A second rain belt sometimes occurs ahead of a frontal rain belt in the warm sector over coastal South China,leading to heavy precipitation.We examined the differences in the mesoscale characteristics and microphysics...A second rain belt sometimes occurs ahead of a frontal rain belt in the warm sector over coastal South China,leading to heavy precipitation.We examined the differences in the mesoscale characteristics and microphysics of the frontal and warm sector rain belts that occurred in South China on May 10–13,2022.The southern rain belt occurred in an environment with favorable mesoscale conditions but weak large-scale forcing.In contrast,the northern rain belt was related to low-level horizontal shear and the surface-level front.The interaction between the enhanced southeasterly winds and the rainfall-induced cold pool promoted the persistent growth of convection along the southern rain belt.The convective cell propagated east over the coastal area,where there was a large temperature gradient.The bow-shaped echo in this region may be closely related to the rear-inflow jet.By contrast,the initial convection of the northern rain belt was triggered along the front and the region of low-level horizontal shear,with mesoscale interactions between the enhanced warm-moist southeasterly airflow and the cold dome associated with the earlier rain.The terrain blocked the movement of the cold pool,resulting in the stagnation of the frontal convective cell at an early stage.Subsequently,a meso-γ-scale vortex formed during the rapid movement of the convective cell,corresponding to an enhancement of precipitation.The representative raindrop spectra for the southern rain belt were characterized by a greater number and higher density of raindrops than the northern rain belt,even though both resulted in comparable hourly rainfalls.These results help us better understand the characteristics of double rain belts over South China.展开更多
Based on the analysis of the Asian lower-level jet stream, this paper indicates that having shifted to the Bay of Bengal, this large-scale lower-level jet(LLJ) develops into two branches: the northern branch (NB) whic...Based on the analysis of the Asian lower-level jet stream, this paper indicates that having shifted to the Bay of Bengal, this large-scale lower-level jet(LLJ) develops into two branches: the northern branch (NB) which is a strong southwest flow moving into the inland of China along the southeast side of the Qinghai-Xizang Plateau and then moving eastward to Japan along the north side of the subtropical high, and the southern branch (SB) which continues to be a west flow and travels into the West Pacific across the Indo-China Peninsula along the south side of the monsoon trough. Above the two branches are two synoptic-scale transient tubular monsoon circulation systems, the northern branch being a subtropical monsoon stream tube (SMST) and the southern branch a tropical monsoon stream tube (TMST). Their ascending branches, corresponding to a subtropical monsoon rain belt and a tropical monsoon rain belt respectively, bear considerable influence on the weather over China.展开更多
In order to investigate the effect of the factors in tower latitudes on Meiyu/Baiu front,a diagnostic analysis for the two cases during June to July of 1985 and 1986 was examined.We found that (1)when the tropical con...In order to investigate the effect of the factors in tower latitudes on Meiyu/Baiu front,a diagnostic analysis for the two cases during June to July of 1985 and 1986 was examined.We found that (1)when the tropical convective activity moves westward to 10.5-15.5′N/140°E from east side of 10.5-15.5°N/160°E,the northward shifts of the Meiyu/Baiu rain belt occurs;(2)the main factor which results in the northward and southward shifts of Meiyu/Baiu rain belt is thought as the 8,18 and 30 day oscillations of the tropical convective activity around West Pacific. Meanwhile,the wave train propagating from Lake Baikal via Okhotsk Sea to the tropics could sometimes shift Baiu rain belt southward;(3)the onsets of Meiyu in China of both cases tend to take place just when the convective activity around lower latitudes moves westward through about 140°E with the 8,18 and 30 day oscillation periods firstly coming to June.展开更多
