ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 50,Issue 2,2024 Table of Contents
2024, 50(2):133-143.
DOI: 10.7519/j.issn.1000-0526.2023.070201
Abstract:
The community of tropical cyclone (TC) researches has identified intensity change of TC as a high priority study subject. The activity of dry cold air, such as the rapid intensification and rapid weak-ening, is closely related to the intensity change of TC. Domestic and international research results of TC intensity change interpreted from the perspective of dry cold air activity are reviewed in the following three aspects: the intensity of dry cold air and intrusion location as well as the effect of upper tropospheric cold weather system on TC intensity change. Also, an outlook for future research is also given here to promote the study of the effect of dry cold air on the intensity change of TC.
The community of tropical cyclone (TC) researches has identified intensity change of TC as a high priority study subject. The activity of dry cold air, such as the rapid intensification and rapid weak-ening, is closely related to the intensity change of TC. Domestic and international research results of TC intensity change interpreted from the perspective of dry cold air activity are reviewed in the following three aspects: the intensity of dry cold air and intrusion location as well as the effect of upper tropospheric cold weather system on TC intensity change. Also, an outlook for future research is also given here to promote the study of the effect of dry cold air on the intensity change of TC.
YAO Lebao
,
SHEN Dan
,
MENG Xuefeng
,
SUN Xin
,
MENG Zhiyong
,
HUANG Xiaolu
,
YE Fei
,
LIU Linchun
,
SUN Yonggang
2024, 50(2):144-158.
DOI: 10.7519/j.issn.1000-0526.2023.091801
Abstract:
Based on the low resolution version of RMAPS-NM forecast system and WRFDA-FSO diagnostic tool, this paper evaluates the impact of existing radiosonde and surface observation on RMAPS-NM forecast system in July 2021. This method is relatively cheap in computation, and allows the observation impact to be divided to the subset of observation according to observation variables, observation types, barometric levels, geographical regions, etc. The cost function is the difference between the prediction error of the background field and the analysis field measured by the total dry energy. The results show that the total sum of observation impact is negative, and observation plays a positive role in prediction. The observation that contributes most to the reduction of 12 h prediction error comes from the dynamic variables (U, V wind components) of radiosonde observation. However, the contribution of radiosonde observation to the average observation impact per unit quantity of a single time is about 1/2 of that of surface observation. The radiosonde observation has a positive contribution to the reduction of 12 h prediction error from the near surface layer to the top of model layer, and there are two maximum zones in the middle and lower troposphere and in the troposphere upper jet layer. The positive contribution of surface observation is obvious in the lower layer below 850 hPa. The radiosonde observation, when assimilated by the assimilation system, has a favorable influence overall, which also reflects the characteristics of stable and high-quality characteristics to radiosonde observation. The zone with the most times of positive contribution for surface observation to the reduction of 12 h prediction error is particularly significant in the Hetao Region. At the same time, the problem that the assimilation rate of surface observation data should be further improved is discussed.
Based on the low resolution version of RMAPS-NM forecast system and WRFDA-FSO diagnostic tool, this paper evaluates the impact of existing radiosonde and surface observation on RMAPS-NM forecast system in July 2021. This method is relatively cheap in computation, and allows the observation impact to be divided to the subset of observation according to observation variables, observation types, barometric levels, geographical regions, etc. The cost function is the difference between the prediction error of the background field and the analysis field measured by the total dry energy. The results show that the total sum of observation impact is negative, and observation plays a positive role in prediction. The observation that contributes most to the reduction of 12 h prediction error comes from the dynamic variables (U, V wind components) of radiosonde observation. However, the contribution of radiosonde observation to the average observation impact per unit quantity of a single time is about 1/2 of that of surface observation. The radiosonde observation has a positive contribution to the reduction of 12 h prediction error from the near surface layer to the top of model layer, and there are two maximum zones in the middle and lower troposphere and in the troposphere upper jet layer. The positive contribution of surface observation is obvious in the lower layer below 850 hPa. The radiosonde observation, when assimilated by the assimilation system, has a favorable influence overall, which also reflects the characteristics of stable and high-quality characteristics to radiosonde observation. The zone with the most times of positive contribution for surface observation to the reduction of 12 h prediction error is particularly significant in the Hetao Region. At the same time, the problem that the assimilation rate of surface observation data should be further improved is discussed.
2024, 50(2):159-169.
