High spatiotemporal resolution infrared radiances from FY-4A/AGRI(Advanced Geostationary Radiation Imager)can provide crucial information for rapidly developing severe convective weather.This study established a symme...High spatiotemporal resolution infrared radiances from FY-4A/AGRI(Advanced Geostationary Radiation Imager)can provide crucial information for rapidly developing severe convective weather.This study established a symmetric observation error model that differentiates between land and sea for FY-4A/AGRI all-sky assimilation,developed an all-sky assimilation scheme for FY-4A/AGRI based on hydrometeor control variables,and investigated the impacts of all-sky FY-4A/AGRI water vapor channels at different altitudes and rapid-update assimilation at different frequencies on the assimilation and forecasting of a severe convective weather event.Results show that simultaneous assimilation of two water vapor channels can enhance precipitation forecasts compared to single-channel assimilation,which is mainly attributable to a more accurate analysis of water vapor and hydrometeor information.Experiments with different assimilation frequencies demonstrate that the hourly assimilation frequency,compared to other frequencies,incorporates the high-frequency information from AGRI while reducing the impact of spurious oscillations caused by excessively high-frequency assimilation.This hourly assimilation frequency reduces the incoordination among thermal,dynamical,and water vapor conditions caused by excessively fast or slow assimilation frequencies,thus improving the forecast accuracy compared to other frequencies.展开更多
为了解FY-4A卫星云顶高度(cloud top height,CTH)产品对陕南暖季降水云的反映状况,以陕南地区2020年暖季(5-10月)降水过程为例,对比分析FY-4A卫星CTH产品与汉中天气雷达回波顶高(echo top height,ET)产品对该地区降水云的探测资料。结...为了解FY-4A卫星云顶高度(cloud top height,CTH)产品对陕南暖季降水云的反映状况,以陕南地区2020年暖季(5-10月)降水过程为例,对比分析FY-4A卫星CTH产品与汉中天气雷达回波顶高(echo top height,ET)产品对该地区降水云的探测资料。结果表明:(1)在暖季21次降水过程中,卫星产品的云顶高度揭示了陕南地区降水云的空间变化,尤其在大巴山峡口附近,CTH值显著偏高的区域与陕南强降水的多发区相吻合。(2)以2020年暖季一次强降水过程为例,云顶高度探测表明卫星CTH的高值区通常与雷达ET的高值区相对应,说明卫星能够揭示陕南山区降水云体的时空变化,但在雷达ET高值区卫星CTH存在以填充值代替的现象,说明复杂地形区CTH填充值可能是潜在强降水区。(3)对比两种探测在降水云体发展中差异,结果显示在降水云初生和消亡阶段,两者绝对差值小于2 km的格点数与总格点数的占比都超过50%,说明CTH产品能有效捕捉降水云的初生和消亡变化。在降水云成熟阶段,两者平均差值超过4 km,卫星探测云体不确定性增加,较难反映降水云体特征。展开更多
基金supported by the National Key R&D Program of China(Grant No.2022YFC3080500)the National Natural Science Foundation of China(Grant Nos.U2142208,42475158,and 42105149)the High-Performance Computing Center of Nanjing University of Information Science&Technology for supporting this work。
文摘High spatiotemporal resolution infrared radiances from FY-4A/AGRI(Advanced Geostationary Radiation Imager)can provide crucial information for rapidly developing severe convective weather.This study established a symmetric observation error model that differentiates between land and sea for FY-4A/AGRI all-sky assimilation,developed an all-sky assimilation scheme for FY-4A/AGRI based on hydrometeor control variables,and investigated the impacts of all-sky FY-4A/AGRI water vapor channels at different altitudes and rapid-update assimilation at different frequencies on the assimilation and forecasting of a severe convective weather event.Results show that simultaneous assimilation of two water vapor channels can enhance precipitation forecasts compared to single-channel assimilation,which is mainly attributable to a more accurate analysis of water vapor and hydrometeor information.Experiments with different assimilation frequencies demonstrate that the hourly assimilation frequency,compared to other frequencies,incorporates the high-frequency information from AGRI while reducing the impact of spurious oscillations caused by excessively high-frequency assimilation.This hourly assimilation frequency reduces the incoordination among thermal,dynamical,and water vapor conditions caused by excessively fast or slow assimilation frequencies,thus improving the forecast accuracy compared to other frequencies.
文摘为了解FY-4A卫星云顶高度(cloud top height,CTH)产品对陕南暖季降水云的反映状况,以陕南地区2020年暖季(5-10月)降水过程为例,对比分析FY-4A卫星CTH产品与汉中天气雷达回波顶高(echo top height,ET)产品对该地区降水云的探测资料。结果表明:(1)在暖季21次降水过程中,卫星产品的云顶高度揭示了陕南地区降水云的空间变化,尤其在大巴山峡口附近,CTH值显著偏高的区域与陕南强降水的多发区相吻合。(2)以2020年暖季一次强降水过程为例,云顶高度探测表明卫星CTH的高值区通常与雷达ET的高值区相对应,说明卫星能够揭示陕南山区降水云体的时空变化,但在雷达ET高值区卫星CTH存在以填充值代替的现象,说明复杂地形区CTH填充值可能是潜在强降水区。(3)对比两种探测在降水云体发展中差异,结果显示在降水云初生和消亡阶段,两者绝对差值小于2 km的格点数与总格点数的占比都超过50%,说明CTH产品能有效捕捉降水云的初生和消亡变化。在降水云成熟阶段,两者平均差值超过4 km,卫星探测云体不确定性增加,较难反映降水云体特征。
