ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 47,Issue 4,2021 Table of Contents
2021, 47(4):389-397.
DOI: 10.7519/j.issn.1000-0526.2021.04.001
Abstract:
Based on the raindrop disdrometer data of 42 stations in Shanghai, Zhejiang, Jiangsu and Anhui during the precipitation process of Typhoon Rumbia （1808）, this paper compares and analyzes the difference between the radar reflectivity calculated from raindrop size distribution and the actual measurement based on radar, and the difference between the raindrop size distribution inversion rain rate and gauge actual observation. The ZR relationship fitting is carried out to explore the relationship between radar echo and the precipitation intensity of typhoon. Two kinds of ZR relations are used for comparative analysis of precipitation estimation so as to explore the application effect of raindrop size distribution. The main results are as follows. The radar reflectivity factor of raindrop disdrometers inversion is consistent with radar observation, with correlation coefficient being 0.96, and the former is slightly smaller than the latter. Comparison suggests that the rainfall intensity observed by rain gauge and the precipitation intensity calculated by raindrop disdrometer data have the almost same varying trend, and their correlation coefficient is 0.94. However, the values from some instruments have great differences in some regions, which may be caused by the system error of the instrument itself in the region, and also by the influence of typhoon. When raindrops fall to the ground, the falling speed is fast so that they are easy to break, overlap, etc. This could cause some errors in the diameter and number of drops. In addition, the fitting formula of precipitation echo and intensity of the cloud system around the Typhoon Rumbia is Z=188.85R1.42. The estimation effect by using this relationship is better than using the default relationship Z=300R1.4, increasing by about 17% of precipitation estimation.
Based on the raindrop disdrometer data of 42 stations in Shanghai, Zhejiang, Jiangsu and Anhui during the precipitation process of Typhoon Rumbia （1808）, this paper compares and analyzes the difference between the radar reflectivity calculated from raindrop size distribution and the actual measurement based on radar, and the difference between the raindrop size distribution inversion rain rate and gauge actual observation. The ZR relationship fitting is carried out to explore the relationship between radar echo and the precipitation intensity of typhoon. Two kinds of ZR relations are used for comparative analysis of precipitation estimation so as to explore the application effect of raindrop size distribution. The main results are as follows. The radar reflectivity factor of raindrop disdrometers inversion is consistent with radar observation, with correlation coefficient being 0.96, and the former is slightly smaller than the latter. Comparison suggests that the rainfall intensity observed by rain gauge and the precipitation intensity calculated by raindrop disdrometer data have the almost same varying trend, and their correlation coefficient is 0.94. However, the values from some instruments have great differences in some regions, which may be caused by the system error of the instrument itself in the region, and also by the influence of typhoon. When raindrops fall to the ground, the falling speed is fast so that they are easy to break, overlap, etc. This could cause some errors in the diameter and number of drops. In addition, the fitting formula of precipitation echo and intensity of the cloud system around the Typhoon Rumbia is Z=188.85R1.42. The estimation effect by using this relationship is better than using the default relationship Z=300R1.4, increasing by about 17% of precipitation estimation.
2021, 47(4):398-411.
DOI: 10.7519/j.issn.1000-0526.2021.04.002
Abstract:
In this paper, RMAPS-ST prediction results, Doppler weather radar data, surface dense automatic station data were used to analyze a localized sudden short-term meso-γ scale rainstorm which occurred in Tianjin on 22 July 2018. Results show that the rainstorm was a local heavy precipitation process caused by an isolated urban storm which occurred within the control range of 500 hPa subtropical high. It featured a small range (less than 20 km), a short life circle (1-2 h), severe precipitation intensity (62.4 mm·h-1) and complex mesoscale boundary layer environment. The rainstorm happened when the boundary of the cold pool of the upstream precipitation system was still far from the urban area of Tianjin, and it was induced by the combined action of the urban heat island, the weak cold air ahead of the outflow of the upstream cold pool, the systematic northeast wind, and the mesoscale sea breeze which gradually formed in the afternoon. The result of the underlying surface horizontal thermal difference and the corresponding surface energy balance contributed to the formation of significant heat island effect in downtown Tianjin with 2-4℃ heat island intensity, and consequently, the formation and development of the urban heat island warm low pressure accompanied by the heat island effect led to the formation of a mesoscale convergence center in the downtown. Moreover, the pressure gradient between the mesoscale high pressure generated by the upstream precipitation (upstream precipitation area) and the warm low pressure in downtown Tianjin (downstream non-precipitation area) resulted in a northern wind branch, which surpassed the outflow boundary of the cold pool and reached the urban area of Tianjin in advance. This weak cold air in the boundary layer combined with the systematic northeast wind and sea breeze, and converged towards the urban area under the effect of the urban island warm low pressure, which further enhanced the intensity and maintenance time of the urban convergence center. Two asymmetric mesoscale secondary circulations were formed along the vertical direction of the urban area in zonal and meridional directions with ascending branch located in the downtown area of Tianjin. The local heat accumulation accompanied by the heat island effect and the water vapor concentration caused by eastbound migration of mesoscale frontal area, jointly caused the development of local high humidity and energy region in downtown and the increment of vertical instability, which provided favorable mesoscale environmental conditions for the occurrence of the short-time local rainstorm.
