ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 40,Issue 2,2014 Table of Contents
2014, 40(2):133-145.
DOI: 10.7519/j.issn.1000-0526.2014.02.001
Abstract:
By using the NCEP reanalysis data, the vapor budget of the area covered by the severe torrential rain over the northeast of North China on 21 July, 2012 is calculated according to the vapor budget equation. The results show that meridional water vapor transportation is dominant while the extremely heavy rain hits Beijing Region, where most moist vapor comes from the southern boundary below 500 hPa. The low level regional moisture convergence is consistent with the time and space when the torrential rain breaks out and develops. Above the middle level the vertical vapor transport is more prominent. Then the variation features of the vapor transport corridors and their moisture contributions are got through the HYSPLIT mode. The backward trajectory analyses illustrate two major vapor transport corridors. The moistest vapor derived from Yellow Sea and East China Sea along the low level make the main moisture contribution during the heavy precipitation. Moisture from the South China Sea and the Bay of Bengal strengthens the water vapor in the region when the heavy rain starts and develops. Also the drier vapor corridor along the high level from the northwest of China plays an important role in this case.
By using the NCEP reanalysis data, the vapor budget of the area covered by the severe torrential rain over the northeast of North China on 21 July, 2012 is calculated according to the vapor budget equation. The results show that meridional water vapor transportation is dominant while the extremely heavy rain hits Beijing Region, where most moist vapor comes from the southern boundary below 500 hPa. The low level regional moisture convergence is consistent with the time and space when the torrential rain breaks out and develops. Above the middle level the vertical vapor transport is more prominent. Then the variation features of the vapor transport corridors and their moisture contributions are got through the HYSPLIT mode. The backward trajectory analyses illustrate two major vapor transport corridors. The moistest vapor derived from Yellow Sea and East China Sea along the low level make the main moisture contribution during the heavy precipitation. Moisture from the South China Sea and the Bay of Bengal strengthens the water vapor in the region when the heavy rain starts and develops. Also the drier vapor corridor along the high level from the northwest of China plays an important role in this case.
2 Sensitivity Simulation of Heavy Rainfall to Land Surface Characteristics and Ensemble Forecast Test
2014, 40(2):146-157.
DOI: 10.7519/j.issn.1000-0526.2014.02.002
Abstract:
The simulation of a heavy rainfall event that occurred in the middle and lower reaches of Yangtze River was conducted to examine the effects of perturbations of land surface variables (soil moisture and soil temperature) and land surface parameter (vegetation fraction) in the ensemble forecast using the Weather Research and Forecasting Model (WRF) Version 3.2.1 and National Centers for Environmental Prediction (NCEP) reanalysis data. The results showed that land surface variable (or parameter) perturbations have a large impact on short term simulation of rainstorm. The time scale that the land surface variable (or parameter) perturbation affects precipitation is lower than 10 h and the smallest time scale is lower than 6 h. From the point of influence mechanism, disturbance of the land surface variables (parameters) changes the surface latent heat flux and sensible heat flux firstly, which has great impact on the local atmospheric temperature, pressure, humidity and wind field by the land atmosphere interaction, and thus affects the intensity and distribution of the heavy rainfall. The ensemble average result is better than the control forecast, which is more stable and credible than the single ensemble members. The analysis of the precipitation probability forecast can provide some useful information about the precipitation forecast especially to heavy rainfall. Overall, the initial perturbation of land surface variables and land surface parameter perturbations are significant to the initial ensemble forecast.
