In this work, the brightness temperature (TB) transfer from the microwave calibration target (MCT) to the feeder antenna in the near-field region is investigated, which is the fundamental physical process in microwave radiometer calibration. As in this scenario, the MCT and antenna cannot be separately considered as points like in far fields, it is interesting and important to study the TB characteristics of the target in cases of feeder antennas at different positions and with different aperture sizes. Recently, as reciprocity in the near field has been established, this fundamental issue can be now investigated. The study starts at a high frequency of 89 GHz when the free-space lambda is much smaller than the unit period of MCT; then, the distributions of the local TB contribution rate are calculated to understand the possible TB transfer variation. It is found that the key factor for the TB variation is the illumination area upon the array-type MCT, and as the footprint is sufficiently large to cover several pyramid units, the TB can be stable versus relative position.

In this work, an interesting phenomenon is investigated in the scenario of calibration link in microwave radiometers, where a feeder antenna is directly harvesting the radiated brightness temperature (BT) from the microwave calibration target (MCT). As reciprocity has been established for the near-field BT transfer, it is important to investigate the performance variation of the MCT in case of different antenna illumination. In this work, it is found and analyzed that at the frequencies where lambda is near to the unit period of periodic array-shaped calibration target, the reflectivity may be notably increased in case of small aperture feeder illumination. This is a disturbing phenomenon that should be avoided for practical applications.

Observations of the Micro-Wave Humidity Sounder-II (MWHS-II) onboard FengYun-3C (FY-3C) satellite are crucial for numerical weather prediction. Precise calibration of MWHS-II is fundamental for the accurate application. However, the Moon’s presence in the deep space view (DSV) can corrupt the in-orbit calibration of MWHS-II, and thus it is necessary to quantify the Moon’s influence. This study proposes a method to identify the Moon’s intrusion into the DSV, which improves the accuracy of lunar identification, by taking into account the lunar phases and the detectable radiance change of the sensor. The abrupt jump in the DSV due to the lunar contamination is removed, assuming the radiometric gain of the adjacent scans barely changes. With the corrected DSV counts, the effective lunar brightness temperature (TB) is calculated. It is found that the phase of the Moon observed by the FY-3C MWHS-II is in the range of 95°–140°, and the effective lunar TB is up to 15 K at 89/118.75 GHz and 45-50 K at 150/183.31 GHz. Though the results are subject to the uncertainties of the Moon calculations and the beam pointing, this study offers unique insights into the lunar observations of MWHS-II onboard the polar-orbiting FY-3C.

Atmospheric boundary layer detection is in urgent demand in meteorological and climate research and is closely related to human life and agricultural production. Atmospheric microwave fine-spectral sounding is a cutting-edge means to break through the regional and even global all-weather atmospheric boundary layer temperature and humidity profiling observations. In this paper, we carry out field campaigns using a unmanned aerial vehicle-based (UAV-based) fine-spectral microwave radiometer to solve key technologies of boundary layer detection and inversion, and realize the sounding of atmospheric water condensate and the study of the evolution.

This paper conducts an in-depth analysis of spaceborne hyperspectral microwave radiometers for remotely sensing atmospheric boundary layers’ temperature and humidity profiles. Utilizing 137 vertical-level atmospheric profile data from the European Centre for Medium-Range Weather Forecasts (ECMWF), the study employs the Atmospheric Radiative Transfer Simulator (ARTS) to construct a forward model of an Earth-based spaceborne microwave radiometer, enabling the computation of the Jacobian matrix. This research thoroughly evaluates the posterior probability of retrieval errors and vertical resolution by analyzing both the background error covariance matrix and the measurement error covariance matrix alongside the Jacobian matrix. Findings reveal that a spectral resolution of 10 MHz significantly enhances the accuracy of posterior retrieval errors and improves vertical resolution, in contrast to the 1000 MHz resolution, which shows lesser efficacy. While hyperspectral microwave radiometers offer clear benefits for detailed atmospheric profiling, the increase in spectral resolution does not uniformly translate to performance enhancements due to the accompanying rise in system noise. These results underscore the importance of conducting meticulous assessments to determine the most effective spectral resolution for radiometers, considering the intricate balance between information gain and noise.

Since the first microwave humidity sounder (MWHS) launched on May 27, 2008, six MWHSs deployed on polar-orbiting FengYun-3 (FY-3) satellites to date have been continuously providing temperature and humidity information for over 15 years. Compared to the predecessors MWHS onboard FY-3A/B/C/D, the central frequency of the window channel is shifted from 150 to 166 GHz for MWHS-II onboard FY-3E/F, and the additional low noise amplifier (LNA) embedded in the radio frequency (RF) module optimizes the performance of the receiver system, leading to a significant reduction in the noise temperature of the receivers. The reduced bias and standard deviation of simultaneous Nadir overpass (SNO) results between MWHS-II and Advanced Technology Microwave Sounder (ATMS) further corroborate that that the instrument performance has been improved and updated. The interchannel interference of FY-3E/F is mitigated, and the channel sensitivities are also enhanced according to the postlaunch test results.

