Cloud-Type-Dependent 1DVAR Algorithm for Retrieving Hydrometeors and Precipitation in Tropical Cyclone Nanmadol from GMI Data

Understanding the structure of tropical cyclone(TC)hydrometeors is crucial for detecting the changes in the distribution and intensity of precipitation.In this study,the GMI brightness temperature and cloud-dependent 1DVAR algorithm were used to retrieve the hydrometeor profiles and surface rain rate of TC Nanmadol(2022).The Advanced Radiative Transfer Modeling System(ARMS)was used to calculate the Jacobian and degrees of freedom(△DOF)of cloud water,rainwater,and graupel for different channels of GMI in convective conditions.The retrieval results were compared with the Dual-frequency Precipitation Radar(DPR),GMI 2A,and IMERG products.It is shown that from all channels of GMI,rain water has the highest△DOF,at 1.72.According to the radiance Jacobian to atmospheric state variables,cloud water emission dominates its scattering.For rain water,the emission of channels 1–4 dominates scattering.Compared with the GMI 2A precipitation product,the 1DVAR precipitation rate has a higher correlation coefficient(0.713)with the IMERG product and can better reflect the location of TC precipitation.Near the TC eyewall,the highest radar echo top indicates strong convection.Near the melting layer where Ka-band attenuation is strong,the double frequency difference of DPR data reflects the location of the melting.The DPR drop size distribution(DSD)product shows that there is a significant increase in particle size below the melting layer in the spiral rain band.Thus,the particle size may be one of the main reasons for the smaller rain water below the melting layer retrieved from 1DVAR.

A cloud optical and microphysical property product for the advanced geosynchronous radiation imager onboard China's Fengyun-4 satellites: The first version

风云四号作为中国新一代静止气象卫星,提供了高时空分辨率的监测产品。本文介绍风云四号搭载的先进地球同步轨道辐射成像仪AGRI的云光学和微物理特性产品.该产品包含了基于双光谱通道反演的云光学厚度和云粒子有效半径产品,以及基于机器学习的云识别和云相态产品。与时空匹配的主动卫星观测结果对比显示,该产品的云识别和云相态的准确率分别在95%和85%;该产品提供的云光学厚度和云有效粒径与经典的MODIS产品的相关系数达到0.76和0.63.团队将持续优化和更新该云光学和微物理特性定量产品,服务风云四号卫星定量应用。

A Multi-Domain Compression Radiative Transfer Model for the Fengyun-4 Geosynchronous Interferometric Infrared Sounder (GIIRS)

Forward radiative transfer(RT)models are essential for atmospheric applications such as remote sensing and weather and climate models,where computational efficiency becomes equally as important as accuracy for high-resolution hyperspectral measurements that need rigorous RT simulations for thousands of channels.This study introduces a fast and accurate RT model for the hyperspectral infrared(HIR)sounder based on principal component analysis(PCA)or machine learning(i.e.,neural network,NN).The Geosynchronous Interferometric Infrared Sounder(GIIRS),the first HIR sounder onboard the geostationary Fengyun-4 satellites,is considered to be a candidate example for model development and validation.Our method uses either PCA or NN(PCA/NN)twice for the atmospheric transmittance and radiance,respectively,to reduce the number of independent but similar simulations to accelerate RT simulations;thereby,it is referred to as a multi-domain compression model.The first PCA/NN gives monochromatic gas transmittance in both spectral and atmospheric pressure domains for each gas independently.The second PCA/NN is performed in the traditional spectral radiance domain.Meanwhile,a new method is introduced to choose representative variables for the PCA/NN scheme developments.The model is three orders of magnitude faster than the standard line-by-line-based simulations with averaged brightness temperature difference(BTD)less than 0.1 K,and the compressions based on PCA or NN methods result in comparable efficiency and accuracy.Our fast model not only avoids an excessively complicated transmittance scheme by using PCA/NN but is also highly flexible for hyperspectral instruments with similar spectral ranges simply by updating the corresponding spectral response functions.

