ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 38,Issue 1,2012 Table of Contents
2012, 38(1):1-16.
DOI: 10.7519/j.issn.1000-0526.2012.01.001
Abstract:
In this paper, the modulation of atmospheric MJO on typhoon generation over the northwestern Pacific and its mechanism are first studied by using the MJO index. The results show that the MJO plays an important modulation role in typhoon generation over the northwestern Pacific: The proportion of typhoon number is 21 between active period and inactive period; During the MJO active period, the proportion of typhoon number is also 2:1 between phases 5-6 and phases 2-3 of MJO. The composite analyses of atmospheric circulation show that there are different circulation patterns over the northwestern Pacific in different phases of the MJO, which will affect the typhoon generation. In phases 5-6 (2-3), the dynamic factor and convective heating patterns over western Pacific are favorable (unfavorable) for typhoon generation. Then， the comparing analyses of the 30-60 day lowfrequency kinetic energy in lower and higher levels of the troposphere show that the atmospheric intraseasonal oscillation over the northwestern Pacific has a clear impact on the typhoon generation. There is an evident positive (negative) anomaly area of 30-60 day lowfrequency kinetic energy in the more (less) typhoon years over the northwestern Pacific east of the Philippines, which means that strong (weak) atmospheric intraseasonal oscillation (ISO) over the northwestern Pacific is favorable (unfavorable) for typhoon generation. The analyses of 200 hPa velocity potential show that there is a clear divergence (convergence) pattern over the northwestern Pacific in the more (less) typhoon years, which is favorable (unfavorable) for typhoon generation. The modulation of the intraseasonal oscillation on the typhoon tracks over the northwestern Pacific is studied by observational data analyses. We classified the main classes of typhoon tracks into 5 types as straight westmoving typhoons (I), northwestmoving typhoons (II), recurving to Korea/west of Japan typhoons (III), landing on Japan typhoons (IV) and recurving to the east of Japan typhoons (V). Then the composite analyses of atmospheric low-frequency wind fields at 850, 500 and 200 hPa, corresponding to the typhoon forming date, for every typhoon track are completed. The analysis results of relationships between the low-frequency (ISO) wind fields and typhoon tracks have indicated that the typhoon tracks will be affected by wind pattern of the ISO. The low frequency positive vorticity belt (the maximum value line of cyclonic vorticity) associated with low-frequency cyclone (LFC) at 850 hPa is so closely related to the typhoon track, that the maximum value line (belt) of low frequency cyclonic vorticity can be an important factor to predicate the typhoon tracks over the northwestern Pacific. And the typhoon tracks will be also affected by the ISO circulation pattern at 200 hPa, particularly the strong low frequency wind associated with low frequency anticyclone (LFAC).
In this paper, the modulation of atmospheric MJO on typhoon generation over the northwestern Pacific and its mechanism are first studied by using the MJO index. The results show that the MJO plays an important modulation role in typhoon generation over the northwestern Pacific: The proportion of typhoon number is 21 between active period and inactive period; During the MJO active period, the proportion of typhoon number is also 2:1 between phases 5-6 and phases 2-3 of MJO. The composite analyses of atmospheric circulation show that there are different circulation patterns over the northwestern Pacific in different phases of the MJO, which will affect the typhoon generation. In phases 5-6 (2-3), the dynamic factor and convective heating patterns over western Pacific are favorable (unfavorable) for typhoon generation. Then， the comparing analyses of the 30-60 day lowfrequency kinetic energy in lower and higher levels of the troposphere show that the atmospheric intraseasonal oscillation over the northwestern Pacific has a clear impact on the typhoon generation. There is an evident positive (negative) anomaly area of 30-60 day lowfrequency kinetic energy in the more (less) typhoon years over the northwestern Pacific east of the Philippines, which means that strong (weak) atmospheric intraseasonal oscillation (ISO) over the northwestern Pacific is favorable (unfavorable) for typhoon generation. The analyses of 200 hPa velocity potential show that there is a clear divergence (convergence) pattern over the northwestern Pacific in the more (less) typhoon years, which is favorable (unfavorable) for typhoon generation. The modulation of the intraseasonal oscillation on the typhoon tracks over the northwestern Pacific is studied by observational data analyses. We classified the main classes of typhoon tracks into 5 types as straight westmoving typhoons (I), northwestmoving typhoons (II), recurving to Korea/west of Japan typhoons (III), landing on Japan typhoons (IV) and recurving to the east of Japan typhoons (V). Then the composite analyses of atmospheric low-frequency wind fields at 850, 500 and 200 hPa, corresponding to the typhoon forming date, for every typhoon track are completed. The analysis results of relationships between the low-frequency (ISO) wind fields and typhoon tracks have indicated that the typhoon tracks will be affected by wind pattern of the ISO. The low frequency positive vorticity belt (the maximum value line of cyclonic vorticity) associated with low-frequency cyclone (LFC) at 850 hPa is so closely related to the typhoon track, that the maximum value line (belt) of low frequency cyclonic vorticity can be an important factor to predicate the typhoon tracks over the northwestern Pacific. And the typhoon tracks will be also affected by the ISO circulation pattern at 200 hPa, particularly the strong low frequency wind associated with low frequency anticyclone (LFAC).
