Abstract:This study uses the monthly sea surface temperature(SST)data from the ERSSTv5 dataset,along with the 10-m wind,sea-level pressure(SLP),latent heat flux,2-m air temperature and 2-m dew point data from the ERA5 reanalysis from 1955 to 2024.The Pacific meridional mode(PMM)is defined via the maximum covariance analysis.Using a combination of statistical methods including the decomposition of wind-evaporation-SST(WES)feedback and regression analysis,we investigate the long-term trends of PMM and explore the potential mechanisms driving its variations from the perspectives of atmospheric variability and subtropical feedback.The results reveal a significant enhancement of PMM since 1990,with a strengthening trend also evident during spring.The enhancement of PMM is attributed to the synergistic effects of mid-to-high-latitude atmospheric variability and subtropical feedback.On the one hand,the North Pacific Oscillation(NPO)exhibits a strengthened driving effect on PMM,where the winter SLP anomalies enhance the sensitivity of subtropical North Pacific SST to atmospheric forcing by modulating latent heat flux and surface wind fields.Notably,the NPO-related spring SST anomalies in the subtropical North Pacific show a high correlation with spring PMM intensity over the study period.On the other hand,the WES feedback intensity in the subtropical North Pacific has significantly strengthened since 1990,further amplifying the PMM-associated SST anomalies.This strengthening primarily stems from the combined effects of sustained background SST warming and reduced relative humidity in the subtropical North Pacific.

Abstract:Based on the meteorological data,maize growth period and yield data of the main maize producing areas in Heilongjiang from 1981 to 2021,extreme wind speed and relative soil moisture are selected and their corresponding critical values suitable for maize harvest are constructed in different parts of the main maize producing areas in Heilongjiang by using the confidence interval estimation method.At the same time,this paper explores and analyzes the impact of precipitation and autumn temperature after the maize matures.The results are as follows.(1)The critical value of suitable daily extreme wind speed W0 is between 8.3 and 13.5 m·s-1,the suitable relative soil moisture M0 between 71％and 94％at different stations in the study area,and the daily extreme wind speed equal to or smaller than W0 and the relative soil moisture equal to or smaller than M0 are suitable for maize harvest.The established indicators can better indicate the suitability of extreme wind speed and soil moisture for maize harvest in Heilongjiang.(2)During the main harvest period between the maturity of maize and 20 October,it is suitable for maize harvest in rainy weather with daily precipitation below 23.0 mm.(3)There is a significant correlation(P＜0.01 or P＜0.05)between the autumn a verage/maximum/minimum temperature and the grain weight of maize per plant,respectively.Within a certain temperature range,the grain weight of maize per plant shows an increasing trend as the autumn temperature rises,which indicates that higher autumn temperature has a positive effect on the maturity of maize.

Abstract:Based on wind lidar observation data from Beijing Daxing International Airport from 2021 to 2022,a systematic analysis is conducted on the spatiotemporal distribution characteristics of low-level wind shear alerts.Furthermore,the relationship between wind shear alerts and weather conditions is examined using 133 alert events in 2022.The results are as follows.(1)There are significant seasonal and diurnal variations in wind shear alerts,with a peak period from April to June and a notably higher alert frequency during nighttime compared to daytime.(2)Weather pattern classifications reveal that wind shear events associated with thunderstorms and strong winds account for approximately one-third of the total alerts,and only 9％of the alerts are triggered by temperature inversion breakdowns.(3)Under stable synoptic conditions,the wind shear alerts caused by vertical wind speed differences tend to last longer.(4)Case studies confirm that the wind lidar system can effectively detect abrupt changes in wind direction and speed caused by cold air intrusions,achieving a wind shear alert hit rate of up to 74％during strong wind events.These findings provide technical support for diagnosing the causes of wind shear,optimizing alert thresholds and improving multi-source data fusion.

