查看更多>>摘要：The effects of sea surface temperature(SST)changes induced by tropical cyclone(TC)Bilis(0604)and its preceding TC,TC Ewiniar(0603),on the intensity of TC Bilis were investigated by using numerical experiments.The observed SST changes induced by TCs Ewiniar(0603)and Bilis(0604)were first separated by using the smooth filtering and cylindrical filtering methods.The maximum SST cooling induced by TC Ewiniar(0603)exceeded 3℃,and that induced by the two TCs,Ewiniar(0603)and Bilis(0604),exceeded 6℃.The simulation results show that the SST cooling induced by TC Ewiniar(0603)and by two TCs reduced the intensity of TC Bilis(0604)by 6.2 m s-1 and 7.6 m s-1 within 60 h,respectively.Without the SST cooling induced by TC Ewiniar(0603),TC Bilis(0604)could have developed into a typhoon.The cold wake induced by TC Ewiniar(0603)was an important factor in inhibiting the intensity of TC Bilis(0604).Based on the analysis of the physical processes of the simulation results,a schematic diagram of the effects of SST changes induced by TCs on the intensity of TC Bilis(0604)was presented.The SST cooling reduced the upward heat flux and moisture flux at the surface of TC mainly within a radius of two latitudes,which in turn decreased the conditional instability and atmospheric moisture in the lower layer of TC,followed by weakening in TC precipitation,TC warm core,the upward vertical velocity of TC,and the inward radial wind in the lower layer of TC.The intensity of TC Bilis(0604)decreased accordingly.
查看更多>>摘要：In real-time operations,the minutely/hourly updated high-resolution rapid refresh(HRRR)system is one of the most expensive numerical weather prediction(NWP)models.Based on a twenty-member HRRR-time-lagged-ensemble(HRRR-TLE)system developed from two real-time convection-permitting HRRR models,CMA-GD(R3)and CMA-SH3,from the China Meteorological Administration(CMA),this study proposes an optimized probability-matching(OPM)technique to improve 0-12 h quantitative precipitation forecasts(QPFs)based on the correlation and error relationships between ensemble forecasts and observations during the training window.Then,a series of sensitivity experiments using different cost functions and optimized ratios was conducted to further improve OPM predictions.The results indicate that:(1)In the HRRR-TLE system,there is no always optimal member in both weak rain and severe rain forecasts,as measured by the equitable threat score(ETS)and bias extent(BE)at four thresholds(1+,5+,10+,and 20+mm h-1;e.g.,"1+"means≥ 1).(2)Compared with the HRRR-TLE system,the QPFs generated by the traditional PM technique showed a notable increase in ETS and a decrease in BE at all of the above thresholds.Compared with the traditional probability-matching method(PM),OPM can generate more skillful forecasts on both spatial representations and rain rates by using the sliding-weight method and optimized ensembles,respectively.(3)In particular,in the 20+mm h-1 forecasts,which are often difficult to predict,the ETS of the optimal OPM test,with a 20％optimization ratio and symmetric mean absolute percentage error cost function,increased by 64.6％,and the BE decreased by 5.7％,relative to PM.Moreover,OPM shows good stability in both daytime and nighttime periods.
