ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 45,Issue 12,2019 Table of Contents
2019, 45(12):1629-1641.
DOI: 10.7519/j.issn.1000-0526.2019.12.001
Abstract:
The China Meteorological Administration Numerical Weather Prediction Centre has established the GRAPESREPS (Global and Regional Assimilation and Prediction Enhanced SystemRegional Ensemble Prediction System) business system since 2014. The lateral boundary perturbation is obtained by the global ensemble prediction system. In order to understand the impact of lateral boundary perturbation on GRAPES regional ensemble prediction, this paper, based on the GRAPESREPS regional ensemble prediction model with 15 km horizontal resolution, constructed two lateral boundary perturbation schemes using the scaled lagged average forecasting (SLAF) method and the dynamic downscaling method. Two kinds of lateral boundary perturbation experiments were designed. The 6 d ensemble prediction test was carried out in July 2015. Using root mean square error (RMSE), spread, CRPS, Outlier, Brier score, TS, AROC and other probabilistic forecast test, the impacts of the two kinds of lateral boundary perturbation methods on the regional ensemble prediction quality were analyzed. The results showed that the energy of the lateral boundary perturbation obtained by dynamic downscaling (DOWN) is greater than that of the SLAF experiment at each vertical layer, resulting in the spread of DOWN experiment greater than the dispersion of SLAF experiment. For the isobaric elements and the ground elements, the scores of DOWN experiment are better than the scores of SLAF experiment, indicating that the lateral boundary perturbation of the DOWN experiment structure is more reasonable. In the aspect of precipitation probability prediction skill, the SLAF experiment has certain advantages in scoring, but the improvement of the score does not pass the significance test, so the two experiments are considered to be similar in the improvement of precipitation forecast.
The China Meteorological Administration Numerical Weather Prediction Centre has established the GRAPESREPS (Global and Regional Assimilation and Prediction Enhanced SystemRegional Ensemble Prediction System) business system since 2014. The lateral boundary perturbation is obtained by the global ensemble prediction system. In order to understand the impact of lateral boundary perturbation on GRAPES regional ensemble prediction, this paper, based on the GRAPESREPS regional ensemble prediction model with 15 km horizontal resolution, constructed two lateral boundary perturbation schemes using the scaled lagged average forecasting (SLAF) method and the dynamic downscaling method. Two kinds of lateral boundary perturbation experiments were designed. The 6 d ensemble prediction test was carried out in July 2015. Using root mean square error (RMSE), spread, CRPS, Outlier, Brier score, TS, AROC and other probabilistic forecast test, the impacts of the two kinds of lateral boundary perturbation methods on the regional ensemble prediction quality were analyzed. The results showed that the energy of the lateral boundary perturbation obtained by dynamic downscaling (DOWN) is greater than that of the SLAF experiment at each vertical layer, resulting in the spread of DOWN experiment greater than the dispersion of SLAF experiment. For the isobaric elements and the ground elements, the scores of DOWN experiment are better than the scores of SLAF experiment, indicating that the lateral boundary perturbation of the DOWN experiment structure is more reasonable. In the aspect of precipitation probability prediction skill, the SLAF experiment has certain advantages in scoring, but the improvement of the score does not pass the significance test, so the two experiments are considered to be similar in the improvement of precipitation forecast.
2019, 45(12):1642-1650.
DOI: 10.7519/j.issn.1000-0526.2019.12.002
Abstract:
A torrential rainfall event occurred in Guangzhou on 7 May 2017. In order to study the impact of different background field data on the simulation of rainstorm process, the NCEP Global Forecast System (GFS) data and CMA T639 data were used separately to develop lateral boundary and initial conditions for the numerical simulation and impact analysis of the rainstorm with the GRAPES_Meso model. The results indicated that background fields have significant impact on the simulation of rainstorm process. The precipitation forecasts using T639 data (T639_run) as initial and boundary conditions seem to be roughly simulated, while the location of the rainfall simulated by GFS data (GFS_run) is obviously northerly. The reason is that there is a deep water vapor transport and strong ascending motion in the rainstorm area of South China using T639 data as the background field, which can produce extremely heavy rainfall. The updraft and water vapor transport are weak in the actual storm area simulated by GFS data, making the heavy precipitation area northerly. Overall, the height of cloud top is higher and the temperature of cloud top is lower simulated by GRAPES_Meso model. Relatively speaking, the simulation result using T639_run is better than using GFS_run. This research result could provide a reference for the improvement and optimization of the calculation about the water substances and cloud fraction in cloud schemes.
