Investigating the potential benefit to a mesoscale NWP model of a microwave sounder on board a geostationary satellite

Abstract

Observing the Earth with a microwave radiometer on board a geostationary satellite has generated interest for several decades. Such a mission would add a high observation rate in the microwave spectrum, offered by a geostationary orbit, to the sounding capabilities of the current observing system. The instrumental concept under study considers a microwave radiometer with six channels with different observation errors within the 183.31 GHz water vapour absorption band. Observing System Simulation Experiments (OSSEs) are conducted to examine if these very frequent microwave observations would be beneficial to mesoscale numerical weather prediction (NWP) and complement the current or soon‐available satellite observations. The OSSE framework is built up on (i) simulated observations from a known ‘truth’ which is a long and uninterrupted forecast from the Météo‐France ARPEGE global model, and (ii) the Météo‐France AROME mesoscale model in which the simulated observations are assimilated using a 1 h update cycle 3D‐Var data assimilation system. Benefits that may be expected from such a microwave sounder mission are evaluated in the context of a dense observing system including observations from the future hyper‐spectral InfraRed Sounder on board Meteosat Third Generation. In particular, impacts of microwave observations with observation errors ranging from 1.25 to 5 K are studied. One of the main findings of this study is that fine‐scale NWP systems do not only need observations that are frequent in space and time, but that these observations must be accurate as well.

Assessment of the Potential Impact of a Hyperspectral Infrared Sounder on the Himawari Follow-On Geostationary Satellite

“…We assimilated the clear-sky radiances of 36 temperature-sensitive channels and 25 water vapor (WV)-sensitive channels using RTTOV version 10.2 (Saunders et al 2012). The channels are selected based on the operational HSS setting for temperature channels and Duruisseau et al (2017) for WV channels. The channels selected is listed in Supplemental Table S1.…”

The Potential Impact of Assimilating Synthetic Microwave Radiances Onboard a Future Geostationary Satellite on the Prediction of Typhoon Lekima Using the WRF Model

“…Because microwave frequencies have the ability to partially penetrate clouds, valuable observations over data-sparse regions at these frequencies can be provided. Several bands in the microwave spectrum have been used to sound the atmosphere, notably those in the O 2 (50)(51)(52)(53)(54)(55)(56)(57)(58) and H 2 O (around 183 GHz) absorption lines [11,12], providing radiance measurements for atmospheric temperature and water vapor profiling in nearly all weather conditions, except very heavy precipitation, and independently of daylight conditions. Based on the 183 GHz properties, data have been used for deep convective cloud detection [13][14][15], snow, hail, and rainfall detection [11,[16][17][18], the evaluation of rainfall and convection prediction [19,20], and even the diagnostics of hurricane-like events in the Mediterranean [21], but there are indeed limited studies that address the usefulness of assimilating microwave radiances in the water vapor frequencies for forecasting.…”

“…The possibility of a microwave sounder detecting the atmospheric state from a geostationary satellite has been long studied [52]. Such instruments would contribute to increase the observational efficiency provided by geostationary satellites to the sounding capability of the current observational system [53][54][55]. However, there has been few researches directly assimilating microwave radiances from geostationary satellites in regional or global models, and no such studies have been conducted for typhoon prediction applications.…”

“…Radiance observations of the 183 GHz water vapor absorption band with different experimental configurations (cycling frequency, data resolution, and calibration accuracy) were investigated. The main reason for the choice of 183 GHz as the sounding channel on geostationary satellites is related to the limitation imposed by the antenna size, so as to achieve a compromise on the minimum desired spatial resolution [53,54]. The added value of assimilating microwave radiances from geostationary satellites will also be studied for the analyses and forecasts of the Lekima typhoon, which landed on Mainland China in early August 2019.…”

All-sky Information Content Analysis for Novel Passive Microwave Instruments in the Range from 23.8 GHz up to 874.4 GHz

“…A five-receiver instrument dropping one of the two highest channels proved to be equally powerful in a mid-latitude scenario as the all-receiver 10 instrument, but for tropical scenarios the highest channel reduced the error for very thin and high clouds. Also, new studies investigate the potential to assimilate microwave sounding data from geostationary satellites into numerical forecast models to further improve the forecast models (Duruisseau et al, 2017).…”