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 ...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 precipitation 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.展开更多
Diurnal variations in amount, frequency and intensity of warm-season hourly precipitation(HP) at seven levels, which are defined as HP 0.1, 0.5, 1, 5, 10, 20 and 50 mm, are revealed based on no less than 30 years of h...Diurnal variations in amount, frequency and intensity of warm-season hourly precipitation(HP) at seven levels, which are defined as HP 0.1, 0.5, 1, 5, 10, 20 and 50 mm, are revealed based on no less than 30 years of hourly rain-gauge observations at national stations over central and eastern China(CEC). This study investigates the variations, relationships, differences and similarities of total, stratiform, convective and extreme HP over the entire CEC and various subregions. Results indicate that the variations in the amount and frequency of HP at the seven levels over the entire CEC all display a bimodal feature. For various regions, the variations of total HP mostly feature two peaks, while convective HP mainly occurs in the late afternoon and determines the diurnal variation of total HP intensity. On the basis of the primary peak time periods of HP frequency at all levels over different subregions, the variations can be classified into three main categories: late-afternoon primary peak, nocturnal primary peak, and time-shifting primary peak. However, the variations over some coastal regions like the Liaodong Peninsula, the Shandong Peninsula, and the coastal regions of Guangdong, distinctly differ from those over their corresponding larger regions. Overall, the normalized diurnal variation amplitude of amount and frequency increases with the increasing HP intensity; convective precipitation can be represented by HP 10 mm; and the intensity of HP 50 mm is slightly larger during the nighttime than during the daytime over the entire CEC. In northern China, diurnal variation in HP 5 mm can represent well that in convective precipitation.展开更多
Based on a daily precipitation observation dataset of 743 stations in China from 1951 2004, the F distribution function is used to calculate the probability distribution of daily precipitation and to define extreme pr...Based on a daily precipitation observation dataset of 743 stations in China from 1951 2004, the F distribution function is used to calculate the probability distribution of daily precipitation and to define extreme precipitation events. Based on this, the relationship of ENSO and the frequency of extreme precipitation events is studied. Results reveal that ENSO events have impact on extreme precipitation events, with different magnitudes at different regions and seasons. In general, during winter and spring, extreme precipitation events occur more often during E1 Nino events than during La Nina events. While during summer and autumn, the opposite is found. The relationship of a two season-lag ENSO and extreme precipitation frequency shows different pattern. Extreme precipitation events occur more often in several regions if an ENSO warm phase happened in the central-eastern tropical Pacific two seasons before. No similar impacts of El Nino and La Nina on the frequency of extreme precipitation events are found.展开更多
Plants play an important role in soil phosphorus nutrition. However, the effect of plants on phosphorus nutrition in soils of the Loess Plateau of China is not well understood. This study was conducted to reveal the r...Plants play an important role in soil phosphorus nutrition. However, the effect of plants on phosphorus nutrition in soils of the Loess Plateau of China is not well understood. This study was conducted to reveal the relationships between plants and phosphorus＇ fractions and availability in the Loess Plateau of China. Twenty-two plant communities were surveyed and soil samples under different plant canopies were collected for the determination of soil properties and inorganic phosphorus fractionation. The results showed that Leguminosae and Lilaceae reduced pH and increased organic matter, cation exchange capacity, total and Olsen phosphorus in soils under their canopies, while Labiatae and Rosaceae increased pH and decreased organic matter, cation exchange capacity, total and Olsen phosphorus in soils under their canopies. The contents of Ca2P, CasP, AI-P and Fe-P were highly related with soil Oisen phosphorus. They were all higher in soils under Leguminosae and Lilaceae and lower in softs under Labiatae and Rosaceae. The results of this study indicate that Leguminosae and Lilaceae improved phosphorus nutrition in soils, yet Labiatae and Rosaceae impeded the improvement of phosphorus nutrition in soils under their canopies, which will be of more help to instruct vegetation restoration in the region and provide information for soil development.展开更多
The operational cloud-motion tracking technique fails to retrieve atmospheric motion vectors （AMVs） in areas lacking cloud; and while water vapor shown in water vapor imagery can be used, the heights assigned to the...The operational cloud-motion tracking technique fails to retrieve atmospheric motion vectors （AMVs） in areas lacking cloud; and while water vapor shown in water vapor imagery can be used, the heights assigned to the retrieved AMVs are mostly in the upper troposphere. As the noise-equivalent temperature difference （NEdT） performance of FY-2E split win- dow （10.3-11.5 μm, 11.6-12.8 μm） channels has been improved, the weak signals representing the spatial texture of water vapor and aerosols in cloud-free areas can be strengthened with algorithms based on the difference principle, and applied in calculating AMVs in the lower troposphere. This paper is a preliminary summary for this purpose, in which the principles and algorithm schemes for the temporal difference, split window difference and second-order difference （SD） methods are introduced. Results from simulation and cases experiments are reported in order to verify and evaluate the methods, based on comparison among retrievals and the ＂truth＂. The results show that all three algorithms, though not perfect in some cases, generally work well. Moreover, the SD method appears to be the best in suppressing the surface temperature influence and clarifying the spatial texture of water vapor and aerosols. The accuracy with respect to NCEP 800 hPa reanalysis data was found to be acceptable, as compared with the accuracy of the cloud motion vectors.展开更多