A torrential rainfall event occurred in Guangzhou on 7 May 2017. In order to study the impact of different background field data on the simulation of rainstorm process, the NCEP Global Forecast System (GFS) data and CMA T639 data were used separately to develop lateral boundary and initial conditions for the numerical simulation and impact analysis of the rainstorm with the GRAPES_Meso model. The results indicated that background fields have significant impact on the simulation of rainstorm process. The precipitation forecasts using T639 data (T639_run) as initial and boundary conditions seem to be roughly simulated, while the location of the rainfall simulated by GFS data (GFS_run) is obviously northerly. The reason is that there is a deep water vapor transport and strong ascending motion in the rainstorm area of South China using T639 data as the background field, which can produce extremely heavy rainfall. The updraft and water vapor transport are weak in the actual storm area simulated by GFS data, making the heavy precipitation area northerly. Overall, the height of cloud top is higher and the temperature of cloud top is lower simulated by GRAPES_Meso model. Relatively speaking, the simulation result using T639_run is better than using GFS_run. This research result could provide a reference for the improvement and optimization of the calculation about the water substances and cloud fraction in cloud schemes.
2019, 45(12):1651-1665.
DOI: 10.7519/j.issn.1000-0526.2019.12.003
Abstract:
Based on the NCEP/NCAR reanalysis data and Hadley sea ice concentration data, the winter variation characteristics of Siberian high (SH) south boundary eastern segment (SHSBES) and its relationship with Arctic sea ice during 1951-2017 were analyzed, and the intraseasonal differences were also discussed. The results showed that SHSBES in winter moves to the north from south in the mid1960s, and transfers to the south in the late 1970s, then turns a little southerly than the normal location since 1990s. The interdecadal transition time of SHSBES in December is earlier, the interdecadal variations of SHSBES in January and February of the following year are similar to the one in winter. SHSBES in winter is most closely related to the homochronous Atlantic sector Arctic sea ice whose decreases can induce the appearance of Baikal Lake blocking high in winter. SHSBES in December is most influenced by Atlantic sector Arctic sea ice in September, and the Western Hemisphere Arctic sea ice in March has the most significant impact on SHSBES in January and February of the next year. Less sea ice of the former results in the blocking high of September in Western Europe, and the reduction of the latter brings about the blocking high on the west site of Baikal in January. Three blocking highs are located respectively in Western Europe, Baikal and Kamchatka Peninsula in February during the ensuing year. Under the dynamic action of the atmospheric blocking, the southeast of SH and its south region are situated in a negative zone of the relative vorticity advection, the surface pressure increases with the downdraft, which is favorable for the southward movement of SHSBES, and vice versa. The decrease (increase) of Atlantic sector Arctic sea ice in September and Western Hemisphere Arctic sea ice in March can cause the southeast of SH and its south region to become colder (warmer) in December and the next year’s February respectively, facilitating the increase (decrease) of surface pressure, ultimately leading SHSBES into the south (north).
Based on the NCEP/NCAR reanalysis data and Hadley sea ice concentration data, the winter variation characteristics of Siberian high (SH) south boundary eastern segment (SHSBES) and its relationship with Arctic sea ice during 1951-2017 were analyzed, and the intraseasonal differences were also discussed. The results showed that SHSBES in winter moves to the north from south in the mid1960s, and transfers to the south in the late 1970s, then turns a little southerly than the normal location since 1990s. The interdecadal transition time of SHSBES in December is earlier, the interdecadal variations of SHSBES in January and February of the following year are similar to the one in winter. SHSBES in winter is most closely related to the homochronous Atlantic sector Arctic sea ice whose decreases can induce the appearance of Baikal Lake blocking high in winter. SHSBES in December is most influenced by Atlantic sector Arctic sea ice in September, and the Western Hemisphere Arctic sea ice in March has the most significant impact on SHSBES in January and February of the next year. Less sea ice of the former results in the blocking high of September in Western Europe, and the reduction of the latter brings about the blocking high on the west site of Baikal in January. Three blocking highs are located respectively in Western Europe, Baikal and Kamchatka Peninsula in February during the ensuing year. Under the dynamic action of the atmospheric blocking, the southeast of SH and its south region are situated in a negative zone of the relative vorticity advection, the surface pressure increases with the downdraft, which is favorable for the southward movement of SHSBES, and vice versa. The decrease (increase) of Atlantic sector Arctic sea ice in September and Western Hemisphere Arctic sea ice in March can cause the southeast of SH and its south region to become colder (warmer) in December and the next year’s February respectively, facilitating the increase (decrease) of surface pressure, ultimately leading SHSBES into the south (north).
2019, 45(12):1666-1679.
