The Impact Cooling of the Storm-Induced SST on Hurricane Intensity     

Tong ZHU Da-Lin ZHANG 《大气科学进展》2006,23(1):14-22

The effects of storm-induced sea surface temperature （SST） cooling on hurricane intensity are investigated using a 5-day cloud-resolving simulation of Hurricane Bonnie （1998）. Two sensitivity simulations are performed in which the storm-induced cooling is either ignored or shifted close to the modeled storm track. Results show marked sensitivity of the model-simulated storm intensity to the magnitude and relative position with respect to the hurricane track. It is shown that incorporation of the storm-induced cooling, with an average value of 1.3℃, causes a 25-hPa weakening of the hurricane, which is about 20 hPa per 1℃ change in SST. Shifting the SST cooling close to the storm track generates the weakest storm, accounting for about 47% reduction in the storm intensity. It is found that the storm intensity changes are well correlated with the air-sea temperature difference. The results have important implications for the use of coupled hurricane-ocean models for numerical prediction of tropical cyclones.  相似文献   

Role of land-surface temperature feedback on model performance for the stable boundary layer     

A. A. M. Holtslag  G. J. Steeneveld  B. J. H. van de Wiel 《Boundary-Layer Meteorology》2007,125(2):361-376

At present a variety of boundary-layer schemes is in use in numerical models and often a large variation of model results is found. This is clear from model intercomparisons, such as organized within the GEWEX Atmospheric Boundary Layer Study (GABLS). In this paper we analyze how the specification of the land-surface temperature affects the results of a boundary-layer scheme, in particular for stable conditions. As such we use a well established column model of the boundary layer and we vary relevant parameters in the turbulence scheme for stable conditions. By doing so, we can reproduce the outcome for a variety of boundary-layer models. This is illustrated with the original set-up of the second GABLS intercomparison study using prescribed geostrophic winds and land-surface temperatures as inspired by (but not identical to) observations of CASES-99 for a period of more than two diurnal cycles. The model runs are repeated using a surface temperature that is calculated with a simple land-surface scheme. In the latter case, it is found that the range of model results in stable conditions is reduced for the sensible heat fluxes, and the profiles of potential temperature and wind speed. However, in the latter case the modelled surface temperatures are rather different than with the original set-up, which also impacts on near-surface air temperature and wind speed. As such it appears that the model results in stable conditions are strongly influenced by non-linear feedbacks in which the magnitude of the geostrophic wind speed and the related land-surface temperature play an important role.  相似文献   

速度传感反馈地震计的动态范围上限     

饶文松  杨晓源 《地震地磁观测与研究》2007,28(5):63-70

在开环参数一定的条件下,速度传感反馈地震计中的环路滤波是影响地震计主要技术指标的关键环节之一.本文探讨了一阶极点高通、一阶极点低通、一阶零点高通、双一阶和零阶环路滤波在扩展地震计动态范围上限方面的优缺点.研究指出,对于用闭环反馈直接生成主导二阶极点的速度传感反馈地震计,一阶零点高通环路滤波的优点较多;若允许在环外生成主导二阶极点,则零阶环路滤波也不失为一个较好的方案.  相似文献   

Mass flows and river response in rapid uplifting regions – A case of lower Yarlung Tsangpo basin,southeast Tibet,China   总被引：1，自引：0，他引：1  

《国际泥沙研究》2020,35(6):609-620

The fluvial geomorphology in tectonically active (particularly rapid uplift) regions often undergoes continuous change. The rapid uplift is coincident with high erosion rates; consequently, incised valleys are formed. Mass flows (for example, avalanches, landslides, and debris flows) in incised valleys can markedly influence fluvial processes and even reshape valley geomorphology. However, these processes and long-term evolution corresponding to mass flows require further clarification. Field campaigns were carried out in the region near the Yigong Tsangpo and Palong Tsangpo Rivers (hereafter the Yigong and Palong Rivers), the two largest tributaries of the lower Yarlung Tsangpo River, to examine the feedback between fluvial processes and mass flows. Remote sensing images from recent decades were used to compare the channel morphology before and after typical mass flows (particularly catastrophic ones). The morphology of the lower Yigong River has evidently been impacted by landslides, while that of the Palong River has mainly been shaped by glacial processes and debris flows. At present, the morphology of the latter consists of alternating sections of gorges and wide valleys, with a staircase-like longitudinal profile. The gorge sections exhibit single and deeply incised channels with a high-gradient channel bed and terraces. In contrast, the wide valley sections consist of lakes, braided or anabranching channels, gentle bed gradients, and thick alluvial deposits. Debris flows occur more frequently in gullies in the reaches of the gorge sections and rarely in gullies along the wide valley sections. The occurrence of mass flow events has resulted in an imbalance of the previous (quasi-)equilibrium in the river morphology; however, this has triggered negative feedback that is driving the transient river morphology to a new state of (quasi-)equilibrium.  相似文献   

Using the TCEV distribution function with systematic and non-systematic data in a regional flood frequency analysis     