DOI: 10.7519/j.issn.1000-0526.2023.110501
Abstract:
The round-trip horizontal drift radiosonde can do the three-stage observation of “ascending-drifting-descending stages” by releasing one sounding balloon at only one time. In particular, in the descending stage the radiosonde can increase the vertical observation of the atmosphere at 06 UTC and 18 UTC respectively, and it has the potential to significantly improve the prediction skills of the regional high-resolution rapid assimilation cycle prediction system at 06 UTC and 18 UTC. In order to achieve the assimilation of the round-trip horizontal drift sounding in the high-resolution regional model and analyze its impacts on the forecast, one vertical thinning method by “selecting the closest observation according to the model layer” for assimilation is preliminarily proposed, and the influence of this thinning method on model analysis is deeply analyzed. On this basis, a one-month batch assimilation impact experiment was carried out by using the networked observations in the middle and lower reaches of Yangtze River, and the impacts on model forecasts are investigated in detail in this paper. The results of the thinning sensitivity tests show that, compared with the assimilation of traditional operational soundings, the analysis and prediction root mean square errors (RMSE) of the assimilation of non-thinning round-trip horizontal drift radiosonde observations are significantly increased, while the precipitation prediction scores are significantly reduced. On the contrary, the model performances in analysis and prediction fields are improved by assimilating the data after vertical thinning， which indicates that the vertical thinning of round-trip horizontal drift radiosonde observations must be carried out before assimilation. The results of batch experiments show that at the cold start time (00 UTC and 12 UTC, time with conventional radiosonde), the assimilation of round-trip horizontal drift sounding (ascending stage) observations has smaller changes in analysis error and prediction error relative to assimilation of traditional operational radiosonde data. At the warm start time (03 UTC, 06 UTC, 09 UTC, 15 UTC, 18 UTC, 21 UTC, time without conventional radiosonde), however, compared with the control experiment, the accuracy of the analysis field is improved by about 0.4% by assimilating the data of descending section of the horizontal drift sounding. The ETS scores of the 0-12 h accumulated precipitation forecast change less, but the ETS scores of the 12-24 h accumulated precipitation forecast at 0.1, 1.0, 5.0, 10.0， 25.0 mm thresholds increase by about 0.5%. Moreover, the ETS score at 50.0 mm threshold increases by about 2.3%. All above results show that the round-trip horizontal drift sounding must be thinned before assimilation, and the assimilation of the round-trip horizontal drift sounding can improve the precipitation forecast skill of the regional high-resolution rapid assimilation cycle forecast system at the warm start time.
The round-trip horizontal drift radiosonde can do the three-stage observation of “ascending-drifting-descending stages” by releasing one sounding balloon at only one time. In particular, in the descending stage the radiosonde can increase the vertical observation of the atmosphere at 06 UTC and 18 UTC respectively, and it has the potential to significantly improve the prediction skills of the regional high-resolution rapid assimilation cycle prediction system at 06 UTC and 18 UTC. In order to achieve the assimilation of the round-trip horizontal drift sounding in the high-resolution regional model and analyze its impacts on the forecast, one vertical thinning method by “selecting the closest observation according to the model layer” for assimilation is preliminarily proposed, and the influence of this thinning method on model analysis is deeply analyzed. On this basis, a one-month batch assimilation impact experiment was carried out by using the networked observations in the middle and lower reaches of Yangtze River, and the impacts on model forecasts are investigated in detail in this paper. The results of the thinning sensitivity tests show that, compared with the assimilation of traditional operational soundings, the analysis and prediction root mean square errors (RMSE) of the assimilation of non-thinning round-trip horizontal drift radiosonde observations are significantly increased, while the precipitation prediction scores are significantly reduced. On the contrary, the model performances in analysis and prediction fields are improved by assimilating the data after vertical thinning， which indicates that the vertical thinning of round-trip horizontal drift radiosonde observations must be carried out before assimilation. The results of batch experiments show that at the cold start time (00 UTC and 12 UTC, time with conventional radiosonde), the assimilation of round-trip horizontal drift sounding (ascending stage) observations has smaller changes in analysis error and prediction error relative to assimilation of traditional operational radiosonde data. At the warm start time (03 UTC, 06 UTC, 09 UTC, 15 UTC, 18 UTC, 21 UTC, time without conventional radiosonde), however, compared with the control experiment, the accuracy of the analysis field is improved by about 0.4% by assimilating the data of descending section of the horizontal drift sounding. The ETS scores of the 0-12 h accumulated precipitation forecast change less, but the ETS scores of the 12-24 h accumulated precipitation forecast at 0.1, 1.0, 5.0, 10.0， 25.0 mm thresholds increase by about 0.5%. Moreover, the ETS score at 50.0 mm threshold increases by about 2.3%. All above results show that the round-trip horizontal drift sounding must be thinned before assimilation, and the assimilation of the round-trip horizontal drift sounding can improve the precipitation forecast skill of the regional high-resolution rapid assimilation cycle forecast system at the warm start time.
