scholarly journals Boundary layer water vapour statistics from high-spatial-resolution spaceborne imaging spectroscopy

2021 ◽  
Author(s):  
Mark T. Richardson ◽  
David R. Thompson ◽  
Marcin J. Kurowski ◽  
Matthew D. Lebsock
Keyword(s):  
Water Vapour ◽  
Imaging Spectroscopy ◽  
Optimal Estimation ◽  
Horizontal Resolution ◽  
Mineral Surfaces ◽  
Eddy Simulation ◽  
New Information ◽  
Planetary Boundary Layers ◽  
Surface Mineral ◽  
Shortwave Infrared

Abstract. Daytime clear-sky total column water vapour (TCWV) is commonly retrieved from visible and shortwave infrared reflectance (VSWIR) measurements, and upcoming missions such as the Earth Surface Mineral Dust Source Investigation (EMIT) will offer unprecedented horizontal resolution of order 30–80 m. We provide evidence that for convective planetary boundary layers (PBLs), spatial variability in TCWV corresponds to variability in PBL water vapour. Using synthetic optimal estimation retrievals applied to Large Eddy Simulation (LES) output, we show that EMIT can retrieve horizontal variability in PBL water vapour, provided that the domain surface is uniformly composed of either vegetated surfaces or mineral surfaces. Random retrieval errors are easily quantified and removed, but biases from −7 % to +34 % remain in retrieved spatial standard deviation and are primarily related to the retrieval’s assumed atmospheric profiles. Future retrieval development could greatly mitigate these errors. Finally, we account for changing solar zenith angle (SZA) from 15–60° and show that the non-vertical solar path destroys the correspondence between footprint retrieved TCWV and the true TCWV directly above that footprint. Even at the 250 m horizontal resolution regularly obtained by current sensors, the derived maps correspond poorly to true TCWV at the pixel-scale, with r2 < 0.6 at SZA = 30°. However, the derived histograms of TCWV in an area are closely related to the true histograms of TCWV at the nominal footprint resolution. Upcoming VSWIR instruments, primarily targeting surface properties, can therefore offer new information on PBL water vapour spatial statistics to the atmospheric community.

scholarly journals Boundary layer water vapour statistics from high-spatial-resolution spaceborne imaging spectroscopy

2021 ◽  
Vol 14 (8) ◽  
pp. 5555-5576
Author(s):  
Mark T. Richardson ◽  
David R. Thompson ◽  
Marcin J. Kurowski ◽  
Matthew D. Lebsock
Keyword(s):  
Water Vapour ◽  
Imaging Spectroscopy ◽  
Horizontal Resolution ◽  
Mineral Surfaces ◽  
Eddy Simulation ◽  
New Information ◽  
Planetary Boundary Layers ◽  
Surface Mineral ◽  
Shortwave Infrared ◽  
Observing System Simulation Experiment

Abstract. Daytime clear-sky total column water vapour (TCWV) is commonly retrieved from visible and shortwave infrared reflectance (VSWIR) measurements, and modern missions such as the upcoming Earth Surface Mineral Dust Source Investigation (EMIT) offer unprecedented horizontal resolution of order 30–80 m. We provide evidence that for convective planetary boundary layers (PBLs), spatial variability in TCWV corresponds to variability in PBL water vapour. Using an observing system simulation experiment (OSSE) applied to large eddy simulation (LES) output, we show that EMIT can retrieve horizontal variability in PBL water vapour, provided that the domain surface is uniformly composed of either vegetated surfaces or mineral surfaces. Random retrieval errors are easily quantified and removed, but biases from −7 % to +34 % remain in retrieved spatial standard deviation and are primarily related to the retrieval's assumed atmospheric profiles. Future retrieval development could greatly mitigate these errors. Finally, we account for changing solar zenith angle (SZA) from 15 to 60∘ and show that the non-vertical solar path destroys the correspondence between footprint-retrieved TCWV and the true TCWV directly above that footprint. Even at the 250 m horizontal resolution regularly obtained by current sensors, the derived maps correspond poorly to true TCWV at the pixel scale, with r2<0.6 at SZA=30∘. However, the derived histograms of TCWV in an area are closely related to the true histograms of TCWV at the nominal footprint resolution. Upcoming VSWIR instruments, primarily targeting surface properties, can therefore offer new information on PBL water vapour spatial statistics to the atmospheric community.

