Assessment of Data Assimilation Approaches for the Simulation of a Monsoon Depression Over the Indian Monsoon Region

A low pressure system that formed on 21 September 2006 over eastern India/Bay of Bengal intensified into a monsoon depression resulting in copious rainfall over north-eastern and central parts of India. Four numerical experiments are performed to examine the performance of assimilation schemes in simulating this monsoon depression using the Fifth Generation Mesoscale Model (MM5). Forecasts from a base simulation (with no data assimilation), a four-dimensional data assimilation (FDDA) system, a simple surface data assimilation (SDA) system coupled with FDDA, and a flux-adjusting SDA system (FASDAS) coupled with FDDA are compared with each other and with observations. The model is initialized with Global Forecast System (GFS) forecast fields starting from 19 September 2006, with assimilation being done for the first 24 hours using conventional observations, sounding and surface data of temperature and moisture from Advanced TIROS Operational Vertical Sounder satellite and surface wind data over the ocean from QuikSCAT. Forecasts are then made from these assimilated states. In general, results indicate that the FASDAS forecast provides more realistic prognostic fields as compared to the other three forecasts. When compared with other forecasts, results indicate that the FASDAS forecast yielded lower root-mean-square (r.m.s.) errors for the pressure field and improved simulations of surface/near-surface temperature, moisture, sensible and latent heat fluxes, and potential vorticity. Heat and moisture budget analyses to assess the simulation of convection revealed that the two forecasts with the surface data assimilation (SDA and FASDAS) are superior to the base and FDDA forecasts. An important conclusion is that, even though monsoon depressions are large synoptic systems, mesoscale features including rainfall are affected by surface processes. Enhanced representation of land-surface processes provides a significant improvement in the model performance even under active monsoon conditions where the synoptic forcings are expected to be dominant.     

Simulation of location-specific severe thunderstorm events using high resolution land data assimilation

In this study, the impact of different land initial conditions on the simulation of thunderstorms and monsoon depressions is investigated using the Weather Research and Forecasting (WRF) model. A control run (CNTL) and a simulation with an improved land state (soil moisture and temperature) using the High Resolution Land Data Assimilation System (HRLDAS, experiment name: EHRLDAS) are compared for three different rainfall cases in order to examine the robustness of the assimilation system. The study comprises two thunderstorm cases (one in the pre-monsoon and one during the monsoon) and one monsoon depression case that occurred during the Interaction of Convective Organisation, Atmosphere, Surface and Sea (INCOMPASS) field campaign of the 2016 Indian monsoon. EHRLDAS is shown to yield improvements in the representation of location-specific rainfall, particularly over land. Further, it is found that surface fluxes as well as convective indices are better captured for the pre-monsoon thunderstorm case in EHRLDAS. By analysing components of the vorticity tendency equation, it is found that the vertical advection term is the major contributor towards the positive vorticity tendency in EHRLDAS compared to CNTL, hence improving localised convection and consequently facilitating rainfall. Significant improvements in the simulation of the pre-monsoon thunderstorm are noted, as seen using Automatic Weather Station (AWS) validation, whereas improvements in the monsoon depression are minimal. Further, it is found that vertical advection (moisture flux convergence) is the major driver modulating the convective circulation in localised thunderstorm (monsoon depression) cases and these dynamics are better represented by EHRLDAS compared to CNTL. These findings underline the importance of accurate and high resolution land-state conditions in model initial conditions for forecasting severe weather systems, particularly the simulation of localised thunderstorms over India.     

Influence of soil moisture on the Sahelian climate prediction II

Summary The sensitivity of short-term climate to soil moisture parameterization has been investigated using the Florida State University Global Spectral Model. This is done through the implementation of a simple and realistic soil moisture availability in a prognostic equation for the surface temperature.The results from two seasonal simulations between 11 May and 31 August 1979 are discussed with an emphasis on the Sahelian regions. These experiments indicated that most of the significant changes that resulted from the new parameterization occurred at and near the surface. Above the surface, land surface effects were strongly diffused and for most of the cases were not conclusively discernible. At the surface, however, soil moisture appeared to be a parameter of large influence. Important modulations in the surface temperature were obtained. The time dependence of the soil moisture availability has led to an evolution of the surface heat sources in the model resulting in an apparent northward propagation of the centers of maximum temperature as the rainfall season progressed over the north African continent from May to August. This has had an important effect on the distribution of the primary variables and showed significant departures from the control.The interaction introduced by the new scheme between the physical processes parameterized in the model, has resulted in a differential modification of the rainfall distribution, and the changes in the hydrological cycle have remarkably affected the summer Sahelian rainfall.With 20 Figures     