In this paper, RMAPS-ST prediction results, Doppler weather radar data, surface dense automatic station data were used to analyze a localized sudden short-term meso-γ scale rainstorm which occurred in Tianjin on 22 July 2018. Results show that the rainstorm was a local heavy precipitation process caused by an isolated urban storm which occurred within the control range of 500 hPa subtropical high. It featured a small range (less than 20 km), a short life circle (1-2 h), severe precipitation intensity (62.4 mm·h-1) and complex mesoscale boundary layer environment. The rainstorm happened when the boundary of the cold pool of the upstream precipitation system was still far from the urban area of Tianjin, and it was induced by the combined action of the urban heat island, the weak cold air ahead of the outflow of the upstream cold pool, the systematic northeast wind, and the mesoscale sea breeze which gradually formed in the afternoon. The result of the underlying surface horizontal thermal difference and the corresponding surface energy balance contributed to the formation of significant heat island effect in downtown Tianjin with 2-4℃ heat island intensity, and consequently, the formation and development of the urban heat island warm low pressure accompanied by the heat island effect led to the formation of a mesoscale convergence center in the downtown. Moreover, the pressure gradient between the mesoscale high pressure generated by the upstream precipitation (upstream precipitation area) and the warm low pressure in downtown Tianjin (downstream non-precipitation area) resulted in a northern wind branch, which surpassed the outflow boundary of the cold pool and reached the urban area of Tianjin in advance. This weak cold air in the boundary layer combined with the systematic northeast wind and sea breeze, and converged towards the urban area under the effect of the urban island warm low pressure, which further enhanced the intensity and maintenance time of the urban convergence center. Two asymmetric mesoscale secondary circulations were formed along the vertical direction of the urban area in zonal and meridional directions with ascending branch located in the downtown area of Tianjin. The local heat accumulation accompanied by the heat island effect and the water vapor concentration caused by eastbound migration of mesoscale frontal area, jointly caused the development of local high humidity and energy region in downtown and the increment of vertical instability, which provided favorable mesoscale environmental conditions for the occurrence of the short-time local rainstorm.
2021, 47(4):412-423.
DOI: 10.7519/j.issn.1000-0526.2021.04.003
Abstract:
Based on station observations (surface observations and upper-air soundings at weather stations and precipitation observations at regional stations), FY-2D infrared images, water vapor images and NCEP reanalysis data with the resolution of 1°×1°, combined with water vapor flux diagnosis and a backward trajectory model, an extreme rainstorm process which occurred in the arid region of western Hexi Corridor during 15-16 June 2011 was analyzed to study the transport mechanism of water vapor and its budget in the process. The results are as follows. The western Hexi Corridor was affected by the plateau vortex center formed from the western part of warm high-pressure ridge which ran northwest-southeast from western Inner Mongolia to Hetao Area. The plateau vortex center with 200-400 km scale remained stable over the rainstorm area for more than 12 hours, forming good dynamic conditions. The humidity increased and the temperature decreased in the lower troposphere. The cold air invaded from the southern plateau vortex in middle layer. The atmosphere was in a weakly unstable state. The convergence of surface wind speed and the effect of terrain upwind slope triggered local convective weather. The water vapor needed by rainstorm was mainly from the west wind flow and the east wind flow bypassed the plateau, and the latter brought the most water vapor with its contribution rate during rainstorm as high as 84.6%. Further more, the water vapor from two channels were both the most pronounced in the middle and low layer of the tro-posphere. The formation of anomalous easterly airflow in central Gansu at 500 hPa and 700 hPa was important for water vapor transport and convergence in the rainstorm area. The average net input intensity of water vapor during the rainstorm period was 2.73 times of that the pre-rainstorm period. The low vortex center in the middle troposphere, the convergence of wind speed and direction in the lower troposphere, and the convergence of terrain caused the 550 hPa, 700 hPa, and 800 hPa three-layer water vapor convergence center with 200-400 km scale. The atmospheric precipitable water in the rainstorm center was as high as 34 mm, which was more than 2 times the summer average.