F. Francés 《Stochastic Hydrology and Hydraulics》1998,12(4):267-283

Due to the social and economic implications, flood frequency analysis must be done with the highest precision. For this reason, the most suitable statistical model must be selected, and the maximum amount of information must be used. Floods in Mediterranean rivers can be produced by two different mechanisms, which forces the use of a non-traditional distribution like the TCEV. The information can be increased by using additional non-systematic data, or with a regional analysis, or both. Through the statistical gain concept, it has been shown that in most cases the use of additional non-systematic information can decrease the quantile estimation error in about 50%. In a regional analysis, the␣benefit of additional information in one station, is propagated to the rest of␣the␣stations with only a small decrease with respect to the at-site equivalent analysis.  相似文献   

气候系统及模式中反馈机制研究 I.概念和方法     

林朝晖  曾庆存 《气候与环境研究》1998,(1)

气候系统中存在着各种各样的气候反馈机制,而气候模式对这些反馈机制描述的差异,正是造成不同模式对同一直接辐射强迫（如二氧化碳加倍）的响应不同的主要原因。因此,只有正确描述气候系统中的各种反馈作用,气候模式才可能用来对未来的气候变化进行预测。为此,本文首先介绍了气候系统及模式反馈机制分析研究时所常用的一些概念,如气候敏感性参数、云辐射强迫等,随后概述了气候模式反馈机制比较分析时常用的各种方法,并指出了这些方法各自的优缺点。而详细的有关气候系统及模式中反馈作用及其机制的分析则在文章的第ＩＩ部分给出。  相似文献   

迭代逼近科学方法在速度估算中的作用     

陈宝孚  李貅 《地球科学与环境学报》2000,22(2):67-70

以地球物理中的速度为题 ,在详细描述了速度参数重要作用、各类速度基本概念及其应用范围、影响速度估算的各种因素的基础上 ,以模型和处理流程的叠加速度分析为例 ,在两个层面上展现了迭代逼近方法。又以剩余层速度分析为例 ,说明了具有反馈控制思想的迭代逼近算法 ,从而指出该方法在速度估算中的重要作用  相似文献   

一种实用的铂热电阻温度巡检仪     

龚一光  杨家仕 《成都信息工程学院学报》2000,15(2):131-135

介绍了一种经济实用的 16通道铂热电阻测温巡检显示仪 ,并论述了铂热电阻的引线消除和用正反馈实现非线性校正的方法。  相似文献   

南汇东滩沉积物粒度特征及其与水动力的关系   总被引：2，自引：0，他引：2  

黄广  陈沈良  胡静 《海洋湖沼通报》2008,(1):32-38

沉积物粒度参数可以用来反演沉积物沉积的水动力条件和沉积环境。根据对南汇边滩采集的表层沉积物粒度资料进行分析,结果表明:沉积物类型以黏土质粉砂为主;随着沉积物平均粒径Mz的减小,分选逐渐变好,偏态由极正偏向正偏转变,并向近对称接近。运用Pe- jurp的三角图式对沉积环境进行划分,结果表明南汇东滩的水动力条件总体上较强,沉积物粒径总体上偏粗,属于径流—潮流共同作用的河口浅滩沉积环境。对潮流底应力和沉积物临界起动切应力的计算进一步印证了该区水动力较强,对应沉积物颗粒偏粗的现象。  相似文献   

Quantitative analysis of the feedback induced by the freshwater flux in the tropical Pacific using CMIP5     

Hai Zhi  Rong-Hua Zhang  Pengfei Lin  Lanning Wang 《大气科学进展》2015,32(10):1341-1353

Freshwater flux (FWF) directly affects sea surface salinity (SSS) and hence modulates sea surface temperature (SST) in the tropical Pacific. This paper quantifies a positive correlation between FWF and SST using observations and simulations of the fifth phase of the Coupled Model Intercomparison Project (CMIP5) to analyze the interannual variability in the tropical Pacific. Comparisons among the displacements of FWF, SSS and SST interannual variabilities illustrate that a large FWF variability is located in the west-central equatorial Pacific, covarying with a large SSS variability, whereas a large SST variability is located in the eastern equatorial Pacific. Most CMIP5 models can reproduce the fact that FWF leads to positive feedback to SST through an SSS anomaly as observed. However, the difference in each model's performance results from different simulation capabilities of the CMIP5 models in the magnitudes and positions of the interannual variabilities, including the mixed layer depth and the buoyancy flux in the equatorial Pacific. SSS anomalies simulated from the CMIP5 multi-model are sensitive to FWF interannual anomalies, which can lead to differences in feedback to interannual SST variabilities. The relationships among the FWF, SSS and SST interannual variabilities can be derived using linear quantitative measures from observations and the CMIP5 multi-model simulations. A 1 mm d-1 FWF anomaly corresponds to an SSS anomaly of nearly 0.12 psu in the western tropical Pacific and a 0.11°C SST anomaly in the eastern tropical Pacific.  相似文献