Abstract:The characteristics of the atmospheric circulation in spring 2025(from March to May)were as follows.The polar vortex in the Northern Hemisphere exhibited a dipolar distribution with two main closed centers,which was stronger than the climatological mean.The westerly wind belt in the mid-high latitudes displayed a 4-wave pattern,with the Eurasian continent showing a"two troughs and one ridge"circulation pattern.From March to May,the subtropical high was positioned southward and was stronger than normal,which was unfavorable for tropical cyclone formation.Compared to normal years,there were more strong winds at sea,while sea fog processes were less frequent.There were 9 distinct gale events(Beaufort wind force scale 8 or higher),among which 8 were generated by maritime temperate cyclones and one was generated by cold air.There were 7 significant sea fog processes,with three occurring in March,two in April and two in May,and the duration of sea fog processes generally ranged between 2 and 4 d.There were a total of 9 significant wave events(significant wave height ≥2.0 m)along the coast of China,and March,April May each had three occurrences.High wave days accounted for 57％of the season's total days.The sea surface temperature(SST)generally showed a gradual warming trend,and the coastal SST along China was generally above the climatological mean,especially in the southern East China Sea and the Bohai Sea.

Abstract:Based on the hourly precipitation data from 6 national surface meteorological observing stations and 122 regional meteorological observing stations in Jiangmen from 2010 to 2021,the spatial and temporal distribution characteristics of precipitation events with different durations during the flood season in Jiangmen are analyzed.The results are as follows.(1)The annual average precipitation in Jiangmen is higher in the south than in the north,with a stronger annual average precipitation intensity in the south.The annual average precipitation hours are high in the west.The distribution of monthly average precipitation exhibits a double peak pattern,with the highest precipitation occurring in August,the second peak in May,and the least precipitation in December.(2)Short-duration precipitation events are the most frequent during the flood season,while long-duration events contribute the most to the total precipitation.(3)During the early flood season,the short-and medium-duration precipitation predominantly affects the northern region,whereas the long-duration precipitation primarily affects the southwestern and coastal areas.During the latter flood season,there is little variation in the frequency of long-duration precipitation,but the contribution of precipitation from the southern region is greater.(4)Spatially,nearly 40％of the stations record peak daily average precipitation from morning to noon both in the early and latter flood seasons.During the early flood season,the northwestern region exhibits stronger convection from afternoon to evening,while the southeastern region experiences more intense convection during the latter part of the night,and the average precipitation intensity is large from morning to nightfall.In the latter flood season,the nocturnal precipitation becomes more pronounced than in the early season,with strong average precipitation intensity from midnight to morning.

Abstract:During the summer of 2025(June-August),the Northern Hemisphere polar vortex exhibited a unipolar distribution pattern,with its main body located within the Arctic Circle and the center shifted toward the Eastern Hemisphere.The mid-to-high latitude circulation displayed a 4-wave pattern configuration,while the Eurasian continent experienced a"two troughs and one ridge"circulation pattern.From June to July,the western Pacific subtropical high was stronger than the climatological average and positioned further westward and southward than normal.A total of 14 tropical cyclones formed in western North Pacific and the South China Sea,representing an increase of 3 systems above the long-term average.Five of these tropical cyclones made landfall along China's coastlines,among which Typhoon Danas followed a historically rare track,making initial landfall on the western coast of Taiwan Island before recurving westward to make a second landfall in Zhejiang.Additionally,19 tropical cyclones developed in other tropical oceans.China's offshore waters experienced 6 occurrences of gale-force wind events(Beaufort wind scale 8 or above),all induced by typhoon activities.Eleven significant wave events with wave height exceeding 2.0 m were recorded in offshore waters,and the most extreme wave event of the season occurred from 11 to 14 August,influenced by Typhoon Podul,with the maximum wave height reaching 9.0 m.Five notable sea fog events were observed in China's northern sea areas,with 4 occurring in June and one in July.The sea surface temperature(SST)across China's offshore waters was generally on the rise,with a significant warming trend in the northern sea areas.In August,the SST anomalies were 2-3 ℃ higher than the climatological mean in the same period.

