Jieying He

Design of the second generation microwave humidity sounder (MWHS-II) for Chinese meteorological satellite FY-3

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.

Effects of seed dot layer and thin GaAs spacer layer on the structure and optical properties of upper In(Ga)As quantum dots

The structure and optical properties of In(Ga)As with the introduction of InGaAlAs or InAlAs seed dot layers are investigated. The area density and size homogeneity of the upper InGaAs dots are efficiently improved by the introduction of a buried layer of high-density dots. Our explanation for the realization of high density and size homogeneity dots is presented. When the GaAs spacer layer is too thin to cover the seed dots, the upper dots exhibit some optical properties like those of a quantum well. By analyzing the growth dynamics, we refer to this kind of dot as an empty-core dot.

Structure and optical properties of upper In(Ga)As quantum dots on a different seed layer with a thin GaAs spacer layer

The structure and optical properties of In(Ga)As grown with the introduction of InGaAlAs or InAlAs seed dots layers are investigated. The area density and size homogeneity of the upper InGaAs dots are efficiently improved with the introduction of a layer of high-density buried dots. When the GaAs spacer layer is too thin to cover the seed dots, the upper dots exhibit the characterization of a quantum well. By analyzing the growth dynamics, we refer to it as an empty-core structure dot

In-orbit performance of microwave humidity and temperature sounder (MWHTS) of the Chinese FY-3C meteorological satellite

FY-3C (FengYun 3C) meteorological satellite of China was successfully launched on Sept 23, 2013. MWHTS (MicroWave Humidity and Temperature Sounder) was a very important payload for measuring global atmospheric water vapour profiles; also, it adds 8 channels at 118.75GHz to sound temperature information for the first time internationally for polar-orbit satellite. In this paper, the authors will describe the system configuration and parameters of MWHTS. Moreover it gives the testing results in-orbit and comparing with AMSU-B which has been installed on NOAA-17 and MWHS-I onboard FY-3A/B satellite.

The retrievals and analysis of clear‐sky water vapor density in the Arctic regions from MWHS measurements on FY‐3A satellite

The atmospheric humidity profiles of clear sky in the Arctic regions were retrieved from the microwave humidity sounder on Chinas FY-3A satellite using the back-propagation neural network algorithm. The algorithm was developed using the reliable measurements of surface temperature, humidity, and pressure as well as atmospheric temperature and humidity profiles from radiosonde observations. Considering the influence of sounding geometry, different surface types, and atmospheric conditions, we improved the commonly used back-propagation artificial neural network by treating the Mexican hat wavelet function as a transfer function and transforming the input data space. The retrieved root-mean-square (RMS) error is about 0.12 g/m(3) in absolute humidity (water vapor density) profiles and 12.7% in relative humidity profiles. Water vapor density retrievals in winter are in acceptable agreement with profiles from radiosonde, but the agreement of the summer data was not as good. Furthermore, the retrieval model has been used in another Arctic station with a mean water vapor density RMS error of 0.185 g/m(3) and 18.3% for a relative humidity profile for all seasons in 2008 at 12:00 UT.

The analysis of atmospheric absorption model based on ground-based microwave radiometer

The paper introduces two widely used atmospheric absorption models: MPM by Liebe in 1989 and Ulaby in 1976. Compare between them based on ground-based microwave radiometer, this paper presents an atmospheric absorption model with improvement including local line absorption, noresonant dry air spectrum, water vapor continuum, suspended water droplet refractivity and rain effects. Also, using the improved absorption model, the paper simulates the temperature and humidity weighting functions and brightness temperature. The results show that in the retrievals of ground-based microwave radiometer, the improvement of atmospheric absorption can derive more accurate brightness temperatures which are more agreement with the actual measuring brightness temperatures.

Rainfall retrievals using 118GHz and 183GHz channels of MWHS-II on FY-3C Meteorological satellite

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).

T/V Calibration for Microwave Humidity and Temperature Sounder onboard Chinese FY-3D satellite

The Microwave Humidity and Temperature Sounder, MWHTS, is being developed to fly on the new generation of FengYun polar orbiters, which is named FY-3D and due to be launched in the latter half of 2016. MWHTS with 15 channels in the range of 89 ~ 190 GHz is designed for atmospheric humidity and temperature sounding, and also for monitoring severe weather systems such as typhoons and rainstorms. Before the launch of MWHTS, a extensive series of experiments will be conducted in a thermal/vacuum (T/V) chamber to determine radiometric characteristics performance and verify the calibration method, which are of very importance before the launch. This paper presents an improved T/V Calibration design, which is useful in orbit operation and performance assessment and is necessary for better calibration accuracy.

Terahertz metasurface-based devices for wavefront modulation

Terahertz (THz) radiation has attracted a lot of attentions due to its fascinating potential applications. However, the traditional THz devices have relatively large size due to the long wavelength nature of the THz radiation. Several metasurface-based THz devices, including lens, computer generated holograms, spin selected focusing lens, as well as wavelength selected diffractive elements, have been demonstrated. The thickness of these device is only 1/4000 of the working wavelength. A THz focusing plane imaging system is employed to characterize the function devices. Experiment results demonstrated the validity of this new method.

A deblurring method for dynamic target observation of the geostationary interferometric microwave sounder (GIMS)

Brightness temperature change of observation target in one imaging period will introduce image blur to the retrieved image of geostationary interferometric microwave sounder (GIMS), which uses rotating circular array to realize time-sharing sampling other than snap-shot to reduce system complexity but meanwhile resulting in a relatively long imaging period. In this paper, an interpolation method utilizing time sequence of visibilities collected by time-sharing sampling is presented. The method is verified through a simulation system that simulates GIMSs observation process in viewing a series of near real case brightness temperature maps modeled by FNL/WRF/RTTOV method. Results show that the interpolation method can de-blur the image and reduce imaging error to the degree of snap-shot imaging.