ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 43,Issue 12,2017 Table of Contents
2017, 43(12):1453-1460.
DOI: 10.7519/j.issn.1000-0526.2017.12.001
Abstract:
To investigate the impact of increased greenhouse gas (GHG) concentration and land use and land cover change (LULCC) on diurnal temperature range (DTR), several numerical experiments were performed using the fully coupled Community Earth System Model (CESM). The results of the model simulation show that the increased GHG concentration has led to significant decrease in DTR over mid- and high- latitudes of the Northern Hemisphere. However, GHG- induced changes in DTR have the significant differences in different seasons. During the warm and cold seasons, there is an opposite change character in the North America and the Siberia Region. The reduction of annual DTR induced by the increased GHG-over mid-high-latitudes is mainly contributed by the cold season. LULCC caused a weakening of the DTR in Eastern Asia, Southern Asia, Europe, and Eastern North America. We visualize the LULCC- and GHG-induced changes to the DTR in both magnitude and sign by the aid of coordinate axis. GHG plays a more important role in changing DTR in Southern Asia and Europe and in highlatitudes of the Northern Hemisphere. In contrast, LULCC plays a dominant role in determining changes in DTR in the midlatitudes of the Northern Hemisphere and Southern Asia, whether in the magnitude or value of the changes in DTR.
To investigate the impact of increased greenhouse gas (GHG) concentration and land use and land cover change (LULCC) on diurnal temperature range (DTR), several numerical experiments were performed using the fully coupled Community Earth System Model (CESM). The results of the model simulation show that the increased GHG concentration has led to significant decrease in DTR over mid- and high- latitudes of the Northern Hemisphere. However, GHG- induced changes in DTR have the significant differences in different seasons. During the warm and cold seasons, there is an opposite change character in the North America and the Siberia Region. The reduction of annual DTR induced by the increased GHG-over mid-high-latitudes is mainly contributed by the cold season. LULCC caused a weakening of the DTR in Eastern Asia, Southern Asia, Europe, and Eastern North America. We visualize the LULCC- and GHG-induced changes to the DTR in both magnitude and sign by the aid of coordinate axis. GHG plays a more important role in changing DTR in Southern Asia and Europe and in highlatitudes of the Northern Hemisphere. In contrast, LULCC plays a dominant role in determining changes in DTR in the midlatitudes of the Northern Hemisphere and Southern Asia, whether in the magnitude or value of the changes in DTR.
2017, 43(12):1461-1472.
DOI: 10.7519/j.issn.1000-0526.2017.12.002
Abstract:
Using Global Ensemble Forecast System (GEFS) data, a regional ensemble forecast system based on WRF model is constructed. Two initialization schemes are tested to form the initial states of regional ensemble (namely DRUC ensemble). One is the direct dynamical downscaling of GEFS initial states (namely DOWN ensemble), and the other is the overlaying the downscaled initial perturbations of GEFS onto the analysis of high resolution regional numerical weather prediction (NWP) system, named Beijing Rapid Update Cycle (BJRUC) system. Using the two methods, a series of ensemble forecast tests are conducted, and the results show that the smallscale components of DRUC perturbations grow more rapidly than those of DOWN perturbations. For shortterm forecast, the DOWN perturbations tend to underestimate the forecast error while the DRUC perturbation tends to identify where the forecast error is large and where the forecast error is small. Ensemble forecast verification shows that the DRUC ensemble has larger spread and smaller root mean square error than DOWN ensemble at short forecast lead time, and the probabilistic scores of DRUC are also better for shortterm forecast. Typical precipitation case study shows that DRUC ensemble can provide better probabilistic precipitation forecast than DOWN ensemble.
Using Global Ensemble Forecast System (GEFS) data, a regional ensemble forecast system based on WRF model is constructed. Two initialization schemes are tested to form the initial states of regional ensemble (namely DRUC ensemble). One is the direct dynamical downscaling of GEFS initial states (namely DOWN ensemble), and the other is the overlaying the downscaled initial perturbations of GEFS onto the analysis of high resolution regional numerical weather prediction (NWP) system, named Beijing Rapid Update Cycle (BJRUC) system. Using the two methods, a series of ensemble forecast tests are conducted, and the results show that the smallscale components of DRUC perturbations grow more rapidly than those of DOWN perturbations. For shortterm forecast, the DOWN perturbations tend to underestimate the forecast error while the DRUC perturbation tends to identify where the forecast error is large and where the forecast error is small. Ensemble forecast verification shows that the DRUC ensemble has larger spread and smaller root mean square error than DOWN ensemble at short forecast lead time, and the probabilistic scores of DRUC are also better for shortterm forecast. Typical precipitation case study shows that DRUC ensemble can provide better probabilistic precipitation forecast than DOWN ensemble.
2017, 43(12):1473-1486.
