ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 35,Issue 9,2009 Table of Contents
2009, 35(9):3-10.
DOI: 10.7519/j.issn.1000-0526.2009.9.001
Abstract:
The impact of terrain on the precipitation during the landfall of “KROSA” (071 6) was analyzed with reanalysis data of JMA, topography data and the high resolu tion rain data generated by the variation method. The correlation coefficient be tween total precipitation and topography indicated that the terrain over Zhejian g largely affected the precipitation. The peak rainfall is located mainly on the windward hillsides. The distribution of frequency of different precipitation r anks showed that the relatively stronger precipitation happened in the topograp hic regions. The rain gains caused by the mountains along the southeastern coast of Zhejiang we re more than those caused by mountains along northeastern coast. With the reanal ysis data of JMA, the nondimensional number of flow crossing the topography was counted. As the value of Fr was small in this case, the air could flow over the hills more easily. The forced upward motion occurred windward in associati on with the heavy precipitation. The forced vertical velocity penetrated more de eply in southeastern coast than in northeastern coast, which might be the reason that the rain gains in southeastern coast were more than in northeastern coast.
The impact of terrain on the precipitation during the landfall of “KROSA” (071 6) was analyzed with reanalysis data of JMA, topography data and the high resolu tion rain data generated by the variation method. The correlation coefficient be tween total precipitation and topography indicated that the terrain over Zhejian g largely affected the precipitation. The peak rainfall is located mainly on the windward hillsides. The distribution of frequency of different precipitation r anks showed that the relatively stronger precipitation happened in the topograp hic regions. The rain gains caused by the mountains along the southeastern coast of Zhejiang we re more than those caused by mountains along northeastern coast. With the reanal ysis data of JMA, the nondimensional number of flow crossing the topography was counted. As the value of Fr was small in this case, the air could flow over the hills more easily. The forced upward motion occurred windward in associati on with the heavy precipitation. The forced vertical velocity penetrated more de eply in southeastern coast than in northeastern coast, which might be the reason that the rain gains in southeastern coast were more than in northeastern coast.
2009, 35(9):11-17.
DOI: 10.7519/j.issn.1000-0526.2009.9.002
Abstract:
Based on archives of Doppler radar, AWS and other data, local severe storms in S hanghai are classified into 4 main types. After careful analysis and comparison, some forecasting points are summarized as follows. Initial places of st orms are mostly massed at north of Shanghai, which keeps close connections with surface weak convergence lines; Developing from initial echo to peak stage will take about 1 hour; Upstream echo takes priority to develop; Strong wind at 2 00hPa level can largely affect the developing pattern of local severe storms. Us ually, northwesterly is not favorable for fast moving echoes, but in case of sou thwesterly, the echo moves quite fast. Low level wind speed is crucial to echoes ' motion and triggering of strong gusts. Those points could be useful references for local severe storms' nowcasting in Shanghai and other similar areas.
Based on archives of Doppler radar, AWS and other data, local severe storms in S hanghai are classified into 4 main types. After careful analysis and comparison, some forecasting points are summarized as follows. Initial places of st orms are mostly massed at north of Shanghai, which keeps close connections with surface weak convergence lines; Developing from initial echo to peak stage will take about 1 hour; Upstream echo takes priority to develop; Strong wind at 2 00hPa level can largely affect the developing pattern of local severe storms. Us ually, northwesterly is not favorable for fast moving echoes, but in case of sou thwesterly, the echo moves quite fast. Low level wind speed is crucial to echoes ' motion and triggering of strong gusts. Those points could be useful references for local severe storms' nowcasting in Shanghai and other similar areas.
2009, 35(9):18-28.
DOI: 10.7519/j.issn.1000-0526.2009.9.003
Abstract:
Right now, the warning accuracy of the high wind is lower and the lead ing time is also very limited in Beijing. In order to change the situation, the forecasting methods are developed. Based on the statistics for 134 cases, it is known that most of the high wind events are caused by the downbursts and some of them break out while the hails are falling. Therefore, the negative buoyancy an d the hail storm factors should be taken into consideration in study of this sev ere weather. Even though most of the high winds break out when the air at the middl e level becomes drier, there are still a few of events appearing in the warm and wet flow. The mechanism for the latter one is not clear yet. When there is some dryincursion in the middle level of troposphere, the favorable conditions for the h igh wind are the great instability in ambient for downdraft and higher temperatu re lapse rate in the lower level. Besides, the use of WINDEX is also discussed. The potential forecasting method is developed on the basis of above study. Furth ermore, the nowcasting equation on the basis of the radar reflectivity, radial s peed a nd so on as the forecasting factors is given through the correlation analysis an d multiple regression analysis. The case study shows that some strong wind gusts caused by squallline or bow echo could be forecasted successfully by using th e equation.