The aim of this study is to calculate the low-level atmospheric motion vectors （AMVs） in clear areas with FY-2E IR2 window （11.59-12.79 μm） channel imagery,where the traditional cloud motion wind technique fails....The aim of this study is to calculate the low-level atmospheric motion vectors （AMVs） in clear areas with FY-2E IR2 window （11.59-12.79 μm） channel imagery,where the traditional cloud motion wind technique fails.A new tracer selection procedure,which we call the temporal difference technique,is demonstrated in this paper.This technique makes it possible to infer low-level wind by tracking features in the moisture pattern that appear as brightness temperature （TB） differences between consecutive sequences of 30-min-interval FY-2E IR2 images over cloud-free regions.The TB difference corresponding to a 10％ change in water vapor density is computed with the Moderate Resolution Atmospheric Transmission （MODTRAN4） radiative transfer model.The total contribution from each of the 10 layers is analyzed under four typical atmospheric conditions：tropical,midlatitude summer,U.S.standard,and midlatitude winter.The peak level of the water vapor weighting function for the four typical atmospheres is assigned as a specific height to the TB ＂wind＂.This technique is valid over cloudfree ocean areas.The proposed algorithm exhibits encouraging statistical results in terms of vector difference （VD）,speed bias （BIAS）,mean vector difference （MVD）,standard deviation （SD）,and root-mean-square error （RMSE）,when compared with the wind field of NCEP reanalysis data and rawinsonde observations.展开更多
[Objective] The aim was to study the change characteristics of temperature and heat resources in rural area of Chaoyang in western Liaoning. [Method] Based on the data from rural meteorological station in Chaoyang in ...[Objective] The aim was to study the change characteristics of temperature and heat resources in rural area of Chaoyang in western Liaoning. [Method] Based on the data from rural meteorological station in Chaoyang in western Liaoning from 1966 to 2010, the change characteristics of temperature and heat resources in rural area in Chaoyang were analyzed by means of serial correlation and climate tendency method, so as to master its climate situation. [Result] The annual average value of daily average temperature, daily maximum temperature and daily minimum temperature in rural area of Chaoyang in western Liaoning from 1966 to 2010 showed fluctuation variation, and the annual average value of daily maximum temperature increased most obviously with the climatic tendency of 0.328 ℃/10 a and highest significant level, so it played an important role in temperature increase, next came daily average temperature (0.151 ℃/10 a), while there was no obvious decrease in daily minimum temperature. The average of daily maximum temperature in winter half year increased more obviously than that in summer half year, with the climatic tendency of 0.417 and 0.250 ℃/10 a, respectively; the trend of daily average temperature reached low significant level, and there was no obvious variation in daily minimum temperature. In addition, ≥10 ℃ accumulated temperature in rural area of Chaoyang in western Liaoning went up obviously, with the climatic tendency of 42.59 ℃·d/10 a, namely it increased by 192 ℃·d in recent 45 years. [Conclusion] The study could provide climatic reference for the adjustment of agriculture structure and varieties distribution.展开更多
In the present paper, a comparison of the performance between moving cutting data-rescaled range analysis （MC- R/S） and moving cutting data-rescaled variance analysis （MC-V/S） is made. The results clearly indicate...In the present paper, a comparison of the performance between moving cutting data-rescaled range analysis （MC- R/S） and moving cutting data-rescaled variance analysis （MC-V/S） is made. The results clearly indicate that the operating efficiency of the MC-R/S algorithm is higher than that of the MC-V/S algorithm. In our numerical test, the computer time consumed by MC-V/S is approximately 25 times that by MC-R/S for an identical window size in artificial data. Except for the difference in operating efficiency, there are no significant differences in performance between MC-R/S and MC-V/S for the abrupt dynamic change detection. Mc-R/s and MC-V/S both display some degree of anti-noise ability. However, it is important to consider the influences of strong noise on the detection results of MC-R/S and MC-V/S in practical application展开更多
In this paper the differences between Meiyu and Baiu front in 1983 have firstly been analysed, the trajectories of air on and to the north side of Meiyu and Baiu fronts during the Meiyu period have then been traced, a...In this paper the differences between Meiyu and Baiu front in 1983 have firstly been analysed, the trajectories of air on and to the north side of Meiyu and Baiu fronts during the Meiyu period have then been traced, and the forecasting and simulating of 4 sets of Meiyu onset of the year have finally been run utilizing the global model at UK Me-leorological Office. The results show: 1) Meiyu fronts are different from Baiu ones in temperature, humidity and stratification fields in lower atmosphere; and the possibly reasons for it are explained. 2) The Bay of Bengal is the main moisture source for Meiyu front, the South China Sea and the Pacific, for Baiu ones; and some existed arguments on it are also discussed. 3) The onset of Meiyu and its rainfall and rain belts are sensitive to the Tibetan Plateau, and the water vapour conditions over the Bay of Bengal and the South China Sea, but not sensitive to the SST over the equatorial area or to the East of Japan.展开更多
To improve the level of meteorological service for the Oilfield region in the Taklimakan Desert, the Urumqi Institute of Desert Meteorology of the China Meteorological Administration （CMA） conducted a detection expe...To improve the level of meteorological service for the Oilfield region in the Taklimakan Desert, the Urumqi Institute of Desert Meteorology of the China Meteorological Administration （CMA） conducted a detection experiment by means of wind profiling radar （WPR） in Tazhong Oilfield region of Xinjiang, China in July 2010. By using the wind profiler data obtained during the rainfall process on 27 July, this paper analyzed the wind field fea- tures and some related scientific issues of this weather event. The results indicated that： （1） wind profiler data had high temporal resolution and vertical spatial resolution, and could be used to analyze detailed vertical structures of rainfall processes and the characteristics of meso-scale systems. Before and after the rain event on 27 July, the wind field showed multi-layer vertical structures, having an obvious meso-scale wind shear line and three airflows from different directions, speeding up the motion of updraft convergence in the lower atmosphere. Besides, the wind directions before and after the rainfall changed inversely with increasing height. Before the rain, the winds blew clockwise, but after the onset of the rain, the wind directions became counterclockwise mainly; （2） the temperature advection derived from wind profiler data can reproduce the characteristics of low-level thermodynamic evolution in the process of rainfall, which is capable to reflect the variation trend of hydrostatic stability in the atmosphere. In the early stage of the precipitation on 27 July, the lower atmosphere was mainly affected by warm advection which had accumulated unstable energy for the rainfall event and was beneficial for the occurrence of updraft motion and precipitation; （3） the ＂large-value zone＂ of the radar reflectivity factor Z was virtually consistent with the onset and end of the rainfall, the height for the formation of rain cloud particles, and precipitation intensity. The reflectivity factor Z during this event varied approximately in the range of 18-38 dBZ and the rain droplets formed mainly at the layer of 3,800-4,500 m.展开更多