DOI: 10.7519/j.issn.1000-0526.2017.12.003
Abstract:
The refinement research of the vertical structure of freezing rain and snow is very lacking. To carry out this kind of research, in this paper we extract reflectivity factor and velocity spectrum width as well as the skewness which can reflect phase state of precipitation particles originally from spectrum data observed by vertical point of Kaband millimeterwave radar. After obtaining the falling velocity of precipitation particles through rising air speed, and the mean particles radius in the vertical direction, we analyze the changes in the liquid water content and ice water content in the vertical structure as well as the changes of the particles combined with sounding data and several parameters in the falling process. The results show that echo characteristic of freezing rain is uneven lamellar structure, while the snow’s filar detailed structure is obvious.The initial mean radius of precipitation particles of freezing rain and snow fall distri butes separately near 40 and 120 mm. From the initial precipitation particles to quickly coagulating and forming big particles, freezing raindrops need to go through about 0.2 km in the process. The cloud top is 0.1 km higher than the top of liquid water content and ice water content. The water content within the higher range is small, and the parameters reflecting the change of particles in vertical structure are consistent.
The refinement research of the vertical structure of freezing rain and snow is very lacking. To carry out this kind of research, in this paper we extract reflectivity factor and velocity spectrum width as well as the skewness which can reflect phase state of precipitation particles originally from spectrum data observed by vertical point of Kaband millimeterwave radar. After obtaining the falling velocity of precipitation particles through rising air speed, and the mean particles radius in the vertical direction, we analyze the changes in the liquid water content and ice water content in the vertical structure as well as the changes of the particles combined with sounding data and several parameters in the falling process. The results show that echo characteristic of freezing rain is uneven lamellar structure, while the snow’s filar detailed structure is obvious.The initial mean radius of precipitation particles of freezing rain and snow fall distri butes separately near 40 and 120 mm. From the initial precipitation particles to quickly coagulating and forming big particles, freezing raindrops need to go through about 0.2 km in the process. The cloud top is 0.1 km higher than the top of liquid water content and ice water content. The water content within the higher range is small, and the parameters reflecting the change of particles in vertical structure are consistent.
4 Characteristic Analysis and Trigger Mechanism of Convective Cluster over Sichuan Basin on 6 May 2016
2017, 43(12):1487-1495.
DOI: 10.7519/j.issn.1000-0526.2017.12.004
Abstract:
In this study, the characteristic and formation mechanism of convective cluster over Sichuan Basin on 6 May 2016 are analyzed with FY2 satellite data, NCEP reanalysis data and conventional data. The results indicate that the convective clusters tend to form at the buffer zone of the western Sichuan Plateau, with their cloud top brightness temperature less than -45℃ and maximum temperature gradient greater than 15℃. Meanwhile, the difference between the cloud top brightness temperature measurements from IR3 and IR1 can range from -5℃ to 0℃ and the difference of those from IR2IR1 is between 0℃ and 2℃. Heavy rain occurs in a few hours after the cloud top temperature quickly drops to the lowest temperature, the difference between the cloud top temperature measurements from IR3 and IR1 is near 0℃, and the difference of IR2IR1 is positive and the temperature gradient of 0℃. Furthermore, the heavy rain starts at the time when the brightness temperature starts to rise again. Typically, wide range of heavy rain is mainly produced by the severe convective clusters whose cloud top brightness temperature is less than -70℃ and it tends to happen within the lower and smooth regions with the cloud top temperature between -65℃ and -60℃ and the IR3 brightness temperature from -65℃ to -60℃. Moreover, it is not in conformity with the lowest temperature center of cloud top. Mechanism analysis shows that the clusters’ ambient characteristics include high instable convective energy, sufficient moisture and east wind flow. The cold airflow in boundary layer and convergence line on surface are the main mechanism of the convective cluster trigger. The enhancement of the vertical wind shear, and the development of the middle level warm airflow and the high level cold airflow jointly prompt the intensification of the severe convective clusters.
In this study, the characteristic and formation mechanism of convective cluster over Sichuan Basin on 6 May 2016 are analyzed with FY2 satellite data, NCEP reanalysis data and conventional data. The results indicate that the convective clusters tend to form at the buffer zone of the western Sichuan Plateau, with their cloud top brightness temperature less than -45℃ and maximum temperature gradient greater than 15℃. Meanwhile, the difference between the cloud top brightness temperature measurements from IR3 and IR1 can range from -5℃ to 0℃ and the difference of those from IR2IR1 is between 0℃ and 2℃. Heavy rain occurs in a few hours after the cloud top temperature quickly drops to the lowest temperature, the difference between the cloud top temperature measurements from IR3 and IR1 is near 0℃, and the difference of IR2IR1 is positive and the temperature gradient of 0℃. Furthermore, the heavy rain starts at the time when the brightness temperature starts to rise again. Typically, wide range of heavy rain is mainly produced by the severe convective clusters whose cloud top brightness temperature is less than -70℃ and it tends to happen within the lower and smooth regions with the cloud top temperature between -65℃ and -60℃ and the IR3 brightness temperature from -65℃ to -60℃. Moreover, it is not in conformity with the lowest temperature center of cloud top. Mechanism analysis shows that the clusters’ ambient characteristics include high instable convective energy, sufficient moisture and east wind flow. The cold airflow in boundary layer and convergence line on surface are the main mechanism of the convective cluster trigger. The enhancement of the vertical wind shear, and the development of the middle level warm airflow and the high level cold airflow jointly prompt the intensification of the severe convective clusters.
2017, 43(12):1496-1506.
