【摘要】 2007年4月13日在河西走廊中西部发生了特强沙尘暴,极大风速25m/s,最小能见度50m。用风云2号卫星红外云图对下沉急流云头进行跟踪,并用NCEP(1°×1°)6h再分析数据对高速下沉急流到达冷锋云带前后的静力不稳定、条件不稳定、条件对称不稳定等进行了诊断分析。结果表明:这次强沙尘暴由高速下沉急流引起,急流头部触发了锋区附近强对流发生;凝结潜热释放先在对流层中层发生,然后向下发展,使对流层中下部转为条件不稳定层,700hPa附近的条件不稳定能量释放使边界层对流环流迅速增强,引发了这次特强沙尘暴。更多还原

【Abstract】 Based on FY-2 infrared images and the reanalysis data for six hours of NCEP(1°×1°),the heavy dust storm process occurred on 13 April 2007 in the middle west part of Hexi corridor is analyzed,particularly the cloud head of the descending jet was tracked and the gravitational instability,conditional symmetric instability and conditional instability are diagnosed in detail.Results show that a high speed descending jet resulted in this heavy dust storm and the jet triggered strong convection in frontal region,and conditional instability occurred in the middle part of troposphere first,then developed downwards.The release of conditional instability energy at the level of 700 hPa caused rapid development of convective circulation in boundary and brought on this heavy dust storm.更多还原