Abstract:Based on data from the China Meteorological Administration's Yearbook of Tropical Cyclones,this study analyzes the spatiotemporal characteristics of typhoon-induced precipitation in the Yellow Sea and Bohai Sea region(30°-50°N,110°-130°E)during 1961-2020.The results show the following.(1)Spatial distribution.The 60-year averages of typhoon precipitation(TP),the number of typhoon precipitation days,the number of typhoon rainstorm days,the number of precipitation-producing typhoons,and contribution rate of typhoon to total precipitation all exhibit a maximum center along the northern coast of Zhejiang,decreasing towards the northern and inland areas.In contrast,the spatial differences in typhoon rainfall intensity and extreme daily precipitation between the southern and northern areas are relatively smaller.Specifically,the three northeastern provinces of China and the circum-Bohai areas show higher values of typhoon single-day precipitation intensity(T-SDPI),event-mean TP,and typhoon contributions to top 1％historical extreme daily precipitation.(2)Interannual distribution.Over the 60 years,the number of precipitation-producing typhoons affecting the Yellow Sea and Bohai Sea region increases significantly,while the annual TP displays a decreasing-increasing trend.Notably,during 2012-2020,the regional mean TP in the Yellow Sea and Bohai Sea region and annual mean TP in Jilin,Jiangsu,Anhui,Hubei,and northern Zhejiang are significantly higher than those during 1961-2011.(3)Seasonal distribution.The TP in the Yellow Sea and Bohai Sea region is predominantly concentrated between June and October,peaking in August,followed by September and July.From 2012 to 2020,with the significant increase in annual mean TP,the spring TP disappears in the Yellow Sea and Bohai Sea region,while the feature of early autumn(September-October)TP stronger than early summer(June-July)TP becomes more pronounced.It suggests an overall tendency for TP in the Yellow Sea and Bohai Sea region to shift toward autumn within the annual cycle.

Abstract:In the late spring and early summer of 2021,many areas in China experienced severe convections,causing heavy casualties and property losses,especially in southern China(25.0°～32.5°N,112.5°～122.5°E)from 10 to 16 May.Through analyzing the features of the atmospheric circulation anomalies from 10 to 16 May 2021,as well as the associated dynamical,thermal and moisture conditions,the study explores the causes of frequent severe convections in southern China from the perspective of large-scale environment.The results show that the frequent severe convections are closely related to large-scale circulation anomalies.At 500 hPa over Eurasia,the geopotential height anomalies exhibit a northwest-southeast oriented wave train pattern with a"+,-,+"distribution.Along this wave train,the Ural Mountains and the coastal areas of East Asia are dominated by positive height anomalies,while the areas from Lake Baikal to Balkhash Lake are occupied by negative height anomalies.The positive anomalies along the coastal areas of East Asia correspond to an intensified and northward shifted western Pacific subtropical high(shorted as WPSH).On the one hand,the anomalous southwest warm and moist airflow to the north of WPSH is beneficial to the development of ascending motion as well as the establishment of unstable stratification in southern China.On the other hand,the pressure decrease resulting from the anomalous warm advection is favorable for the frequent occurrence of low-level convergence systems in southern China,which provides triggering conditions for severe convections.In addition,the strong vertical wind shear formed between high-and low-level jets is also one of the favorable dynamic conditions for the development of severe convections.Further analysis indicates that there is a southeastward propagating anomalous wave activity flux,which originates from the high latitudes of Eurasia,suggesting that the wave train-like circulation anomaly is closely associated with the dispersion of the Rossby wave energy.Therefore,the atmospheric dynamical process in mid-high latitudes plays an important role in the frequent severe convections in southern China.

Abstract:Based on the retrieval data of sea ice concentration from the U.S.National Snow and Ice Data Center and ERA-Interim data from 1979 to 2020,this paper makes use of the ensemble empirical mode decomposition method to analyze the variations of the sea ice and atmospheric wind/pressure field during this period.The results are shown below.(1)The sea ice coverage area has shown a decreasing trend in the past 40 years,and the decreasing rate is about 1.4×103 km2/(10 a).Among them,the decreasing trend of the sea ice concentration in the Barents Sea and Kara Sea is the most significant.At the same time,the sea ice coverage area reaches a minimum in September(summer)and a maximum in March(winter).(2)The polar sea-level pressure field shows a decreasing trend in the center of the Arctic and an increasing trend outside the Arctic from 1979 to 2014,and its spatial distribution characteristics are similar to those of the positive phase of the Arctic Oscillation.At the same time,the surface wind blowing from the Atlantic Ocean to the Barents Sea has an increasing trend from 1979 to 2014.Considering the dragging effect of the surface wind field on the surface current and sea ice,it is speculated that the warm water from the Atlantic Ocean will increase in the Barents Sea,which may cause the sea ice to melt in the area.

