ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 43,Issue 11,2017 Table of Contents
2017, 43(11):1309-1325.
DOI: 10.7519/j.issn.1000-0526.2017.11.001
Abstract:
Numerical simulation is carried out for a heavy rainfall event influenced by two typhoons to study the mesoscale vortex related to the event. The results show that: (1) the rainfall event was jointly influenced by continental high, Typhoon Fitow and Typhoon Danas. Obvious mesoscale vortex activity was found in the midtolower levels during the event. (2) Vertical vorticities related to the vortex started to develop from the lower level of atmosphere. At first, vorticities concentrated below 850 hPa, and then strengthened upward. Meanwhile, the vortex was growing in size and intensity, and finally became a deep mesoβ scale vortex accompanied by closed cyclonic circulation. (3) The terms of horizontal advection, vertical advection, convergence making and tilting of local vorticity tendency had different effects in different times and levels. The convergence making term was the main contributor to the midtolower level vorticity source. The vertical advection term was the main contributor to the upperlevel vorticity by transporting lower vorticity to the higher levels. The tilting effect had some influence on the development and movement of the vortex. (4) The latent heating effect of precipitation had important influence on the development and movement of the vortex. It changed thermodynamic condition and stability of the atmosphere. Therefore, it was responsible for the maintenance and development of the convergence and convection term of the local vorticity tendency.
Numerical simulation is carried out for a heavy rainfall event influenced by two typhoons to study the mesoscale vortex related to the event. The results show that: (1) the rainfall event was jointly influenced by continental high, Typhoon Fitow and Typhoon Danas. Obvious mesoscale vortex activity was found in the midtolower levels during the event. (2) Vertical vorticities related to the vortex started to develop from the lower level of atmosphere. At first, vorticities concentrated below 850 hPa, and then strengthened upward. Meanwhile, the vortex was growing in size and intensity, and finally became a deep mesoβ scale vortex accompanied by closed cyclonic circulation. (3) The terms of horizontal advection, vertical advection, convergence making and tilting of local vorticity tendency had different effects in different times and levels. The convergence making term was the main contributor to the midtolower level vorticity source. The vertical advection term was the main contributor to the upperlevel vorticity by transporting lower vorticity to the higher levels. The tilting effect had some influence on the development and movement of the vortex. (4) The latent heating effect of precipitation had important influence on the development and movement of the vortex. It changed thermodynamic condition and stability of the atmosphere. Therefore, it was responsible for the maintenance and development of the convergence and convection term of the local vorticity tendency.
2017, 43(11):1326-1338.
DOI: 10.7519/j.issn.1000-0526.2017.11.002
Abstract:
Based on the fourtimes daily CFSR global reanalysis data and the hourly observed national base station precipitation in the Central China region, we focused on one mesoscale convective vortex (MCV) weather process that occurred in Central China on 1 June 2015, and studied the characteristics of energy distribution and the mechanism that impacted the MCV during the enhancement phase by using the WRF simulation and energy diagnosis method. The results showed that the MCV was born in the central part of Hubei Province, then it moved towards Dabie Mountain in northeast of Hubei Province with enhancing intensity of MCV. By analyzing the precipitation distribution characteristics during the vortex enhancing stage, we found that the precipitation mainly focused on three regions at the early stage, then evolved into the distribution of zonal pattern. By analyzing meteorological conditions corresponding to the vortex enhancing stage, we found that latent heat caused by precipitation, the warm and wet southwest flow transport in the lower troposphere, the cold and dry air intrusion in the midlevel and a sharp increase of CAPE value were favorable for the enhancement of MCV intensity. On one hand, the convergence flow was strengthening in MCV peripheral section while the vortex was developing, resulting in the increase of perturbation kinetic energy. On the other hand, latent heat of condensation generated by precipitation resulted in the increase of perturbation available potential energy in middle level of troposphere. Then, the available potential energy was transferred upward by vertical air flow, hence it caused the enhancement of available potential energy in upper level of troposphere. With the method of calculating budget of the above two kinds of energy, we found that the energy producing items in the MCV enhancing stage were the conversion between perturbation available potential energy and perturbation kinetic energy which was triggered by pressure change between inside and outside of the MCV system, the effect of viscous force produced by basic air flow in different levels of troposphere, the conversion between zonal mean available potential energy and the perturbation kinetic energy caused by latent heat release as well as the input of perturbation kinetic energy from the outside of MCV system. However, the conversion between perturbation available potential energy and perturbation kinetic energy was the most contributable item for the development of MCV. By further analyzing its spatial distribution characteristics, we concluded that in the lower level and upper levels of troposphere, the forward conversion was propitious to strengthen the convergence and divergence flow, but in middlelevel and upperlevel troposphere, the reverse conversion was propitious to store the energy to satisfy the need of maintenance of vortex after it developed into maturity.