DOI: 10.7519/j.issn.1000-0526.2017.12.005
Abstract:
In this study, a new concept of multitimescale heavy rainfall reinforcement (HRR) and extreme heavy rainfall reinforcement (EHRR) associated with tropical cyclones (TCs) based on Euler coordinate method are defined to study coastal areas. The 1 h, 3 h, 6 h, 12 h, and 24 h accumulated rainfall increment data of 135 TCs which influenced Zhejiang Province from 1973 to 2015 are extracted from hourly precipitation data of 67 national stations in Zhejiang Province, and the TC center location and intensity information of the abovementioned precipitation samples are also extracted from the China Meteorological Administration tropical cyclone best track datasets. Statistical results show that the thresholds of EHRR are 29.1, 51.9, 88.3, 103.9 and 123.9 mm over 1 h, 3 h, 6 h, 12 h, and 24 h, respectively. The frequencies of HRR under different temporal resolutions have similar seasonal variation, interannual variation and longterm linear trend, but the diurnal variation is different. The HRR and EHRR occur mainly in the eastern coastal area of Zhejiang in which the southern part of Wenzhou and the southern part of Taizhou are the highest frequency areas. HRR is likely to occur with 9 kinds of typhoon tracks which influenced Zhejiang. Except for the tracks by which TCs landed north of Zhoushan, EHRR could happen with the other tracks. The kind of track by which TC landed between Jiaojiang and Fuqing occupies the most percent of frequency of HRR and EHRR. Most of the TC centers concentrate in the border of Wenzhou and Taizhou in Zhejiang and northeast coast of Fujian when HRR and EHRR happened. The high frequency of HRR and EHRR at different timescales has different distance away from the TC center, but the maximum value of TC HRR appears in the range of typhoon center 600-700 km. The highest frequency of HRR and EHRR occurs in the northeast quadrant under different temporal resolutions, followed by the northwest quadrant, and the most significant reinforcements occur in the northeast quadrant. In addition, HRR and EHRR are related to the intensity of TC. On average, the most likely occurrence of RRTC is the strong tropical storm level, and ERRTC is the tropical depression level.
In this study, a new concept of multitimescale heavy rainfall reinforcement (HRR) and extreme heavy rainfall reinforcement (EHRR) associated with tropical cyclones (TCs) based on Euler coordinate method are defined to study coastal areas. The 1 h, 3 h, 6 h, 12 h, and 24 h accumulated rainfall increment data of 135 TCs which influenced Zhejiang Province from 1973 to 2015 are extracted from hourly precipitation data of 67 national stations in Zhejiang Province, and the TC center location and intensity information of the abovementioned precipitation samples are also extracted from the China Meteorological Administration tropical cyclone best track datasets. Statistical results show that the thresholds of EHRR are 29.1, 51.9, 88.3, 103.9 and 123.9 mm over 1 h, 3 h, 6 h, 12 h, and 24 h, respectively. The frequencies of HRR under different temporal resolutions have similar seasonal variation, interannual variation and longterm linear trend, but the diurnal variation is different. The HRR and EHRR occur mainly in the eastern coastal area of Zhejiang in which the southern part of Wenzhou and the southern part of Taizhou are the highest frequency areas. HRR is likely to occur with 9 kinds of typhoon tracks which influenced Zhejiang. Except for the tracks by which TCs landed north of Zhoushan, EHRR could happen with the other tracks. The kind of track by which TC landed between Jiaojiang and Fuqing occupies the most percent of frequency of HRR and EHRR. Most of the TC centers concentrate in the border of Wenzhou and Taizhou in Zhejiang and northeast coast of Fujian when HRR and EHRR happened. The high frequency of HRR and EHRR at different timescales has different distance away from the TC center, but the maximum value of TC HRR appears in the range of typhoon center 600-700 km. The highest frequency of HRR and EHRR occurs in the northeast quadrant under different temporal resolutions, followed by the northwest quadrant, and the most significant reinforcements occur in the northeast quadrant. In addition, HRR and EHRR are related to the intensity of TC. On average, the most likely occurrence of RRTC is the strong tropical storm level, and ERRTC is the tropical depression level.
2017, 43(12):1507-1516.
DOI: 10.7519/j.issn.1000-0526.2017.12.006
Abstract:
On 17 June and 15 July 2014, two continuous local shorttime severe rainstorms occurred in Chengde as a result of cold vortex. The hourly rainfalls were 39.6 and 66.1 mm·h-1 respectively and the maximum 10 min rainfalls were 15 and 18 mm correspondingly. Based on conventional observation data, 5-10 min automatic weather station data, Doppler radar data, satellite images and NCEP reanalysis data, the mesoscale characteristics of the two shorttime severe rainstorms are analyzed in this paper. The minute precipitation observation reveals that in the 17 June rainstorm process, 10 min rainfall showed a double peak type distribution as time going on, lasting about half an hour. In the 15 July rainstorm process, it showed a single peak type, which lasted less than 1 h. Both of the two local heavy rains were generated with the upper cold vortex circulation, and their triggering system is the ground mesoscale convergence center (convergence line). The precipitation peak was associated with southeast wind or the increased wind speed. The 6 m·s-1 southeast winds were favorable for the heavy rains. Satellite data show that the direct influence system of the rainstorm on 17 June 2014 was the mesoβ scale convective system. The heavy precipitation was corresponding to the low area of TBB. The severe convective system on 15 July 2014 performed as the mesoγ scale, corresponding to the large gradient area of TBB. The rainstorm on 17 June 2014 corresponded to the merge enhancement of convective cell echoes, which had a horizontal scale of near 20 km, lasting about half an hour with the echo intensity of 65 dBz. The rainstorm on 15 July 2014 was shown that a number of convective cell echoes passed through the urban area of Chengde in order, due to the “train effect”, and the convective cell echoes had a number of horizontal scales of less than 5 km, living less than 1 h with echo intensity 55 dBz. In two precipitation processes, the occurrence time of inverse wind area was corresponding to that of the shorttime strong rainfall, the duration of inverse wind area was longer, and the rainfall intensity is also stronger.