DOI: 10.7519/j.issn.1000-0526.2019.12.004
Abstract:
Himawari-8 is a new generation of geostationary meteorological satellite launched by Japan. Compared with the previous generation of MTSAT-2, it has greatly improved its spatio-temporal resolution. The number of infrared channels of Himawari-8 is increased from 4 to 10 compared with MTSAT-2, providing new observation data for infrared remote sensing of dust. This research makes full use of Himawari-8 infrared observation data and develops an all-day dust identification algorithm using only infrared channels, which can realize continuous monitoring during the day and night. The algorithm is based on previous algorithms, and does not use visible light channels, but uses more infrared channels for cloud detection and dust recognition. As surface temperature changes during the day, two different sets of discriminant thresholds are set up for daytime and nighttime to ensure the applicability of the algorithm for the whole day. Finally, two dust events are used to verify the results of dust discrimination. The consistency between ground-based and remote sensing results shows that it is feasible to use the infrared channel to identify sand and dust all day.
Himawari-8 is a new generation of geostationary meteorological satellite launched by Japan. Compared with the previous generation of MTSAT-2, it has greatly improved its spatio-temporal resolution. The number of infrared channels of Himawari-8 is increased from 4 to 10 compared with MTSAT-2, providing new observation data for infrared remote sensing of dust. This research makes full use of Himawari-8 infrared observation data and develops an all-day dust identification algorithm using only infrared channels, which can realize continuous monitoring during the day and night. The algorithm is based on previous algorithms, and does not use visible light channels, but uses more infrared channels for cloud detection and dust recognition. As surface temperature changes during the day, two different sets of discriminant thresholds are set up for daytime and nighttime to ensure the applicability of the algorithm for the whole day. Finally, two dust events are used to verify the results of dust discrimination. The consistency between ground-based and remote sensing results shows that it is feasible to use the infrared channel to identify sand and dust all day.
2019, 45(12):1680-1690.
DOI: 10.7519/j.issn.1000-0526.2019.12.005
Abstract:
Based on the observations from 500 quality-controlled rain gauges, the applicability of the tropical rainfall measuring mission (TRMM) multi-satellite precipitation analysis (TMPA) and integrated multi-satellite retrievals for global precipitation measurement (GPM) mission (IMERG) products to the precipitation in mid-eastern China during the summer of period 2014-2016 was analyzed, from the aspects of spatio-temporal distribution patterns, regional factors, rainfall intensities, and diurnal cycles. Statistical analysis showed that TMPA and IMERG have the similar daily variations of rainfall compared to gauge observations, and the mean errors are much smaller for IMERG. IMERG exhibits much stronger linear correlations (>0.9) with rain gauge observations than TMPA (0.8) at the daily scale. IMERG shows superior skill in estimating light rainfall (< 4 mm·d-1) and detecting light precipitation events, compared with TMPA over both plain and mountain regions. However, no clear improvement is found in detecting heavy rainfall events over mountain regions. For precipitation diurnal cycles, TMPA underestimates the early morning rain intensity and rain frequency, but overestimates those in the late-afternoon. As a high spatio-temporal precipitation dataset, IMERG performs well over mid-eastern China, and can be applied in meteo-rological and hydrological models in the future.
Based on the observations from 500 quality-controlled rain gauges, the applicability of the tropical rainfall measuring mission (TRMM) multi-satellite precipitation analysis (TMPA) and integrated multi-satellite retrievals for global precipitation measurement (GPM) mission (IMERG) products to the precipitation in mid-eastern China during the summer of period 2014-2016 was analyzed, from the aspects of spatio-temporal distribution patterns, regional factors, rainfall intensities, and diurnal cycles. Statistical analysis showed that TMPA and IMERG have the similar daily variations of rainfall compared to gauge observations, and the mean errors are much smaller for IMERG. IMERG exhibits much stronger linear correlations (>0.9) with rain gauge observations than TMPA (0.8) at the daily scale. IMERG shows superior skill in estimating light rainfall (< 4 mm·d-1) and detecting light precipitation events, compared with TMPA over both plain and mountain regions. However, no clear improvement is found in detecting heavy rainfall events over mountain regions. For precipitation diurnal cycles, TMPA underestimates the early morning rain intensity and rain frequency, but overestimates those in the late-afternoon. As a high spatio-temporal precipitation dataset, IMERG performs well over mid-eastern China, and can be applied in meteo-rological and hydrological models in the future.
2019, 45(12):1691-1699.
