9403号强热带风暴水汽通量非对称研究

用实测资料对9403号南海强热带风暴(简称TC,以下同)登陆前后的物理结构变化作了分析,对其水汽通量、动力学等特征量进行了计算。研究结果表明：TC的水汽通量分布不对称,辐合主要在边界层中,辐合最大值出现在TC登陆前南半圆边界层附近：风速分布不对称,气旋性切向风大值区位于TC东半圆;风速垂直切变随TC加强而减弱。强流入位于TC南半圆400hPa以下,流入大值区在850hPa附近;高层反气旋流出在150-100hPa层附近,流出主要位于TC北半圆。TC垂直运动分布不对称,上升最大值出现在南半网。TC整个生命期均具有暖心结构,300hPa附近增暖最明显。     

海洋飞沫对热带气旋边界层结构的影响

将海洋飞沫参数化引入到一个高分辨率、非静力中尺度WRF模式中,对0908号热带气旋Morakot进行数值模拟,探讨了海洋飞沫对热带气旋Morakot边界层结构和强度的影响。模拟结果表明:采用新参数化后,对热带气旋Morakot的强度预报有改进,但对热带气旋移动路径改进不大;其次,通过对边界层过程的改进,使得眼墙区域的平均径向风速、切向风速、温度、相对湿度、垂直风速、热通量,降水等物理量均有增强,各物理量的贡献对热带气旋Morakot强度和结构变化的影响十分重要。     

Simulation of Typhoon Muifa using a mesoscale coupled atmosphere–ocean model

A mesoscale coupled atmosphere–ocean model has been developed based on the GRAPES(Global and Regional Assimilation and Prediction System) regional typhoon model(GRAPES_TYM) and ECOM-si(estuary, coast and ocean model(semi-implicit)). Coupling between the typhoon and ocean models was conducted by exchanging wind stress, heat, moisture fluxes, and sea surface temperatures(SSTs) using the coupler OASIS3.0. Numerical prediction experiments were run with and without coupling for the case of Typhoon Muifa in the western North Pacific. To investigate the impact of using more accurate SST information on the simulation of the track and the intensity of Typhoon Muifa, experiments were also conducted using increased SST resolution in the initial condition field of the control test. The results indicate that increasing SST resolution in the initial condition field somewhat improved the intensity forecast, and use of the coupled model improved the intensity forecast significantly, with mean absolute errors in maximum wind speed within 48 and 72 h reduced by 32% and 20%, respectively. Use of the coupled model also resulted in less pronounced over-prediction of the intensity of Typhoon Muifa by the GRAPES_TYM. Moreover, the effects of using the coupled model on the intensity varied throughout the different stages of the development of Muifa owing to changes in the oceanic mixed layer depth. The coupled model had pronounced effects during the later stage of Muifa but had no obvious effects during the earlier stage. The SSTs predicted by the coupled model decreased by about 5–6°C at most after the typhoon passed, in agreement with satellite data. Furthermore, based on analysis on the sea surface heat flux, wet static energy of the boundary layer, atmospheric temperature, and precipitation forecasted by the coupled model and the control test, the simulation results of this coupled atmosphere–ocean model can be considered to reasonably reflect the primary mechanisms underlying the interactions between tropical cyclones and oceans.     

Importance of tropical cyclone heat potential for tropical cyclone intensity and intensification in the Western North Pacific

Which is more important for tropical cyclone (TC) intensity and intensification, sea surface temperature (SST) or tropical cyclone heat potential (TCHP)? Investigations using best-track TC central pressures, TRMM/TMI three-day mean SST data, and an estimated TCHP based on oceanic reanalysis data from 1998 to 2004, show that the central pressure is more closely related to TCHP accumulated from TC formation to its mature stages than to the accumulated SST and its duration. From an oceanic environmental viewpoint, a rapid deepening of TC central pressure occurs when TCHP is relatively high on a basin scale, while composite distributions of TCHP, vertical wind shear, lower tropospheric relative humidity, and wind speed occurring in cases of rapid intensification are different for each TC season. In order to explore the influence of TCHP on TC intensity and intensification, analyses using both oceanic reanalysis data and the results of numerical simulations based on an ocean general circulation model are performed for the cases of Typhoons Chaba (2004) and Songda (2004), which took similar tracks. The decrease in TCHP due to the passage of Chaba led to the suppression of Songda’s intensity at the mature stage, while Songda maintained its intensity for a relatively long time because induced near-inertial currents due to the passage of Chaba reproduced anticyclonic warm eddies appearing on the leftside of Chaba’s track before Songda passed by. This type of intensity-sustenance process caused by the passage of a preceding TC is often found in El Niño years. These results suggest that TCHP, but not SST, plays an important role in TC intensity and its intensification.     