On 17 June and 15 July 2014, two continuous local shorttime severe rainstorms occurred in Chengde as a result of cold vortex. The hourly rainfalls were 39.6 and 66.1 mm·h-1 respectively and the maximum 10 min rainfalls were 15 and 18 mm correspondingly. Based on conventional observation data, 5-10 min automatic weather station data, Doppler radar data, satellite images and NCEP reanalysis data, the mesoscale characteristics of the two shorttime severe rainstorms are analyzed in this paper. The minute precipitation observation reveals that in the 17 June rainstorm process, 10 min rainfall showed a double peak type distribution as time going on, lasting about half an hour. In the 15 July rainstorm process, it showed a single peak type, which lasted less than 1 h. Both of the two local heavy rains were generated with the upper cold vortex circulation, and their triggering system is the ground mesoscale convergence center (convergence line). The precipitation peak was associated with southeast wind or the increased wind speed. The 6 m·s-1 southeast winds were favorable for the heavy rains. Satellite data show that the direct influence system of the rainstorm on 17 June 2014 was the mesoβ scale convective system. The heavy precipitation was corresponding to the low area of TBB. The severe convective system on 15 July 2014 performed as the mesoγ scale, corresponding to the large gradient area of TBB. The rainstorm on 17 June 2014 corresponded to the merge enhancement of convective cell echoes, which had a horizontal scale of near 20 km, lasting about half an hour with the echo intensity of 65 dBz. The rainstorm on 15 July 2014 was shown that a number of convective cell echoes passed through the urban area of Chengde in order, due to the “train effect”, and the convective cell echoes had a number of horizontal scales of less than 5 km, living less than 1 h with echo intensity 55 dBz. In two precipitation processes, the occurrence time of inverse wind area was corresponding to that of the shorttime strong rainfall, the duration of inverse wind area was longer, and the rainfall intensity is also stronger.
2017, 43(12):1517-1526.
DOI: 10.7519/j.issn.1000-0526.2017.12.007
Abstract:
The regional rainstorm of Sichuan Basin is classified using the data from meteorological stations in Sichuan Basin, NCEP/NCAR reanalysis data, NOAA SST data, snow days of Tibet Plateau, and the method of MTMSVD (multitaper methodsingular value decomposition). Not only the characteristics of spatiotemporal variation but also the previous signal is discussed. The results show that the regional rainstorm of Sichuan Basin can be divided into three types, which are the west basin, northeast basin and south basin respectively. The most significant interannual variation is the quasi3year cycle which reflects the abnormal circulation process of west basin type with the weakadjustmentstrong pattern. The quasi16year cycle is the obvious interdecadal signal which embodies the exception evolution of the northeast basin and south basin. Through the analysis of cooperative change, it is found that the ENSO event and snow cover days in the previous winter are the strong precursor signal in the quasi3year cycle. In the quasi16year oscillation process, the PDO (Pacific decadal oscillation) acts as a previous signal of the northeast basin type and south basin type.
The regional rainstorm of Sichuan Basin is classified using the data from meteorological stations in Sichuan Basin, NCEP/NCAR reanalysis data, NOAA SST data, snow days of Tibet Plateau, and the method of MTMSVD (multitaper methodsingular value decomposition). Not only the characteristics of spatiotemporal variation but also the previous signal is discussed. The results show that the regional rainstorm of Sichuan Basin can be divided into three types, which are the west basin, northeast basin and south basin respectively. The most significant interannual variation is the quasi3year cycle which reflects the abnormal circulation process of west basin type with the weakadjustmentstrong pattern. The quasi16year cycle is the obvious interdecadal signal which embodies the exception evolution of the northeast basin and south basin. Through the analysis of cooperative change, it is found that the ENSO event and snow cover days in the previous winter are the strong precursor signal in the quasi3year cycle. In the quasi16year oscillation process, the PDO (Pacific decadal oscillation) acts as a previous signal of the northeast basin type and south basin type.
2017, 43(12):1527-1533.