DOI: 10.7519/j.issn.1000-0526.2019.12.006
Abstract:
Based on the precipitable water vapor (PWV) data observed by Global Positioning System (GPS), the radiosonde data and daily precipitation data and employing several statistical methods, characteristics of summer PWV over the Tianshan Mountains and their possible reasons were analyzed. For the distribution of summer PWV average, remarkable differences exist among stations over the Tianshan Mountains, and there is a significant negative relationship between PWV and station altitude. The PWV at lower altitudes exhibits more variabilities and divergences than that at higher altitudes. The extreme and median of PWV in rainy days exceed those in rainless days. The daily and monthly variations of summer PWV are considerable, and most stations present maximum in July and minimum in August. As to diurnal variation, most stations have maximum at about 10 o’clock while some individual stations exhibit opposite features, and discrepancies still exit between rainy days and rainless days. There is no direct correlation between precipitation and PWV. However, precipitation and water cycle index are positively related to station altitude, which maybe be attributed to more local convective precipitation processes over higher mountains in summer and more water cycle frequencies.
Based on the precipitable water vapor (PWV) data observed by Global Positioning System (GPS), the radiosonde data and daily precipitation data and employing several statistical methods, characteristics of summer PWV over the Tianshan Mountains and their possible reasons were analyzed. For the distribution of summer PWV average, remarkable differences exist among stations over the Tianshan Mountains, and there is a significant negative relationship between PWV and station altitude. The PWV at lower altitudes exhibits more variabilities and divergences than that at higher altitudes. The extreme and median of PWV in rainy days exceed those in rainless days. The daily and monthly variations of summer PWV are considerable, and most stations present maximum in July and minimum in August. As to diurnal variation, most stations have maximum at about 10 o’clock while some individual stations exhibit opposite features, and discrepancies still exit between rainy days and rainless days. There is no direct correlation between precipitation and PWV. However, precipitation and water cycle index are positively related to station altitude, which maybe be attributed to more local convective precipitation processes over higher mountains in summer and more water cycle frequencies.
2019, 45(12):1700-1709.
DOI: 10.7519/j.issn.1000-0526.2019.12.007
Abstract:
The effects of different scales of turbulent vortices in vertical direction on entrainment process and vertical transmission of tracers were studied, and the role of model vertical resolution in the analysis of simulation results was clarified by using field dense observation data in Dunhuang and large eddy model (LEM). The results showed that, in the vertical direction, the small-scale turbulence contributes more to the entrainment, and when small-scale turbulences are more, the clamping layer is even warmer. However, the thickness, strength and wind speed of the clamping layer are less affected by the scale of vertical direction turbulent vortices. Over the upper part of the entrainment layer, there are more updrafts and downdrafts with stronger intensities in the 50 m vertical resolution test. The distributions of vertical velocities, potential temperature and tracer concentration at different heights of the clamping layer are similar in the 10 m, 20 m and 30 m vertical resolution tests. In addition, the scales of vertical turbulent vortices affect the tracer vertical transport height slighty, but has a certain effect on the spatial distribution of tracer. When the large-scale turbulences are more and stronger, they are more favorable for the vertical transmissions of high-concentration tracers. Considering the noise generated in the simulation process and the longer computing time during the high resolution simulations, we use the 30 m grid spacing as LEM vertical resolution in simulating, which is an ideal choice. In such a case, the model can simulate not only the average structure of the entrainment layer, but also the very fine turbulence distribution in the clamping layer.
The effects of different scales of turbulent vortices in vertical direction on entrainment process and vertical transmission of tracers were studied, and the role of model vertical resolution in the analysis of simulation results was clarified by using field dense observation data in Dunhuang and large eddy model (LEM). The results showed that, in the vertical direction, the small-scale turbulence contributes more to the entrainment, and when small-scale turbulences are more, the clamping layer is even warmer. However, the thickness, strength and wind speed of the clamping layer are less affected by the scale of vertical direction turbulent vortices. Over the upper part of the entrainment layer, there are more updrafts and downdrafts with stronger intensities in the 50 m vertical resolution test. The distributions of vertical velocities, potential temperature and tracer concentration at different heights of the clamping layer are similar in the 10 m, 20 m and 30 m vertical resolution tests. In addition, the scales of vertical turbulent vortices affect the tracer vertical transport height slighty, but has a certain effect on the spatial distribution of tracer. When the large-scale turbulences are more and stronger, they are more favorable for the vertical transmissions of high-concentration tracers. Considering the noise generated in the simulation process and the longer computing time during the high resolution simulations, we use the 30 m grid spacing as LEM vertical resolution in simulating, which is an ideal choice. In such a case, the model can simulate not only the average structure of the entrainment layer, but also the very fine turbulence distribution in the clamping layer.
2019, 45(12):1710-1717.