scholarly journals New sampling strategy mitigates a solar-geometry-induced bias in sub-kilometre vapour scaling statistics derived from imaging spectroscopy

2022 ◽  
Vol 15 (1) ◽  
pp. 117-129
Author(s):  
Mark T. Richardson ◽  
David R. Thompson ◽  
Marcin J. Kurowski ◽  
Matthew D. Lebsock
Keyword(s):  
Water Vapour ◽  
Imaging Spectroscopy ◽  
Sampling Strategy ◽  
Horizontal Resolution ◽  
Noise Model ◽  
Dust Source ◽  
Clear Sky ◽  
Large Eddy ◽  
Instrument Noise ◽  
Surface Mineral

Abstract. Upcoming spaceborne imaging spectrometers will retrieve clear-sky total column water vapour (TCWV) over land at a horizontal resolution of 30–80 m. Here we show how to obtain, from these retrievals, exponents describing the power-law scaling of sub-kilometre horizontal variability in clear-sky bulk planetary boundary layer (PBL) water vapour (q) accounting for realistic non-vertical sunlight paths. We trace direct solar beam paths through large eddy simulations (LES) of shallow convective PBLs and show that retrieved 2-D water vapour fields are “smeared” in the direction of the solar azimuth. This changes the horizontal spatial scaling of the field primarily in that direction, and we address this by calculating exponents perpendicular to the solar azimuth, that is to say flying “across” the sunlight path rather than “towards” or “away” from the Sun. Across 23 LES snapshots, at solar zenith angle SZA = 60∘ the mean bias in calculated exponent is 38 ± 12 % (95 % range) along the solar azimuth, while following our strategy it is 3 ± 9 % and no longer significant. Both bias and root-mean-square error decrease with lower SZA. We include retrieval errors from several sources, including (1) the Earth Surface Mineral Dust Source Investigation (EMIT) instrument noise model, (2) requisite assumptions about the atmospheric thermodynamic profile, and (3) spatially nonuniform aerosol distributions. By only considering the direct beam, we neglect 3-D radiative effects such as light scattered into the field of view by nearby clouds. However, our proposed technique is necessary to counteract the direct-path effect of solar geometries and obtain unique information about sub-kilometre PBL q scaling from upcoming spaceborne spectrometer missions.

scholarly journals New sampling strategy removes imaging spectroscopy solar-smearing bias in sub-km vapour scaling statistics

2021 ◽  
Author(s):  
Mark T. Richardson ◽  
David R. Thompson ◽  
Marcin J. Kurowski ◽  
Matthew D. Lebsock
Keyword(s):  
Water Vapour ◽  
Imaging Spectroscopy ◽  
Sampling Strategy ◽  
Horizontal Resolution ◽  
Noise Model ◽  
Dust Source ◽  
Clear Sky ◽  
Large Eddy ◽  
Instrument Noise ◽  
Surface Mineral

Abstract. Upcoming spaceborne imaging spectrometers will allow retrieval of total column water vapour (TCWV) over land at horizontal resolution of 30–80 m. Here we show how to obtain, from these retrievals, exponents describing the power-law scaling of sub-km horizontal variability in clear-sky bulk planetary boundary layer (PBL) water vapour (q). Using large-eddy simulations (LES) of shallow convective PBLs we show how sunlight entering the PBL up to several km away from the footprint location degrades estimates of these exponents. We address this by calculating exponents perpendicular to the solar azimuth, that is to say flying “across” the sunlight path rather than “towards” or “away” from the Sun. Across 23 LES snapshots, at SZA = 60° the mean bias in calculated exponent is 38 ± 12 % (95 % range) along the solar azimuth, while following our strategy it is 3 ± 9 % and no longer significant. Both bias and root-mean-square error RMSE decrease with lower SZA. We include retrieval errors from several sources including: (1) the Earth Surface Mineral Dust Source Investigation (EMIT) instrument noise model, (2) requisite assumptions about the atmospheric thermodynamic profile, and (3) spatially nonuniform aerosol distributions. This technique can be used to obtain unique information about sub-km PBL q scaling from upcoming spaceborne spectrometer missions, while mitigating errors due to challenging solar geometries.

scholarly journals Validation of stratospheric water vapour measurements from the airborne microwave radiometer AMSOS

