Forecast impact assessment of a potential ATMS instrument in the early-morning orbit using the EDA method
Title | Forecast impact assessment of a potential ATMS instrument in the early-morning orbit using the EDA method
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Technical memorandum
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Date Published |
12/2024
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Secondary Title |
Technical Memoranda
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Number |
925
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Author | |
Publisher |
ECMWF
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Abstract | This study evaluates the impact of a hypothetical future microwave (MW) sounding instrument in a 17:30 Local Time of Ascending Node (LTAN) orbit, in order to provide input to the design of NOAA’s future MW sounding missions. As an international collaborative effort between the University of Maryland Cooperative Institute for Satellite Earth System Studies (UMD/CISESS) and the European Centre for Medium-Range Weather Forecasts (ECMWF), the potential Numerical Weather Prediction (NWP) benefits of these future MW sounders are being evaluated using an Ensemble of Data Assimilations (EDA) approach. The EDA method for assessing new observations provides a theoretical estimate of the expected reduction in analysis and short-range forecast uncertainty, as a result of assimilating the new data. A reduction of the spread resulting from additional observations used is hence an indication of beneficial impact from these observations. This study focuses on assessing the impact of an Advanced Technology Microwave Sounder (ATMS)-like instrument in a 17:30 LTAN orbit (referred to as 1730_LTAN), comparing its performance to existing sounders on the Polar Operational Environmental Satellites (POES) and ATMS instruments in the 13:30 LTAN orbit. For the new 1730_LTAN instrument, we assume a performance similar to that of ATMS on Suomi National Polar-orbiting Partnership (S-NPP). The EDA analysis shows that 1730_LTAN significantly impacts a range of atmospheric variables, when added on top of an observing system that uses MW-sounders from Meteorological Operational satellite (Metop) and Joint Polar Satellite System (JPSS) satellites only, but otherwise includes all other operationally used observations. The impact of a MW sounder in 1730_LTAN orbit is similar to or slightly larger than the benefit currently achieved with real data from the remaining MW-sounding instruments on the POES satellites (NOAA-15, 18, and 19), and the largest impact is achieved when 1730_LTAN and POES satellites are used together. When added to NOAA’s contribution from the JPSS system — including the Cross-track Infrared Sounder (CrIS), the Visible Infrared Imaging Radiometer Suite (VIIRS), and ATMS from S-NPP and NOAA-20 — the 1730_LTAN MW sounder provides an additional increase the overall short-range forecast impact. Sensitivity experiments that assume a degraded noise performance for the temperature-sounding channels of 1730_LTAN show that the benefit is significantly reduced compared to assuming S-NPP like noise levels, though some benefits from adding these observations are still observed. These findings emphasize the importance of instrument noise characteristics for the effectiveness of microwave temperature sounding observations in NWP systems. In addition, the consistency of the impact in the EDA between real and simulated microwave radiance observations is also evaluated. An additional experiment was conducted to compare the impact of simulated ATMS data with that of real ATMS observations from S-NPP and NOAA-20 satellites. The results show that the simulated and real ATMS data have a similar impact on EDA spread, suggesting that the simulations provide realistic predictions of actually achieved impact in the EDA. |
URL | https://www.ecmwf.int/en/elibrary/81632-forecast-impact-assessment-potential-atms-instrument-early-morning-orbit-using |
DOI | 10.21957/59eb3a9b44 |
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