[A-CG36] Satellite Earth Environment Observation

[ACG36-P11] Feasibility study for estimation of liquid-only water path over land using satellite-based Ka-band passive microwave measurements by synthetic simulations

*Rie Seto¹, Toshio Koike² (1.Meteorological Research Institute, 2.International Centre for Water Hazard and Risk Management)

Keywords:liquid water path estimation, Over land, AMSR-E/AMSR2, Ka-band

We investigate the feasibility of a method of estimating liquid water path (LWP, the sum of only liquid water paths of cloud and rain) over land using satellite-based Ka-band passive microwave measurements by conducting synthetic simulations. Specifically, we assume utilizing brightness temperatures at 36.5 GHz (TB36) from the Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) and AMSR2. TB36 is appropriate for liquid-only estimation as it is less affected by ice scattering compared to higher frequency measurements. However, estimating LWP over land using TB36 is challenging due to weak cloud signals and strong and heterogeneous land radiation in TB36. To address this, our method (Le36) dynamically estimates land emissivity using lower frequency (6.9 and 10.7 GHz) measurements from AMSR-E/AMSR2, minimizing land radiation errors. Synthetic simulations indicated that Le36 has high performance in cases of a wide range of LWPs (∼8 kg/m2) for cloud-only cases and a range of about 1.5∼8.0 kg/m2 for cloud-plus-rain cases if the cloud top (CT) height is appropriately set. For cases without suitable CT settings, emphasis should be placed on high-CT clouds (>8000 m). While there are some constraints, this study highlights the promising performance of Ka-band LWP estimation over land by mitigating the ice scattering effect and suggests the potential for more detailed cloud water content estimation concurrently using the higher frequency measurements.