2024, 50(2):170-180.
DOI: 10.7519/j.issn.1000-0526.2023.051901
Abstract:
Based on multi-source observation data and ERA5 （0.25°×0.25°） reanalysis data, the causes of the first rainstorm in the local warm sector of Zhejiang in the Meiyu period over the night of 9 June 2021 are analyzed. The results are as follows. The circulation situation of this process was different from that of the typical Meiyu, and belonged to the rainstorm in the local warm sector under a weak weather background. The maintenance of the southeast air flow between the South China Sea low pressure and the western Pacific subtropical high provided abundant water vapor for the rainstorm area. The strengthening of 925 hPa ultra-low level southerly jet was conducive to the increase in temperature and humidity in the low layer and the aggravation of unstable stratification, and the rainstorm area was located on the left side of the jet axis. The weak lifting condition caused by the high humidity background triggered convection. The strengthening of cyclonic convergence and rotation in the middle and high layers strengthened the rainstorm, and the thicker warm cloud layer was benefitial to improving the precipitation efficiency. The formation of mesoscale convergence zone stimulated the initial convection, and its maintenance and strengthening stimulated the formation of convective cloud clusters, producing train effect and leading to the formation of rainstorm. The small-scale topography of Longmen Mountain was favorable for the forced uplift of southerly air flow on the windward slope, strengthening the convection. The development of vertical velocity had a good corresponding relationship with the height of the topography. The higher the topography height, the stronger the verticle velocity to be stimulated.
Based on multi-source observation data and ERA5 （0.25°×0.25°） reanalysis data, the causes of the first rainstorm in the local warm sector of Zhejiang in the Meiyu period over the night of 9 June 2021 are analyzed. The results are as follows. The circulation situation of this process was different from that of the typical Meiyu, and belonged to the rainstorm in the local warm sector under a weak weather background. The maintenance of the southeast air flow between the South China Sea low pressure and the western Pacific subtropical high provided abundant water vapor for the rainstorm area. The strengthening of 925 hPa ultra-low level southerly jet was conducive to the increase in temperature and humidity in the low layer and the aggravation of unstable stratification, and the rainstorm area was located on the left side of the jet axis. The weak lifting condition caused by the high humidity background triggered convection. The strengthening of cyclonic convergence and rotation in the middle and high layers strengthened the rainstorm, and the thicker warm cloud layer was benefitial to improving the precipitation efficiency. The formation of mesoscale convergence zone stimulated the initial convection, and its maintenance and strengthening stimulated the formation of convective cloud clusters, producing train effect and leading to the formation of rainstorm. The small-scale topography of Longmen Mountain was favorable for the forced uplift of southerly air flow on the windward slope, strengthening the convection. The development of vertical velocity had a good corresponding relationship with the height of the topography. The higher the topography height, the stronger the verticle velocity to be stimulated.
2024, 50(2):181-194.
DOI: 10.7519/j.issn.1000-0526.2023.092801
Abstract:
Based on the conventional surface and upper-air observations, Doppler radar products, wind-profiling radar data, VDRAS and NCEP reanalysis data, the triggering and development mechanisms of multiple β-meso scale convective systems under the influence of subtropical high in North China from 5 to 6 August 2018 are analyzed. The results show that this severe torrential rain occurred under the control of subtropical high, in a high temperature and high humidity air mass, with extremely unstable atmospheric stratification. The torrential rain was caused by multiple successive developing mesoscale convective systems, namely MCS-Ⅰ, MCS-Ⅱ, MCS-Ⅲ and MCS-Ⅳ, which were quasi-stationary β-meso scale systems on the windward slope of Taihang Mountains in southwest-northeast direction, in Baoding Area of North China Plain in north-south direction, near Baoding to Bazhou in the southwest-northeast direction and centered on Xiong’an New Area in east-west direction， respectively. In a similar environment, different mesoscale convective systems had significant differences in triggering mechanisms. MCS-Ⅰ on the windward slope of Taihang Mountains was triggered by near-surface easterly warm and humid airflow converging and lifting on the windward slope with mountain wind. After being influenced by MCS-Ⅰ, the local cold pool formed by radiation difference and earlier-stage severe precipitation was strengthened again. Its outflow formed two surface convergence lines with environmental wind, which triggered MCS-Ⅱ and MCS-Ⅲ and organized convection along convergence line into band-like development. The enhanced easterly wind at ultra-low altitude superimposed the outflow of the cold pool, promoting further uplift of the warm and humid air mass along the mountain under the effect of terrain uplift, triggering MCS-Ⅰ reconstruction. MCS-Ⅳ developed most vigorously and lasted longest, and was the direct maker of the severe torrential rain center. On one hand, the two merger processes of MCS-Ⅱ and MCS-Ⅲ, MCS-Ⅰ and MCS-Ⅳ were important reasons for the strengthening and persistence of MCS-Ⅳ. On the other hand, the boundary layer easterly jet provided favorable conditions such as water vapor 〖JP2〗and unstable energy for MCS-Ⅳ’s development, and also〖JP〗 promoted the development of mesoscale vortex in its left front side, resulting in a significant increase of cyclonic vorticity in MCS-Ⅳ’s location, enhancing the vertical secondary circulation development centered on jet axis, causing MCS-Ⅳ’s continuous maintenance, and forming an east-west severe torrential rain belt centered at Xiong’an New Area in North China Plain.