Extreme space weather events caused by super active regions during solar cycles 21-24

Extreme space weather events including≥X5.0 flares,ground level enhancement(GLE)events and super geomagnetic storms(Dst≥-250 nT)caused by super active regions(SARs)during solar cycles 21-24 were studied.The total number ofX5.0 solar flares was 62,among which 41 were X5.0-X9.9 flares and 21 were≥X10.0 flares.We found that 83.9%of the≥X5.0 flares were produced by SARs;78.05%of the X5.0-X9.9 and 95.24%of the≥X10.0 solar flares were produced by SARs;46 GLEs were registered during solar cycles 21-24,and 25 GLEs were caused by SARs,indicating that 54.3%of the GLEs were caused by SARs;24 super geomagnetic storms were recorded during solar cycles 21-24,and 12 of them were caused by SARs,namely 50%of the super geomagnetic storms were caused by SARs.We ascertained that only 29 SARs produced≥X5.0 flares,15 SARs generated GLEs and 10 SARs triggered super geomagnetic storms.Of the 51 SARs,only 33 SARs produced at least one extreme space weather event,while none of the other 18 SARs could trigger an extreme space weather event.There were only four SARs and each of them generated not only a≥X5.0 flare,but also a GLE event and a super geomagnetic storm.Most of the extreme space weather events caused by the SARs appeared during solar cycles 22 and 23,especially for GLE events and super geomagnetic storms.The longitudinal distributions of source locations for the extreme space weather events caused by SARs were also studied.

Fusion SST from Infrared and Microwave Measurement of FY-3D Meteorological Satellite

Sea surface temperature(SST)is one of the important parameters of global ocean and climate research,which can be retrieved by satellite infrared and passive microwave remote sensing instruments.While satellite infrared SST offers high spatial resolution,it is limited by cloud cover.On the other hand,passive microwave SST provides all-weather observation but suffers from poor spatial resolution and susceptibility to environmental factors such as rainfall,coastal effects,and high wind speeds.To achieve high-precision,comprehensive,and high-resolution SST data,it is essential to fuse infrared and microwave SST measurements.In this study,data from the Fengyun-3D(FY-3D)medium resolution spectral imager II(MERSI-II)SST and microwave imager(MWRI)SST were fused.Firstly,the accuracy of both MERSIII SST and MWRI SST was verified,and the latter was bilinearly interpolated to match the 5km resolution grid of MERSI SST.After pretreatment and quality control of MERSI SST and MWRI SST,a Piece-Wise Regression method was employed to correct biases in MWRI SST.Subsequently,SST data were selected based on spatial resolution and accuracy within a 3-day window of the analysis date.Finally,an optimal interpolation method was applied to fuse the FY-3D MERSI-II SST and MWRI SST.The results demonstrated a significant improvement in spatial coverage compared to MERSI-II SST and MWRI SST.Furthermore,the fusion SST retained true spatial distribution details and exhibited an accuracy of–0.12±0.74℃compared to OSTIA SST.This study has improved the accuracy of FY satellite fusion SST products in China.

Improving Satellite-Retrieved Cloud Base Height with Ground-Based Cloud Radar Measurements

Cloud base height(CBH) is a crucial parameter for cloud radiative effect estimates, climate change simulations, and aviation guidance. However, due to the limited information on cloud vertical structures included in passive satellite radiometer observations, few operational satellite CBH products are currently available. This study presents a new method for retrieving CBH from satellite radiometers. The method first uses the combined measurements of satellite radiometers and ground-based cloud radars to develop a lookup table(LUT) of effective cloud water content(ECWC), representing the vertically varying cloud water content. This LUT allows for the conversion of cloud water path to cloud geometric thickness(CGT), enabling the estimation of CBH as the difference between cloud top height and CGT. Detailed comparative analysis of CBH estimates from the state-of-the-art ECWC LUT are conducted against four ground-based millimeter-wave cloud radar(MMCR) measurements, and results show that the mean bias(correlation coefficient) is0.18±1.79 km(0.73), which is lower(higher) than 0.23±2.11 km(0.67) as derived from the combined measurements of satellite radiometers and satellite radar-lidar(i.e., Cloud Sat and CALIPSO). Furthermore, the percentages of the CBH biases within 250 m increase by 5% to 10%, which varies by location. This indicates that the CBH estimates from our algorithm are more consistent with ground-based MMCR measurements. Therefore, this algorithm shows great potential for further improvement of the CBH retrievals as ground-based MMCR are being increasingly included in global surface meteorological observing networks, and the improved CBH retrievals will contribute to better cloud radiative effect estimates.