海洋对热带气旋响应的一种改进模式

建立一个改进的二层非线性原始方程海洋模式，研究海洋对热带气旋的响应。采用湍流动能收支参数化风应力产生的垂直混合（夹卷），其中考虑了盐度对层结强度的影响。通过海洋对７００２号台风响应的数值模拟，结果表明，在引起海表温度下降的各热通量分量中，夹卷约占了８３％，余下的海表面热通量占了１７％。在台风路径转向的右侧，海洋出现强烈的降温，表现出明显的右偏性。降温的幅度、范围和形状均与观测结果较为一致。     

海洋对热带气旋响应的研究 Ⅰ.海洋对静止、移速不同的热带气旋响应

建立一个二层非线性原始方程海洋模式，用以研究海洋对静止和以不同移速移动的热带气旋（TC）的响应。数值试验结果表明，海洋对静止TC的响应，具有不对称性；在TC中心处，抽吸使混合层（ML）变浅，在TC最大风速半径处，大风夹卷明显使ML加深和海表温（SST）下降；海洋对移动TC的响应，具有右偏性，且随移速加快而加剧。ML深度和SST的变化对TC移速十分敏感，而海流则不同。     

基于回归模型的热带气旋条件下的海表降温参数化方案设计

Combining a linear regression and a temperature budget formula, a multivariate regression model is proposed to parameterize and estimate sea surface temperature(SST) cooling induced by tropical cyclones(TCs). Three major dynamic and thermodynamic processes governing the TC-induced SST cooling(SSTC), vertical mixing, upwelling and heat flux, are parameterized empirically using a combination of multiple atmospheric and oceanic variables:sea surface height(SSH), wind speed, wind curl, TC translation speed and surface net heat flux. The regression model fits reasonably well with 10-year statistical observations/reanalysis data obtained from 100 selected TCs in the northwestern Pacific during 2001–2010, with an averaged fitting error of 0.07 and a mean absolute error of 0.72°C between diagnostic and observed SST cooling. The results reveal that the vertical mixing is overall the pre dominant process producing ocean SST cooling, accounting for 55% of the total cooling. The upwelling accounts for 18% of the total cooling and its maximum occurs near the TC center, associated with TC-induced Ekman pumping. The surface heat flux accounts for 26% of the total cooling, and its contribution increases towards the tropics and the continental shelf. The ocean thermal structures, represented by the SSH in the regression model,plays an important role in modulating the SST cooling pattern. The concept of the regression model can be applicable in TC weather prediction models to improve SST parameterization schemes.     

环境条件对0709号超强台风“圣帕”影响的分析

利用多种卫星观测资料和NCAR／NCEP提供的分析场，分析海温和环境垂直风切变这两个环境因素对0709号超强台风“圣帕”的强度、对流和降水结构的影响．结果表明：强度的变化和环境垂直风切变之间没有直接相关性，海温是影响强度变化的主要环境因素；最大对流区域位于顺切变方向左侧；较强切变条件下，在内眼壁上的最大降水位于顺切变方向左侧，降水呈一波非对称分布；在外围螺旋雨带上的最大降水区域则分布在顺切变方向上或顺切变方向右侧．     

海面温度变化影响台风"海棠"强度的数值研究

通过对台风"海棠"5 d的数值模拟,研究海表温度(SST)变化对台风强度的影响。与NCEP月平均海表温度相对比,在中尺度大气模式中引入热带测雨卫星(TRMM)微波成像仪(TMI)/先进微波扫描辐射计(AMSR-E)来考察SST对台风"海棠"路径和强度的影响。研究结果表明,每天变化SST的试验模拟的台风强度和路径整体效果不错;模拟的台风路径不敏感于SST的变化,而台风强度的变化不仅取决于由于台风移动引发的SST冷却的幅度大小,而且取决于SST冷却区域的相对位置。在台风"海棠"强烈发展过程中,台风中心右侧冷却区对台风中心气压影响很小;台风强烈发展过后,SST冷却区开始影响台风强度,但造成台风中心气压下降幅度不大,6 h内台风中心气压减弱约3.9 hPa。海面热量通量和海面风速与SST的分布都有良好的相关性:在SST变化为正值的暖水区,感热通量和潜热通量都是一个正的通量分布的极值区,并有风速极大值区域存在;在台风右侧相应的冷却区,则存在着负的通量异常和风速极小值区域。     