Based on the conventional surface and upper-air observations, Doppler radar products, wind-profiling radar data, VDRAS and NCEP reanalysis data, the triggering and development mechanisms of multiple β-meso scale convective systems under the influence of subtropical high in North China from 5 to 6 August 2018 are analyzed. The results show that this severe torrential rain occurred under the control of subtropical high, in a high temperature and high humidity air mass, with extremely unstable atmospheric stratification. The torrential rain was caused by multiple successive developing mesoscale convective systems, namely MCS-Ⅰ, MCS-Ⅱ, MCS-Ⅲ and MCS-Ⅳ, which were quasi-stationary β-meso scale systems on the windward slope of Taihang Mountains in southwest-northeast direction, in Baoding Area of North China Plain in north-south direction, near Baoding to Bazhou in the southwest-northeast direction and centered on Xiong’an New Area in east-west direction， respectively. In a similar environment, different mesoscale convective systems had significant differences in triggering mechanisms. MCS-Ⅰ on the windward slope of Taihang Mountains was triggered by near-surface easterly warm and humid airflow converging and lifting on the windward slope with mountain wind. After being influenced by MCS-Ⅰ, the local cold pool formed by radiation difference and earlier-stage severe precipitation was strengthened again. Its outflow formed two surface convergence lines with environmental wind, which triggered MCS-Ⅱ and MCS-Ⅲ and organized convection along convergence line into band-like development. The enhanced easterly wind at ultra-low altitude superimposed the outflow of the cold pool, promoting further uplift of the warm and humid air mass along the mountain under the effect of terrain uplift, triggering MCS-Ⅰ reconstruction. MCS-Ⅳ developed most vigorously and lasted longest, and was the direct maker of the severe torrential rain center. On one hand, the two merger processes of MCS-Ⅱ and MCS-Ⅲ, MCS-Ⅰ and MCS-Ⅳ were important reasons for the strengthening and persistence of MCS-Ⅳ. On the other hand, the boundary layer easterly jet provided favorable conditions such as water vapor 〖JP2〗and unstable energy for MCS-Ⅳ’s development, and also〖JP〗 promoted the development of mesoscale vortex in its left front side, resulting in a significant increase of cyclonic vorticity in MCS-Ⅳ’s location, enhancing the vertical secondary circulation development centered on jet axis, causing MCS-Ⅳ’s continuous maintenance, and forming an east-west severe torrential rain belt centered at Xiong’an New Area in North China Plain.
2024, 50(2):195-209.
DOI: 10.7519/j.issn.1000-0526.2023.100801
Abstract:
Using the Jinan S-band dual-polarization Doppler weather radar data, Zhangqiu sounding and ground conventional meteorological observation data and disaster investigation, this article analyzes the dual-polarization and microphysical structure characteristics of a hail supercell storm that occurred in Zhangqiu, Jinan on 9 July 2021. The results show that under the background of cold vortex weather, strong vertical wind shear and strong convective available potential energy were conducive to the formation and maintenance of supercell. The gust front was the trigger mechanism of the storm and the long-term maintenance mechanism of the storm. The initial storm was triggered by the gust front and it developed into a supercell through merging. In the mature stage, the intersection area between the west side of the storm and the gust front continuously excited new cells, which merged with the main body, thus the storm maintained for a long time. The strong divergence of storm top was one of the key factors for the long-term maintenance of mesocyclone and the high height of storm top. In the super-large hail stage, there existed a clear inflow gap at the right rear of the storm bottom, and there was a differential reflectivity arc in front of it, manifested as a small amount of large liquid particles or small wet ice particles. The strong reflectivity factor area on the left side of the inflow gap corresponded to small differential reflectivity and small correlation coefficient, which was the hail falling area. In terms of the vertical structure, there was a deep bounded weak echo zone on the side of the strong updraft area, and a differential reflectivity ring was distributed below the height of the 0°C layer. There was a differential reflectivity column in the bounded weak echo zone and above it, and the height was higher with a little larger liquid or melting small ice particles. The higher differential reflectivity column indicates that the updraft in the storm is strong and high, which is benefitical to the development and maintenance of the storm and the wet growth of hail particles.