Based on the fourtimes daily CFSR global reanalysis data and the hourly observed national base station precipitation in the Central China region, we focused on one mesoscale convective vortex (MCV) weather process that occurred in Central China on 1 June 2015, and studied the characteristics of energy distribution and the mechanism that impacted the MCV during the enhancement phase by using the WRF simulation and energy diagnosis method. The results showed that the MCV was born in the central part of Hubei Province, then it moved towards Dabie Mountain in northeast of Hubei Province with enhancing intensity of MCV. By analyzing the precipitation distribution characteristics during the vortex enhancing stage, we found that the precipitation mainly focused on three regions at the early stage, then evolved into the distribution of zonal pattern. By analyzing meteorological conditions corresponding to the vortex enhancing stage, we found that latent heat caused by precipitation, the warm and wet southwest flow transport in the lower troposphere, the cold and dry air intrusion in the midlevel and a sharp increase of CAPE value were favorable for the enhancement of MCV intensity. On one hand, the convergence flow was strengthening in MCV peripheral section while the vortex was developing, resulting in the increase of perturbation kinetic energy. On the other hand, latent heat of condensation generated by precipitation resulted in the increase of perturbation available potential energy in middle level of troposphere. Then, the available potential energy was transferred upward by vertical air flow, hence it caused the enhancement of available potential energy in upper level of troposphere. With the method of calculating budget of the above two kinds of energy, we found that the energy producing items in the MCV enhancing stage were the conversion between perturbation available potential energy and perturbation kinetic energy which was triggered by pressure change between inside and outside of the MCV system, the effect of viscous force produced by basic air flow in different levels of troposphere, the conversion between zonal mean available potential energy and the perturbation kinetic energy caused by latent heat release as well as the input of perturbation kinetic energy from the outside of MCV system. However, the conversion between perturbation available potential energy and perturbation kinetic energy was the most contributable item for the development of MCV. By further analyzing its spatial distribution characteristics, we concluded that in the lower level and upper levels of troposphere, the forward conversion was propitious to strengthen the convergence and divergence flow, but in middlelevel and upperlevel troposphere, the reverse conversion was propitious to store the energy to satisfy the need of maintenance of vortex after it developed into maturity.
2017, 43(11):1339-1353.
DOI: 10.7519/j.issn.1000-0526.2017.11.003
Abstract:
Typhoons Ramasun and Kalmaegi along west route influenced Yunnan in 2014, where rainstorm distribution characteristics and the relative position of tropical cyclone had significant differences. The diagnosis results indicate that production of rainstorm distribution difference was mainly caused by the role of ambient flow field, which caused frontogenesis, then energy change, together with the effect of topo graphy. Particularly, lowlevel westerly (easterly) jet and convergence at south (north) side of Ramasun Typhoon center enhanced, causing generation of heavy rainfall. However, because water vapor content in lower layer of south side was higher than that of north side, the southwest Yunnan edge and Red River Valley windward slope had uplift effect, the rainfall amplified. Precipitation of south side was heavier than that of north side. In addition, thermodynamic properties differences of flow between south and north side caused frontogenesis. Frontal zone at lowlevel enhanced, beneficial to the development of severe precipitation on the northeastern side of Ramasun, southeast Yunnan. Furthermore, intersection of the easterly and westerly made divergence enhancing, then baroclinic available potential energy was released, which caused divergent wind kinetic energy to increase, and increase of divergent wind kinetic energy was relative to the change of precipitation peak caused by Ramasun. However, as Kalmaegi was influencing Yunnan, the center position of tropical cyclone and Bay of Bengal low pressure were both further south, and the southwest monsoon was also further south. The lowlevel jet at Kalmaegi northeastern side was the main factor influencing rainfall over Yunnan, and the intensity of lowlevel jet and zonal convergence at the jet front left quadrant were both stronger than that by Ramasun, so the precipitation of Kalmaegi northeastern side was more intense than that of Ramasun. In addition, the uplift effect of terrain played an important role in the generation of heavy rainstorm at south Yunnan edge. Moreover, frontal zone at lowlevel enhanced, which was also beneficial to the development of severe precipitation over northeast Yunnan at the northeastern side of Kalmaegi. Furthermore, increasing rotational wind kinetic energy was relative to precipitation peak, and the formation of the first precipitation peak in the edom of central Yunnan was related to baroclinic processes. However, at the second precipitation peak, south jet was strengthened on the east side of depression inverted trough, and rotational velocity field transported kinetic energy to heavy rain area, then kinetic energy over heavy rain area increased significantly, which was related to barotropic processes.