查看更多>>摘要：Typhoons,characterized by their high destructive potential,significantly impact coastal residents'lives and property safety.To optimize numerical models'typhoon simulation,carefully selecting appropriate physical para-meterization schemes is crucial,offering robust support for disaster prevention and reduction efforts.This study focuses on Typhoon Mujigae,conducting a comparative analysis of different physical parameterization schemes(microphysics,cu-mulus parameterization,shortwave radiation,and longwave radiation)in WRF simulations.The key findings are as follows:cumulus and microphysics parameterization schemes notably influence the simulation of typhoon tracks and intensity,while the impact of longwave and shortwave radiation schemes is relatively minor.Typhoon intensity is more sensitive to the choice of parameterization schemes than track.Together,the Kain-Fritsch cumulus convection scheme,WRF Single Moment 5-class scheme,and Dudhia/RRTM radiation scheme yield the best intensity simulation results.Compared with the Betts-Miller-Janjic and Grell 3D scheme,the use of the Kain-Fritsch scheme results in a clearer,taller eyewall and more symmetric deep convection,enhancing precipitation and latent heat release,and consequently improving the simulated typhoon intensity.More complex microphysics schemes like Purdue Lin,WRF Single Moment 5-class,and WRF Double Moment 6-class perform better in simulations,while simpler schemes like Kessler and WSM3 exhibit significant deviations in typhoon simulations.Particularly,the large amount of supercooled water clouds simulated by the Kessler scheme is a major source of bias.Furthermore,a coupling effect exists between cumulus convection and mi-crophysics parameterization schemes,and only a reasonable combination of both can achieve optimal simulation results.
查看更多>>摘要：The Pearl River Estuary(PRE)is one of China's busiest shipping hubs and fishery production centers,as well as a region with abundant island tourism and wind energy resources,which calls for accurate short-term wind forecasts.First,this study evaluated three operational numerical models,i.e.,ECMWF-EC,NCEP-GFS,and CMA-GD,for their ability to predict short-term wind speed over the PRE against in-situ observations during 2018-2021.Overall,ECMWF-EC out-performs other models with an average RMSE of 2.24 m s-1 and R of 0.57,but the NCEP-GFS performs better in the case of strong winds.Then,various bias correction and multi-model ensemble(MME)methods are used to perform the deterministic post-processing using a local and lead-specific scheme.Two-factor model output statistics(MOS2)is the optimal bias correction method for reducing(increasing)the overall RMSE(R)to 1.62(0.70)m s-1,demonstrating the benefits of considering both initial and lead-specific information.Intercomparison of MME results reveals that Multiple linear regression(MLR)presents superior skills,followed by random forest(RF),but it is slightly inferior to MOS2,particularly for the first few forecasting hours.Furthermore,the incorporation of additional features in MLR reduces the overall RMSE to 1.53 m s-1 and increases R to 0.74.Similarly,RF presents comparable results,and both outperform MOS2 in terms of correcting their deficiencies at the first few lead hours and limiting the error growth rate.Despite the satisfactory skill of deterministic post-processing techniques,they are unable to achieve a balanced performance between mean and extreme statistics.This highlights the necessity for further development of probabilistic forecasts.
查看更多>>摘要：Based on rain gauge data during 2008-2021 from national meteorological observation stations,this study investigated the performance of the precipitation field from the 1-km-resolution version of the China Atmospheric Re-altime Analysis(CARAS)over Hubei from the perspective of climatology,multiple-time scale variations,as well as fusion accuracy and detection capability at multiple temporal scales.The results show that CARAS precipitation can reproduce the spatial distribution patterns of climatological seasonal precipitation and rainy days well over the whole of Hubei compared with observational(OBS)precipitation,albeit deviations exist between CARAS and OBS in terms of magnitude.Moreover,high correlation and consistency between CARAS and OBS can be found in multiple-time scale variations over Hubei,with correlation coefficients of interannual,seasonal,and diurnal variation generally exceeding 0.85,0.98,and 0.95,respectively.Furthermore,CARAS has a relatively higher fusion accuracy in summer and winter,and stronger/weaker detection capability in spring/winter at a daily scale.However,the detection capability of CARAS at an hourly scale is weaker than that at a daily scale.With different precipitation intensity levels considered,CARAS daily precipitation shows relatively higher fusion accuracy in estimating moderate and heavy rain,and better detection capability in capturing no rain events.The variations of accuracy metrics and detection metrics under different precipitation intensities at an hourly scale generally resemble those at a daily scale.However,CARAS precipitation at an hourly scale shows a relatively lower fusion accuracy and weaker detection capability compared with that at a daily scale.This paper provides an insight into the characteristics of systematic deviations in CARAS precipitation over Hubei,which will benefit relevant applications of CARAS in meteorological operations over Hubei and the improvement of CARAS in the future.
