ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 42,Issue 12,2016 Table of Contents
2016, 42(12):1431-1444.
DOI: 10.7519/j.issn.1000-0526.2016.12.001
Abstract:
In this study, two heavy precipitation processes are simulated using the twomoment cloud microphysical scheme coupled with highresolution GRAPES model. The scheme is compared with WSM6 scheme, NCEP5 scheme and a variety of observation data to diagnose the prediction performance and analyze the key cloud microphysics process in deep convective precipitation. The simulation study shows that ice phase particles, especially graupel particles, play a leading role on the convection and precipitation in the deep convection clouds and the melting of graupel is the main source of heavy precipitation, while graupel distributes rarely in the stratiform precipitation region which is mainly affected by the melting of snow and warm cloud precipitation. The results derived from the twomoment scheme fit better with observations on rain belt direction, precipitation range and intensity. The scheme also has certain advantages on the maximum echo height and strength of convective cells, ice content distribution and cloud anvil structure. However, the ice content and echo height are slightly lower than observations. All these results would provide meaningful support for the improvement and operational application of the twomoment scheme.
In this study, two heavy precipitation processes are simulated using the twomoment cloud microphysical scheme coupled with highresolution GRAPES model. The scheme is compared with WSM6 scheme, NCEP5 scheme and a variety of observation data to diagnose the prediction performance and analyze the key cloud microphysics process in deep convective precipitation. The simulation study shows that ice phase particles, especially graupel particles, play a leading role on the convection and precipitation in the deep convection clouds and the melting of graupel is the main source of heavy precipitation, while graupel distributes rarely in the stratiform precipitation region which is mainly affected by the melting of snow and warm cloud precipitation. The results derived from the twomoment scheme fit better with observations on rain belt direction, precipitation range and intensity. The scheme also has certain advantages on the maximum echo height and strength of convective cells, ice content distribution and cloud anvil structure. However, the ice content and echo height are slightly lower than observations. All these results would provide meaningful support for the improvement and operational application of the twomoment scheme.
2016, 42(12):1445-1455.
DOI: 10.7519/j.issn.1000-0526.2016.12.002
Abstract:
Operational technologies in short and mediumrange weather forecast need further strengthening for the development of seamless and intensified weather forecast operational framework. Through reviewing present status of development, we find that, by the meteorological modernization during 2011-2015, the preliminary digitization for the technical flow in the short and mediumrange operational forecast has been developed in the national and some provincial operational units of China, including the numerical weather prediction system, the objective method application, the subjective editing and the downscaling gridded postprocessing. However, comparison with the developed countries shows that there are still some problems in the short and mediumrange operational technologies of China, such as lowerlevel development of numerical model, insufficiency of complete and indepth application of the objective technical method, lack of effective technology tools to support calibration of forecasters and the weak foundation of processing technique for gridding. Based on the review of present status of development and the analysis of current problems, suggestions are made that in the future development, the foundation role of the independent numerical model system should be enhanced, the objective techniques of forecast information extraction and calibration should be further developed, platform of subjective and objective blending techniques and tools should be developed greatly, and the development concepts of the downscaling gridded processing technique should be improved, followed by detailed exposition. Finally, ideas for reference are provided on four aspects, which are the basic data support for technical development, selection of the technical route, laws of technical development as well as exchange and sharing of techniques.
Operational technologies in short and mediumrange weather forecast need further strengthening for the development of seamless and intensified weather forecast operational framework. Through reviewing present status of development, we find that, by the meteorological modernization during 2011-2015, the preliminary digitization for the technical flow in the short and mediumrange operational forecast has been developed in the national and some provincial operational units of China, including the numerical weather prediction system, the objective method application, the subjective editing and the downscaling gridded postprocessing. However, comparison with the developed countries shows that there are still some problems in the short and mediumrange operational technologies of China, such as lowerlevel development of numerical model, insufficiency of complete and indepth application of the objective technical method, lack of effective technology tools to support calibration of forecasters and the weak foundation of processing technique for gridding. Based on the review of present status of development and the analysis of current problems, suggestions are made that in the future development, the foundation role of the independent numerical model system should be enhanced, the objective techniques of forecast information extraction and calibration should be further developed, platform of subjective and objective blending techniques and tools should be developed greatly, and the development concepts of the downscaling gridded processing technique should be improved, followed by detailed exposition. Finally, ideas for reference are provided on four aspects, which are the basic data support for technical development, selection of the technical route, laws of technical development as well as exchange and sharing of techniques.
2016, 42(12):1456-1464.
