2015年1月27—28日宁夏出现首场降雪过程,利用常规气象资料,从首场降雪环流演变特征、影响系统、T-ln P图的应用等方面进行了分析。结果表明,中纬度500 h Pa有清晰的高空锋区和冷平流输送;700 h Pa有低涡、切变及偏南低空急流配合;地面...2015年1月27—28日宁夏出现首场降雪过程,利用常规气象资料,从首场降雪环流演变特征、影响系统、T-ln P图的应用等方面进行了分析。结果表明,中纬度500 h Pa有清晰的高空锋区和冷平流输送;700 h Pa有低涡、切变及偏南低空急流配合;地面有倒槽和回流形势。大于80%高湿区主要集中在700 h Pa以下层,银川湿对流有效位能CAPE从0增加至180 J/kg,说明冬季降雪需储备一定的能量条件。将宁夏日常业务中常用的EC_MOS、T639_MOS、WRF等3种数值模式和中央指导产品的客观要素预报与区台订正预报进行比较,使用了Ts评分和误差分析对该次降雪各预报产品的日最高、最低温度和晴雨(雪)在宁夏的预报效果进行检验评估,总结了各模式产品在本地的预报性能特点。展开更多
Although zircon U-Pb geochronometer has been widely used for dating metamorphism in moderate- to high-grade metamorphic rocks, it is still difficult to link the zircon U-Pb age to pressure and temperature （P-T） cond...Although zircon U-Pb geochronometer has been widely used for dating metamorphism in moderate- to high-grade metamorphic rocks, it is still difficult to link the zircon U-Pb age to pressure and temperature （P-T） conditions. In this study, zircon trace elements and Hf isotopes and REE partitioning between zircon and garnet are adopted to track the formation condition of zircon in the granu- lites from North Tongbai Orogen, Central China. Combined with previous metamorphic P-T path results, a quantitative integrated anticlockwise P-T-t path was established for Tongbai granulites. These grauulites recorded an early low-P heating followed by a dramatic pressure increase. Evidence for the prograde history （M1） is provided by cordierite, orthopyroxene and biotite inclusions in garnet. The prograde metamorphism occurred at around 443±3 Ma, with P-T conditions of ca. 730-820 ℃ and 〈6 kbar. The peak metamorphic （M2） condition is 〉920 ℃ and 8.5-10 kbar and the peak metamorphism age is ca. 432±4 Ma. At around 419 Ma, the granulites suffered an amphibolite-facies retrograde metamorphism （M3）, represented by the replacement of garnet by biotite and plagioclase, and clinopyroxene by amphibole, with metamorphic condition of ca. 700℃ and ca. 7 kbar. The last retrograde metamorphism （M4） is a greenschist-facies overprint with an age of ca. 404 Ma. It is concluded that the meta- morphism of Tongbai granulite lasted for more than 40 Ma, including a stage of more than 20 Ma granulitc-facies metamorphism. The prolonged granulite-facies metamorphism resulted from the continuous northward subduction of the Shangdan oceanic crust beneath the North Qinling terrane.展开更多
文摘2015年1月27—28日宁夏出现首场降雪过程,利用常规气象资料,从首场降雪环流演变特征、影响系统、T-ln P图的应用等方面进行了分析。结果表明,中纬度500 h Pa有清晰的高空锋区和冷平流输送;700 h Pa有低涡、切变及偏南低空急流配合;地面有倒槽和回流形势。大于80%高湿区主要集中在700 h Pa以下层,银川湿对流有效位能CAPE从0增加至180 J/kg,说明冬季降雪需储备一定的能量条件。将宁夏日常业务中常用的EC_MOS、T639_MOS、WRF等3种数值模式和中央指导产品的客观要素预报与区台订正预报进行比较,使用了Ts评分和误差分析对该次降雪各预报产品的日最高、最低温度和晴雨(雪)在宁夏的预报效果进行检验评估,总结了各模式产品在本地的预报性能特点。
基金supported by the National Natural Science Foundation of China (No. 41302040)the China Geological Survey (No. DD20160201)
文摘Although zircon U-Pb geochronometer has been widely used for dating metamorphism in moderate- to high-grade metamorphic rocks, it is still difficult to link the zircon U-Pb age to pressure and temperature （P-T） conditions. In this study, zircon trace elements and Hf isotopes and REE partitioning between zircon and garnet are adopted to track the formation condition of zircon in the granu- lites from North Tongbai Orogen, Central China. Combined with previous metamorphic P-T path results, a quantitative integrated anticlockwise P-T-t path was established for Tongbai granulites. These grauulites recorded an early low-P heating followed by a dramatic pressure increase. Evidence for the prograde history （M1） is provided by cordierite, orthopyroxene and biotite inclusions in garnet. The prograde metamorphism occurred at around 443±3 Ma, with P-T conditions of ca. 730-820 ℃ and 〈6 kbar. The peak metamorphic （M2） condition is 〉920 ℃ and 8.5-10 kbar and the peak metamorphism age is ca. 432±4 Ma. At around 419 Ma, the granulites suffered an amphibolite-facies retrograde metamorphism （M3）, represented by the replacement of garnet by biotite and plagioclase, and clinopyroxene by amphibole, with metamorphic condition of ca. 700℃ and ca. 7 kbar. The last retrograde metamorphism （M4） is a greenschist-facies overprint with an age of ca. 404 Ma. It is concluded that the meta- morphism of Tongbai granulite lasted for more than 40 Ma, including a stage of more than 20 Ma granulitc-facies metamorphism. The prolonged granulite-facies metamorphism resulted from the continuous northward subduction of the Shangdan oceanic crust beneath the North Qinling terrane.