DOI: 10.7519/j.issn.1000-0526.2019.12.008
Abstract:
Using the forecasting radar echo data from GRAPES_3 km (Global/Regional Assimilation and Prediction System) and WRFRUC (Weather Research and Forecast Rapid Update Cycle) of July and August in 2018, the real radar echo data from SWAN (MCR), and FSS (fractions skill score), the radar echo forecast abilities of two high-resolution models for typhoon and subtropical anticyclone were analyzed. The results showed that the two models have better skill for weak radar echo forecast, with increase of radar echo, the forecasting skill score decreases. When radar echo reaches 55 dBz, FSS even is equal to zero. When spatial neighborhood radius is 3, the forecast is less skillfull in the typhoon rainstorm than subtropical anticyclone rainstorm with radar echo lower than 35 dBz. If radar echo is bigger than 35 dBz, it is in contrast. The forecasting of radar echo by WRFRUC model is always better for typhoon rainstorm than for subtropical anticyclone rainstorm. When spatial neighborhood radius increases to 9, the echo forecasting FSS of WRFRUC model is higher than that of GRAPES model in typhoon rain, but in subtropical anticyclone rainstorm, GRAPES model has the higher skill than WRFRUC model. The biggest FSSs of GRAPES and WRFRUC models appear at the spatial neighborhood radius of 11, and the values are 0.239 and 0.195, respectively. In the first three hours of the forecasting, FSS is bigger than in other hours for the GRAPES model. In the middle hours of the echo forecasting of WRFRUC model, FSS is higher than in other hours.
Using the forecasting radar echo data from GRAPES_3 km (Global/Regional Assimilation and Prediction System) and WRFRUC (Weather Research and Forecast Rapid Update Cycle) of July and August in 2018, the real radar echo data from SWAN (MCR), and FSS (fractions skill score), the radar echo forecast abilities of two high-resolution models for typhoon and subtropical anticyclone were analyzed. The results showed that the two models have better skill for weak radar echo forecast, with increase of radar echo, the forecasting skill score decreases. When radar echo reaches 55 dBz, FSS even is equal to zero. When spatial neighborhood radius is 3, the forecast is less skillfull in the typhoon rainstorm than subtropical anticyclone rainstorm with radar echo lower than 35 dBz. If radar echo is bigger than 35 dBz, it is in contrast. The forecasting of radar echo by WRFRUC model is always better for typhoon rainstorm than for subtropical anticyclone rainstorm. When spatial neighborhood radius increases to 9, the echo forecasting FSS of WRFRUC model is higher than that of GRAPES model in typhoon rain, but in subtropical anticyclone rainstorm, GRAPES model has the higher skill than WRFRUC model. The biggest FSSs of GRAPES and WRFRUC models appear at the spatial neighborhood radius of 11, and the values are 0.239 and 0.195, respectively. In the first three hours of the forecasting, FSS is bigger than in other hours for the GRAPES model. In the middle hours of the echo forecasting of WRFRUC model, FSS is higher than in other hours.
2019, 45(12):1718-1726.
DOI: 10.7519/j.issn.1000-0526.2019.12.009
Abstract:
Atmospheric heat source is one of the main points of the theory of plateau meteorology. The studies on its calculation method and applicability are of great significance to deepen the understanding of plateau meteorology and broaden the horizon of students of this course. The precise calculation of atmospheric heat source remains a challenge. We introduced two methods for calculating the atmospheric heat sources in detail. Based on historical observations of meterological stations, satellite-based radiation datasets (ISCCP and SRB) and four reanalysis datasets (NCEP/NCAR, NCEP/DOE, ERA-Interim and JRA55), we calculated the atmospheric heat sources in summer season over the Tibetan Plateau and compared their differences in multiscale vaiabilities. The results showed that radiation data should be carefully selected in calculating the atmospheric column energy budget. When the atmospheric apparent heat sources are calculated, the reanalysis date should be carefully selected according to the focus of the timescale owing to their quite different performances. In terms of the long-term trend, <Q1>-JRA55 is the closest to observations; on the interannual time scale, the results of <Q1>-ERAI and <Q1>-JRA55 can repeat the variability of the heat source from observations; and on the intraseasonal oscillation, the differences of multiple sets of reanalysis data have been narrowed, and they all can be used well to describe the changes of the heat source over the Tibetan Plateau.
Atmospheric heat source is one of the main points of the theory of plateau meteorology. The studies on its calculation method and applicability are of great significance to deepen the understanding of plateau meteorology and broaden the horizon of students of this course. The precise calculation of atmospheric heat source remains a challenge. We introduced two methods for calculating the atmospheric heat sources in detail. Based on historical observations of meterological stations, satellite-based radiation datasets (ISCCP and SRB) and four reanalysis datasets (NCEP/NCAR, NCEP/DOE, ERA-Interim and JRA55), we calculated the atmospheric heat sources in summer season over the Tibetan Plateau and compared their differences in multiscale vaiabilities. The results showed that radiation data should be carefully selected in calculating the atmospheric column energy budget. When the atmospheric apparent heat sources are calculated, the reanalysis date should be carefully selected according to the focus of the timescale owing to their quite different performances. In terms of the long-term trend, <Q1>-JRA55 is the closest to observations; on the interannual time scale, the results of <Q1>-ERAI and <Q1>-JRA55 can repeat the variability of the heat source from observations; and on the intraseasonal oscillation, the differences of multiple sets of reanalysis data have been narrowed, and they all can be used well to describe the changes of the heat source over the Tibetan Plateau.