Typhoons Ramasun and Kalmaegi along west route influenced Yunnan in 2014, where rainstorm distribution characteristics and the relative position of tropical cyclone had significant differences. The diagnosis results indicate that production of rainstorm distribution difference was mainly caused by the role of ambient flow field, which caused frontogenesis, then energy change, together with the effect of topo graphy. Particularly, lowlevel westerly (easterly) jet and convergence at south (north) side of Ramasun Typhoon center enhanced, causing generation of heavy rainfall. However, because water vapor content in lower layer of south side was higher than that of north side, the southwest Yunnan edge and Red River Valley windward slope had uplift effect, the rainfall amplified. Precipitation of south side was heavier than that of north side. In addition, thermodynamic properties differences of flow between south and north side caused frontogenesis. Frontal zone at lowlevel enhanced, beneficial to the development of severe precipitation on the northeastern side of Ramasun, southeast Yunnan. Furthermore, intersection of the easterly and westerly made divergence enhancing, then baroclinic available potential energy was released, which caused divergent wind kinetic energy to increase, and increase of divergent wind kinetic energy was relative to the change of precipitation peak caused by Ramasun. However, as Kalmaegi was influencing Yunnan, the center position of tropical cyclone and Bay of Bengal low pressure were both further south, and the southwest monsoon was also further south. The lowlevel jet at Kalmaegi northeastern side was the main factor influencing rainfall over Yunnan, and the intensity of lowlevel jet and zonal convergence at the jet front left quadrant were both stronger than that by Ramasun, so the precipitation of Kalmaegi northeastern side was more intense than that of Ramasun. In addition, the uplift effect of terrain played an important role in the generation of heavy rainstorm at south Yunnan edge. Moreover, frontal zone at lowlevel enhanced, which was also beneficial to the development of severe precipitation over northeast Yunnan at the northeastern side of Kalmaegi. Furthermore, increasing rotational wind kinetic energy was relative to precipitation peak, and the formation of the first precipitation peak in the edom of central Yunnan was related to baroclinic processes. However, at the second precipitation peak, south jet was strengthened on the east side of depression inverted trough, and rotational velocity field transported kinetic energy to heavy rain area, then kinetic energy over heavy rain area increased significantly, which was related to barotropic processes.
2017, 43(11):1354-1363.
DOI: 10.7519/j.issn.1000-0526.2017.11.004
Abstract:
Utilizing conventional meteorological data, the NECP reanalysis data, spring southwest jet warm sector severe convection flow pattern of Fujian is established by using mesoscale convective weather analysis technique. From the perspectives of the four basic conditions for the development of severe convection, namely the instability, moisture, lifting and wind vertical shear, the characteristics of spring southwest jet warm sector severe convection flow pattern of Fujian are revealed. Southwest jet warm sector severe convection flow pattern is characterized by lowlevel strong warm and moist advection over middle and high level troposphere’s dry and cold air. The inversion, warm dry lid, midlow level sufficient water vapor, upper dry and low moist vertical profile, low level convergence and high level divergence are all favorable to the development of severe convection. The severe convective weather is often triggered by the front of surface, the convergence line of surface or 925 hPa, hot low pressure of surface, pulsation of southwest jet. The severe convective weather sustainably develops when the convection moves to the favorable envir onment by the guidance of southwest jet. Strong vertical wind shear with high CAPE is favorable for the sustainable development of convective storm.
Utilizing conventional meteorological data, the NECP reanalysis data, spring southwest jet warm sector severe convection flow pattern of Fujian is established by using mesoscale convective weather analysis technique. From the perspectives of the four basic conditions for the development of severe convection, namely the instability, moisture, lifting and wind vertical shear, the characteristics of spring southwest jet warm sector severe convection flow pattern of Fujian are revealed. Southwest jet warm sector severe convection flow pattern is characterized by lowlevel strong warm and moist advection over middle and high level troposphere’s dry and cold air. The inversion, warm dry lid, midlow level sufficient water vapor, upper dry and low moist vertical profile, low level convergence and high level divergence are all favorable to the development of severe convection. The severe convective weather is often triggered by the front of surface, the convergence line of surface or 925 hPa, hot low pressure of surface, pulsation of southwest jet. The severe convective weather sustainably develops when the convection moves to the favorable envir onment by the guidance of southwest jet. Strong vertical wind shear with high CAPE is favorable for the sustainable development of convective storm.
2017, 43(11):1364-1373.
DOI: 10.7519/j.issn.1000-0526.2017.11.005
Abstract:
Atmospheric dispersion conditions during the November Beijing AsiaPacific Economic Cooperation (APEC) meeting are analyzed and compared with those in October when four fog haze processes occurred. Stable weather index (SWI) during APEC was slightly smaller than that during the four fog haze processes in October. Numerical simulations show that emission control of Beijing and its surrounding areas is the main reason for a low level of aerosol concentrations in Beijing during APEC. Both the pollution transmission from neighboring regions and the diurnal variations of mountainvalley breeze under special terrain conditions contributed to the space distribution and time variation of pollution over Beijing. The north wind at night caused by topographic distribution eliminated pollution near ground obviously. Compared to heavy pollution weather, during the APEC, because of the low aerosol concentration and the corresponding enlarged diurnal variations of surface air temperature, the valley wind circulation in the Beijing area was obvious and hence enhanced daytime mixing layer height, producing more conductive conditions to spread the pollutants. Emission reduction led to low aerosol concentration which improved dispersion condition further, forming a negative feedback for pollutants to accumulate, contributing to “APEC blue” as well.