Using the Jinan S-band dual-polarization Doppler weather radar data, Zhangqiu sounding and ground conventional meteorological observation data and disaster investigation, this article analyzes the dual-polarization and microphysical structure characteristics of a hail supercell storm that occurred in Zhangqiu, Jinan on 9 July 2021. The results show that under the background of cold vortex weather, strong vertical wind shear and strong convective available potential energy were conducive to the formation and maintenance of supercell. The gust front was the trigger mechanism of the storm and the long-term maintenance mechanism of the storm. The initial storm was triggered by the gust front and it developed into a supercell through merging. In the mature stage, the intersection area between the west side of the storm and the gust front continuously excited new cells, which merged with the main body, thus the storm maintained for a long time. The strong divergence of storm top was one of the key factors for the long-term maintenance of mesocyclone and the high height of storm top. In the super-large hail stage, there existed a clear inflow gap at the right rear of the storm bottom, and there was a differential reflectivity arc in front of it, manifested as a small amount of large liquid particles or small wet ice particles. The strong reflectivity factor area on the left side of the inflow gap corresponded to small differential reflectivity and small correlation coefficient, which was the hail falling area. In terms of the vertical structure, there was a deep bounded weak echo zone on the side of the strong updraft area, and a differential reflectivity ring was distributed below the height of the 0°C layer. There was a differential reflectivity column in the bounded weak echo zone and above it, and the height was higher with a little larger liquid or melting small ice particles. The higher differential reflectivity column indicates that the updraft in the storm is strong and high, which is benefitical to the development and maintenance of the storm and the wet growth of hail particles.
2024, 50(2):210-220.
DOI: 10.7519/j.issn.1000-0526.2023.122801
Abstract:
This article uses the T-Matrix method and raindrop spectrometer data to invert the dual-polarization parameters, and the inversion result is used to evaluate the dual-polarization weather radar data, which is the raindrop spectrum inversion evaluation method. Then this method is used to evaluate the data quality of polarization parameter in different types of precipitation. The results show that under the conditions of micro-raindrop, the raindrop spectrum inversion evaluation method can effectively monitor the systematic deviation of the polarization parameters caused by the radar systematic error as the same as micro-raindrop method, and the evaluation results of the two methods are basically consistent.When the micro-raindrop condition is not satisfied, the radar polarization parameter quality of different types of precipitation processes evaluated by the raindrop spectrum inversion evaluation method is basically consistent with the evaluation results under the conditions of micro-raindrop, reflecting the objective fact that the radar operates well and the data quality is stable. The raindrop spectrum inversion evaluation method has consistency in evaluating radar polarization parameters under different rainfall intensities. When the rainfall intensity of precipitation process is ≥10 mm·h-1 and ＜20 mm·h-1, the data quality of the dual-polarization radar is the most stable.The raindrop spectrum inversion evaluation method has a wide range of applications and can be used for real-time monitoring of dual-polarization radar data quality. The evaluation results can provide timely reference for radar calibration and data correction.
This article uses the T-Matrix method and raindrop spectrometer data to invert the dual-polarization parameters, and the inversion result is used to evaluate the dual-polarization weather radar data, which is the raindrop spectrum inversion evaluation method. Then this method is used to evaluate the data quality of polarization parameter in different types of precipitation. The results show that under the conditions of micro-raindrop, the raindrop spectrum inversion evaluation method can effectively monitor the systematic deviation of the polarization parameters caused by the radar systematic error as the same as micro-raindrop method, and the evaluation results of the two methods are basically consistent.When the micro-raindrop condition is not satisfied, the radar polarization parameter quality of different types of precipitation processes evaluated by the raindrop spectrum inversion evaluation method is basically consistent with the evaluation results under the conditions of micro-raindrop, reflecting the objective fact that the radar operates well and the data quality is stable. The raindrop spectrum inversion evaluation method has consistency in evaluating radar polarization parameters under different rainfall intensities. When the rainfall intensity of precipitation process is ≥10 mm·h-1 and ＜20 mm·h-1, the data quality of the dual-polarization radar is the most stable.The raindrop spectrum inversion evaluation method has a wide range of applications and can be used for real-time monitoring of dual-polarization radar data quality. The evaluation results can provide timely reference for radar calibration and data correction.