Based on station observations (surface observations and upper-air soundings at weather stations and precipitation observations at regional stations), FY-2D infrared images, water vapor images and NCEP reanalysis data with the resolution of 1°×1°, combined with water vapor flux diagnosis and a backward trajectory model, an extreme rainstorm process which occurred in the arid region of western Hexi Corridor during 15-16 June 2011 was analyzed to study the transport mechanism of water vapor and its budget in the process. The results are as follows. The western Hexi Corridor was affected by the plateau vortex center formed from the western part of warm high-pressure ridge which ran northwest-southeast from western Inner Mongolia to Hetao Area. The plateau vortex center with 200-400 km scale remained stable over the rainstorm area for more than 12 hours, forming good dynamic conditions. The humidity increased and the temperature decreased in the lower troposphere. The cold air invaded from the southern plateau vortex in middle layer. The atmosphere was in a weakly unstable state. The convergence of surface wind speed and the effect of terrain upwind slope triggered local convective weather. The water vapor needed by rainstorm was mainly from the west wind flow and the east wind flow bypassed the plateau, and the latter brought the most water vapor with its contribution rate during rainstorm as high as 84.6%. Further more, the water vapor from two channels were both the most pronounced in the middle and low layer of the tro-posphere. The formation of anomalous easterly airflow in central Gansu at 500 hPa and 700 hPa was important for water vapor transport and convergence in the rainstorm area. The average net input intensity of water vapor during the rainstorm period was 2.73 times of that the pre-rainstorm period. The low vortex center in the middle troposphere, the convergence of wind speed and direction in the lower troposphere, and the convergence of terrain caused the 550 hPa, 700 hPa, and 800 hPa three-layer water vapor convergence center with 200-400 km scale. The atmospheric precipitable water in the rainstorm center was as high as 34 mm, which was more than 2 times the summer average.
2021, 47(4):424-438.
DOI: 10.7519/j.issn.1000-0526.2021.04.004
Abstract:
The evolution characteristics of radar echo and environmental parameters of the severe convective storm in central Yunnan on 23 August 2017 are analyzed using conventional observation data, automatic weather station data, Doppler radar data, NCEP (1°×1°) 6 h reanalysis data. The main conclusions are as follows. This severe convective storm occurred under the background of strong unstable conditions caused by the front side of typhoon depression system moving westward and the rear side of mid and high latitude cold trough. Surface convergence lines and strong vertical wind shear were conducive to the maintenance and enhancement of convective storms. The severe convective storms were influenced significantly by the topography and six supercells or similar supercells were induced during the evolution of convective storms. The strong centers of three hail supercells climbed along the terrain, while the non-hail and small hail supercells descended along the terrain 10 minutes before the supercells developed to maturity. The six supercells or similar supercells had characteristics of mesocyclone or meso-γ scale vortex. Hails occurred when the maximum velocity to rotation value in the supercell exceeded 10 m·s-1. The velocity at elevation 2.4°-3.4° reached the mesocyclone standard when the diameter of hails was bigger than 15 mm. There were the characteristics of higher reflectivity centroid point, echo nuclear tilting forward, weak echo zone, the echo wall and three-body scatter for supercells with 15-20 mm hail particles. In addition, the radial velocity showed the following characteristics. The zero velocity line tilted back, the height of the convergence zone exceeded -10℃ layers of supercooled water zone, a strong divergence zone appeared at the top, the maximum echo intensity of the -20-0℃ layer exceeded 55 dBz, the thickness of the 50 dBz echo was more than 6 km, and the density of vertically accumulated liquid water content (VIL) was larger than 2.2 g·m-3. The echo nuclear shows an upright shape, the characteristics of overhanging echoes were not significant, the height of the convergence zone was low and the thickness of the divergence zone was higher than that of the convergence zone, for supercells of non-hail and 5-8 mm small hail particles. The maximum echo intensity of different isothermal layers showed little difference, but the 50 dBz echo thickness was less than 6 km, and the VIL density was less than 2.2 g·m-3.
