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1.
The default green vegetation fraction (GVF) in the Weather Research and Forecasting (WRF) Model version 3.7.1 was derived between 1985 and 1990 from the 1990s Normalized Difference Vegetation Index (NDVI) achieved from the NOAA Advanced Very High Resolution Radiometer (AVHRR), and its representation is deteriorating when used to simulate recent weather and climate events. In this study, we applied in WRF v3.7.1 the updated GVF estimated by the real-time NDVI of the Moderate Resolution Imaging Spectroradiometer (MODIS) data to provide a better representation of the prescribed surface GVF condition. A one-year simulation was carried out in China, and the simulated 2-m air temperature and specific humidity were compared between the WRF model control experiment that employs the default GVF data (WRF-CTL), the WRF simulations with updated GVF (WRF-MODIS), and the observations from 824 weather stations in China. Results are significantly improved for both the 2-m air temperature and the specific humidity by WRF-MODIS, which has effectively reproduced the observed pattern and increased the correlation coefficient between the model simulations and observations. The RMSE and bias of specific humidity are also reduced in WRF-MODIS. In general, the real-time MODIS-NDVI based GVF reflected the realistic increase of vegetation cover in China when comparing to the WRF default GVF, and also provided a more accurate seasonal variation for the simulated year of 2009. As a result, the WRF-MODIS simulation significantly improves its representation in the simulated 2-m air temperature and specific humidity, both in spatial distributions and seasonal variations, due to the GVF’s great contribution in modulating the coupled land-atmosphere interactions. 相似文献
2.
F. Chen 《Climate Dynamics》2005,24(7-8):667-684
The International Satellite Land-Surface Climatology Project (ISLSCP) Initiative-I 1-degree 1987–1988 data were used to drive
a land surface model (LSM) to simulate global surface energy budgets. Simulated surface heat fluxes show remarkable spatial
variability and seem to capture well their annual and interannual variability. A shift of maximum evaporation across the equator
is more closely related to the seasonal shifting of precipitation pattern than to surface radiation changes. The NCEP/NCAR
reanalysis did not reflect this shift, presumably due to its dominant rainfall maximum in the Southern Hemisphere. To assess
the “reliability” of these fields, both Global Soil Wetness Project (GSWP) and reanalysis were verified against observations,
at two sites. Monthly mean ISLSCP forcing conditions agree fairly well with observations, but its precipitation is usually
lower during spring and summer. Low summer GSWP evaporation may be due to low precipitation and incorrect specification of
vegetation and soil conditions. The reanalysis had larger seasonal variability than GSWP and observations, and overestimated
summer heat fluxes because of its large rainfall and surface radiation. Despite uncertainty in ISLSCP data, an LSM with a
modest treatment of vegetation was able to capture reasonably well the seasonal variations in surface heat fluxes at global
scales. With some caution, these types of simulations can be used as “pseudo-observations” to evaluate climate-model simulations
and to investigate global energy budgets. For the next phase of ISLSCP data development, higher resolution data, which can
reflect local heterogeneity of vegetation and soil characteristics, include more rain gauge data are highly desirable to improve
model simulations. 相似文献
3.
复杂地形区陆面资料对WRF模式模拟性能的影响 总被引：2，自引：0，他引：2
本文利用WRF（Weather Research and Forecasting）模式耦合Noah陆面过程模式,对比研究了使用不同精度陆面资料:WRF默认陆面资料、中国1 km分辨率数字高程模型数据集、2006年MODIS（MODerate-resolution Imaging Spectroradiometer）土地利用和植被覆盖度资料,WRF模式对兰州地区冬季气象场模拟结果的差异。结果表明,近地面气温对陆面资料的精度非常敏感,而风场对陆面资料的精度不敏感,WRF模式对气温的模拟效果好于对风场模拟。采用高精度且时效性好的陆面资料后,WRF模拟的近地面气温准确率提高了15.8%,模拟的夜间气温改进幅度较白天大。陆面资料可影响整个边界层温度场分布,准确的陆面资料对提高WRF模式模拟近地面乃至整个边界层气象场至关重要。尽管风速模拟误差较大,但总体上WRF模式能较准确地模拟出研究区的风场演变特征。使用新的陆面资料后WRF模拟的风速误差略有减小,风向误差略有增加。干旱半干旱区冬季数值模拟需要注意土壤湿度初值和模式初始积分时刻对模拟结果的影响。 相似文献
4.