海洋飞沫方案改进对台风“威马逊”强度预报的影响

本文采用分粒径段组合方式改进海气耦合模式海洋飞沫方案,并利用耦合模式对1409号台风"威马逊"进行数值模拟,分析了海洋飞沫方案改进对台风结构、强度以及海气动量通量、热量通量模拟结果的影响。结果显示,耦合模式中海洋飞沫方案可通过改变海表面粗糙度影响海气动量与热量通量;海洋飞沫还可以通过沫滴向大气输送感热和水汽而直接影响海气热通量,进一步影响台风的强度。模拟结果显示改进后海洋飞沫方案的台风强度更接近观测。改进海洋飞沫方案后粗糙度的计算结果小于原始方案,相应地海气热通量以及下垫面耗散作用也弱于后者,海表面风场是海气热交换与下垫面耗散共同作用的结果。     

海洋对静止热带气旋响应的某些特征

建立二层非线性原始方程海洋模式，采用湍流动能收支参数化风应力产生的垂直混合（夹卷），研究海洋对不同强度和最大风速半径的静止热带气旋（ＴＣ）的响应。数值试验结果表明，由于科氏参数随纬度变化，海洋对热带气旋的响应具有不对称性。热带气旋强度对海流，上混合层（ＵＭＬ）深度和海表温（ＳＳＴ）变化量值产生重大影响，并对它们变化范围影响较大。热带气旋最大风速半径对海流、混合层深度和海表温变化量值的影响不明显，但对它们的变化范围有明显影响。     

海面温度半球间偶极子模态对7—11月北半球平均热带气旋强度年代际变化的调控

海面温度半球间偶极子(sea surface temperature inter-hemispheric dipole,SSTID)是全球海面温度(sea surface temperature,SST)异常的重要模态之一,表现为南、北两半球间SST的反相变化。此文探究了7—11月SSTID对7—11月北半球平均热带气旋(tropical cyclone,TC)强度年代际变率的超前影响。观测分析表明,SSTID超前7—11月北半球平均TC强度年代际分量8~11 a,并在提前时间为9 a时达到最大正相关。通过海洋-大气耦合桥理论进一步分析表明,7—11月北半球TC活跃区海洋可以作为海洋桥,以SST的形式存储超前约9 a的SSTID信号。同时北半球TC活跃区大气作为大气桥将超前约9 a的SSTID信号传递到大气中,进而作用于7—11月北半球平均TC强度,该过程以TC潜在生成指数为表征。北半球TC活跃区的垂直风切变和600 hPa相对湿度的综合影响在其中起关键作用。由此建立了基于SSTID的7—11月北半球平均TC强度年代际变化预测模型,该模型表现出良好的后报性能。利用该模型对2021—2029年7—11月北半球平均TC强度预测表明,7—11月北半球平均TC强度将以持续增强为主并在2020年代末达到破纪录的强度。     

西北太平洋热带气旋的闪电特征及其与强度关系的初步分析

使用TRMM卫星搭载的闪电成像传感器测得的1998-2005年间的闪电信息,结合热带气旋的活动特征,提出了一种识别热带气旋闪电的方法,进而分离了1998-2005年西北太平洋热带气旋的闪电信息,并在此基础上,对西北太平洋的热带气旋闪电特征进行了初步分析.结果表明:西北太平洋热带气旋的眼壁附近(距热带气旋中心约30~50km)、内雨带(热带气旋中心外约60~100km)和外雨带(热带气旋中心外约130~610km)内普遍存在闪电现象,而且各月均有发生,并以7-8月较频;我国东南沿海地区,特别是台湾岛-台湾海峡-福建沿海地区、珠江三角洲的近海海域,是最易发生热带气旋闪电的两个区域,而日本岛东南方向广阔的西北太平洋洋面上的热带气旋,则较少有闪电发生.此外,闪电与热带气旋的强度及其变化有一定的关系,利用发生在热带气旋不同区域的闪电信息可对热带气旋的强度进行估算,估算的误差与目前的业务定强误差接近.     

