Characterizing the FY-3A Microwave Temperature Sounder Using the ECMWF Model

Abstract

China's Feng-Yun-3A (FY-3A), launched in May 2008, is the first in a series of seven polar-orbiting meteorological satellites planned for the next decade by China. The FY-3 series is set to become an important data source for numerical weather prediction (NWP), reanalysis, and climate science. FY-3A is equipped with a microwave temperature sounding instrument (MWTS). This study reports an assessment of the MWTS instrument using the ECMWF NWP model, radiative transfer modeling, and comparisons with equivalent observations from the Advanced Microwave Sounding Unit-A (AMSU-A). The study suggests the MWTS instrument is affected by biases related to large shifts, or errors, in the frequency of the channel passbands as well as radiometer nonlinearity. The passband shifts, relative to prelaunch measurements, are 55, 39, and 33 MHz for channels 2-4, respectively. Relative to the design specification the shifts are 60, 80, and 83 MHz, with uncertainties of 62.5 MHz. The radiometer nonlinearity results in a positive bias in measured brightness temperatures and is manifested as a quadratic function of measured scene temperatures. By correcting for both of these effects the quality of the MWTS data is improved significantly, with the standard deviations of the (observed minus simulated) differences based on short-range forecast fields reduced by 30%-50% relative to simulations using prelaunch measurements of the passband, to values close to those observed for AMSU-A-equivalent channels. The new methodology could be applied to other microwave temperature sounding instruments and illustrates the value of NWP fields for the on-orbit characterization of satellite sensors.

Assimilation of MWHS radiance data from the FY‐3B satellite with the WRF Hybrid‐3DVAR system for the forecasting of binary typhoons

“…Recently, microwave satellite observations have contributed the most to improving numerical weather forecasts; the observations have been (or are being) ingested into DA systems [e.g., Smith et al ., ; Goodrum et al ., ; Li and Liu , ; Liu et al ., ; Schwartz et al ., ; Newman et al ., ; Shen et al ., ]. Examples include the Suomi National Polar‐orbiting Partnership (NPP)‐Advanced Technology Microwave Sounder (ATMS) data, used in the European Centre for Medium‐Range Weather Forecasts (ECMWF) and the National Centers for Environmental Prediction (NCEP) systems (NIELS) [ Niels et al , ; Collard et al ., ]; the NOAA‐18 and MetOp‐A Microwave Humidity Sounders (MHSs), used in the Weather Research and Forecasting DA system (WRFDA) [ Schwartz et al ., ; Newman et al ., ] as well as most operational centers [ Thépaut , ]; and the FY‐3A and FY‐3B MWHSs, used in the ECMWF system, which is the first operational use of Chinese polar orbiter satellite data by an NWP center outside China [ Lu et al ., a; Chen et al ., ].Notably, the MHS and MWHS are designed to retrieve profiles of atmospheric water vapor. Atmospheric moisture profiles have been shown to impact tropical convection and cyclones [ Holloway and Neelin , ].…”

A Bias in the Midtropospheric Channel Warm Target Factor on the NOAA-9 Microwave Sounding Unit

“…The procedure for merging individual satellites into a continuous, climate-quality TMT time series differs for each group and must account for a number of nonclimatic biases such as the diurnal cycle drift effect (e.g., Christy et al 1997;Christy et al 1998;Fu and Johanson 2005;Mears and Wentz 2005), biases due to the decay of satellite orbits (e.g., Wentz and Schabel 1998), frequency shifts in the radiometer passband (e.g., Zou and Wang 2012;Lu et al 2011), and the influence of the instrument body temperature on the measured radiance (e.g., Christy et al 1998Christy et al , 2000Prabhakara et al 2000;Mears et al 2003;Zou et al 2006). As a result of differences in the merging procedure for the various MSU teams, global TMT trends from 1979 to 2009 differ by more than a factor of 3.…”

All‐Sky Assimilation of the MWHS‐2 Observations and Evaluation the Impacts on the Analyses and Forecasts of Binary Typhoons

“…MWHS‐2, which is the second generation of microwave humidity sounders that have more channels than the first generation, is flown onboard the China Meteorological Administration's FengYun (FY)‐3C polar orbiting satellite. Among the FY series of polar orbit satellites, the FY‐3B MWHS has been assimilated into the ECMWF Integrated Forecasting System since 24 September 2014, which makes a slight improvement in long‐term and short‐term forecasts (Chen et al, ; Lu, ; Lu et al, ). Recently, the evaluation of MWHS‐2 data was also carried out by assimilating via the ECMWF (Lawrence et al, ), demonstrating that the quality of MWHS‐2 data is good and that there is a small positive impact on short‐range humidity forecasts.…”