Abstract:Using the North American Multi-Model Ensemble(NMME)hindcasts and ERSST observations,we investigate how the El Niño-Southern Oscillation(ENSO)prediction skill changes with the NMME model update and its possible causes.The NMME is divided into 4 phases of model update,approximately representing the operational model suites of 2011-2012,2012-2014,2014-2019 and 2019-present.ENSO prediction skills are analyzed in the hindcast for the period of 1982-2010.Results show that ENSO prediction skill does not change much in short-term prediction but improves significantly in long-term prediction with the model update.The possible reasons for the improvement are the improvement of ENSO spring prediction barrier and the improvement of NMME's prediction skill for Atlantic Niño/Niña.

Abstract:Based on the precipitation phenomenon instrument data,combined with the Doppler weather radar data and ERA5 data(0.25° × 0.25°),the synoptic systems,radar echoes and raindrop size distribution characteristics of the severe rainstorm in Yinan,Shandong from 13 to 14 August 2020 are analyzed.The main conclusions are as follows.(1)The precipitation in Yinan includes a relatively complex evolution process of mesoscale echoes.The earlier precipitation,referred to as the squall line precipitation,is generated by the linear convection and discontinuous convection echoes at the tail of the squall line under the influence of cold air and a low-level shear line,and the echoes strongly develop.Generated by the continuously developed and strengthened mesoscale convective cloud cluster,the later heavy precipitation,referred to as convective cloud cluster precipitation,is a kind of precipitation within the warm sector of the southwest low-level jet at the edge of the subtropical high,and the echo intensity is weaker with longer duration of precipitation.(2)The squall line precipitation is highly localized with a great fluctuation of rainfall intensity,and there are obvious changes in the parameters of lg Nw,Dm and NT.In contrast,the convective cloud cluster precipitation is relatively stable with slight changes in the parameters of raindrop size distribution,resulting in a more concentrated distribution of lg Nw-Dm.Both types of precipitation exhibit the raindrop size distribution characteristics of continental convective precipitation.(3)During the squall line precipitation,the coalescence and collision-breakup processes are more likely to reach equilibrium,and the proportion of equilibrium raindrop size distribution is high.During the convective cloud cluster precipitation,the proportion of transitional raindrop size distribution is high,indicating that the crushing of raindrops has a significant impact on the ground raindrop size distribution,which obviously alters the raindrop size distribution.Overall,there are certain but not significant differences in the microphysical characteristics of heavy precipitation in cold and warm sectors.

Abstract:The Beibu Gulf is an important hub region for China's new international trade route facing ASEAN,while the significant lack of research on the visibility parameterization in this area has hindered the safety assurance of maritime navigation.By utilizing the observational data on the microphysical characteristics of fog droplets from February to April in 2021 and 2023 across 4 regions of the Beibu Gulf,as well as routine meteorological data from port and island meteorological stations in January,February,March and December from 2016 to 2022,visibility parameterization models based on microphysical factors and meteorological elements are constructed,and their application effects are explored.The results are as follows.(1)The number concentration and liquid water content of fog droplets in the 4 regions of the Beibu Gulf are generally low,with average values of 20-42 particles/cm3 and approximately 0.01 g/m3,respectively.(2)The parameterization model constructed using the number concentration of fog droplets provides the best estimation of visibility in the Beibu Gulf,with correlation coefficients ranging from 0.51 to 0.76.(3)Key meteorological factors,when selected,are effective in distinguishing foggy days from non-foggy days,with relative humidity showing the best discrimination for foggy days across all the 4 regions.Other factors fully consider the thermal and dynamic conditions for the sea fog formation.(4)The visibility assessment model based on BP neural networks shows good consistency across the 4 regions,with correlation coefficients exceeding 0.8 between the estimated and observed visibility values during the training period,and the model in its forecast period successfully captures the peak and valley periods of the visibility evolution.Whether it is a visibility parameterization physical model or statistical model,the application effect is the best when it is constructed regionally for different regions of the Beibu Gulf.