The simulation of a heavy rainfall event that occurred in the middle and lower reaches of Yangtze River was conducted to examine the effects of perturbations of land surface variables (soil moisture and soil temperature) and land surface parameter (vegetation fraction) in the ensemble forecast using the Weather Research and Forecasting Model (WRF) Version 3.2.1 and National Centers for Environmental Prediction (NCEP) reanalysis data. The results showed that land surface variable (or parameter) perturbations have a large impact on short term simulation of rainstorm. The time scale that the land surface variable (or parameter) perturbation affects precipitation is lower than 10 h and the smallest time scale is lower than 6 h. From the point of influence mechanism, disturbance of the land surface variables (parameters) changes the surface latent heat flux and sensible heat flux firstly, which has great impact on the local atmospheric temperature, pressure, humidity and wind field by the land atmosphere interaction, and thus affects the intensity and distribution of the heavy rainfall. The ensemble average result is better than the control forecast, which is more stable and credible than the single ensemble members. The analysis of the precipitation probability forecast can provide some useful information about the precipitation forecast especially to heavy rainfall. Overall, the initial perturbation of land surface variables and land surface parameter perturbations are significant to the initial ensemble forecast.
2014, 40(2):158-165.
DOI: 10.7519/j.issn.1000-0526.2014.02.003
Abstract:
After the radiosonde system of radiosonde station in China was upgraded to the L band sounding system, the high resolution vertical second level or minute level sounding data including temperature, pressure, humidity, wind profiles at 120 national stations can be continuously and automatically obtained. In this study, the high resolution vertical second level sounding profiling data are used to analyze the characteristics of their horizontal and vertical structures and to apply to GRAPES 3DVAR Regional Variational Assimilation Prediction System so as to compare the difference between the high resolution vertical second/minute level sounding profiling data and the traditional ones applied on the assimilation and prediction. The experiments using the data of June and July in the year of 2011 show encouraging results. The second level sounding profiling data can lead to a uniform horizontal distribution with highly dense vertical structure. The analyses of height field at 850 hPa and 500 hPa layers are closer to NCEP analyses than those with the traditional sounding data, which shows the improved effect for the analysis fields. Meanwhile, there is a significant improvement on the wind analysis fields for 200 hPa and higher layers, which shows the application of high resolution data on the high layer analysis can lead to more accurate system simulation. Furthmore, due to the improvement of the initial fields for the model prediction, the performance score for precipitation forecast increased and the forecast deviation obviously becomes smaller. Conclusively, the use of high resolution vertical radiosonde data has a positive impact on the initial analysis and forecast improvements of numerical model, which can provide the necessary foundation for the further development and utilization of second level radiosonde data.
After the radiosonde system of radiosonde station in China was upgraded to the L band sounding system, the high resolution vertical second level or minute level sounding data including temperature, pressure, humidity, wind profiles at 120 national stations can be continuously and automatically obtained. In this study, the high resolution vertical second level sounding profiling data are used to analyze the characteristics of their horizontal and vertical structures and to apply to GRAPES 3DVAR Regional Variational Assimilation Prediction System so as to compare the difference between the high resolution vertical second/minute level sounding profiling data and the traditional ones applied on the assimilation and prediction. The experiments using the data of June and July in the year of 2011 show encouraging results. The second level sounding profiling data can lead to a uniform horizontal distribution with highly dense vertical structure. The analyses of height field at 850 hPa and 500 hPa layers are closer to NCEP analyses than those with the traditional sounding data, which shows the improved effect for the analysis fields. Meanwhile, there is a significant improvement on the wind analysis fields for 200 hPa and higher layers, which shows the application of high resolution data on the high layer analysis can lead to more accurate system simulation. Furthmore, due to the improvement of the initial fields for the model prediction, the performance score for precipitation forecast increased and the forecast deviation obviously becomes smaller. Conclusively, the use of high resolution vertical radiosonde data has a positive impact on the initial analysis and forecast improvements of numerical model, which can provide the necessary foundation for the further development and utilization of second level radiosonde data.
2014, 40(2):166-173.