[Objective] The hail weather and forecast storm in Guilin were studied. [Method] In allusion to the occurrence of hailstorm in Guilin and considering the observation data of a new generation of Doppler weather radar i...[Objective] The hail weather and forecast storm in Guilin were studied. [Method] In allusion to the occurrence of hailstorm in Guilin and considering the observation data of a new generation of Doppler weather radar in Guilin, the weather situation and radar echo characteristics in Guilin was summarized so as to explore the short time forecast method. [Result] There were one or two icy storms every year in Guilin. The occurrence of icy storm was distinctly influenced by terrain. A new generation of Doppler weather radar detection ice storm was very effective. The singular intensity of echo of icy storm in Guilin was above or equal to 50 dBz and the height of echo was above or equal to 10 km. The vertical liquid content was above or equal to 40 kg/m2, accompanied by mild cyclone. When there was strong icy storm, there were three flux characteristics. The forecast of icy storm was mainly short time forecast. [Conclusion] The study offered reference for the forecast of icy storm, artificial storm and disaster prevention and mitigation work.展开更多
[Objective] The aim was to study the change trend of accumulated temperature in Shenyang in recent 58 years, as well as its effect on agricultural production. [Method] Based on the surface temperature data in Shenyang...[Objective] The aim was to study the change trend of accumulated temperature in Shenyang in recent 58 years, as well as its effect on agricultural production. [Method] Based on the surface temperature data in Shenyang, the change trends of ≥0 ℃ and ≥10 ℃ accumulated temperature in Shenyang in recent 58 years were analyzed by means of climatic statistics method, and the effects of accumulated temperature variation on agricultural production were discussed. [Result] In recent 58 years, the first day with temperature ≥0 ℃ advanced 10 d, and the last day put off slightly, while sustained days prolonged 13 d, and ≥0 ℃ accumulated temperature increased by 343 ℃·d; meanwhile, the first day with temperature ≥10 ℃ advanced 9 d, and the last day put off 8 d, while sustained days prolonged 16 d, and ≥10 ℃ accumulated temperature increased by 370 ℃·d; compared with the first 20 years, sustained days with temperature ≥0 ℃ and ≥10 ℃ prolonged 9 d in the last 20 years, and ≥0 ℃ and ≥10 ℃ accumulated temperature increased by 196 and 202 ℃·d, respectively. In addition, the increase of heat resources affected agricultural production in Shenyang. [Conclusion] The study could provide theoretical foundation for grasping heat resources variation and adjusting agriculture distribution.展开更多
The climate data of 84 meteorological stations in Guizhou from 1981 to 2010 was used,including the statistical data of daily precipitation,temperature,sunshine hours,evaporation,frost free period and so on. Using the ...The climate data of 84 meteorological stations in Guizhou from 1981 to 2010 was used,including the statistical data of daily precipitation,temperature,sunshine hours,evaporation,frost free period and so on. Using the equations of light and heat coefficient,light and heat index,latitude and temperature index,active accumulated temperature,effective accumulated temperature,aridity index,and arid-wet index,the red cartridge kiwifruit zoning index of Guizhou was analyzed and studied. The results showed that the zoning index system for the climatic characteristics of Guizhou mountainous area must be established in order to realize the variety regionalization of red cartridge kiwifruit in Guizhou mountainous area,and ten climatic factors were taken as climatic zoning indexes of red cartridge kiwifruit planting,including active accumulated temperature,effective accumulated temperature,annual average temperature,average temperature of July,light and heat coefficient,light and heat index,latitude and temperature index,frost free period,aridity index and arid-wet index. These indicators were giving a comprehensive evaluation for climate suitability conditions of red cartridge kiwifruit planting,and providing the scientific and reasonable basis for the promotion planting of red cartridge kiwifruit in mountain area of Guizhou.展开更多
Extreme climate events have profound impacts on economies and livelihoods of many regions of the world. In Kenya, the extreme climate events often have strong impacts on agriculture production systems in the Arid and ...Extreme climate events have profound impacts on economies and livelihoods of many regions of the world. In Kenya, the extreme climate events often have strong impacts on agriculture production systems in the Arid and Semi-Arid Lands (ASALs). A small change in the mean climate condition can cause large changes in these production systems. There is a paucity of information on trends in climate and climate extremes in the country. However, a joint World Meteorological Commission for Climatology/World Climate Research Programme (WCPRP) project on climate Variability and Predictability (WMO CCl/CLIVAR) Expert Team (ET) on Climate Change Detection, Monitoring and Indices has defined 27 core climate indices mainly focusing on extreme events which can be derived through the use of RClimDex Software. In this study, therefore, the RClimDex software has been used to derive climate extreme indices for five stations in the ASALs of South-Eastern Kenya based on climate data for the period 1961 to 2009. The objective was to examine trends in these extremes to aid agricultural planning and practice. These indices have shown decreasing trends in annual rainfall, rainfall intensity and consecutive wet days but increasing trends in consecutive dry days. Steady warming patterns were evident in both the maximum and minimum temperature indices. This paper concludes that indeed significant changes in climate extremes are apparent in the ASALs of the country and recommends a re-thinking of planning and practice of rain-fed agriculture in the ASALs of South-Eastern Kenya.展开更多