FengYun-3F (FY-3F) is a sun-synchronous satellite launched on August 3, 2023. It crosses the equator at a local time of 10:15 a.m. and will be a substitute for FY-3C. This study introduces the preflight and in-orbit calibration of microwave humidity sounder-II (MWHS-II) onboard FY-3F. The instrument nonlinearity and radiometric sensitivity are characterized in the ground thermal vacuum chamber (TVAC) tests. The residual of nonlinearity correction is within 0.5 K, depending on viewing scenes and channels. As a substitute for its predecessor FY-3C, the performance of MWHS-II onboard FY-3F is compliant with requirements. The in-orbit radiometric sensitivity of the sensor is consistent with the prediction of the TVAC test results, with margins of 20%–60% relative to the requirements. The in-orbit behavior of the sensor is further evaluated by simultaneous nadir overpass (SNO) with the advanced technology microwave sounder (ATMS) and the difference between observation-background (O-B). The results confirm that the radiometric performance of MWHS-II onboard FY-3F is improved, compared to FY-3C. With stable and consistent observations, MWHS-II onboard FY-3F will benefit numerical weather predictions by providing accurate temperature and humidity information at the 118- and 183-GHz bands.

This article investigates the potential of microwave sounders for a future international Venusian lower atmosphere exploration mission. Venusian microwave atmospheric radiative transfer (RT) calculations from a spaceborne perspective are performed with appropriate settings of the specific observation geometry and input atmospheric scenarios. An atmospheric profile perturbation analysis was undertaken to determine the channel selection and corresponding retrieval accuracy. Meanwhile, a suitable configuration of microwave sounder is proposed based on the gas absorption characteristics, sensitivity, and retrieval error analysis. The channel frequency selected includes 21 (2) channels of SO2 (H2SO4) absorption lines and its sidebands, as well as 37 channels between 6 and 42 GHz. Due to the strong coupling between temperature, SO2, and H2SO4 in the lower atmosphere, a joint physical retrieval method [optimal estimation method (OEM)] is proposed. Under ideal model conditions, the RMSE of retrieved temperature profiles improves by 1.3 K to stay within 2 K for 0–65 km, while the maximum RMSEs for SO2 and H2SO4 volume mixing ratios (VMRs) show improvements of at least 15% and 10%, reaching 30% and 25%, respectively. These results validate the proposed microwave sounder’s effectiveness for temperature and SO2 (H2SO4) profiling up to 65 km (30–75 km for SO2 and 35–55 km for H2SO4). However, increasing model error reduces retrieval accuracy, emphasizing the importance of model development for accurate joint observations of these parameters.

Fine spectrum refines conventional spectral sounding channels by increasing the spectral resolution to improve further the vertical resolution for accurate detection of atmospheric parameters. The 50- to 60-GHz absorption band is mainly used to sound the vertical distribution of atmospheric temperature in the troposphere and stratosphere, and 53 GHz is located in the weak oxygen absorption line. FengYun-3E (FY-3E) Microwave Temperature Sounder-III (MWTS-III) has two sounding channels added to this absorption band, and initially realized the refinement of the sampling channels. In this article, by establishing the assimilation operator for the radiance data of MWTS-III in China Meteorological Administration Global Assimilation Forecasting System (CMA-GFS) 4D-Var, and using the in-orbit observations from FY-3E MWTS-III, we investigate the impact of refining sounding channels at 53 GHz on numerical weather prediction (NWP). Results show that the temperature increment has the largest value and the widest influencing area near the peak weighting functions of channels, and the intensity and range of the temperature increment also change as the number of assimilated channels increases. An increment index can help quantify the impact of channel refinement on the forecast field. After single-cycle assimilation, the root mean square error (RMSE) of atmospheric parameters in the analysis field shows a decreasing trend. After continuous assimilation, the RMSE of geopotential height has a positive effect on short-term forecasts as the number of assimilated channels increases. It can be seen that channel refinement at 53 GHz positively impacts the performance of NWP.

The precipitation evolution plays a key role in the refined precipitation forecasting. At present, the description on the evolution of hydrometer particles is insufficient. There are still deviations in the quantification of cloud, ice, and rain microphysical parameters in the cloud model, and the evolution mechanism is not refined enough, which affects the accurate prediction and decision-making of precipitation. In order to solve this problem, this project makes full use of the advantages of 89GHz for cloud ice identification and inversion. With the existing ground-based multi-frequency and multi-angle (10.65~89GHz) dual-polarization scanning microwave radiometer, micro rain radar MRR and Raindrop spectrometer, accurate model of cloud ice, cloud water and rain paths can be obtained. Profiles and spatial-temporal distribution of particle concentrations and average size are further retrieved using deep learning methods. The project aims at the physical evolution process of cloud ice, cloud water and rain in each development stage, trying to quantify their indicative role and develop a microwave remote sensing model according to the atmospheric microphysical information in the precipitation process. The project results will provide insight into the cloud rainfall efficiency in cloud models, and support important theoretical references for refined precipitation forecasts and weather modification.

Calibration uncertainty is quantified for Microwave Humidity Sounder (MWHS-II) onboard Fengyun Meteorological Satellites (FY-3C and D) in this study. The on-orbit calibration equation is used to construct the uncertainty model and the observation period is during January to December 2020. The results show that, among the 15 channels of the microwave sound, Channel 2 has the largest observation uncertainty due to its narrow bandwidth. The maximum observing uncertainty values over the ocean and land onboard FY-3C are 0.98K and 0.97K, respectively, while the corresponding values onboard FY-3D satellite are 0.94K and 0.82K. The calibration uncertainties of the 183GHz channels onboard FY-3D are greater than that of FY-3C due to the harmonic interference.