Atmospheric dispersion conditions during the November Beijing AsiaPacific Economic Cooperation (APEC) meeting are analyzed and compared with those in October when four fog haze processes occurred. Stable weather index (SWI) during APEC was slightly smaller than that during the four fog haze processes in October. Numerical simulations show that emission control of Beijing and its surrounding areas is the main reason for a low level of aerosol concentrations in Beijing during APEC. Both the pollution transmission from neighboring regions and the diurnal variations of mountainvalley breeze under special terrain conditions contributed to the space distribution and time variation of pollution over Beijing. The north wind at night caused by topographic distribution eliminated pollution near ground obviously. Compared to heavy pollution weather, during the APEC, because of the low aerosol concentration and the corresponding enlarged diurnal variations of surface air temperature, the valley wind circulation in the Beijing area was obvious and hence enhanced daytime mixing layer height, producing more conductive conditions to spread the pollutants. Emission reduction led to low aerosol concentration which improved dispersion condition further, forming a negative feedback for pollutants to accumulate, contributing to “APEC blue” as well.
2017, 43(11):1374-1382.
DOI: 10.7519/j.issn.1000-0526.2017.11.006
Abstract:
Based on CloudSat and CALIPSO data from 2007 to 2010, the cloud vertical structure (CVS) over Northeast China (39°-53°N, 119°-135°E) was analyzed. At first, the precipitation flag of CloudSat was validated by surface observation. Based on the validation, the parameters of CVS, especially that of precipitation cloud and nonprecipitation cloud, were analyzed. The results show that the distribution of cloud fraction profile is bimodal and shows significant diurnal and seasonal variations. Singlelayer cloud is the main type over Northeast China and most precipitation is generated by such cloud which is the main target of artificial rainfall enhancement. Most precipitation cloud is nimbostratus of low, cold, ice or mixed phase. Twolayer precipitation cloud is dominated by highlow or highmedium cold cloud, and most of the high cloud is cirrus or altostratus of ice phase while the low cloud is dominated by nimbostratus, stratocumulus or cumulus of mixed or ice phase. Significant differences of CVS between precipitation and non-precipitation are found. Precipitation is more likely to occur in the cloud with low cloud base (CB), thick cloud depth (CD), and thin cloud interlayer thickness (CIT). Meanwhile, the CB temperature of precipitation cloud is higher and varies significantly with seasons.
Based on CloudSat and CALIPSO data from 2007 to 2010, the cloud vertical structure (CVS) over Northeast China (39°-53°N, 119°-135°E) was analyzed. At first, the precipitation flag of CloudSat was validated by surface observation. Based on the validation, the parameters of CVS, especially that of precipitation cloud and nonprecipitation cloud, were analyzed. The results show that the distribution of cloud fraction profile is bimodal and shows significant diurnal and seasonal variations. Singlelayer cloud is the main type over Northeast China and most precipitation is generated by such cloud which is the main target of artificial rainfall enhancement. Most precipitation cloud is nimbostratus of low, cold, ice or mixed phase. Twolayer precipitation cloud is dominated by highlow or highmedium cold cloud, and most of the high cloud is cirrus or altostratus of ice phase while the low cloud is dominated by nimbostratus, stratocumulus or cumulus of mixed or ice phase. Significant differences of CVS between precipitation and non-precipitation are found. Precipitation is more likely to occur in the cloud with low cloud base (CB), thick cloud depth (CD), and thin cloud interlayer thickness (CIT). Meanwhile, the CB temperature of precipitation cloud is higher and varies significantly with seasons.
2017, 43(11):1383-1392.
DOI: 10.7519/j.issn.1000-0526.2017.11.007
Abstract:
In this paper, conventional meteorological data, AWS data and Doppler radar data are used to analyze the organization and formation mechanism, structure characteristics and evolution causation of a squall line in northern Henan on 29 July 2014. The results show that the squall line formed under the synoptic situation of pretrough. Before the convection, cold air invaded into the front of upperlevel trough and laid over the lowerlevel warm airflow in potential convection area to form a favorable mesoscale unstable stratification. The process can be divided into organizationevolution stage and regeneration stage. In the organizationevolution stage, eastmoving upperlevel trough and mesoscale topographic convergence line are the main trigger systems. The vertical circulation structure of the coexistence of front inflow and back outflow, the coexistence of lowerlevel convergence and upperlevel divergence, and the horizontal circulation structure of coexistence and derangement of ambient inflow and system outflow reflect the selforganization characteristics of the squall line. This positive feedback mechanism leads to develop and preserve for a long time. Moreover, convective cloud mergering of squall line and other storms is the important reason why its local organization structure boosts quickly. In regeneration stage, favorable thermodynamic condition and stratification characteristics, especially the vertical wind shear with stronger than moderate intensity are extremely advantageous to the development of organization structure of the squall line. Convective clouds merger where bow echo is intersected into squall line forming a mesoscale thunderstorm high near the ground. The convergence lifting motion formed by isallobaric wind and environment airflow in mesoscale wet region offered an important trigger mechanism for the regeneration of the squall line.