Recognition of Organizational Morphology of Mesoscale Convective Systems Using Himawari-8 Observations

The onset,evolution,and propagation processes of convective cells can be reflected by the organizational morphology of mesoscale convective systems(MCSs),which are key factors in determining the potential for heavy precipitation.This paper proposed a method for objectively classifying and segmenting MCSs using geosynchronous satellite observations.Validation of the product relative to the classification in radar composite reflectivity imagery indicates that the algorithm offers skill for discriminating between convective and stratiform areas and matched 65%of convective area identifications in radar imagery with a false alarm rate of 39%and an accuracy of 94%.A quantitative evaluation of the similarity between the structures of 50 MCSs randomly obtained from satellite and radar observations shows that the similarity was as high as 60%.For further testing,the organizational modes of the MCS that caused the heavy precipitation in Northwest China on August 21,2016(hereinafter known as the“0821”rainstorm)were identified.It was found that the MCS,accompanied by the“0821”rainstorm,successively exhibited modes of the isolated cell,squall line with parallel stratiform(PS)rain,and non-linear system during its life cycle.Among them,the PS mode might have played a key role in causing this flooding.These findings are in line with previous studies.

Characteristics of Lightning Activity in Southeast China and its Relation to the Atmospheric Background

Based on the lightning observation data from the Fengyun-4A(FY-4A)Lightning Mapping Imager(FY-4A/LMI)and the Lightning Imaging Sensor(LIS)on the International Space Station(ISS),we extract the“event”type data as the lightning detection results.These observations are then compared with the cloud-to-ground(CG)lightning observation data from the China Meteorological Administration.This study focuses on the characteristics of lightning activity in Southeast China,primarily in Jiangxi Province and its adjacent areas,from April to September,2017–2022.In addition,with the fifth-generation European Centre for Medium-Range Weather Forecasts reanalysis data,we further delved into the potential factors influencing the distribution and variations in lightning activity and their primary related factors.Our findings indicate that the lightning frequency and density of the FY-4A/LMI,ISS-LIS and CG data are higher in southern and central Jiangxi,central Fujian Province,and western and central Guangdong Province,while they tend to be lower in eastern Hunan Province.In general,the high-value areas of lightning density for the FY-4A/LMI are located in inland mountainous areas.The lower the latitude is,the higher the CG lightning density is.High-value areas of the CG lightning density are more likely to be located in eastern Fujian and southeastern Zhejiang Province.However,the high-value areas of lightning density for the ISS-LIS are more dispersed,with a scattered distribution in inland mountainous areas and along the coast of eastern Fujian.Thus,the mountainous terrain is closely related to the high-value areas of the lightning density.The locations of the high-value areas of the lightning density for the FY-4A/LMI correspond well with those for the CG observations,and the seasonal variations are also consistent.In contrast,the distribution of the high-value areas of the lightning density for the ISS-LIS is more dispersed.The positions of the peak frequency of the FY-4A/LMI lightning and CG lightning contrast with local altitudes,primarily located at lower altitudes or near mountainsides.K-index and convective available potential energy(CAPE)can better reflect the local boundary layer conditions,where the lightning density is higher and lightning seasonal variations are apparent.There are strong correlations in the annual variations between the dew-point temperature(Td)and CG lightning frequency,and the monthly variations of the dew-point temperature and CAPE are also strongly correlated with monthly variations of CG lightning,while they are weakly correlated with the lightning frequency for the FY-4A/LMI and ISS-LIS.This result reflects that the CAPE shows a remarkable effect on the CG lightning frequency during seasonal transitions.

Forecast daily indices of solar activity, F10.7, using support vector regression method

The 10.7 cm solar radio flux （F10.7）, the value of the solar radio emission flux density at a wavelength of 10.7 cm, is a useful index of solar activity as a proxy for solar extreme ultraviolet radiation. It is meaningful and important to predict F10.7 values accurately for both long-term （months-years） and short-term （days） forecasting, which are often used as inputs in space weather models. This study applies a novel neural network technique, support vector regression （SVR）, to forecasting daily values of F10.7. The aim of this study is to examine the feasibility of SVR in short-term F10.7 forecasting. The approach, based on SVR, reduces the dimension of feature space in the training process by using a kernel-based learning algorithm. Thus, the complexity of the calculation becomes lower and a small amount of training data will be sufficient. The time series of F10.7 from 2002 to 2006 are employed as the data sets. The performance of the approach is estimated by calculating the norm mean square error and mean absolute percentage error. It is shown that our approach can perform well by using fewer training data points than the traditional neural network.

