scholarly journals Consistency between GRUAN sondes, LBLRTM and IASI

2017 ◽  
Vol 10 (6) ◽  
pp. 2323-2335 ◽  
Author(s):  
Xavier Calbet ◽  
Niobe Peinado-Galan ◽  
Pilar Rípodas ◽  
Tim Trent ◽  
Ruud Dirksen ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Climate Data ◽  
Night Time ◽  
Upper Troposphere ◽  
Atmospheric Sounding ◽  
Data Record ◽  
Water Vapour Absorption ◽  
Reference Measurements

Abstract. Radiosonde soundings from the GCOS Reference Upper-Air Network (GRUAN) data record are shown to be consistent with Infrared Atmospheric Sounding Instrument (IASI)-measured radiances via LBLRTM (Line-By-Line Radiative Transfer Model) in the part of the spectrum that is mostly affected by water vapour absorption in the upper troposphere (from 700 hPa up). This result is key for climate data records, since GRUAN, IASI and LBLRTM constitute reference measurements or a reference radiative transfer model in each of their fields. This is specially the case for night-time radiosonde measurements. Although the sample size is small (16 cases), daytime GRUAN radiosonde measurements seem to have a small dry bias of 2.5 % in absolute terms of relative humidity, located mainly in the upper troposphere, with respect to LBLRTM and IASI. Full metrological closure is not yet possible and will not be until collocation uncertainties are better characterized and a full uncertainty covariance matrix is clarified for GRUAN.

scholarly journals Consistency between GRUAN sondes, LBLRTM and IASI

2016 ◽  
Author(s):  
Xavier Calbet ◽  
Niobe Peinado-Galan ◽  
Pilar Ripodas ◽  
Tim Trent ◽  
Ruud Dirksen ◽  
...  
Keyword(s):  
Radiative Transfer Model ◽  
Transfer Model ◽  
Climate Data ◽  
Satellite Measurements ◽  
Night Time ◽  
Upper Troposphere ◽  
Data Record ◽  
Water Vapour Absorption ◽  
Reference Measurements ◽  
Dry Bias

Abstract. Radiosonde soundings from the GRUAN data record are shown to be consistent with IASI measured radiances via the LBLRTM radiative transfer model in the part of the spectrum that is mostly affected by water vapour absorption in the upper troposphere (from 700 hPa up). This result is key to have consistency between radiosonde and satellite measurements for climate data records, since GRUAN, IASI and LBLRTM constitute reference measurements in each of their fields. This is specially the case for night time radiosonde measurements. Although the sample size is small (16 cases), day time GRUAN radiosonde measurements seem to have a small dry bias of 2.5 % in absolute terms of relative humidity, located mainly in the upper troposphere, with respect to LBLRTM and IASI.

scholarly journals Physical behaviour of anthropogenic light propagation into the nocturnal environment

2015 ◽  
Vol 370 (1667) ◽  
pp. 20140117 ◽  
Author(s):  
Martin Aubé
Keyword(s):  
Radiative Transfer ◽  
Natural Environment ◽  
Spectral Power ◽  
Radiative Transfer Model ◽  
City Centre ◽  
Light Pollution ◽  
Transfer Model ◽  
Light Sources ◽  
Night Time ◽  
The Impact

Propagation of artificial light at night (ALAN) in the environment is now known to have non negligible consequences on fauna, flora and human health. These consequences depend on light levels and their spectral power distributions, which in turn rely on the efficiency of various physical processes involved in the radiative transfer of this light into the atmosphere and its interactions with the built and natural environment. ALAN can affect the living organisms by direct lighting and indirect lighting (scattered by the sky and clouds and/or reflected by local surfaces). This paper mainly focuses on the behaviour of the indirect light scattered under clear sky conditions. Various interaction processes between anthropogenic light sources and the natural environment are discussed. This work mostly relies on a sensitivity analysis conducted with the light pollution radiative transfer model, Illumina (Aubé et al . 2005 Light pollution modelling and detection in a heterogeneous environment: toward a night-time aerosol optical depth retrieval method. In Proc. SPIE 2005, vol. 5890, San Diego, California, USA). More specifically, the impact of (i) the molecular and aerosol scattering and absorption, (ii) the second order of scattering, (iii) the topography and obstacle blocking, (iv) the ground reflectance and (v) the spectrum of light devices and their angular emission functions are examined. This analysis considers different behaviour as a function of the distance from the city centre, along with different zenith viewing angles in the principal plane.

scholarly journals Calibration and Validation of Antenna and Brightness Temperatures from Metop-C Advanced Microwave Sounding Unit-A (AMSU-A)

2020 ◽  
Vol 12 (18) ◽  
pp. 2978
Author(s):  
Banghua Yan ◽  
Junye Chen ◽  
Cheng-Zhi Zou ◽  
Khalil Ahmad ◽  
Haifeng Qian ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Data Quality ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Model Simulations ◽  
Calibration And Validation ◽  
Microwave Sounding Unit ◽  
Data Record ◽  
Microwave Sounding ◽  
Advanced Microwave Sounding Unit