DOI: 10.7519/j.issn.1000-0526.2016.12.003
Abstract:
The contiguous rain area (CRA) is an objectoriented verification procedure. By setting a threshold for precipitation, the CRA is identified and isolated, and the forecast error of the rain area can be analyzed. This method can avoid the “double penalty” effect of traditional score method. The horizontal displacement is determined by translating the forecast rain field to the observation. This allows a decomposition of total error into components due to the rain location, amount and pattern. 119 CRAs from May to September in 2011-2014 over the east of Southwest China were found by using the CRA technique. Their location and intensity errors of the forecast by ECMWF model in 36 h were analyzed by the CRA verification method in this paper. Then these cases were classified into three types according to the weather systems, i.e., the low vortex and shear line over the east of Southwest China (the first type), the shear line located over Jianghuai Basin and the east of Southwest China (the second type), and the southerly wind type (the third type), respectively. The systematical error of each type was presented. The results showed that the pattern error for all CRAs is the greatest about 60% of the total error, then is the location error, about 30%, and the amount error is the least, about 10%. The average location error is 0.7° westward to observation, and the meridional displacement error is not clear. The mesoβscale rain area may fail to be forecasted by the model. However the horizontal scale larger than mesoβscale rain events would be overforecasted to have more rain area and total rainfall, but weaker intensity. The intensity error is similar to the first and the second types, in which the rain areas are overforecasted and the average rain intensity and maximum rainfall are underforecasted. However, the intensity is underforecasted or the event is missed for the third type. For the location error, it is westward for the first type, northwestward for the second type, and southwestward for the third type.
The contiguous rain area (CRA) is an objectoriented verification procedure. By setting a threshold for precipitation, the CRA is identified and isolated, and the forecast error of the rain area can be analyzed. This method can avoid the “double penalty” effect of traditional score method. The horizontal displacement is determined by translating the forecast rain field to the observation. This allows a decomposition of total error into components due to the rain location, amount and pattern. 119 CRAs from May to September in 2011-2014 over the east of Southwest China were found by using the CRA technique. Their location and intensity errors of the forecast by ECMWF model in 36 h were analyzed by the CRA verification method in this paper. Then these cases were classified into three types according to the weather systems, i.e., the low vortex and shear line over the east of Southwest China (the first type), the shear line located over Jianghuai Basin and the east of Southwest China (the second type), and the southerly wind type (the third type), respectively. The systematical error of each type was presented. The results showed that the pattern error for all CRAs is the greatest about 60% of the total error, then is the location error, about 30%, and the amount error is the least, about 10%. The average location error is 0.7° westward to observation, and the meridional displacement error is not clear. The mesoβscale rain area may fail to be forecasted by the model. However the horizontal scale larger than mesoβscale rain events would be overforecasted to have more rain area and total rainfall, but weaker intensity. The intensity error is similar to the first and the second types, in which the rain areas are overforecasted and the average rain intensity and maximum rainfall are underforecasted. However, the intensity is underforecasted or the event is missed for the third type. For the location error, it is westward for the first type, northwestward for the second type, and southwestward for the third type.
2016, 42(12):1465-1475.
DOI: 10.7519/j.issn.1000-0526.2016.12.004
Abstract:
Based on several rainstorm processes of landed typhoons in 2013-2015 and statistics, we propose a realtime correction method for typhoon rainstorm forecast (also called ensemble member optimization method) using ECMWF precipitation and typhoon track ensemble forecasts and operational positioning of National Meteorological Certre (NMC) for the operational track forecast. The results show that ensemble statistic precipitation products are improved significantly by using the ensemble member optimization method, and the improved products give better performances than the ECMWF deterministic forecasts. Improvements of ensemble statistic products for shortrange forecast are more significant than mediumrange forecast, and that for extra torrential rain forecast are more significant than torrential and heavy rain forecast. Moreover, Fuse Matching average (FM) product is proposed in this paper, based on the characteristics and principles of Probability Matching average (PM) and fusing products. The results also show that the PM products with 10 to 15 optimal selected members give the best performance for 36 h forecast, while the threat scores of PM products can be promoted by 10% approximately for extra torrential rain forecasts. For 60 h and 84 h extra torrential rain forecasts, the threat scores of FM products can be promoted by above 20%, compared with the ECMWF deterministic forecasts.