Investigation of the possible source for the solar energetic particle event on 2017 September 10

According to the solar proton data observed by Geostationary Operational Environmental Satellites （GOES）, ground-based neutron monitors on Earth and near-relativistic electron data measured by the ACE spacecraft, the onset times of protons with different energies and near-relativistic electrons have been estimated and compared with the time of solar soft and hard X-ray and radio burst data. The results show that first arriving relativistic and non-relativistic protons and electrons may have been accelerated by the concurrent flare. The results also suggest that release times of protons with different energies may be different, and the protons with lower energy may have been released earlier than those with higher energy. Some protons accelerated by concurrent flares may be further accelerated by the shock driven by the associated CME.

A study on the dynamic spectral indices for SEP events on 2000 July 14 and 2005 January 20

We have studied the dynamic proton spectra for the two solar energetic particle(SEP)events on2000 July 14(hereafter GLE59)and 2005 January 20(hereafter GLE69).The source locations of GLE59 and GLE69 are N22 W07 and N12 W58 respectively.Proton fluxes>30 Me V have been used to compute the dynamic spectral indices of the two SEP events.Our results show that spectral indices of the two SEP events increased more swiftly at early times,suggesting that the proton fluxes>30 Me V might be accelerated particularly by the concurrent flares at early times for the two SEP events.For the GLE69 with source location at N12 W58,both flare site and shock nose are well connected with the Earth at the earliest time.However,only the particles accelerated by the shock driven by eastern flank of the CME can propagate along the interplanetary magnetic field line to the Earth after the flare.For the GLE59 with source location at N22 W07,only the particles accelerated by the shock driven by western flank of the associated CME can reach the Earth after the flare.Our results also show that there was slightly more than one hour during which the proton spectra for GLE69 are softer than that for GLE59 after the flares,suggesting that the shock driven by eastern flank of the CME associated with GLE69 is weaker than the shock driven by the western flank of the CME associated with GLE59.The results support that quasi-perpendicular shock has stronger potential in accelerating particles than the quasi-parallel shock.These results also suggest that only a small part of the shock driven by western flank of the CME associated with the GLE59 is quasi-perpendicular.

A New Post-hoc Flat Field Measurement Method for the Solar X-Ray and Extreme Ultraviolet Imager Onboard the FengYun-3E Satellite

Extreme ultraviolet(EUV)observations are widely used in solar activity research and space weather forecasting since they can observe both the solar eruptions and the source regions of the solar wind.Flat field processing is indispensable to remove the instrumental non-uniformity of a solar EUV imager in producing high-quality scientific data from original observed data.FengYun-3E(FY-3E)is a meteorological satellite operated in a Sunsynchronous orbit,and the routine EUV imaging data from the Solar X-ray and Extreme Ultraviolet Imager(X-EUVI)onboard FY-3E has the characteristic of concentric rotation.Taking advantage of the concentric rotation,we propose a post-hoc flat field measurement method for its EUV 195A channel in this paper.This method removes the small-scale and time-varying component of coronal activities by taking the median value for each pixel along the time axis of a concentric rotation data cube,and then derives the large-scale and invariable component of the quiet coronal radiation,and finally generates a flat field image.The flat field can be generated with cadences from hundreds of minutes(one orbit)to several days.Higher flat field accuracy can be achieved by employing more data.Further analysis shows that our method is able to measure the instrumental spot-like nonuniformity possibly caused by contamination on the detector,which mostly disappears after the in-orbit selfcleaning process.It can also measure the quasi-periodic grid-like non-uniformity,possibly from the obscuration of the support mesh on the rear filter.After flat field correction,these instrumental non-uniformities from the original data are effectively removed.Moreover,the X-EUVI 195A data after dark and flat field corrections are consistent with the 193A imaging data from the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory,verifying the suitability of the method.The post-hoc method does not occupy observation time,which is advantageous for space weather operations.Our method is not only suitable for FY-3E/X-EUVI but also a candidate method for the flat field measurement of future solar EUV telescopes.

The properties of solar active regions responsible for ground level enhancements during solar cycles 22 and 23

This is a study designed to analyze the relationship between ground level enhancements（GLEs）and their associated solar active regions during solar cycles 22and 23.Results show that 90.3%of the GLE events that are investigated are accompanied by X-class flares,and that 77.4%of the GLE events originate from super active regions.It is found that the intensity of a GLE event is strongly associated with the specific position of an active region where the GLE event occurs.As a consequence,the GLE events having a peak increase rate exceeding 50%occur in a longitudinal range from W20 to W100.Moreover,the largest GLE events occur in a heliographic longitude at roughly W60.Additionally,an analysis is made to understand the distributional pattern of the Carrington longitude of the active regions that have generated the GLE events.