Right now, the warning accuracy of the high wind is lower and the lead ing time is also very limited in Beijing. In order to change the situation, the forecasting methods are developed. Based on the statistics for 134 cases, it is known that most of the high wind events are caused by the downbursts and some of them break out while the hails are falling. Therefore, the negative buoyancy an d the hail storm factors should be taken into consideration in study of this sev ere weather. Even though most of the high winds break out when the air at the middl e level becomes drier, there are still a few of events appearing in the warm and wet flow. The mechanism for the latter one is not clear yet. When there is some dryincursion in the middle level of troposphere, the favorable conditions for the h igh wind are the great instability in ambient for downdraft and higher temperatu re lapse rate in the lower level. Besides, the use of WINDEX is also discussed. The potential forecasting method is developed on the basis of above study. Furth ermore, the nowcasting equation on the basis of the radar reflectivity, radial s peed a nd so on as the forecasting factors is given through the correlation analysis an d multiple regression analysis. The case study shows that some strong wind gusts caused by squallline or bow echo could be forecasted successfully by using th e equation.
2009, 35(9):29-37.
DOI: 10.7519/j.issn.1000-0526.2009.9.004
Abstract:
Using the highresolution mesoscale model WRF, a strong squall line process on April 17, 2007 in South China was simulated.The numerical simulation results were used to make the diagnostic analysis on the strong squall line process, a nd to explore its trigger and maintenance mechanism. The results show that low l evel mesoscale convergence line and shear line are one of the main trigger syste ms of this squall line process and one of the important maintenance mechanisms. And also the dry invasion and con vective instability, and convergence and divergence from bottom to top play an i mportant role in the development and maintenance of the squall line.In addition, mesoβ scale structure characteristics of the strong squall line process are successfully simulated, indicating that the WRF model has a certain simulation capability of strong convective weather systems.
Using the highresolution mesoscale model WRF, a strong squall line process on April 17, 2007 in South China was simulated.The numerical simulation results were used to make the diagnostic analysis on the strong squall line process, a nd to explore its trigger and maintenance mechanism. The results show that low l evel mesoscale convergence line and shear line are one of the main trigger syste ms of this squall line process and one of the important maintenance mechanisms. And also the dry invasion and con vective instability, and convergence and divergence from bottom to top play an i mportant role in the development and maintenance of the squall line.In addition, mesoβ scale structure characteristics of the strong squall line process are successfully simulated, indicating that the WRF model has a certain simulation capability of strong convective weather systems.
2009, 35(9):38-43.
DOI: 10.7519/j.issn.1000-0526.2009.9.005
Abstract:
To examine the uncertainties of tropical cyclone track forecast, track errors of the comprehensive forecast of National Meteorological Center during 2 004-2007 are used to build a statistical model to produce tropical cyclone strik ing probability. It could be a meaningful reference for issuing typhoon warning.
To examine the uncertainties of tropical cyclone track forecast, track errors of the comprehensive forecast of National Meteorological Center during 2 004-2007 are used to build a statistical model to produce tropical cyclone strik ing probability. It could be a meaningful reference for issuing typhoon warning.
2009, 35(9):44-50.
DOI: 10.7519/j.issn.1000-0526.2009.9.006
Abstract:
Based on the 1945-2008 typhoon data from JTWC, the accumulative cyclone energy ( ACE) over the western North Pacific is calculated. The characters and the relati onship between ACE and SST in NINO3.4 are analyzed. The following results are ob tained. ACE is mostly concentrated in June-December. The activity of ACE occurs at regular intervals. After 1990, the frequency of extreme strong typhoon had a n increasing tendency obviously. The relationship of ACE in June-December and a nomalous SST in NINO3.4 is notable. Abnormal Walker circulation and Hadley cell play an important role in the relationship between ACE and SST.
