Microwave Temperature Sounder Research Articles

A quality control procedure for Fengyun-3A microwave temperature sounder with emphasis on a new cloud detection algorithm

A cloud detection algorithm for satellite radiance from the microwave temperature sounder (MWTS) on board the first satellite of the Chinese polar-orbiting Fengyun-three series (FY-3A) is proposed based on the measurements at the frequencies of 50.3 and 53.6 GHz. The cloud liquid water path index (LWP index) is calculated using the brightness temperature at these two channels. Analysis of one case carried out in January2010shows the great consistency be-tween this new algorithm result and the available liquid water path product from the Meteorological Operational satellite A (MetOp-A).In general, about 60% of the global MWTS data are considered to be contaminated by cloud by virtue of the new cloud detection algorithm. A quality control (QC) procedure is applied to MWTS measurements with emphasis on the cloud detection. The QC steps are composed of (i) channel 2 over sea ice, land and coastal field of views (FOVs); (ii) channels 2 and 3 over cloudy FOVs; and (iii) outliers with large differences between observations and model simulations. After QC, MWTS measurements of channels 2–4 agree very well with the model simulations using the National Centres for Environmental Prediction (NCEP) forecast data as radiative transfer model input; the scan biases are reduced significantly, especially at the edges of the swath; and the frequency distributions of the differences between observations and model simulations become more Gaussian-like.

A quality control procedure for Fengyun-3A microwave temperature sounder with emphasis on a new cloud detection algorithm

A quality control procedure for Fengyun-3A microwave temperature sounder with emphasis on a new cloud detection algorithm

Observation‐based evaluation of ensemble reliability

In order to obtain new insight into the reliability of the ensemble prediction system of the European Centre for Medium‐range Weather Forecasts (ECMWF), we compare the ensemble spread‐error relationship obtained from an observation‐based verification to the one obtained from an analysis‐based verification. Observations used in this study are mainly radiosonde temperatures and radiance measurements from the AMSU‐A channel 5 microwave temperature sounder. The observation operators from the 4D‐Var data assimilation scheme are used to map the forecasts into observation space. In ‘observation‐space’, observed radiances are compared with forecast radiances, derived from the ensemble's atmospheric profiles of temperature, gas concentrations, cloud, and surface properties using the ‘RTTOV’ radiative transfer code.The observation‐space assessment yields different results than the analysis‐based assessment in the extratropics for short‐range forecasts (1‐day), and in the Tropics in general. In the extratropics, for 5‐day forecasts the discrepancy between the analysis‐based and observation‐based verification is small and the ensemble variances are quite reliable.The observation‐based diagnostics indicate that the stochastic model error schemes contribute to the well‐tuned ensemble spread in the extratropics, but can degrade the reliability of the ensemble in the Tropics. It is suggested that observation‐based diagnostics should be used more routinely to diagnose the ensemble performance, and help diagnosing the effectiveness of model error schemes and estimating the amplitude of the initial perturbations.

Assimilation of Chinese Fengyun-3B Microwave Temperature Sounder radiances into the Global GRAPES system with an improved cloud detection threshold

Fengyun-3B (FY-3B) is the second polar-orbiting satellite in the new Fengyun-three series. This paper describes the assimilation of the FY-3B Microwave Temperature Sounder (MWTS) radiances in the Chinese Numerical Weather prediction system — the Global and Regional Assimilation and PrEdiction System (GRAPES). A quality control procedure for the assimilation of the FY-3B MWTS radiance was proposed. Extensive monitoring before assimilation shows that the observations of channel 4 are notably contaminated. Channels 2 and 3 are used in this research. A cloud detection algorithm with an improved cloud-detection threshold is determined and incorporated into the impact experiments. The clear field-of-view (FOV) percentage increased from 42% to 57% with the new threshold. In addition, the newly added FOVs are located in the clear region, as demonstrated by the cloud liquid water path data from NOAA-18. The impact of the MWTS radiances on the prediction of GRAPES was researched. The observation biases of FY-3B MWTS O-B (differences between satellite observations and model simulations) significantly decreased after an empirical bias correction procedure. After assimilation, the residual biases are small. The assimilation of the FY-3B MWTS radiances shows a positive impact in the Northern Hemisphere and a neutral impact in the Southern Hemisphere.