初值对中国东部初夏土壤湿度可预报性影响

土壤湿度是影响天气和气候非常重要的因子之一,但目前针对土壤湿度可预报性的研究报道相对较少。该文在对BCC_CSM模式进行了适合的陆面初始化的条件下,设计了两组在中国东部地区采用不同土壤湿度初值的回报试验研究该地区土壤湿度的可预报性及初值对其可预报性影响问题。试验结果表明:BCC_CSM模式在真实的外场强迫下可以模拟出相对合理的土壤湿度;土壤湿度的可预报性在表层约为3候,随着深度的增加,土壤湿度的可预报性持续时间增加,在中层预报性甚至能达到月尺度以上;初值对于土壤湿度的预报存在影响,在表层影响时间约为2~3候,影响时间随着深度增加;浅层土壤湿度受降水的影响较大,浅层土壤湿度变化滞后降水变化约1~2 d,中层土壤湿度变化与降水变化存在5 d左右的滞后关系。     

“威马逊”（1409）强降水物理过程模拟诊断研究

利用WRF模式,结合三维降水诊断方程和降水效率定义,针对1409号超强台风“威马逊”临岸迅速加强为超强台风并登陆我国华南沿海这一时段的强降水物理过程开展了高分辨率数值模拟诊断研究。结果表明,“威马逊”主体环流区域内一直维持很强的平均降水强度（P_S）,陆地和海洋P_S的相对贡献基本呈反向变化,登陆期间陆面摩擦辐合增强,有利于水汽更多地向陆地区域辐合（Q_WVA代表垂直积分的三维水汽通量辐合/辐散率,此时段Q_WVA为正值）,造成登陆前短时段内陆地上空局地大气增湿（Q_WVL代表垂直积分的水汽局地变化率的负值,此时段Q _WVL为负值）,借助云微物理过程快速转化为液相和固相云水凝物（Q_CLL和Q_CIL分别代表垂直积分的液相和固相云水凝物局地变化率的负值,此时段Q_CLL和Q_CIL为负值）,促使陆地上空降水云系快速发展和降水强度增强,而当环流中心位于北部湾洋面时,海洋Q_WVA的相对贡献显著增强,登陆期间下垫面的变化导致水汽相关物理过程明显变化,进而造成降水云系和强降水中心的显著变化;与陆地相比,海洋表面蒸发的作用更强,变化更明显;“威马逊”影响华南沿海期间,主体环流圈内平均的Q_CLL和Q_CIL均基本呈现“正—负—正”的变化特征,当环流中心位于北部湾洋面（三次登陆时期）时水凝物含量以增加（减少）为主;“威马逊”主体环流区域内一直维持高降水效率,从主体环流圈接触陆地开始,陆地降水效率迅速升高,而海洋降水效率在绝大多数积分时段内维持较高数值,只在第二和第三次登陆后有所降低。     

应用WRF模式对江西一次暴雨过程的模拟分析

利用新一代数值预报模式WRF耦合RUC、NOAH两个陆面过程,对2006年4月11-12日发生在江西境内的一次暴雨过程进行模拟,并对模式输出的水文平衡和能量,尤其是土壤湿度、地表径流、土壤温度等的变化进行了分析.结果显示,WRF模式耦合两个陆面过程均能模拟出此次暴雨过程的降水空间、时间分布和强度,而WRF-RUC提供了...     

WRF耦合4个陆面过程对“6.19”暴雨过程的模拟研

利用WRF模式与4个陆面过程的耦合,对2010年6月19—20日的暴雨过程进行了数值模拟,并分析陆面过程对暴雨强度和范围的敏感性。结果显示：WRF耦合4个陆面过程模拟的雨带和实况分布一致,均为东西向的雨带形状,且均预报出与实况资料相似的强降水中心。在无陆面方案情况下,强降水中心的位置、范围、强度等都发生明显变化。另外地表径流预报量和降水趋势表现一致,由于土壤含水量趋于饱和,多余的降水分配给地表径流,这种剧增的地表径流也是洪水暴涨、水位上升的重要原因。在较湿的土壤状况下,由于净辐射增长,有利于产生厚度更小的边界层高度以及更大的地表向上潜热通量,这也是导致本次降水过程异常增幅的一个重要原因。     

Mechanisms for the land/sea warming contrast exhibited by simulations of climate change

