ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 50,Issue 4,2024 Table of Contents
2024, 50(4):393-406.
DOI: 10.7519/j.issn.1000-0526.2023.123001
Abstract:
Based on the hourly precipitation data from national meteorological stations of China and the definition method of extreme precipitation with percentile threshold, this paper makes a statistical study of the spatio-temperal distribution and diurnal variation of hourly precipitation in China from April to October in 1951-2021. The results show that the hourly precipitation thresholds of the main rainy season in China are large in the southeast but small in the northwest, and there are four large threshold value centers lo-cated in South China, the Circum-Bohai Region, the middle and lower reaches of the Yangtze River and the Sichuan Basin. With the increasing extremeness, the hourly precipitation threshold in northern China increases more significantly than that in southern China, and the large threshold center moves northward. On the monthly time scale, from the south to north of China, the month with the highest frequency of hourly precipitation is postponed from May to August and the latest month is in West China (September-October). As the extremeness increases, the month with the highest frequency of precipitation is postponed from June-July to July-August, and the regional differences are reduced. In terms of diurnal variation characteristics, the frequency proportion of hourly precipitation of China presents a main valley-peak cycle from afternoon to night and a sub-cycle from midnight to morning. With the increasing extremeness, the amplitude of the main cycle increases and the peak value of the sub-cycle decreases. From the perspective of different geographical locations, the peak time of extreme hourly precipitation in Sichuan Basin is in the early morning, while the peak time in other three areas is consistent with the mean of whole China. The diurnal variation amplitude declines gradually from south to north of China, with the largest amplitude in weastern China. The peak time of hourly precipitation has the characteristics of spatial concentration. The night peak is mainly concentrated in North China, Northeast China and southern coastal areas of China, while the morning-to-forenoon peak is concentrated in the central, east, southwest and the parts of northwest of China. And the gradual delay and abrupt change in spatial distribution of precipitation peak time are closely related to land-sea distribution and large topography. The diurnal variation characteristics of the spatial proportion and frequency proportion of hourly precipitation peak time are similar, both featured with gentle peak in the morning and steep peak at night. This is because the time of the night peak is close to the time at different stations, but the time of the morning peak is not so. Furthermore, with the increasing extremeness, the main peak of frequency proportion at night increases significantly, but the main peak of spatial proportion at night is almost unchanged. This difference is because the change of frequency is mainly caused by the change of frequency at the same stations, rather than the difference between different stations.
Based on the hourly precipitation data from national meteorological stations of China and the definition method of extreme precipitation with percentile threshold, this paper makes a statistical study of the spatio-temperal distribution and diurnal variation of hourly precipitation in China from April to October in 1951-2021. The results show that the hourly precipitation thresholds of the main rainy season in China are large in the southeast but small in the northwest, and there are four large threshold value centers lo-cated in South China, the Circum-Bohai Region, the middle and lower reaches of the Yangtze River and the Sichuan Basin. With the increasing extremeness, the hourly precipitation threshold in northern China increases more significantly than that in southern China, and the large threshold center moves northward. On the monthly time scale, from the south to north of China, the month with the highest frequency of hourly precipitation is postponed from May to August and the latest month is in West China (September-October). As the extremeness increases, the month with the highest frequency of precipitation is postponed from June-July to July-August, and the regional differences are reduced. In terms of diurnal variation characteristics, the frequency proportion of hourly precipitation of China presents a main valley-peak cycle from afternoon to night and a sub-cycle from midnight to morning. With the increasing extremeness, the amplitude of the main cycle increases and the peak value of the sub-cycle decreases. From the perspective of different geographical locations, the peak time of extreme hourly precipitation in Sichuan Basin is in the early morning, while the peak time in other three areas is consistent with the mean of whole China. The diurnal variation amplitude declines gradually from south to north of China, with the largest amplitude in weastern China. The peak time of hourly precipitation has the characteristics of spatial concentration. The night peak is mainly concentrated in North China, Northeast China and southern coastal areas of China, while the morning-to-forenoon peak is concentrated in the central, east, southwest and the parts of northwest of China. And the gradual delay and abrupt change in spatial distribution of precipitation peak time are closely related to land-sea distribution and large topography. The diurnal variation characteristics of the spatial proportion and frequency proportion of hourly precipitation peak time are similar, both featured with gentle peak in the morning and steep peak at night. This is because the time of the night peak is close to the time at different stations, but the time of the morning peak is not so. Furthermore, with the increasing extremeness, the main peak of frequency proportion at night increases significantly, but the main peak of spatial proportion at night is almost unchanged. This difference is because the change of frequency is mainly caused by the change of frequency at the same stations, rather than the difference between different stations.
