[Objective]The research aimed to study variation characteristics of large-scale frost in the east region of the Yellow River of Gansu in recent 40 years.[Method]Based on daily minimum temperature data at 15 meteorolog...[Objective]The research aimed to study variation characteristics of large-scale frost in the east region of the Yellow River of Gansu in recent 40 years.[Method]Based on daily minimum temperature data at 15 meteorological stations over the east region of the Yellow River of Gansu from 1969 to 2008,according to common climatic statistical index of the frost,variation characteristics of the large-scale frost and continuous frost in the east region of the Yellow River of Gansu in recent 40 years were studied.[Result]Since the 1990s,average last frost date in the east region of the Yellow River of Gansu obviously advanced,and first frost date started to obviously postpone.Advancing time of the last frost date was longer than postponing time of the first frost date.Average frost-free period also obviously prolonged.Extremely early first frost date and extremely late last frost date mainly happened in the 1970s and the 1980s.Extremely late first frost date and extremely early last frost date mainly happened after the middle period of the 1990s.Extremely long frost-free period gradually started to appear frequently.In recent 40 years,the continuous frost gradually decreased,and the intensity also declined.[Conclusion]The research was favorable for understanding change characteristics of the frost and climate in the east region of the Yellow River of Gansu,and had important guidance significance for improving prediction capability of the abnormal frost disaster,effectively preventing frost disaster and improving crop yield in the area.展开更多
利用欧洲中期天气预报中心(European Center for Medium-Range Weather Forecasts,ECMWF)提供的ERA-Interim再分析资料和日本高知大学提供的红外卫星云图,从夏季东亚地区134个“大气河”个例中挑选了4个典型个例分析其天气形势和演变过...利用欧洲中期天气预报中心(European Center for Medium-Range Weather Forecasts,ECMWF)提供的ERA-Interim再分析资料和日本高知大学提供的红外卫星云图,从夏季东亚地区134个“大气河”个例中挑选了4个典型个例分析其天气形势和演变过程,考察其水平与垂直结构。发现有两个南-北向的“大气河”在气旋东部暖输送带上发展,另外两个东-西向的“大气河”分别在两气旋之间的锋面上、低压与副热带高压之间发展。整体而言,“大气河”位于500 hPa以下,在1000 hPa上低压天气系统的东部或外围。在有锋面伴随的情况下,水汽输送带会沿着锋面延伸。在没有锋面伴随的情况下,“大气河”会沿着低空气旋式环流外围延伸。“大气河”内800 hPa高度附近有低空急流,与锋面之间有上升运动。“大气河”输送方向的左侧200 hPa高度附近有急流。最后本文给出了夏季影响东亚地区两种“大气河”的空间概念示意图。展开更多
基金Supported by National Science and Technology Support Plan(2009BAC53B02)National Natural Science Fund Item (41075103)Special Item of the Public Welfare Industry (Meteorology) Science and Research (GYHY201106034,GYHY201006023)
文摘[Objective]The research aimed to study variation characteristics of large-scale frost in the east region of the Yellow River of Gansu in recent 40 years.[Method]Based on daily minimum temperature data at 15 meteorological stations over the east region of the Yellow River of Gansu from 1969 to 2008,according to common climatic statistical index of the frost,variation characteristics of the large-scale frost and continuous frost in the east region of the Yellow River of Gansu in recent 40 years were studied.[Result]Since the 1990s,average last frost date in the east region of the Yellow River of Gansu obviously advanced,and first frost date started to obviously postpone.Advancing time of the last frost date was longer than postponing time of the first frost date.Average frost-free period also obviously prolonged.Extremely early first frost date and extremely late last frost date mainly happened in the 1970s and the 1980s.Extremely late first frost date and extremely early last frost date mainly happened after the middle period of the 1990s.Extremely long frost-free period gradually started to appear frequently.In recent 40 years,the continuous frost gradually decreased,and the intensity also declined.[Conclusion]The research was favorable for understanding change characteristics of the frost and climate in the east region of the Yellow River of Gansu,and had important guidance significance for improving prediction capability of the abnormal frost disaster,effectively preventing frost disaster and improving crop yield in the area.
文摘利用欧洲中期天气预报中心(European Center for Medium-Range Weather Forecasts,ECMWF)提供的ERA-Interim再分析资料和日本高知大学提供的红外卫星云图,从夏季东亚地区134个“大气河”个例中挑选了4个典型个例分析其天气形势和演变过程,考察其水平与垂直结构。发现有两个南-北向的“大气河”在气旋东部暖输送带上发展,另外两个东-西向的“大气河”分别在两气旋之间的锋面上、低压与副热带高压之间发展。整体而言,“大气河”位于500 hPa以下,在1000 hPa上低压天气系统的东部或外围。在有锋面伴随的情况下,水汽输送带会沿着锋面延伸。在没有锋面伴随的情况下,“大气河”会沿着低空气旋式环流外围延伸。“大气河”内800 hPa高度附近有低空急流,与锋面之间有上升运动。“大气河”输送方向的左侧200 hPa高度附近有急流。最后本文给出了夏季影响东亚地区两种“大气河”的空间概念示意图。