2012, 38(1):17-27.
DOI: 10.7519/j.issn.1000-0526.2012.01.002
Abstract:
The potential vorticity (PV) theory is based on the analysis methods of isentropic PV. This paper aimed at the introduction to the basic concepts and methods which are necessary to grasp to do the analysis of isentropic PV. It first gave the fundamentals of potential temperature and PV, troposphere and stratosphere, front and tropopause, and then discussed the characteristics of front and tropopause in the vertical cross sections, isobaric surface maps, and isentropic surface maps. Different kinds of chart instances were illustrated in this paper. Through analyses and comparisons, the results are obtained as follows. The high PV in stratosphere originates from the large vertical gradient of potential temperature which increases sharply with height above the tropopause. The vertical gradient of potential temperature is the main factor which determines PV distribution. The isentropic PV maps mainly reflect the activity of polar air mass, and the front, jet, and tropopause closely associated with polar air mass. In the end, this paper pointed out that some wrong knowledges should be avoided in the isentropic PV analyses, especially, we should avoid treating streamlines in the isentropic surface as trajectories and cannot obtain such a wrong deduction that the stratospheric dry air can intrude into the lower troposphere.
The potential vorticity (PV) theory is based on the analysis methods of isentropic PV. This paper aimed at the introduction to the basic concepts and methods which are necessary to grasp to do the analysis of isentropic PV. It first gave the fundamentals of potential temperature and PV, troposphere and stratosphere, front and tropopause, and then discussed the characteristics of front and tropopause in the vertical cross sections, isobaric surface maps, and isentropic surface maps. Different kinds of chart instances were illustrated in this paper. Through analyses and comparisons, the results are obtained as follows. The high PV in stratosphere originates from the large vertical gradient of potential temperature which increases sharply with height above the tropopause. The vertical gradient of potential temperature is the main factor which determines PV distribution. The isentropic PV maps mainly reflect the activity of polar air mass, and the front, jet, and tropopause closely associated with polar air mass. In the end, this paper pointed out that some wrong knowledges should be avoided in the isentropic PV analyses, especially, we should avoid treating streamlines in the isentropic surface as trajectories and cannot obtain such a wrong deduction that the stratospheric dry air can intrude into the lower troposphere.
2012, 38(1):28-40.
DOI: 10.7519/j.issn.1000-0526.2012.01.003
Abstract:
In weather forecasting, there are some improper uses of the concept of stratospheric dry air intrusion into troposphere deduced from the isentropic potential vorticity (PV) analyses. This paper reviewed the history of weather forecast from pressure change to vorticity change, and discussed the origin of PV concept. Furthermore, based on the definition, mathematical expression, physical meaning, and computation of PV, this paper showed that PV value is mainly determined by the vertical gradient of potential temperature, and PV distribution reflects tropopause distribution, and thus indirectly reflects the distribution of polar air mass, front, upper-level trough and jet stream. The trajectories and model simulation both show that the PV anomaly in the lower atmosphere is resulting from the strong deepening of surface cyclone and the feedback of latent heat, instead from dry intrusion. This paper also pointed out that the law of PV conservation cannot be used to replace the dynamic mechanism of baroclinic disturbance development. The misuse of PV is from the heuristics of PV conservation and the confusion between trajectories and streamlines used in fluid mechanics.