2024, 50(2):221-233.
DOI: 10.7519/j.issn.1000-0526.2023.010901
Abstract:
Coastal offshore observation stations are rare, but coastal land observation stations are relatively dense. Carrying out research on the characteristics of land-sea wind speed difference caused by land-sea distribution and realizing the estimation of sea surface wind speed from land observation wind speed is helpful to improve the service ability of sea surface wind forecast. In this paper, the hourly mean wind speed and gust speed data of two groups of buoys and their adjacent land observation stations in the north coast of China from 2016 to 2020 are used to statistically analyze the characteristics and regularity of the difference between sea surface wind speed and land wind speed. And the support vector machine method is used to build the sea surface wind speed estimation model based on the land mean wind speed, land gust speed, distance between land-sea stations, month and hour. The estimation model is tested by using the observation data of the other two groups of land-sea observation stations in 2021. The results show that for the mean wind speed ≥ scale 6 and gust wind speed ≥ scale 7, the model has a high estimation accuracy. The root mean square errors of the mean wind speed (gust speed) of the two groups estimated by the model are 2.40 m·s-1 (3.20 m·s-1) and 2.35 m·s-1 (2.57 m·s-1), respectively. Compared with ERA5, the errors decreased by 24% (14%) and 23% (20%) respectively. In a strong wind process jointly affected by an extratropical cyclone and cold air, the mean absolute errors of the mean wind speed (gust speed) estimated by the model for the two test groups are 1.6 m·s-1 (2.3 m·s-1) and 1.1 m·s-1 (1.5 m·s-1) respectively, and the mean wind speed (gust speed) errors at the extreme moment are -1.3 m·s-1 (-0.6 m·s-1) and -1.2 m·s-1 (-3.1 m·s-1) respectively, which are better than those from ERA5. The sea surface wind speed estimation model based on support vector machine can estimate accurate heavy sea surface wind speed using the land observation wind speed, which can reduce the impact of insufficient sea observation data, and has a certain application prospect.
Coastal offshore observation stations are rare, but coastal land observation stations are relatively dense. Carrying out research on the characteristics of land-sea wind speed difference caused by land-sea distribution and realizing the estimation of sea surface wind speed from land observation wind speed is helpful to improve the service ability of sea surface wind forecast. In this paper, the hourly mean wind speed and gust speed data of two groups of buoys and their adjacent land observation stations in the north coast of China from 2016 to 2020 are used to statistically analyze the characteristics and regularity of the difference between sea surface wind speed and land wind speed. And the support vector machine method is used to build the sea surface wind speed estimation model based on the land mean wind speed, land gust speed, distance between land-sea stations, month and hour. The estimation model is tested by using the observation data of the other two groups of land-sea observation stations in 2021. The results show that for the mean wind speed ≥ scale 6 and gust wind speed ≥ scale 7, the model has a high estimation accuracy. The root mean square errors of the mean wind speed (gust speed) of the two groups estimated by the model are 2.40 m·s-1 (3.20 m·s-1) and 2.35 m·s-1 (2.57 m·s-1), respectively. Compared with ERA5, the errors decreased by 24% (14%) and 23% (20%) respectively. In a strong wind process jointly affected by an extratropical cyclone and cold air, the mean absolute errors of the mean wind speed (gust speed) estimated by the model for the two test groups are 1.6 m·s-1 (2.3 m·s-1) and 1.1 m·s-1 (1.5 m·s-1) respectively, and the mean wind speed (gust speed) errors at the extreme moment are -1.3 m·s-1 (-0.6 m·s-1) and -1.2 m·s-1 (-3.1 m·s-1) respectively, which are better than those from ERA5. The sea surface wind speed estimation model based on support vector machine can estimate accurate heavy sea surface wind speed using the land observation wind speed, which can reduce the impact of insufficient sea observation data, and has a certain application prospect.
2024, 50(2):234-245.