The land/sea warming contrast is a phenomenon of both equilibrium and transient simulations of climate change: large areas of the land surface at most latitudes undergo temperature changes whose amplitude is more than those of the surrounding oceans. Using idealised GCM experiments with perturbed SSTs, we show that the land/sea contrast in equilibrium simulations is associated with local feedbacks and the hydrological cycle over land, rather than with externally imposed radiative forcing. This mechanism also explains a large component of the land/sea contrast in transient simulations as well. We propose a conceptual model with three elements: (1) there is a spatially variable level in the lower troposphere at which temperature change is the same over land and sea; (2) the dependence of lapse rate on moisture and temperature causes different changes in lapse rate upon warming over land and sea, and hence a surface land/sea temperature contrast; (3) moisture convergence over land predominantly takes place at levels significantly colder than the surface; wherever moisture supply over land is limited, the increase of evaporation over land upon warming is limited, reducing the relative humidity in the boundary layer over land, and hence also enhancing the land/sea contrast. The non-linearity of the Clausius–Clapeyron relationship of saturation specific humidity to temperature is critical in (2) and (3). We examine the sensitivity of the land/sea contrast to model representations of different physical processes using a large ensemble of climate model integrations with perturbed parameters, and find that it is most sensitive to representation of large-scale cloud and stomatal closure. We discuss our results in the context of high-resolution and Earth-system modelling of climate change.     

Surface rainfall and cloud budgets associated with mei-yu torrential rainfall over eastern China during June 2011

Surface rainfall and cloud budgets associated with three heavy rainfall events that occurred over eastern China during the mei-yu season in June 2011 were analyzed using 2D cumulus ensemble model simulation data.Model domain mean rainfall showed three peaks in response to three prescribed ascending motion maxima,primarily through the mean moisture convergence during the torrential rainfall period.Prescribed ascending motion throughout the troposphere produced strong convective rainfall during the first （9 June） and third （17-18 June） rainfall events,whereas strong prescribed ascending motion in the mid and upper troposphere and weak subsidence near the surface generated equally important stratiform and convective rainfall during the second rainfall event （14 June）.The analysis of surface rainfall budgets reveals that convective rainfall was associated with atmospheric drying during the first event and moisture convergence during the third event.Both stratiform and convective rainfall responded primarily to moisture convergence during the second event.An analysis of grid data shows that the first and third mean rainfall maxima had smaller horizontal scales of the precipitation system than the second.     

The influence of surface roughness of deserts on the July circulation

The influence of low surface roughness of deserts on the July circulation is examined by employing numerical simulations with a GLAS GCM. Two identical sets of simulations were made with the model starting from the initial state of the atmosphere based on the NMC analysis of observations for June 15, at OOZ for the years 1979 and 1980. The first set, called the Control, had land surface roughness set to 45 cm, everywhere. The second set called the Experiment, had surface roughness set to 0.02 cm for deserts, but 45 cm everywhere else on land. All other prescribed boundary conditions were the same in both runs.A comparative analysis of these simulations showed that the rainfall in the Sahara desert was reduced significantly in both Experiments as compared to the corresponding Controls; the ITCZ (inter-tropical convergence zone) moved southward, to about 14° N, which is close to its observed location at about 10° N. This was primarily caused by the relative moisture divergence from the smoother Sahara. In other deserts, which anyway had little rainfall in the July simulation of the Control run, there was virtually no change. The differences in regional heat and moisture budgets, particularly for the Sahara desert, are significant as compared to the sample standard deviation for a set of three July simulations (i.e., Control runs for three different initial conditions). In a third simulation, in which the surface roughness was changed over all land, similar results were obtained in the Sahara desert region.The study reveals the influence of low surface-roughness of deserts on the July rainfall. For the Sahara desert, this influence is comparable to that of an increase in surface albedo. In nature, formation of deserts leads to reduction of surface roughness as the vegetation perishes and soil erosion ensues. It is inferred that the smoothness of land then causes reduction in rainfall and further promotes desertification.Sigma Data Services through contract # NASA 25900.     