In weather forecasting, there are some improper uses of the concept of stratospheric dry air intrusion into troposphere deduced from the isentropic potential vorticity (PV) analyses. This paper reviewed the history of weather forecast from pressure change to vorticity change, and discussed the origin of PV concept. Furthermore, based on the definition, mathematical expression, physical meaning, and computation of PV, this paper showed that PV value is mainly determined by the vertical gradient of potential temperature, and PV distribution reflects tropopause distribution, and thus indirectly reflects the distribution of polar air mass, front, upper-level trough and jet stream. The trajectories and model simulation both show that the PV anomaly in the lower atmosphere is resulting from the strong deepening of surface cyclone and the feedback of latent heat, instead from dry intrusion. This paper also pointed out that the law of PV conservation cannot be used to replace the dynamic mechanism of baroclinic disturbance development. The misuse of PV is from the heuristics of PV conservation and the confusion between trajectories and streamlines used in fluid mechanics.
2012, 38(1):41-55.
DOI: 10.7519/j.issn.1000-0526.2012.01.004
Abstract:
In this work, a new method of prediction of China summer precipitation was suggested. The new ensemble method is a combination of singular spectrum analysismaximum entropy method (SSA MEM) and optimal subset regression (OSR), in which the inner characteristics of the series and influence of outer forcing factors are both calculated. The hindcast of the summer precipitation during period of 1961-2000, and the prediction of 2001-2004 are made separately. Results show that the anomaly correlation between the hindcast and the observed of precipitation for 160 stations reaches 0.85, passing through significance level of 0.01.The accuracy of summer prediction is obviously over 69%, which is slightly better than climate prediction on average. It indicates that the performance of the method suggested in this paper is well on the prediction of summer precipitation and is especially well over Northeast and Southwest China, which stands for its application into prediction practice.
In this work, a new method of prediction of China summer precipitation was suggested. The new ensemble method is a combination of singular spectrum analysismaximum entropy method (SSA MEM) and optimal subset regression (OSR), in which the inner characteristics of the series and influence of outer forcing factors are both calculated. The hindcast of the summer precipitation during period of 1961-2000, and the prediction of 2001-2004 are made separately. Results show that the anomaly correlation between the hindcast and the observed of precipitation for 160 stations reaches 0.85, passing through significance level of 0.01.The accuracy of summer prediction is obviously over 69%, which is slightly better than climate prediction on average. It indicates that the performance of the method suggested in this paper is well on the prediction of summer precipitation and is especially well over Northeast and Southwest China, which stands for its application into prediction practice.
2012, 38(1):47-55.
DOI: 10.7519/j.issn.1000-0526.2012.01.005
Abstract:
This study constructed a method of ensemble linear cross-correlation and conducted Doppler radar echo extrapolation. The linear cross-correlation algorithm can obtain the echo distribution based on the previous two echo times. As a result, the ensemble linear cross-correlation technique is more close to the observed and has been taken into account the nonlinear characteristics, which involve the evolution, moving speed and direction, and deformation during the movement of multi-time echoes. According to the methods of ensemble linear cross correlation and least squares fitting, the echo extrapolation of two rainstorm processes has been carried out. By comparison, the echo distribution derived from the ensemble cross-correlation is more realistic. Further analysis of precipitation evaluation indicates that the echo movement derived by ensemble linear cross-correlation is more similar to the observed, and gets better 1 h accumulated precipitation forecast. Therefore, the ensemble cross-correlation extrapolation technique has certain practical value in nowcasting.