Abstract:In order to reveal the environmental and radar parameter characteristics of supercell storm with hails of 7 cm or above,the environmental physical parameters,storm parameter evolution and polarization parameters of the supercell storm with giant hails in Tengzhou are analyzed using the S-band dual-polarization radar data in Jining,combined with sounding and ground observations.The results are outlined below.(1)The severe hailstorm in Tengzhou occurs under environmental conditions of strong convective available potential energy and moderate vertical wind shear in the deep layer,with relatively large temperature difference(Δt)between 850 hPa and 500 hPa,drier middle and upper troposphere,warmer and wetter lower troposphere.(2)The supercell storm in Tengzhou producing hails of 7 cm or above has a lower average maximum reflectivity(64.82 dBZ)due to the low concentration of larger hails,but higher C-VIL(average of 82 kg·m-2),depth of ZDR column(average of 2 km)and maximum rotational velocity of mesocyclone(average of 25.2 m·s-1),which means that there are strong updrafts supporting larger hails.(3)The top height of the ZDR column continues to increase and the C-VIL remains above 80 kg·m-2,which has indicative significance for the occurrence and early warning of severe hails.The continuous increase of the top height of the ZDR column indicates the intensification of the updrafts within the storm,and the storm would further develop.The C-VIL remains at high values,showing that the storm has abundant hail particles and the probability of giant hails is higher.(4)During the vigorous development stage of the storm,the strong echo(exceeding 60 dBZ)depth is close to 8 km and the top reaches about 10 km,indicating that large hails have been generated in the upper layer,and at the same time,hails fall to the lower layer,which reveals the mechanism of sustained development of hail clouds and continuous hails on the ground.

Abstract:Focusing on the Bohai Rim region,the study carries out an applicability evaluation for the mean wind products of the High Resolution China Meteorological Administration Land Data Assimilation System(HRCLDAS)and the 1-km-resolution products of the multi-source fused extreme wind real-time analysis(Analysis of Real Time,ART_1km)from 2022 to 2023.The evaluation is based on the hourly wind observation data from 1 324 meteorological stations,including surface automatic stations,buoy stations and offshore platforms.The results are shown below.The monthly mean absolute error of the HRCLDAS wind products is around 0.4 m·s-1.The errors of offshore stations are relatively large,and the phenomenon of wind speed underestimation is more obvious,while the data quality in 2023 significantly improves.During the same period,the accuracy rate of the mean wind direction is between 75％and 90％,and the situation when the accuracy rate of some stations is lower than 60％during light winds is related to the terrain.In terms of extreme wind,when the wind is Beaufort wind force scale 6 or above,the stronger the wind observed at stations,the greater the degree to which ART_1km underestimates.For winds of Beaufort wind force scale 8-9,the daily mean absolute errors between the ART_1km values and wind speed observations at both non-independent and independent stations range from 2 to 4 m·s-1;for winds of Beaufort wind force scale 10-11,the errors reach 4.5-5.5 m·s-1 at non-independent stations.