2024, 50(4):407-419.
DOI: 10.7519/j.issn.1000-0526.2024.022001
Abstract:
This article aims to understand the short-time severe rainfall events in the area of Sichuan and Chongqing more comprehensively, and provide references for improving operational forecast skills and numerical weather forecast skills. Based on a convection-scale ensemble forecast system, a short-time severe rainfall event that occurred in the area of Sichuan and Chongqing is selected, and then the ensemble sensitivity analyses of the average precipitation in the target region to the model initial values are carried out and the corresponding dynamic mechanisms are discussed. The results show that the distribution characteristics of sensitive areas correspond well with the synoptic systems that play a key role in the precipitation forecast of the target regions. The sensitive areas around the southwest vortex at 850 hPa and 700 hPa show positive and negative distribution characteristics, the left (right) side of the 500 hPa trough shows negative (positive) sensitive area, the high-level southwest jet area at 250 hPa (south side) shows positive (negative) sensitive area, and the corresponding areas corresponding with the front (back) of the front zone of the middle and low layers show positive (negative) sensitive area. These findings indicate that the stronger the northwest (southeast) wind in the negative (positive) sensitive area around the southwest vortex, the stronger the northwest (southeast) wind on the left (right) side of the trough, the stronger the southwest (northeast) wind in the upper jet stream zone (south), and the higher (lower) the pre-frontal (post-frontal) temperature is, the more favorable they are to the convergence upward movement in the southwest vortex, to the strengthening of the 500 hPa trough, to the strengthening of the 250 hPa divergence, to the increase of the temperature gradient in the frontal zone and to the strengthening of the frontal uplift, which finally result in positive impacts on the precipitation in the target regions.
This article aims to understand the short-time severe rainfall events in the area of Sichuan and Chongqing more comprehensively, and provide references for improving operational forecast skills and numerical weather forecast skills. Based on a convection-scale ensemble forecast system, a short-time severe rainfall event that occurred in the area of Sichuan and Chongqing is selected, and then the ensemble sensitivity analyses of the average precipitation in the target region to the model initial values are carried out and the corresponding dynamic mechanisms are discussed. The results show that the distribution characteristics of sensitive areas correspond well with the synoptic systems that play a key role in the precipitation forecast of the target regions. The sensitive areas around the southwest vortex at 850 hPa and 700 hPa show positive and negative distribution characteristics, the left (right) side of the 500 hPa trough shows negative (positive) sensitive area, the high-level southwest jet area at 250 hPa (south side) shows positive (negative) sensitive area, and the corresponding areas corresponding with the front (back) of the front zone of the middle and low layers show positive (negative) sensitive area. These findings indicate that the stronger the northwest (southeast) wind in the negative (positive) sensitive area around the southwest vortex, the stronger the northwest (southeast) wind on the left (right) side of the trough, the stronger the southwest (northeast) wind in the upper jet stream zone (south), and the higher (lower) the pre-frontal (post-frontal) temperature is, the more favorable they are to the convergence upward movement in the southwest vortex, to the strengthening of the 500 hPa trough, to the strengthening of the 250 hPa divergence, to the increase of the temperature gradient in the frontal zone and to the strengthening of the frontal uplift, which finally result in positive impacts on the precipitation in the target regions.