DOI: 10.7519/j.issn.1000-0526.2017.12.008
Abstract:
To explicitly investigate the influence of precipitation on visibility and PM2.5 concentration, minutescale observations of Hangzhou during 2014-2015 are used to comparatively analyze the distribution characteristics of visibility and PM2.5 concentration under different levels of precipitation, and, furthermore, the quantitative impacts of precipitation with different intensities on visibility and PM2.5 concentration are studied. The results indicate that the intensity and duration of precipitation can significantly modulate visibility and PM2.5 concentration. Consistent and stable rainfall are easy to trigger long lowvisibility scenario, and the sudden heavy precipitation is an important factor inducing the sharpdecrease of visibility. With the rise of rainfall, the visibility changes from rapiddecline to slowdecline and there exists an inflection point. The removing effect of precipitation on PM2.5 concentration can be mediated by the intensity of rainfall and the PM2.5 concentration before raining. When there is modest/small rainfall, the removing effect usually occurs several time later. However, heavy precipitation is able to remove PM2.5 quickly. Basically, synchronous changes among precipitation, PM2.5 concentration and visibility can appear. Based on the two factors of precipitation intensity and PM2.5 concentration before raining, a quantitative statistical model reflecting the influence of rainfall on PM2.5 concentration is constructed with the nonlinear fitting technology, and the modeling results agree well with observations. Finally, the existing limitations and some scientific issues which need further exploring in the future are discussed.
To explicitly investigate the influence of precipitation on visibility and PM2.5 concentration, minutescale observations of Hangzhou during 2014-2015 are used to comparatively analyze the distribution characteristics of visibility and PM2.5 concentration under different levels of precipitation, and, furthermore, the quantitative impacts of precipitation with different intensities on visibility and PM2.5 concentration are studied. The results indicate that the intensity and duration of precipitation can significantly modulate visibility and PM2.5 concentration. Consistent and stable rainfall are easy to trigger long lowvisibility scenario, and the sudden heavy precipitation is an important factor inducing the sharpdecrease of visibility. With the rise of rainfall, the visibility changes from rapiddecline to slowdecline and there exists an inflection point. The removing effect of precipitation on PM2.5 concentration can be mediated by the intensity of rainfall and the PM2.5 concentration before raining. When there is modest/small rainfall, the removing effect usually occurs several time later. However, heavy precipitation is able to remove PM2.5 quickly. Basically, synchronous changes among precipitation, PM2.5 concentration and visibility can appear. Based on the two factors of precipitation intensity and PM2.5 concentration before raining, a quantitative statistical model reflecting the influence of rainfall on PM2.5 concentration is constructed with the nonlinear fitting technology, and the modeling results agree well with observations. Finally, the existing limitations and some scientific issues which need further exploring in the future are discussed.
9 Quality Assessment of China Merged Precipitation Product Using Hydrological Data in Jiangxi Province
2017, 43(12):1534-1546.
DOI: 10.7519/j.issn.1000-0526.2017.12.009
Abstract:
In this paper, the quality of 5 km and 10 km merged precipitation developed by China National Meteorological Information Centre is assessed based on the hydrological observed precipitation. Besides the U.S. National Oceanic and Atmospheric Administration (NOAA) climate prediction center satellite precipitation products (CMORPH) and the East Asian multisatellite integrated precipitation (EMSIP) developed by National Meteorological Information Centre are also assessed by comparing the two merged precipitation products. The data error of each precipitation product and its spatiotemporal variation characteristic are analyzed to verify the applicability of merged precipitation product in this selected region. The results show that the merged precipitation and satellite precipitation can well reflect the variation tendency of annual hourly precipitation. Four precipitation products all have a certain underestimate compared with the hydrological observed precipitation, and the underestimate of the satellite precipitation is larger. Merged precipitation has better quality, and the accuracy of the 5 km merged precipitation (R=0.81, RMSE=2.12 mm·h-1, RE=-5.4%) is better than the 10 km merged precipitation (R=0.78, RMSE=2.3 mm·h-1, RE=-5.1%). There is a great difference between the satellite precipitation and the hydrological observed precipitation. The correlation coefficient of CMORPH and EMSIP precipitation products is only 0.19 and 0.24, respectively. The error of each precipitation product has the same monthly variation tendency, and the error variation range of the merged precipitation product is obviously smaller than that of the satellite precipitation product. Besides, the quality variation of the four precipitation products in different rainfall level is also discussed, which shows that the correlation of the four precipitation products increases with the increase of precipitation. Merged precipitation products can accurately show the spatial structure and the central location of precipitation, 5 km merged precipitation takes great advantage in monitoring the severe precipitation events.
