In this paper, the authors develop the earlier work of Chen Jiabin et al. (1986). In order to reduce spectral truncation errors, the reference atmosphere has been introduced in ECMWF model, and the spectrally-represen...In this paper, the authors develop the earlier work of Chen Jiabin et al. (1986). In order to reduce spectral truncation errors, the reference atmosphere has been introduced in ECMWF model, and the spectrally-represented variables, temperature, geopotential height and orography, are replaced by their deviations from the reference atmosphere. Two modified semi- implicit schemes have been proposed to alleviate the computational instability due to the introduction of reference atmosphere. Concerning the deviation of surface geopotential height from reference atmosphere, an exact computational formulation has been used instead of the approximate one in the earlier work. To re duce aliasing errors in the computations of the deviation of the surface geopotential height, a spectral fit has been used slightly to modify the original Gaussian grid-point values of orography.A series of experiments has been performed in order to assess the impact of the reference atmosphere on ECMWF medium- range forecasts at the resolution T21, T42 and T63. The results we have obtained reveal that the reference atmosphere introduced in ECMWF spectral model is generally beneficial to the mean statistical scores of 1000-200 hPa height 10-day forecasts over the globe. In the Southern Hemisphere, it is a clear improvement for T21, T42 and T63 throughout the 10-day forecast period. In the Northern Hemisphere, the impact of the reference atmos phere on anomaly correlation is positive for resolution T21, a very slightly damaging at T42 and almost neutral at T63 in the range of day 1 to day 4. Beyond the day 4 there is a clear improvement at all resolutions.展开更多
China＇s FengYnn 3 （FY-3） polar orbiting satellites axe set to become an important sonrce of observational data for nu- merical weather prediction （NWP）, atmospheric reanalyses, and climate monitoring studies over...China＇s FengYnn 3 （FY-3） polar orbiting satellites axe set to become an important sonrce of observational data for nu- merical weather prediction （NWP）, atmospheric reanalyses, and climate monitoring studies over the next two decades. As part of the Climate Science for Service Partnership China （CSSP China） prograln, FY-3B Microwave Humidity Sounder 1 （MWHS-1） and FY-3C MWHS-2 observations have been thoroughly assessed and prepared for operational assimilation. This represents the first time observations from China＇s polar orbiting satellites have been used in the UK＇s global NWP model. Since 2016, continuous data quality monitoring has shown occasional bias changes found to be correlated to changes in the energy supply scheme regulating the platform heating system and other transient anomalies. Nonetheless, MWHS-1 and MWHS-2 significantly contribute to the 24-h forecast error reduction by 0.3% and 0.6%, respectively, and the combination of both instruments is shown to improve the fit to the model background of independent sounders by up to 1%. The observations from the Microwave Radiation Imager （MWRI） also are a potentially significant source of benefits for NWP models, but a solar-dependent bias observed in the instrument half-orbits has prevented their assimilation. This paper presents the bases of a correction scheme developed at the Met Office for the purpose of a future assimilation of MWRI data.展开更多
Features of structure and propagation of the 30 to SO day atmospheric oscillations are investigated using the ECMWF analysis of 1980-1983. Evidence is provided to confirm the characteristics of the oscillation in the ...Features of structure and propagation of the 30 to SO day atmospheric oscillations are investigated using the ECMWF analysis of 1980-1983. Evidence is provided to confirm the characteristics of the oscillation in the equatorial region. Those in the mid-high latitudes, however, are revealed to be very different from the tropics and pose a strong barotropic structure. Horizontal coherence shows teleconnection patterns which can be identified as EAP and PNA. The wind field of the specified time scale of the oscillation appears as long-lived vortices and vortex pairs. Mid-latitude perturbations propagate clearly westwards, especially during the winter season. In the high latitudes, they propagate westwards in the winter but eastwards in the summer. Meridional propagations are rather different from region to region.展开更多