DOI: 10.7519/j.issn.1000-0526.2014.02.004
Abstract:
A one dimensional (1 D) heat diffusion lake model has been successfully coupled into the Weather Research and Forecasting (WRF) model version 3.2. The ability of simulating lake surface temperature of the coupled model (WRF Lake) was first tested in Taihu Lake using observations obtained from Meiliangwan Station from August 11 to 28, 2010. Three experiments were conducted to evaluate the performance of this coupled model. The three experiments include: (1) simulated by original WRF model without lake scheme (WRF); (2) simulated by coupled model without parameter optimization (WRF_Lake_Old); (3) simulated by coupled model with parameter optimization (WRF_Lake_New). Results show that the coupled model with parameter optimization (WRF_Lake_New) has greatly improved the lake surface temperature (LST) simulations when compared with that simulated by WRF. It is found that LSTs for the Meiliangwan Station simulated by WRF_Lake_New show good agreement with observations, WRF_Lake_New can generate realistically daily variation of LST, and the averaged LST bias range reduces to ±1℃. The averaged bias for 2 meter high air temperature is within the range of ±0.5℃. With the improvement of LST and 2 meter high air temperature simulations, the simulated sensible and latent heat flux are both much closer to observations than WRF simulations. These results show that the coupled model (WRF_Lake) has provided a good tool for the study of lake processes and lake atmosphere interactions in the future.
A one dimensional (1 D) heat diffusion lake model has been successfully coupled into the Weather Research and Forecasting (WRF) model version 3.2. The ability of simulating lake surface temperature of the coupled model (WRF Lake) was first tested in Taihu Lake using observations obtained from Meiliangwan Station from August 11 to 28, 2010. Three experiments were conducted to evaluate the performance of this coupled model. The three experiments include: (1) simulated by original WRF model without lake scheme (WRF); (2) simulated by coupled model without parameter optimization (WRF_Lake_Old); (3) simulated by coupled model with parameter optimization (WRF_Lake_New). Results show that the coupled model with parameter optimization (WRF_Lake_New) has greatly improved the lake surface temperature (LST) simulations when compared with that simulated by WRF. It is found that LSTs for the Meiliangwan Station simulated by WRF_Lake_New show good agreement with observations, WRF_Lake_New can generate realistically daily variation of LST, and the averaged LST bias range reduces to ±1℃. The averaged bias for 2 meter high air temperature is within the range of ±0.5℃. With the improvement of LST and 2 meter high air temperature simulations, the simulated sensible and latent heat flux are both much closer to observations than WRF simulations. These results show that the coupled model (WRF_Lake) has provided a good tool for the study of lake processes and lake atmosphere interactions in the future.
2014, 40(2):174-185.
DOI: 10.7519/j.issn.1000-0526.2014.02.005
Abstract:
Based on the air sounding data, the CIND3830 CC CINRAD data and surface observation data, the hail event processes seen in Puer and Xishuangbanna during 2004-2011 are analyzed. The results show that: (1) hail can be forecasted 60 min in advance when initial and developing features of hail cloud appear in the radar echo images. (2) Hail can be forecasted 12 to 102 min earlier before the event occurs, if echo composite reflectivity ≥55 dBz, width ≥ 12.0 km, gradient ≥ 15 dBz·km-1, H45 dBz ≥ 7.5 km, H45 dBz-H0 ≥ 3.1 km and H45 dBz-H-20≥ -0.5 km during February-May, H45 dBz-H0 ≥ 2.0 km and H45 dBz-H-20 ≥ -1.2 km, VIL ≥ 30 kg·m-2, DVIL ≥ 3.0 g·m-3 during June-August. (3) If the echo shows the features of weak shear, echo top in 45 dBz≥7.5 km, H45 dBz-H0≥3.1 km and H45 dBz-H-20≥-0.5 km during February-May, H45 dBz-H0≥2.0 km and H45 dBz-H-20≥-1.2 km during June-August, hail can be forecasted with 18-54 min in advance. (4) In addition to squall line and downburst, hail can be forecasted 12-54 min earlier if VIL≥30 kg·m-2, DVIL≥3.0 g·m-3. Besides, this paper summarizes the characteristics of hail cloud lifetime, and tests forecast indice by using the hail process in 2012.