In the calibration of Microwave Humidity and Temperature Sounder (MWHTS) onboard the Fengyun-3E (FY-3E) satellite, the ideal rectangular spectral response function is normally used. However, the measured spectral response function has in-band fluctuation, which will not only cause errors to the calibration, but also is essential to the subsequent data retrieval and assimilation applications. In this paper, the spectral response function (SRF) of five channels located near the frequency of 183.31-GHz is studied. The results demonstrate that different channels have different responses to the measured SRF and the ideal rectangular SRF. The closer the channel is the frequency 183.31-GHz, the maximum deviation is nearly 0.2 K. In addition, a constant noise, uniform noise, Gaussian noise and Chebyshev 1 ripple noise were added respectively. The greater the noise amplitude, the greater the brightness temperature deviation, and the results of four different noise was consistent. When the noise amplitude is set to 3 dB, the brightness temperature deviation reaches 0.1 K. The results can not only provide reference for the design of the sensor, but also provide a new idea for data calibration, so as to improve the accuracy of data calibration.

This paper demonstrated the advantages of spaceborne hyperspectral microwave radiometer in retrieving temperature and humidity profiles. Build a forward model using the Atmospheric Radiative Transfer Simulator (ARTS) and input profile datasets from the ECMWF 137 level short range forecasts to calculate simulated brightness temperature. A physical retrieval algorithm (Optimal Estimation Method, OEM) was used to retrieve temperature profiles ranging from 0-40 km and humidity profiles ranging from 0-10 km. The results showed that 10 MHz can more effectively retrieve temperature and humidity profiles. The mean values of root-mean-square error integrated over the height are 0.6096 K (0.6093 K) and 2.6373% (2.7210%) for land (ocean) temperature and relative humidity profiles, respectively. The information content (IC) of different spectral resolutions slightly differs from OEM retrieval results. 10 MHz and 100 MHz spectral resolutions have maximum channel IC for retrieving temperature and humidity profiles, respectively. In conclusion, spaceborne microwave hyperspectral sounder can improve the retrieval accuracy of temperature and humidity profiles by increasing spectral resolution.

Calibration accuracy can affect the interpretation of microwave radiometer observations and it is the premise of quantitative microwave remote sensing. To calibrate the microwave radiometers is to establish a quantitative relationship between output (voltage or voltage digital) and input noise temperature. On-orbit calibration uses the calibration target of the sensor and the cold space as reference sources. It has been found that the performance of the same microwave instrument will be degraded with the aging components. Observations from microwave instruments of different satellite generations may be inconsistent, and with different systems the receiving radiance for the same atmospheric scene could be also different. To calibrate the microwave payloads onboard FengYun satellite, the calibration/validation is performed based on the global navigation satellite system (GNSS) retrievals, focusing on the sounding mechanisms of microwave and the GNSS occultation payloads on FengYun polar-orbiting meteorological satellites. For GNSS occultation data, the detection accuracy above 3 km is better than that of the microwave radiometer. Within the time window of 30 min and the spatial resolution of 0.5 degree both in latitude and longitude, the brightness temperature deviation is better than 3 K for clear sky. The results show that the FengYun meteorological satellite can not only provide global all-weather temperature and humidity profiles but also realize self-cross-calibration for microwave sounders with complementary instruments onboard.

This study presents precipitation and related microphysical processes observed by a self-developed ground-based five-band dual-polarization microwave radiometer in conjunction with disdrometer and vertically pointing micro rain radars (MRRs) during convective and orographically induced precipitation. The ground-based microwave radiometer has ten channels measuring in horizontal and vertical polarization at 10.65, 18.7, 23.8, 36.5 and 89GHz, where dual 89GHz channels can provide additional information on cloud-ice and melting cloud, which are rarely used in ground-based instruments so far. Measured brightness temperatures and polarization differences (vertical-horizontal) are validated by 3-D radiative transfer simulations (VDISORT) considering the role played by cloud-ice and melting particles, other than traditional cloud-rain particles. Observing measurements confirm the importance of the 89GHz polarization difference for separating the cloud-ice from rain and cloud-water component and quantitatively interpreting cloud-ice-rain concentration and distribution profiles by deep learning combing additional measurements from MRR and disdrometer.

This paper develops a novel deep learning-based model for quantitative precipitation estimation (QPE). In this model, the multi-channel microwave Brightness Temperature (TBVand TBH) and Polarization Difference (PD = TBV - TBH) from the Microwave Radiation Imager (MWRI) aboard the FY-3D satellite are used as predictor variables for QPE. An observational database built from the Integrated Multi-satellite Retrievals for GPM (IMERG) is employed as reference to train the deep learning model. In order to assess the model performance, an independent test dataset is used, and the results show that the model is computationally efficient and the derived QPE is highly consistent with IMERG product. The encouraging results also indicate that PD can enhance the precipitation estimation performance compared to using the TB only.