Based on the 1945-2008 typhoon data from JTWC, the accumulative cyclone energy ( ACE) over the western North Pacific is calculated. The characters and the relati onship between ACE and SST in NINO3.4 are analyzed. The following results are ob tained. ACE is mostly concentrated in June-December. The activity of ACE occurs at regular intervals. After 1990, the frequency of extreme strong typhoon had a n increasing tendency obviously. The relationship of ACE in June-December and a nomalous SST in NINO3.4 is notable. Abnormal Walker circulation and Hadley cell play an important role in the relationship between ACE and SST.
2009, 35(9):51-58.
DOI: 10.7519/j.issn.1000-0526.2009.9.007
Abstract:
By using the summer(June-August) monthly mean precipitation data from 25 meteor ological stations in Tarim Basin during 1979-2003 and the new NCEP/DOE monthly mean grou nd heat fluxes data, the relationships between spring and summer ground heat flu xes of Taklimakan desert and summer precipitation abnormity in South Xinjian g were analyzed with the SVD (singular value decomposition). Results show that t he first pattern from SVD indicates the coupling characteristics of ground heat fields and summer precipitation fields with closely temporal and spatial correlations. The west and northwest areas in SouthXinjiang and de sert middle part (37°-40°N, 78°-83°E） are the prominence area of SVD coupling co r relation. The first SVD mode of desert spring and summer surface sensible heat f ield and summer precipitation in the South Xinjiang shows that there is an appar ent negative co rrelation between ground sensible heat fields and the summer precipitation. When the sensible heat of main desert region is small (great), and desert middle par t is small (great) obviously, summer precipitation anomaly corresponds to more (les s) in South Xinjiang, in which the west and northwest areas of the South Xinjian g are notably more (less). The first SVD mode of desert spring and s ummer surface latent heat field and summer precipitation in the South Xinjiang s hows that there is an apparent positive correlation between ground latent heat f ields and the summer p recipitation. When the latent heat of whole desert is large (small), and desert middle part is large (small) obviously, summer precipitation anomaly corresponds to more (less) in South Xinjiang, in which the west and northwest areas of the South Xinjiang are notably more (less). Ground sensible heat and latent heat a bnormity of Taklimakan desert in spring is a signal of summer precipitation in S outh Xinjiang.
By using the summer(June-August) monthly mean precipitation data from 25 meteor ological stations in Tarim Basin during 1979-2003 and the new NCEP/DOE monthly mean grou nd heat fluxes data, the relationships between spring and summer ground heat flu xes of Taklimakan desert and summer precipitation abnormity in South Xinjian g were analyzed with the SVD (singular value decomposition). Results show that t he first pattern from SVD indicates the coupling characteristics of ground heat fields and summer precipitation fields with closely temporal and spatial correlations. The west and northwest areas in SouthXinjiang and de sert middle part (37°-40°N, 78°-83°E） are the prominence area of SVD coupling co r relation. The first SVD mode of desert spring and summer surface sensible heat f ield and summer precipitation in the South Xinjiang shows that there is an appar ent negative co rrelation between ground sensible heat fields and the summer precipitation. When the sensible heat of main desert region is small (great), and desert middle par t is small (great) obviously, summer precipitation anomaly corresponds to more (les s) in South Xinjiang, in which the west and northwest areas of the South Xinjian g are notably more (less). The first SVD mode of desert spring and s ummer surface latent heat field and summer precipitation in the South Xinjiang s hows that there is an apparent positive correlation between ground latent heat f ields and the summer p recipitation. When the latent heat of whole desert is large (small), and desert middle part is large (small) obviously, summer precipitation anomaly corresponds to more (less) in South Xinjiang, in which the west and northwest areas of the South Xinjiang are notably more (less). Ground sensible heat and latent heat a bnormity of Taklimakan desert in spring is a signal of summer precipitation in S outh Xinjiang.
2009, 35(9):59-67.