2019, 45(12):1727-1735.
DOI: 10.7519/j.issn.1000-0526.2019.12.010
Abstract:
Sounding observation data are the most basic and important data source in weather forecast and numerical weather prediction. Vaisala Radiosonde 92/90 data account for a large proportion of this kind of observation. The quality of the humidity observation data directly affects the assimilation analysis and model forecast, so it is necessary to evaluate the quality of the data and correct the deviation. The humidity observation deviation of RS92/90 detector is found by comparing the humidity field of NCEP with EC reanalysis. Based on the deviation correction scheme of Yoneyama et al (2008) for the humidity observation of the instrument, the revised scheme, which is the most significant for the analysis and improvement and takes into account the influence of solar radiation and other factors, is selected from the comparison of several revised schemes. The scheme is applied to GRAPES-GFS test. The experimental results show that after the deviation of humidity observation for the RS92/90 sounding is corrected, the assimilation analysis and prediction have neutral effect. After the correction of prediction anomaly correlation in continuous experiments, there is an improvement in East Asia and the Tropics. The forecast score is slightly improved in these areas, so the correction scheme of humidity observation deviation of RS92/90 sounding instrument has its application value in practical operation.
Sounding observation data are the most basic and important data source in weather forecast and numerical weather prediction. Vaisala Radiosonde 92/90 data account for a large proportion of this kind of observation. The quality of the humidity observation data directly affects the assimilation analysis and model forecast, so it is necessary to evaluate the quality of the data and correct the deviation. The humidity observation deviation of RS92/90 detector is found by comparing the humidity field of NCEP with EC reanalysis. Based on the deviation correction scheme of Yoneyama et al (2008) for the humidity observation of the instrument, the revised scheme, which is the most significant for the analysis and improvement and takes into account the influence of solar radiation and other factors, is selected from the comparison of several revised schemes. The scheme is applied to GRAPES-GFS test. The experimental results show that after the deviation of humidity observation for the RS92/90 sounding is corrected, the assimilation analysis and prediction have neutral effect. After the correction of prediction anomaly correlation in continuous experiments, there is an improvement in East Asia and the Tropics. The forecast score is slightly improved in these areas, so the correction scheme of humidity observation deviation of RS92/90 sounding instrument has its application value in practical operation.
2019, 45(12):1736-1746.
DOI: 10.7519/j.issn.1000-0526.2019.12.011
Abstract:
Four semi-winter wheat varieties Tanmai 98, Shannong 18, Xumai 33 and Wanmai 52 in Huanghuaihai winter wheat area were selected as test materials. Through the sowing date tests, the trends of grain filling rate and the influence of meteorological factors on the filling rate were analyzed by means of analysis of variance, correlation analysis, stepwise regression and path analysis. The results showed that the fluctuation of grain filling rate is the least and the 1000-grain weight is the highest in the normal sowing period, the late-sowed 10 d winter wheat has the highest volatility and smallest 1000-grain weight. The grain filling rate of Tanmai 98 is most stable and the 1000-grain weight is the highest in winter wheat area of North China, while the grain filling rate of Wanmai 52 is the highest in Huanghuai winter wheat area. The grain filling of semi-winter wheat usually lasts 35-39 days. The climate difference between north and south is one of the reasons for the different filling rates of winter wheat. The variation trends of the filling rate of semi-winter wheat in each sowing period are the same, and the change of filling rate is consistent with the change law of related significant meteorological factors. The peak period of grain filling generally appears 15-25 days later than flowering, and the appearance time is earlier of the maximum fil-ling rate of late-sowed winter wheat than the control treatment, which is not conducive to increasing the grain weight. The temperature conditions have significant effects on the grain filling rate of winter wheat, of which the highest temperature factor is the common key factor affecting the filling rate of different sowing dates and varieties. Path analysis showed that the effect of maximum temperature on filling rate is determined by its direct effect, while the effect of sunshine hours and minimum temperature on filling rate is consistent with indirect effect. The average of highest temperature has the most important effect on fil-ling rate, while the sunshine time and averaged minimum temperature influence the filling rate weakly. The averages of highest and lowest temperature and the sunshine hours are the limiting factors of the filling rate, of which the average of highest temperature has the greatest decision-making effect on the change of filling rate.