This study constructed a method of ensemble linear cross-correlation and conducted Doppler radar echo extrapolation. The linear cross-correlation algorithm can obtain the echo distribution based on the previous two echo times. As a result, the ensemble linear cross-correlation technique is more close to the observed and has been taken into account the nonlinear characteristics, which involve the evolution, moving speed and direction, and deformation during the movement of multi-time echoes. According to the methods of ensemble linear cross correlation and least squares fitting, the echo extrapolation of two rainstorm processes has been carried out. By comparison, the echo distribution derived from the ensemble cross-correlation is more realistic. Further analysis of precipitation evaluation indicates that the echo movement derived by ensemble linear cross-correlation is more similar to the observed, and gets better 1 h accumulated precipitation forecast. Therefore, the ensemble cross-correlation extrapolation technique has certain practical value in nowcasting.
2012, 38(1):56-65.
DOI: 10.7519/j.issn.1000-0526.2012.01.006
Abstract:
Based on the observation data of the lightning location system, temperature of blackbody brightness, Doppler radar echo and denser surface precipitation measurements from the process of a heavy rainstorm during 8-9 August 2007 in the Central Shaanxi Plain, the characteristics of ground lightning，and relationships of ground lightning, MCS, and rainstorm intensity are analyzed separately. The results indicate that the negative ground lightning accounts for the 97.7 percent of the total ground lightning. Hourly evolution tendency of negative ground lightning frequency and total ground lightning frequency presents a two-peak one-valley structure. Positive flash frequency changes have a tri-peak two-valley trend. The ground lightning frequency of 6 min positive and negative flashes in the active negative lightning period displays a trend of multi-peak value. The peaks of positive ground lightning frequency is 12 min prior to negative ground lightning frequency peaks. The relationship of ground lightning and MCS shows that the negative ground lightning happening area is the convective cloud cluster development and strengthening area in the future. The densified locality of negative ground lightning frequency is situated in the concentrated TBB isoline area in front of the convective cloud cluster. The sharp increase of negative ground lightning frequency means MCS development by-and-by. Negative flash occurred mainly in the echo area whose strength is greater than 40 dBz, and positive lightning falls into both sides of strong echo center. During the rapid development of MCS, negative flash dense area is located in the forefront of single echo. In MCS stabilization period, negative flashes are concentrated near the center of the strong echo. The evolution relationship between the ground lightning and the heavy precipitation reveals that the occurrence and sharp growth of the ground lightning have very good indicative significance to the development and strengthening of the rainstorm. The occurrence of the first flash occurs ahead of the strong precipitation happening. The sharp increase of ground lightning has a close connection with the sudden increase of precipitation intensity. And the concentrated regions of the negative ground lightning may indicate the area where strong precipitation happens.
Based on the observation data of the lightning location system, temperature of blackbody brightness, Doppler radar echo and denser surface precipitation measurements from the process of a heavy rainstorm during 8-9 August 2007 in the Central Shaanxi Plain, the characteristics of ground lightning，and relationships of ground lightning, MCS, and rainstorm intensity are analyzed separately. The results indicate that the negative ground lightning accounts for the 97.7 percent of the total ground lightning. Hourly evolution tendency of negative ground lightning frequency and total ground lightning frequency presents a two-peak one-valley structure. Positive flash frequency changes have a tri-peak two-valley trend. The ground lightning frequency of 6 min positive and negative flashes in the active negative lightning period displays a trend of multi-peak value. The peaks of positive ground lightning frequency is 12 min prior to negative ground lightning frequency peaks. The relationship of ground lightning and MCS shows that the negative ground lightning happening area is the convective cloud cluster development and strengthening area in the future. The densified locality of negative ground lightning frequency is situated in the concentrated TBB isoline area in front of the convective cloud cluster. The sharp increase of negative ground lightning frequency means MCS development by-and-by. Negative flash occurred mainly in the echo area whose strength is greater than 40 dBz, and positive lightning falls into both sides of strong echo center. During the rapid development of MCS, negative flash dense area is located in the forefront of single echo. In MCS stabilization period, negative flashes are concentrated near the center of the strong echo. The evolution relationship between the ground lightning and the heavy precipitation reveals that the occurrence and sharp growth of the ground lightning have very good indicative significance to the development and strengthening of the rainstorm. The occurrence of the first flash occurs ahead of the strong precipitation happening. The sharp increase of ground lightning has a close connection with the sudden increase of precipitation intensity. And the concentrated regions of the negative ground lightning may indicate the area where strong precipitation happens.