Based on the air sounding data, the CIND3830 CC CINRAD data and surface observation data, the hail event processes seen in Puer and Xishuangbanna during 2004-2011 are analyzed. The results show that: (1) hail can be forecasted 60 min in advance when initial and developing features of hail cloud appear in the radar echo images. (2) Hail can be forecasted 12 to 102 min earlier before the event occurs, if echo composite reflectivity ≥55 dBz, width ≥ 12.0 km, gradient ≥ 15 dBz·km-1, H45 dBz ≥ 7.5 km, H45 dBz-H0 ≥ 3.1 km and H45 dBz-H-20≥ -0.5 km during February-May, H45 dBz-H0 ≥ 2.0 km and H45 dBz-H-20 ≥ -1.2 km, VIL ≥ 30 kg·m-2, DVIL ≥ 3.0 g·m-3 during June-August. (3) If the echo shows the features of weak shear, echo top in 45 dBz≥7.5 km, H45 dBz-H0≥3.1 km and H45 dBz-H-20≥-0.5 km during February-May, H45 dBz-H0≥2.0 km and H45 dBz-H-20≥-1.2 km during June-August, hail can be forecasted with 18-54 min in advance. (4) In addition to squall line and downburst, hail can be forecasted 12-54 min earlier if VIL≥30 kg·m-2, DVIL≥3.0 g·m-3. Besides, this paper summarizes the characteristics of hail cloud lifetime, and tests forecast indice by using the hail process in 2012.
2014, 40(2):186-195.
DOI: 10.7519/j.issn.1000-0526.2014.02.006
Abstract:
Two warm area heavy rain processes in 25-26 May 2008 (“0805”) and 28-29 June 2010 (“1006”) in Guizhou are analyzed based on the conventional observational data and the NCEP 1°×1° reanalysis data. The similar and different features of the two processes in early summer in Guizhou are compard. The results indicate that there is no cold air but warm low pressure near the surface when the two torrential rains occur. The low level jet at 850 hPa enhances obviously, and the heavy rain areas are found in the left front of low level jet. What’s different is that synoptic systems in middle and high levels in the two rain cases are different. In the “0805” heavy rain process the middle level is affected by plateau trough, but in the “1006” heavy rain case the mid level system is the shear vortex between two high pressures while the high level is affected by South Asia high ridge. In the “0805” heavy rain case, several meso β scale convective cells grow up and are combined in to a mesoscale convective syestem (MCS). The convective clouds develop severely. Base reflectivity of vertical cross section of Guiyang Radar shows it has warm cloud layer and mixing liquid phase layer. In the “1006” heavy rain case, the single meso β scale convective cells grow up very quickly, finally into MCS. The convection develops strongly with a deep warm cloud layer. Analyzing their trigger mechanism, it is found that the key points to warm area heavy rain in Guizhou lie in the building and enhancement of the low level jet as well as the enhanced frontogenesis of convergence line in the surface low pressure.
Two warm area heavy rain processes in 25-26 May 2008 (“0805”) and 28-29 June 2010 (“1006”) in Guizhou are analyzed based on the conventional observational data and the NCEP 1°×1° reanalysis data. The similar and different features of the two processes in early summer in Guizhou are compard. The results indicate that there is no cold air but warm low pressure near the surface when the two torrential rains occur. The low level jet at 850 hPa enhances obviously, and the heavy rain areas are found in the left front of low level jet. What’s different is that synoptic systems in middle and high levels in the two rain cases are different. In the “0805” heavy rain process the middle level is affected by plateau trough, but in the “1006” heavy rain case the mid level system is the shear vortex between two high pressures while the high level is affected by South Asia high ridge. In the “0805” heavy rain case, several meso β scale convective cells grow up and are combined in to a mesoscale convective syestem (MCS). The convective clouds develop severely. Base reflectivity of vertical cross section of Guiyang Radar shows it has warm cloud layer and mixing liquid phase layer. In the “1006” heavy rain case, the single meso β scale convective cells grow up very quickly, finally into MCS. The convection develops strongly with a deep warm cloud layer. Analyzing their trigger mechanism, it is found that the key points to warm area heavy rain in Guizhou lie in the building and enhancement of the low level jet as well as the enhanced frontogenesis of convergence line in the surface low pressure.