As a follow-up of a previously published article on the contribution of tropical waves,this study explores the evolution of the mid-tropospheric mesoscale cyclonic vortex(MV)during the formation of Typhoon Megi(2010)w...As a follow-up of a previously published article on the contribution of tropical waves,this study explores the evolution of the mid-tropospheric mesoscale cyclonic vortex(MV)during the formation of Typhoon Megi(2010)with a successful cloud-resolving simulation.It is found that the formation and intensification of the MV were related to the deep convection and subsequent stratiform precipitation,while the weakening of the MV was related to the shallow convection.Both the upward transport of vorticity related to the deep convection and the horizontal convergence associated with the stratiform precipitation contributed to the formation and intensification of the MV.Even though the latter was dominant,the former could not be ignored,especially in the early stage of the MV.The MV played dual roles in the formation of Megi.On the one hand,the formation and intensification of MV were primarily associated with the stratiform precipitation,which induced the low-level divergence inhibiting the spin-up of the near-surface cyclonic circulation.On the other hand,the coupled low-level cold core under the MV benefited the accumulation of the convective available potential energy(CAPE),which was favorable for the convective activity.A sensitivity experiment with the evaporative cooling turned off indicated that the development of the MV retarded the genesis process of Megi.展开更多
[Objective] This paper studied the characteristics of lightning in Tong＇an district in Xiamen City based on the thunder observation and lightning location data. EMethod] Based on thunder observation and lightning loc...[Objective] This paper studied the characteristics of lightning in Tong＇an district in Xiamen City based on the thunder observation and lightning location data. EMethod] Based on thunder observation and lightning location data in Tong＇an district from 2005 to 2010, the distribution characteristics of lightning in Tong＇an district were analyzed. [ Resldt~ Thunder and lightning occurred frequently from March to November and was very active during May and September. Spatial distribution was uneven, more frequently in northern mountainous area and less in south plain area. The related circulation patterns and weather were also studied. The weather type causing severe lightning can be divided into three categories and six types, which were the upper air trough, under the control of the subtropical high and tropical systems, respectively. [ Conclusion] The study pro- vided reference for carrying out damage evaluation, pre-waming and report of thunder and lightning.展开更多
1 INTRODUCTION Sudden changes in the intensity of the tropical cyclone （TC） are a difficult issue to be tackled. Few of the previous works dealt with the characteristics of large-scale circulation background of TCs...1 INTRODUCTION Sudden changes in the intensity of the tropical cyclone （TC） are a difficult issue to be tackled. Few of the previous works dealt with the characteristics of large-scale circulation background of TCs that experience sudden intensity changes prior to landfall. Studies that do address the issue are only case-based, which do not isolate large-scale circulation background common to all cases, whether it be favorable or not. By diagnostically studying large-scale characteristics of two categories of TCs, one intensifying and the other weakening, suddenly, before making landfall on the area of South China, the current work attempts to support the prediction of TC intensity.展开更多
According to the data in the past nine years in Heyuan urban district and its adjacent five counties,annual,seasonal and monthly change characteristics of heat island effect in Heyuan City and its meteorological influ...According to the data in the past nine years in Heyuan urban district and its adjacent five counties,annual,seasonal and monthly change characteristics of heat island effect in Heyuan City and its meteorological influence factors were analyzed. The results showed that the intensity of heat island effect in central urban district and suburb of Heyuan City overall showed an upward trend from 2007 to 2015. From 2007 to 2012,heat island effect showed a slow weakening trend; from 2012 to 2013,heat island effect significantly enhanced and then weakened; after 2013,heat island effect significantly reduced. Heat island effect of Heyuan was the strongest in winter,followed by autumn,and it was the weakest in summer.The strongest heat island effect occurred in October,while the weakest occurred in July. According to the grey correlation analysis,the main factors affecting urban heat island effect of Heyuan were analyzed,and the order of each influence factor was as follows: average wind speed > relative humidity > rainfall > sunshine hours.展开更多
While previous studies indicate that typhoons can decrease sea surface temperature(SST) along their tracks, a few studies suggest that the cooling patterns in coastal areas are different from those in the open sea. Ho...While previous studies indicate that typhoons can decrease sea surface temperature(SST) along their tracks, a few studies suggest that the cooling patterns in coastal areas are different from those in the open sea. However, little is known about how the induced cooling coupled with the complex ocean circulation in the coastal areas can affect tropical cyclone track and intensity. The sea surface responses to the land falling process of Typhoon Morakot(2009) are examined observationally and its influences on the activity of the typhoon are numerically simulated with the WRF model. The present study shows that the maximum SST cooling associated with Morakot occurred on the left-hand side of the typhoon track during its landfall. Numerical simulations show that, together with the SST gradients associated with the coastal upwelling and mesoscale oceanic vortices, the resulting SST cooling can cause significant difference in the typhoon track, comparable to the current 24-hour track forecasting error. It is strongly suggested that it is essential to include the non-uniform SST distribution in the coastal areas for further improvement in typhoon track forecast.展开更多
Aiming at piezoresistive pressure sensors, this paper studies simulation of standard pressure by using benchmark current source and self-calibration of the sampling data characteristics. A data fusion algorithm for sa...Aiming at piezoresistive pressure sensors, this paper studies simulation of standard pressure by using benchmark current source and self-calibration of the sampling data characteristics. A data fusion algorithm for sample set is presented which transforms a surface problem into a curve fitting and interpolation problem. The simulation result shows that benchmark current source simulating pressure is successful and data fusion algorithm is effective. The maximum measurement error is only 0.098 kPa and maximum relative error is 0.92% at 0-45 kPa and -10-45~C.展开更多
基金National Natural Science Foundation of China(U2142205)Science and Technology Research Project of the Guangdong Meteorological Service(GRMC2021M13,GRMC2023M11)。
文摘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 precipitation 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.