Cloud and precipitation features of Super Typhoon Neoguri revealed from dual oxygen absorption band sounding instruments on board FengYun‐3C satellite

AbstractA new methodology is developed to detect the cloud structures at different vertical levels using the dual oxygen absorption bands located near 60 GHz and 118 GHz, respectively. Observations from Microwave Temperature Sounder (MWTS) and Microwave Humidity Sounder (MWHS) on board the recently launched Chinese FengYun‐3C satellite are used to prove the concept. It is shown that a paired oxygen MWTS and MWHS sounding channel with the same peak weighting function altitude allows for detecting the vertically integrated cloud water path above that level. A cloud emission and scattering index (CESI) is defined using dual oxygen band measurements to indicate the amounts of cloud liquid and ice water paths. The CESI distributions from three paired channels reveal unique three‐dimensional structures of clouds and precipitation within Super Typhoon Neoguri that occurred in July 2014.

Preliminary investigation of FengYun-3C Microwave Temperature Sounder (MWTS) measurements

The third FengYun satellite (FY-3C) was successfully launched into morning-configured orbit on 23 September 2013. The cross-tracking scanning instrument microwave temperature sounder (MWTS) on board FY-3C provides 13 channels, many more than the four MWTS channels on board FY-3A/B, at frequencies ranging from 50 to 60 GHz, which allow for probing the atmospheric temperature under all conditions except heavy precipitation. This study investigates and assesses the quality of the brightness temperature measurements from MWTS using the rapid radiative transfer model. Overall, MWTS observations (labelled ‘O’) compare favourably with simulations (labelled ‘B’) for troposphere and stratosphere channels except for surface-sensitive channels, the measurements of which provide more detail of thermal structures in the lower troposphere, especially for storm conditions such as tropical cyclones. Moreover, measurements from channels 1 and 4 can be used to derive the cloud liquid water path index (LWPindex) for cloud detection. However, this study also finds that (1) the brightness temperature differences (labelled ‘O-B’) between observations and model simulations exhibit a clear striping pattern for upper level channels; (2) the geolocation result has a systematic bias towards the real geolocation; and (3) the calibrated cold space view is contaminated by light reflected from the moon.

Neural Network Based Retrieval of Atmospheric Temperature Profile Using AMSU-A Observations

The present study describes artificial neural network (ANN) based approach for the retrieval of atmospheric temperature profiles from AMSU-A microwave temperature sounder. The nonlinear relationship between the temperature profiles and satellite brightness temperatures dictates the use of ANN, which is inherently nonlinear in nature. Since latitudinal variation of temperature is dominant one in the Earth’s atmosphere, separate network configurations have been established for different latitudinal belts, namely, tropics, mid-latitudes, and polar regions. Moreover, as surface emissivity in the microwave region of electromagnetic spectrum significantly influences the radiance (or equivalently the brightness temperature) at the satellite altitude, separate algorithms have been developed for land and ocean for training the networks. Temperature profiles from National Center for Environmental Prediction (NCEP) analysis and brightness temperature observations of AMSU-A onboard NOAA-19 for the year 2010 have been used for training of the networks. Further, the algorithm has been tested on the independent dataset comprising several months of 2012 AMSU-A observations. Finally, an error analysis has been performed by comparing retrieved profiles with collocated temperature profiles from NCEP. Errors in the tropical region are found to be less than those in the mid-latitude and polar regions. Also, in each region the errors over ocean are less than the corresponding ones over land.