This study carries out the calibration and validation of Antenna Temperature Data Record (TDR) and Brightness Temperature Sensor Data Record (SDR) data from the last National Oceanic and Atmospheric Administration (NOAA) Advanced Microwave Sounding Unit-A (AMSU-A) flown on the Meteorological Operational satellite programme (MetOp)-C satellite. The calibration comprises the selection of optimal space view positions for the instrument and the determination of coefficients in calibration equations from the Raw Data Record (RDR) to TDR and SDR. The validation covers the analyses of the instrument noise equivalent differential temperature (NEDT) performance and the TDR and SDR data quality from the launch until 15 November 2019. In particular, the Metop-C data quality is assessed by comparing to radiative transfer model simulations and observations from Metop-A/B AMSU-A, respectively. The results demonstrate that the on-orbit instrument NEDTs have been stable since launch and continue to meet the specifications at most channels except for channel 3, whose NEDT exceeds the specification after April 2019. The quality of the Metop-C AMSU-A data for all channels except channel 3 have been reliable since launch. The quality at channel 3 is degraded due to the noise exceeding the specification. Compared to its TDR data, the Metop-C AMSU-A SDR data exhibit a reduced and more symmetric scan angle-dependent bias against radiative transfer model simulations, demonstrating the great performance of the TDR to SDR conversion coefficients. Additionally, the Metop-C AMSU-A data quality agrees well with Metop-A/B AMSU-A data, with an averaged difference in the order of 0.3 K, which is confirmed based on Simultaneous Nadir Overpass (SNO) inter-sensor comparisons between Metop-A/B/C AMSU-A instruments via either NOAA-18 or NOAA-19 AMSU-A as a transfer.

scholarly journals RADIATIVE TRANSFER MODEL SIMULATIONS TO DETERMINE THE NIGHT TIME FOG DETECTION THRESHOLD

2018 ◽  
Vol XLII-5 ◽  
pp. 511-517
Author(s):  
S. Gaurav ◽  
P. Jindal
Keyword(s):  
Radiative Transfer ◽  
Satellite Image ◽  
Detection Threshold ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Night Time ◽  
Northern India ◽  
Microphysical Properties ◽  
Spectral Channels ◽  
Fog Detection

<p><strong>Abstract.</strong> Every winter the Indo-Gangetic plains (IGP) of northern India are severely impacted both socially and economically by fog. For night time fog detection, visible imagery cannot be used. Also, as emissions from ground and fog is almost similar in thermal infrared (TIR, 10.8<span class="thinspace"></span>&amp;mu;m) channel, TIR channel cannot help in identifying fog. However, emission in middle infrared (MIR, 3.9<span class="thinspace"></span>&amp;mu;m) channel is less than emission in TIR channel over foggy area. Therefore, brightness temperature difference (BTD) between TIR and MIR is positive during night time over fog area. This BTD technique cannot be directly used during day time as MIR channel is contaminated by solar radiations. In the present work, a spectral sensitivity analysis study has been done for these two spectral channels using radiative transfer model (RTM) simulations to determine a threshold BTD for night time fog detection. SBDART (Santa Barbara DISORT Radiative Transfer) model was used for this study to simulate brightness temperatures (BT). The RTM simulations of BT of the two spectral channels was carried out for different fog microphysical characteristics like fog optical depth (FOD) and fog droplet size (Re). The fog episode of January 2018 over IGP was studied by applying threshold BTD obtained from simulation results for INSAT-3D data. A threshold BTD value ><span class="thinspace"></span>5<span class="thinspace"></span>K detected night time fog over IGP with good accuracy. The threshold BTD obtained from satellite image is compared with different cases established from simulation result which gave idea about microphysical properties of fog over IGP during winter seasons.</p>

scholarly journals Ash and ice clouds during the Mt. Kelud Feb 2014 eruption as interpreted from IASI and AVHRR/3 observations

2016 ◽  
Author(s):  
Arve Kylling
Keyword(s):  
Radiative Transfer ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Ice Clouds ◽  
Ice Cloud ◽  
Atmospheric Sounding ◽  
2014 Eruption ◽  
Very High ◽  
Ash Cloud ◽  
Absorption Technique

Abstract. During the Mt. Kelud Feb 2014 eruption the ash cloud was detectable on 13–14 Feb in the infrared with the reverse absorption technique by, for example, the Advanced Very High Resolution Radiometer (AVHRR/3). The Infrared Atmospheric Sounding Interferometer (IASI) observed the ash cloud also on 15 Feb when AVHRR did not detect any ash signal. The differences between ash detection with AVHRR/3 and IASI are discussed and the reasons for the differences supported with radiative transfer modelling. The effect of conccurent ice clouds on the ash detection and the ash signal in the IASI measurements is demonstrated. Specifically, a radiative transfer model is used to simulate IASI spectra with ash only, with ice cloud only and with both ash and ice clouds. It is shown that modelled IASI spectra with ash and ice clouds better reproduce the measured IASI spectra than ash only or ice only modelled spectra. The ash and ice modelled spectra that best reproduce the IASI spectra contain about a factor of 14 less ash than the ash only spectra that come closest to reproducing the measured spectra.

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