Four semi-winter wheat varieties Tanmai 98, Shannong 18, Xumai 33 and Wanmai 52 in Huanghuaihai winter wheat area were selected as test materials. Through the sowing date tests, the trends of grain filling rate and the influence of meteorological factors on the filling rate were analyzed by means of analysis of variance, correlation analysis, stepwise regression and path analysis. The results showed that the fluctuation of grain filling rate is the least and the 1000-grain weight is the highest in the normal sowing period, the late-sowed 10 d winter wheat has the highest volatility and smallest 1000-grain weight. The grain filling rate of Tanmai 98 is most stable and the 1000-grain weight is the highest in winter wheat area of North China, while the grain filling rate of Wanmai 52 is the highest in Huanghuai winter wheat area. The grain filling of semi-winter wheat usually lasts 35-39 days. The climate difference between north and south is one of the reasons for the different filling rates of winter wheat. The variation trends of the filling rate of semi-winter wheat in each sowing period are the same, and the change of filling rate is consistent with the change law of related significant meteorological factors. The peak period of grain filling generally appears 15-25 days later than flowering, and the appearance time is earlier of the maximum fil-ling rate of late-sowed winter wheat than the control treatment, which is not conducive to increasing the grain weight. The temperature conditions have significant effects on the grain filling rate of winter wheat, of which the highest temperature factor is the common key factor affecting the filling rate of different sowing dates and varieties. Path analysis showed that the effect of maximum temperature on filling rate is determined by its direct effect, while the effect of sunshine hours and minimum temperature on filling rate is consistent with indirect effect. The average of highest temperature has the most important effect on fil-ling rate, while the sunshine time and averaged minimum temperature influence the filling rate weakly. The averages of highest and lowest temperature and the sunshine hours are the limiting factors of the filling rate, of which the average of highest temperature has the greatest decision-making effect on the change of filling rate.
2019, 45(12):1747-1755.
DOI: 10.7519/j.issn.1000-0526.2019.12.012
Abstract:
By using the hourly extreme wind from the conventional meteorological observation and the 6 h extreme wind forecast data from ECMWF between February 2015 and February 2018, the representative stations in the Bohai Sea were selected to analyze the prediction error characteristics of the extreme wind products in the ensemble forecast. The analysis showed that the spread of the extreme wind product in ensemble forecasting is obviously smaller than the root mean square error, and whether the forecasting results of each forecasting member are concentrated or not cannot reflect the reliability of forecasting. Due to the limitation of model prediction ability, it is impossible to select the most credible prediction results simply by ensemble prediction. The ensemble average, the 75th percentile and maximum ensemble forecasting have their own advantages and disadvantages in extreme wind forecasting. Therefore, based on the above three statistics and the frequency of different magnitude wind speed occurrence, an objective correction method for extreme wind forecasting in the Bohai Sea is established. The comparative analysis of experiments shows that the correction method can effectively improve the accuracy of extreme wind forecasting, which can provide important references for the forecast of extreme wind process.
By using the hourly extreme wind from the conventional meteorological observation and the 6 h extreme wind forecast data from ECMWF between February 2015 and February 2018, the representative stations in the Bohai Sea were selected to analyze the prediction error characteristics of the extreme wind products in the ensemble forecast. The analysis showed that the spread of the extreme wind product in ensemble forecasting is obviously smaller than the root mean square error, and whether the forecasting results of each forecasting member are concentrated or not cannot reflect the reliability of forecasting. Due to the limitation of model prediction ability, it is impossible to select the most credible prediction results simply by ensemble prediction. The ensemble average, the 75th percentile and maximum ensemble forecasting have their own advantages and disadvantages in extreme wind forecasting. Therefore, based on the above three statistics and the frequency of different magnitude wind speed occurrence, an objective correction method for extreme wind forecasting in the Bohai Sea is established. The comparative analysis of experiments shows that the correction method can effectively improve the accuracy of extreme wind forecasting, which can provide important references for the forecast of extreme wind process.
2019, 45(12):1756-1761.