基金supported by the National Natural Science Foundation of China (Grant Nos.91637211 and 41375051)the National Key Research and Development Program of China (Grant No.2017YFC1502003)
文摘Diurnal variations in amount, frequency and intensity of warm-season hourly precipitation(HP) at seven levels, which are defined as HP 0.1, 0.5, 1, 5, 10, 20 and 50 mm, are revealed based on no less than 30 years of hourly rain-gauge observations at national stations over central and eastern China(CEC). This study investigates the variations, relationships, differences and similarities of total, stratiform, convective and extreme HP over the entire CEC and various subregions. Results indicate that the variations in the amount and frequency of HP at the seven levels over the entire CEC all display a bimodal feature. For various regions, the variations of total HP mostly feature two peaks, while convective HP mainly occurs in the late afternoon and determines the diurnal variation of total HP intensity. On the basis of the primary peak time periods of HP frequency at all levels over different subregions, the variations can be classified into three main categories: late-afternoon primary peak, nocturnal primary peak, and time-shifting primary peak. However, the variations over some coastal regions like the Liaodong Peninsula, the Shandong Peninsula, and the coastal regions of Guangdong, distinctly differ from those over their corresponding larger regions. Overall, the normalized diurnal variation amplitude of amount and frequency increases with the increasing HP intensity; convective precipitation can be represented by HP 10 mm; and the intensity of HP 50 mm is slightly larger during the nighttime than during the daytime over the entire CEC. In northern China, diurnal variation in HP 5 mm can represent well that in convective precipitation.
基金supported by the program under Grant No.2007BAC29B04
文摘Based on a daily precipitation observation dataset of 743 stations in China from 1951 2004, the F distribution function is used to calculate the probability distribution of daily precipitation and to define extreme precipitation events. Based on this, the relationship of ENSO and the frequency of extreme precipitation events is studied. Results reveal that ENSO events have impact on extreme precipitation events, with different magnitudes at different regions and seasons. In general, during winter and spring, extreme precipitation events occur more often during E1 Nino events than during La Nina events. While during summer and autumn, the opposite is found. The relationship of a two season-lag ENSO and extreme precipitation frequency shows different pattern. Extreme precipitation events occur more often in several regions if an ENSO warm phase happened in the central-eastern tropical Pacific two seasons before. No similar impacts of El Nino and La Nina on the frequency of extreme precipitation events are found.
基金supported by the National Key Basic Research Special Foundation Project(2007CB106803)National Natural Science Foundation(40801111, 41001137)One hundred-Talent Plan of Chinese Academy of Sciences,the CAS/SAFEA International Partnership Program for Creative Research Teams,and the Program for Youthful Talents in Northwest A and F University
文摘Plants play an important role in soil phosphorus nutrition. However, the effect of plants on phosphorus nutrition in soils of the Loess Plateau of China is not well understood. This study was conducted to reveal the relationships between plants and phosphorus＇ fractions and availability in the Loess Plateau of China. Twenty-two plant communities were surveyed and soil samples under different plant canopies were collected for the determination of soil properties and inorganic phosphorus fractionation. The results showed that Leguminosae and Lilaceae reduced pH and increased organic matter, cation exchange capacity, total and Olsen phosphorus in soils under their canopies, while Labiatae and Rosaceae increased pH and decreased organic matter, cation exchange capacity, total and Olsen phosphorus in soils under their canopies. The contents of Ca2P, CasP, AI-P and Fe-P were highly related with soil Oisen phosphorus. They were all higher in soils under Leguminosae and Lilaceae and lower in softs under Labiatae and Rosaceae. The results of this study indicate that Leguminosae and Lilaceae improved phosphorus nutrition in soils, yet Labiatae and Rosaceae impeded the improvement of phosphorus nutrition in soils under their canopies, which will be of more help to instruct vegetation restoration in the region and provide information for soil development.
基金supported by the National Natural Science Foundation of China(Grant Nos.41175035 and 40475018)the National Basic Research Program of China(Grant No.2009CB421502)a project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘The operational cloud-motion tracking technique fails to retrieve atmospheric motion vectors （AMVs） in areas lacking cloud; and while water vapor shown in water vapor imagery can be used, the heights assigned to the retrieved AMVs are mostly in the upper troposphere. As the noise-equivalent temperature difference （NEdT） performance of FY-2E split win- dow （10.3-11.5 μm, 11.6-12.8 μm） channels has been improved, the weak signals representing the spatial texture of water vapor and aerosols in cloud-free areas can be strengthened with algorithms based on the difference principle, and applied in calculating AMVs in the lower troposphere. This paper is a preliminary summary for this purpose, in which the principles and algorithm schemes for the temporal difference, split window difference and second-order difference （SD） methods are introduced. Results from simulation and cases experiments are reported in order to verify and evaluate the methods, based on comparison among retrievals and the ＂truth＂. The results show that all three algorithms, though not perfect in some cases, generally work well. Moreover, the SD method appears to be the best in suppressing the surface temperature influence and clarifying the spatial texture of water vapor and aerosols. The accuracy with respect to NCEP 800 hPa reanalysis data was found to be acceptable, as compared with the accuracy of the cloud motion vectors.