Based on several rainstorm processes of landed typhoons in 2013-2015 and statistics, we propose a realtime correction method for typhoon rainstorm forecast (also called ensemble member optimization method) using ECMWF precipitation and typhoon track ensemble forecasts and operational positioning of National Meteorological Certre (NMC) for the operational track forecast. The results show that ensemble statistic precipitation products are improved significantly by using the ensemble member optimization method, and the improved products give better performances than the ECMWF deterministic forecasts. Improvements of ensemble statistic products for shortrange forecast are more significant than mediumrange forecast, and that for extra torrential rain forecast are more significant than torrential and heavy rain forecast. Moreover, Fuse Matching average (FM) product is proposed in this paper, based on the characteristics and principles of Probability Matching average (PM) and fusing products. The results also show that the PM products with 10 to 15 optimal selected members give the best performance for 36 h forecast, while the threat scores of PM products can be promoted by 10% approximately for extra torrential rain forecasts. For 60 h and 84 h extra torrential rain forecasts, the threat scores of FM products can be promoted by above 20%, compared with the ECMWF deterministic forecasts.
2016, 42(12):1476-1482.
DOI: 10.7519/j.issn.1000-0526.2016.12.005
Abstract:
A statelevel gridded quantitative precipitation forecasting system has been built by using the fusion of subjective and objective precipitation inversion, precipitation statistical downscaling, time split method and other techniques. The technical structure of this system is reasonable, and its module features a clear division. It has been put into meteorological operation in the National Meteorological Center, China Meteorological Administration since June 2014, being able to generate gridded quantitative precipitation forecast products with forecast time length of 0-168 h, 10 km resolution and 3 h interval. The gridded precipitation forecast of the 13th tropical cyclone “Soudelor” in 2015 is tested and the results show that, compared to the deterministic model forecasts of the European Centre for MediumRange Weather Forecast (ECMWF) and the subjective forecasts, this forecast can better reflect the spatiotemporal distribution of typhoon precipitation, and more accurately express the severe rainstorm center in northeast of Fujian and southeast of Zhejiang. The overall effect of the gridded forecasts from April to September 2015 is verified. The results indicate that, compared to the deterministic model forecasts of the ECMWF and the forecasters’ subjective forecasts after inversedistance objective analysis, the forecast products can maintain the same predictive accuracy as subjective forecasts, and meanwhile can obviously improve the degree of spatiotemporal precision of precipitation forecasts.
A statelevel gridded quantitative precipitation forecasting system has been built by using the fusion of subjective and objective precipitation inversion, precipitation statistical downscaling, time split method and other techniques. The technical structure of this system is reasonable, and its module features a clear division. It has been put into meteorological operation in the National Meteorological Center, China Meteorological Administration since June 2014, being able to generate gridded quantitative precipitation forecast products with forecast time length of 0-168 h, 10 km resolution and 3 h interval. The gridded precipitation forecast of the 13th tropical cyclone “Soudelor” in 2015 is tested and the results show that, compared to the deterministic model forecasts of the European Centre for MediumRange Weather Forecast (ECMWF) and the subjective forecasts, this forecast can better reflect the spatiotemporal distribution of typhoon precipitation, and more accurately express the severe rainstorm center in northeast of Fujian and southeast of Zhejiang. The overall effect of the gridded forecasts from April to September 2015 is verified. The results indicate that, compared to the deterministic model forecasts of the ECMWF and the forecasters’ subjective forecasts after inversedistance objective analysis, the forecast products can maintain the same predictive accuracy as subjective forecasts, and meanwhile can obviously improve the degree of spatiotemporal precision of precipitation forecasts.
2016, 42(12):1483-1497.
DOI: 10.7519/j.issn.1000-0526.2016.12.006
Abstract:
Modifying trend (MD) analysis for different forecasts at same valid time is a method to estimate the forecast error and calibrate the forecast. To verify the validation of this method, intensity and position index of the westerly wind trough (WWT) and area index, intensity index, west ridge point and north edge index of the subtropical high (sTH) of northwest Pacific Ocean are defined. Using the 500 hPa geopotential height forecast dataset from April 2011 to September 2015, the correlation and consistency of intensity and position MDs of sTH and WWT at different positions around China produced by ECMWF （EC） and T639 models are analyzed and compared. The results show that there are systematic biases for EC and T639 sTH forecast and the WWTs are nearly bias free. The systematic biases of T639 are larger than that of EC. As the lead times are prolonged, the sTH eastward systematic biases of west ridge points and decreasing intensity and area systematic biases are enlarged. The west ridge point, intensity and area of sTH show no significant correlations among the MDs of different lead times and the MDs are not consistent for EC and T639. The forecast error and MD characteristics of sTH are different as the west ridge points are located at different longitudes. As the west ridge point moves from the east Indian Ocean to the northwest Pacific Ocean east of Philippines Islands, the sTH forecast errores and systematic biases decrease. In different longitude ranges there is no significant correlation among MDs of different lead times and their covariances are negative, which means the MDs are inconsistent. For the WWT, EC and T639 models both show that the errors of WWT in high latitudes are larger than that in low latitudes and the errors of WWT intensity are small. The errors of T639 are significantly larger than that of EC. The covariances among MDs of different lead times are negative too, which means that the WWTs position MDs are not consistent for EC and T639 as well. The correlatons among MDs of different periods are nearly 0, which means that the upgrades of EC and T639 models do not have any effects on the inconsistency of MDs.