A Review of Research on the Record-Breaking Precipitation Event in Henan Province,China,July 2021

A record-breaking precipitation event,with a maximum 24-h(1-h)precipitation of 624 mm(201.9 mm)observed at Zhengzhou Weather Station,occurred in Henan Province,China,in July 2021.However,all global operational forecast models failed to predict the intensity and location of maximum precipitation for this event.The unexpected heavy rainfall caused 398 deaths and 120.06 billion RMB of economic losses.The high-societal-impact of this event has drawn much attention from the research community.This article provides a research review of the event from the perspectives of observations,analysis,dynamics,predictability,and the connection with climate warming and urbanization.Global reanalysis data show that there was an anomalous large-scale circulation pattern that resulted in abundant moisture supply to the region of interest.Three mesoscale systems(a mesoscale low pressure system,a barrier jet,and downslope gravity current)were found by recent high-resolution model simulation and data assimilation studies to have contributed to the local intensification of the rainstorm.Furthermore,observational analysis has suggested that an abrupt increase in graupel through microphysical processes after the sequential merging of three convective cells contributed to the record-breaking precipitation.Although these findings have aided in our understanding of the extreme rainfall event,preliminary analysis indicated that the practical predictability of the extreme rainfall for this event was rather low.The contrary influences of climate warming and urbanization on precipitation extremes as revealed by two studies could add further challenges to the predictability.We conclude that data sharing and collaboration between meteorological and hydrological researchers will be crucial in future research on high-impact weather events.

Responses of the Sea Surface Temperature and Suspended Matter Concentration to ENSO Events in the Bohai Sea

The sea surface temperature(SST)and sea surface suspended matter concentration data in the Bohai Sea were collected by multiple NOAA satellites from 1985 to 2018.The background calibration method was used to correct the systematic errors caused by the long-term observations through multiple NOAA satellites in this paper.Then,we studied the long-term variations of the sea surface temperature(SST)and sea surface suspended matter concentration(SSC)and their response to ENSO events in the Bohai Sea.Our results show that the SST and SSC of the Bohai Sea have been increasing since 1985,with an average rate of 0.04℃per year for SST,which is higher than the global average.The average increasing rate of SSC was 0.51 mg L^(-1)yr^(-1),which may be mainly due to the enhancement of winter monsoon in the Bohai.In winter,the SST and SSC of the Bohai Sea were higher in El Niño years than in La Niña years.In El Niño years,the ocean circulations were the main factor affecting the variation in SST.The robust circulation system caused by the strong winter monsoon enhances the water exchange between the cold water of the Bohai Sea and the warm water of the Yellow Sea,resulting in a higher SST in La Niña years.In summer,the SSTs of the Bohai Sea were lower in El Niño years than those in the La Niña years because of the decrease of the SST in the Western Pacific Ocean,the weakening of the subtropical high in the western Pacific,and its eastward shift caused by the El Niño events.

Sawtooth and dune auroras simultaneously driven by waves around the plasmapause

The dune aurora,at a scale of~30 kilometers,was reported recently using ground camera.The small-scale dune aurora occurs on the duskside and exhibits a monochromatic oscillation in the auroral emission,implying fundamental energy conversions.However,whether the dune auroras correspond to atmospheric waves or are associated with magnetospheric dynamics should be determined.This paper reports a dune aurora that occurred during a storm;further,we demonstrate that it was the substructure of the sawtooth aurora that was generated by plasmapause surface waves.Conjugate observations in the magnetospheric source region suggest that the exohiss waves,which are periodically modulated by the plasmapause surface wave-excited ultralow frequency wave,might be responsible for the generation of the dune aurora.Most reported dune aurora events have occurred simultaneously with sawtooth auroras,suggesting that both are plasmapause-driven cross-scale auroral structures.

Cross-satellite calibration of high-energy electron fluxes measured by FengYun-4A based on Arase observations

We use the High-energy Electron Experiments(HEP)instrument onboard Arase(ERG)to conduct an energy-dependent cross-satellite calibration of electron fluxes measured by the High Energy Particle Detector(HEPD)onboard FengYun-4A(FY-4A)spanning from April 1,2017,to September 30,2019.By tracing the two-dimensional magnetic positions(L,magnetic local time[MLT])of FY-4A at each time,we compare the datasets of the conjugate electron fluxes over the range of 245–894 keV in 6 energy channels for the satellite pair within different sets of L×MLT.The variations in the electron fluxes observed by FY-4A generally agree with the Arase measurements,and the percentages of the ratios of electron flux conjunctions within a factor of 2 are larger than 50%.Compared with Arase,FY-4A systematically overestimates electron fluxes at all 6 energy channels,with the corresponding calibration factors ranging from 0.67 to 0.81.After the cross-satellite calibration,the electron flux conjunctions between FY-4A and Arase show better agreement,with much smaller normalized root mean square errors.Our results provide a valuable reference for the application of FY-4A high-energy electron datasets to in-depth investigations of the Earth’s radiation belt electron dynamics.