DOI: 10.7519/j.issn.1000-0526.2009.9.008
Abstract:
Monthly runoff in the Hanjiang River Basin from 1971 to 2000 was simulated by us ing the SWAT model. The results show that SWAT simulation precision is high er than the criterion(Ens>0.5，r2>0.6), and the SWAT model is appropriate to simulate the runoff in the Hanjiang River Basin. Among the essentials of wate r balance, the percentages of 30a monthly/annual mean evapotranspiration, surfa ce runoff, percolation, soil water, lateral flow to the amount of rainfall are 5 5.97%, 25.88%, 17.64%, 0.26%, and 0.25% respectively, and evapotranspiration is the main output item of rainfall. The trend of monthly mean rainfall from 1971 t o 2000 is in accordance with the trend of surface runoff in Hanjiang RiverBasin , but is not in accordance with base flow; the trend of annual mean rainfall from 1971 to 2000 is in accordance with the trend of surface runoff and base flow; the 30a monthly/yearly surface runoff’s response to rainfall is higher than base flow.
Monthly runoff in the Hanjiang River Basin from 1971 to 2000 was simulated by us ing the SWAT model. The results show that SWAT simulation precision is high er than the criterion(Ens>0.5，r2>0.6), and the SWAT model is appropriate to simulate the runoff in the Hanjiang River Basin. Among the essentials of wate r balance, the percentages of 30a monthly/annual mean evapotranspiration, surfa ce runoff, percolation, soil water, lateral flow to the amount of rainfall are 5 5.97%, 25.88%, 17.64%, 0.26%, and 0.25% respectively, and evapotranspiration is the main output item of rainfall. The trend of monthly mean rainfall from 1971 t o 2000 is in accordance with the trend of surface runoff in Hanjiang RiverBasin , but is not in accordance with base flow; the trend of annual mean rainfall from 1971 to 2000 is in accordance with the trend of surface runoff and base flow; the 30a monthly/yearly surface runoff’s response to rainfall is higher than base flow.
2009, 35(9):68-76.
DOI: 10.7519/j.issn.1000-0526.2009.9.009
Abstract:
By using the high temperature data of 35 meteorological observation stations in Chongqing from 1960 to 2006, the spatiotemporal variation features of high temperature day (HTD) are studied. The results show that there are four regions with more HTD in Chongqing. The largest values of general, serious and special serious HTD are 21d/a, 14d/a and 2d/a respectively. The HTD occurs mainly in Jul y and August, and there are much more HTDs in August than in July. In the recent 47 years, the HTD has an evolutional trend of increasingdecreasingincreasi ng and the variation tendency of serious HTD is especially obvious.
By using the high temperature data of 35 meteorological observation stations in Chongqing from 1960 to 2006, the spatiotemporal variation features of high temperature day (HTD) are studied. The results show that there are four regions with more HTD in Chongqing. The largest values of general, serious and special serious HTD are 21d/a, 14d/a and 2d/a respectively. The HTD occurs mainly in Jul y and August, and there are much more HTDs in August than in July. In the recent 47 years, the HTD has an evolutional trend of increasingdecreasingincreasi ng and the variation tendency of serious HTD is especially obvious.
2009, 35(9):77-83.
DOI: 10.7519/j.issn.1000-0526.2009.9.010
Abstract:
The numerical simulation using the NCEP/NCAR 1°×1° global reanalysis in January 2008 and the MM5 mesoscale model is performed to investigate the stru cture and characteristics of Kunming quasistationary front (KQSF) during the extrem e low temperature and frozen snow events over southern China. The results indi cate th at the formation and its maintenance of KQSF are the consequence of the obstruct i on due to plateau terrain and special synoptic system configuration under the i nflu ence of the longtime, repeating cold airs over southern China. It is foun d t hat the obstruction of plateau terrain is necessary for the formation and the ma intenance of KQSF by the sensitivity numerical experiments of halving terrain.
The numerical simulation using the NCEP/NCAR 1°×1° global reanalysis in January 2008 and the MM5 mesoscale model is performed to investigate the stru cture and characteristics of Kunming quasistationary front (KQSF) during the extrem e low temperature and frozen snow events over southern China. The results indi cate th at the formation and its maintenance of KQSF are the consequence of the obstruct i on due to plateau terrain and special synoptic system configuration under the i nflu ence of the longtime, repeating cold airs over southern China. It is foun d t hat the obstruction of plateau terrain is necessary for the formation and the ma intenance of KQSF by the sensitivity numerical experiments of halving terrain.