The evolution characteristics of radar echo and environmental parameters of the severe convective storm in central Yunnan on 23 August 2017 are analyzed using conventional observation data, automatic weather station data, Doppler radar data, NCEP (1°×1°) 6 h reanalysis data. The main conclusions are as follows. This severe convective storm occurred under the background of strong unstable conditions caused by the front side of typhoon depression system moving westward and the rear side of mid and high latitude cold trough. Surface convergence lines and strong vertical wind shear were conducive to the maintenance and enhancement of convective storms. The severe convective storms were influenced significantly by the topography and six supercells or similar supercells were induced during the evolution of convective storms. The strong centers of three hail supercells climbed along the terrain, while the non-hail and small hail supercells descended along the terrain 10 minutes before the supercells developed to maturity. The six supercells or similar supercells had characteristics of mesocyclone or meso-γ scale vortex. Hails occurred when the maximum velocity to rotation value in the supercell exceeded 10 m·s-1. The velocity at elevation 2.4°-3.4° reached the mesocyclone standard when the diameter of hails was bigger than 15 mm. There were the characteristics of higher reflectivity centroid point, echo nuclear tilting forward, weak echo zone, the echo wall and three-body scatter for supercells with 15-20 mm hail particles. In addition, the radial velocity showed the following characteristics. The zero velocity line tilted back, the height of the convergence zone exceeded -10℃ layers of supercooled water zone, a strong divergence zone appeared at the top, the maximum echo intensity of the -20-0℃ layer exceeded 55 dBz, the thickness of the 50 dBz echo was more than 6 km, and the density of vertically accumulated liquid water content (VIL) was larger than 2.2 g·m-3. The echo nuclear shows an upright shape, the characteristics of overhanging echoes were not significant, the height of the convergence zone was low and the thickness of the divergence zone was higher than that of the convergence zone, for supercells of non-hail and 5-8 mm small hail particles. The maximum echo intensity of different isothermal layers showed little difference, but the 50 dBz echo thickness was less than 6 km, and the VIL density was less than 2.2 g·m-3.
2021, 47(4):439-449.
DOI: 10.7519/j.issn.1000-0526.2021.04.005
Abstract:
Based on hourly observational datasets from 84 national automatic weather stations and 6 h ERA-Interim reanalysis data at Sichuan Basin between May and September during 2007-2017, this study investigates the ambient conditions, such as thermodynamic variables, water vapor and vertical wind shear, and contrasts characteristics of convective parameters of the occurrence and development of flash-rain under different intensities. Compared with ordinary short-time severe precipitation, extreme flash-rain has relatively higher lifting condensation level (LCL), higher level of free convection (LFC) and higher equilibrium level (EL), which can be used to effectively distinguish extreme and ordinary flash-rain. About 75% of extreme and ordinary flash-rain events occur in the ambient background with EL higher than 258.6 hPa and 658.2 hPa, respectively. The values of convective available potential energy (CAPE) and convective inhibition (CIN) are larger in extreme flash-rain events. About 50% of extreme and ordinary flash-rain occurrence needs CAPE values greater than 792.5 J·kg-1 and 451.9 J·kg-1, respectively. The bigger difference of potential pseudo-equivalent temperature between 850 hPa and 500 hPa (θse850-θse500) is better for extreme flash-rain, and 10℃ can be the threshold value to judge extreme and ordinary flash-rain. The precipitable water (PW) value of about 50% of all flash-rain events is greater than 58 mm. The difference of PW between extreme and ordinary flash-rain is not obvious, but the vertical distribution characteristic of a dry upper level associated with a wet low level of extreme flash-rain is significant. The vertical wind shear can not act as a potential predicator to distinguish flash-rain under different intensities in Sichuan Basin, and the ascending motion can not either.
Based on hourly observational datasets from 84 national automatic weather stations and 6 h ERA-Interim reanalysis data at Sichuan Basin between May and September during 2007-2017, this study investigates the ambient conditions, such as thermodynamic variables, water vapor and vertical wind shear, and contrasts characteristics of convective parameters of the occurrence and development of flash-rain under different intensities. Compared with ordinary short-time severe precipitation, extreme flash-rain has relatively higher lifting condensation level (LCL), higher level of free convection (LFC) and higher equilibrium level (EL), which can be used to effectively distinguish extreme and ordinary flash-rain. About 75% of extreme and ordinary flash-rain events occur in the ambient background with EL higher than 258.6 hPa and 658.2 hPa, respectively. The values of convective available potential energy (CAPE) and convective inhibition (CIN) are larger in extreme flash-rain events. About 50% of extreme and ordinary flash-rain occurrence needs CAPE values greater than 792.5 J·kg-1 and 451.9 J·kg-1, respectively. The bigger difference of potential pseudo-equivalent temperature between 850 hPa and 500 hPa (θse850-θse500) is better for extreme flash-rain, and 10℃ can be the threshold value to judge extreme and ordinary flash-rain. The precipitable water (PW) value of about 50% of all flash-rain events is greater than 58 mm. The difference of PW between extreme and ordinary flash-rain is not obvious, but the vertical distribution characteristic of a dry upper level associated with a wet low level of extreme flash-rain is significant. The vertical wind shear can not act as a potential predicator to distinguish flash-rain under different intensities in Sichuan Basin, and the ascending motion can not either.
2021, 47(4):450-462.