Abstract:Using the typhoon forecasts from National Meteorological Center,the observation data of China's automatic weather stations,ERA5 reanalysis data,main operational numerical models and ensemble forecasts,the evolution and track forecasting difficulties of Typhoon Gaemi(2403)during different stages are analyzed.The results are as follows.(1)Gaemi successively made landfall in Yilan,Taiwan and Putian,Fujian,bringing widespread and intense wind and rain impacts.The daily precipitation at 14 national meteorological observing stations broke historical records,demonstrating strong extremity.(2)During the formation stage of Gaemi when the atmospheric circulation is in a dynamic adjustment stage,it forms concurrently with Typhoon Prapiroon.The binary interaction between the two typhoon vortices further adds the difficulty of track forecasts.Although subjective forecasts have positive skill of corrections,significant deviations still exist in the typhoon track forecasts.(3)The complex terrain of Taiwan causes high uncertainty into the track forecasts of Typhoon Gaemi before and after it crosses the Taiwan Island,greatly increasing the challenge of accurate landing forecasts.However,high-resolution numerical models have certain advantages in forecasting small-scale fluctuations(such as track loops)in the track under complex terrain conditions.(4)After landing in Putian,Fujian,Gaemi suddenly turns to move westward in the northwest of Jiangxi,leading to significant deviations both in the track forecasts by numerical models and National Meteorological Center.This is because Gaemi is in a complex saddle-shaped environment,where its movement is extremely sensitive to minor changes in the surrounding circulation systems.(5)Nevertheless,AI models such as Fengqing demonstrate unique advantages in forecasting the westward turn of the track.In the future,forecasters should enhance the understanding and application of AI meteorological models.The factors influencing the typhoon track over land are complex,making the forecasting much more challenging than that over the sea.It is necessary to conduct in-depth research on the mechanisms of changes in the typhoon track over land to enhance the understanding of them.

Abstract:Using the WRF-CMAQ(Weather Research and Forecasting-Community Multiscale Air Quality)model and its adjoint(referred to as ADJOINT)model,a simulation is conducted for a 10-d continuous ozone(O3)pollution event in Hainan from 21 to 30 September 2019.The simulation aims to perform source apportionment for the O3 pollution event,quantifying the contributions of emission sources of different areas and species to the event.The results are outlined below.(1)During this pollution event,the mean value of mass concentration of MDA8-O3(maximum daily 8-h average-ozone)is 167μg·m-3,with the peak mass concentration of MDA8-O3 reaching 186.1 μg·m-3.(2)The WRF-CMAQ/ADJOINT model shows a good ability to simulate the variation of O3 mass concentration during this pollution event in Hainan.The ADJOINT model indicates that the long-distance regional transport is the main source of O3 pollution during this event,with an average contribution of 85％from external emissions and 15％from local emissions.The contribution of external emissions to Hainan is concentrated in the Pearl River Delta region.(3)Through analyzing the emission sources of VOCs(volatile organic compounds),it can be concluded that isoprene has the highest contribution among the sources,with an average contribution ratio of 51％.During the O3 pollution event,the pollution in Hainan is mainly controlled by NOx,and only in Haikou,the pollution is controlled both by VOCs and NOx.Given that the long-distance regional transport is the main source of the O3 pollution event,the future joint control in Hainan and the Pearl River Delta region is crucial for improving the air quality in Hainan.

Abstract:Different precipitation events are divided into short-duration,medium-duration,long-duration and persistent precipitation at 2-h intervals by minute precipitation data of 12 national meteorological stations in Tianjin during the warm season(from May to September)of 1979-2020.The spatial and temporal variation characteristics of precipitation,intensity and frequency of the precipitation events with different durations are analyzed.The results are shown below.(1)Temporally,the variations of precipitation,precipitation frequency and ratio are consistent,short-and medium-duration precipitation events show an increasing trend,and long-duration and persistent precipitation events show a decreasing trend.The precipitation intensity increases in each duration.(2)The time range of high precipitation and intensity of short-and medium-duration precipitation events has expanded from the traditional"late July-early August"to"mid-June-late August",while that of long-duration and persistent precipitation events has become more concentrated.(3)There are different spatial characteristics and trends in precipitation and intensity.The change in precipitation is mainly reflected in the increase of short-duration precipitation and the decrease of persistent precipitation,corresponding to the increase in precipitation intensity.This change is particularly significant in urban districts and their surrounding areas as well as in Binhai New area,which may be related to the changes in the urban thermal environment caused by urbanization.