DOI: 10.7519/j.issn.1000-0526.2023.050803
Abstract:
To deal with the lack of marine observation data and enhance the monitoring ability of strong wind event in the Yellow Sea and Bohai Sea, a calculation method of wind speed in sea area under different atmospheric circulation patterns is developed, on the basis of multiple linear regression method and observation data from 74 coastal and island stations as well as 21 sea-based stations of buoy and ship stations from 2017 to 2020. The calculated results are tested by the observation data in 2021. The results show that the wind speed prediction models (CM model and HM model, respectively) established for all wind scales and winds stronger than scale 6 have higher reliability, and especially the HM model has higher accuracy for wind prediction. The probability of strong winds exceeds 60% for five out of the eight weather types. Among the five weather types with high frequency of gale, the calculation effect for the northwest high-southeast low type is the best, the calculation effects for winds at scales 6-7 of the west high-east low type, the southwest high-northeast low type and the northwest low-southeast high type are better, but the calculation effects for the three types of strong winds at scale 8 and above are slightly worse. In the calculation results of gale in different sea areas, the wind speed calculated for most sea areas of the Yellow Sea and the Bohai Sea is smaller than observation data, and the wind speed calculated for some stations in the southwest sea area of the Bohai Sea is larger than observation data. The minimum mean absolute error in the northern Yellow Sea is 0.95 m·s-1, and the mean absolute error in other sea areas is 1.32-1.70 m·s-1. The calculated wind speed can effectively supplement the marine wind observation in the case of discontinuous and unstable observation in the sea area. The calculating method is easy to be applied in operational work, and can be further optimized with increasing number of observation data in different sea areas. It also has a certain reference value in designating the layout of marine observation systems.
To deal with the lack of marine observation data and enhance the monitoring ability of strong wind event in the Yellow Sea and Bohai Sea, a calculation method of wind speed in sea area under different atmospheric circulation patterns is developed, on the basis of multiple linear regression method and observation data from 74 coastal and island stations as well as 21 sea-based stations of buoy and ship stations from 2017 to 2020. The calculated results are tested by the observation data in 2021. The results show that the wind speed prediction models (CM model and HM model, respectively) established for all wind scales and winds stronger than scale 6 have higher reliability, and especially the HM model has higher accuracy for wind prediction. The probability of strong winds exceeds 60% for five out of the eight weather types. Among the five weather types with high frequency of gale, the calculation effect for the northwest high-southeast low type is the best, the calculation effects for winds at scales 6-7 of the west high-east low type, the southwest high-northeast low type and the northwest low-southeast high type are better, but the calculation effects for the three types of strong winds at scale 8 and above are slightly worse. In the calculation results of gale in different sea areas, the wind speed calculated for most sea areas of the Yellow Sea and the Bohai Sea is smaller than observation data, and the wind speed calculated for some stations in the southwest sea area of the Bohai Sea is larger than observation data. The minimum mean absolute error in the northern Yellow Sea is 0.95 m·s-1, and the mean absolute error in other sea areas is 1.32-1.70 m·s-1. The calculated wind speed can effectively supplement the marine wind observation in the case of discontinuous and unstable observation in the sea area. The calculating method is easy to be applied in operational work, and can be further optimized with increasing number of observation data in different sea areas. It also has a certain reference value in designating the layout of marine observation systems.
ZHU Xiaying
,
SUN Linhai
,
ZHONG Hailing
,
ZHI Rong
,
AI Wanxiu
,
JIANG Yundi
,
LI Wei
,
CHEN Xianyan
,
ZOU Xukai
,
WANG Ling
,
ZHAO Shanshan
,
ZENG Hongling
,
WANG Youmin
,
FENG Aiqing
,
ZHU Xiaojin
,
DAI Tanlong
,
GUO Yanjun
,
ZHANG Yingxian
,
LI Xiang
,
GONG Zhensong
2024, 50(2):246-256.
DOI: 10.7519/j.issn.1000-0526.2024.010501
Abstract:
China experienced a warm and dry climate in 2023 with the national average temperature reaching 10.71℃, which is 0.82℃ warmer than the climatology of 1991-2020 and has peaked the warmest temperature since 1951. The annual precipitation averaged over China was 615.0 mm, being 3.9% less than the normal and the second lowest since 2012. The temperatures in all four seasons in the year were higher than normal values, and the summer and autumn temperatures were found to be the second warmest and the warmest in the same periods in records, respectively. In terms of precipitation in 2023, precipitation in autumn was more than normal, but less than normal in the other three seasons. During the rainy season from May to September, the national average precipitation was reduced by 4.3% compared to the normal amount, recorded as the second lowest since 2012. The precipitation in the central and eastern parts of China was characterized by the distribution of more in the middle and less in the north and south. In 2023, China suffered from many types of regional meteorological disasters. First of all, droughts occurred in many regions, and particularly the Southwest China experienced consecutive drought from winter to spring. Also in spring, more than normal sand-dust processes attacked northern China. Then, in early summer, North China and the Huanghuai Region endured the most intense high-temperature process since 1961. From the end of July to the beginning of August, a rarely-seen extremely severe precipitation process, which was caused by the Super Typhoon Doksuri, hit the Beijing-Tianjin-Hebei Region, incurring heavy flood disaster, thus a phenomenon “rapid transfer from drought to flood” occurred in North China. The autumn rain in West China started earlier but ended late, resulting much more rainfall than normal. In addition, there were more than normal cold waves impacting China all the year round, and the most intense cold wave took place in mid-January. Moreover, cold airs frequently appeared in late autumn and early winter, making more heavy snowfall days and deeper snow depth in December in North China and Huanghuai Region.