Evaluation of the WRF Model with Different Land Surface Schemes： A Drought Event Simulation in Southwest China during 2009–10 
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下载免费PDF全文 The authors examined the performance of version 3.4.1 of the Weather Research and Forecasting Model（WRF） with various land surface schemes in simulating a severe drought event in Southwest China. Five numerical experiments were completed using the Noah land surface scheme, the Pleim-Xiu land surface scheme, the Noah-MP land surface schemes, the Noah- MP scheme with dynamic vegetation, and the Noah-MP scheme with dynamic vegetation and groundwater processes. In general, all the simulations reasonably reproduced the spatial and temporal variations in precipitation, but significant bias was also found, especially for the spatial pattern of simulated precipitation. The WRF simulations with the Noah-MP series land surface schemes performed slightly better than the WRF simulation with the Noah and Pleim-Xiu land surface schemes in reproducing the severe drought events in Southwest China. The leaf area index（LAI） simulated by the different land surface schemes showed significant deviations in Southwest China. The Pleim-Xiu scheme overestimated the value of LAI by a factor of two. The Noah-MP scheme with dynamical vegetation overestimated the magnitude of the annual cycle of the LAI, although the annual mean LAI was close to observations. The simulated LAI showed a long-term lower value from autumn 2009 to spring 2010 relative to normal years. This indicates that the LAI is a potential indictor to monitor drought events. 相似文献
5.
夏季我国干旱、半干旱区陆面过程能量平衡及其局地大气环流 总被引：28，自引：10，他引：18
利用NCEP资料分析得出,夏季我国干旱,半干旱区在整个欧亚大陆上是陆面感热通量最强的地方,与此对应的陆面潜热通量则最弱.陆面所接收的太阳短波辐射主要以感热和长波辐射的能量形式释放.该区降水量很少,降水量的年际变率也很弱;因此,该区的陆面热量通量都显出很弱的年际变率;然而,这些通量的年代际变率信号则比较显著.我国干旱、半干旱区大气环流的热力过程与其陆面过程特征密切相关.该区对流层大气的辐射冷却很强,达-3 K d-1.由于缺乏水汽和上升运动,大尺度凝结加热率、深对流加热率、浅对流加热率都非常弱.因此,600hPa以上的大气以绝热下沉加热来平衡辐射冷却;600hPa以下,陆面感热引起的垂直扩散加热率非常强,多达8 K d-1,它除了平衡辐射冷却以外还制造对流层低层的对流运动,以绝热上升冷却来平衡多余的垂直扩散加热.总之,我国干旱、半干旱区的陆面过程特征决定了该区大气运动的特殊垂直结构,即对流层低层对流上升运动及其上层的下沉运动.我国干旱、半干旱区陆面能量平衡及其局地大气环流的年代际变率,是全球气候系统年代际变率的必然结果. 相似文献
6.
