Impacts of Direct Assimilation of the FY-4A/GIIRS Long-Wave Temperature Sounding Channel Data on Forecasting Typhoon In-Fa (2021)

Abstract

In this paper, the Advanced Weather Research Forecast model (WRF-ARW) is used to investigate the potential impacts of assimilating the FengYun-4A (FY-4A) Geostationary Interferometric Infrared Sounder (GIIRS) long-wave temperature sounding channel data on the prediction of Typhoon In-Fa (2021). In addition, a series of data assimilation experiments are conducted to demonstrate the added value of the FY-4A/GIIRS data assimilation for typhoon forecasts. It is shown that the higher spectral resolution and broader coverage of GIIRS radiance data can positively impact the model analysis and forecasts with larger temperature and moisture increments at the initial time of simulations, thus producing a better simulation for the typhoon’s warm core aloft, vortex wind structure, and spiral rainfall band. Moreover, the assimilation of the GIIRS data can also lead to better storm steering flows and, consequently, better typhoon track forecasts. Overall, the assimilation of FY-4A/GIIRS temperature sounding channel data shows some added values to improve the track and storm structure forecasts of Typhoon In-Fa.

Scale Analysis of Typhoon In-Fa (2021) Based on FY-4A Geostationary Interferometric Infrared Sounder (GIIRS) Observed and All-Sky-Simulated Brightness Temperature

“…In this study, we focus on channel 27 (716.25 cm −1 ), channel 90 (755.625 cm −1 ), and channel 417 (960 cm −1 ), which are in the middle troposphere, lower troposphere, and the surface, respectively. Channel 27 and channel 90 are selected based on the sixty assimilation channels [21] in Table 1, and channel 417 is…”

“…In this study, we focus on channel 27 (716.25 cm −1 ), channel 90 (755.625 cm −1 ), and channel 417 (960 cm −1 ), which are in the middle troposphere, lower troposphere, and the surface, respectively. Channel 27 and channel 90 are selected based on the sixty assimilation channels [21] in Table 1, and channel 417 is the window channel which is appropriate for examining the cloud effect. The normalized weighting function of the selected 60 assimilated channels are shown in Figure 2.…”

Performances between the FY‐4A/GIIRS and FY‐4B/GIIRS Long‐Wave InfraRed (LWIR) channels under clear‐sky and all‐sky conditions

“…Despite being an experimental mission, the instrument FY-4A/GIIRS offers a rare early opportunity to get ready for the assimilation of GEO-hyperspectral radiances in NWP models. Recent studies (Yin et al, 2022;Xie et al, 2023;Zhang et al, 2023) demonstrate that assimilation of the clear-sky FY-4A GIIRS radiance is significant in regional NWP models. In terms of satellite data assimilation, it is assumed that the observation-minus-background (O − B) values, follow a Gaussian unbiased distribution (Dee, 2005).…”

Evaluation of Temperature and Humidity Profiles Retrieved from Fengyun-4B and Implications for Typhoon Assimilation and Forecasting

“…It enables the high temporal and spatial resolution detection of weather systems over China and its surrounding areas and helps to obtain a more detailed atmospheric vertical structure, such as retrieving atmospheric temperature profiles for 1 km layers and moisture profiles for 2 km layers [14,15]. Advancements such as the development of the fast radiative transfer model [16], the evaluation of bias characteristics [17], and the development of retrieval algorithms [18][19][20] have progressed the application of FY-4A/GIIRS data in NWP models [21][22][23]. Atmospheric temperature and humidity profile products retrieved from spaceborne sounders make noteworthy contributions to weather monitoring and forecasting [24,25].…”