CORRELATION BETWEEN PEAK INTENSITY OF EXTREME AFTERNOON SHORT-DURATION RAINFALL AND HUMIDITY AND SURFACE AIR TEMPERATURE IN SOUTHEAST COAST OF CHINA

Using hourly rainfall intensity, daily surface air temperature, humidity and low-level dew point depressions at 55 stations in the southeast coast of China, and sea surface temperature from reanalysis in the coastal region, this paper analyzes the connection between peak intensity of extreme afternoon short-duration rainfall (EASR) and humidity as well as surface air temperature. The dependency of extreme peak intensity of EASR on temperature has a significant transition. When daily highest surface temperature is below (above) 29°C, the peak rainfall intensity shows an ascending (descending) tendency with rising temperature. Having investigated the role of moisture condition in the variation of EASR and temperature, this paper discovered that the decrease of peak rainfall intensity with temperature rising is connected with the variation of relative humidity. At higher temperatures, the land surface relative humidity decreases dramatically as temperature further increases. During this process, the sea surface temperature maintains basically unchanged, resulting in indistinct variations of water vapor content at seas. As water vapor over land is mainly contributed by the quantitative moisture transport from adjacent seas, the decline of relative humidity over land will be consequently caused by the further rise of surface air temperature.     

Atmosphere-land surface interactions and their influence on extreme rainfall and potential abrupt climate change over southern Africa

In a changing climate, changes in rainfall variability and, in particular, extreme rainfall events are likely to be highly significant for environmentally vulnerable regions such as southern Africa. It is generally accepted that sea-surface temperatures play an important role in modulating rainfall variability, thus the majority work to date has focused on these mechanisms. However past research suggests that land surface processes are also critical for rainfall variability. In particular, work has suggested that the atmosphere-land surface feedback has been important for past abrupt climate changes, such as those which occurred over the Sahara during the mid-Holocene or, more recently, the prolonged Sahelian drought. Therefore the primary aim of this work is to undertake idealised experiments using both a regional and global climate model, to test the sensitivity of rainfall variability to land surface changes over a location where such abrupt climate changes are projected to occur in the future, namely southern Africa. In one experiment, the desert conditions currently observed over southwestern Africa were extended to cover the entire subcontinent. This is based on past research which suggests a remobilisation of sand dune activity and spatial extent under various scenarios of future anthropogenic global warming. In the second experiment, savanna conditions were imposed over all of southern Africa, representing an increase in vegetation for most areas except the equatorial regions. The results suggest that a decrease in rainfall occurs in the desert run, up to 27% of total rainfall in the regional model (relative to the control), due to a reduction in available moisture, less evaporation, less vertical uplift and therefore higher near surface pressure. This result is consistent across both the regional and global model experiments. Conversely an increase in rainfall occurs in the savanna run, because of an increase in available moisture giving an increase in latent heat and therefore surface temperature, increasing vertical uplift and lowering near surface pressure. These experiments, however, are only preliminary, and form the first stage of a wider study into how the atmosphere-land surface feedback influences rainfall extremes over southern Africa in the past (when surface i.e. vegetation conditions were very different) and in the future under various scenarios of future climate change. Future work will examine how other climate models simulate the atmosphere-land surface feedback, using more realistic vegetation types based on past and future surface conditions.     

Validating a regional climate model’s downscaling ability for East Asian summer monsoonal interannual variability

Performance of a regional climate model (RCM), WRF, for downscaling East Asian summer season climate is investigated based on 11-summer integrations associated with different climate conditions with reanalysis data as the lateral boundary conditions. It is found that while the RCM is essentially unable to improve large-scale circulation patterns in the upper troposphere for most years, it is able to simulate better lower-level meridional moisture transport in the East Asian summer monsoon. For precipitation downscaling, the RCM produces more realistic magnitude of the interannual variation in most areas of East Asia than that in the reanalysis. Furthermore, the RCM significantly improves the spatial pattern of summer rainfall over dry inland areas and mountainous areas, such as Mongolia and the Tibetan Plateau. Meanwhile, it reduces the wet bias over southeast China. Over Mongolia, however, the performance of precipitation downscaling strongly depends on the year: the WRF is skillful for normal and wet years, but not for dry years, which suggests that land surface processes play an important role in downscaling ability. Over the dry area of North China, the WRF shows the worst performance. Additional sensitivity experiments testing land effects in downscaling suggest the initial soil moisture condition and representation of land surface processes with different schemes are sources of uncertainty for precipitation downscaling. Correction of initial soil moisture using the climatology dataset from GSWP-2 is a useful approach to robustly reducing wet bias in inland areas as well as to improve spatial distribution of precipitation. Despite the improvement on RCM downscaling, regional analyses reveal that accurate simulation of precipitation over East China, where the precipitation pattern is strongly influenced by the activity of the Meiyu/Baiu rainfall band, is difficult. Since the location of the rainfall band is closely associated with both lower-level meridional moisture transport and upper-level circulation structures, it is necessary to have realistic upper-air circulation patterns in the RCM as well as lower-level moisture transport in order to improve the circulation-associated convective rainfall band in East Asia.     