Modifying trend (MD) analysis for different forecasts at same valid time is a method to estimate the forecast error and calibrate the forecast. To verify the validation of this method, intensity and position index of the westerly wind trough (WWT) and area index, intensity index, west ridge point and north edge index of the subtropical high (sTH) of northwest Pacific Ocean are defined. Using the 500 hPa geopotential height forecast dataset from April 2011 to September 2015, the correlation and consistency of intensity and position MDs of sTH and WWT at different positions around China produced by ECMWF （EC） and T639 models are analyzed and compared. The results show that there are systematic biases for EC and T639 sTH forecast and the WWTs are nearly bias free. The systematic biases of T639 are larger than that of EC. As the lead times are prolonged, the sTH eastward systematic biases of west ridge points and decreasing intensity and area systematic biases are enlarged. The west ridge point, intensity and area of sTH show no significant correlations among the MDs of different lead times and the MDs are not consistent for EC and T639. The forecast error and MD characteristics of sTH are different as the west ridge points are located at different longitudes. As the west ridge point moves from the east Indian Ocean to the northwest Pacific Ocean east of Philippines Islands, the sTH forecast errores and systematic biases decrease. In different longitude ranges there is no significant correlation among MDs of different lead times and their covariances are negative, which means the MDs are inconsistent. For the WWT, EC and T639 models both show that the errors of WWT in high latitudes are larger than that in low latitudes and the errors of WWT intensity are small. The errors of T639 are significantly larger than that of EC. The covariances among MDs of different lead times are negative too, which means that the WWTs position MDs are not consistent for EC and T639 as well. The correlatons among MDs of different periods are nearly 0, which means that the upgrades of EC and T639 models do not have any effects on the inconsistency of MDs.
2016, 42(12):1498-1505.
DOI: 10.7519/j.issn.1000-0526.2016.12.007
Abstract:
Faced with a series of limitations in developing numerical weather prediction model, a brand new conception of forecaster data assimilation (DA) has been put forward. That is an organic combination between weather forecasters’ irreplaceable ability and numerical weather prediction. The improvement on the model initial field by manual correction of potential vorticity is coincident with this conception. By utilizing the principle of correspondence between potential vorticity (PV) and water vapor image (WV) observed by satellite, forecasters can exam the model and manually correct the distribution of PV, and use PV inversion to obtain a well developed model initial field. This technology has been proved efficacious in operational work in some countries. This study takes use of the principles mentioned above to achieve the whole technology and use some experimental results to show the technical processes.
Faced with a series of limitations in developing numerical weather prediction model, a brand new conception of forecaster data assimilation (DA) has been put forward. That is an organic combination between weather forecasters’ irreplaceable ability and numerical weather prediction. The improvement on the model initial field by manual correction of potential vorticity is coincident with this conception. By utilizing the principle of correspondence between potential vorticity (PV) and water vapor image (WV) observed by satellite, forecasters can exam the model and manually correct the distribution of PV, and use PV inversion to obtain a well developed model initial field. This technology has been proved efficacious in operational work in some countries. This study takes use of the principles mentioned above to achieve the whole technology and use some experimental results to show the technical processes.
2016, 42(12):1506-1512.
DOI: 10.7519/j.issn.1000-0526.2016.12.008
Abstract:
The correlation between environment forecast fields and track forecast errors of typhoons in Northwestern Pacific Ocean and South China Sea was analyzed by using the output data in 2009 and 2010 from T639, which is the global spectrum model of National Meteorological Centre, and the best track data from Shanghai Typhoon Institute of CMA. With regression method, a linear track error estimate model was built for the T639 typhoon track forecast errors at lead time from 24 h to 120 h with whole layer vertical shear of environment and typhoon circulation intensity at 400 hPa (with samples of 299, 232, 170, 117 and 84, respectively). The estimate model was examined with the data in 2011 (with samples of 182, 146, 117, 85 and 61, respectively). The preliminary results illustrated that the typhoon track forecast error is positively correlated to ambient vertical wind shear, but being negative correlation with typhoon circulation intensity in each layer, which is most obvious at 400 hPa. The linear prediction model built with the whole layer vertical shear and typhoon circulation intensity at 400 hPa is able to perform estimation to track errors qualitatively, with a preferable result for the 24 h lead time forecast.
