Three Dimensional Radiative Effects in Passive Millimeter/Sub-Millimeter All-sky Observations
This study was conducted to quantify the errors prompted by neglecting three-dimensional (3D) effects, i.e., beam-filling and horizontal photon transport effects, at millimeter/sub-millimeter wavelengths. This paper gives an overview of the 3D effects that impact ice cloud retrievals of both current...
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| Format: | Article |
| Language: | English |
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MDPI AG
2020-02-01
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| Series: | Remote Sensing |
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| Online Access: | https://www.mdpi.com/2072-4292/12/3/531 |
| _version_ | 1819289372775677952 |
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| author | Vasileios Barlakas Patrick Eriksson |
| author_facet | Vasileios Barlakas Patrick Eriksson |
| author_sort | Vasileios Barlakas |
| collection | DOAJ |
| description | This study was conducted to quantify the errors prompted by neglecting three-dimensional (3D) effects, i.e., beam-filling and horizontal photon transport effects, at millimeter/sub-millimeter wavelengths. This paper gives an overview of the 3D effects that impact ice cloud retrievals of both current and proposed (Ice Cloud Imager) satellite instruments operating at frequencies of ≈186.3 and ≈668 GHz. The 3D synthetic scenes were generated from two-dimensional (2D) CloudSat (Cloud Satellite) observations over the tropics and mid-latitudes using a stochastic approach. By means of the Atmospheric Radiative Transfer Simulator (ARTS), three radiative transfer simulations were carried out: one 3D, one independent beam approximation (IBA), and one-dimensional (1D). The comparison between the 3D and IBA simulations revealed a small horizontal photon transport effect, with IBA simulations introducing mostly random errors and a slight overestimation (below 1 K). However, performing 1D radiative transfer simulations results in a significant beam-filling effect that increases primarily with frequency, and secondly, with footprint size. For a sensor footprint size of 15 km, the errors induced by neglecting domain heterogeneities yield root mean square errors of up to ≈4 K and ≈13 K at 186.3 GHz and 668 GHz, respectively. However, an instrument operating at the same frequencies, but with a much smaller footprint size, i.e., 6 km, is subject to smaller uncertainties, with a root mean square error of ≈2 K at 186.3 GHz and ≈7.1 K at 668 GHz. When designing future satellite instruments, this effect of footprint size on modeling uncertainties should be considered in the overall error budget. The smallest possible footprint size should be a priority for future sub-millimeter observations in light of these results. |
| first_indexed | 2024-12-24T03:05:48Z |
| format | Article |
| id | doaj.art-068a4916fd6142839f4919aa6a9c72a8 |
| institution | Directory Open Access Journal |
| issn | 2072-4292 |
| language | English |
| last_indexed | 2024-12-24T03:05:48Z |
| publishDate | 2020-02-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Remote Sensing |
| spelling | doaj.art-068a4916fd6142839f4919aa6a9c72a82022-12-21T17:18:00ZengMDPI AGRemote Sensing2072-42922020-02-0112353110.3390/rs12030531rs12030531Three Dimensional Radiative Effects in Passive Millimeter/Sub-Millimeter All-sky ObservationsVasileios Barlakas0Patrick Eriksson1Department of Space, Earth and Environment, Microwave and Optical Remote Sensing, Chalmers University of Technology, Chalmersplatsen 4, 41296 Gothenburg, SwedenDepartment of Space, Earth and Environment, Microwave and Optical Remote Sensing, Chalmers University of Technology, Chalmersplatsen 4, 41296 Gothenburg, SwedenThis study was conducted to quantify the errors prompted by neglecting three-dimensional (3D) effects, i.e., beam-filling and horizontal photon transport effects, at millimeter/sub-millimeter wavelengths. This paper gives an overview of the 3D effects that impact ice cloud retrievals of both current and proposed (Ice Cloud Imager) satellite instruments operating at frequencies of ≈186.3 and ≈668 GHz. The 3D synthetic scenes were generated from two-dimensional (2D) CloudSat (Cloud Satellite) observations over the tropics and mid-latitudes using a stochastic approach. By means of the Atmospheric Radiative Transfer Simulator (ARTS), three radiative transfer simulations were carried out: one 3D, one independent beam approximation (IBA), and one-dimensional (1D). The comparison between the 3D and IBA simulations revealed a small horizontal photon transport effect, with IBA simulations introducing mostly random errors and a slight overestimation (below 1 K). However, performing 1D radiative transfer simulations results in a significant beam-filling effect that increases primarily with frequency, and secondly, with footprint size. For a sensor footprint size of 15 km, the errors induced by neglecting domain heterogeneities yield root mean square errors of up to ≈4 K and ≈13 K at 186.3 GHz and 668 GHz, respectively. However, an instrument operating at the same frequencies, but with a much smaller footprint size, i.e., 6 km, is subject to smaller uncertainties, with a root mean square error of ≈2 K at 186.3 GHz and ≈7.1 K at 668 GHz. When designing future satellite instruments, this effect of footprint size on modeling uncertainties should be considered in the overall error budget. The smallest possible footprint size should be a priority for future sub-millimeter observations in light of these results.https://www.mdpi.com/2072-4292/12/3/5313d effectsmm/sub-mmice cloud imager |
| spellingShingle | Vasileios Barlakas Patrick Eriksson Three Dimensional Radiative Effects in Passive Millimeter/Sub-Millimeter All-sky Observations Remote Sensing 3d effects mm/sub-mm ice cloud imager |
| title | Three Dimensional Radiative Effects in Passive Millimeter/Sub-Millimeter All-sky Observations |
| title_full | Three Dimensional Radiative Effects in Passive Millimeter/Sub-Millimeter All-sky Observations |
| title_fullStr | Three Dimensional Radiative Effects in Passive Millimeter/Sub-Millimeter All-sky Observations |
| title_full_unstemmed | Three Dimensional Radiative Effects in Passive Millimeter/Sub-Millimeter All-sky Observations |
| title_short | Three Dimensional Radiative Effects in Passive Millimeter/Sub-Millimeter All-sky Observations |
| title_sort | three dimensional radiative effects in passive millimeter sub millimeter all sky observations |
| topic | 3d effects mm/sub-mm ice cloud imager |
| url | https://www.mdpi.com/2072-4292/12/3/531 |
| work_keys_str_mv | AT vasileiosbarlakas threedimensionalradiativeeffectsinpassivemillimetersubmillimeterallskyobservations AT patrickeriksson threedimensionalradiativeeffectsinpassivemillimetersubmillimeterallskyobservations |