2012, 38(1):66-71.
DOI: 10.7519/j.issn.1000-0526.2012.01.007
Abstract:
Based on the WSR 98D Doppler weather radar data and SAFIR 3000 lightning locating data， the relationship between lightning activity and radar echo characteristics of 14 thunderstorms in Beijing area is investigated. The studied period spans from 2006 to 2008 and focuses on the events with the most important lightning activity. It was found that the total lightning frequency has a strong linear correlation with the echo volume above -15℃ level with reflectivity exceeding 30 dBz. And the correlation coefficient is 0.89 . Its curve fitting value is 0.83. Furthermore, the echo volume per flash (VPF) has higher values in the beginning of lightning, while has lower values at the end of the period of lightning.
Based on the WSR 98D Doppler weather radar data and SAFIR 3000 lightning locating data， the relationship between lightning activity and radar echo characteristics of 14 thunderstorms in Beijing area is investigated. The studied period spans from 2006 to 2008 and focuses on the events with the most important lightning activity. It was found that the total lightning frequency has a strong linear correlation with the echo volume above -15℃ level with reflectivity exceeding 30 dBz. And the correlation coefficient is 0.89 . Its curve fitting value is 0.83. Furthermore, the echo volume per flash (VPF) has higher values in the beginning of lightning, while has lower values at the end of the period of lightning.
2012, 38(1):72-80.
DOI: 10.7519/j.issn.1000-0526.2012.01.008
Abstract:
On July 17, 2007, a major rainstorm occurred in the north slope of the Tianshan Mountains. The analysis results show that the circulation background of the rainstorm displays a twobody pattern of South Asia high and stabilization of low system in the middle of Asia. On the condition of steady stratification, the systematic ascending motion in the both sides of the Tianshan Mountains, the northern airflow in low levels, and the orographic uplift all augment rainstorm precipitation. The rainstorm area is corresponding to the cyclonic vortex column, with the vapor transported to the rainstorm area from Bay of Bengal through high-level southwesterly winds and lower northeasterly winds. There is a close relation between positive potential vorticity anomaly and the rainstorm.
On July 17, 2007, a major rainstorm occurred in the north slope of the Tianshan Mountains. The analysis results show that the circulation background of the rainstorm displays a twobody pattern of South Asia high and stabilization of low system in the middle of Asia. On the condition of steady stratification, the systematic ascending motion in the both sides of the Tianshan Mountains, the northern airflow in low levels, and the orographic uplift all augment rainstorm precipitation. The rainstorm area is corresponding to the cyclonic vortex column, with the vapor transported to the rainstorm area from Bay of Bengal through high-level southwesterly winds and lower northeasterly winds. There is a close relation between positive potential vorticity anomaly and the rainstorm.
2012, 38(1):81-89.
DOI: 10.7519/j.issn.1000-0526.2012.01.009
Abstract:
The terrain of Hubei Province is very complicated, and the loss of local heavy rainfall caused by terrain is serious. The heavy rainfall of Yichang region on 15 July 2010, is strengthened by landform effects, and occurred under a good background condition. Using the upper-air observation data, surface observation data, surface intensive observation data, the Doppler radar data and LAPS reanalysis data, the background field, surface layer air flows and radar echoes are analyzed. Research indicates that both the southward moving cold air and the strengthening subtropical high promote the adjustment of surface layer atmospheric wind fields, and the flow convergence effect on the local heavy rainfall results in a lagerscale rainfall event. There are two trigger actions by the terrain in this process, one is wind lifting in the upward side, and the other is the convergence of surface layer flow circulation.
The terrain of Hubei Province is very complicated, and the loss of local heavy rainfall caused by terrain is serious. The heavy rainfall of Yichang region on 15 July 2010, is strengthened by landform effects, and occurred under a good background condition. Using the upper-air observation data, surface observation data, surface intensive observation data, the Doppler radar data and LAPS reanalysis data, the background field, surface layer air flows and radar echoes are analyzed. Research indicates that both the southward moving cold air and the strengthening subtropical high promote the adjustment of surface layer atmospheric wind fields, and the flow convergence effect on the local heavy rainfall results in a lagerscale rainfall event. There are two trigger actions by the terrain in this process, one is wind lifting in the upward side, and the other is the convergence of surface layer flow circulation.