In this paper, using the daily grid data (2.5 × 2.5) of the ECMWF / WMO, we have computed respectively the three-dimensional wave activity flux in the stages of pre-onset, prevailing and post ending of Meiyu from...In this paper, using the daily grid data (2.5 × 2.5) of the ECMWF / WMO, we have computed respectively the three-dimensional wave activity flux in the stages of pre-onset, prevailing and post ending of Meiyu from 1 to 31 July 1982. The potential vorticity field is taken as the physical quantity relating the wave activity flux to the variation of the subtropical high over the Western Pacific. It is found that the three-dimensional wave activity flux is a powerful means for diagnosis of the variation of the subtropical high over the Western Pacific: The region of the subtropical high is just the confluence area of wave energy, whose changes in intensity and range decide the variation of the subtropical high. The confluence of wave energy comes from the monsoon flow in low latitudes, the Meiyu rain belts in middle latitudes and the heating fields on the eastern side of the Qinghai-Xizang Plateau. The relation between these sources and the subtropical high displays the self-adjusting mechanism among members of East-Asia summer monsoon.展开更多
The features of water vapor transport, such as temporal evolution, vertical structure and spatial pattern, over North China during the prolonged drought in the summer of 1980 have been analyzed through computation of ...The features of water vapor transport, such as temporal evolution, vertical structure and spatial pattern, over North China during the prolonged drought in the summer of 1980 have been analyzed through computation of water vapor flux based on the once daily ECMWF grid-point data at 12GMT. The results indicate that it is unlikely that the characteristics of the atmospheric mass divergence, ascending motion and stratification stability in North China were completely opposite to those in the Yangtze River Valley, where the heavy flood occurred in the summer of 1980. It is major differences that the strong ascending motion and significant water vapor convergence overlap fairly well each other in the vertical levels in the Yangtze River Valley, while the maximum ascending motion is accompanied by water vapor divergence or weak water vapor convergence in North China. This vertical structure in North China results in insufficient water vapor supply and, therefore, little condensation and precipitation in the middle and upper atmosphere were produced. Additionally, a mode of monthly-scale low frequency oscillation can be found in water vapor flux, which is in correspondence to the fluctuation period of rainfall.展开更多
Cloud-based services introduce a paradigm shift in how users access,process and analyse Big Earth data.A key challenge is to align the current state of how users access,process and analyse the data with trends and roa...Cloud-based services introduce a paradigm shift in how users access,process and analyse Big Earth data.A key challenge is to align the current state of how users access,process and analyse the data with trends and roadmaps large data organisations layout.In addition,due to the increased availability of open data,a more diverse user base wants to take advantage of Earth science data leading to new user requirements.We run a web-based survey among Big Earth data users to better understand the motivation to migrate to cloud-based services as well as the challenges and opportunities that might arise.Results show an overall interest in moving to cloud-based services but air an insufficient literacy in cloud systems and a lack of trust due to security concerns and opacity of emerging costs.These gaps demand efforts on three levels.First,cloud services shall be targeted at intermediate users instead of policy-and decision-makers and over-engineered systems with a high level of abstraction should be avoided.Second,more substantial capacity-building efforts are required to decrease the existing gap in cloud skills and uptake.Third,a cloud certification mechanism could help in building up overall trust in cloud-based services.展开更多
This review summarizes the rapporteur report on tropical cyclone(TC)intensity change from the operational perspective,as presented to the 10th International Workshop on TCs(IWTC-10)held in Bali,Indonesia,from Dec.5–9...This review summarizes the rapporteur report on tropical cyclone(TC)intensity change from the operational perspective,as presented to the 10th International Workshop on TCs(IWTC-10)held in Bali,Indonesia,from Dec.5–9,2022.The accuracy of TC intensity forecasts issued by operational forecast centers depends on three aspects:real-time observations,TC dynamical model forecast guidance,and techniques and methods used by forecasters.The rapporteur report covers the progress made over the past four years(2018–2021)in all three aspects.This review focuses on the progress of dynamical model forecast guidance.The companion paper(Part II)summarizes the advance from operational centers.The dynamical model forecast guidance continues to be the main factor leading to the improvement of operational TC intensity forecasts.Here,we describe recent advances and developments of major operational regional dynamical TC models and their intensity forecast performance,including HWRF,HMON,COAMPS-TC,Met Office Regional Model,CMA-TYM,and newly developed HAFS.The performance of global dynamical models,including NOAA's GFS,Met Office Global Model(MOGM),JMA's GSM,and IFS(ECMWF),has also been improved in recent years due to their increased horizontal and vertical resolution as well as improved data assimilation systems.Recent challenging cases of rapid intensification are presented and discussed.展开更多