Numerical simulation of the impact of vegetation index on the interannual variation of summer precipitation in the Yellow River Basin 总被引：1，自引：0，他引：1
Two sets of numerical experiments using the coupled National Center for Environmental Prediction General Circulation Model （NCEP/GCM T42L18） and the Simplified Simple Biosphere land surface scheme （SSiB） were carried out to investigate the climate impacts of fractional vegetation cover （FVC） and leaf area index （LAI） on East Asia summer precipitation, especially in the Yellow River Basin （YRB）. One set employed prescribed FVC and LAI which have no interannual variations based on the climatology of vegetation distribution; the other with FVC and LAI derived from satellite observations of the International Satellite Land Surface Climate Project （ISLSCP） for 1987 and 1988. The simulations of the two experiments were compared to study the influence of FVC, LAI on summer precipitation interannual variation in the YRB. Compared with observations and the NCEP reanalysis data, the experiment that included both the effects of satellite-derived vegetation indexes and sea surface temperature （SST） produced better seasonal and interannual precipitation variations than the experiment with SST but no interannual variations in FVC and LAI, indicating that better representations of the vegetation index and its interannual variation may be important for climate prediction. The difference between 1987 and 1988 indicated that with the increase of FVC and LAI, especially around the YRB, surface albedo decreased, net surface radiation increased, and consequently local evaporation and precipitation intensified. Further more, surface sensible heat flux, surface temperature and its diurnal variation decreased around the YRB in response to more vegetation. The decrease of surface-emitting longwave radiation due to the cooler surface outweighed the decrease of surface solar radiation income with more cloud coverage, thus maintaining the positive anomaly of net surface radiation. Further study indicated that moisture flux variations associated with changes in the general circulation also contributed to the precipitation interannual variation. 相似文献
7.
The development of satellite-derived vegetation indices and metrics has enabled researchers to monitor land surface phenology (LSP). While the use of satellite data to monitor LSP is prevalent, there has been minimal effort to model LSP in temperate climates using satellite observations of the land surface. Satellite-derived LSP models are beneficial for studying past and future changes in phenology and related ecosystem processes (e.g., water, energy, and carbon fluxes). The purpose of this study was to model LSP during the spring in a mixed temperate forest using satellite-derived measurements of leaf area index (LAI) and land surface temperature (LST). As part of the model validation process, the use of LST as a proxy for air temperature to model LSP was also investigated. The results indicate that LST derived from the MODIS Terra sensor at 10:30?a.m. (local solar time) can be used to develop a LSP model that predicts the full profile of LAI from winter dormancy to maturity and the date when LAI reaches half of the annual maximum (LAI50%) with relatively low error. In addition, the modeled LAI values closely tracked in situ observations of the phenological development of the dominant deciduous tree species located in the study area where the model was developed. A comparison of LST and daily maximum air temperature at two levels above the ground surface revealed distinct differences and nonlinearities in the relationship between these two variables. However, accumulated growing degree-days calculated from each of these variables were similar because the largest differences between LST and daily maximum air temperature occurred prior to the beginning of heat accumulation. Consequently, the model predictions of LAI50% derived from the use of LST and daily maximum air temperature were similar. When the developed model was applied in two other mixed forests, the errors were larger due to substantial interannual variability in the relationship between LAI and heat accumulation and systematic differences in this relationship between sites. Although the model cannot be successfully applied in these other mixed forests, the ability of the model to capture a consistent relationship between satellite estimates of LAI and LST in the study area where it was developed demonstrates that satellite observations of the land surface can be used in certain locations to create LSP phenology models. When validated, the models can be used to examine past and future changes in phenology and related ecosystem processes. 相似文献
8.
9.
热通量和风应力影响北太平洋SST年际和年代际变率的数值模拟 总被引：2，自引：0，他引：2
利用一个大洋环流模式LICOM, 通过1958～2001年风应力 (ERA40) 和热通量驱动下的两组模拟试验, 检验了二者在北太平洋年际和年代际变率形成中的作用。结果表明, 尽管在年际尺度上热带太平洋变率主要受风应力影响, 但合理考虑热通量异常的强迫作用能够显著改进模式对El Niño的模拟效果, 包括对El Niño周期非规则性的成功模拟; 北太平洋SST的年际和年代际异常主要受热通量异常的影响, 合理考虑热通量强迫的年代际变化能够改善模式对北太平洋年代际变率的模拟效果。在北太平洋海盆的不同区域, 导致SST变率异常的因子不同: 在加利福尼亚沿岸, 冬季平均海温的变率异常主要由热通量的异常决定; 在北太平洋中部, 温度趋势异常主要受热通量和水平平流的作用影响; 在黑潮及其延伸体区域, 对温度趋势异常起主导作用的是热通量和海洋非线性作用, 与此同时, 水平平流和扩散的作用亦不容忽视。 相似文献
10.