2024, 50(4):420-433.
DOI: 10.7519/j.issn.1000-0526.2023.103001
Abstract:
The stability of forecast refers to the consistency of multiple timeliness forecast conclusions issued at different times in the same period. It is an important aspect of the model system, and the large instability will cause trouble to users. In order to understand the stability of common operational models, the relative standard deviation index is used to calculate the magnitude of precipitation fluctuation, and the Flip-Flop index (FFnorm) is improved to measure the reversal degree of precipitation forecast trend in this paper. Besides, the stability of precipitation forecast in two global models (ECMWF, NCEP-GFS) and three regional models (CMA-MESO, CMA-SH9, HHUPS-ST) in six climate zones in China， is discussed on the basis of the two cases of the observed precipitation and the rainstorm and the above. The results are as follows. When there is precipitation, the relative standard deviation of multiple timeliness precipitation forecasts of global models is smaller than that of regional models. That is, the fluctuation of model precipitation forecast is small. The volatility of each model for the western part of the southwest region, the eastern part of the northeast region and southern part of South China is smaller, while that for the western part of the northwest region is larger. In terms of the change trend of multiple timeliness precipitation forecast, the stability of CMA-MESO, NCEP-GFS and ECMWF is better in the two cases, and the index of FFnorm is smaller than that of HHUPS-ST and CMA-SH9. Among them CMA-MESO has a more prom-inent stability effect in the forecast for Southwest China and parts of South China. The index of CMA-SH9 is the largest and the model forecast is unstable. Each model has a relatively large index in the middle and lower reaches of the Yangtze River, and the stability of multiple timeliness forecast is poor. When there is precipitation, the frequency of stable (monotonically increasing or decreasing or constant) trend of precipitation forecast of CMA-MESO is the most, followed by NCEP-GFS. Under the two precipitation conditions, the precipitation forecast of the two models for each region is that the number of monotonically increasing times is greater than the number of decreasing times, and the monotonically increasing characteristics of the CMA-MESO model are particularly significant. The above characteristics could provide some references for model debugging and forecast decision-making.
The stability of forecast refers to the consistency of multiple timeliness forecast conclusions issued at different times in the same period. It is an important aspect of the model system, and the large instability will cause trouble to users. In order to understand the stability of common operational models, the relative standard deviation index is used to calculate the magnitude of precipitation fluctuation, and the Flip-Flop index (FFnorm) is improved to measure the reversal degree of precipitation forecast trend in this paper. Besides, the stability of precipitation forecast in two global models (ECMWF, NCEP-GFS) and three regional models (CMA-MESO, CMA-SH9, HHUPS-ST) in six climate zones in China， is discussed on the basis of the two cases of the observed precipitation and the rainstorm and the above. The results are as follows. When there is precipitation, the relative standard deviation of multiple timeliness precipitation forecasts of global models is smaller than that of regional models. That is, the fluctuation of model precipitation forecast is small. The volatility of each model for the western part of the southwest region, the eastern part of the northeast region and southern part of South China is smaller, while that for the western part of the northwest region is larger. In terms of the change trend of multiple timeliness precipitation forecast, the stability of CMA-MESO, NCEP-GFS and ECMWF is better in the two cases, and the index of FFnorm is smaller than that of HHUPS-ST and CMA-SH9. Among them CMA-MESO has a more prom-inent stability effect in the forecast for Southwest China and parts of South China. The index of CMA-SH9 is the largest and the model forecast is unstable. Each model has a relatively large index in the middle and lower reaches of the Yangtze River, and the stability of multiple timeliness forecast is poor. When there is precipitation, the frequency of stable (monotonically increasing or decreasing or constant) trend of precipitation forecast of CMA-MESO is the most, followed by NCEP-GFS. Under the two precipitation conditions, the precipitation forecast of the two models for each region is that the number of monotonically increasing times is greater than the number of decreasing times, and the monotonically increasing characteristics of the CMA-MESO model are particularly significant. The above characteristics could provide some references for model debugging and forecast decision-making.