In this paper, the quality of 5 km and 10 km merged precipitation developed by China National Meteorological Information Centre is assessed based on the hydrological observed precipitation. Besides the U.S. National Oceanic and Atmospheric Administration (NOAA) climate prediction center satellite precipitation products (CMORPH) and the East Asian multisatellite integrated precipitation (EMSIP) developed by National Meteorological Information Centre are also assessed by comparing the two merged precipitation products. The data error of each precipitation product and its spatiotemporal variation characteristic are analyzed to verify the applicability of merged precipitation product in this selected region. The results show that the merged precipitation and satellite precipitation can well reflect the variation tendency of annual hourly precipitation. Four precipitation products all have a certain underestimate compared with the hydrological observed precipitation, and the underestimate of the satellite precipitation is larger. Merged precipitation has better quality, and the accuracy of the 5 km merged precipitation (R=0.81, RMSE=2.12 mm·h-1, RE=-5.4%) is better than the 10 km merged precipitation (R=0.78, RMSE=2.3 mm·h-1, RE=-5.1%). There is a great difference between the satellite precipitation and the hydrological observed precipitation. The correlation coefficient of CMORPH and EMSIP precipitation products is only 0.19 and 0.24, respectively. The error of each precipitation product has the same monthly variation tendency, and the error variation range of the merged precipitation product is obviously smaller than that of the satellite precipitation product. Besides, the quality variation of the four precipitation products in different rainfall level is also discussed, which shows that the correlation of the four precipitation products increases with the increase of precipitation. Merged precipitation products can accurately show the spatial structure and the central location of precipitation, 5 km merged precipitation takes great advantage in monitoring the severe precipitation events.
2017, 43(12):1547-1553.
DOI: 10.7519/j.issn.10000526.2017.12.010
Abstract:
With the software of GAMIT 10.6 and the GPS observation data at Nanchang Station, a set of 13 tests about the influence of approximate coordinate on the solving of GPS PWV are carried out. The results show that when the distance between the approximate coordinate and actual coordinate is less than 60 m, the approximate coordinate has weak effect on GPS PWV. But when the distance exceeds 60 m, the variation of approximate coordinate significantly affects the solving of GPS PWV. The relative error of baseline and the standard deviation between GPS PWV and sounding PWV increase rapidly, while the days of successful solving GPS PWV decrease rapidly with the increasing of the distance (when the distance ≥120 m, the day is 0). Meanwhile, NRMS (normalized root mean square) and the correlation between GPS PWV and sounding PWV also has a significant decrease when the distance is more than 60 m. Additionally, the effects of variation of approximate coordinate on the relative error of baseline, NRMS, and the accuracy of GPS PWV only occur at local station.
With the software of GAMIT 10.6 and the GPS observation data at Nanchang Station, a set of 13 tests about the influence of approximate coordinate on the solving of GPS PWV are carried out. The results show that when the distance between the approximate coordinate and actual coordinate is less than 60 m, the approximate coordinate has weak effect on GPS PWV. But when the distance exceeds 60 m, the variation of approximate coordinate significantly affects the solving of GPS PWV. The relative error of baseline and the standard deviation between GPS PWV and sounding PWV increase rapidly, while the days of successful solving GPS PWV decrease rapidly with the increasing of the distance (when the distance ≥120 m, the day is 0). Meanwhile, NRMS (normalized root mean square) and the correlation between GPS PWV and sounding PWV also has a significant decrease when the distance is more than 60 m. Additionally, the effects of variation of approximate coordinate on the relative error of baseline, NRMS, and the accuracy of GPS PWV only occur at local station.
2017, 43(12):1554-1561.
DOI: 10.7519/j.issn.1000-0526.2017.12.011
Abstract:
Urban development information and observed atmospheric temperature over the past 28 years are analyzed to study the relationship between urban cluster development indexes and urban heat island effect in the Pearl River Delta Region. The results reveal that urban cluster development indexes increase slowly before 2000, but soar five to nine times afterwards. Warming rate of the urban heat island intensity (UHII) is 0.34 ℃·(10 a)-1 before 2000, and doubles to 0.69 ℃·(10 a)-1 after 2000. The UHII increases year by year, and changes significantly during a year. It is weak in rainy seasons, but strong in dry seasons. In July when rainfall is abundant, the UHII is the weakest, whereas in December when the weather is dry, it is the strongest. Gray relational analysis indicates that, urban development indexes, including city builtup area, gross industrial output value, total annual electricity consumption and resident population significantly affect atmospheric temperature and the UHII. Urban development indexes are sorted according to their correlation coefficients with atmospheric temperature and the UHII in descending order. Then, indexes with greater correlation are selected to build a gray model, simulating atmospheric temperature and the UHII. This gray model performs well with the mean relative fitting error of urban cluster development indexes being 2.7% and 7% to air temperature and the UHII, respectively.
Urban development information and observed atmospheric temperature over the past 28 years are analyzed to study the relationship between urban cluster development indexes and urban heat island effect in the Pearl River Delta Region. The results reveal that urban cluster development indexes increase slowly before 2000, but soar five to nine times afterwards. Warming rate of the urban heat island intensity (UHII) is 0.34 ℃·(10 a)-1 before 2000, and doubles to 0.69 ℃·(10 a)-1 after 2000. The UHII increases year by year, and changes significantly during a year. It is weak in rainy seasons, but strong in dry seasons. In July when rainfall is abundant, the UHII is the weakest, whereas in December when the weather is dry, it is the strongest. Gray relational analysis indicates that, urban development indexes, including city builtup area, gross industrial output value, total annual electricity consumption and resident population significantly affect atmospheric temperature and the UHII. Urban development indexes are sorted according to their correlation coefficients with atmospheric temperature and the UHII in descending order. Then, indexes with greater correlation are selected to build a gray model, simulating atmospheric temperature and the UHII. This gray model performs well with the mean relative fitting error of urban cluster development indexes being 2.7% and 7% to air temperature and the UHII, respectively.