DOI: 10.7519/j.issn.1000-0526.2021.04.006
Abstract:
Based on the data of effective short-time severe rainfall at 219 national stations and from 7 Doppler weather radars in Yunnan Province from May to October in 2014-2016, the short-time severe rainfall in the periphery of the subtropical high in Yunnan is further subdivided into three categories, including the Qinghai-Tibet high and western Pacific subtropical high convergence category, simple periphery of the subtropical high category and the west side of subtropical high with westerly trough category. The conclusions are as follows. August is the high incidence period of short-time severe rainfall in the periphery of the subtropical high in Yunnan Province, and the precipitation period is concentrated in the afternoon and the first half of the night. The Qinghai-Tibet high and western Pacific subtropical high convergence precipitation distributes along the convergence area, with high intensity and relatively concentrated falling area. The simple periphery of the subtropical high precipitation is mainly located in southern Yunnan, manifested as three large-value zones. The west side of subtropical high with westerly trough precipitation is mainly located at the edge of Yunnan with scattered falling areas. The average intensity of the three types of precipitation echoes is between 35 dBz and 45 dBz with average duration of 9 volume scans. Nearly a quarter of the echoes have inclination and strong echo gradients, and the precipitation is obviously heavier than the echo which does not appear. In a way that can be used as a basis for judging the intensity of precipitation. The occurrence time of the strongest ET and VIL of the three types of precipitation is basically at the same time as that of the strongest echo, or slightly lagged behind. Nearly half of the Qinghai-Tibet high and western Pacific subtropical high convergence VWPs have southwesterly or westerly airflows in the lower layer, which corresponds to the obvious characteristics of warm advection. With the development of precipitation, the disappearance of no-data area corresponding to the clear sky area around the subtropical high is the most obvious feature of VWPs of precipitation in the simple periphery of the subtropical high. For the west side of subtropical high with westerly trough category, whether precipitation begins or not, invasion of upper northwest airflow and middle-level wind shear both exist, corresponding to the cold advection brought by the rear of the low trough and the intersection of warm and cold air currents.
Based on the data of effective short-time severe rainfall at 219 national stations and from 7 Doppler weather radars in Yunnan Province from May to October in 2014-2016, the short-time severe rainfall in the periphery of the subtropical high in Yunnan is further subdivided into three categories, including the Qinghai-Tibet high and western Pacific subtropical high convergence category, simple periphery of the subtropical high category and the west side of subtropical high with westerly trough category. The conclusions are as follows. August is the high incidence period of short-time severe rainfall in the periphery of the subtropical high in Yunnan Province, and the precipitation period is concentrated in the afternoon and the first half of the night. The Qinghai-Tibet high and western Pacific subtropical high convergence precipitation distributes along the convergence area, with high intensity and relatively concentrated falling area. The simple periphery of the subtropical high precipitation is mainly located in southern Yunnan, manifested as three large-value zones. The west side of subtropical high with westerly trough precipitation is mainly located at the edge of Yunnan with scattered falling areas. The average intensity of the three types of precipitation echoes is between 35 dBz and 45 dBz with average duration of 9 volume scans. Nearly a quarter of the echoes have inclination and strong echo gradients, and the precipitation is obviously heavier than the echo which does not appear. In a way that can be used as a basis for judging the intensity of precipitation. The occurrence time of the strongest ET and VIL of the three types of precipitation is basically at the same time as that of the strongest echo, or slightly lagged behind. Nearly half of the Qinghai-Tibet high and western Pacific subtropical high convergence VWPs have southwesterly or westerly airflows in the lower layer, which corresponds to the obvious characteristics of warm advection. With the development of precipitation, the disappearance of no-data area corresponding to the clear sky area around the subtropical high is the most obvious feature of VWPs of precipitation in the simple periphery of the subtropical high. For the west side of subtropical high with westerly trough category, whether precipitation begins or not, invasion of upper northwest airflow and middle-level wind shear both exist, corresponding to the cold advection brought by the rear of the low trough and the intersection of warm and cold air currents.
2021, 47(4):463-470.
DOI: 10.7519/j.issn.1000-0526.2021.04.007
Abstract:
In the case study of GRAPES_GFS, the vertical velocity on the upper level over the Antarctic continent has big computational noise, affecting the integral stability, and even causing the integral interruption. The diagnostic analysis of its dynamical core and physics-dynamics couple scheme indicates that the vertical interpolation of the potential temperature at the Lagrangian departure points is the main source of noise. Monthly case study of July 2013 shows that by introducing the vertical non-interpolated Lagrangian scheme into the thermal equation, this computational noise can be greatly reduced or eliminated. The comprehensive performance in the Northern Hemisphere and tropical region has improved significantly, and the serious loss of mass in 8 d integration process has been significantly alleviated.
In the case study of GRAPES_GFS, the vertical velocity on the upper level over the Antarctic continent has big computational noise, affecting the integral stability, and even causing the integral interruption. The diagnostic analysis of its dynamical core and physics-dynamics couple scheme indicates that the vertical interpolation of the potential temperature at the Lagrangian departure points is the main source of noise. Monthly case study of July 2013 shows that by introducing the vertical non-interpolated Lagrangian scheme into the thermal equation, this computational noise can be greatly reduced or eliminated. The comprehensive performance in the Northern Hemisphere and tropical region has improved significantly, and the serious loss of mass in 8 d integration process has been significantly alleviated.