2024, 50(4):434-448.
DOI: 10.7519/j.issn.1000-0526.2023.061401
Abstract:
The circulation classification of 850 hPa hourly wind field in the rainy season in Hunan Province from April to September in 2021 is carried out by using the T-mode oblique rotating principal component analysis method. On this basis, the evaluation is carried out for the hourly precipitation forecast of Rapid Updating Cycle Assimilation and Forecasting System in South China (CMA-GD-R3) in the same period. The results show that the main circulation types affecting the rainy season in Hunan in 2021 are the southwest vortex shear type, the shear type, the southerly type at the edge of the subtropical high and the easterly type at the periphery of the typhoon. The model shows good forecasting ability for the clear-rainy accuracy rate and graded precipitation. The daily variations of clear-rainy accuracy rate and TS of hourly precipitation forecast of CMA-GD-R3 are obvious. The clear-rainy accuracy rate is higher in the night time than that during the day, the peak value of TS score for graded precipitatin appears in the morning, and the effects of rainfall nowcasting of all circulation types are better. The southwest vortex shear type, which has the highest frequency of short-term heavy precipitation, has the lowest accuracy. The southerly type at the edge of the subtropical high has relatively poor performance in heavier precipitation. The SAL test shows that the rainfall location forecast of the model in the cases of the southwest vortex shear type and the shear type is closer to the observation. The intensity forecast is weak first but then strong. The precipitation location forecast in the cases of the southerly type at the edge of the subtropical high is scattered, and the location forecast is unstable. The overall intensity is obviously weaker than the observation. The location forecast in the cases of the easterly type at the periphery of the typhoon is close to the observation in the short-time forecast, and the intensity forecast is significantly weaker. The SAL method can more objectively reflect the structure, intensity, and location deviation in the hourly precipitation forecast.
The circulation classification of 850 hPa hourly wind field in the rainy season in Hunan Province from April to September in 2021 is carried out by using the T-mode oblique rotating principal component analysis method. On this basis, the evaluation is carried out for the hourly precipitation forecast of Rapid Updating Cycle Assimilation and Forecasting System in South China (CMA-GD-R3) in the same period. The results show that the main circulation types affecting the rainy season in Hunan in 2021 are the southwest vortex shear type, the shear type, the southerly type at the edge of the subtropical high and the easterly type at the periphery of the typhoon. The model shows good forecasting ability for the clear-rainy accuracy rate and graded precipitation. The daily variations of clear-rainy accuracy rate and TS of hourly precipitation forecast of CMA-GD-R3 are obvious. The clear-rainy accuracy rate is higher in the night time than that during the day, the peak value of TS score for graded precipitatin appears in the morning, and the effects of rainfall nowcasting of all circulation types are better. The southwest vortex shear type, which has the highest frequency of short-term heavy precipitation, has the lowest accuracy. The southerly type at the edge of the subtropical high has relatively poor performance in heavier precipitation. The SAL test shows that the rainfall location forecast of the model in the cases of the southwest vortex shear type and the shear type is closer to the observation. The intensity forecast is weak first but then strong. The precipitation location forecast in the cases of the southerly type at the edge of the subtropical high is scattered, and the location forecast is unstable. The overall intensity is obviously weaker than the observation. The location forecast in the cases of the easterly type at the periphery of the typhoon is close to the observation in the short-time forecast, and the intensity forecast is significantly weaker. The SAL method can more objectively reflect the structure, intensity, and location deviation in the hourly precipitation forecast.
2024, 50(4):449-460.