2009, 35(9):84-90.
DOI: 10.7519/j.issn.1000-0526.2009.9.011
Abstract:
Based on the conventional observation and NCEP reanalysis data, the synoptic ana lysis of a rare heavy fog process occurring in the eastern China was carried out. The result shows that the height and intensity of the inversion layer are related to the formati o n and status of the fog, weak cold and warm advections are both advantageous to pr oducing fog. Furthermore, the temperature advection quickly turns into reverse at some height near the surface, and thus makes temper ature stratification from unstable into stable, all these are benefical to prod uce the hea vy fog. The inversion layer which formed in the interface of ascending and desce nding movement is the important fact for producing the heavy fog.
Based on the conventional observation and NCEP reanalysis data, the synoptic ana lysis of a rare heavy fog process occurring in the eastern China was carried out. The result shows that the height and intensity of the inversion layer are related to the formati o n and status of the fog, weak cold and warm advections are both advantageous to pr oducing fog. Furthermore, the temperature advection quickly turns into reverse at some height near the surface, and thus makes temper ature stratification from unstable into stable, all these are benefical to prod uce the hea vy fog. The inversion layer which formed in the interface of ascending and desce nding movement is the important fact for producing the heavy fog.
2009, 35(9):91-97.
DOI: 10.7519/j.issn.1000-0526.2009.9.012
Abstract:
Based on the automatic meteorological station, Doppler radar and NCEP reana lysis data of 1°×1° with 6 h interval, a squall line weather event on July 12 , 2 005 was analyzed. This severe convection occurred under the background of traver se trough developing into vertical trough. When a traverse trough turned into ve rtical trough, the cold air pours from high altitudes, thus an instable stratification with upp erlayer dry and lowerlayer wet was formed, which was carried out by highlo w diffe rential effects of temperature. There was a strong upward airflow before squall line and a falling airflow with large momentum behind it. The surface wind behi nd squall line strengthened by relatively strong momentum transmitted from high to low. When squall line promulgated, old convergence line split or united , so new convergence line came into being consequently. When surface convergence inten sity became stronger, convective weather became more severe. Severe weather was loca ted behind disturbed convergence center. The convergence center was situated beh ind disturbed low pressure band and the high pressure stood before divergence center . There was a low pressure dangled after high pressure, and mesoscale high or low pr essure indicated a foreboding of convective weather.
Based on the automatic meteorological station, Doppler radar and NCEP reana lysis data of 1°×1° with 6 h interval, a squall line weather event on July 12 , 2 005 was analyzed. This severe convection occurred under the background of traver se trough developing into vertical trough. When a traverse trough turned into ve rtical trough, the cold air pours from high altitudes, thus an instable stratification with upp erlayer dry and lowerlayer wet was formed, which was carried out by highlo w diffe rential effects of temperature. There was a strong upward airflow before squall line and a falling airflow with large momentum behind it. The surface wind behi nd squall line strengthened by relatively strong momentum transmitted from high to low. When squall line promulgated, old convergence line split or united , so new convergence line came into being consequently. When surface convergence inten sity became stronger, convective weather became more severe. Severe weather was loca ted behind disturbed convergence center. The convergence center was situated beh ind disturbed low pressure band and the high pressure stood before divergence center . There was a low pressure dangled after high pressure, and mesoscale high or low pr essure indicated a foreboding of convective weather.
2009, 35(9):98-103.
DOI: 10.7519/j.issn.1000-0526.2009.9.013
Abstract:
The straw stalk cover may reduce the soil surface moisture evaporation , and raise the moisture content use efficiency. By taking the processing without straw stalk cov er as comparison, the observational experiments of the straw stalk cover in whe at and corn growing period were conducted from October 2005 to October 2007. T he experimental result indicates that, th e straw mulching led to changes of meteorological elements near the ground, the air temperature increased, while the vapor pressure near the ground dec re ased, the radiation to the ground was blocked by the straw mulching,the soil tem pe rature decreased, and the moisture content was increased, thus the water use eff icienc y was raised. Meanwhile the straw mulching increased the mature spike number of w heat, and increased the thousandgrain weights of wheat and maize. During the s traw mulching tests, the yield of wheat increased 8.7 percent, and the yield of maize increased 8.9 percent.