2012, 38(1):90-95.
DOI: 10.7519/j.issn.1000-0526.2012.01.010
Abstract:
A decrease in average annual total cloud cover was observed from 1960-2009, based on data from 606 meteorological stations in China. Specifically, the cloud cover in 1980-2009 was 0.6% less than that in the period 1960-1970. In coastal areas of China south of the Yangtze River, a stable variation in total cloud cover was observed, however, a significant difference was observed in the spatial variability of low clouds. In the Sichuan Basin during 1960-2009 the low-cloud cover has decreased by approximately 4.0% every decade since 1960. The situation is different in other regions of China. For example, south of the Yangtze River, east of Northeast China, and west of Xinjiang to the northern of Qinghai Tibetan Platean, low-cloud cover increases about 4.8% on average every decade since 1960.
A decrease in average annual total cloud cover was observed from 1960-2009, based on data from 606 meteorological stations in China. Specifically, the cloud cover in 1980-2009 was 0.6% less than that in the period 1960-1970. In coastal areas of China south of the Yangtze River, a stable variation in total cloud cover was observed, however, a significant difference was observed in the spatial variability of low clouds. In the Sichuan Basin during 1960-2009 the low-cloud cover has decreased by approximately 4.0% every decade since 1960. The situation is different in other regions of China. For example, south of the Yangtze River, east of Northeast China, and west of Xinjiang to the northern of Qinghai Tibetan Platean, low-cloud cover increases about 4.8% on average every decade since 1960.
2012, 38(1):96-102.
DOI: 10.7519/j.issn.1000-0526.2012.01.011
Abstract:
Based on 5 years’surface observation and sounding data in eastern China Region, a set of discrimination criterion is suggested after statistically analyzing temperature and thickness for different precipitation types. It is found that: Discrimination criterion in eastern China is different from that of western Europe because of climate factors； Applicability of North America’s criterion is not good to eastern China; Criterion combining temperature with thickness has a better behavior. The suggested criterion has a fairly good performance to rain and snow, with TS scores of 0.91 and 0.73 respectively. A compatible TS score of sleet can reach 0.57 too. With a FAR (false alarm ratio) of 0.70-0.80, the criterion for freezing rain (ice pellet) is not satisfying, only turns out a TS score of 0.25. This poor behavior is attributable to insufficiency of discrimination factors. Due to complex mechanism of freezing rain (ice pellet), more detailed vertical profile information and local climate factors must be taken into account when developing its discrimination criterion. And local forecasters’experience can still play an important role in forecasting this precipitation type. Results from this paper can be a good reference for operational work and numerical model post-process in eastern China.
Based on 5 years’surface observation and sounding data in eastern China Region, a set of discrimination criterion is suggested after statistically analyzing temperature and thickness for different precipitation types. It is found that: Discrimination criterion in eastern China is different from that of western Europe because of climate factors； Applicability of North America’s criterion is not good to eastern China; Criterion combining temperature with thickness has a better behavior. The suggested criterion has a fairly good performance to rain and snow, with TS scores of 0.91 and 0.73 respectively. A compatible TS score of sleet can reach 0.57 too. With a FAR (false alarm ratio) of 0.70-0.80, the criterion for freezing rain (ice pellet) is not satisfying, only turns out a TS score of 0.25. This poor behavior is attributable to insufficiency of discrimination factors. Due to complex mechanism of freezing rain (ice pellet), more detailed vertical profile information and local climate factors must be taken into account when developing its discrimination criterion. And local forecasters’experience can still play an important role in forecasting this precipitation type. Results from this paper can be a good reference for operational work and numerical model post-process in eastern China.
2012, 38(1):103-108.