基金supported by the National Natural Science Foundation of China (Grant Nos.41175035 and 41005005)the National Basic Research Program of China (Grant No.2009CB421502)a project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘The aim of this study is to calculate the low-level atmospheric motion vectors （AMVs） in clear areas with FY-2E IR2 window （11.59-12.79 μm） channel imagery,where the traditional cloud motion wind technique fails.A new tracer selection procedure,which we call the temporal difference technique,is demonstrated in this paper.This technique makes it possible to infer low-level wind by tracking features in the moisture pattern that appear as brightness temperature （TB） differences between consecutive sequences of 30-min-interval FY-2E IR2 images over cloud-free regions.The TB difference corresponding to a 10％ change in water vapor density is computed with the Moderate Resolution Atmospheric Transmission （MODTRAN4） radiative transfer model.The total contribution from each of the 10 layers is analyzed under four typical atmospheric conditions：tropical,midlatitude summer,U.S.standard,and midlatitude winter.The peak level of the water vapor weighting function for the four typical atmospheres is assigned as a specific height to the TB ＂wind＂.This technique is valid over cloudfree ocean areas.The proposed algorithm exhibits encouraging statistical results in terms of vector difference （VD）,speed bias （BIAS）,mean vector difference （MVD）,standard deviation （SD）,and root-mean-square error （RMSE）,when compared with the wind field of NCEP reanalysis data and rawinsonde observations.
基金Supported by Natural Science Foundation of Liaoning Province(20102109)
文摘[Objective] The aim was to study the change characteristics of temperature and heat resources in rural area of Chaoyang in western Liaoning. [Method] Based on the data from rural meteorological station in Chaoyang in western Liaoning from 1966 to 2010, the change characteristics of temperature and heat resources in rural area in Chaoyang were analyzed by means of serial correlation and climate tendency method, so as to master its climate situation. [Result] The annual average value of daily average temperature, daily maximum temperature and daily minimum temperature in rural area of Chaoyang in western Liaoning from 1966 to 2010 showed fluctuation variation, and the annual average value of daily maximum temperature increased most obviously with the climatic tendency of 0.328 ℃/10 a and highest significant level, so it played an important role in temperature increase, next came daily average temperature (0.151 ℃/10 a), while there was no obvious decrease in daily minimum temperature. The average of daily maximum temperature in winter half year increased more obviously than that in summer half year, with the climatic tendency of 0.417 and 0.250 ℃/10 a, respectively; the trend of daily average temperature reached low significant level, and there was no obvious variation in daily minimum temperature. In addition, ≥10 ℃ accumulated temperature in rural area of Chaoyang in western Liaoning went up obviously, with the climatic tendency of 42.59 ℃·d/10 a, namely it increased by 192 ℃·d in recent 45 years. [Conclusion] The study could provide climatic reference for the adjustment of agriculture structure and varieties distribution.
基金Project supported by the National Basic Research Program of China(Grant No.2012CB955902)the National Natural Science Foundation of China(Grant Nos.41275074,41475073,and 41175084)
文摘In the present paper, a comparison of the performance between moving cutting data-rescaled range analysis （MC- R/S） and moving cutting data-rescaled variance analysis （MC-V/S） is made. The results clearly indicate that the operating efficiency of the MC-R/S algorithm is higher than that of the MC-V/S algorithm. In our numerical test, the computer time consumed by MC-V/S is approximately 25 times that by MC-R/S for an identical window size in artificial data. Except for the difference in operating efficiency, there are no significant differences in performance between MC-R/S and MC-V/S for the abrupt dynamic change detection. Mc-R/s and MC-V/S both display some degree of anti-noise ability. However, it is important to consider the influences of strong noise on the detection results of MC-R/S and MC-V/S in practical application
文摘In this paper the differences between Meiyu and Baiu front in 1983 have firstly been analysed, the trajectories of air on and to the north side of Meiyu and Baiu fronts during the Meiyu period have then been traced, and the forecasting and simulating of 4 sets of Meiyu onset of the year have finally been run utilizing the global model at UK Me-leorological Office. The results show: 1) Meiyu fronts are different from Baiu ones in temperature, humidity and stratification fields in lower atmosphere; and the possibly reasons for it are explained. 2) The Bay of Bengal is the main moisture source for Meiyu front, the South China Sea and the Pacific, for Baiu ones; and some existed arguments on it are also discussed. 3) The onset of Meiyu and its rainfall and rain belts are sensitive to the Tibetan Plateau, and the water vapour conditions over the Bay of Bengal and the South China Sea, but not sensitive to the SST over the equatorial area or to the East of Japan.