2017, 43(12):1562-1571.
DOI: 10.7519/j.issn.1000-0526.2017.12.012
Abstract:
This paper summarizes the international progress in weather modification technologies during 2013-2016, reviews the comprehensive evaluation of weather modification experiments, application of high performance remote sensing equipment, application of cloud and seeding models, research and development of weather modification equipment and other related researches. In addition, combining the status of weather modification technologies in China with recent international progress, the experiences and suggestions for promoting the related weather modification technologies are discussed from different aspects.
This paper summarizes the international progress in weather modification technologies during 2013-2016, reviews the comprehensive evaluation of weather modification experiments, application of high performance remote sensing equipment, application of cloud and seeding models, research and development of weather modification equipment and other related researches. In addition, combining the status of weather modification technologies in China with recent international progress, the experiences and suggestions for promoting the related weather modification technologies are discussed from different aspects.
2017, 43(12):1572-1577.
DOI: 10.7519/j.issn.1000-0526.2017.12.013
Abstract:
The data of international exchange stations are an important basis for studying engineering meteorological parameters in the area of only few observational data. However, this data are timed data which have some quality problems. Therefore, quality control of the data and the transform of timed data are necessary before further study. Being to lack of other references, the quality control of the data includes temporal consistency check, spatial consistency check and consistency check between various observed elements based on the weather and climate characteristics of Arctic. Return period wind speed is calculated with yearly maximum wind speed (usually 10 min average wind) which may not occur in timed data. However, there is no any good ways to obtain hourly data from timed data, return period wind speed is therefore obtained mainly through correcting the return period wind speed calculated from timed data. By applying wind speed standard deviation, the relationship between return period wind speed calculated from timed data and yearly data is established, with which return period wind speed in Arctic is obtained.
The data of international exchange stations are an important basis for studying engineering meteorological parameters in the area of only few observational data. However, this data are timed data which have some quality problems. Therefore, quality control of the data and the transform of timed data are necessary before further study. Being to lack of other references, the quality control of the data includes temporal consistency check, spatial consistency check and consistency check between various observed elements based on the weather and climate characteristics of Arctic. Return period wind speed is calculated with yearly maximum wind speed (usually 10 min average wind) which may not occur in timed data. However, there is no any good ways to obtain hourly data from timed data, return period wind speed is therefore obtained mainly through correcting the return period wind speed calculated from timed data. By applying wind speed standard deviation, the relationship between return period wind speed calculated from timed data and yearly data is established, with which return period wind speed in Arctic is obtained.
2017, 43(12):1578-1583.
DOI: 10.7519/j.issn.1000-0526.2017.12.014
Abstract:
Based on the daily observation data of seven stations in Dalian from 1971 to 2015, the cumulative frequency the diurnal and monthly distributions of low windspeed are analyzed. The trend of annual percentage of low windspeed are also studied. The results show that: (1) The frequency of low wind speed conditions in Dalian is about 20% in the recent 45 years, with the lowest (8%) at Changhai, and the highest (35%) at Pulandian. (2) The frequency of low wind speed has an increasing trend, and there are significant increasing trends at Dalian, Pulandian and Changhai, especially in the past ten years. (3) The frequency of low wind speed conditions has significant diurnal changes, which is high over the night and low during the daytime. (4) From March to July, the frequency of low windspeed is low and from September to February it is higher with the maximum value seen in Dalian in September. (5) Changhai is the station with the longest duration of low windspeed. The 27% low wind-speed condition can last at least 10 h and the 9% low windspeed conditions can last at least 20 h at Changhai Station. Dalian Station is the station with the shortest duration, more than 85% low windspeed condition in Dalian Station can last 4 h or less.
Based on the daily observation data of seven stations in Dalian from 1971 to 2015, the cumulative frequency the diurnal and monthly distributions of low windspeed are analyzed. The trend of annual percentage of low windspeed are also studied. The results show that: (1) The frequency of low wind speed conditions in Dalian is about 20% in the recent 45 years, with the lowest (8%) at Changhai, and the highest (35%) at Pulandian. (2) The frequency of low wind speed has an increasing trend, and there are significant increasing trends at Dalian, Pulandian and Changhai, especially in the past ten years. (3) The frequency of low wind speed conditions has significant diurnal changes, which is high over the night and low during the daytime. (4) From March to July, the frequency of low windspeed is low and from September to February it is higher with the maximum value seen in Dalian in September. (5) Changhai is the station with the longest duration of low windspeed. The 27% low wind-speed condition can last at least 10 h and the 9% low windspeed conditions can last at least 20 h at Changhai Station. Dalian Station is the station with the shortest duration, more than 85% low windspeed condition in Dalian Station can last 4 h or less.
2017, 43(12):1584-1593.