2014, 40(2):196-205.
DOI: 10.7519/j.issn.1000-0526.2014.02.007
Abstract:
The cloud microphysical characteristics with aircraft icing during 7 flights are analyzed. The cloud phase, liquid water content, median volume diameter and the concentration of supercooled large droplets are described in detail. The aircraft icing potential monitoring technology which combines satellite, numerical model outputs and surface observations are introduced. In comparison with 20 icing reports during 2000-2010, it is found that it can detect 90% of icing correctly. The aircraft icing on 26 October 2010 is analyzed. Finally, the aircraft icing monitoring system based on aircraft icing potential detection technology is showed. The system determines the products of aircraft icing potential with horizontal resolution of 20 km, vertical resolution of 25 hPa, and temporal of 1 h. So, this system can be used in actual operations.
The cloud microphysical characteristics with aircraft icing during 7 flights are analyzed. The cloud phase, liquid water content, median volume diameter and the concentration of supercooled large droplets are described in detail. The aircraft icing potential monitoring technology which combines satellite, numerical model outputs and surface observations are introduced. In comparison with 20 icing reports during 2000-2010, it is found that it can detect 90% of icing correctly. The aircraft icing on 26 October 2010 is analyzed. Finally, the aircraft icing monitoring system based on aircraft icing potential detection technology is showed. The system determines the products of aircraft icing potential with horizontal resolution of 20 km, vertical resolution of 25 hPa, and temporal of 1 h. So, this system can be used in actual operations.
2014, 40(2):206-215.
DOI: 10.7519/j.issn.1000-0526.2014.02.008
Abstract:
By using the Doppler radar data and the conventional observation of 29 torrential rain processes from 2004 to 2010 the velocity field characteristics in rainstorms in south central Hebei Province are analyzed. It is found that the characteristics can be divided into five categories, including the meso β scale convergence line, the meso β scale convergence, the meso γ scale convergence, the upper level jet and the long lasting and deep low level jet. The last one is one of the main velocity field features of large range severe rainstorms. The upper level jet is the characteristic of both large range heavy rainstorms and regional heavy rainstorms. The meso β scale convergence line, the meso β scale convergence and the meso γ scale convergence are common features and main meso scale systems of all the three types of severe rainstorms. In addition, train effects is a key cause of local severe torrential rains.
By using the Doppler radar data and the conventional observation of 29 torrential rain processes from 2004 to 2010 the velocity field characteristics in rainstorms in south central Hebei Province are analyzed. It is found that the characteristics can be divided into five categories, including the meso β scale convergence line, the meso β scale convergence, the meso γ scale convergence, the upper level jet and the long lasting and deep low level jet. The last one is one of the main velocity field features of large range severe rainstorms. The upper level jet is the characteristic of both large range heavy rainstorms and regional heavy rainstorms. The meso β scale convergence line, the meso β scale convergence and the meso γ scale convergence are common features and main meso scale systems of all the three types of severe rainstorms. In addition, train effects is a key cause of local severe torrential rains.
2014, 40(2):216-222.
DOI: 10.7519/j.issn.1000-0526.2014.02.009
Abstract:
Using ground based microwave radiometer observation data, two hailstorm cases that happened in Xianning of Hubei Province on 26 February 2009 and 12 April 2010 are analyzed. The results show that low level warm air transportation and mid level dry cold air intrusion contributes to the “upper dry and lower wet” 2 layer vertical structure of 0-10 km relative humidity. The updraft transports upward sensible heat and latent heat of the low level, resulting in the significant warming of 2-3 km layer, and the slight rising of 0, -5 and -20℃ layers. As the low level moisture is rising up, ILW, IWV and super cooled water grow rapidly before the hail. After the wet vapor goes through the cold layer, the ice crystals increase. When the ice crystals increase and fall into the area above 0℃ melting layer, the ice crystals are melted, leading to an increase in liquid water, and part of the water becomes hails or surface precipitation, so that the ILW, IWV and liquid water content below 0℃ decrease after hails. The above conclusion is of some significance to the early warning of hails.