Impact of moisture flux convergence and soil moisture on precipitation: a case study for the southern United States with implications for the globe

Interactions between soil moisture, evapotranspiration (ET), atmospheric moisture fluxes and precipitation are complex. It is difficult to attribute the variations of one variable to another. In this study, we investigate the influence of atmospheric moisture fluxes and land surface soil moisture on local precipitation, with a focus on the southern United States (U.S.), a region with a strong humidity gradient and intense moisture fluxes. Experiments with the Weather Research and Forecasting model show that the variation of moisture flux convergence (MFC) is more important than that of soil moisture for precipitation variation over the southern U.S. Further analyses decompose the precipitation change into several contributing factors and show that MFC affects precipitation both directly through changing moisture inflow (wet areas) and indirectly by changing the precipitation efficiency (transitional zones). Soil moisture affects precipitation mainly by changing the precipitation efficiency, and secondly through direct surface ET contribution. The greatest soil moisture effects are over transitional zones. MFC is more important for the probability of heavier rainfall; soil moisture has much weaker impact on rainfall probability and its roles are similar for the probability of intermediate-to-heavy rainfall (>10 mm day^?1). Although MFC is more important than soil moisture for precipitation over most regions, the impact of soil moisture could be large over certain transitional regions. At the submonthly time scale, the African Sahel appears to be the only major region where soil moisture has a greater impact than MFC on precipitation. This study provides guidance to understanding and further investigation of the roles of local land surface processes and large-scale circulations on precipitation.     

A numerical simulation of the surface water budget during HAPEX-MOBILHY

A simple land surface parameterization scheme previously validated at the daily time scale is studied for monthly periods using the HAPEX-MOBILHY data set. For a set of six locations, the scheme reproduces with good accuracy two components of the surface water budget (evaporation and soil moisture depletion) when the observed rainfall rate at the ground surface is specified. For two sites where the superficial soil moisture content has been measured, the model provides a reasonable evolution for this quantity. The validation has been completed by examining the screen-level temperature and relative humidity. The agreement with observations is fair, except when the local properties of the site strongly differ from those of the surroundings.     

Short timescale air-sea coupling in the tropical deep convective regime

Summary The relationship between surface rainfall rate and sea-surface temperature (SST) over tropical cloudy areas is revisited, and associated air-sea interaction processes are investigated based on hourly grid simulation data over cloudy areas from a two-dimensional coupled ocean-cloud resolving atmosphere model. A cloud-weighted data analysis shows that surface evaporation flux decreases with increasing SST and is one order of magnitude smaller than the residual between moisture convergence and condensation, playing a negligible role in moisture budget. Moisture convergence determines the surface rainfall rate by determining vapor condensation and deposition rates. Ocean mixed-layer thermal budget shows that the atmospheric surface flux is a major process responsible for SST variation while thermal advection and thermal entrainment play a secondary role. The results indicate that atmospheric impacts on the ocean are important whereas oceanic impacts on the atmosphere are not, in the tropical air-sea system, on short timescales. Thus, the relationship between surface rainfall rate and SST over tropical cloudy areas is not physically important. Further estimates indicate that the surface evaporation flux and residual between moisture convergence and condensation could have the same order of magnitude in daily-mean moisture budget.     

陆面过程模式中地下水位的参数化及初步应用

田间研究表明地表水和地下水有重要的相互作用,它与土壤含水量密切相关.土壤含水量不仅在陆气相互作用系统水和能量平衡中,而且在干旱、洪水预报、水资源管理、生态系统研究中起十分重要的作用.因此,研究地表水和地下水的相互作用,建立陆面模式中地下水位的动态表示,对于气候与水资源研究具有重要意义.将地下水位的动态表示问题归结为饱和与非饱和流问题,发展了其数值计算方案,建立了地下水位的动态表示,并与陆面过程模型耦合,建立了陆气相互作用中地下水位的动态表示,并进行了数值模拟研究.     

