The responses of vertical structures, in convective and stratiform regions, to the large-scale forcing during the landfall of tropical storm Bilis （2006） are investigated using the data from a two-dimensional cloud-...The responses of vertical structures, in convective and stratiform regions, to the large-scale forcing during the landfall of tropical storm Bilis （2006） are investigated using the data from a two-dimensional cloud-resolving model simulation. An imposed large-scale forcing with upward motion in the mid and upper troposphere and downward motion in the lower troposphere on 15 July suppresses convective clouds, which leads to -100% coverage of raining stratiform clouds over the entire model domain. The imposed forcing extends upward motion to the lower troposphere during 16-17 July, which leads to an enhancement of convective clouds and suppression of raining stratiform clouds. The switch of large-scale lower-tropospheric vertical velocity from weak downward motion on 15 July to moderate upward motion during 16-17 July produces a much broader distribution of the vertical velocity, water vapor and hydrometeor fluxes, perturbation specific humidity, and total hydrometeor mixing ratio during 16-17 July than those on 15 July in the analysis of contoured frequency-altitude diagrams. Further analysis of the water vapor budget reveals that local atmospheric moistening is mainly caused by the enhancement of evaporation of rain associated with downward motion on 15 July, whereas local atmospheric drying is mainly determined by the advective drying associated with downward motion over raining stratiform regions and by the net condensation associated with upward motion over convective regions during 16-17 July.展开更多
大气可降水量(precipitable water vapor,PWV)在多尺度气候变化及大气物理过程中扮演着重要的角色。为提高PWV垂直改正精度进一步扩展各类PWV产品的空间应用性,本文基于2010—2019年ERA5再分析资料构建了一种顾及PWV垂直衰减系数时空变...大气可降水量(precipitable water vapor,PWV)在多尺度气候变化及大气物理过程中扮演着重要的角色。为提高PWV垂直改正精度进一步扩展各类PWV产品的空间应用性,本文基于2010—2019年ERA5再分析资料构建了一种顾及PWV垂直衰减系数时空变化的全球适用范围的分层格网模型(GPWVCS)。同时联合2020年ERA5及无线电探空PWV,评估了本文模型在全球范围内的精度及适用性。结果表明,相比于经验模型及未分层的GPWVC模型,GPWVCS模型有效提升了PWV的垂直改正精度。以ERA5 PWV为参考,全球范围内GPWVCS模型修正PWV的RMS不超过1.9 mm。以探空数据为参考,GPWVCS模型在热带、温带、寒带及全球范围的年均RMS分别为2.24、1.29、0.44、1.44 mm,较经验模型分别提升34.6%、14.1%、10.9%及21.4%,较GPWVC模型分别提升6.4%、5.8%、9.4%及6.0%。GPWVCS的分层算法最大限度地削弱了PWV指数外推的误差累积影响,本文开发的水平分辨率为1°×1°、2°×2°及5°×5°的模型均能够显著提升全球范围内多种高差下PWV的垂直改正效果,用户可以根据计算效率及精度需求自行选择最佳模型。展开更多
GNSS水汽层析技术可以反演对流层水汽三维时空变化情况,但该技术比较复杂、运算量大,需要消耗一定的时间.故本文提出了一种利用地基GNSS反演的大气可降水量(precipitable water vapor,PWV)结合水汽在垂直方向上的指数分布特性来计算大...GNSS水汽层析技术可以反演对流层水汽三维时空变化情况,但该技术比较复杂、运算量大,需要消耗一定的时间.故本文提出了一种利用地基GNSS反演的大气可降水量(precipitable water vapor,PWV)结合水汽在垂直方向上的指数分布特性来计算大气水汽三维分布的快速层析方法.该方法利用香港地区2022年8月的GNSS数据开展试验,与传统GNSS水汽层析方法进行对比.试验结果表明:两种方法的层析解算结果与探空数据均具有良好的一致性.虽然快速层析方法的解算结果在底层区域缺少一些水汽变化的细节信息,精度略逊于传统层析方法,但是在中、高层时精度会有所提升,层析解算结果良好.而且本文提出的快速层析方法无需构建和解算复杂的层析方程组,可以在大量GNSS测站参与水汽层析时减少计算复杂度,提升运算能力,同时可以更快地得到任意高度层的水汽密度,是一种简便、高效的层析方法.展开更多