2008 ◽  
Vol 8 (1) ◽  
pp. 1635-1671 ◽  
Author(s):  
S. C. Müller ◽  
N. Kämpfer ◽  
D. G. Feist ◽  
A. Haefele ◽  
M. Milz ◽  
...  
Keyword(s):  
Water Vapour ◽  
Microwave Radiometer ◽  
Estimation Method ◽  
Optimal Estimation ◽  
Horizontal Resolution ◽  
Polar Regions ◽  
Upper Troposphere ◽  
Vertical Range ◽  
Stratospheric Water Vapour

Abstract. We present the validation of a water vapour dataset obtained by the Airborne Microwave Stratospheric Observing System AMSOS, a passive microwave radiometer operating at 183 GHz. Vertical profiles are retrieved from spectra by an optimal estimation method. The useful vertical range lies in the upper troposphere up to the mesosphere with an altitude resolution of 8 to 16 km and a horizontal resolution of about 57 km. Flight campaigns were performed once a year from 1998 to 2006 measuring the latitudinal distribution of water vapour from the tropics to the polar regions. The obtained profiles show clearly the main features of stratospheric water vapour in all latitudinal regions. Data are validated against a set of instruments comprising satellite, ground-based, airborne remote sensing and in-situ instruments. It appears that AMSOS profiles have a dry bias of 3–20%, when compared to satellite experiments. A good agreement with a difference of 3.3% was found between AMSOS and in-situ hygrosondes FISH and FLASH and an excellent matching of the lidar measurements from the DIAL instrument in the short overlap region in the upper troposphere.

scholarly journals Validation of stratospheric water vapour measurements from the airborne microwave radiometer AMSOS

2008 ◽  
Vol 8 (12) ◽  
pp. 3169-3183 ◽  
Author(s):  
S. C. Müller ◽  
N. Kämpfer ◽  
D. G. Feist ◽  
A. Haefele ◽  
M. Milz ◽  
...  
Keyword(s):  
Water Vapour ◽  
Microwave Radiometer ◽  
Estimation Method ◽  
Optimal Estimation ◽  
Horizontal Resolution ◽  
Polar Regions ◽  
Upper Troposphere ◽  
Vertical Range ◽  
Stratospheric Water Vapour

Abstract. We present the validation of a water vapour dataset obtained by the Airborne Microwave Stratospheric Observing System AMSOS, a passive microwave radiometer operating at 183 GHz. Vertical profiles are retrieved from spectra by an optimal estimation method. The useful vertical range lies in the upper troposphere up to the mesosphere with an altitude resolution of 8 to 16 km and a horizontal resolution of about 57 km. Flight campaigns were performed once a year from 1998 to 2006 measuring the latitudinal distribution of water vapour from the tropics to the polar regions. The obtained profiles show clearly the main features of stratospheric water vapour in all latitudinal regions. Data are validated against a set of instruments comprising satellite, ground-based, airborne remote sensing and in-situ instruments. It appears that AMSOS profiles have a dry bias of 0 to –20%, when compared to satellite experiments. Also a comparison between AMSOS and in-situ hygrosondes FISH and FLASH have been performed. A matching in the short overlap region in the upper troposphere of the lidar measurements from the DIAL instrument and the AMSOS dataset allowed water vapour profiling from the middle troposphere up to the mesosphere.

scholarly journals Algorithm theoretical baseline for formaldehyde retrievals from S5P TROPOMI and from the QA4ECV project

2018 ◽  
Vol 11 (4) ◽  
pp. 2395-2426 ◽  
Author(s):  
Isabelle De Smedt ◽  
Nicolas Theys ◽  
Huan Yu ◽  
Thomas Danckaert ◽  
Christophe Lerot ◽  
...  
Keyword(s):  
Near Infrared ◽  
Horizontal Resolution ◽  
Retrieval Algorithm ◽  
User Requirements ◽  
Vertical Column ◽  
Ultraviolet Range ◽  
Order Of Magnitude ◽  
Shortwave Infrared ◽  
Double Channel ◽  
The Eu

Abstract. On board the Copernicus Sentinel-5 Precursor (S5P) platform, the TROPOspheric Monitoring Instrument (TROPOMI) is a double-channel, nadir-viewing grating spectrometer measuring solar back-scattered earthshine radiances in the ultraviolet, visible, near-infrared, and shortwave infrared with global daily coverage. In the ultraviolet range, its spectral resolution and radiometric performance are equivalent to those of its predecessor OMI, but its horizontal resolution at true nadir is improved by an order of magnitude. This paper introduces the formaldehyde (HCHO) tropospheric vertical column retrieval algorithm implemented in the S5P operational processor and comprehensively describes its various retrieval steps. Furthermore, algorithmic improvements developed in the framework of the EU FP7-project QA4ECV are described for future updates of the processor. Detailed error estimates are discussed in the light of Copernicus user requirements and needs for validation are highlighted. Finally, verification results based on the application of the algorithm to OMI measurements are presented, demonstrating the performances expected for TROPOMI.