Comparison of radio sounding and ground-based remote measurements of temperature profiles in the troposphere

A ground-based experiment on microwave temperature sounding in the troposphere with a RPG-HATPRO instrument, which has been performed at the Faculty of Physics, St. Petersburg State University since June, 2012, is described. On the basis of comparison of the results with radio sounding data, the temperature retrieval errors have been estimated using an algorithm provided by the manufacturer of the instrument. The errors have been compared with corresponding values for similar instruments functioning abroad. The conclusion has been drawn about a need to develop specialized algorithms and data processing procedures which include adaptation and correction of algorithms accounting for peculiarities of a specific instrument and experimental conditions.

Impact of FY-3A MWTS radiances on prediction in GRAPES with comparison of two quality control schemes

The impact of Microwave Temperature Sounder (MWTS) radiances on the prediction of the Chinese Numerical Weather prediction (NWP) system-GRAPES (Global and Regional Assimilation and PrEdiction System) with comparison of two Quality Control (QC) schemes was researched. The main differences between the two schemes are cloud detection, O-B (brightness temperature difference between observation and model simulation) check and thinning. To evaluate the impact of the two QC schemes on GRAPES, a typhoon case study and cycle experiments were conducted. In the typhoon case study, two experiments were conducted using both the new and old QC schemes. The results show that outliers are removed in the new QC while they exist in the old QC. The analysis and the model forecast are subsequently generated after assimilating data from the two QC schemes. The model-predicted steering flows more southward with the new QC scheme, and as a result, the forecast track in the experiments is more southward, i.e., closer to the best track than the old scheme. In addition to the case study, four impact cycle experiments were conducted for 25-day periods. The results show that the new QC scheme removed nearly all the biases whereas the old scheme could not. Furthermore, the mean and standard deviation of analysis increments with the new scheme is much smaller than those of O-B. In contrast, the old scheme values are either slightly smaller or the same. Verifications indicate that forecast skill is improved after applying the new scheme. The largest improvements are found in the Southern Hemisphere. According to the results above, MWTS with the new QC scheme can improve the GRAPES forecast.

A Quality Control Procedure for FY-3A MWTS Measurements with Emphasis on Cloud Detection Using VIRR Cloud Fraction

Abstract A quality control (QC) procedure for satellite radiance assimilation is proposed and applied to radiance observations from the Microwave Temperature Sounder (MWTS) on board the first satellite of the Chinese polar-orbiting Fengyun-3 series (FY-3A). A cloud detection algorithm is incorporated based on the cloud fraction product provided by the Visible and Infrared Radiometer (VIRR) on board FY-3A. Analysis of the test results conducted in July 2011 indicates that most clouds are identifiable by applying an FY-3A VIRR cloud fraction threshold of 37%. This result is verified with the cloud liquid water path data from the Meteorological Operational Satellite A (MetOp-A). On average, 56.1% of the global MWTS data are identified as cloudy by the VIRR-based cloud detection method. Other QC steps include the following: (i) two outmost field of views (FOVs), (ii) use of channel 3 if the terrain altitude is greater than 500 m, (iii) channel 2 over sea ice and land, (iv) coastal FOVs, and (v) outliers with large differences between model simulations and observations. About 82%, 74%, and 29% of the MWTS observations are removed by the proposed QC for channels 2–4, respectively. An approximate 0.5-K scan bias improvement is achieved with QC, with a large impact at edges of the field of regard for channels 2–4. After QC, FY-3A MWTS global data more closely resemble the National Centers for Environmental Prediction (NCEP) forecast data, the global biases and standard deviations are reduced significantly, and the frequency distribution of the differences between observations and model simulations become more Gaussian.

Case Studies of Drought-Flooding Variations for Validating FY-3B/MWRI Data With Intercalibration of Aqua/AMSR-E

As a second generation of China's polar orbiting meteorological satellite, the satellite of FY-3A and FY-3B were launched in 2008 and 2010, sequentially, in sun-synchronous orbits located at the altitude 831 km. The FY-3A/B load totally 11 sensors, including microwave sensors, such microwave temperature sounder (MWTS), microwave humidity sounder (MWHS) and microwave radiometer imager (MWRI), etc. In this paper, based on atmospheric radiative transfer model, intercalibration of multi-channel MWRI measurements with, correspondingly, AMSR-E data are analyzed. Some FY-3B MWRI data along Yangtze River area during spring and summer seasons of 2011 are specifically collected. Based on radiative transfer and MWRI features, the polarization indexes for monitoring drought and flooding happened during those periods are quantitatively analyzed and compared by AMSR-E data. Meanwhile, the scattering indexes are also analyzed for monitoring rainfall, and validated by AMSR-E data and ground station records.