Based on the analyses of the moisture transport structure in the whole layer of the troposphere along the Yangtze River valley during draught/flood years using the NCEP reanalysis data, this paper reveals that there e...Based on the analyses of the moisture transport structure in the whole layer of the troposphere along the Yangtze River valley during draught/flood years using the NCEP reanalysis data, this paper reveals that there exists a key region with a “Large Triangle” shape of transporting moisture for the Tibetan Plateau to Meiyu Belt and its“source/sink” structure; discloses that the interannual variation of the whole budget of inflow and outflow of moisture through the boundaries of a “Large Triangle” key region has the in-phase characteristic. Then a moisture transport structure over the skirt of the plateau and a conceptual model on the “transfer post” of moisture transport in the area of the South China Sea-Tibetan Plateau-Yangtze River valley in summer are put forward in this paper: the anti-phase feature of whole layer moisture transport flow patterns of Yangtze River valley during drought/flooding years is exhibited using the computational scheme of whole layer moisture transport correlation vector fields; a comprehensive dynamic model and its physical diagram of the teleconnection source/sink structure of the moisture transport of the Meiyu rain belt have been made. It shows that the moisture transfer effect over the skirt of the plateau from the ocean (Indian Ocean, South China Sea and west North Pacific) led to a moisture confluence belt in the Yangtze River valley and the teleconnection moisture transport source/sink structure over the “Large Triangle” shape area in flooding years.展开更多
采用国产水动力学模型(integrated flood model system,IFMS),对“23·7”海河流域永定河系特大洪水中永定河泛区洪水演进及淹没范围变化进行精细化模拟复盘。将模拟结果与卫星遥感监测获取的泛区淹没范围进行对比,最大淹没面积误...采用国产水动力学模型(integrated flood model system,IFMS),对“23·7”海河流域永定河系特大洪水中永定河泛区洪水演进及淹没范围变化进行精细化模拟复盘。将模拟结果与卫星遥感监测获取的泛区淹没范围进行对比,最大淹没面积误差仅为8.8%,验证了该模型在永定河泛区洪水模拟中的可靠度。构建的永定河泛区模型可以准确反映分洪口门启闭、蓄滞洪量变化及泛区进退洪淹没过程。基于该模型,进一步研究雨带北移对该地区未来防洪情势的影响。结果表明:同等重现期的设计洪水受雨带北移影响后,将导致泛区防洪情势愈加严峻,雨带北移影响下的20 a一遇设计洪水最大淹没范围与现状情景下50 a一遇设计洪水最大淹没范围持平。因此,为更好地应对未来防洪情势的发展,需要针对永定河泛区提出更加合理的防洪规划并科学制定工程与非工程相结合的防洪措施。展开更多
2022年汛期,国家气候中心准确预测了“全国气候年景总体偏差,区域性、阶段性旱涝灾害明显,降水空间差异显著,主要多雨区在我国北方”的总趋势,较好、较早把握了汛期主雨带位置和全国旱涝分布。对东亚夏季风和雨季季节进程“南海夏季风5...2022年汛期,国家气候中心准确预测了“全国气候年景总体偏差,区域性、阶段性旱涝灾害明显,降水空间差异显著,主要多雨区在我国北方”的总趋势,较好、较早把握了汛期主雨带位置和全国旱涝分布。对东亚夏季风和雨季季节进程“南海夏季风5月第3候爆发,长江中下游入梅偏早,梅雨量偏少,以及华北雨季开始偏早,雨量偏多”的预测与实况一致。对夏季台风生成个数较常年偏少,盛夏出现北上台风可能性大的预测与实况基本吻合。准确预测了全国平均气温趋势和高温异常特征。对“夏季我国中东部大部气温偏高,华东、华中、新疆等地高温日数较常年同期偏多,可能出现阶段性高温热浪”的预测与实况一致。主要不足之处是对长江中下游和川渝地区高温干旱的范围和极端程度估计不足。2022年汛期预测重点考虑连续La Ni a事件和印度洋偶极子负位相对东亚夏季风环流的影响,夏季西太平洋副热带高压强度偏强,脊线位置偏北,东亚夏季风偏强,初夏东北冷涡活跃,导致汛期主雨带位于东北、华北和西北地区东部等地。展开更多
基金National Natural Science Foundation of China(41930972,52239006,41975001)。
文摘A second rain belt sometimes occurs ahead of a frontal rain belt in the warm sector over coastal South China,leading to heavy precipitation.We examined the differences in the mesoscale characteristics and microphysics of the frontal and warm sector rain belts that occurred in South China on May 10–13,2022.The southern rain belt occurred in an environment with favorable mesoscale conditions but weak large-scale forcing.In contrast,the northern rain belt was related to low-level horizontal shear and the surface-level front.The interaction between the enhanced southeasterly winds and the rainfall-induced cold pool promoted the persistent growth of convection along the southern rain belt.The convective cell propagated east over the coastal area,where there was a large temperature gradient.The bow-shaped echo in this region may be closely related to the rear-inflow jet.By contrast,the initial convection of the northern rain belt was triggered along the front and the region of low-level horizontal shear,with mesoscale interactions between the enhanced warm-moist southeasterly airflow and the cold dome associated with the earlier rain.The terrain blocked the movement of the cold pool,resulting in the stagnation of the frontal convective cell at an early stage.Subsequently,a meso-γ-scale vortex formed during the rapid movement of the convective cell,corresponding to an enhancement of precipitation.The representative raindrop spectra for the southern rain belt were characterized by a greater number and higher density of raindrops than the northern rain belt,even though both resulted in comparable hourly rainfalls.These results help us better understand the characteristics of double rain belts over South China.