scholarly journals Optimal Estimation MSG-SEVIRI Clear-Sky Total Column Water Vapour Retrieval Using the Split Window Difference

Atmosphere ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1256
Author(s):  
Jan El Kassar ◽  
Cintia Carbajal Henken ◽  
Rene Preusker ◽  
Jürgen Fischer
Keyword(s):  
Water Vapour ◽  
Large Scale ◽  
Pearson Correlation ◽  
Microwave Radiometer ◽  
Optimal Estimation ◽  
Forward Model ◽  
Observation Data ◽  
Atmospheric Conditions ◽  
Uncertainty Estimates ◽  
Total Column

A new algorithm for the retrieval of day-time total column water vapour (TCWV) from measurements of a MSG-SEVIRI (Meteosat Second Generation Spinning Enhanced Visible and Infrared Imager) instrument is presented. The retrieval is based on a forward operator, at the core of which lies Radiative Transfer for TIROS Operational Vertical Sounder (RTTOV). This forward model relates TCWV and surface temperature to brightness temperatures in the split window at 11 and 12µm with the use of a first guess for temperature and humidity profiles from the ERA5 reanalysis. The forward model is then embedded in a full Optimal Estimation (OE) method, which yields pixel by pixel uncertainty estimates and performance indicators. The algorithm is applicable to any instrument which features the split window configuration, given a first guess for atmospheric conditions (i.e., from NWP) and an estimate of surface emissivity at 11 µm. The algorithm was developed within the framework of RealPEP (Near-Realtime Quantitative Precipitation Estimation and Prediction) in which the advancement of the estimation and nowcasting of extreme precipitation and flooding in Germany are studied. Thus, processing and validation has been limited to the German domain. Three independent ground-based TCWV observation data sets were used as reference, i.e., AERONET (Aerosol Robotic Network), GNSS Germany (Global Navigation Satellite System) and measurements from two MWR (Microwave Radiometer) sites. The validation concludes with good agreement, with absolute biases between 0.11 and 2.85 kg/m2, root mean square deviations (rmsds) between 1.63 and 3.24 kg/m2 and Pearson correlation coefficients ranging from 0.96 to 0.98. The retrievals uncertainty estimates were evaluated against AERONET. The comparison suggests that, in sum, uncertainties are estimated well, while still some error sources seem to be over- and underestimated. In limited case studies it could be shown that SEVIRI TCWV is capable to both display large scale variabilities in water vapour fields and reproduce the daily course of water vapour exposed by ground-based observations.

Determination of the viability of retinispora (Hinoki cypress) seeds using shortwave infrared hyperspectral imaging spectroscopy

2020 ◽  
Vol 28 (2) ◽  
pp. 70-80 ◽  
Author(s):  
Perez Mukasa ◽  
Collins Wakholi ◽  
Akbar Faqeerzada Mohammad ◽  
Eunsoo Park ◽  
Jayoung Lee ◽  
...  
Keyword(s):  
Discriminant Analysis ◽  
Hyperspectral Imaging ◽  
Imaging Spectroscopy ◽  
Partial Least Square ◽  
Least Square ◽  
Successive Projections Algorithm ◽  
Hinoki Cypress ◽  
Sorting System ◽  
Shortwave Infrared ◽  
Successive Projections

The combination of hyperspectral imaging with multivariate data analysis methods has recently been applied to develop a nondestructive technique, required to determine the seed viability of artificially aged vegetable and cereal seeds. In this study, the potential of shortwave infrared hyperspectral imaging to determine the viability of naturally aged seeds was investigated and thereafter a model for online seed sorting system was developed. The hyperspectral images of 400 Hinoki cypress tree seeds were acquired, and germination tests were conducted for viability confirmation, which indicated 31.5% of the viable seeds. Partial least square discriminant analysis models with 179 variables in the wavelength region of 1000–1800 nm were developed with a maximum model accuracy of 98.4% and 93.8% in both the calibration and validation sets, respectively. The partial least square discriminant analysis beta coefficient revealed the key wavelengths to differentiate viable from nonviable seeds, determined based on the differences in the chemical compositions of the seeds, including their lipid and fatty acid contents, which may control the germination ability of the seeds. The most effective wavelengths were selected using two model-based variable selection methods (i.e., the variable importance of projection (15 variables) and the successive projections algorithm (8 variables)) to develop the model. The successive projections algorithm wavelength selection method was considered to develop a viability model, and its application to the raw data resulted in a prediction accuracy of 94.7% in the calibration set and 92.2% in the validation set. These results demonstrate the potential of shortwave infrared hyperspectral imaging spectroscopy as a powerful nondestructive method to determine the viability of Hinoki cypress seeds. This method could be applied to develop an online seed sorting system for seed companies and nurseries.