DOI: 10.7519/j.issn.1000-0526.2023.082701
Abstract:
In order to improve the numerical modeling of vertical turbulent transport of water vapor and sensible heat in atmospheric boundary layer and also the simulation of fog, this paper adopts the three-dimensional non-hydrostatic WRF model, with the help of a scale-aware MYNN_SA scheme of both local and non-local turbulences, to simulate a dense foggy weather process that occurred in a broad region from North China to Jiang-Huai Region during 28-29 December 2017. Impacts of the scale-aware boundary-layer turbulent scheme on the development of stable boundary layer, the turbulent transport and the simulation of fog are focused in a model resolution from mesoscale to large eddy. Compared with the surface observations in China and the ERA5 data, the scale-aware MYNN_SA scheme can improve the results of sub-grid-scale turbulent mixing when model resolution approaches the gray-zone scale, which shows better fog density, spatial and temporal variation of the dense fog in comparison with the original MYNN scheme. Detailed vertical structures of the fog, liquid cloud water and temperature inversion are well simulated by the scale-aware MYNN_SA scheme.
In order to improve the numerical modeling of vertical turbulent transport of water vapor and sensible heat in atmospheric boundary layer and also the simulation of fog, this paper adopts the three-dimensional non-hydrostatic WRF model, with the help of a scale-aware MYNN_SA scheme of both local and non-local turbulences, to simulate a dense foggy weather process that occurred in a broad region from North China to Jiang-Huai Region during 28-29 December 2017. Impacts of the scale-aware boundary-layer turbulent scheme on the development of stable boundary layer, the turbulent transport and the simulation of fog are focused in a model resolution from mesoscale to large eddy. Compared with the surface observations in China and the ERA5 data, the scale-aware MYNN_SA scheme can improve the results of sub-grid-scale turbulent mixing when model resolution approaches the gray-zone scale, which shows better fog density, spatial and temporal variation of the dense fog in comparison with the original MYNN scheme. Detailed vertical structures of the fog, liquid cloud water and temperature inversion are well simulated by the scale-aware MYNN_SA scheme.
2024, 50(4):461-474.
DOI: 10.7519/j.issn.1000-0526.2023.053002
Abstract:
Taking the high temperature and summer drought areas of ratoon rice in the eastern part of Sichuan Basin as the study area, and based on the mechanism of the influence of meteorological conditions on the growth and development of ratoon rice during the axillary bud germination stage, this article explores the impact factors, pathways, and degrees of axillary bud germination with a structural equation model. Furthermore, combined with the membership function and analytic hierarchy process, a meteorological suitability model for axillary bud germination of ratoon rice is constructed, and the meteorological impact factors and changes in meteorological suitability of axillary bud germination stage of ratoon rice in the study area from 1981 to 2021 are analyzed. The results indicate that temperature, air humidity, and precipitation are key impact factors for axillary bud germination in the high temperature and summer drought areas of ratoon rice in eastern Sichuan Basin. The meteorological suitability model based on these factors can effectively evaluate the meteorological impact of axillary bud germination of ratoon rice. From 1981 〖JP2〗to 2021, the temperature suitability, air humidity suitability, and synthetical meteoro-〖JP〗logical suitability all showed a downward trend, while the precipitation suitability did not have a significant change trend. In general, the spatial distributions of temperature suitability, air humidity suitability, and synthetical meteorological suitability were characterized by “high in the west and low in the east”, while the precipitation suitability was distributed in the pattern of “high in the east and west, and low in the middle”. From 1981 to 2021, there was a significant upward trend in temperature 〖JP2〗and a downward trend in air humidity in the study area,〖JP〗 resulting in significant increases in the accumulated temperature causing harmful high temperatures (daily mean temperature ≥32℃) and the days of harmful low humidity (daily average relative humidity ≤65%). This is major cause for the overall downward trend in meteorological suitability of axillary bud germination stage of ratoon rice.