2021, 47(4):471-477.
DOI: 10.7519/j.issn.1000-0526.2021.04.008
Abstract:
In 2020, concentration of the major greenhouse gases on the earth continued to increase. The global mean temperature was 1.2±0.1℃ higher than before industrialization, ranking the second warmest in the same period in history. Sea level continued to rise at a faster rate.The highest ocean heat content was recorded and the Arctic minimum sea ice range became the second smallest on record, of which record low sea ice extents were observed in the months of July and October. The Antarctic sea ice range remained close to the long term average. Over 80% of the ocean area experienced at least one marine heat wave event in 2020. Areas where “strong” ocean heat waves occur were more than the areas with “moderate” ocean heat waves. On the other hand, many countries and regions suffered from severe torrential rain and floods in 2020, including the Sahel Region of Africa, the Greater Horn of Africa, the India Subcontinent and neighbouring areas, China, Korea, Japan, and parts of southeastern Asia, etc. In addition, severe droughts occurred in many parts of interior South America, while Europe, Australia, Mexico and other places were seriously impacted by severe heat wave events. Moreover, severe cold wave and heavy snowfall were experienced in North America, South America and Australia. Also, there were 30 tropical cyclones generated in the North Atlantic, breaking the historic record.
In 2020, concentration of the major greenhouse gases on the earth continued to increase. The global mean temperature was 1.2±0.1℃ higher than before industrialization, ranking the second warmest in the same period in history. Sea level continued to rise at a faster rate.The highest ocean heat content was recorded and the Arctic minimum sea ice range became the second smallest on record, of which record low sea ice extents were observed in the months of July and October. The Antarctic sea ice range remained close to the long term average. Over 80% of the ocean area experienced at least one marine heat wave event in 2020. Areas where “strong” ocean heat waves occur were more than the areas with “moderate” ocean heat waves. On the other hand, many countries and regions suffered from severe torrential rain and floods in 2020, including the Sahel Region of Africa, the Greater Horn of Africa, the India Subcontinent and neighbouring areas, China, Korea, Japan, and parts of southeastern Asia, etc. In addition, severe droughts occurred in many parts of interior South America, while Europe, Australia, Mexico and other places were seriously impacted by severe heat wave events. Moreover, severe cold wave and heavy snowfall were experienced in North America, South America and Australia. Also, there were 30 tropical cyclones generated in the North Atlantic, breaking the historic record.
DAI Tanlong
,
WANG Qiuling
,
WANG Guofu
,
CHEN Yu
,
ZHAO Shanshan
,
ZHAI Jianqing
,
ZOU Xukai
,
JIANG Yundi
,
SHI Shuai
,
ZHOU Bing
,
CUI Tong
,
SUN Shao
,
CAI Wenyue
,
ZHU Xiaojin
,
ZHONG Hailing
,
GUO Yanjun
,
ZHI Rong
,
LIU Yunyun
,
ZHAO Junhu
,
LIU Yanju
,
LI Duo
2021, 47(4):478-487.
DOI: 10.7519/j.issn.1000-0526.2021.04.009
Abstract:
The general feature of China’s climate in 2020 is warm and wet. The 2020 annual mean temperature over China was 0.7℃ higher than normal, becoming the eighth warmest since 1951. The temperatures in all the four seasons were above normal, and much warmer in spring and winter. The annual mean precipitation over amount China was 694.8 mm with 10.3% more than normal. The seasonal precipitation in spring was below normal, but above normal in summer, autumn and winter. The pre-flood season in South China started and ended both earlier than normal with deficient precipitation. The rainy season in Southwest China started later but ended earlier than normal with more heavy precipitation. The Meiyu season started earlier but ended later than normal with more precipitation, resulting in the longest rainy period and the most precipitation amount since 1961. The rainy season in North China, the autumn rain in West China and the rainy season in Northeast China started and ended later than normal with more rainfall. In 2020, the landing typhoons were fewer than normal, feathering concentrated landing locations and periods of time, with lighter disaster losses. Rainstorm and floods occurred heavily, causing serious losses in China. The impacts of other disasters such as droughts, severe convection, cold freezing and snow disaster as well as sand-dust storms, were all mild relatively.