Simulation of urban climate with high-resolution WRF model: A case study in Nanjing, China 总被引：1，自引：0，他引：1
In this study, urban climate in Nanjing of eastern China is simulated using 1-km resolution Weather Research and Forecasting (WRF) model coupled with a single-layer Urban Canopy Model. Based on the 10-summer simulation results from 2000 to 2009 we find that the WRF model is capable of capturing the high-resolution features of urban climate over Nanjing area. Although WRF underestimates the total precipitation amount, the model performs well in simulating the surface air temperature, relative humidity, and precipitation frequency and inter-annual variability. We find that extremely hot events occur most frequently in urban area, with daily maximum (minimum) temperature exceeding 36°C (28°C) in around 40% (32%) of days. Urban Heat Island (UHI) effect at surface is more evident during nighttime than daytime, with 20% of cases the UHI intensity above 2.5°C at night. However, The UHI affects the vertical structure of Planet Boundary Layer (PBL) more deeply during daytime than nighttime. Net gain for latent heat and net radiation is larger over urban than rural surface during daytime. Correspondingly, net loss of sensible heat and ground heat are larger over urban surface resulting from warmer urban skin. Because of different diurnal characteristics of urban-rural differences in the latent heat, ground heat and other energy fluxes, the near surface UHI intensity exhibits a very complex diurnal feature. UHI effect is stronger in days with less cloud or lower wind speed. Model results reveal a larger precipitation frequency over urban area, mainly contributed by the light rain events (< 10 mm d?1). Consistent with satellite dataset, around 10?C20% more precipitation occurs in urban than rural area at afternoon induced by more unstable urban PBL, which induces a strong vertical atmospheric mixing and upward moisture transport. A significant enhancement of precipitation is found in the downwind region of urban in our simulations in the afternoon. 相似文献
11.
Effects of Land Cover Conversion on Surface Climate 总被引：11，自引：0，他引：11
This study investigates the effects of large-scale human modification of land cover on regional and global climate. A general circulation model (Colorado State University GCM) coupled to a biophysically-based land surface model (SiB2) was used to run two 15-yr climate simulations. The control run used current vegetation distribution as observed by satellite for the year 1987 to derive the vegetation's physiological and morphological properties. The twin simulation used a realistic approximation of vegetation type distribution that would exist in the absence of human disturbance.In temperate latitudes, where anthropogenic modification of the landscape has converted large areas of forest and grassland to cropland, conversion cools canopy temperatures up to 0.7 ° C in summer and 1.1 ° C in winter. This cooling results from both (1) morphological changes in vegetation which increase albedo and (2) physiological changes in vegetation which increase latent heat flux of crops compared with undisturbed vegetation during the growing season. In the tropics and subtropics, conversion warms canopy temperature by about 0.8 ° C year round. The warming results from a combination of morphological changes in vegetation offset by physiological changes that reduce latent heat flux of existing compared with undisturbed vegetation. If water efficient, tropical C4 grasses replace C3 vegetation, latent heat flux is further reduced.The overall effect of land cover conversion is cooling in temperate latitudes and warming in the tropics. Because the effects are opposite in sign in tropics and middle latitudes, they cancel each other when averaged globally. Over land, the surface temperature increased by 0.2 C in winter and remained essentially unchanged in summer. The effects on land surface hydrology were also small when averaged globally. The results suggest that the effects of land use change of the observed magnitude do not have a strong impact on the globally averaged climate but their signature at regional scales is significant and vary according to the type of land cover conversion. 相似文献
12.