Taking the high temperature and summer drought areas of ratoon rice in the eastern part of Sichuan Basin as the study area, and based on the mechanism of the influence of meteorological conditions on the growth and development of ratoon rice during the axillary bud germination stage, this article explores the impact factors, pathways, and degrees of axillary bud germination with a structural equation model. Furthermore, combined with the membership function and analytic hierarchy process, a meteorological suitability model for axillary bud germination of ratoon rice is constructed, and the meteorological impact factors and changes in meteorological suitability of axillary bud germination stage of ratoon rice in the study area from 1981 to 2021 are analyzed. The results indicate that temperature, air humidity, and precipitation are key impact factors for axillary bud germination in the high temperature and summer drought areas of ratoon rice in eastern Sichuan Basin. The meteorological suitability model based on these factors can effectively evaluate the meteorological impact of axillary bud germination of ratoon rice. From 1981 〖JP2〗to 2021, the temperature suitability, air humidity suitability, and synthetical meteoro-〖JP〗logical suitability all showed a downward trend, while the precipitation suitability did not have a significant change trend. In general, the spatial distributions of temperature suitability, air humidity suitability, and synthetical meteorological suitability were characterized by “high in the west and low in the east”, while the precipitation suitability was distributed in the pattern of “high in the east and west, and low in the middle”. From 1981 to 2021, there was a significant upward trend in temperature 〖JP2〗and a downward trend in air humidity in the study area,〖JP〗 resulting in significant increases in the accumulated temperature causing harmful high temperatures (daily mean temperature ≥32℃) and the days of harmful low humidity (daily average relative humidity ≤65%). This is major cause for the overall downward trend in meteorological suitability of axillary bud germination stage of ratoon rice.
2024, 50(4):475-487.
DOI: 10.7519/j.issn.1000-0526.2023.121201
Abstract:
Based on the basic method of consistency evaluation between 〖JP2〗radar base data, this article analyzes〖JP〗 the influence of radar altitude difference, terrain blockage, noise, congestion, temporal and spatial overlap rate, attenuation, etc. on consistency evaluation algorithm result quality, and takes corresponding improvement measures, that is, using radar beam blockage percentage data to correct or directly eliminate overlapping points with blockage, eliminating the overlapping points with low SNR, incomplete filling and abnormality, adding the factors of temporal spatial overlap rate, and analyzing the impact of different threshold temporal and spatial overlap rates on the evaluation results. The improvement measures have improved the quality of the deviation mean and standard deviation in the consistency evaluation results. The improved algorithm is used to evaluate the radar system deviation of Yueyang Station and the consistency of radar echoes in Jiangsu and Anhui regions. The results show that the deviation value between the Yueyang Radar and the surrounding radars has obviously decreased after being maintained, returning to the normal level, and the standard deviation value has also decreased slightly. The average value of deviations between radars in Jiangsu and Anhui is mostly within 2 dB. The vector triangle composed of the deviation mean has a good closure, with standard deviation between 2.9 dB and 3.3 dB and correlation coefficient between 0.40 and 0.55.
Based on the basic method of consistency evaluation between 〖JP2〗radar base data, this article analyzes〖JP〗 the influence of radar altitude difference, terrain blockage, noise, congestion, temporal and spatial overlap rate, attenuation, etc. on consistency evaluation algorithm result quality, and takes corresponding improvement measures, that is, using radar beam blockage percentage data to correct or directly eliminate overlapping points with blockage, eliminating the overlapping points with low SNR, incomplete filling and abnormality, adding the factors of temporal spatial overlap rate, and analyzing the impact of different threshold temporal and spatial overlap rates on the evaluation results. The improvement measures have improved the quality of the deviation mean and standard deviation in the consistency evaluation results. The improved algorithm is used to evaluate the radar system deviation of Yueyang Station and the consistency of radar echoes in Jiangsu and Anhui regions. The results show that the deviation value between the Yueyang Radar and the surrounding radars has obviously decreased after being maintained, returning to the normal level, and the standard deviation value has also decreased slightly. The average value of deviations between radars in Jiangsu and Anhui is mostly within 2 dB. The vector triangle composed of the deviation mean has a good closure, with standard deviation between 2.9 dB and 3.3 dB and correlation coefficient between 0.40 and 0.55.