Seasonal variation of atmospheric coupling with oceanic mesoscale eddies in the North Pacific Subtropical Countercurrent

This study investigated the seasonal variation in the atmospheric response to oceanic mesoscale eddies in the North Pacific Subtropical Countercurrent (STCC) and its mechanism, based on satellite altimetric and reanalysis datasets. Although mesoscale eddy in the study area is more active in summer, the sea surface temperature (SST) anomaly associated with mesoscale eddies is more intense and dipolar in winter, which is largely due to the larger background SST gradient. Similarly, the impact of the oceanic eddy on sea surface wind speed and heat flux is strongest in winter, whereas its effect on precipitation rate is more significant in summer. The study revealed that the SST gradient in STCC could impact the atmosphere layer by up to 800 hPa (900 hPa) in boreal winter (summer) through the dominant vertical mixing mechanism. Moreover, the intensity of the SST gradient causes such seasonal variation in mesoscale air-sea coupling in the study region. In brief, a stronger (weaker) background SST gradient field in wintertime (summertime) leads to a larger (smaller) eddy-induced SST anomaly, thus differently impacting atmosphere instability and transitional kinetic energy flux over oceanic eddies, leading to seasonal variation in mesoscale air-sea coupling intensity.     

A study of cross-shore maximum upwelling intensity along the Northwest Africa coast

Satellite images of sea surface temperature (SST) show that the location of cross-shore SST minimum (LCSM) stretches along the isobaths in the Northwest Africa Upwelling System. To understand and interpret these observations better, we set up a two-dimensional analytical model that takes into account the surface and bottom Ekman transport and the alongshore geostrophic current, as well as bottom friction and variations in bottom topography. The structure of vertical velocity with a realistic topography clearly illustrates the variations of SST drop in a sample cross-shore section. Some idealized theoretical model experiments are carried out to examine the effects of eddy viscosity, Coriolis force, and cross-shore wind on the location of the cross-shore maximum upwelling intensity. The results show that the cross-shore wind largely impacts on the location where the coldest water outcrops to the surface through an adjustment of the cross-shore pressure gradient. This is also verified by the remotely sensed data, which indicate that the maximum correlation coefficient between cross-shore wind stress and the depth of LCSM is ?0.65 with a lag of approximately 1 day.     

海洋表层温度对台风"蔷薇"路径和强度预测精度的影响

基于中尺度大气模式WRF(Weather Research and Forecasting Model),首先对2007年3次船舶辐射通量观测进行模拟,以检验WRF对长波和短波辐射通量的模拟能力,结果表明使用中国近海海洋环境数值预报系统环流模式POM(Princeton Ocean Model)模拟的高时空分辨率的海洋表层温度能够显著改进短波辐射通量的模拟,而对长波辐射通量模拟的改进不明显。然后,将业务化运行的中国近海海洋环境数值预报系统后报的逐时海洋表面温度(SST)作为WRF底边界条件,对2008年15号强台风"蔷薇"(Jangmi)过程进行了数值后报试验。结果表明,与使用NCEP/NCAR的SST试验后报的台风中心位置偏差相比,使用高时空分辨率的SST能够较为显著地改善"蔷薇"的路径模拟,台风中心位置模拟偏差减少11%,尤其在台风减弱阶段,台风中心位置模拟偏差减少37%。台风强度在台风发展的不同阶段对下垫面SST的变化敏感性不同。台风路径附近的海表面温度下降会导致海洋向大气输送的热量减少从而减弱台风强度。     