Using ground based microwave radiometer observation data, two hailstorm cases that happened in Xianning of Hubei Province on 26 February 2009 and 12 April 2010 are analyzed. The results show that low level warm air transportation and mid level dry cold air intrusion contributes to the “upper dry and lower wet” 2 layer vertical structure of 0-10 km relative humidity. The updraft transports upward sensible heat and latent heat of the low level, resulting in the significant warming of 2-3 km layer, and the slight rising of 0, -5 and -20℃ layers. As the low level moisture is rising up, ILW, IWV and super cooled water grow rapidly before the hail. After the wet vapor goes through the cold layer, the ice crystals increase. When the ice crystals increase and fall into the area above 0℃ melting layer, the ice crystals are melted, leading to an increase in liquid water, and part of the water becomes hails or surface precipitation, so that the ILW, IWV and liquid water content below 0℃ decrease after hails. The above conclusion is of some significance to the early warning of hails.
2014, 40(2):223-228.
DOI: 10.7519/j.issn.1000-0526.2014.02.010
Abstract:
A predicting model, low frequency synoptic chart, is developed to forecast severe precipitation events in Hunan Region based on NCEP/NCAR reanalysis data of 500 hPa height and 700 hPa winds as well as the daily rainfall data from 97 observation stations in Hunan Province during 2006-2010. Meanwhile, the synoptic key regions are determined and the characteristics of low frequency waves are analyzed. Using historic data for validation, the average fitting rate of hindcast is 64.4% in April, 54.9% in May and 50.7% in June. Compared with the lead time of 10 d, 15 d, 20 d and 25 d, the fitting rate of hindcasts increases to the maximum at the lead time of 30 d. Applying the data to the forecasting of the severe precipitation events from April to June 2011 gives a good prediction result with the accuracy rate reaching 70%, the vacancy rate being 30% and no missing rate
A predicting model, low frequency synoptic chart, is developed to forecast severe precipitation events in Hunan Region based on NCEP/NCAR reanalysis data of 500 hPa height and 700 hPa winds as well as the daily rainfall data from 97 observation stations in Hunan Province during 2006-2010. Meanwhile, the synoptic key regions are determined and the characteristics of low frequency waves are analyzed. Using historic data for validation, the average fitting rate of hindcast is 64.4% in April, 54.9% in May and 50.7% in June. Compared with the lead time of 10 d, 15 d, 20 d and 25 d, the fitting rate of hindcasts increases to the maximum at the lead time of 30 d. Applying the data to the forecasting of the severe precipitation events from April to June 2011 gives a good prediction result with the accuracy rate reaching 70%, the vacancy rate being 30% and no missing rate
2014, 40(2):229-233.
DOI: 10.7519/j.issn.1000-0526.2014.02.011
Abstract:
Based on daily discoloration percentage and meteorological datasets, the meteorological conditions of cotinus coggygria leaves discoloration (CCLD) are studied and the staticstical prediction model is built. The results are as follows: (1) CCLD has a close relationship with temperature variation in the near several days, and the reliability of CCLD Day forecast by meteorological threshold is high. (2) The mean CCLD Day is between October 4 and 5, the earliest CCLD Day is September 27, and the latest one is October 13. (3) There is significant negative correlation between CCLD Day and the mean temperature (also minimum temperature and maximum temperature) in July. It should be noticed that the annual increment of CCLD Day has significant positive correlation with that of precipitation in July. (4) Choosing the annual increment of mean and maximum temperature in July as predictors, the statistical prediction model based on meteorology is built, and the mean error is around 3 days. (5) According to the 2011 independent sample verification and the 2012 forecast experiment, the prediction model of CCLD Day is proved to be usable.