The correlation between environment forecast fields and track forecast errors of typhoons in Northwestern Pacific Ocean and South China Sea was analyzed by using the output data in 2009 and 2010 from T639, which is the global spectrum model of National Meteorological Centre, and the best track data from Shanghai Typhoon Institute of CMA. With regression method, a linear track error estimate model was built for the T639 typhoon track forecast errors at lead time from 24 h to 120 h with whole layer vertical shear of environment and typhoon circulation intensity at 400 hPa (with samples of 299, 232, 170, 117 and 84, respectively). The estimate model was examined with the data in 2011 (with samples of 182, 146, 117, 85 and 61, respectively). The preliminary results illustrated that the typhoon track forecast error is positively correlated to ambient vertical wind shear, but being negative correlation with typhoon circulation intensity in each layer, which is most obvious at 400 hPa. The linear prediction model built with the whole layer vertical shear and typhoon circulation intensity at 400 hPa is able to perform estimation to track errors qualitatively, with a preferable result for the 24 h lead time forecast.
2016, 42(12):1513-1521.
DOI: 10.7519/j.issn.1000-0526.2016.12.009
Abstract:
This study analyzed the climatic features and environmental parameters of severe thunderstorm gales (≥25 m·s-1) in China in 2004-2013. The results show that severe thunderstorm gales are seen mainly in the eastern part of China. Beginning from March the gales blow in the southwest and southeast of China, then moving northward to the central and eastern part in April and continuously to the northern, northeastern and northwestern parts in May. The peak values of severe thunderstorm gales appear at different times in different regions and there are two peaks in the central and eastern parts of China. Severe thunderstorm gales have medium vertical wind shears, 10.2 m·s-1 from surface to 700 hPa, and 14.3 m·s-1 from surface to 500 hPa, which are lower than the average values in America. The relative dry layers exist obviously in the middle level. The average difference between temperature and dew point temperature at 500 hPa is greater than 10 ℃, while the layers from 3 km to 7 km are dry in the northern and northeastern part of China. According to the infrared satellite images, the most common severe thunderstorm gales are mostly along with cluster clouds, and secondly line clouds. Besides, there are some single convective clouds and the major cloud patterns are different in different regions. By analyzing the environmental parameters of three different cloud patterns in East China where severe thunderstorm gales are seen often, we found that, in the case of the cluster clouds, the CAPE values of the severe gales are large with humidity high in low level but low in middle level, and also with high lapse rate. In comparison, for the line cloud pattern the thermodynamic parameters are smaller, but the values of lowlevel and deep vertical wind shears are large and the whole layer is dry. The values of humidity and temperature in low level for the single convective cloud pattern are large and the ambient vertical wind shears are smaller.
This study analyzed the climatic features and environmental parameters of severe thunderstorm gales (≥25 m·s-1) in China in 2004-2013. The results show that severe thunderstorm gales are seen mainly in the eastern part of China. Beginning from March the gales blow in the southwest and southeast of China, then moving northward to the central and eastern part in April and continuously to the northern, northeastern and northwestern parts in May. The peak values of severe thunderstorm gales appear at different times in different regions and there are two peaks in the central and eastern parts of China. Severe thunderstorm gales have medium vertical wind shears, 10.2 m·s-1 from surface to 700 hPa, and 14.3 m·s-1 from surface to 500 hPa, which are lower than the average values in America. The relative dry layers exist obviously in the middle level. The average difference between temperature and dew point temperature at 500 hPa is greater than 10 ℃, while the layers from 3 km to 7 km are dry in the northern and northeastern part of China. According to the infrared satellite images, the most common severe thunderstorm gales are mostly along with cluster clouds, and secondly line clouds. Besides, there are some single convective clouds and the major cloud patterns are different in different regions. By analyzing the environmental parameters of three different cloud patterns in East China where severe thunderstorm gales are seen often, we found that, in the case of the cluster clouds, the CAPE values of the severe gales are large with humidity high in low level but low in middle level, and also with high lapse rate. In comparison, for the line cloud pattern the thermodynamic parameters are smaller, but the values of lowlevel and deep vertical wind shears are large and the whole layer is dry. The values of humidity and temperature in low level for the single convective cloud pattern are large and the ambient vertical wind shears are smaller.
2016, 42(12):1522-1530.