The general feature of China’s climate in 2020 is warm and wet. The 2020 annual mean temperature over China was 0.7℃ higher than normal, becoming the eighth warmest since 1951. The temperatures in all the four seasons were above normal, and much warmer in spring and winter. The annual mean precipitation over amount China was 694.8 mm with 10.3% more than normal. The seasonal precipitation in spring was below normal, but above normal in summer, autumn and winter. The pre-flood season in South China started and ended both earlier than normal with deficient precipitation. The rainy season in Southwest China started later but ended earlier than normal with more heavy precipitation. The Meiyu season started earlier but ended later than normal with more precipitation, resulting in the longest rainy period and the most precipitation amount since 1961. The rainy season in North China, the autumn rain in West China and the rainy season in Northeast China started and ended later than normal with more rainfall. In 2020, the landing typhoons were fewer than normal, feathering concentrated landing locations and periods of time, with lighter disaster losses. Rainstorm and floods occurred heavily, causing serious losses in China. The impacts of other disasters such as droughts, severe convection, cold freezing and snow disaster as well as sand-dust storms, were all mild relatively.
2021, 47(4):488-498.
DOI: 10.7519/j.issn.1000-0526.2021.04.010
Abstract:
It was accurately predicted that in the flood season of 2020, the overall characteristics of “China’s generally poor climate condition, more extreme weather and climate events” and “more serious flooding than drought”. The predictions of abundant precipitation in the middle and lower reaches of the Yangtze River Valley, the middle and upper reaches of the Yellow River Valley, the Haihe River Valley, and the Songhuajiang River Valley, and the deficit precipitation in the Liaohe River Basin, are consistent with observations. The subseasonal monsoon rainy season processes, including the earlier start of South China pre-flood season, the earlier onset and later retreat of Meiyu in Yangtze-Huaihe River Valley, and the later start of North China rainy season than normal, were also well predicted in the climate operation. However, we underestimated the abnormal degree of excessive precipitation in the middle and lower reaches of the Yangtze River, and did not accurately predict the precipitation anomaly in the western reach of the Huaihe River, the Hanshui River, and the Sichuan Basin. The predictions of the surface air temperature are in line with the observations which was warmer than normal in most of China and more high-temperature days in South China. Moreover, we had a good grasp of the tropical cyclone frequency, tracks, and active/inactive periods over the Northwest Pacific and the South China Sea in 2020. For the diagnostic analyses, the weak sea surface temperature (SST) warming in the central and eastern Pacific in pre-winter plus continuous warming in the tropical Indian Ocean were considered to be important predictors. Under the influence of the tropical SST anomalies, the western Pacific subtropical high (WPSH) tended to be stronger and further westward, and anomalous anticyclone dominated the Philippine Sea. Nevertherless, the degree of abnormal warming in the tropical Indian Ocean SST and its impact on the precipitation in the middle and lower reaches of the Yangtze-Huaihe Rivers were underestimated, which is a significant deviation in the prediction. The Climate System Model of the National Climate Centre (NCC_CSM1.1(m)) had a good performance overall in predicting the observation of more precipitation in eastern China, which was mainly related to the accurate prediction of the spatial distribution patterns of atmospheric circulation systems over the tropical and subtropical regions in summer by dynamic models. The subseasonal circulation variations, however, were not well captured, including the double blocking high circulation with “two ridges and one trough” in the mid and high latitudes of Eurasia region in June and July, the persistent southward position of WPSH ridgeline in July, with obviously late subseasonal process.
It was accurately predicted that in the flood season of 2020, the overall characteristics of “China’s generally poor climate condition, more extreme weather and climate events” and “more serious flooding than drought”. The predictions of abundant precipitation in the middle and lower reaches of the Yangtze River Valley, the middle and upper reaches of the Yellow River Valley, the Haihe River Valley, and the Songhuajiang River Valley, and the deficit precipitation in the Liaohe River Basin, are consistent with observations. The subseasonal monsoon rainy season processes, including the earlier start of South China pre-flood season, the earlier onset and later retreat of Meiyu in Yangtze-Huaihe River Valley, and the later start of North China rainy season than normal, were also well predicted in the climate operation. However, we underestimated the abnormal degree of excessive precipitation in the middle and lower reaches of the Yangtze River, and did not accurately predict the precipitation anomaly in the western reach of the Huaihe River, the Hanshui River, and the Sichuan Basin. The predictions of the surface air temperature are in line with the observations which was warmer than normal in most of China and more high-temperature days in South China. Moreover, we had a good grasp of the tropical cyclone frequency, tracks, and active/inactive periods over the Northwest Pacific and the South China Sea in 2020. For the diagnostic analyses, the weak sea surface temperature (SST) warming in the central and eastern Pacific in pre-winter plus continuous warming in the tropical Indian Ocean were considered to be important predictors. Under the influence of the tropical SST anomalies, the western Pacific subtropical high (WPSH) tended to be stronger and further westward, and anomalous anticyclone dominated the Philippine Sea. Nevertherless, the degree of abnormal warming in the tropical Indian Ocean SST and its impact on the precipitation in the middle and lower reaches of the Yangtze-Huaihe Rivers were underestimated, which is a significant deviation in the prediction. The Climate System Model of the National Climate Centre (NCC_CSM1.1(m)) had a good performance overall in predicting the observation of more precipitation in eastern China, which was mainly related to the accurate prediction of the spatial distribution patterns of atmospheric circulation systems over the tropical and subtropical regions in summer by dynamic models. The subseasonal circulation variations, however, were not well captured, including the double blocking high circulation with “two ridges and one trough” in the mid and high latitudes of Eurasia region in June and July, the persistent southward position of WPSH ridgeline in July, with obviously late subseasonal process.