Based on daily discoloration percentage and meteorological datasets, the meteorological conditions of cotinus coggygria leaves discoloration (CCLD) are studied and the staticstical prediction model is built. The results are as follows: (1) CCLD has a close relationship with temperature variation in the near several days, and the reliability of CCLD Day forecast by meteorological threshold is high. (2) The mean CCLD Day is between October 4 and 5, the earliest CCLD Day is September 27, and the latest one is October 13. (3) There is significant negative correlation between CCLD Day and the mean temperature (also minimum temperature and maximum temperature) in July. It should be noticed that the annual increment of CCLD Day has significant positive correlation with that of precipitation in July. (4) Choosing the annual increment of mean and maximum temperature in July as predictors, the statistical prediction model based on meteorology is built, and the mean error is around 3 days. (5) According to the 2011 independent sample verification and the 2012 forecast experiment, the prediction model of CCLD Day is proved to be usable.
2014, 40(2):234-237.
DOI: 10.7519/j.issn.1000-0526.2014.02.012
Abstract:
In the ground meteorological observation, it generally takes artificial observation to judge whether icing phenomenon occurs. In order to improve the efficiency of icing observation, automation of icing observation has become an inevitable trend. This paper introduces a new automatic observation device for icing through detecting the sudden rise process of temperature that is caused by latent heat release in the icing process, and judges the occurrence of icing phenomenon to realize the automation of icing observation. Combined with temperature observation data, characteristics of each stage in the icing process are analyzed as well. Compared with the artificial icing observation results, it is concluded that the automation observation device for icing can accurately observe icing phenomenon.
In the ground meteorological observation, it generally takes artificial observation to judge whether icing phenomenon occurs. In order to improve the efficiency of icing observation, automation of icing observation has become an inevitable trend. This paper introduces a new automatic observation device for icing through detecting the sudden rise process of temperature that is caused by latent heat release in the icing process, and judges the occurrence of icing phenomenon to realize the automation of icing observation. Combined with temperature observation data, characteristics of each stage in the icing process are analyzed as well. Compared with the artificial icing observation results, it is concluded that the automation observation device for icing can accurately observe icing phenomenon.
2014, 40(2):238-246.
DOI: 10.7519/j.issn.1000-0526.2014.02.013
Abstract:
The comparative analysis on observation data of the L band radar sounding system and 59 701 sounding system by four sounding stations in Sichuan is made in this paper. The results indicate that temperature and geopotential height data observed by 59 701 sounding system made in Taiyuan are higher than that observed by 59 701 sounding system made in Shanghai. The temperature and geopotential height data below 100 hPa do not change obviously after using L band sounding system, but above 100 hPa they change obviously. Humidity data measured by the two sounding systems have large differences. The differences near surface are small, increasing with height. Most of the humidity data measured by L band sounding system are lower than that measured by 59 701 sounding system. The differences between average wind direction and velocity measured by the two sounding systems are small. Peak value differences of all elements are large. The discrete case of each elements difference changes with different heights. The greatest degree of general discrete is geopotential height, secondly is the wind direction, humidity, dew point, wind speed, and temperature in sequence. The trends of differences between the two sounding systems are not large, but relations exist between the difference changes of humidity, wind direction, wind speed and the geographic location, season, and releasing time. There are differences between L band and 59 701 sounding systems in equipment, measuring principle, measurement accuracy, the revised statistics, methods of observation, releasing time and so on.
The comparative analysis on observation data of the L band radar sounding system and 59 701 sounding system by four sounding stations in Sichuan is made in this paper. The results indicate that temperature and geopotential height data observed by 59 701 sounding system made in Taiyuan are higher than that observed by 59 701 sounding system made in Shanghai. The temperature and geopotential height data below 100 hPa do not change obviously after using L band sounding system, but above 100 hPa they change obviously. Humidity data measured by the two sounding systems have large differences. The differences near surface are small, increasing with height. Most of the humidity data measured by L band sounding system are lower than that measured by 59 701 sounding system. The differences between average wind direction and velocity measured by the two sounding systems are small. Peak value differences of all elements are large. The discrete case of each elements difference changes with different heights. The greatest degree of general discrete is geopotential height, secondly is the wind direction, humidity, dew point, wind speed, and temperature in sequence. The trends of differences between the two sounding systems are not large, but relations exist between the difference changes of humidity, wind direction, wind speed and the geographic location, season, and releasing time. There are differences between L band and 59 701 sounding systems in equipment, measuring principle, measurement accuracy, the revised statistics, methods of observation, releasing time and so on.