The straw stalk cover may reduce the soil surface moisture evaporation , and raise the moisture content use efficiency. By taking the processing without straw stalk cov er as comparison, the observational experiments of the straw stalk cover in whe at and corn growing period were conducted from October 2005 to October 2007. T he experimental result indicates that, th e straw mulching led to changes of meteorological elements near the ground, the air temperature increased, while the vapor pressure near the ground dec re ased, the radiation to the ground was blocked by the straw mulching,the soil tem pe rature decreased, and the moisture content was increased, thus the water use eff icienc y was raised. Meanwhile the straw mulching increased the mature spike number of w heat, and increased the thousandgrain weights of wheat and maize. During the s traw mulching tests, the yield of wheat increased 8.7 percent, and the yield of maize increased 8.9 percent.
2009, 35(9):104-111.
DOI: 10.7519/j.issn.1000-0526.2009.9.014
Abstract:
By analyzing the cloud characteristics during Meiyu periods from 2005 to 2008, t he heavy rain clouds were classified into three types, i.e. northtype, center type and southtype. The relations between the TBB of cloud top and correspon ding rainfall extreme and coverage of rainfall rate above 10 mm/h were studied. The results indicate that the northtype and southtype clouds have lots of co mmon feature, and show reverse features compared to the centertype. The positi on of heavy rainfall corresponding to the moving path of clouds revealed that du ring Meiyu periods the onehour variation and gradient of TBB were not obviously correlative. Then the relations between environmental factors and clouds were analyzed. And the resul ts show that the macroscopic features of cloud are obviously correlative with ve rtical velocity and water vapor flux. At last based on atmospheric circumstances the n eural network forecast equations of TBB of cloud top and strong rainfall in matu re phase of clouds were developed.
By analyzing the cloud characteristics during Meiyu periods from 2005 to 2008, t he heavy rain clouds were classified into three types, i.e. northtype, center type and southtype. The relations between the TBB of cloud top and correspon ding rainfall extreme and coverage of rainfall rate above 10 mm/h were studied. The results indicate that the northtype and southtype clouds have lots of co mmon feature, and show reverse features compared to the centertype. The positi on of heavy rainfall corresponding to the moving path of clouds revealed that du ring Meiyu periods the onehour variation and gradient of TBB were not obviously correlative. Then the relations between environmental factors and clouds were analyzed. And the resul ts show that the macroscopic features of cloud are obviously correlative with ve rtical velocity and water vapor flux. At last based on atmospheric circumstances the n eural network forecast equations of TBB of cloud top and strong rainfall in matu re phase of clouds were developed.
2009, 35(9):112-118.
DOI: 10.7519/j.issn.1000-0526.2009.9.015
Abstract:
The humancomputer interaction platform and element forecasting equation of 125 weather stations in Yunnan Province which included the elements of rainfall and temperature were set up by using factor selection and prediction equation. Comp arison tests indicated that vast majority of combined factors were more efficien t than single factor, and the equation forecasting quality by using combined fac tors was better than that by using single factor. The forecasting test results s howed that the precipitation forecasting in dry season had not been available ye t, but the forecasting on light rain, moderate rain and heavy rain in rainy seas on could guide forecasting operation to some extent. For the storm rainfall even ts which reflect the meso or small scale system, the forecasting effects were po or. Therefore, lots ofmeticulous works about factor selection need to be done. Furthermore, temperature prediction was valuable for reference, but it also needs to be improved further.
The humancomputer interaction platform and element forecasting equation of 125 weather stations in Yunnan Province which included the elements of rainfall and temperature were set up by using factor selection and prediction equation. Comp arison tests indicated that vast majority of combined factors were more efficien t than single factor, and the equation forecasting quality by using combined fac tors was better than that by using single factor. The forecasting test results s howed that the precipitation forecasting in dry season had not been available ye t, but the forecasting on light rain, moderate rain and heavy rain in rainy seas on could guide forecasting operation to some extent. For the storm rainfall even ts which reflect the meso or small scale system, the forecasting effects were po or. Therefore, lots ofmeticulous works about factor selection need to be done. Furthermore, temperature prediction was valuable for reference, but it also needs to be improved further.
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ISSN:1000-0526 CN:11-2282/P