In this paper, conventional meteorological data, AWS data and Doppler radar data are used to analyze the organization and formation mechanism, structure characteristics and evolution causation of a squall line in northern Henan on 29 July 2014. The results show that the squall line formed under the synoptic situation of pretrough. Before the convection, cold air invaded into the front of upperlevel trough and laid over the lowerlevel warm airflow in potential convection area to form a favorable mesoscale unstable stratification. The process can be divided into organizationevolution stage and regeneration stage. In the organizationevolution stage, eastmoving upperlevel trough and mesoscale topographic convergence line are the main trigger systems. The vertical circulation structure of the coexistence of front inflow and back outflow, the coexistence of lowerlevel convergence and upperlevel divergence, and the horizontal circulation structure of coexistence and derangement of ambient inflow and system outflow reflect the selforganization characteristics of the squall line. This positive feedback mechanism leads to develop and preserve for a long time. Moreover, convective cloud mergering of squall line and other storms is the important reason why its local organization structure boosts quickly. In regeneration stage, favorable thermodynamic condition and stratification characteristics, especially the vertical wind shear with stronger than moderate intensity are extremely advantageous to the development of organization structure of the squall line. Convective clouds merger where bow echo is intersected into squall line forming a mesoscale thunderstorm high near the ground. The convergence lifting motion formed by isallobaric wind and environment airflow in mesoscale wet region offered an important trigger mechanism for the regeneration of the squall line.
2017, 43(11):1393-1401.
DOI: 10.7519/j.issn.1000-0526.2017.11.008
Abstract:
Based on the monthly mean temperature data at 284 China stations and NCEP/NCAR reanalysis dataset, the dominant modes of three months’ temperature in summer and their associated circulation anomalies are investigated with empirical orthogonal function (EOF), composite analysis and other statistical methods. The three dominant modes can be calculated from EOF. The first mode (EOF1) depicts a uniform mode (UM) from north to south over China. The second mode (EOF2) depicts a tripole mode (TM) between Inner Mongolia, North China, South China and the middlelower reaches of the Yangtze River. The third mode (EOF3) depicts a dipole mode between the north part and south part to the Yangtze River. The major circulation characteristics related with the three modes are different. UM is attributed to the equivalent barotropic atmosphere feature. The potential height anomaly shows the same tendency from the lower troposphere to the lower stratosphere over East Asia. TM is attributed to the East AsiaPacific (EAP) teleconnection pattern and the stratosphere height field anomaly in early spring can be used as a precursor for summer TM. The location and intensity of the West Pacific subtropical high and northeast cold vortex are very important to DM.
Based on the monthly mean temperature data at 284 China stations and NCEP/NCAR reanalysis dataset, the dominant modes of three months’ temperature in summer and their associated circulation anomalies are investigated with empirical orthogonal function (EOF), composite analysis and other statistical methods. The three dominant modes can be calculated from EOF. The first mode (EOF1) depicts a uniform mode (UM) from north to south over China. The second mode (EOF2) depicts a tripole mode (TM) between Inner Mongolia, North China, South China and the middlelower reaches of the Yangtze River. The third mode (EOF3) depicts a dipole mode between the north part and south part to the Yangtze River. The major circulation characteristics related with the three modes are different. UM is attributed to the equivalent barotropic atmosphere feature. The potential height anomaly shows the same tendency from the lower troposphere to the lower stratosphere over East Asia. TM is attributed to the East AsiaPacific (EAP) teleconnection pattern and the stratosphere height field anomaly in early spring can be used as a precursor for summer TM. The location and intensity of the West Pacific subtropical high and northeast cold vortex are very important to DM.
2017, 43(11):1402-1409.
