Abstract
Abstract. We perform an all-sky information content analysis for channels in the millimetre and sub-millimetre wavelength with 24 channels in the region from 23.8 to 874.4 GHz. The employed set of channels corresponds to the instruments ISMAR and MARSS, which are available on the British FAAM research aircraft, and it is complemented by two precipitation channels at low frequencies from Deimos. The channels also cover ICI, which will be part of the MetOp-SG mission. We use simulated atmospheres from the ICON model as basis for the study and quantify the information content with the reduction of degrees of freedom (ΔDOF). The required Jacobians are calculated with the radiative transfer model ARTS. Specifically we focus on the dependence of the information content on the atmospheric composition. In general we find a high information content for the frozen hydrometeors, which mainly comes from the higher frequency channels beyond 183.31 GHz (on average 3.10 for cloud ice and 2.57 for snow). Considerable information about the microphysical properties, especially for cloud ice, can be gained. The information content about the liquid hydrometeors comes from the lower frequency channels. It is 1.69 for liquid cloud water and 1.08 for rain using the full set of channels. The Jacobians for a specific cloud hydrometeor strongly depend on the atmospheric composition. Especially for the liquid hydrometeors the Jacobians even change sign in some cases. However, the information content is robust across different atmospheric compositions. For liquid hydrometeors the information content decreases in the presence of any frozen hydrometeor, for the frozen hydrometeors it decreases slightly in the presence of the respective other frozen hydrometeor. Due to the lack of channels below 183 GHz liquid hydrometeors are hardly seen by ICI. However, the overall results with regard to the frozen hydrometeors also hold for the ICI sensor. This points to ICI's great ability to observe ice clouds from space on a global scale with a good spatial coverage in unprecedented detail.
Highlights
In the last few years, passive millimetre and sub-millimetre wavelength measurements of the cloudy sky from space have gained increasing attention
The employed set of channels corresponds to the instruments ISMAR and MARSS, which are available on the British FAAM research aircraft, and it is complemented by two precipitation channels at low frequencies from Deimos
It is possible to put a special focus on the upcoming Ice Cloud Imager (ICI) instrument on MetOp-SG, which employs channels from 183 to 664.0 GHz to gain more detailed information about cloud ice, its microphysical properties and perhaps some more profile information than the instruments that are currently deployed in the different satellite missions
Summary
In the last few years, passive millimetre and sub-millimetre wavelength measurements of the cloudy sky from space have gained increasing attention. We study the information content of passive microwave measurements of clouds from space with specific focus on the cloudy atmosphere, especially on frozen hydrometeors. We investigate whether it depends on the combinations of cloud and precipitation hydrometeors within the atmospheric column how much information is obtained, as the results from Greenwald and Christopher (2002) suggest. We can put the focus on the potential of novel instruments operating at frequencies higher than 183 GHz to robustly observe ice, and include liquid clouds and precipitation, which are observed with the channels lower than 183 GHz. Since it is impossible to have full knowledge of the real atmosphere, we chose to base our investigations on highresolution model data from the ICOsahedral Non-hydrostatic.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