2021, 47(4):499-509.
DOI: 10.7519/j.issn.1000-0526.2021.04.011
Abstract:
In autumn 2020, China’s climate presented the features of “warmer and wetter” than normal. But the intra-seasonal variability was significant. The distribution of precipitation anomaly shows rainfall was more than normal in south and less than normal in northern part of China in September, and the pattern was reversed in November. The circulation of mid-high latitudes of Eurasia in autumn was in the “+-+” EAP pattern, which also showed obvious intra-seasonal variability. The subtropical high over western Pacific (WPSH) continued to be stronger, larger and more westward, but developed southward to its climate state in September and northward in October-November. Further analysis proves that wide warming in the tropical Indian Ocean Basin was beneficial to the strong, large and westerly features of WPSH in autumn. The evolution of SST over tropical mid-east Pacific, where El Ni〖AKn~D〗o event ended in spring and La Ni〖AKn~D〗a started in autumn, had an important impact on tropical and subtropical circulations and favorable to the northward of WPSH, especially in October. Convective activity in the western Pacific warm pool was significantly weaker and more southward than normal, which was conducive to the southward WPSH in September. The co-action of SSTA evolution and intra-seasonal variability of tropical convective activity led to the significant intra-seasonal variability of precipitation in autumn 2020.
In autumn 2020, China’s climate presented the features of “warmer and wetter” than normal. But the intra-seasonal variability was significant. The distribution of precipitation anomaly shows rainfall was more than normal in south and less than normal in northern part of China in September, and the pattern was reversed in November. The circulation of mid-high latitudes of Eurasia in autumn was in the “+-+” EAP pattern, which also showed obvious intra-seasonal variability. The subtropical high over western Pacific (WPSH) continued to be stronger, larger and more westward, but developed southward to its climate state in September and northward in October-November. Further analysis proves that wide warming in the tropical Indian Ocean Basin was beneficial to the strong, large and westerly features of WPSH in autumn. The evolution of SST over tropical mid-east Pacific, where El Ni〖AKn~D〗o event ended in spring and La Ni〖AKn~D〗a started in autumn, had an important impact on tropical and subtropical circulations and favorable to the northward of WPSH, especially in October. Convective activity in the western Pacific warm pool was significantly weaker and more southward than normal, which was conducive to the southward WPSH in September. The co-action of SSTA evolution and intra-seasonal variability of tropical convective activity led to the significant intra-seasonal variability of precipitation in autumn 2020.
2021, 47(4):510-516.
DOI: 10.7519/j.issn.1000-0526.2021.04.012
Abstract:
The main characteristics of the general atmospheric circulation in January 2021 are as follows. Polar vortex was a dipole pattern in the Northern Hemisphere. The atmospheric circulation presented a great meridionality in the mid-high latitudes in Eurasia. The East Asian trough was stronger to the west, and the southern branch trough was weaker in this month. The monthly mean precipitation over China was 5.6 mm, 58% lower than normal (13.2 mm), which is the fourth lowest since 1961. The monthly average temperature was -4.5℃, which is 0.5℃ above the normal. Totally, there was one strong cold air process, two dust weather processes and one largescale fog-haze event in this month. During 4-7 January, a strong cold air process occurred in central and eastern China, characterized by wide range of influence, significant low temperature extremes and long duration of strong winds in northern China.
The main characteristics of the general atmospheric circulation in January 2021 are as follows. Polar vortex was a dipole pattern in the Northern Hemisphere. The atmospheric circulation presented a great meridionality in the mid-high latitudes in Eurasia. The East Asian trough was stronger to the west, and the southern branch trough was weaker in this month. The monthly mean precipitation over China was 5.6 mm, 58% lower than normal (13.2 mm), which is the fourth lowest since 1961. The monthly average temperature was -4.5℃, which is 0.5℃ above the normal. Totally, there was one strong cold air process, two dust weather processes and one largescale fog-haze event in this month. During 4-7 January, a strong cold air process occurred in central and eastern China, characterized by wide range of influence, significant low temperature extremes and long duration of strong winds in northern China.
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ISSN:1000-0526 CN:11-2282/P