China experienced a warm and dry climate in 2023 with the national average temperature reaching 10.71℃, which is 0.82℃ warmer than the climatology of 1991-2020 and has peaked the warmest temperature since 1951. The annual precipitation averaged over China was 615.0 mm, being 3.9% less than the normal and the second lowest since 2012. The temperatures in all four seasons in the year were higher than normal values, and the summer and autumn temperatures were found to be the second warmest and the warmest in the same periods in records, respectively. In terms of precipitation in 2023, precipitation in autumn was more than normal, but less than normal in the other three seasons. During the rainy season from May to September, the national average precipitation was reduced by 4.3% compared to the normal amount, recorded as the second lowest since 2012. The precipitation in the central and eastern parts of China was characterized by the distribution of more in the middle and less in the north and south. In 2023, China suffered from many types of regional meteorological disasters. First of all, droughts occurred in many regions, and particularly the Southwest China experienced consecutive drought from winter to spring. Also in spring, more than normal sand-dust processes attacked northern China. Then, in early summer, North China and the Huanghuai Region endured the most intense high-temperature process since 1961. From the end of July to the beginning of August, a rarely-seen extremely severe precipitation process, which was caused by the Super Typhoon Doksuri, hit the Beijing-Tianjin-Hebei Region, incurring heavy flood disaster, thus a phenomenon “rapid transfer from drought to flood” occurred in North China. The autumn rain in West China started earlier but ended late, resulting much more rainfall than normal. In addition, there were more than normal cold waves impacting China all the year round, and the most intense cold wave took place in mid-January. Moreover, cold airs frequently appeared in late autumn and early winter, making more heavy snowfall days and deeper snow depth in December in North China and Huanghuai Region.
2024, 50(2):257-264.
DOI: 10.7519/j.issn.1000-0526.2024.011601
Abstract:
The main characteristics of the general circulation of atmosphere in November 2023 are as follows. There were three polar vortex centers in the Northern Hemisphere, and the intensity of polar vortexes was significantly stronger than normal. The mid-high latitude circulation was distributed in the pattern of four troughs and four ridges. The mid-high latitude circulation in Asia was in the west-high and east-low pattern overall, but the East Asian trough was weaker than that in the same period of normal year, and the western Pacific subtropical high was stronger. In November, the national monthly mean temperature was 0.5℃ higher than usual (3.3℃) and the national monthly mean precipitation increased by 9% relative to normal (20.2 mm). The regions having received much more precipitation included Inner Mongolia, Northeast China, southern part of North China and northern part of Huanghuai Area, Especially, some parts of Northeast China saw the precipitation surpass the recorded maximum value for the same time period. During this month, cold airs were more active and frequent, making the atmospheric dispersion conditions improved overall with less fog-haze weather seen in the central and eastern parts of China. In addition, two cold wave processes occurred in the northern part of China.
The main characteristics of the general circulation of atmosphere in November 2023 are as follows. There were three polar vortex centers in the Northern Hemisphere, and the intensity of polar vortexes was significantly stronger than normal. The mid-high latitude circulation was distributed in the pattern of four troughs and four ridges. The mid-high latitude circulation in Asia was in the west-high and east-low pattern overall, but the East Asian trough was weaker than that in the same period of normal year, and the western Pacific subtropical high was stronger. In November, the national monthly mean temperature was 0.5℃ higher than usual (3.3℃) and the national monthly mean precipitation increased by 9% relative to normal (20.2 mm). The regions having received much more precipitation included Inner Mongolia, Northeast China, southern part of North China and northern part of Huanghuai Area, Especially, some parts of Northeast China saw the precipitation surpass the recorded maximum value for the same time period. During this month, cold airs were more active and frequent, making the atmospheric dispersion conditions improved overall with less fog-haze weather seen in the central and eastern parts of China. In addition, two cold wave processes occurred in the northern part of China.
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ISSN:1000-0526 CN:11-2282/P