DOI: 10.7519/j.issn.1000-0526.2016.12.010
Abstract:
Estimation methods of extreme wind speed and turbulence intensity parameters for wind turbine classes recommended by IEC 614001 Ed.3: Wind turbines Part 1: Design Requirements are widely used in wind energy because of its simple and convenient features. Based on the observation data from 193 masts in the professional observation network of wind energy resource in China, we compare the extreme 10 min average wind speeds within a recurrence period of 50 years (V50) by IEC method and extremum Ⅰ distribution which is recommended in China, and obtain the following findings. First of all, there are only 7 masts where the values of V50 by the two methods is relatively consistent within ±1% deviation. Values of V50 by IEC method are generally smaller, and there are 121 masts with V50 lower than -10% and 44 masts with the value lower than -30%, while only 9 masts have the value higher than +10% all around the country. After that, masts with much smaller V50 by IEC method are mainly distributed in southeastern coastal areas affected by typhoon, while masts with small deviations are mainly distributed in the regions with flat terrain in the Northwest and North China, and the masts with deviation over 10% are also concentrated right here. Finally, 46 masts will go into errors if they are calculated only by characteristic indices of the mean turbulence intensity in 15 m·s-1 wind speed, compared to results by the 90% quantile for 15 m·s-1 wind speed.
Estimation methods of extreme wind speed and turbulence intensity parameters for wind turbine classes recommended by IEC 614001 Ed.3: Wind turbines Part 1: Design Requirements are widely used in wind energy because of its simple and convenient features. Based on the observation data from 193 masts in the professional observation network of wind energy resource in China, we compare the extreme 10 min average wind speeds within a recurrence period of 50 years (V50) by IEC method and extremum Ⅰ distribution which is recommended in China, and obtain the following findings. First of all, there are only 7 masts where the values of V50 by the two methods is relatively consistent within ±1% deviation. Values of V50 by IEC method are generally smaller, and there are 121 masts with V50 lower than -10% and 44 masts with the value lower than -30%, while only 9 masts have the value higher than +10% all around the country. After that, masts with much smaller V50 by IEC method are mainly distributed in southeastern coastal areas affected by typhoon, while masts with small deviations are mainly distributed in the regions with flat terrain in the Northwest and North China, and the masts with deviation over 10% are also concentrated right here. Finally, 46 masts will go into errors if they are calculated only by characteristic indices of the mean turbulence intensity in 15 m·s-1 wind speed, compared to results by the 90% quantile for 15 m·s-1 wind speed.
2016, 42(12):1531-1539.
DOI: 10.7519/j.issn.1000-0526.2016.12.011
Abstract:
Based on the relationship between the sea surface roughness (z0) and the 10 m wind speed, a method is developed for the 10 m wind speed in this paper. By comparing with the ERAInterim wind speed, a very good correlation is obtained. And the wind speed calculated by this method is closer to the ERAInterim wind speed than the speed by the fixed z0 method. Based on this dynamic z0 method, the data from two weather stations on the offshore oil platform in the South China Sea is used to calculate the hourly 10 m wind speed and the corresponding dynamic roughness length for nearly four years. The analysis reveals the wind speed ranges mainly within 3-13 m·s-1. The average wind speed is smaller from April to September and larger from October to March. The daily variation of wind speed has the following characteristics in 14:00-17:00 BT, the wind speed is at the minimum and in 06:00-09:00 BT, the wind speed reaches the maximum. In addition, there is significant seasonal variation and daily variation of z0 value which is consistent with the variation of wind speed. The variation of meteorological elements is analyzed when the center of Vicente passed the station, and the result shows that the corrected wind speed and z0 are in accord with the actual observation values.
Based on the relationship between the sea surface roughness (z0) and the 10 m wind speed, a method is developed for the 10 m wind speed in this paper. By comparing with the ERAInterim wind speed, a very good correlation is obtained. And the wind speed calculated by this method is closer to the ERAInterim wind speed than the speed by the fixed z0 method. Based on this dynamic z0 method, the data from two weather stations on the offshore oil platform in the South China Sea is used to calculate the hourly 10 m wind speed and the corresponding dynamic roughness length for nearly four years. The analysis reveals the wind speed ranges mainly within 3-13 m·s-1. The average wind speed is smaller from April to September and larger from October to March. The daily variation of wind speed has the following characteristics in 14:00-17:00 BT, the wind speed is at the minimum and in 06:00-09:00 BT, the wind speed reaches the maximum. In addition, there is significant seasonal variation and daily variation of z0 value which is consistent with the variation of wind speed. The variation of meteorological elements is analyzed when the center of Vicente passed the station, and the result shows that the corrected wind speed and z0 are in accord with the actual observation values.
2016, 42(12):1540-1546.