DOI: 10.7519/j.issn.1000-0526.2012.01.012
Abstract:
Wire icing is an important influencing factor of power grid’s safety. It is of important directive significance for the risk division of wire icing and the feasibility demonstration of power gird construction to study the correlativity between wire icing and microrelief elements. The paper uses 1:50000 large-scale topographic maps and investigation data of wire icing disasters to study the correlativity of different microrelief elements and icing thickness, distinguish the microrelief elements which influence icing thickness remarkably and analyze quantitative relations between icing thickness and microrelief elements. Thus we obtain the sensitivity levels of the microrelief elements to different icing thickness range. The results show that, among the microrelief elements, the topographic roughness, altitude, distance from water body and land use type are the most significant elements which influence the icing thickness; the relationship of topographic roughness and design icing thickness is a power function; the relationship of altitude and design icing thickness is a logarithm function; the relationship of distance from water body and design icing thickness is a piecewise function, and the function relation of land use type and design icing thickness is not obvious. However, icing disaster is of obvious distribution configuration with land use type. While topographic roughness and altitude increase, icing thickness increases, its change rate and sensitivity descend; when topographic roughness is less than 40 m, it is the most sensitive to icing risk; when altitude is between 25-100 m, it is the most sensitive to icing risk; while distance from water body increases, icing thickness decreases after increasing trend, its change rate and sensitivity also decrease after increasing trend; when the distance is between 2-2.7 km, it is the most sensitive to icing risk. It is found that wire icing disasters mainly occur in water body, woodland, cultivated field and meadow, the sensitivity level of water body to icing risk is 1.5 times of woodland, 3.6 times of cultivated field, 16.7 times of meadow respectively.
Wire icing is an important influencing factor of power grid’s safety. It is of important directive significance for the risk division of wire icing and the feasibility demonstration of power gird construction to study the correlativity between wire icing and microrelief elements. The paper uses 1:50000 large-scale topographic maps and investigation data of wire icing disasters to study the correlativity of different microrelief elements and icing thickness, distinguish the microrelief elements which influence icing thickness remarkably and analyze quantitative relations between icing thickness and microrelief elements. Thus we obtain the sensitivity levels of the microrelief elements to different icing thickness range. The results show that, among the microrelief elements, the topographic roughness, altitude, distance from water body and land use type are the most significant elements which influence the icing thickness; the relationship of topographic roughness and design icing thickness is a power function; the relationship of altitude and design icing thickness is a logarithm function; the relationship of distance from water body and design icing thickness is a piecewise function, and the function relation of land use type and design icing thickness is not obvious. However, icing disaster is of obvious distribution configuration with land use type. While topographic roughness and altitude increase, icing thickness increases, its change rate and sensitivity descend; when topographic roughness is less than 40 m, it is the most sensitive to icing risk; when altitude is between 25-100 m, it is the most sensitive to icing risk; while distance from water body increases, icing thickness decreases after increasing trend, its change rate and sensitivity also decrease after increasing trend; when the distance is between 2-2.7 km, it is the most sensitive to icing risk. It is found that wire icing disasters mainly occur in water body, woodland, cultivated field and meadow, the sensitivity level of water body to icing risk is 1.5 times of woodland, 3.6 times of cultivated field, 16.7 times of meadow respectively.
2012, 38(1):109-117.
DOI: 10.7519/j.issn.1000-0526.2012.01.013
Abstract:
Frequent severe weather conditions and subsequent huge damages have risen many concerns in the meteorological services including a necessary evaluation of the current quality and level of services and the demands of customers. To develop quality improvement strategies and explore the market capacity for the meteorological services, this paper analyzed the survey data collected through the project “Research of Meteorological Service Performance Evaluation Methods and Technologies （MSPE）”, jointly funded by Ministry of Finance of People’s Republic of China and China Meteorological Administration. The project contained nearly 50000 records obtained from an internet survey and onsite questionnaire. First, some descriptive statistical methods are applied to the data to achieve enlightenment results. Then based on the contingent valuation method (CVM), the willingness to pay for the meteorological services is estimated, ranging from 7.36 to 20.58 billion Yuan per year. Further, regression analysis shows that variables including weather staff or not, education background, outdoor work time, monthly income, age and place of parental residence, are significant influential factors for the willingness to pay. However, gender and time span of residence are not significant variables.