This study characterizes the marginally-known angular-dependent polarization difference of the land surface emissivity (LSE), using the microwave humidity sounder (MWHS) onboard China’s sun-synchronous satellite FengYun-3B (FY-3B). The instrument has two quasi-polarization channels at 150 GHz in addition to the three water-vapor absorption channels in the vicinity of 183 GHz, allowing observations at quasi vertical and horizontal polarizations with its cross-track scanning geometry. The Saharan and Taklimakan deserts are taken as examples due to the relatively homogeneous surface conditions. In the two 150 GHz channels of MWHS, the polarization bias is corrected according to the measurements at the Earth incidence angle (EIA) of 0°. The monthly-mean quasi-polarization difference (QPD) at 150 GHz is found to be varying with the EIA and exhibits seasonal variations over deserts. The QPD reaches a maximum value at the EIA of ~35°, while the zero value appears near the EIA of ~53° (equal to the satellite viewing angle of 45°) as expected. In contrast to the relatively stable and low QPD over Sahara, the QPD, quasi polarized emissivity difference and pure polarized emissivity difference are generally larger in the Taklimakan Desert, where the maximum monthly QPD is ~4 K and the polarized emissivity difference increases monotonously to ~0.2 at the EIA of 50°. The complex surface parameters and temporal variabilities impinge on the uncertainties of the land polarization. The increasing soil moisture due to precipitation damps the dichroic ability of the land surface, while the frozen surface due to snowfalls in cold seasons enhances the polarization.

A water-logging disaster occurred in Eastern China on 1 June 2016 was utilized to investigate the practical performance of six radar rainfall estimators based on horizontal reflectivity ($Z_{\mathrm{H}}$), specific attenuation ($A_{\mathrm{H}}$), specific differential phase ($K_{\text{DP}}$), and multi-variable estimators that integrate differential reflectivity ($Z_{\text{DR}}$), namely$R(Z_{\mathrm{H}},\, Z_{\text{DR}}), R(K_{\text{DP}}, Z_{\text{DR}})$and$R(A_{\mathrm{H}}, Z_{\text{DR}})$. Detailed evaluation with a local rain gauge network and drop size distribution (DSD) measurements shows that (i)$R(A_{\mathrm{H}},\, Z_{\text{DR}})$underestimates the light rain pattern, but it achieves the best scores and performs the best among the various estimators; (ii) each radar rainfall estimator can outperform other estimators at a certain period of time determined by the rainfall patterns; (iii) both the optimal radar rainfall relationship and high calibration accuracy are required to obtain accurate rainfall estimates; (iv) the contamination of melting solid hydrometeors on$A_{\mathrm{H}} \text{and}/\text{or}K_{\text{DP}}$may make them less effective than$Z_{\mathrm{H}}$. In addition, with appropriate adjustment of$\alpha$coefficient,$R(A_{\mathrm{H}})$can perform better than$R(K_{\text{DP}})$.

Microwave Humidity and Temperature Sounder (MWHTS) and the Microwave Temperature Sounder (MWTS) are two sensors onboard the Fengyun-3D (FY-3D) polar-orbiting meteorological satellite to detect the atmospheric humidity and temperature, respectively. Not only that, these two sensors also have a certain ability to detect precipitation. Channels of MWHTS designed near 118. 75-GHz and the channels of MWTS designed near 50-60-GHz are used to detect the atmospheric vertical temperature distribution. In this paper, the global ocean and land precipitation retrieval have been studied combining the MWHTS and MWTS. The results show that three groups of channels from the sensors, (118.75+2.5-GHz and 52.8-GHz), (118.75+3.0-GHz and 51.76-GHz) and (118.75+5.0-GHz and 50.3-GHz), improve the accuracy of global ocean and land precipitation retrieval, especially the land precipitation retrieval effect. This brings new ideas and methods to enhance the application of land precipitation retrieval in the future.

Compared to the legacy GOES Imager, the GOES-16 Advanced Baseline Imager (ABI) provides measurements at much higher resolution in both spatial and temporal dimensions, which benefits many applications such as rainfall rate estimation. However, it is challenging to quantify the water droplets in the cloud and precipitation intensity with only the Infrared (IR) radiation and converted brightness temperature information. Comparison between ground radar rainfall estimates and the operational GOES-16 rain rate products indicates that uncertainty associated with GOES-16 rain rate estimates is significant. This paper proposes an innovative deep learning system for precipitation estimation using measurements from GOES-16/ ABI. Cloud-top brightness temperature information observed by channels 8/10/11/14/15 of the ABI are used as input to this deep learning framework. The rainfall estimates from a ground radar network are used as target labels in the training phase. Independent verification shows that the deep learning-based rainfall system can estimate precipitation time, intensity, and amount very well, especially in heavy rain regions.

A torrential flood event occurred over the complex terrain in Zhejiang on 23 June 2015 is investigated utilizing the first routinely operational C-band polarimetric radar in China. The polarimetric radar quantitative precipitation estimation (QPE) performance is verified using a local rain gauge network, and the microphysical characteristics of the rainstorm are revealed based on polarimetric radar variables. The results show that (i) radar QPE estimator based on KDP performs the best among all estimators; (ii) the rainstorm upon the rainfall center area was dominated by small-moderate sized raindrops with mean volume diameter less than 2 mm, but high raindrop concentration with log10(Nw) exceeding 5 mm-1m-3, resulting in rather high liquid water content; (iii) small hailstones were falling and melting upon the intense rainfall area between gauge stations, which compounded the complex precipitation structure and enhanced raindrop concentration.