DOI: 10.7519/j.issn.1000-0526.2016.12.012
Abstract:
Continuous observation was made with the help of ceilometers on the sanddust weather processes in Beijing in the spring of 2015. By using the observation data and the conventional ground meteorological elements, visibility and the changes of PM10 particulate mass concentration, this paper analyzes the spatiotemporal distribution characteristics of aerosol backscatter coefficients in the three weather phenomena of floating dust, blowing sand and dust storm during the two sanddust weather processes. In addition, the paper conducts the correlation analysis on the backscatter coefficient of ceilometers and the PM10 particulate mass concentration as well. The results indicate that ceilometers have the ability of monitoring the vertical distribution of aerosol particles. During the process of blowing sand and dust storm, backscatter coefficient decreases with the increase of height. What’s more, the correlation coefficients between the backscatter coefficient and PM10 particulate mass concentration at the height of 10 m, 50 m and 100 m are all above 0.82.
Continuous observation was made with the help of ceilometers on the sanddust weather processes in Beijing in the spring of 2015. By using the observation data and the conventional ground meteorological elements, visibility and the changes of PM10 particulate mass concentration, this paper analyzes the spatiotemporal distribution characteristics of aerosol backscatter coefficients in the three weather phenomena of floating dust, blowing sand and dust storm during the two sanddust weather processes. In addition, the paper conducts the correlation analysis on the backscatter coefficient of ceilometers and the PM10 particulate mass concentration as well. The results indicate that ceilometers have the ability of monitoring the vertical distribution of aerosol particles. During the process of blowing sand and dust storm, backscatter coefficient decreases with the increase of height. What’s more, the correlation coefficients between the backscatter coefficient and PM10 particulate mass concentration at the height of 10 m, 50 m and 100 m are all above 0.82.
2016, 42(12):1547-1553.
DOI: 10.7519/j.issn.1000-0526.2016.12.013
Abstract:
Wet bulb temperature is an important parameter in some largescale engineering design and safety, and a key factor in investment costs and operational effectiveness. Since wet bulb temperature observation stopped, it is pretty important to solve how to get more accurate data and study the continuity. Therefore, based on the hourly and timing data of 70 stations in Jiangsu Province, the Newton iterative method and the best approximation method are used to study the variance calculation and data continuous application. The best approximation method is better with high accuracy, and good compliance rate (90.8%-100%), which is far higher than that of the Newton iterative method (12.7%-20.1%). And the results present an obvious diurnal variation that the coincidence rate is the higher during 09:00-20:00 BT, but lower before and after sunrise. The analysis of the 40year series shows that the calculation results of the best approximation have a good stability, and to a certain extent, could replace the observed value. The effect is better when temperature is high and vice versa. Compared with the heterogeneity in the decade data, research on the continuity of the wet bulb temperature data is more reliable.
Wet bulb temperature is an important parameter in some largescale engineering design and safety, and a key factor in investment costs and operational effectiveness. Since wet bulb temperature observation stopped, it is pretty important to solve how to get more accurate data and study the continuity. Therefore, based on the hourly and timing data of 70 stations in Jiangsu Province, the Newton iterative method and the best approximation method are used to study the variance calculation and data continuous application. The best approximation method is better with high accuracy, and good compliance rate (90.8%-100%), which is far higher than that of the Newton iterative method (12.7%-20.1%). And the results present an obvious diurnal variation that the coincidence rate is the higher during 09:00-20:00 BT, but lower before and after sunrise. The analysis of the 40year series shows that the calculation results of the best approximation have a good stability, and to a certain extent, could replace the observed value. The effect is better when temperature is high and vice versa. Compared with the heterogeneity in the decade data, research on the continuity of the wet bulb temperature data is more reliable.
2016, 42(12):1554-1559.
DOI: 10.7519/j.issn.1000-0526.2016.12.014
Abstract:
In this paper, sugarcane observation data and meteorological data of five agrometeorological experimental stations in Guangxi are used to analyze the growth and development characteristics of ratooning cane, meteorological condition differences in different growing stages and its relationship with sugarcane’s growth and development. The results show that: (1) From 2000 to 2011, the emergence date of ratooning cane delays about 2.5 d·a-1; the duration from emergence to stem elongation shortens about 2.9 d·a-1 and 2.7 d·a-1 for the whole growing period; interannual fluctuation of duration from emergence to stem elongation is bigger than the period from stem elongation to maturity, about 15 d (16%) and 4 d (3%) respectively; the maximum stalk height increases about 5.3 cm·a-1 and single stem fresh weight increases about 64.4 g·a-1. (2) Relative humidity of the whole growth period declines about 0.38% every year; sunshine hours in the emergence to stem elongation stage descends 10 h·a-1. For each stage, the interannual variation of minimum temperature and precipitation is big while that of mean temperature and relative humidity is small. The variation of meteorological factors from emergence to stem elongation is higher than those from stem elongation to maturity and in the whole growing period. (3) Rising temperature shortens the ratooning sugarcane growing period obviously, but there is no significant relationship between the highest temperature, lowest temperature, mean temperature and the largest stem height, fresh weight. Effect of precipitation on ratooning sugarcane is very significant in the emergence to stem elongation stage and the whole growth stage except the stem elongation to maturity stage. The effect prolonged or shortened sunshine hours during each growth stage is not obvious. However, in the emergence to stem elongation stage, the reduction of sunshine hours is more favorable for the growth of ratooning sugarcane because the environment becomes wetter.