The quality control,validation and verification of the European Flood Alert System(EFAS)are described.EFAS is designed as a flood early warning system at pan-European scale,to complement national systems and provide f...The quality control,validation and verification of the European Flood Alert System(EFAS)are described.EFAS is designed as a flood early warning system at pan-European scale,to complement national systems and provide flood warnings more than 2 days before a flood.On average 2030 alerts per year are sent out to the EFAS partner network which consists of 24 National hydrological authorities responsible for transnational river basins.Quality control of the system includes the evaluation of the hits,misses and false alarms,showing that EFAS has more than 50%of the time hits.Furthermore,the skills of both the meteorological as well as the hydrological forecasts are evaluated,and are included here for a 10-year period.Next,end-user needs and feedback are systematically analysed.Suggested improvements,such as real-time river discharge updating,are currently implemented.展开更多
Seasonal tropical cyclone(TC)forecasting has evolved substantially since its commencement in the early 1980s.However,present operational seasonal TC forecasting services still do not meet the requirements of society a...Seasonal tropical cyclone(TC)forecasting has evolved substantially since its commencement in the early 1980s.However,present operational seasonal TC forecasting services still do not meet the requirements of society and stakeholders:current operational products are mainly basin-scale information,while more detailed sub-basin scale information such as potential risks of TC landfall is anticipated for decision making.To fill this gap and make the TC science and services move forward,this paper reviews recent research and development in seasonal tropical cyclone(TC)forecasting.In particular,this paper features new research topics on seasonal TC predictability in neutral conditions of El Ni˜no–Southern Oscillation(ENSO),emerging forecasting techniques of seasonal TC activity including Machine Learning/Artificial Intelligence,and multi-annual TC predictions.We also review the skill of forecast systems at predicting landfalling statistics for certain regions of the North Atlantic,Western North Pacific and South Indian oceans and discuss the gap that remains between current products and potential user's expectations.New knowledge and advanced forecasting techniques are expected to further enhance the capability of seasonal TC forecasting and lead to more actionable and fit-for-purpose products.展开更多
文摘In this paper, the authors develop the earlier work of Chen Jiabin et al. (1986). In order to reduce spectral truncation errors, the reference atmosphere has been introduced in ECMWF model, and the spectrally-represented variables, temperature, geopotential height and orography, are replaced by their deviations from the reference atmosphere. Two modified semi- implicit schemes have been proposed to alleviate the computational instability due to the introduction of reference atmosphere. Concerning the deviation of surface geopotential height from reference atmosphere, an exact computational formulation has been used instead of the approximate one in the earlier work. To re duce aliasing errors in the computations of the deviation of the surface geopotential height, a spectral fit has been used slightly to modify the original Gaussian grid-point values of orography.A series of experiments has been performed in order to assess the impact of the reference atmosphere on ECMWF medium- range forecasts at the resolution T21, T42 and T63. The results we have obtained reveal that the reference atmosphere introduced in ECMWF spectral model is generally beneficial to the mean statistical scores of 1000-200 hPa height 10-day forecasts over the globe. In the Southern Hemisphere, it is a clear improvement for T21, T42 and T63 throughout the 10-day forecast period. In the Northern Hemisphere, the impact of the reference atmos phere on anomaly correlation is positive for resolution T21, a very slightly damaging at T42 and almost neutral at T63 in the range of day 1 to day 4. Beyond the day 4 there is a clear improvement at all resolutions.