Recent advances in low-power millimeter wave low-noise amplifier technologies have enabled the host of high performance atmospheric sounding sensors on ground-based instruments. In this paper, frequencies at K-band (22-31 GHz) and V-band (51-59 GHz) are chosen to retrieve atmospheric temperature and water vapor profiles. The specifications including sensitivity, integral time along with the calibration accuracy for all channels are presented. The key techniques such as calibration method and retrieving algorithm are described. In addition, measurements during two on-site experiments are presented to demonstrate the prototype performance in terms of calibrated brightness temperatures and retrievals (temperature and humidity) using radiosonde data as validation references. Besides the meteorological applications, a potential climate research in different seasons is provided based on a long term of observations.

This paper focuses on the evaluation of FY-3C MWHTS in terms of the calibration/validation exercise and initial assimilation trials in extreme weather. The observations are qualified for atmospheric profile retrievals and data assimilation by monitoring the on-orbit specifications of MWHTS. Experiments based on WRFDA were carried on and a case study is provided with track and intensity analysis. The discussion shows that the impact of MWHTS observations in assimilation trials over tropical cyclone Rammsun is significantly positive in the short range over the Western Ocean. The results of this paper suggest that MWHTS provides additional information of 118GHz, which is firstly used in meteorological satellite, also shows positive impact in the assimilation system.

Compared to existing polar-orbiting satellites, the small satellite constellation is of low-cost, rapidly deployable and mission-flexible. Meanwhile, a series of challenges are followed in aspects of size, weight, life, stability, detecting accuracy, consistency of multi-satellite and so on. This paper mainly focuses on the characteristic of diode detector for Microsat microwave radiometer. Given the certain observation target, the retrieved brightness temperatures would have changed correspondingly under different system AGC (Automatic Gain control) values. By adjusting the system gain, a little change happened but still in normal workspace. The variation caused by nonlinearity of diode, by using two-point calibration method, cannot be completely eliminated. Setting a wide range of 3-350K, the experimental results demonstrate that there is obvious nonlinearity for brightness temperatures between retrievals minus actual values and observations. So, in the procedure of real-time calibration for Microsat microwave radiometer, the system must be assured working in approximately linear workplace with a certain and reasonable AGC value.

Precipitation is a critical element in global atmospheric circulation and ecosystem. However, it is challenging to monitor the global or even continental scale precipitation features using ground-based rain gauges due to the spatial coverage limitations. The Geostationary Operational Environmental Satellite-R (GOES-R) series provide new opportunities for continuous observation of precipitation at large scales. This paper presents a detailed cross-comparison of quantitative precipitation estimates (QPE) between GOES-R (GOES-16) and the ground radar-based rainfall product derived from the National Ocean and Atmospheric Administration's (NOAA) multi-radar multi-sensor (MRMS) system over the continental United States (CONUS). The precipitation detectability of GOES-R is investigated using MRMS products as references. In addition, uncertainties associated with the GOES-R precipitation estimates are quantified in different regions over the CONUS.

On November 15, 2017, the fourth satellite, Feng Yun-3D (FY-3D), of the new generation of Chinese polar orbit meteorological satellites was successfully launched into orbit. As one of the key payloads, the second-generation Microwave Humidity Sounder (MWHS II) has 15 channels for observing atmospheric temperature and moisture. In the ground data processing system, the calibration is completed for every scanning period, and then, brightness temperature (TB) data are obtained with calibration coefficients. In order to analyze the performance of MWHS II, one year of in-orbit data are used to monitor the trend of internal blackbody target temperature, instrument temperature, calibration counts, and automatic gain control (AGC), and the results indicate whether the instrument is working well. The instrument noise equivalent differential temperature (NEDT) is calculated, and the value satisfies the design requirements. Two methods are used to validate FY-3D MWHS II measurements. One is the simultaneous nadir overpass (SNO) approach: in this method, ATMS is chosen as the reference sensor, and the standard deviations for five humidity sounding channels are all less than 1.3 K. In the alternate approach, a comparison of the observed and simulated TB of MWHS II is carried out between FY-3C and FY-3D. The results also demonstrate a consistent performance between the two instruments.

Quantitative Precipitation Estimation (QPE) is one of the most important applications of weather radars. However, it is difficult to obtain an optimal Z-R relation that can represent the local variability in precipitation microphysics. This study implements an adaptive radar QPE scheme based on the Storm Cell Identification and Tracking (SCIT) algorithm for Doppler radar and rain gauge measurements from Southwest China. The performance of this innovative QPE system is demonstrated using four precipitation events featured by different meteorological characteristics. Evaluation results show that the SCIT-based rainfall approach performs better than conventional Z-R based algorithms.

The evolution process of hurricane Sandy (Oct 20-10.29, 2012) was analyszed using satellite remote sensing observations on polar-orbiting(MWHS on Chinese meteorological satellite FY-3B, GMI on GPM satellite) and simulations on geostationary orbit (designed for FY-4M), conventional datasets and forcasting utilizing the mesoscale Weather Research and Forecasting (WRF) model at temporal and spatial resolution of 15 km and 5 minutes. WRF Data Assimilation (WRFDA) model is utilized to forecast the track and intensity of hurricane Sandy with radiance described above, and the forecast results are cross-compared with the best track to verify the track and intensity of previous forecasts and analysis results, which proposes a kind of novel observations to improve the track and intensity for future hurricanes.