Long-Term Calibration and Accuracy Assessment of the FengYun-3 Microwave Temperature Sounder Radiance Measurements

The Chinese FengYun-3 (FY-3)A satellite was successfully launched on May 27, 2008, with a Microwave Temperature Sounder (MWTS) onboard. MWTS has four channels with frequencies of 50.3, 53.596, 54.94, and 57.29 GHz, respectively. The MWTS measurements are primarily used for profiling atmospheric temperatures from surface to lower stratosphere. MWTS is a cross-track scanning instrument, and its Earth-view measurements are calibrated through the warm target and cold space measurements during every scan cycle. In this paper, the FY-3A MWTS and its channel characteristics are first introduced. The calibration process and the postlaunch instrument performance are then presented, including the long-term trends of noise equivalent differential temperature (NEDT), calibration counts from cold space and warm targets, instrument telemetry, and channel gains. The observed and simulated brightness temperature (BT) differences of MWTS and Advanced Microwave Sounding Unit-A (AMSU-A) are compared. It is shown that the MWTS NEDT values at all channels are much better than its specification. The BT biases of MWTS channels 1 and 3 with respect to the simulations are similar in magnitude to those from National Oceanic and Atmospheric Administration-18 AMSU-A. The MWTS biases at channels 2 and 4 are larger than AMSU-A.

An Assessment of the FY-3A Microwave Temperature Sounder Using the NCEP Numerical Weather Prediction Model

The MicroWave Temperature Sounder (MWTS) on FY-3A has four channels with designed band central frequencies of 50.3, 53.6, 54.9, and 57.3 GHz, respectively. Lu et al. found that the central frequency for three upper level sounding channels shifted after the satellite launch into orbit. This study confirms the findings Lu et al. using a different numerical weather prediction (NWP) model and a different radiative transfer model. Furthermore, it is shown that the strong temperature dependence of MWTS <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">O</i> - <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DF</sup> biases found in our earlier work is mostly induced by these frequency shifts, where O represents MWTS observations and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DF</sup> is model simulations. The mean difference of brightness temperature simulations with ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SF</sup> ) and without ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SF</sup> ) incorporating the frequency shifts into the radiative transfer model resembles the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">O</i> - <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SF</sup> biases. For NWP applications of FY-3A MWTS data, it is sufficient to generate new fast radiative transfer model coefficients that incorporate the new passband parameters, and the resulting MWTS <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">O</i> - <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">shifted</sup> biases become constant as those of MetOp-A/NOAA-18 AMSU-A data. For climate applications, the FY-3A MWTS brightness temperatures adjusted by subtracting <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SF</sup> - <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DF</sup> match quite well with the MetOp-A/NOAA-18 AMSU-A data at the simultaneous nadir overpass locations in both the Arctic and Antarctic.

Quality Assessments of Chinese FengYun-3B Microwave Temperature Sounder (MWTS) Measurements

Following the successful launch of the first polar-orbiting morning-configured satellite, FY-3A, on May 27, 2008, in a new Fengyun three (FY-3) series, the second afternoon-configured polar-orbiting satellite (FY-3B) was launched on November 5, 2010. The four-channel Microwave Temperature Sounder (MWTS) was onboard both FY-3A/B satellites, with designed channel frequency similar to channels 3, 5, 7, and 9 of the Advanced Microwave Sounding Unit-A (AMSU-A). This study assesses the quality of the brightness temperature measurements from FY-3B MWTS by comparing them with numerical weather prediction (NWP) model simulations and NOAA-18 AMSU-A measurements with the same frequencies. A strong latitudinal-dependent bias is found for both MWTS channel 3 and AMSU-A channel 7. At channel 4, the brightness temperatures are contaminated within a small latitudinal zone ( ~ 30°-40°N) of the Northern Hemisphere. It is also found that the MWTS channel 4 bias is strongly asymmetric across the scan and the fourth field of view (FOV4) of channel 4 is globally and systematically warmer than its neighboring FOVs. These anomalous biases may arise from sidelobe effect and interferences of the signal transmitted from some unknown sources. A quality control algorithm is developed to remove the anomalous data at MWTS channel 4 for its applications in NWP.