AC vector magnetometer for space-based applications using low-resource magneto-impedance sensor

This study proposes a novel AC vector magnetometer developed using a low-resource magneto-impedance sensor for China’s Feng-Yun meteorological satellite(FY-3E).It was calibrated and characterized to determine its performance parameters.The total weight of the AC vector magnetometer is 51 g(the aluminum box excluded),while the total power consumption is 310 m W.The proposed AC vector magnetometer can detect magnetic field variations in the range of±1000 nT and noise power spectral density of≤50 pT/Hz^(1/2)@1 Hz.Furthermore,the proposed device has a maximum nonlinearity of≤0.71‰over the entire range and a nonorthogonality error of 3.07 nT or 0.15%(root mean square).The total dose hardness of the sensor is≥30 krad(Si).Furthermore,we propose the first survey results of a magnetometer equipped aboard a Chinese FY-3E satellite in a Sunsynchronous orbit.The data revealed that the AC vector magnetometer can detect transient physical signals such as quasistatic field-aligned currents(~50 nT)and waves at the auroral latitudes.These features render the proposed AC vector magnetometer suitable for space-based applications,particularly those involving the study of geomagnetic activity.

Properties of the Main Phases of the Super Geomagnetic Storms(ΔSYM-H≤-250 nT)with Different Heliolongitudes

We studied the properties of the main phases of 24 super geomagnetic storms(SGSs)(ΔSYM-H≤-250 nT)since 1981.We divided the SGSs into two subgroups:SGSs-Ⅰ(-400 nT<ΔSYM-H≤-250 nT)and SGSs-Ⅱ(ΔSYM-H≤-400 nT).Of the 24 SGSs,16 are SGSs-Ⅰand eight are SGSs-Ⅱ.The source locations of SGSs were distributed in the longitudinal scope of[E37,W66].95.8%of the SGSs were distributed in the longitudinal scope of[E37,W20].East and west hemispheres of the Sun had 14 and 10 SGSs,respectively.The durations of the main phases for six SGSs ranged from 2 to 4 hr.The durations of the main phases for the rest 18 SGSs were longer than 6.5 hr.The duration of the SGSs with source locations in the west hemisphere varied from 2.22 to 19.58 hr.The duration for the SGSs with the source locations in the east hemisphere ranged from 2.1 to31.88 hr.The averaged duration of the main phases of the SGSs in the west and east hemispheres are 8.3 hr and13.98 hr,respectively.|ΔSYM-H/Δt|for six SGSs with source locations distributed in the longitudinal area ranging from E15 to W20 was larger than 1.0 nT·minute^(-1),while|ΔSYM-H/Δt|for the rest 18 SGSs was lower than 1.0 nT·minute^(-1).|ΔSYM-H/Δt|for SGSs-Ⅰvaried from 0.18 to 3.0 nT·minute^(-1).|ΔSYM-H/Δt|for eight SGSs-Ⅱvaried from 0.37 to 2.2 nT·minute^(-1)with seven SGSs-Ⅱfalling in the scope from 0.37 to0.992 nT·minute^(-1).

Fengyun Satellites:Achievements and Future

Chinese meteorological satellite,Fengyun(FY) Satellite,has a polar-orbiting series and a geostationary series.Up to now,5 polar-orbiting(FY-1A/B/C/D and FY-3A) and 5 geostationary(FY-2A/B/C/D/E) satellites were launched.FY data has been being intensively applied not only to meteorological monitoring and prediction but also to many other fields regarding ecology,environment,disaster,space weather and so and.The FY data sharing system,FengyunCast,is now one of the three components of global meteorological satellite information dissemination system,GEONETCast.The first satellite of the new generation polar-orbiting series,FY-3A,was launched on 27 May,2008,demonstrating the FY polar-orbiting satellite and its application completed a great leap to realize threedimensional observations and quantitative application.The first of the next generation geostationary series(FY-4) is planned to launch in 2014.