There are atmospheric temperature sounding channels on the new generation of Microwave Humidity and Temperature Sounder (MWHTS) and the Microwave Temperature Sounder (MWTS) onboard the FY-3D polar-orbiting meteorological satellite, which are set at frequencies near 118.75-GHz and 50~60-GHz, respectively. These atmospheric temperature sounding channels are used to analyze sensitivity to precipitation over ocean and land, respectively. In this paper, data from the MWHTS, MWTS and the Tropical Rainfall Measuring Mission (TRMM) Multi-Satellite Precipitation Analysis (TMPA) 3B42 are matched in time and space. Then, combined with the MWHTS and MWTS microwave data, the global ocean and land precipitation sensitivities are analyzed separately. The results demonstrate that three groups of channels, (118.75+2.5-GHz and 52.8-GHz), (118.75+3.0-GHz and 51.76-GHz) and (118.75+5.0-GHz and 50.3-GHz), are at the same height, and the corresponding brightness temperatures have good consistency. The application of these channels will deserve further research in the future.

The microwave radiation data from the microwave humidity and temperature sounder (MWHTS) onboard FY-3C meteorological satellite was employed in the data assimilation system to estimate the impact of this data on typhoon forecasts. 118.75-GHz and 183.31-GHz channels from the MWHTS provide atmospheric temperature and humidity profile measurements, respectively. These measurements play critical roles forecasting the path of the typhoon and pressure of the typhoon center. In this paper, the data from the MWHTS are implemented in the Weather Research and Forecasting (WRF) model data assimilation system (WRFDA) to forecast the path of the typhoon and pressure of the typhoon center. The results demonstrate that the path prediction of the typhoon has been improved, but the error of the forecast pressure did not decrease significantly. It can be concluded that the data of the 118.75-GHz and 183.31-GHz channels from the MWHTS for predicting the path of the typhoon is effective. In particular, the 118 GHz frequency is the first time applied to polar orbiting meteorological satellites in the world. The application of the 118-GHz channels in data assimilation will deserve further research in the future.

Typhoon is often accompanied by strong convective weather such as high winds and heavy rainfall. The dualpolarization radar observations show a great performance for quantitative precipitation estimation (QPE) over traditional single-polarization radar by gleaning more useful information about precipitation particle size and shape distributions. According to the simulation of raindrop size distribution data from disdrometers in Guangzhou, China, this paper established a localized QPE algorithm for three typhoons landing in southern China. This regional QPE algorithm was compared with various rainfall relations such as the default Z- R relationship (Z = 300R1.4) adopted by the WSR-88D. Results show that the rainfall estimates with localized algorithms approximate to rainfall observations from surface meteorological stations. The localized QPE algorithm is more accurate and reliable than other algorithms for typhoon events over southern China.

An advanced terahertz atmospheric profiling sounder for Chinese next generation meteorological satellite (FY-5 satellite) is introduced in this paper, driven by recent advances in microwave device technology that now permit broad frequency bands and higher frequencies into more sounding channels in order to not only improve both the vertical and horizontal resolutions of the retrieved atmospheric profile, but also enhance sounding capability of atmospheric hydrometeor parameters, like water cloud, ice, snow, rain and gaupel. Global simulation studies over ocean and land in clear and cloudy atmospheres using WMO radiosonde datesets and NWP reanalysis are presented that assess the temperature, moisture, and precipitation sounding capability with channels sampled near the 89, 118.75, 183.31, 380 and 425GHz absorption lines. Channel specification and configuration are presented after channel correlation and retrieval demonstration, and the distribution of subsystem units are determined based on previous design experience and requirements of satellite platform.

A newly designed thermal/vacuum (T/V) prelaunch multiangle calibration test is proposed for Microwave Humidity and Temperature Sounder (MWHTS) onboard the Feng Yun 3D satellite. Compared with other existing prelaunch calibration tests designed at fix scan angle, this test is first proposed to analyze the measurements of MWHTS from multiscan angles. A set of comprehensive calibration method is established and used for calibration data processing. The high-quality data preprocessing methods are performed. Essential calibration coefficients such as cold bias, hot bias, and nonlinearity coefficients, and calibration results such as calibration residual error, sensitivity, and calibration accuracy of MWHTS are all obtained and analyzed in MWHTS's six observing positions. The measured sensitivity value of channel 2 is 1.5 K while the measured sensitivities of the others range from 0.18 to 0.57 K. The calibration accuracy of channel 2 is 1.5 K while the calibration accuracies of the others range from 0.32 to 0.7 K. According to the discrepancy of multiangle calibration test results, the radiation leakage and the response lag for special channels are discovered for the first time in T/V test, and the reasons of these two special phenomena are fully analyzed. Moreover, the measurements of the T/V test with fast changing instrument temperatures are analyzed and the applicability of nonlinearity coefficients obtained in T/V test for in-orbit calibration is verified. In conclusion, MWHTS meets the basic design requirements of sensitivity and calibration accuracy, the changing of the MWHTS observing positions does not impact the calibration coefficients and results, and the nonlinearity coefficients obtained in T/V test are valid when instrument temperature experiences some fast changing.