Overview of FY-3 Payload and Ground Application System

The payload on board the FengYun 3 (FY-3) satellite series has been providing critical observations to the Earth, and the observation data have been processed and distributed to various users by the corresponding ground application system. In this paper, the FY-3 payload and its future development plan are presented, and its ground system is introduced. The major characteristics of the FY-3 instruments and the requirement on the instruments for major applications are discussed as well. There are nine new instruments, including the Microwave Temperature Sounder (MWTS), Microwave Humidity Sounder (MWHS), Infrared Atmospheric Sounder (IRAS), Medium-Resolution Spectral Imager (MERSI), Microwave Radiation Imager (MWRI), Solar Backscatter Ultraviolet Sounder, Total Ozone Unit, Solar Irradiation Monitor, and Earth Radiation Measurement. The data quality from the IRAS, MWTS, MWHS, and MWRI has proved to be good, and according to our evaluation at the European Centre for Medium-Range Weather Forecasts (ECMWF), the data have a very high availability. The MERSI has 20 visible (VIS) and infrared (IR) channels, of which three are VIS channels with a 250-m spatial resolution, one is a near-IR channel with a 250-m spatial resolution, and one is a long-wave IR channel with a 250-m spatial resolution. The global data at a 250-m spatial resolution are very useful in weather, disaster, and environmental monitoring. Compared with the ground observations, the ozone products derived from the FY-3 series are highly accurate. We have completed the calibration and validation of these sensors and most products.

The Study on Calibration Target with Temperature Adjusted Function for 10GHz~90GHz Microwave Radiometer

FY-3 meteorological satellite is the new generation of China’s polar-orbit meteorological satellite and be hoped to meet the operational weather prediction requirements of china and the global change research. The microwave imaging sounder (MWIS) and the microwave temperature sounder (MWTS) are two of its main payloads. To calibrate the linearity, sensitivity and stability of MWIS and MWTS accurately, the calibration target with temperature adjusted function is studied by Beijing Institute of Radio Metrology &amp; Measurement (BIRMM). The configuration, technical specifi-cations and operational theory of the calibration target is presented in this paper. Because the two PID (Proportional-Integral-Differential) outputs by associating the parameter of liquid nitrogen cooling combined with electric heater is used, the target can provide a temperature adjusted brightness temperature output from 85K to 340K in 10GHz~90GHz to meet calibration requirements in lab environments.

The Study on Calibration Target with Temperature Adjusted Function for 10GHz~90GHz Microwave Radiometer

FY-3 meteorological satellite is the new generation of China’s polar-orbit meteorological satellite and be hoped to meet the operational weather prediction requirements of china and the global change research. The microwave imaging sounder (MWIS) and the microwave temperature sounder (MWTS) are two of its main payloads. To calibrate the linearity, sensitivity and stability of MWIS and MWTS accurately, the calibration target with temperature adjusted function is studied by Beijing Institute of Radio Metrology & Measurement (BIRMM). The configuration, technical specifi-cations and operational theory of the calibration target is presented in this paper. Because the two PID (Proportional-Integral-Differential) outputs by associating the parameter of liquid nitrogen cooling combined with electric heater is used, the target can provide a temperature adjusted brightness temperature output from 85K to 340K in 10GHz~90GHz to meet calibration requirements in lab environments.