海洋表层温度对台风"蔷薇"路径和强度预测精度的影响

基于中尺度大气模式WRF(Weather Research and Forecasting Model),首先对2007年3次船舶辐射通量观测进行模拟,以检验WRF对长波和短波辐射通量的模拟能力,结果表明使用中国近海海洋环境数值预报系统环流模式POM(Princeton Ocean Model)模拟的高时空分辨率的海洋表层温度能够显著改进短波辐射通量的模拟,而对长波辐射通量模拟的改进不明显。然后,将业务化运行的中国近海海洋环境数值预报系统后报的逐时海洋表面温度(SST)作为WRF底边界条件,对2008年15号强台风"蔷薇"(Jangmi)过程进行了数值后报试验。结果表明,与使用NCEP/NCAR的SST试验后报的台风中心位置偏差相比,使用高时空分辨率的SST能够较为显著地改善"蔷薇"的路径模拟,台风中心位置模拟偏差减少11%,尤其在台风减弱阶段,台风中心位置模拟偏差减少37%。台风强度在台风发展的不同阶段对下垫面SST的变化敏感性不同。台风路径附近的海表面温度下降会导致海洋向大气输送的热量减少从而减弱台风强度。     

东海黑潮暖舌对热带气旋“派比安”(1807)强度的影响

通过使用天气研究与预报(Weather Research and Forecasting,WRF)模式对热带气旋(Tropical Cyclone,TC)个例“派比安”(1807)进行了一组数值试验,分析了东海黑潮暖舌对“派比安”强度的影响。研究结果表明,东海黑潮暖舌高海面温度(以下简称“海温”)导致TC区域内海气界面热通量显著增加,并造成TC边界层不稳定特征发展,形成了有利于垂直对流发展的边界层环境。因此TC内特别是TC眼墙处对流更为活跃,TC强度显著提高,同时黑潮暖舌对TC的局部加热还会引起TC内部对流活动的非对称分布。根据数值试验的结果,黑潮暖舌为“派比安”整体动能增加做出约24.7%的贡献,中心气压变化对东海黑潮暖舌高海温特征的响应时间约为10 h。此外,在黑潮暖舌作用下,“派比安”7级风圈半径扩张16.3%,最大风速半径收缩10.7%。     

Assessment of the initial sea surface temperature product of the scanning microwave radiometer aboard on HY-2 satellite

HY-2 satellite is the first satellite for dynamic environmental parameters measurement of China,which was launched on 16th August 2011.A scanning microwave radiometer（RM） is carried for sea surface temperature（SST）,sea surface wind speed,columnar water vapor and columnar cloud liquid water detection.In this paper,the initial SST product of RM was validated with in-situ data of National Data of Buoy Center（NDBC） mooring and Argo buoy.The validation results indicate the accuracy of RM SST is better than 1.7 C.The comparison of RM SST and WindSat SST shows the former is warmer than the latter at high sea surface wind speed and the difference between these SSTs is depend on the sea surface wind speed.Then,the relationship between the errors of RM SST and sea surface wind speed was analyzed using NDBC mooring measurements.Based on the results of assessment and errors analysis,the suggestions of taking account of the affection of sea surface wind speed and using sea surface wind speed and direction derived from the microwave scatteromter aboard on HY-2 for SST product calibration were given for retrieval algorithm improvement.     

一种温度相关的HY-2A散射计地球物理模型函数

利用散射计测量海面后向散射系数, 并通过地球物理模型函数(geophysical model function, GMF)反演得到海面风场。目前散射计风场反演所采用的GMF一般只考虑雷达极化方式、雷达入射角、风速和相对风向对海面后向散射系数的影响, 而相关研究表明海表温度(sea surface temperature, SST)对Ku波段散射计风场反演具有不可忽略的影响。文章利用海洋二号A卫星散射计(Haiyang-2A Scatterometer, HY2A-SCAT)后向散射系数观测值、欧洲中期天气预报中心(European Center for Medium-Range Weather Forecasts, ECMWF )再分析风矢量和SST数据, 采用人工神经网络方法, 建立起一种SST相关的GMF (TNGMF)。对TNGMF进行分析后发现, 海面后向散射系数随着SST的增加而增加, 并且其增加幅度与雷达极化方式、风速有关。为了对比, 文章使用相同数据集和相同方法建立了不包含SST的GMF (NGMF), 将美国国家航天航空局散射计-2 (National Aeronautics and Space Administration Scatterometer-2, NSCAT2) GMF、TNGMF和NGMF分别用于HY2A-SCAT风场反演实验。试验结果表明, 采用NSCAT2 GMF、NGMF反演得到的风速在低温时系统性偏小, 在高温时系统性偏大; 而TNGMF可较好地纠正SST对风速偏差均值的影响, 从而提高反演风场质量。