查看更多>>摘要：Based on the surface-gridded daily precipitation dataset and the simulation results from the Coupled Model Intercomparison Project Phase 6(CMIP6)models,this study investigates the variation of extreme precipitation probability over East China in spring and summer during the decaying year of East Pacific(EP)/Central Pacific(CP)El Nino events and explores possible influencing mechanisms.The results show that for the EP El Nino,in spring,the probability of extreme precipitation is much higher in the vast majority of East China.The anticyclonic water vapor transport in the Northwest Pacific and the higher temperature in East China jointly result in a large amount of water vapor converging and ascending in East China,which is conducive to extreme precipitation events in this region.In summer,the probability of extreme precipitation events decreases,but is still high in the Yangtze River Basin,corresponding to the weak and northerly anticyclone over the Northwest Pacific and the convergence and ascending of water vapor in the Yangtze River Basin.For the CP El Nino,the most obvious probability increase of extreme precipitation events appears over Northeast China and the Yangtze River Basin in spring.These regions are featured by positive geopotential height anomalies and strong northerly wind.Meanwhile,the temperature in Northeast China is slightly lower.In summer,the probability of extreme precipitation events in most areas significantly increases.The anomalous cold high-pressure center over the north of the South China Sea is notably strong,and the northwestern Pacific anticyclone expands to the west and the north.East China is mainly affected by the warm-wet southwesterly airflow,which is conducive to extreme precipitation events.The United States Geophysical Fluid Dynamics Laboratory model well represents the probability distribution of extreme precipitation events and the atmospheric circulation of the EP/CP El Nino.However,compared with observations,there are some biases,such as the higher probability of extreme precipitation in Central China in summer under the EP El Nino.
查看更多>>摘要：Based on previously released data,this paper first presented the criteria for recognizing bow echoes and divided their life cycle into three stages:the development stage,the mature stage,and the attenuation stage.Based on Doppler weather radar data during 2011-2020,43 bow echo events(including 54 individual bow echoes)in western South China were identified.The spatial and temporal distributions,formation and dissipation modes of these bow echoes,and the severe weather they caused were statistically analyzed.The results show that:(1)The bow echo events were unevenly distributed year-to-year,but all occurred from March to July,with the highest in April and May and the lowest in July.The period from night to early morning was found to be the main period for bow echo generation and intensification.(2)A banded area from Hechi City on the southeastern edge of the Yunnan-Guizhou Plateau to Wuzhou City in southeast Guangxi was identified as a high-incidence area of bow echoes.The length of bow echoes was correlated with their life cycle.(3)The origins of the bow echoes could be divided into five locations,most of which were in the eastern Yunnan-Guizhou Plateau.After entering western South China,their moving paths were categorized into three types,among which most bow echoes moved southeastward,generally because of the effect of cold air.Specifically,bow echoes generally moved eastward when cold air was weak or in the warm zone.Meanwhile,the fewest bow echoes moved northeastward.(4)Four modes of bow echo formation were identified:linearly organized,broken areal,linearly merging,and broken line.Dissipation could also be classified into four types.(5)The probability of convective weather generated by a bow echo was largest in the mature stage.
查看更多>>摘要：The occurrence of most major basin-wide floods is closely related to persistent heavy rainfall(PHR).In June 2022,a PHR event that lasted twenty days hit the Beijiang River Basin(BRB)in South China.The record-breaking rainfall led to major floods and caused tremendous losses.This study first reviews the spatiotemporal distribution of the pre-cipitation and the flooding process of this PHR event and then analyzes the atmospheric circulation patterns associated with the event based on the hourly reanalysis data from the European Centre for Medium-Range Weather Forecasts(ERA5).The results show that the establishment and stabilization of mid-to high-latitude blockings provided a favorable background for the"2022.06"PHR event in the BRB.The convergence of water vapor at the low level,the release of unstable energy,and the development of stronger vertical ascending movement provided the necessary dynamic conditions.The vertical circulation of water vapor was much stronger than that of climatology,while the vertical ascending movement was also more active in the BRB.The heavy rainfall belt in the BRB was formed in a region with apparently stronger divergence,which also coincided with regions of higher-than-normal updraft velocity and specific humidity.