DOI: 10.7519/j.issn.1000-0526.2017.11.009
Abstract:
Based on the revised national standard of grades of meteorological drought, daily meteorological drought composite index (MCI) from 825 stations in China from 1961 to 2015 are calculated with historic daily rainfall, mean air temperature, maximum air temperature, minimum air temperature and wind speed. Spatiotemporal distribution and changes of drought days over China and six regions such as Northeast China, North China, eastern Northwest China, Southwest China, middle and lower reaches of the Yangtze River, South China are analyzed using the calculated daily MCI. Drought disaster rate of each province and changes of affected areas and damaged areas in China are also analyzed with disaster data from 1961 to 2015. The results show that annual drought days in North China, Huanghuai, eastern Northwest China, western Northeast China, western South China, most parts of Southwest China and Inner Mongolia are more than 40 days. Especially in most parts of North China, northeastern Huanghuai and northern Shaanxi, most parts of eastern Gansu and Ningxia, annual drought days are more than 60 days. The maximum dry spells in southern Hebei, most parts of Ningxia, northern and western Xinjiang, central and southern Yunnan, southern Hainan are more than 210 days. But in middle and lower reaches of the Yangtze River, eastern South China, central Northwest China, eastern Northeast China, annual drought days are less than 40 days. The drought mainly occurs in late spring, summer and autumn in Northeast China and North China, in late spring and early summer in eastern Northwest China, in midsummer and autumn in middle and lower reaches of the Yangtze River, in autumn and winter in South China and in winter and spring in Southwest China. Annual drought days are in an overall increasing trend over China from 1961 to 2015, especially in southeastern Gansu, Ningxia, Shaanxi, southern Shanxi, western Henan, northwestern Hubei, central and western Guizhou, central and western Yunnan. But in central and western Northwest China, central and eastern Northeast China, most parts of Jiangnan and South China, central and western Tibet and Inner Mongolia, annual drought days have decreasing trend. Annual drought affected areas and damaged areas in China have an overall increasing trend from 1951 to 2015, but they are both decreasing in the recent years.
Based on the revised national standard of grades of meteorological drought, daily meteorological drought composite index (MCI) from 825 stations in China from 1961 to 2015 are calculated with historic daily rainfall, mean air temperature, maximum air temperature, minimum air temperature and wind speed. Spatiotemporal distribution and changes of drought days over China and six regions such as Northeast China, North China, eastern Northwest China, Southwest China, middle and lower reaches of the Yangtze River, South China are analyzed using the calculated daily MCI. Drought disaster rate of each province and changes of affected areas and damaged areas in China are also analyzed with disaster data from 1961 to 2015. The results show that annual drought days in North China, Huanghuai, eastern Northwest China, western Northeast China, western South China, most parts of Southwest China and Inner Mongolia are more than 40 days. Especially in most parts of North China, northeastern Huanghuai and northern Shaanxi, most parts of eastern Gansu and Ningxia, annual drought days are more than 60 days. The maximum dry spells in southern Hebei, most parts of Ningxia, northern and western Xinjiang, central and southern Yunnan, southern Hainan are more than 210 days. But in middle and lower reaches of the Yangtze River, eastern South China, central Northwest China, eastern Northeast China, annual drought days are less than 40 days. The drought mainly occurs in late spring, summer and autumn in Northeast China and North China, in late spring and early summer in eastern Northwest China, in midsummer and autumn in middle and lower reaches of the Yangtze River, in autumn and winter in South China and in winter and spring in Southwest China. Annual drought days are in an overall increasing trend over China from 1961 to 2015, especially in southeastern Gansu, Ningxia, Shaanxi, southern Shanxi, western Henan, northwestern Hubei, central and western Guizhou, central and western Yunnan. But in central and western Northwest China, central and eastern Northeast China, most parts of Jiangnan and South China, central and western Tibet and Inner Mongolia, annual drought days have decreasing trend. Annual drought affected areas and damaged areas in China have an overall increasing trend from 1951 to 2015, but they are both decreasing in the recent years.
2017, 43(11):1410-1419.
DOI: 10.7519/j.issn.1000-0526.2017.11.010
Abstract:
This paper analyzes the factors which led to landslide in Guzhang of Hunan Province on 17 July 2016. Based on the GIS space analysis tools, all geological factors contributing to the Guzhang landslide are analyzed by using the geological disaster investigation data with scale of 150000, distribution of road and railway as well as the net of small rivers, river banks and aspect of landslides. Using the module of Bayesian inference, and Gibbs Sampling (BUGS), the parameters of ID curves are estimated, and the effective rainfall which led to the landslides of Guzhang area is studied. Combining the previous disaster investigation of Guzhang landslides with the analysis result, we get a detailed cause of Guzhang landslides, which is helpful in warning landslides there in future. The analysis about the landslide factor of Guzhang landslide shows us that the extremely heavy rains are the main cause for the landslides, the badly cutting slope condition caused by traffic construction, sensitive slope interval and the high risk of the aspect to the landslide are also the key factors for the 17 July landslide at Morong of Guzhang. The research methods and findings are conductive to the future warning of geological disasters.