基金co-funded by the National Basic Research Program of China(2010CB951001)the Research Subject with the Support of National Science and Technology(2012BA C23B01)the Central Scientific Research and Operational Project(IDM201002)
文摘To improve the level of meteorological service for the Oilfield region in the Taklimakan Desert, the Urumqi Institute of Desert Meteorology of the China Meteorological Administration （CMA） conducted a detection experiment by means of wind profiling radar （WPR） in Tazhong Oilfield region of Xinjiang, China in July 2010. By using the wind profiler data obtained during the rainfall process on 27 July, this paper analyzed the wind field fea- tures and some related scientific issues of this weather event. The results indicated that： （1） wind profiler data had high temporal resolution and vertical spatial resolution, and could be used to analyze detailed vertical structures of rainfall processes and the characteristics of meso-scale systems. Before and after the rain event on 27 July, the wind field showed multi-layer vertical structures, having an obvious meso-scale wind shear line and three airflows from different directions, speeding up the motion of updraft convergence in the lower atmosphere. Besides, the wind directions before and after the rainfall changed inversely with increasing height. Before the rain, the winds blew clockwise, but after the onset of the rain, the wind directions became counterclockwise mainly; （2） the temperature advection derived from wind profiler data can reproduce the characteristics of low-level thermodynamic evolution in the process of rainfall, which is capable to reflect the variation trend of hydrostatic stability in the atmosphere. In the early stage of the precipitation on 27 July, the lower atmosphere was mainly affected by warm advection which had accumulated unstable energy for the rainfall event and was beneficial for the occurrence of updraft motion and precipitation; （3） the ＂large-value zone＂ of the radar reflectivity factor Z was virtually consistent with the onset and end of the rainfall, the height for the formation of rain cloud particles, and precipitation intensity. The reflectivity factor Z during this event varied approximately in the range of 18-38 dBZ and the rain droplets formed mainly at the layer of 3,800-4,500 m.
文摘[Objective] The hail weather and forecast storm in Guilin were studied. [Method] In allusion to the occurrence of hailstorm in Guilin and considering the observation data of a new generation of Doppler weather radar in Guilin, the weather situation and radar echo characteristics in Guilin was summarized so as to explore the short time forecast method. [Result] There were one or two icy storms every year in Guilin. The occurrence of icy storm was distinctly influenced by terrain. A new generation of Doppler weather radar detection ice storm was very effective. The singular intensity of echo of icy storm in Guilin was above or equal to 50 dBz and the height of echo was above or equal to 10 km. The vertical liquid content was above or equal to 40 kg/m2, accompanied by mild cyclone. When there was strong icy storm, there were three flux characteristics. The forecast of icy storm was mainly short time forecast. [Conclusion] The study offered reference for the forecast of icy storm, artificial storm and disaster prevention and mitigation work.
基金Supported by Scientific Research Project of Shenyang Science and Technology Bureau([2010]Number 15)
文摘[Objective] The aim was to study the change trend of accumulated temperature in Shenyang in recent 58 years, as well as its effect on agricultural production. [Method] Based on the surface temperature data in Shenyang, the change trends of ≥0 ℃ and ≥10 ℃ accumulated temperature in Shenyang in recent 58 years were analyzed by means of climatic statistics method, and the effects of accumulated temperature variation on agricultural production were discussed. [Result] In recent 58 years, the first day with temperature ≥0 ℃ advanced 10 d, and the last day put off slightly, while sustained days prolonged 13 d, and ≥0 ℃ accumulated temperature increased by 343 ℃·d; meanwhile, the first day with temperature ≥10 ℃ advanced 9 d, and the last day put off 8 d, while sustained days prolonged 16 d, and ≥10 ℃ accumulated temperature increased by 370 ℃·d; compared with the first 20 years, sustained days with temperature ≥0 ℃ and ≥10 ℃ prolonged 9 d in the last 20 years, and ≥0 ℃ and ≥10 ℃ accumulated temperature increased by 196 and 202 ℃·d, respectively. In addition, the increase of heat resources affected agricultural production in Shenyang. [Conclusion] The study could provide theoretical foundation for grasping heat resources variation and adjusting agriculture distribution.
基金Supported by Innovation Driven Project of China Association for Science(2017ZLGC004)Provincial and Municipal Scientific and Technological Cooperation Projects(52020-2015-01-02)Guizhou Science and Technology Plan Project(Qiankehe NY[2012]3020)
文摘The climate data of 84 meteorological stations in Guizhou from 1981 to 2010 was used,including the statistical data of daily precipitation,temperature,sunshine hours,evaporation,frost free period and so on. Using the equations of light and heat coefficient,light and heat index,latitude and temperature index,active accumulated temperature,effective accumulated temperature,aridity index,and arid-wet index,the red cartridge kiwifruit zoning index of Guizhou was analyzed and studied. The results showed that the zoning index system for the climatic characteristics of Guizhou mountainous area must be established in order to realize the variety regionalization of red cartridge kiwifruit in Guizhou mountainous area,and ten climatic factors were taken as climatic zoning indexes of red cartridge kiwifruit planting,including active accumulated temperature,effective accumulated temperature,annual average temperature,average temperature of July,light and heat coefficient,light and heat index,latitude and temperature index,frost free period,aridity index and arid-wet index. These indicators were giving a comprehensive evaluation for climate suitability conditions of red cartridge kiwifruit planting,and providing the scientific and reasonable basis for the promotion planting of red cartridge kiwifruit in mountain area of Guizhou.
文摘Extreme climate events have profound impacts on economies and livelihoods of many regions of the world. In Kenya, the extreme climate events often have strong impacts on agriculture production systems in the Arid and Semi-Arid Lands (ASALs). A small change in the mean climate condition can cause large changes in these production systems. There is a paucity of information on trends in climate and climate extremes in the country. However, a joint World Meteorological Commission for Climatology/World Climate Research Programme (WCPRP) project on climate Variability and Predictability (WMO CCl/CLIVAR) Expert Team (ET) on Climate Change Detection, Monitoring and Indices has defined 27 core climate indices mainly focusing on extreme events which can be derived through the use of RClimDex Software. In this study, therefore, the RClimDex software has been used to derive climate extreme indices for five stations in the ASALs of South-Eastern Kenya based on climate data for the period 1961 to 2009. The objective was to examine trends in these extremes to aid agricultural planning and practice. These indices have shown decreasing trends in annual rainfall, rainfall intensity and consecutive wet days but increasing trends in consecutive dry days. Steady warming patterns were evident in both the maximum and minimum temperature indices. This paper concludes that indeed significant changes in climate extremes are apparent in the ASALs of the country and recommends a re-thinking of planning and practice of rain-fed agriculture in the ASALs of South-Eastern Kenya.