2014, 40(2):247-252.
DOI: 10.7519/j.issn.1000-0526.2014.02.014
Abstract:
In order to improve the ability of using the products of T639, a synoptic verification on its medium range forecasting prodcuts in autumn 2013 is made, and then compared with the NWP of ECMWF and Japan models. The results show that all the three models have good performances on the aspect of predicting large scale circulation evolution and adjustment in Asian middle and high latitude areas. As a whole, the ECMWF model is much better in forecasting most weather systems compared with the T639 and Japan models. Taking the strong tropical storm No.1319 (Usagi) process during the period of September 20-22, 2013 as a case, it is found that the ECMWF model is more effective than the other two models in medium range forecasting of the turning track of USAGI and its landing point.
In order to improve the ability of using the products of T639, a synoptic verification on its medium range forecasting prodcuts in autumn 2013 is made, and then compared with the NWP of ECMWF and Japan models. The results show that all the three models have good performances on the aspect of predicting large scale circulation evolution and adjustment in Asian middle and high latitude areas. As a whole, the ECMWF model is much better in forecasting most weather systems compared with the T639 and Japan models. Taking the strong tropical storm No.1319 (Usagi) process during the period of September 20-22, 2013 as a case, it is found that the ECMWF model is more effective than the other two models in medium range forecasting of the turning track of USAGI and its landing point.
2014, 40(2):253-260.
DOI: 10.7519/j.issn.1000-0526.2014.02.015
Abstract:
The main characteristics of the general atmospheric circulation in November 2013 are as follows. There is one polar vortex center located in the Arctic Circle in the Northern Hemisphere with stronger strength than normal years. The circulation presents latitudinal patterns in middle and high latitudes. The average south branch trough is located around 80°E. The subtropical high is stronger than normal years, located more westward and northward. The monthly mean precipitation is 22.5 mm, 19.7% more than the normal (18.8 mm). The monthly mean temperature is 3.6℃, 0.7℃ higher than the normal (2.9℃). There are three cold air processes and six heavier rainfall processes during this month. The Northeast Region suffers from extreme snows twice and some places are hit by snowstorm or blizzards. Tropical cyclone “Haiyan” brings gale and heavy rains to South China. There are obvious rainfalls in the northern winter wheat region and the Jiangnan Region. Meanwhile, the fog and the haze appear in the central and eastern China due to the weak cold airs. The monthly mean fog and haze days are 4.3 days, which is the maximum record since 1961.
The main characteristics of the general atmospheric circulation in November 2013 are as follows. There is one polar vortex center located in the Arctic Circle in the Northern Hemisphere with stronger strength than normal years. The circulation presents latitudinal patterns in middle and high latitudes. The average south branch trough is located around 80°E. The subtropical high is stronger than normal years, located more westward and northward. The monthly mean precipitation is 22.5 mm, 19.7% more than the normal (18.8 mm). The monthly mean temperature is 3.6℃, 0.7℃ higher than the normal (2.9℃). There are three cold air processes and six heavier rainfall processes during this month. The Northeast Region suffers from extreme snows twice and some places are hit by snowstorm or blizzards. Tropical cyclone “Haiyan” brings gale and heavy rains to South China. There are obvious rainfalls in the northern winter wheat region and the Jiangnan Region. Meanwhile, the fog and the haze appear in the central and eastern China due to the weak cold airs. The monthly mean fog and haze days are 4.3 days, which is the maximum record since 1961.
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ISSN:1000-0526 CN:11-2282/P