Remote sounding of atmospheric temperature from satellites IV. The selective chopper radiometer for Nimbus 5

1973 ◽  
Vol 334 (1597) ◽  
pp. 149-170 ◽  
Keyword(s):  
Water Vapour ◽  
Near Infrared ◽  
Far Infrared ◽  
Atmospheric Temperature ◽  
Horizontal Resolution ◽  
Ice Clouds ◽  
New Instrument ◽  
Remote Sounding ◽  
Complete Set ◽  
High Clouds

An improved version of the selective chopper radiometer which has successfully flown for three years on the Nimbus 4 satellite has been built for the Nimbus 5 satellite which was launched in December 1972. The new instrument has 16 channels, eight of which observe emission from the 15 μm band of carbon dioxide for remote temperature sounding, two observe emission from water-vapour and ice clouds in the far infrared, one observes emission from low atmospheric water-vapour, three are in spectral regions where the atmosphere is substantially transparent, i.e. window regions, and two observe reflected sunlight from high clouds near to 2.7 μm in the near infrared. The horizontal resolution of the instrument is about 25 km and a complete set of measurements is made every 4 s. The design, construction and calibration of the instrument are described.

scholarly journals Retrieval of volcanic SO<sub>2</sub> from HIRS/2 using optimal estimation

2017 ◽  
Vol 10 (7) ◽  
pp. 2687-2702 ◽  
Author(s):  
Georgina M. Miles ◽  
Richard Siddans ◽  
Roy G. Grainger ◽  
Alfred J. Prata ◽  
Bradford Fisher ◽  
...  
Keyword(s):  
Water Vapour ◽  
Computational Cost ◽  
Optimal Estimation ◽  
Previous Method ◽  
Aerosol Model ◽  
Water Ice ◽  
Ice Cloud ◽  
Retrieval Scheme ◽  
Initial Comparison ◽  
Daily Sampling

Abstract. We present an optimal-estimation (OE) retrieval scheme for stratospheric sulfur dioxide from the High-Resolution Infrared Radiation Sounder 2 (HIRS/2) instruments on the NOAA and MetOp platforms, an infrared radiometer that has been operational since 1979. This algorithm is an improvement upon a previous method based on channel brightness temperature differences, which demonstrated the potential for monitoring volcanic SO2 using HIRS/2. The Prata method is fast but of limited accuracy. This algorithm uses an optimal-estimation retrieval approach yielding increased accuracy for only moderate computational cost. This is principally achieved by fitting the column water vapour and accounting for its interference in the retrieval of SO2. A cloud and aerosol model is used to evaluate the sensitivity of the scheme to the presence of ash and water/ice cloud. This identifies that cloud or ash above 6 km limits the accuracy of the water vapour fit, increasing the error in the SO2 estimate. Cloud top height is also retrieved. The scheme is applied to a case study event, the 1991 eruption of Cerro Hudson in Chile. The total erupted mass of SO2 is estimated to be 2300 kT ± 600 kT. This confirms it as one of the largest events since the 1991 eruption of Pinatubo, and of comparable scale to the Northern Hemisphere eruption of Kasatochi in 2008. This retrieval method yields a minimum mass per unit area detection limit of 3 DU, which is slightly less than that for the Total Ozone Mapping Spectrometer (TOMS), the only other instrument capable of monitoring SO2 from 1979 to 1996. We show an initial comparison to TOMS for part of this eruption, with broadly consistent results. Operating in the infrared (IR), HIRS has the advantage of being able to measure both during the day and at night, and there have frequently been multiple HIRS instruments operated simultaneously for better than daily sampling. If applied to all data from the series of past and future HIRS instruments, this method presents the opportunity to produce a comprehensive and consistent volcanic SO2 time series spanning over 40 years.

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