Abstract:Based on the daily temperature observations from 1960 to 2023 in Shandong,this study analyzes the interannual distribution of the extreme values of annual and monthly highest and lowest temperatures,as well the characteristics of record-equalling/breaking highest and lowest temperatures since 2000.The results are shown below.(1)The interannual variation of the extreme values of the lowest temperatures since 1960 has shown a significant upward trend.The upward trend of the extreme values of the monthly lowest temperatures is greater than that of the monthly highest temperatures,the upward trend of the lowest temperatures in the first half of the year is greater than that in the second half,and the upward trend of the extreme values of the monthly highest temperatures during the transition of seasons is more significant.(2)The annual highest temperature records mostly occur after 2000,with the most in June.The annual lowest temperature records mostly occur in the 1960s and 1970s,with the most in January.The number and amplitude of record-equalling/breaking highest temperatures since 2000 are generally higher and larger than those of the lowest temperatures.(3)The frequency and warming amplitude of the monthly record-equalling/breaking highest temperature events are higher and larger than those of the lowest temperature events,and especially during the transition of seasons when warm and cold air masses are more active,the frequency of record-equalling/breaking highest temperature events is higher.In November,the frequency and amplitude of the record-equalling/breaking lowest and highest temperature events are higher and larger.

Abstract:The Baidu index(BI)of allergic rhinitis(AR),namely AR-BI,and the near surface observations of meteorological elements from 2021 to 2023 are used to evaluate the impact of changes in the meteorological elements on the incidence rate of AR in China.The results are as follows.(1)The analyses of changes in the meteorological elements and synoptic processes reveal a good correspondence between the rapid increase of AR-BI and early cold air activities during the shift season from autumn to winter.The rapid and significant decrease in the daily minimum relative humidity(RH),daily minimum specific humidity and daily minimum equivalent potential temperature during the cold air intrusion is synchronized with the rapid increase of the AR-BI from its background value.(2)During the first or early cold air activities each year,the air humidity decreases rapidly and significantly from the range that is more suitable for the human body in summer and autumn(RH higher than 40％),which may damage the nasal mucosa and could be the main cause of the high incidence of AR during the shift season from autumn to winter,resulting in the period with a high AR-BI from early August to mid-September each year.(3)The influence area of the cold air gradually expands from the north to the south over China during the shift season from autumn to winter,and the dry and cold air with lower humidity also gradually advances from the north to the south,resulting in the beginning and ending times of the AR-BI peak(i.e.the high incidence period of AR)gradually delayed from high latitudes to low latitudes.(4)The variability of the AR-BI is significantly higher in the north than in the south.Compared with the southern region,the cold air has a more significant impact on the northern region,resulting in lower specific humidity and a greater decrease of air humidity in the northern cities,which may lead to a higher incidence rate of AR in the north.

Abstract:The percentile and K-means clustering methods are utilized to analyze the longitude and latitude information of Fujian ocean buoy,trying to solve the problem of position estimation of missing observations under the conditions of position drift and swing in the long sequence of ocean buoy data.On this basis,with the third-party data such as CLDAS and ERA5,the inverse distance weighted method and the ordinary Kriging interpolation algorithm are used to calculate when the timing and longitude/latitude positions are determined,and the corresponding temperature,pressure,relative humidity,wind direction and wind speed are estimated.First,the evaluation results of different third-party information and different interpolation algorithms indicate that the stability of data sequence and its length have great impact on the filling of elements,and the inverse distance weighted method performs better than the ordinary Kriging interpolation.Subsequently,based on the conclusions,a new data set is reconstituted by integrating the original observation data from 7 Fujian ocean buoys.A comparative evaluation and validation of the two data sets show that the Pearson correlation coefficients of various meteorological elements are generally above 0.9.The new data set not only significantly improves its completeness but also preserves the consistency and robustness of the original observation data.Local abnormal element values are also effectively controlled.During the validation process of typhoon cases from 2014 to 2021,the wind speed elements are evaluated by comparing them with the real-time typhoon tracks.The correlation coefficients of the wind speed elements in the new data set averagely increase by 0.03,and the root mean square error averagely decreases by 0.5 m·s-1.The experiment shows that the data continuation technology can improve the operational applicability of ocean buoy observations.