This paper focuses on precipitation detection using microwave humidity temperature sounder (MWHS-II) onboard FY-3C satellite. Some of its channels are sensitive to moisture at different atmospheric altitudes and provide vertical precipitation information. In this paper, precipitation detection algorithm over ocean using scatter index (SI) and over land using direct classification are proposed, then rain rate retrieval algorithm is completed on the basis of the precipitation detection algorithm. For ocean, compared with the Level 2 precipitation detection data product of FY3C MWHS-II, the correctness of the ocean precipitation detection algorithm is close to 100% (| latitude |50°), and compared with TMPA 3B42 data product, it can reach 96.5%. For land, compared with the TMPA 3B42 data product, its accuracy is higher than 93%. It can be seen that the proposed algorithm for detecting precipitation for ocean and land is effective.

The paper introduces the design and development of MWHTS system and quantitatively evaluates the stability of its post-launch performance (3 years and 3 months). The on-orbit assessment of MWHTS demonstrates that the MWHTS onboard FY-3C has been improved compared to it on FY-3A and FY-3B. Furthermore, using the observing data from MTHTS shows that the instrument plays an important role in monitor extreme climate, especially for typhoon between June to Sept in 2016, including the procedure of generating, evolution, strengthen and die out, and also including the heavy rainfall caused by typhoon, which is compared against ground-based observations (gauge) and products blended by sensors onboard TRMM and GPM.

Total precipitable water (TPW) plays a major role to short range weather prediction as precipitation, flash flood and other severe weather which are closed related to distribution of water vapor. Clouds are important in the global climate change and weather as clouds control the planetary albedo and are precursor of precipitation. Cloud Liquid Water (CLW) also plays a key role in the transport of energy in the earth-atmosphere system and is identified as one of the most important factors, which is used by researcher and operation forecaster to access cloud properties and aircraft icing. The measurements of TPW and CLW from observations of Radiosonde (RAOBs), ground-based microwave radiometers and research aircrafts have been well documented by previous studies [Guan et al 2002; Cober et al. 1996; Han and Westwater 1995; Solheim et al. 1998; Vaillancourt et al. 2003; Tremblay et al., 2003]. Weng F.Z used to retrieve TPW and CLW from Jason-2 AMR and AMSU-A observations on board NOAA satellite. But until now, few researchers retrieve the TPW and CLW combing MWHTS (MicroWave Humidity and Temperature Sounder) and ACMR (Atmospheric Correction Microwave Radiometer) on board Chinese polar orbiting satellites FY-3C and HY-2A.

This paper focuses on rainfall retrievals using 118GHz and 183GHz channels of microwave humidity temperature sounder (MWHS-II), which has been launched onboard FY-3C satellite. These channels contain various information about the rain. The dataset of FY-3C and GPM are matched in the aspects of time and location and the retrieval algorithm is established. Using the 118GHz and 183GHz channels, the correlation coefficients of retrieval for the ocean and land are 0.8044 and 0.7001 respectively. However, the correlation coefficients are 0.6473 and 0.5438 respectively without using the 118GHz channels, and the result are 0.7284 and 0.5611 respectively without using the 183GHz channels. Comparing the result, we analyze the sensitivity of the 118GHz and 183GHz using the Community Radiative Transfer Model (CRTM).

The Geostationary Interferometric Microwave Sounder (GIMS) is a synthetic aperture microwave sounder working in time-sharing sampling mode with a rotating circular antenna array, thus having a relatively long imaging period. Since target motion in the imaging period will pose a problem to imaging effect, observing dynamic target such as fast changing weather of tropical cyclones will introduce imaging error to the retrieved image of GIMS. A method that combines Kalman filter and interpolation to reduce imaging error are presented, which utilizes a time sequence of visibilities collected by time-sharing sampling method. Simulations of GIMS's observation process in viewing a series of near real case brightness temperature maps modeled by the National Center for Environmental Prediction Final Operational Global Analysis data/Weather Research and Forecasting Model/Radiative Transfer for Television Infrared Observation Satellite Operational Vertical Sounder method, together with postprocessing of dynamic observation error-correction processing and image retrieval are conducted for the method. Results show that the method can reduce imaging error even if there are random noises in visibilities.

An one-dimensional variational retrieval system was developed to retrieve the clear sky atmospheric temperature and humidity profiles over land using the measurements of microwave humidity-temperature sounder (MWHTS) on Chinese FY-3C satellite. The system parameters are configured by analyzing the MWHTS channel properties and the climate condition over land. The retrieval results are evaluated by root mean square error (rmse) with respect to European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis data. The validated results show that the maximum root mean square error of temperature and humidity are 2.59K and 11.87%, respectively. The retrieval results, compared with National Centers for Environmental Prediction (NCEP) 6 hour forecast profiles, show that the background profiles can affect the accuracy of retrieval profiles and FY-3C/MWHTS measurements can improve forecast precision of humidity.

