  
Barley Grain ◽  
Separation Processes ◽  
Material Particle ◽  
Angle Of Internal Friction ◽  
Powder Density ◽  
First Results ◽  
The Difference ◽  
Barley Grains

The article focuses on the intensification of raw barley grains initial purification and separation processes before the subsequentprocessing in the area of brewing. Above all, it deals with the physical and mechanical concepts of the purification and separationof qualitatively satisfactory grains from undesirable impurities, e.g. coarse impurities, as the prevention from the potential damageof milling and scrapping facilities. Four different cultivated barley species were tested within the study. Physical and mechanicalparameters were determined in all samples, for instance powder density, angle of internal friction and external friction angle withsteel contact material, particle size distribution and morphology. The first results of measuring revealed the difference in the qualityof initial entering component of barley grains before the purification process compared to the output quality of grains after machinepurification and separation processes in the facilities determined for the subsequent grain storage. As a result of the non-effectiveprocess of separation, the final quality of the product, i.e. the beer, may be affected by the qualitative parameters of partial processesinvolved in treating barley grains.

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