Effect of Length Scale Tuning of Background Error in WRF-3DVAR System on Assimilation of High-Resolution Surface Data for Heavy Rainfall Simulation

We investigated the impact of tuning the length scale of the background error covariance in the Weather Research and Forecasting(WRF) three-dimensional variational assimilation(3DVAR) system.In particular,we studied the effect of this parameter on the assimilation of high-resolution surface data for heavy rainfall forecasts associated with mesoscale convective systems over the Korean Peninsula.In the assimilation of high-resolution surface data,the National Meteorological Center method tended to exaggerate the length scale that determined the shape and extent to which observed information spreads out.In this study,we used the difference between observation and background data to tune the length scale in the assimilation of high-resolution surface data.The resulting assimilation clearly showed that the analysis with the tuned length scale was able to reproduce the small-scale features of the ideal field effectively.We also investigated the effect of a double-iteration method with two different length scales,representing large and small-length scales in the WRF-3DVAR.This method reflected the large and small-scale features of observed information in the model fields.The quantitative accuracy of the precipitation forecast using this double iteration with two different length scales for heavy rainfall was high;results were in good agreement with observations in terms of the maximum rainfall amount and equitable threat scores.The improved forecast in the experiment resulted from the development of well-identified mesoscale convective systems by intensified low-level winds and their consequent convergence near the rainfall area.     

Role of the global oceans and land–atmosphere interaction on summertime interdecadal variability over northern Argentina

This study uses experiments with an atmospheric general circulation model (AGCM) to address the role of the oceans and the effect of land–atmosphere coupling on the predictability of summertime rainfall over northern Argentina focusing on interdecadal time scales during 1901–2006. Ensembles of experiments where the AGCM is forced with historical sea surface temperature (SST) in the global, Pacific and tropical-North Atlantic domains are used. The role of land–atmosphere interaction is assessed comparing the output of simulations with active and climatological soil moisture. A maximum covariance analysis between precipitation and SST reveals the impact of the Pacific Decadal Oscillation, the Atlantic Multidecadal Oscillation and the equatorial–tropical South Atlantic on rainfall over northern Argentina. Model simulations further show that while the dominant influence comes from the Pacific basin, the Atlantic influence can explain a large transition from dry to wet decades over northern Argentina during the beginning of the 1970s. Analysis of anomalies before and after the transition reveals an upper level anticyclonic circulation off the Patagonian coast with barotropic structure. This circulation enhances the moisture transport and convergence in northern Argentina and, together with enhanced evaporation, increased the rainfall after 1970. The SST pattern is dominated by cold conditions in the equatorial Atlantic and warm eastern Pacific and South Atlantic. We also found that land–atmosphere interaction leads to a representation of the long term rainfall evolution over northern Argentina that is closer to the observed one. Moreover, it leads to a smaller dispersion among ensemble members, thus resulting in a larger signal-to-noise ratio.     

The role of the land surface processes in the rainfall generated by a landfall typhoon: A simulation of the typhoon Sepat (2007)

Landfall tropical cyclones are a major kind of severe weather affecting China. The typhoon Sepat, declassified as tropical storm after its landfalling, caused a continuous heavy rainfall event over China mainland from 19th to 25th August, 2007. The storm cyclone resided over the Hunan province for 60 hours, causing observed accumulated precipitation larger than 300 mm in a large area of the Hunan province and leading severe flood events. This event was simulated using the Weather Research and Forecasting (WRF) model coupled with the surface layer scheme UTOPIA. The model was able to reproduce the main characteristics of the event, including the typhoon track and the rainfall field and timing. In addition, three sets of sensitivity experiments have been performed. In the first one, the effects of different land surface schemes (RUC, NOAH and UTOPIA) coupled with WRF on the precipitation, sensible and latent heat flux fields associated with the Typhoon Sepat (2007) were investigated. The second set of sensitivity experiments analyzed the role of the surface fluxes (sensible and latent heat flux) on the typhoon evolution. The third set of sensitivity experiments regarded the initialization of the soil moisture content. These experiments showed that both latent and sensible heat fluxes sustained this landfalling typhoon, maintaining the spiral structure of rain belt. Among the two fluxes, the latent heat one played a major role in determining the intensity, the track and the rainfall distribution of the typhoon. In addition, the correct initialization of the soil moisture content has reveled a fundamental parameter to be initialized in order to correctly evaluate the distribution and intensity of the rain field. The intercomparison between the three different land surface schemes coupled with WRF showed that the WRF-UTOPIA and WRF-NOAH outputs seem comparable between each other and physically most realistic than those of WRF-RUC. These analyses were helpful to understand the evolution and the development of the landfalling typhoon, and demonstrated that WRF-UTOPIA and WRF-NOAH could be considered a good tool for managing the risk evaluation connected with the occurrence of such events at regional scale.