DOI: 10.7519/j.issn.1000-0526.2019.12.013
Abstract:
Based on the data of air sounding winds from 93 high-altitude meteorological stations (300 m, 600 m and 900 m above the radar) in China from 1981 to 2014, the spatio-temporal variations of wind speed and its trends at different heights in the boundary layer were analyzed using GIS. The following conclusions were obtained. At the height of 300-900 m, the average wind speed over the years in Northeast and North China is larger, while the mean annual wind speed in Southwest and Northwest China is small relatively. The monthly variation trends of average wind speeds at different heights over the same area in the boundary layer are basically the same, but the seasonal wind speed variations in different regions are different. The annual range of monthly average wind speed in the same region increases with altitude. The annual average wind speed at 300 m altitude decreases significantly. At 600 m and 900 m heights, the average annual wind speeds in North China, Northwest China and Central China show an upward trend while the average annual wind speed in Northeast China shows a decreasing trend, but none of them have passed the significance level tests. The spatial distribution of average annual wind speed at all altitudes is relatively large in Northeast China, especially in the Greater Khingan Mountains and the Northeast Plain. The wind speed from east to west gradually decreases from the coast to the inland. At 300 m height, the annual average wind speed across China shows mainly a decreasing trend. At 600 m height, annual average wind speed in most parts of China shows an increasing trend, especially in Central China, Northwest China and the eastern coastal areas. At 900 m height, the change in annual average wind speed nationwide shows an encircling trend from the boundary to the interior, with the central area showing an increasing trend and the border areas a downward trend. However, not many areas have passed the significance level tests.
Based on the data of air sounding winds from 93 high-altitude meteorological stations (300 m, 600 m and 900 m above the radar) in China from 1981 to 2014, the spatio-temporal variations of wind speed and its trends at different heights in the boundary layer were analyzed using GIS. The following conclusions were obtained. At the height of 300-900 m, the average wind speed over the years in Northeast and North China is larger, while the mean annual wind speed in Southwest and Northwest China is small relatively. The monthly variation trends of average wind speeds at different heights over the same area in the boundary layer are basically the same, but the seasonal wind speed variations in different regions are different. The annual range of monthly average wind speed in the same region increases with altitude. The annual average wind speed at 300 m altitude decreases significantly. At 600 m and 900 m heights, the average annual wind speeds in North China, Northwest China and Central China show an upward trend while the average annual wind speed in Northeast China shows a decreasing trend, but none of them have passed the significance level tests. The spatial distribution of average annual wind speed at all altitudes is relatively large in Northeast China, especially in the Greater Khingan Mountains and the Northeast Plain. The wind speed from east to west gradually decreases from the coast to the inland. At 300 m height, the annual average wind speed across China shows mainly a decreasing trend. At 600 m height, annual average wind speed in most parts of China shows an increasing trend, especially in Central China, Northwest China and the eastern coastal areas. At 900 m height, the change in annual average wind speed nationwide shows an encircling trend from the boundary to the interior, with the central area showing an increasing trend and the border areas a downward trend. However, not many areas have passed the significance level tests.
2019, 45(12):1762-1768.
DOI: 10.7519/j.issn.1000-0526.2019.12.014
Abstract:
The main characteristics of the general atmospheric circulation in September 2019 are as follows. The polar vortex of Northern Hemisphere presented a single-pole pattern. In the mid-high latitudes of Asia, the circulation presented a two-trough pattern. The Northwest Pacific subtropical high was more westward and stronger than normal. The monthly mean precipitation amount is 62.4 mm, which is less than its normal value (65.3 m) by 4%. The monthly mean temperature is 17.7℃, 1.1℃ higher than its climatological mean (16.6℃). Four regional torrential rainfall processes occurred in China during September, and two of them were caused by tropical cyclones. In September, six tropical cyclones were generated over the Northwest Pacific and the South China Sea, no one landing China. Moreover, the autumn rain of West China started earlier than normal in the southern area and had a significant impact. Meteorological drought developed continuously over the lower-middle reaches of the Yangtze River. High air temperatures appeared over South to Yangtze River, South China and parts of North China. Heilongjiang, Inner Mongolia and many other regions were attacked by hail, and some areas of the two provinces suffered from low temperature and freezing disasters.
The main characteristics of the general atmospheric circulation in September 2019 are as follows. The polar vortex of Northern Hemisphere presented a single-pole pattern. In the mid-high latitudes of Asia, the circulation presented a two-trough pattern. The Northwest Pacific subtropical high was more westward and stronger than normal. The monthly mean precipitation amount is 62.4 mm, which is less than its normal value (65.3 m) by 4%. The monthly mean temperature is 17.7℃, 1.1℃ higher than its climatological mean (16.6℃). Four regional torrential rainfall processes occurred in China during September, and two of them were caused by tropical cyclones. In September, six tropical cyclones were generated over the Northwest Pacific and the South China Sea, no one landing China. Moreover, the autumn rain of West China started earlier than normal in the southern area and had a significant impact. Meteorological drought developed continuously over the lower-middle reaches of the Yangtze River. High air temperatures appeared over South to Yangtze River, South China and parts of North China. Heilongjiang, Inner Mongolia and many other regions were attacked by hail, and some areas of the two provinces suffered from low temperature and freezing disasters.
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ISSN:1000-0526 CN:11-2282/P