文摘Based on the analysis of the Asian lower-level jet stream, this paper indicates that having shifted to the Bay of Bengal, this large-scale lower-level jet(LLJ) develops into two branches: the northern branch (NB) which is a strong southwest flow moving into the inland of China along the southeast side of the Qinghai-Xizang Plateau and then moving eastward to Japan along the north side of the subtropical high, and the southern branch (SB) which continues to be a west flow and travels into the West Pacific across the Indo-China Peninsula along the south side of the monsoon trough. Above the two branches are two synoptic-scale transient tubular monsoon circulation systems, the northern branch being a subtropical monsoon stream tube (SMST) and the southern branch a tropical monsoon stream tube (TMST). Their ascending branches, corresponding to a subtropical monsoon rain belt and a tropical monsoon rain belt respectively, bear considerable influence on the weather over China.
基金This study is supported by National Natural Science Foundation of China under Grant No.49794030Ministry of Science Technology of China(G1998040908)
文摘In order to investigate the effect of the factors in tower latitudes on Meiyu/Baiu front,a diagnostic analysis for the two cases during June to July of 1985 and 1986 was examined.We found that (1)when the tropical convective activity moves westward to 10.5-15.5′N/140°E from east side of 10.5-15.5°N/160°E,the northward shifts of the Meiyu/Baiu rain belt occurs;(2)the main factor which results in the northward and southward shifts of Meiyu/Baiu rain belt is thought as the 8,18 and 30 day oscillations of the tropical convective activity around West Pacific. Meanwhile,the wave train propagating from Lake Baikal via Okhotsk Sea to the tropics could sometimes shift Baiu rain belt southward;(3)the onsets of Meiyu in China of both cases tend to take place just when the convective activity around lower latitudes moves westward through about 140°E with the 8,18 and 30 day oscillation periods firstly coming to June.
文摘Based on the analyses of the moisture transport structure in the whole layer of the troposphere along the Yangtze River valley during draught/flood years using the NCEP reanalysis data, this paper reveals that there exists a key region with a “Large Triangle” shape of transporting moisture for the Tibetan Plateau to Meiyu Belt and its“source/sink” structure; discloses that the interannual variation of the whole budget of inflow and outflow of moisture through the boundaries of a “Large Triangle” key region has the in-phase characteristic. Then a moisture transport structure over the skirt of the plateau and a conceptual model on the “transfer post” of moisture transport in the area of the South China Sea-Tibetan Plateau-Yangtze River valley in summer are put forward in this paper: the anti-phase feature of whole layer moisture transport flow patterns of Yangtze River valley during drought/flooding years is exhibited using the computational scheme of whole layer moisture transport correlation vector fields; a comprehensive dynamic model and its physical diagram of the teleconnection source/sink structure of the moisture transport of the Meiyu rain belt have been made. It shows that the moisture transfer effect over the skirt of the plateau from the ocean (Indian Ocean, South China Sea and west North Pacific) led to a moisture confluence belt in the Yangtze River valley and the teleconnection moisture transport source/sink structure over the “Large Triangle” shape area in flooding years.
文摘2022年汛期,国家气候中心准确预测了“全国气候年景总体偏差,区域性、阶段性旱涝灾害明显,降水空间差异显著,主要多雨区在我国北方”的总趋势,较好、较早把握了汛期主雨带位置和全国旱涝分布。对东亚夏季风和雨季季节进程“南海夏季风5月第3候爆发,长江中下游入梅偏早,梅雨量偏少,以及华北雨季开始偏早,雨量偏多”的预测与实况一致。对夏季台风生成个数较常年偏少,盛夏出现北上台风可能性大的预测与实况基本吻合。准确预测了全国平均气温趋势和高温异常特征。对“夏季我国中东部大部气温偏高,华东、华中、新疆等地高温日数较常年同期偏多,可能出现阶段性高温热浪”的预测与实况一致。主要不足之处是对长江中下游和川渝地区高温干旱的范围和极端程度估计不足。2022年汛期预测重点考虑连续La Ni a事件和印度洋偶极子负位相对东亚夏季风环流的影响,夏季西太平洋副热带高压强度偏强,脊线位置偏北,东亚夏季风偏强,初夏东北冷涡活跃,导致汛期主雨带位于东北、华北和西北地区东部等地。