基金supported in part by the National Key Research and Development Program of China(Grant No.2017YFC1501601)the National Natural Science Foundation of China(Grant No.41875067)。
文摘As a follow-up of a previously published article on the contribution of tropical waves,this study explores the evolution of the mid-tropospheric mesoscale cyclonic vortex(MV)during the formation of Typhoon Megi(2010)with a successful cloud-resolving simulation.It is found that the formation and intensification of the MV were related to the deep convection and subsequent stratiform precipitation,while the weakening of the MV was related to the shallow convection.Both the upward transport of vorticity related to the deep convection and the horizontal convergence associated with the stratiform precipitation contributed to the formation and intensification of the MV.Even though the latter was dominant,the former could not be ignored,especially in the early stage of the MV.The MV played dual roles in the formation of Megi.On the one hand,the formation and intensification of MV were primarily associated with the stratiform precipitation,which induced the low-level divergence inhibiting the spin-up of the near-surface cyclonic circulation.On the other hand,the coupled low-level cold core under the MV benefited the accumulation of the convective available potential energy(CAPE),which was favorable for the convective activity.A sensitivity experiment with the evaporative cooling turned off indicated that the development of the MV retarded the genesis process of Megi.
文摘[Objective] This paper studied the characteristics of lightning in Tong＇an district in Xiamen City based on the thunder observation and lightning location data. EMethod] Based on thunder observation and lightning location data in Tong＇an district from 2005 to 2010, the distribution characteristics of lightning in Tong＇an district were analyzed. [ Resldt~ Thunder and lightning occurred frequently from March to November and was very active during May and September. Spatial distribution was uneven, more frequently in northern mountainous area and less in south plain area. The related circulation patterns and weather were also studied. The weather type causing severe lightning can be divided into three categories and six types, which were the upper air trough, under the control of the subtropical high and tropical systems, respectively. [ Conclusion] The study pro- vided reference for carrying out damage evaluation, pre-waming and report of thunder and lightning.
基金Natural Science Foundation of China (402750184997501440333025)
文摘1 INTRODUCTION Sudden changes in the intensity of the tropical cyclone （TC） are a difficult issue to be tackled. Few of the previous works dealt with the characteristics of large-scale circulation background of TCs that experience sudden intensity changes prior to landfall. Studies that do address the issue are only case-based, which do not isolate large-scale circulation background common to all cases, whether it be favorable or not. By diagnostically studying large-scale characteristics of two categories of TCs, one intensifying and the other weakening, suddenly, before making landfall on the area of South China, the current work attempts to support the prediction of TC intensity.
文摘According to the data in the past nine years in Heyuan urban district and its adjacent five counties,annual,seasonal and monthly change characteristics of heat island effect in Heyuan City and its meteorological influence factors were analyzed. The results showed that the intensity of heat island effect in central urban district and suburb of Heyuan City overall showed an upward trend from 2007 to 2015. From 2007 to 2012,heat island effect showed a slow weakening trend; from 2012 to 2013,heat island effect significantly enhanced and then weakened; after 2013,heat island effect significantly reduced. Heat island effect of Heyuan was the strongest in winter,followed by autumn,and it was the weakest in summer.The strongest heat island effect occurred in October,while the weakest occurred in July. According to the grey correlation analysis,the main factors affecting urban heat island effect of Heyuan were analyzed,and the order of each influence factor was as follows: average wind speed > relative humidity > rainfall > sunshine hours.
基金National Key Technology Research and Development Program of China(2009CB421503)New Recruitment Graduate Project of the Fujian Province Meteorological Bureau(2012G01)
文摘While previous studies indicate that typhoons can decrease sea surface temperature(SST) along their tracks, a few studies suggest that the cooling patterns in coastal areas are different from those in the open sea. However, little is known about how the induced cooling coupled with the complex ocean circulation in the coastal areas can affect tropical cyclone track and intensity. The sea surface responses to the land falling process of Typhoon Morakot(2009) are examined observationally and its influences on the activity of the typhoon are numerically simulated with the WRF model. The present study shows that the maximum SST cooling associated with Morakot occurred on the left-hand side of the typhoon track during its landfall. Numerical simulations show that, together with the SST gradients associated with the coastal upwelling and mesoscale oceanic vortices, the resulting SST cooling can cause significant difference in the typhoon track, comparable to the current 24-hour track forecasting error. It is strongly suggested that it is essential to include the non-uniform SST distribution in the coastal areas for further improvement in typhoon track forecast.
基金Project supported by the National Natural Science Foundation of China （Grant No.40265001）, and the Science Foundation of Yunnan Province （Grant No.2002C0038M）
文摘Aiming at piezoresistive pressure sensors, this paper studies simulation of standard pressure by using benchmark current source and self-calibration of the sampling data characteristics. A data fusion algorithm for sample set is presented which transforms a surface problem into a curve fitting and interpolation problem. The simulation result shows that benchmark current source simulating pressure is successful and data fusion algorithm is effective. The maximum measurement error is only 0.098 kPa and maximum relative error is 0.92% at 0-45 kPa and -10-45~C.