2024, 50(4):488-498.
DOI: 10.7519/j.issn.1000-0526.2023.121801
Abstract:
With the increasing number of X-band dual-polarization radar networks, making network observation of X-band dual-polarization radars and S-band dual-polarization radars has become more necessary. Based on the observation data of the severe convective weather in Beijing on 27 July 2021, the consistency of polarization parameters between the X-band radar network and S-band dual-polarization radar is quantitatively analyzed. The results indicate that Beijing X-band radar networks and S-band dual-polarization radar have a favorable consistency on reflectivity factor (Z), and the differences of differential reflectivity (ZDR) are concentrated near 0 dB, specific differential phase (KDP) has significant difference in the area where Z≥30 dBz. Based on the characteristics of the observed polarization parameter differences, two fusion mosaic methods of parameters are compared: one is direct fusion mosaic and the other is distance-weighted with an exponent. By analyzing vertical cross-section (VCS) of polarization parameters, we see that the blind area of radars could be made up for each other, and KDP can have a more natural transition through the fusion mosaic method distance-weighted with an exponent. The fusion effect could provide some references for different band radars needing fusion mosaic.
With the increasing number of X-band dual-polarization radar networks, making network observation of X-band dual-polarization radars and S-band dual-polarization radars has become more necessary. Based on the observation data of the severe convective weather in Beijing on 27 July 2021, the consistency of polarization parameters between the X-band radar network and S-band dual-polarization radar is quantitatively analyzed. The results indicate that Beijing X-band radar networks and S-band dual-polarization radar have a favorable consistency on reflectivity factor (Z), and the differences of differential reflectivity (ZDR) are concentrated near 0 dB, specific differential phase (KDP) has significant difference in the area where Z≥30 dBz. Based on the characteristics of the observed polarization parameter differences, two fusion mosaic methods of parameters are compared: one is direct fusion mosaic and the other is distance-weighted with an exponent. By analyzing vertical cross-section (VCS) of polarization parameters, we see that the blind area of radars could be made up for each other, and KDP can have a more natural transition through the fusion mosaic method distance-weighted with an exponent. The fusion effect could provide some references for different band radars needing fusion mosaic.
2024, 50(4):499-513.
DOI: 10.7519/j.issn.1000-0526.2024.022602
Abstract:
Based on the NCEP/NCAR reanalysis data and climate observations from 2400 stations of China, the characteristics of climatic anomalies over China in autumn 2023 and the possible causes are analyzed. The results denote that, in autumn 2023, the average temperature in China peaked the record in the same period since 1961, and the average precipitation was close to the climatic mean, but had uneven spatial distribution and significant intra-seasonal variability. The circulation in the mid-high latitudes of Eurasia showed a “negative-positive-negative” pattern on the seasonal mean scale, leading to the abnormal warming in China. In September, the circulation was in a “positive-negative-positive” pattern that caused the frequent activity of the trough near Balkhash Lake and the increase of precipitation in Northwest China; in October, the “negative-positive-negative” pattern of circulation caused further warming in northern China; and in November the circulation pattern of “positive in west and negative in east” formed, enhancing the cold air in the east and causing the temperature in Northeast 〖JP2〗China to drop to below normal and precipitation〖JP〗 to be more than normal. The Western Pacific subtropical high (WPSH) was stronger and more westward than usual overall, and its ridge line swung frequently in the meridional direction, that is, the ridge line was abnormally further north than usual in September, further south than usual in October and close to normal position in November. The India-Burma trough was significantly stronger in September and near normal during October-November. In September, the stronger Indo-Burma trough and the northerly WPSH jointly contributed to the heavy〖JP2〗 rainfall in the region between the middle and lower reaches of Yangtze〖JP〗 River and the lower reaches of Yellow River. The basic water vapor transport condition in eastern China became negative from October to November. In addition, typhoon activities in southern coastal area of China were frequent in September and October, resulting in more precipitation in South China. These results reveal that the climate anomaly in autumn 2023 was significantly affected by the intra-seasonal variation of the atmosphere, and it did not match the typical responses to the tropical SST anomaly.