基金supported by the UK-China Research&Innovation Partnership Fund through the Met Office Climate Science for Service Partnership(CSSP)China as part of the Newton Fund
文摘China＇s FengYnn 3 （FY-3） polar orbiting satellites axe set to become an important sonrce of observational data for nu- merical weather prediction （NWP）, atmospheric reanalyses, and climate monitoring studies over the next two decades. As part of the Climate Science for Service Partnership China （CSSP China） prograln, FY-3B Microwave Humidity Sounder 1 （MWHS-1） and FY-3C MWHS-2 observations have been thoroughly assessed and prepared for operational assimilation. This represents the first time observations from China＇s polar orbiting satellites have been used in the UK＇s global NWP model. Since 2016, continuous data quality monitoring has shown occasional bias changes found to be correlated to changes in the energy supply scheme regulating the platform heating system and other transient anomalies. Nonetheless, MWHS-1 and MWHS-2 significantly contribute to the 24-h forecast error reduction by 0.3% and 0.6%, respectively, and the combination of both instruments is shown to improve the fit to the model background of independent sounders by up to 1%. The observations from the Microwave Radiation Imager （MWRI） also are a potentially significant source of benefits for NWP models, but a solar-dependent bias observed in the instrument half-orbits has prevented their assimilation. This paper presents the bases of a correction scheme developed at the Met Office for the purpose of a future assimilation of MWRI data.
文摘Features of structure and propagation of the 30 to SO day atmospheric oscillations are investigated using the ECMWF analysis of 1980-1983. Evidence is provided to confirm the characteristics of the oscillation in the equatorial region. Those in the mid-high latitudes, however, are revealed to be very different from the tropics and pose a strong barotropic structure. Horizontal coherence shows teleconnection patterns which can be identified as EAP and PNA. The wind field of the specified time scale of the oscillation appears as long-lived vortices and vortex pairs. Mid-latitude perturbations propagate clearly westwards, especially during the winter season. In the high latitudes, they propagate westwards in the winter but eastwards in the summer. Meridional propagations are rather different from region to region.
文摘In this paper, using the daily grid data (2.5 × 2.5) of the ECMWF / WMO, we have computed respectively the three-dimensional wave activity flux in the stages of pre-onset, prevailing and post ending of Meiyu from 1 to 31 July 1982. The potential vorticity field is taken as the physical quantity relating the wave activity flux to the variation of the subtropical high over the Western Pacific. It is found that the three-dimensional wave activity flux is a powerful means for diagnosis of the variation of the subtropical high over the Western Pacific: The region of the subtropical high is just the confluence area of wave energy, whose changes in intensity and range decide the variation of the subtropical high. The confluence of wave energy comes from the monsoon flow in low latitudes, the Meiyu rain belts in middle latitudes and the heating fields on the eastern side of the Qinghai-Xizang Plateau. The relation between these sources and the subtropical high displays the self-adjusting mechanism among members of East-Asia summer monsoon.
基金This research is sponsored by the National Natural Science Foundation of China.
文摘The features of water vapor transport, such as temporal evolution, vertical structure and spatial pattern, over North China during the prolonged drought in the summer of 1980 have been analyzed through computation of water vapor flux based on the once daily ECMWF grid-point data at 12GMT. The results indicate that it is unlikely that the characteristics of the atmospheric mass divergence, ascending motion and stratification stability in North China were completely opposite to those in the Yangtze River Valley, where the heavy flood occurred in the summer of 1980. It is major differences that the strong ascending motion and significant water vapor convergence overlap fairly well each other in the vertical levels in the Yangtze River Valley, while the maximum ascending motion is accompanied by water vapor divergence or weak water vapor convergence in North China. This vertical structure in North China results in insufficient water vapor supply and, therefore, little condensation and precipitation in the middle and upper atmosphere were produced. Additionally, a mode of monthly-scale low frequency oscillation can be found in water vapor flux, which is in correspondence to the fluctuation period of rainfall.