In this paper, sugarcane observation data and meteorological data of five agrometeorological experimental stations in Guangxi are used to analyze the growth and development characteristics of ratooning cane, meteorological condition differences in different growing stages and its relationship with sugarcane’s growth and development. The results show that: (1) From 2000 to 2011, the emergence date of ratooning cane delays about 2.5 d·a-1; the duration from emergence to stem elongation shortens about 2.9 d·a-1 and 2.7 d·a-1 for the whole growing period; interannual fluctuation of duration from emergence to stem elongation is bigger than the period from stem elongation to maturity, about 15 d (16%) and 4 d (3%) respectively; the maximum stalk height increases about 5.3 cm·a-1 and single stem fresh weight increases about 64.4 g·a-1. (2) Relative humidity of the whole growth period declines about 0.38% every year; sunshine hours in the emergence to stem elongation stage descends 10 h·a-1. For each stage, the interannual variation of minimum temperature and precipitation is big while that of mean temperature and relative humidity is small. The variation of meteorological factors from emergence to stem elongation is higher than those from stem elongation to maturity and in the whole growing period. (3) Rising temperature shortens the ratooning sugarcane growing period obviously, but there is no significant relationship between the highest temperature, lowest temperature, mean temperature and the largest stem height, fresh weight. Effect of precipitation on ratooning sugarcane is very significant in the emergence to stem elongation stage and the whole growth stage except the stem elongation to maturity stage. The effect prolonged or shortened sunshine hours during each growth stage is not obvious. However, in the emergence to stem elongation stage, the reduction of sunshine hours is more favorable for the growth of ratooning sugarcane because the environment becomes wetter.
2016, 42(12):1560-1566.
DOI: 10.7519/j.issn.1000-0526.2016.12.015
Abstract:
The main characteristics of the general circulation in September 2016 are as follows. The polar vortex of the Northern Hemisphere presented a single pattern with stronger intensity. In the midhigh latitudes of Eurasia, the circulation presented a twotrough and oneridge pattern. The subtropical high in Northwestern Pacific lay westward and northward, and its intensity was stronger than its average state during the corresponding time of the normal years. Meanwhile, the monthly mean precipitation amount is 78.9 mm, which is more than its normal value (65.3 mm) by 20.8%. The monthly mean temperature is 17.7℃, 1.1℃ higher than its climatological mean (16.6℃), which is recorded as the second high value since 1961. Three regional severe precipitation events happened in September, two of which were caused by tropical cyclones or typhoons. In September, seven tropical cyclones were generated over the Pacific and the South China Sea, and Typhoon Meranti (1614) and Megi (1617) made landfall over Fujian Province, China, carrying continuous heavy rains to many places. Sichuan Province and Yunnan Province received autumn rain notably so that serious flood disasters occurred in some locations. In addition, the drought condition in the southern part of Huanghuai Region and northwestern part of Hubei Province got relieved.
The main characteristics of the general circulation in September 2016 are as follows. The polar vortex of the Northern Hemisphere presented a single pattern with stronger intensity. In the midhigh latitudes of Eurasia, the circulation presented a twotrough and oneridge pattern. The subtropical high in Northwestern Pacific lay westward and northward, and its intensity was stronger than its average state during the corresponding time of the normal years. Meanwhile, the monthly mean precipitation amount is 78.9 mm, which is more than its normal value (65.3 mm) by 20.8%. The monthly mean temperature is 17.7℃, 1.1℃ higher than its climatological mean (16.6℃), which is recorded as the second high value since 1961. Three regional severe precipitation events happened in September, two of which were caused by tropical cyclones or typhoons. In September, seven tropical cyclones were generated over the Pacific and the South China Sea, and Typhoon Meranti (1614) and Megi (1617) made landfall over Fujian Province, China, carrying continuous heavy rains to many places. Sichuan Province and Yunnan Province received autumn rain notably so that serious flood disasters occurred in some locations. In addition, the drought condition in the southern part of Huanghuai Region and northwestern part of Hubei Province got relieved.
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