This paper analyzes the factors which led to landslide in Guzhang of Hunan Province on 17 July 2016. Based on the GIS space analysis tools, all geological factors contributing to the Guzhang landslide are analyzed by using the geological disaster investigation data with scale of 150000, distribution of road and railway as well as the net of small rivers, river banks and aspect of landslides. Using the module of Bayesian inference, and Gibbs Sampling (BUGS), the parameters of ID curves are estimated, and the effective rainfall which led to the landslides of Guzhang area is studied. Combining the previous disaster investigation of Guzhang landslides with the analysis result, we get a detailed cause of Guzhang landslides, which is helpful in warning landslides there in future. The analysis about the landslide factor of Guzhang landslide shows us that the extremely heavy rains are the main cause for the landslides, the badly cutting slope condition caused by traffic construction, sensitive slope interval and the high risk of the aspect to the landslide are also the key factors for the 17 July landslide at Morong of Guzhang. The research methods and findings are conductive to the future warning of geological disasters.
LI Xiufen
,
MA Shuqing
,
JIANG Lixia
,
JI Ruipeng
,
LIU Jing
,
LI Xinghua
,
HAN Junjie
,
ZHOU Yongji
2017, 43(11):1420-1430.
DOI: 10.7519/j.issn.1000-0526.2017.11.011
Abstract:
monitoring, early warning and assessment, and its applicability is related to the quality of agricultural meteorological service and the effect of disaster prevention and mitigation. By using daily meteorological data, soil relative moisture data, spring maize growth and development observation data and maize yield data in 1981-2012 from 31 spring maize representative stations in Northeast China, the application effect of soil moistrue and water deficit index indicators for spring maize drought grade are tested, and their applicability differences are compared. By using the data from 2013 to 2016 in Heilongjiang Province, an example is analyzed. The results show that the soil moisture indicator and the water deficit index indicator are suitable for determining spring maize drought grades in different growth stages in Northeast China and they have good consistency. The same proportion of the two sets of indicators to determine the drought grade of sping maize is about 75%. The same and basically same proportion is about 95%. Identification effect of the two sets of indicators are good on the historic and recent maize drought events, the accuracy of drought identification by soil moisture indicator and water deficit index are above 80% and 75% respectively, and the identification effect of soil moisture indicator is better. The suitability of the two sets of indicators in early and mid stage is slightly better than that in later stage. The application effect in three provinces in Northeast China is better than that in East of Inner Mongolia. In some drought years, the drought grade determined by water deficit index is higher, so when the results determined by the two sets of indicators are different, it should be based on the results of the soil relative moisture indicator.
monitoring, early warning and assessment, and its applicability is related to the quality of agricultural meteorological service and the effect of disaster prevention and mitigation. By using daily meteorological data, soil relative moisture data, spring maize growth and development observation data and maize yield data in 1981-2012 from 31 spring maize representative stations in Northeast China, the application effect of soil moistrue and water deficit index indicators for spring maize drought grade are tested, and their applicability differences are compared. By using the data from 2013 to 2016 in Heilongjiang Province, an example is analyzed. The results show that the soil moisture indicator and the water deficit index indicator are suitable for determining spring maize drought grades in different growth stages in Northeast China and they have good consistency. The same proportion of the two sets of indicators to determine the drought grade of sping maize is about 75%. The same and basically same proportion is about 95%. Identification effect of the two sets of indicators are good on the historic and recent maize drought events, the accuracy of drought identification by soil moisture indicator and water deficit index are above 80% and 75% respectively, and the identification effect of soil moisture indicator is better. The suitability of the two sets of indicators in early and mid stage is slightly better than that in later stage. The application effect in three provinces in Northeast China is better than that in East of Inner Mongolia. In some drought years, the drought grade determined by water deficit index is higher, so when the results determined by the two sets of indicators are different, it should be based on the results of the soil relative moisture indicator.
2017, 43(11):1431-1438.
DOI: 10.7519/j.issn.1000-0526.2017.11.012
Abstract:
Selecting two heavy pollution weather processes cover Hubei on 25 December 2015 and 18 January 2016, and using FY3A (B)/MERSI satellite data and weather observation, environmental monitoring data, this paper carries out the study of haze remote sensing identification by digitizing the image color processing technology and technology of reflectance threshold of visible and near infrared channels in Hubei area. The results show that haze can be distinguished by the color composition of red, green and blue channels. With full visible bands, the color of haze is mainly graywhite, slightly darker than the surrounding cloud area; with visible, infrared and near infrared bands, the color of haze is mainly purple and purple grey, and the cloud class recognition is more fine; and with enhanced display of visible and near infrared bands, the color of haze is mainly purple grey, which can be distinguished from the clear sky surface and cloud area, but easy to be confused with the thin cirrus composed of small particles, so it needs to be eliminated through the blackbody brightness temperature. With the help of TBB of infrared channel and the visible reflectance index, haze can be identified from the clear sky and thick cloud area, but difficult to distinguish from mist. The problem can be solved by adding the reflectance of near infrared channel which is sensitive to the effective particle radius. Finally the results are verified through the observation of ground weather phenomena.