文摘Cloud-based services introduce a paradigm shift in how users access,process and analyse Big Earth data.A key challenge is to align the current state of how users access,process and analyse the data with trends and roadmaps large data organisations layout.In addition,due to the increased availability of open data,a more diverse user base wants to take advantage of Earth science data leading to new user requirements.We run a web-based survey among Big Earth data users to better understand the motivation to migrate to cloud-based services as well as the challenges and opportunities that might arise.Results show an overall interest in moving to cloud-based services but air an insufficient literacy in cloud systems and a lack of trust due to security concerns and opacity of emerging costs.These gaps demand efforts on three levels.First,cloud services shall be targeted at intermediate users instead of policy-and decision-makers and over-engineered systems with a high level of abstraction should be avoided.Second,more substantial capacity-building efforts are required to decrease the existing gap in cloud skills and uptake.Third,a cloud certification mechanism could help in building up overall trust in cloud-based services.
文摘This review summarizes the rapporteur report on tropical cyclone(TC)intensity change from the operational perspective,as presented to the 10th International Workshop on TCs(IWTC-10)held in Bali,Indonesia,from Dec.5–9,2022.The accuracy of TC intensity forecasts issued by operational forecast centers depends on three aspects:real-time observations,TC dynamical model forecast guidance,and techniques and methods used by forecasters.The rapporteur report covers the progress made over the past four years(2018–2021)in all three aspects.This review focuses on the progress of dynamical model forecast guidance.The companion paper(Part II)summarizes the advance from operational centers.The dynamical model forecast guidance continues to be the main factor leading to the improvement of operational TC intensity forecasts.Here,we describe recent advances and developments of major operational regional dynamical TC models and their intensity forecast performance,including HWRF,HMON,COAMPS-TC,Met Office Regional Model,CMA-TYM,and newly developed HAFS.The performance of global dynamical models,including NOAA's GFS,Met Office Global Model(MOGM),JMA's GSM,and IFS(ECMWF),has also been improved in recent years due to their increased horizontal and vertical resolution as well as improved data assimilation systems.Recent challenging cases of rapid intensification are presented and discussed.
文摘The quality control,validation and verification of the European Flood Alert System(EFAS)are described.EFAS is designed as a flood early warning system at pan-European scale,to complement national systems and provide flood warnings more than 2 days before a flood.On average 2030 alerts per year are sent out to the EFAS partner network which consists of 24 National hydrological authorities responsible for transnational river basins.Quality control of the system includes the evaluation of the hits,misses and false alarms,showing that EFAS has more than 50%of the time hits.Furthermore,the skills of both the meteorological as well as the hydrological forecasts are evaluated,and are included here for a 10-year period.Next,end-user needs and feedback are systematically analysed.Suggested improvements,such as real-time river discharge updating,are currently implemented.
基金support of the MEXT program for the advanced studies of climate change projection(SENTAN),Grant Numbers JPMXD0722680395 and JPMXD0722680734Julia Lockwood would like to acknowledge funding from the C3S_34c contract(number:ECMWF/COPERNICUS/2019/C3S_34c_DWD)of the Copernicus Climate Change Service operated by ECMWF.
文摘Seasonal tropical cyclone(TC)forecasting has evolved substantially since its commencement in the early 1980s.However,present operational seasonal TC forecasting services still do not meet the requirements of society and stakeholders:current operational products are mainly basin-scale information,while more detailed sub-basin scale information such as potential risks of TC landfall is anticipated for decision making.To fill this gap and make the TC science and services move forward,this paper reviews recent research and development in seasonal tropical cyclone(TC)forecasting.In particular,this paper features new research topics on seasonal TC predictability in neutral conditions of El Ni˜no–Southern Oscillation(ENSO),emerging forecasting techniques of seasonal TC activity including Machine Learning/Artificial Intelligence,and multi-annual TC predictions.We also review the skill of forecast systems at predicting landfalling statistics for certain regions of the North Atlantic,Western North Pacific and South Indian oceans and discuss the gap that remains between current products and potential user's expectations.New knowledge and advanced forecasting techniques are expected to further enhance the capability of seasonal TC forecasting and lead to more actionable and fit-for-purpose products.