查看更多>>摘要：To enhance urban resilience to climate change in the future,this study quantitatively assesses the climate carrying capacity of the Beibu Gulf Urban Agglomeration(BGUA)in the Guangxi Zhuang Autonomous Region from 2000 to 2020 and in a future projected study from 2021 to 2060.The data used includes real-time data from the National Meteorological Observatory,prediction data from the National Climate Center's global climate model BCC-CSM2-MR under different Shared Socioeconomic Pathways(SSP2-4.5 and SSP5-8.5),and socio-economic development data.The assessment is conducted using four criteria dimensions:climate natural capacity(CNC),extreme climate event pressure(ECP),urban climate pressure(UCP),and urban coordinated development capacity(UCC).The results indicate that from 2000 to 2020,there was a significant interannual fluctuation in the CNC and ECP in the BGUA.The UCP and the UCC showed an increasing trend,while the overall climate-carrying capacity of the BGUA showed a fluctuating decrease.It is estimated that the climate carrying capacity will exhibit a non-significant decreasing trend from 2021 to 2060,with the capacity in the period from 2021 to 2040 generally higher than that in the period from 2041 to 2060 and the SSP2-4.5 scenario higher than the SSP5-8.5 scenario overall.Currently and in the future,the climate-carrying capacity of the BGUA is primarily influenced by normal climate conditions and extreme events such as strong winds and temperature extremes.With the passage of time,climate instability will increase.Under the planned implementation of China's carbon peak and carbon neutrality pathway,the rate of increase in the capacity for coordinated urban development is expected to surpass the rate of increase in urban climate pressure.Industrial production and energy consumption are the main drivers of future urban climate pressure growth.
查看更多>>摘要：Using the daily precipitation data from the global precipitation measurement(GPM)satellite and meteorological stations from 2001 to 2020,the present study has analyzed the seasonal and interannual spatial-temporal variations of the precipitation over the Three-River Headwaters region.The rainfall of the Three-River Headwaters region is verified to have obvious spatial-temporal variations and is mainly concentrated in summer.Then,the empirical orthogonal function(EOF)method is performed and reveals that the summer precipitation in the Three-River Headwaters region mainly shows three patterns,e.g.,the"north-south dipole pattern,""northeast-southwest diploe pattern,"and"east-west dipole pattern,"among which the northeast-southwest diploe pattern has a strong correlation with the mid-latitude westerlies and summer monsoon.Further analysis reveals that the northeast-southwest diploe pattern of summer precipitation is significantly related to the tripolar sea surface temperature(SST)anomalies(SSTAs)of the North Atlantic Ocean in the preceding winter and the tropical Indian Ocean SSTAs in the simultaneous summer.In the preceding winter,a wave-like pattern zonally propagating along the mid-latitude westerlies is triggered downstream by the North Atlantic tripolar SSTAs.One of the cyclones generated by the wave-like pattern coincidentally locates in Northeastern China and forms a deep northeastern low system in summer.Moreover,the warming of the tropical Indian Ocean SSTAs in summer weakens the Walker circulation,which leads to the strengthening and westward extension of the Western Pacific subtropical high(WPSH).Northerly anomalies from the deep northeastern cyclonic anomalies and southwesterly anomalies from the enhancing WPSH exactly met at the eastern Three-River Headwaters region.Hence,more water vapor and ascending motion anomalies likely appear over the east part of the Three-River Headwaters region.Opposite anomalies cover the south-western Three-River Headwaters region and its surroundings.Then,the northeast-southwest reverse diploe pattern of the summer rainfall in the Three-River Headwaters region is directly produced.
万方数据
维普