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 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 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 The Earth Surface Mineral Dust Source Investigation: An Earth Science Imaging Spectroscopy Mission

2020 ◽  
Author(s):  
Robert O. Green ◽  
Natalie Mahowald ◽  
Charlene Ung ◽  
David R. Thompson ◽  
Lori Bator ◽  
...  
Keyword(s):  
Mineral Dust ◽  
Earth Science ◽  
Imaging Spectroscopy ◽  
Earth Surface ◽  
Dust Source ◽  
The Earth ◽  
Surface Mineral

scholarly journals Water vapour foreign-continuum absorption in near-infrared windows from laboratory measurements

2012 ◽  
Vol 370 (1968) ◽  
pp. 2557-2577 ◽  
Author(s):  
Igor V. Ptashnik ◽  
Robert A. McPheat ◽  
Keith P. Shine ◽  
Kevin M. Smith ◽  
R. Gary Williams
Keyword(s):  
Water Vapour ◽  
Near Infrared ◽  
Prediction Models ◽  
Weather Prediction ◽  
Pair Interaction ◽  
Atmospheric Conditions ◽  
Laboratory Measurements ◽  
Atmospheric Absorption ◽  
Clear Sky ◽  
Long Time

For a long time, it has been believed that atmospheric absorption of radiation within wavelength regions of relatively high infrared transmittance (so-called ‘windows’) was dominated by the water vapour self-continuum, that is, spectrally smooth absorption caused by H 2 O−H 2 O pair interaction. Absorption due to the foreign continuum (i.e. caused mostly by H 2 O−N 2 bimolecular absorption in the Earth's atmosphere) was considered to be negligible in the windows. We report new retrievals of the water vapour foreign continuum from high-resolution laboratory measurements at temperatures between 350 and 430 K in four near-infrared windows between 1.1 and 5 μm (9000–2000 cm −1 ). Our results indicate that the foreign continuum in these windows has a very weak temperature dependence and is typically between one and two orders of magnitude stronger than that given in representations of the continuum currently used in many climate and weather prediction models. This indicates that absorption owing to the foreign continuum may be comparable to the self-continuum under atmospheric conditions in the investigated windows. The calculated global-average clear-sky atmospheric absorption of solar radiation is increased by approximately 0.46 W m −2 (or 0.6% of the total clear-sky absorption) by using these new measurements when compared with calculations applying the widely used MTCKD (Mlawer–Tobin–Clough–Kneizys–Davies) foreign-continuum model.

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 Matching radiative transfer models and radiosonde data from the EPS/Metop Sodankylä campaign to IASI measurements

2011 ◽  
Vol 4 (6) ◽  
pp. 1177-1189 ◽  
Author(s):  
X. Calbet ◽  
R. Kivi ◽  
S. Tjemkes ◽  
F. Montagner ◽  
R. Stuhlmann
Keyword(s):  
Radiative Transfer ◽  
Water Vapour ◽  
Spectral Region ◽  
Radiosonde Data ◽  
Radiative Transfer Models ◽  
Frost Point ◽  
Instrument Noise ◽  
Atmospheric State ◽  
Dry Bias ◽  
Transfer Models

Abstract. Radiances observed from IASI are compared to calculated ones. Calculated radiances are obtained using several radiative transfer models (OSS, LBLRTM v11.3 and v11.6) on best estimates of the atmospheric state vectors. The atmospheric state vectors are derived from cryogenic frost point hygrometer and humidity dry bias corrected RS92 measurements flown on sondes launched 1 h and 5 min before IASI overpass time. The temperature and humidity best estimate profiles are obtained by interpolating or extrapolating these measurements to IASI overpass time. The IASI observed and calculated radiances match to within one sigma IASI instrument noise in the spectral region where water vapour is a strong absorber (wavenumber, ν, in the range of 1500 ≤ ν ≤ 1570 and 1615 ≤ ν ≤ 1800 cm−1).

Optical design of the Earth Surface Mineral Dust Source Investigation (EMIT) imaging spectrometer

2020 ◽  
Author(s):  
Christine L. Bradley ◽  
Erik Thingvold ◽  
Lori B. Moore ◽  
Justin M. Haag ◽  
Nasrat A. Raouf ◽  
...  
Keyword(s):  
Mineral Dust ◽  
Optical Design ◽  
Earth Surface ◽  
Dust Source ◽  
Imaging Spectrometer ◽  
The Earth ◽  
Surface Mineral

scholarly journals Effects of 3D Thermal Radiation on Cloud Development

2016 ◽  
Author(s):  
Carolin Klinger ◽  
Bernhard Mayer ◽  
Fabian Jakub ◽  
Tobias Zinner ◽  
Seungbu Park ◽  
...  
Keyword(s):  
Thermal Radiation ◽  
Horizontal Resolution ◽  
Cumulus Cloud ◽  
Local Cooling ◽  
Convective Clouds ◽  
Heating And Cooling ◽  
Large Eddy ◽  
Cloud Development ◽  
Cloud Tops ◽  
Les Model

Abstract. We investigate the effects of thermal radiation on cloud development in an idealized setup in large-eddy simulations with the UCLA-LES model. We investigate single convective clouds (driven by a warm bubble) and a large cumulus cloud field at 50 m horizontal resolution. We compare the newly developed 3D "neighboring column approximation" with the independent column approximation and a simulation without radiation and their respective impact on clouds. Thermal radiation causes strong local cooling at cloud tops accompanied by a modest warming at the cloud bottom, and in the case of a 3D scheme, also cloud side cooling. 3D thermal radiation causes systematically larger cooling when averaged over the model domain. In order to investigate the effects of local cooling on the clouds and to separate these local effects from a systematically larger cooling effect in the modeling domain, we apply the radiative transfer solutions in different ways. The direct effect of heating and cooling at the clouds is applied (interactive thermal radiation) in a first simulation. Furthermore, a slab-averaged applications of the 1D and 3D radiation is used to study the effect of local cloud radiation as opposed to the domain averaged effect. These simulations exhibit a cooling profile, with stronger cooling in the cloudy layers. In a final setup, we replace the radiation simulation by a uniform cooling of 2.6 K/d. For the simulations of isolated single cloud, or the cumulus cloud field with interactive radiation, we find that thermal radiation changes cloud circulation, by causing stronger updrafts and stronger subsiding shells. In our cumulus cloud field simulation we find that interactive radiation, acting locally on clouds enhances the circulation compared to the averaged radiation applications. In addition we find that thermal radiation triggers the organization of clouds. Comparing the effects of 3D and 1D thermal radiation, we find that organization effects of 3D thermal radiation are usually stronger than the 1D counterpart (either interactive or averaged). Interactive radiation leads to an earlier onset of the organization both in 1D and 3D compared to the averaged radiation application. Applying a constant cooling to the simulations leads to a similar development of the cloud field as in the case of averaged radiation, but less water condenses overall in the simulation. Generally, clouds contain more liquid water if radiation is accounted for. Furthermore, thermal radiation enhances turbulence and mixing as well as the size and lifetime of clouds. Interactive thermal radiation produces larger clouds with longer lifetimes.

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