Selecting two heavy pollution weather processes cover Hubei on 25 December 2015 and 18 January 2016, and using FY3A (B)/MERSI satellite data and weather observation, environmental monitoring data, this paper carries out the study of haze remote sensing identification by digitizing the image color processing technology and technology of reflectance threshold of visible and near infrared channels in Hubei area. The results show that haze can be distinguished by the color composition of red, green and blue channels. With full visible bands, the color of haze is mainly graywhite, slightly darker than the surrounding cloud area; with visible, infrared and near infrared bands, the color of haze is mainly purple and purple grey, and the cloud class recognition is more fine; and with enhanced display of visible and near infrared bands, the color of haze is mainly purple grey, which can be distinguished from the clear sky surface and cloud area, but easy to be confused with the thin cirrus composed of small particles, so it needs to be eliminated through the blackbody brightness temperature. With the help of TBB of infrared channel and the visible reflectance index, haze can be identified from the clear sky and thick cloud area, but difficult to distinguish from mist. The problem can be solved by adding the reflectance of near infrared channel which is sensitive to the effective particle radius. Finally the results are verified through the observation of ground weather phenomena.
2017, 43(11):1439-1445.
DOI: 10.7519/j.issn.1000-0526.2017.11.013
Abstract:
The performance of mediumrange forecasts is verified and compared for the T639, ECMWF and Japan models from June to August 2017. The results show that all of the three models could well predict the variation and adjustment of the atmospheric circulation over middle and high latitudes in Eurasia, of which ECMWF model performs the best. ECMWF and T639 models have good performance in predicting activity of western Pacific subtropical high (WPSH), and the ECMWF model shows better skill. The prediction bias of the west ridge of WPSH reduces from early summer to late summer. The T639 and ECMWF models underestimates the temperature over most of China at 850 hPa, and the JP model overestimates the temperature over most of China. In southern China, three models have smaller bias of temperature prediction than that in northern China. ECMWF model has better performance than T639 and Japan models. As far as Typhoon Hato (1713) is concerned, ECMWF model performs better in predicting the track, intensity and landing position, although the predicted strength is weaker. The T639 model shows a poor skill in the prediction of Typhoon Hato.
The performance of mediumrange forecasts is verified and compared for the T639, ECMWF and Japan models from June to August 2017. The results show that all of the three models could well predict the variation and adjustment of the atmospheric circulation over middle and high latitudes in Eurasia, of which ECMWF model performs the best. ECMWF and T639 models have good performance in predicting activity of western Pacific subtropical high (WPSH), and the ECMWF model shows better skill. The prediction bias of the west ridge of WPSH reduces from early summer to late summer. The T639 and ECMWF models underestimates the temperature over most of China at 850 hPa, and the JP model overestimates the temperature over most of China. In southern China, three models have smaller bias of temperature prediction than that in northern China. ECMWF model has better performance than T639 and Japan models. As far as Typhoon Hato (1713) is concerned, ECMWF model performs better in predicting the track, intensity and landing position, although the predicted strength is weaker. The T639 model shows a poor skill in the prediction of Typhoon Hato.
2017, 43(11):1446-1452.
DOI: 10.7519/j.issn.1000-0526.2017.11.014
Abstract:
The main characteristics of the general atmospheric circulation in August 2017 are as follows. There was one polar vortex center in the Northern Hemisphere, stronger than usual. The circulation in Eurasian middlehigh latitudes showed a multiwave pattern. The subtropical high lay westward and its intensity in northwestern Pacific was weaker than its average state during the corresponding period of normal years. The monthly mean precipitation amount was 126.6 mm, which is more than normal by 20%, while the monthly mean temperature is 21.4℃, being higher than normal value by 0.6℃. Eight regional torrential rainfall events with extreme daily precipitation records happened in August. Five tropical cyclones were active over the northwestern Pacific and the South China Sea, and Typhoons Hato (1713) and Pakhar (1714) made landfall along the coastal areas over Pearl River Delta of China. Largescale high temperature weather occurred all over the southern part of China.
The main characteristics of the general atmospheric circulation in August 2017 are as follows. There was one polar vortex center in the Northern Hemisphere, stronger than usual. The circulation in Eurasian middlehigh latitudes showed a multiwave pattern. The subtropical high lay westward and its intensity in northwestern Pacific was weaker than its average state during the corresponding period of normal years. The monthly mean precipitation amount was 126.6 mm, which is more than normal by 20%, while the monthly mean temperature is 21.4℃, being higher than normal value by 0.6℃. Eight regional torrential rainfall events with extreme daily precipitation records happened in August. Five tropical cyclones were active over the northwestern Pacific and the South China Sea, and Typhoons Hato (1713) and Pakhar (1714) made landfall along the coastal areas over Pearl River Delta of China. Largescale high temperature weather occurred all over the southern part of China.
Mobile website
® 2024 All Rights Reserved
Supported by:Beijing E-Tiller Technology Development Co., Ltd.
ISSN:1000-0526 CN:11-2282/P