DOI: 10.7519/j.issn.1000-0526.2017.12.015
Abstract:
The grid element forecasting is the main business of China Meteorological Administration, and also the future development trend of weather forecasting operation. This article proposes the method of “station corrected value transfer to grid point” which uses traditional station temperature forecast issued by SCMOC of Central Meteorological Observatory and station temperature established by the regression method to correct the grid forecast data of ECMWF high resolution model 2 m temperature. The results show that (1) the accuracy rate of maximum and minimum temperature deviation less than 2℃ in 24-168 h of SCMOC was higher than that of ECMWF by 10.0% and 23.1% respectively. There was large systematic deviation in ECMWF temperature forecast, whose minimum temperature forecast was higher and maximum temperature forecast was lower. (2) The “station corrected value transfer to grid point” method could correct the systematic deviation of ECMWF temperature forecast, and at the same time, keep the spatial pattern of forecasted field and topography characterization described by the original model unchanged. (3) Using SCMOC temperature forecasts from 98 county stations in the study area to correct ECMWF grid forecast data and returned the results to 1289 village stations for testing, we found that the accuracy rate of 24 h minimum and maximum temperature deviation <1℃ increased by 22.8% and 11.9% compared to ECMWF, and the accuracy of deviation <2℃ increased by 29.7% and 17.4%. The absolute error of the minimum (maximum) temperature decreased 0.99℃ (0.69℃) and the mean error decreased 0.7℃ (-0.9℃). (4) Using the temperature forecast of the 98 county stations by the regression method to correct the grid field could correct the systematic deviation of ECMWF as well. Comparing the two methods, SCMOC difference transfer has a great advantage in minimum temperature correction, and the regression method is better in maximum temperature correction. In addition, the regression method could improve the hourly temperature forecast effect. This method has been successfully applied to Shaanxi fining grid forecasting system.
The grid element forecasting is the main business of China Meteorological Administration, and also the future development trend of weather forecasting operation. This article proposes the method of “station corrected value transfer to grid point” which uses traditional station temperature forecast issued by SCMOC of Central Meteorological Observatory and station temperature established by the regression method to correct the grid forecast data of ECMWF high resolution model 2 m temperature. The results show that (1) the accuracy rate of maximum and minimum temperature deviation less than 2℃ in 24-168 h of SCMOC was higher than that of ECMWF by 10.0% and 23.1% respectively. There was large systematic deviation in ECMWF temperature forecast, whose minimum temperature forecast was higher and maximum temperature forecast was lower. (2) The “station corrected value transfer to grid point” method could correct the systematic deviation of ECMWF temperature forecast, and at the same time, keep the spatial pattern of forecasted field and topography characterization described by the original model unchanged. (3) Using SCMOC temperature forecasts from 98 county stations in the study area to correct ECMWF grid forecast data and returned the results to 1289 village stations for testing, we found that the accuracy rate of 24 h minimum and maximum temperature deviation <1℃ increased by 22.8% and 11.9% compared to ECMWF, and the accuracy of deviation <2℃ increased by 29.7% and 17.4%. The absolute error of the minimum (maximum) temperature decreased 0.99℃ (0.69℃) and the mean error decreased 0.7℃ (-0.9℃). (4) Using the temperature forecast of the 98 county stations by the regression method to correct the grid field could correct the systematic deviation of ECMWF as well. Comparing the two methods, SCMOC difference transfer has a great advantage in minimum temperature correction, and the regression method is better in maximum temperature correction. In addition, the regression method could improve the hourly temperature forecast effect. This method has been successfully applied to Shaanxi fining grid forecasting system.
2017, 43(12):1594-1600.
DOI: 10.7519/j.issn.1000-0526.2017.12.016
Abstract:
The main characteristics of the general atmospheric circulation in September 2017 are as follows. There was one polar vortex center in the Northern Hemisphere, slightly stronger than usual. The circulation in Eurasian middlehigh latitudes showed a multiwave pattern. The subtropical high in northwest Pacific Ocean lay westward and southward, and its intensity was slightly stronger than its average state during the corresponding period of normal years. The monthly mean precipitation amount is 62.0 mm which is less than normal in 5%, while the monthly mean temperature is 17.8℃, 1.2℃ higher than normal, which ranks the highest since 1961. Ten regional torrential rainfall events happened in September. Four tropical cyclones were generated over northwest Pacific Ocean and the South China Sea, and typhoon Mawar (1716) made landfall along the coastal areas over Guangdong Province in September. Sichuan and Yunnan received autumn rain notably; strong wind and hail disasters hit 13 provinces; drought situation in middle and eastern parts of Mongolia got relieved.
The main characteristics of the general atmospheric circulation in September 2017 are as follows. There was one polar vortex center in the Northern Hemisphere, slightly stronger than usual. The circulation in Eurasian middlehigh latitudes showed a multiwave pattern. The subtropical high in northwest Pacific Ocean lay westward and southward, and its intensity was slightly stronger than its average state during the corresponding period of normal years. The monthly mean precipitation amount is 62.0 mm which is less than normal in 5%, while the monthly mean temperature is 17.8℃, 1.2℃ higher than normal, which ranks the highest since 1961. Ten regional torrential rainfall events happened in September. Four tropical cyclones were generated over northwest Pacific Ocean and the South China Sea, and typhoon Mawar (1716) made landfall along the coastal areas over Guangdong Province in September. Sichuan and Yunnan received autumn rain notably; strong wind and hail disasters hit 13 provinces; drought situation in middle and eastern parts of Mongolia got relieved.
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ISSN:1000-0526 CN:11-2282/P