Assessments of Chinese Fengyun Microwave Temperature Sounder (MWTS) Measurements for Weather and Climate Applications

Abstract After the successful launches of the first two polar-orbiting satellites in a new Fengyun-3 (FY-3) series, FY-3A/B, into a morning- and afternoon-configured orbit in May 2008 and November 2010, respectively, China will launch its next three polar-orbiting satellites before 2020. The Microwave Temperature Sounder (MWTS) on the FY-3A/B satellites has four channels that have the same channel frequency as channels 3, 5, 7, and 9 of Advanced Microwave Sounding Unit-A (AMSU-A). Thus, the quality of the brightness temperature measurements from the FY-3A MWTS can be assessed using the AMSU-A brightness temperature observations from the NOAA-18 satellite. Overall, MWTS data compare favorably with AMSU-A data in terms of its global bias to NWP simulations. The standard deviations of global MWTS brightness temperatures are slightly larger than those of AMSU-A data. The scan-angle dependence of the brightness temperature bias is found to be symmetric for MWTS channel 3 as well as AMSU-A channel 7, and asymmetric for MWTS channels 2 and 4 and AMSU-A channels 5 and 9; there is a warm (cold) bias located at the beginning (end) of a scan line for all asymmetric channels except for MWTS channel 4. A major difference between the two instruments is that the MWTS biases in channels 3 and 4 are negative in low latitudes and positive in high latitudes, while the AMSU-A biases are negative in all latitudes. A detailed analysis of the data reveals that such a difference is closely related to the difference in the temperature dependence of biases between the two instruments. The AMSU-A biases are independent of the scene temperature, but MWTS biases vary with the earth scene brightness temperature. The root cause of the bias could be a combination of several factors, including solar contamination on its calibration target, detector nonlinearity, and the center frequency drift. This study further demonstrates the utility of a well-calibrated radiometer like AMSU-A for the assessment of a new instrument with NWP fields that are used as inputs to forward radiative transfer simulations.

Data validation of Chinese microwave FY-3A for retrieval of atmospheric temperature and humidity profiles during Phoenix typhoon, 2008

As a first polar-orbit meteorological satellite, FY-3A (FY – Feng Yun, which means wind and cloud), in China, the Microwave Temperature Sounder (MWTS) and Microwave Humidity Sounder (MWHS) are aboard the satellite for the purpose of retrieving atmospheric temperature and humidity profiles. A novel mixed (MIX) model, based on the Millimetre Propagation Model (MPM) and Rosenkranz (ROS) models, is developed for calculation of atmospheric absorption coefficients in multiple channels of the MWTS and MWHS using the China National Standard Atmosphere (GB 1920-80) and US Standard Atmosphere of 1976. Using atmospheric radiative transfer with the in situ measurements of 836 radiosonde datasets (including the altitude, pressure, atmospheric temperature and humidity) from 16 sites in China and Japan, multiple channel brightness temperatures are simulated and compared with FY-3A MWTS/MWHS observations for data validation. Simulations using respective MPM, ROS and MIX models are also analysed. Furthermore, the statistical D-matrix is constructed from the MWTS/MWHS data and the aforementioned radiosonde measurements, and it is then applied to the retrieval of atmospheric temperature and humidity profiles over the north-western Pacific Ocean during 2008’s Phoenix typhoon.

Improved assimilation of data from China's FY‐3A microwave temperature sounder

AbstractThe FY‐3A microwave temperature sounder (MWTS) suffers from nonlinearities in the calibration of the radiometer and uncertainties in the radiometer passbands. Corrections have been developed and are assessed here by comparing recalibrated MWTS data with equivalent advanced microwave sounding unit‐A (AMSU‐A) observations. The corrections are effective in improving the first guess departure statistics for MWTS, relative to the original uncorrected data, to values close to those for AMSU‐A equivalent channels. In observing system experiments, MWTS observations improve the first guess fits for AMSU‐A observations. Forecast verification shows a systematic improvement by using the recalibrated data, e.g. forecasts of 200 hPa geopotential are improved to Day 3 in the SH by approximately 1%. Copyright © 2011 Royal Meteorological Society