基金supported by the State Key Basic Research Development Program (2004CB418300 and 2009CB421504)the National Natural Science Foundation of China under Grant Nos.40633016 and 40830958
文摘The responses of vertical structures, in convective and stratiform regions, to the large-scale forcing during the landfall of tropical storm Bilis （2006） are investigated using the data from a two-dimensional cloud-resolving model simulation. An imposed large-scale forcing with upward motion in the mid and upper troposphere and downward motion in the lower troposphere on 15 July suppresses convective clouds, which leads to -100% coverage of raining stratiform clouds over the entire model domain. The imposed forcing extends upward motion to the lower troposphere during 16-17 July, which leads to an enhancement of convective clouds and suppression of raining stratiform clouds. The switch of large-scale lower-tropospheric vertical velocity from weak downward motion on 15 July to moderate upward motion during 16-17 July produces a much broader distribution of the vertical velocity, water vapor and hydrometeor fluxes, perturbation specific humidity, and total hydrometeor mixing ratio during 16-17 July than those on 15 July in the analysis of contoured frequency-altitude diagrams. Further analysis of the water vapor budget reveals that local atmospheric moistening is mainly caused by the enhancement of evaporation of rain associated with downward motion on 15 July, whereas local atmospheric drying is mainly determined by the advective drying associated with downward motion over raining stratiform regions and by the net condensation associated with upward motion over convective regions during 16-17 July.
文摘GNSS水汽层析技术可以反演对流层水汽三维时空变化情况,但该技术比较复杂、运算量大,需要消耗一定的时间.故本文提出了一种利用地基GNSS反演的大气可降水量(precipitable water vapor,PWV)结合水汽在垂直方向上的指数分布特性来计算大气水汽三维分布的快速层析方法.该方法利用香港地区2022年8月的GNSS数据开展试验,与传统GNSS水汽层析方法进行对比.试验结果表明:两种方法的层析解算结果与探空数据均具有良好的一致性.虽然快速层析方法的解算结果在底层区域缺少一些水汽变化的细节信息,精度略逊于传统层析方法,但是在中、高层时精度会有所提升,层析解算结果良好.而且本文提出的快速层析方法无需构建和解算复杂的层析方程组,可以在大量GNSS测站参与水汽层析时减少计算复杂度,提升运算能力,同时可以更快地得到任意高度层的水汽密度,是一种简便、高效的层析方法.
文摘大气加权平均温度(Atmospheric Weighted Mean Temperature,Tm)是全球导航卫星系统(Global Navigation Satellite System,GNSS)反演水汽的关键因素,针对已有的中国南部区域大气加权平均温度模型未同时顾及Tm的高程非线性垂直变化和日周期变化特征,提出利用2015—2017年的欧洲中期天气预报中心(European Center for Medium-Range Weather Forecasts,ECMWF)提供的第5代再分析资料建立了水平分辨率为1°×1°的中国南部Tm模型(CNXNTm模型)。用未参与建模的2018年ERA5再分析资料积分计算的Tm和探空站Tm数据为参考值,对CNXNTm模型进行精度检验,与目前精度较好的IGPT2W模型和最新的GPT3模型进行比较分析。结果表明,在统计的22个气压层内CNXNTm模型偏差(BIAS)和均方根误差(RMSE)分别为0.14、2.26 K,相对于IGPT2W模型的0.73、5.38 K提升了81%和58%,相对于GPT3模型的17.66、17.81 K提升了99%和87%。在所有气压层范围,CNXNTm模型结果变化小,稳定性强。在内陆与沿海比较中CNXNTm模型适应性更好。因此顾及了非线性垂直变化的CNXNTm模型估计值更接近Tm在垂直高度上的变化趋势,并且顾及了日变化的CNXNTm模型能够获得更精细的Tm值日周期变化特征,可为中国南部区域实时、高精度GNSS水汽监测提供参考。