Frequent severe weather conditions and subsequent huge damages have risen many concerns in the meteorological services including a necessary evaluation of the current quality and level of services and the demands of customers. To develop quality improvement strategies and explore the market capacity for the meteorological services, this paper analyzed the survey data collected through the project “Research of Meteorological Service Performance Evaluation Methods and Technologies （MSPE）”, jointly funded by Ministry of Finance of People’s Republic of China and China Meteorological Administration. The project contained nearly 50000 records obtained from an internet survey and onsite questionnaire. First, some descriptive statistical methods are applied to the data to achieve enlightenment results. Then based on the contingent valuation method (CVM), the willingness to pay for the meteorological services is estimated, ranging from 7.36 to 20.58 billion Yuan per year. Further, regression analysis shows that variables including weather staff or not, education background, outdoor work time, monthly income, age and place of parental residence, are significant influential factors for the willingness to pay. However, gender and time span of residence are not significant variables.
2012, 38(1):118-122.
DOI: 10.7519/j.issn.1000-0526.2012.01.014
Abstract:
The following are the main characteristics of the general circulation of atmosphere in October 2011. There were two polar vortex centers in the Northern Hemisphere. The circulation presents a fourwave pattern in middle-high latitudes. The intensity of the center of Atlantic and the east of Pacific deep trough is stronger than that of troughs in average conditions. The average temperature (10.6℃) is 1.0℃ higher than and the average precipitation (38.7 mm) is 1.7 mm more than compared the same time of normal years during October in 2011. There were four precipitation processes, two cold air processes and three heavy fog processes in the month.
The following are the main characteristics of the general circulation of atmosphere in October 2011. There were two polar vortex centers in the Northern Hemisphere. The circulation presents a fourwave pattern in middle-high latitudes. The intensity of the center of Atlantic and the east of Pacific deep trough is stronger than that of troughs in average conditions. The average temperature (10.6℃) is 1.0℃ higher than and the average precipitation (38.7 mm) is 1.7 mm more than compared the same time of normal years during October in 2011. There were four precipitation processes, two cold air processes and three heavy fog processes in the month.
2012, 38(1):123-128.
DOI: 10.7519/j.issn.1000-0526.2012.01.015
Abstract:
According to the position servo system working principle, fault phenomena and fault causes, the servo system maintenance work for a new generation of Zunyi Doppler weather radar is summarized as follows: (1) The orientation of the servo system in fault can be classified to five kinds of typical faults, and specific measures corresponding to maintenance are found out; (2) Position servo system has many components, distributed in many different places,thus repair work is difficult, the maintenance personnel have to master system composition and working principle, and then through graded judgment found out the fault location;(3) Oscilloscope and three-phase multimeter are mainly used in position servo system maintenance and inspection, thus technical personnel must be skilful in using; (4) From the occurrence of failure positions to see, faults are mainly concentrated in the position driving system, thus technical personnel have to master the azimuth drive principle, the inspection parameters of corresponding parts and the measured values, especially to remember some test waveforms.
According to the position servo system working principle, fault phenomena and fault causes, the servo system maintenance work for a new generation of Zunyi Doppler weather radar is summarized as follows: (1) The orientation of the servo system in fault can be classified to five kinds of typical faults, and specific measures corresponding to maintenance are found out; (2) Position servo system has many components, distributed in many different places,thus repair work is difficult, the maintenance personnel have to master system composition and working principle, and then through graded judgment found out the fault location;(3) Oscilloscope and three-phase multimeter are mainly used in position servo system maintenance and inspection, thus technical personnel must be skilful in using; (4) From the occurrence of failure positions to see, faults are mainly concentrated in the position driving system, thus technical personnel have to master the azimuth drive principle, the inspection parameters of corresponding parts and the measured values, especially to remember some test waveforms.
Mobile website
® 2024 All Rights Reserved
Supported by:Beijing E-Tiller Technology Development Co., Ltd.
ISSN:1000-0526 CN:11-2282/P