Based on the NCEP/NCAR reanalysis data and climate observations from 2400 stations of China, the characteristics of climatic anomalies over China in autumn 2023 and the possible causes are analyzed. The results denote that, in autumn 2023, the average temperature in China peaked the record in the same period since 1961, and the average precipitation was close to the climatic mean, but had uneven spatial distribution and significant intra-seasonal variability. The circulation in the mid-high latitudes of Eurasia showed a “negative-positive-negative” pattern on the seasonal mean scale, leading to the abnormal warming in China. In September, the circulation was in a “positive-negative-positive” pattern that caused the frequent activity of the trough near Balkhash Lake and the increase of precipitation in Northwest China; in October, the “negative-positive-negative” pattern of circulation caused further warming in northern China; and in November the circulation pattern of “positive in west and negative in east” formed, enhancing the cold air in the east and causing the temperature in Northeast 〖JP2〗China to drop to below normal and precipitation〖JP〗 to be more than normal. The Western Pacific subtropical high (WPSH) was stronger and more westward than usual overall, and its ridge line swung frequently in the meridional direction, that is, the ridge line was abnormally further north than usual in September, further south than usual in October and close to normal position in November. The India-Burma trough was significantly stronger in September and near normal during October-November. In September, the stronger Indo-Burma trough and the northerly WPSH jointly contributed to the heavy〖JP2〗 rainfall in the region between the middle and lower reaches of Yangtze〖JP〗 River and the lower reaches of Yellow River. The basic water vapor transport condition in eastern China became negative from October to November. In addition, typhoon activities in southern coastal area of China were frequent in September and October, resulting in more precipitation in South China. These results reveal that the climate anomaly in autumn 2023 was significantly affected by the intra-seasonal variation of the atmosphere, and it did not match the typical responses to the tropical SST anomaly.
2024, 50(4):514-520.
DOI: 10.7519/j.issn.1000-0526.2024.032901
Abstract:
The main characteristics of the general atmospheric circulation in January 2024 are as follows. There were two polar vortex centers in the Northern Hemisphere. The Eurasian mid- and high-latitude circulation showed a two-trough-one-ridge pattern. The East Asian trough was more eastward. The monthly mean precipitation (16.3 mm) over China was 15.6% more than normal (14.1 mm). The monthly average temperature was -3.8℃, which was 1.0℃ higher than that in the same period of normal years. Cold and warm temperatures fluctuated greatly during the month. There was one nationwide cold wave process and two widespread persistent fog-haze weather processes, among which the cold wave weather process from 20 to 22 January presented the characteristics of a wide range of influence, and cooling, long duration of strong wind and heavy snowstorm.
The main characteristics of the general atmospheric circulation in January 2024 are as follows. There were two polar vortex centers in the Northern Hemisphere. The Eurasian mid- and high-latitude circulation showed a two-trough-one-ridge pattern. The East Asian trough was more eastward. The monthly mean precipitation (16.3 mm) over China was 15.6% more than normal (14.1 mm). The monthly average temperature was -3.8℃, which was 1.0℃ higher than that in the same period of normal years. Cold and warm temperatures fluctuated greatly during the month. There was one nationwide cold wave process and two widespread persistent fog-haze weather processes, among which the cold wave weather process from 20 to 22 January presented the characteristics of a wide range of influence, and cooling, long duration of strong wind and heavy snowstorm.
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ISSN:1000-0526 CN:11-2282/P