High-altitude cirrus clouds are particularly common in the Tibetan Plateau, which is populated by irregular ice crystals with complex scattering and absorption characteristics. Given the scarcity of ground probing sites, the lack of observational data, laser radar and infrared and visible light detection forces us to develop a new sounding method. In this paper, combined cloud products from CloudSat and MODIS, the retrieval algorithm of Dme and IWC from MWHS data (89 and 150 GHz) onboard Chinese FY-3B/C meteorological satellite is described and analyzed in Tibetan Plateau and the authors analyze the distribution of cirrus in Tibetan plateau and derive the ice water content (IWC) and median mass equivalent sphere diameter (Dme) of each microphysical sample. Then the analysis of cirrus clouds distribution over seasonal and annual variations of the Tibetan Plateau during a 1-year period can be provided, and it is important for researchers to analyze the impact of this region to China and global climate through cirrus clouds parameters.

A variational method based on 1Dvar is proposed to retrieve Integrated Precipitable Water vapor (IPW) in typhoon area from brightness temperatures measured by the Microwave Humidity and Temperature Sounder (MWHTS) on the Chinese Fengyun 3C (FY-3C) polar-orbit meteorological satellite. Water vapor values provided by European Centre for Medium-Range Weather Forecasts (ECMWF) were used as background. The performance of the retrieval method was demonstrated by using an independent dataset of MWHTS observations and the corresponding total water vapor values from ECMWF. Results were compared with the measurements obtained from radiosonde, NCEP/WRF and MiRS software.

Imaging period is an important consideration to geostationary interferometric microwave sounder (GIMS) when mapping fast changing target such as typhoon. GIMS simulation system with near real case observation target can evaluate system performance in different system configurations and thus help determine the optimal imaging period. In this paper, GIMS simulation system using MATLAB and near real case observation modeled by FNL/WRF/RTTOV method has been used to analyze the effect of imaging period on image quality. System simulation results for each frequency channel will be presented and analyses of imaging period's effect on image quality will also be given.

The paper develops a passive sub-millimeter atmospheric profile and precipitation retrievals algorithm for Microwave Humidity and Temperature Sounder (MWHTS) onboard the Chinese Feng Yu n 3C (FY-3C) satellite. The retrieval algorithm employs a number of neural network estimators trained and evaluated using the validated global reference physical model NCEP/WRF/ARTS, and works for land and seawater with latitude between -30 to 30 degree. To simply the calculation procedure and save the training time, principle component analysis was adapted to filter out the redundancy caused by scanning angle and surface effects, as well as system noise. NCEP data per 6 hours are downloaded to run the Weather Research and Forecast model WRF, and derive the typical precipitation data from the whole world. The Atmospheric Radiative Transfer Simulator ARTS is feasible for performing simulations of atmospheric radiative transfer.

Target brightness temperature maps can be used in geostationary interferometric microwave sounder (GIMS) system simulation. System simulation with accurate target brightness temperature maps can evaluate system performance in near real case and thus help adjust design parameters for the sensor before it is finally put into use. In this paper, method of simulating target brightness temperature using Weather Research and Forecasting Model and Radiative Transfer for TOVS (RTTOV) has been discussed. Target brightness temperature simulation results at oxygen absorption band and water-vapor absorption band have been presented. Some preliminary analyses of simulated brightness temperature for GIMS' observation have also been given.

The Advanced Microwave Atmospheric Sounder (AMAS) is the new generation of Microwave Humidity Sounder (MWHS) onboard the Feng Yun 3 C/D (FY-3C/D) satellite and follows the heritage and development of MWHS onboard the FY-3(A/B) satellite. AMAS onboard the FY-3C satellite is a 15-channel total power microwave radiometer in the range of 89-191 GHz scheduled to be launched on September 23, 2013. Compared to MWHS onboard FY-3A/B, AMAS improves channel characteristics by adding eight horizontal polarized channels near 118.75 GHz, which is the first operational polar-orbiting satellite-based sensor to observe the atmosphere in Earth-scanning mode in the 118-GHz oxygen band. Also, AMAS has more channels at 183 GHz than MWHS. This paper analyzes the channel capability and radiometric characteristics of AMAS at 118.75 GHz. Before the launch of FY-3C, the intensive thermal vacuum (T/V) tests for AMAS were carried out in a 2-m T/V chamber, and the basic parameters were obtained, such as the receiver nonlinearity and sensitivity of each channel for AMAS. Furthermore, system nonlinear error correction and bias correction of warm and cold targets are derived after the T/V data analysis and will be used for calibration processing, playing an important role in level 1 and 2 data processing. Accuracies of calibrated channels in AMAS range from 0.48 K to 2.7 K.

Respect to ground-based microwave radiometer, the paper presents exponent calibration based on blackbody cooled by liquid nitrogen. In order to correct the calibration coefficients, this paper also presents tipping method at low optical depth (K band), which is different from common tipping method. It observes the clear-sky and clear-sky with noise injection to correct nonlinear factor and stability of noise. The calibration results show that using tipping method can achieve high resolution.

Design and Technical specification parameters of MWHS-II (MicroWaves Humidity Sounder) of FY-3 satellite are presented, which include much improvements compared to MWHS onboard FY-3A/B satellite launched in 2008 and 2010. Especially MWHS-II adds 8 channels at 118.75GHz to sound temperature information for the first time internationally. The simulation results show that MWHS-II will play an important role in the meteorological sounding system for measuring global atmospheric temperature and water vapour profiles.