环太湖地区土地利用变化的局地气候效应 总被引：3，自引：2，他引：1
利用WRF模式和1985年、2005年环太湖区域的土地利用资料,模拟了环太湖区域土地利用变化的局地气候效应,并从陆面过程的角度进行了分析。模拟结果显示：城市扩张区域净短波辐射通量增多,地面温度升高,感热通量增大,潜热通量减小。近地面水平风场在城市化地区风速减小,在城市化带方向上形成狭长的动能衰减区域。湖陆风和城市热岛环流增强,城市化地区向上垂直速度增大,积云性降水增多。老城区和郊区下沉运动增强,对流受到抑制,积云性降水减少。层云降水的改变,集中在层云降水的大值区,且多呈带状分布。总降水在城市化区域增强,在老城区和郊区减少,积云性降水占总降水的比值增大。在土地利用没有变化的区域,降水的改变与地表能量通量的改变在空间分布上大致吻合。 相似文献
13.
中国区域陆面覆盖变化的气候效应模拟研究 总被引：3，自引：0，他引：3
基于MODIS和CLCV陆面覆盖资料,利用区域气候模式RegCM4分别进行两组24年（1978-2001年）的数值模拟试验,研究中国区域陆面覆盖变化对区域气候的影响。结果表明,以荒漠化和植被退化为主要特征的陆面覆盖变化通过改变陆面能量、水分平衡与大尺度环流进而对气候要素产生重要影响。夏季,中国南方地区普遍降温,季风边缘区及藏北高原气温升高,降水减少;季风边缘区与西北地区气温年际波动加剧;内蒙古中东部地区西南风增强,进而水汽输送增强,一定程度上增加了该地区降水。冬季,中国东部地区偏北气流增强,更多干燥冷空气南下,使得黄河以南地区降水减少、气温降低。 相似文献
14.
In the frame of this paper a heat wave that resulted in record high temperatures in Athens Greece is analysed. Namely the analysis focuses in the ability of three widely used planetary boundary layer parameterisations to reproduce the heat wave temperatures. The simulations were performed with the Pennsylvania State University – National Center for Atmospheric Research MM5 model that is also used for operational weather forecasting at the National Observatory of Athens since 2002. The 2-m temperature at a grid increment of 1-km over the highly complex terrain of the Athens Area is statistically verified against the available surface station observations. The results of the analysis showed that the two nonlocal schemes, namely Blackadar and MRF succeeded much better than the local scheme ETA to reproduce the heat wave 2-m temperature although they considerably underestimated the maximum observed temperatures. In addition, it was found that the model grid points characterised by “urban” land-use provided better statistical verification results, with reduced cold bias. Further, in order to study the role of the initial skin temperature conditions on the 2-m temperature forecasts, satellite observed skin temperatures have been used to initialise the high resolution simulations. This sensitivity test showed that when using the satellite observed skin temperature in the model initial conditions, the simulation of the 2-m temperature is positively affected during the early stages of the simulation while later on the model physical parameterisations are decisive for the time evolution of temperature. 相似文献
15.
This study conducted meteorological simulations in northern Colombia by analyzing different planetary boundary layer (PBL) schemes available in the numerical Weather Research and Forecasting (WRF) model. The study area included three nested domains with horizontal resolutions of 18 km, 6 km, and 2 km, with 38 vertical levels. The evolution and structure of the PBL were analyzed during the driest months (March, April, and May 2016) and in regions with the highest particulate matter concentrations. Sensitivity analysis of the WRF model was performed with two local and two non-local PBL schemes. The results were validated using observations of the surface air temperature, relative humidity, and surface wind speed collected from three meteorological stations in the area. The PBL heights were experimentally determined using radiosonde data provided by a station located in the center of the study area. Variations in PBL heights were estimated using linear regression methods and minimization of statistical errors for the bulk Richardson number, as well as analysis of vertical temperature and wind profiles. The WRF model reliably reproduced the daily values and diurnal cycles of temperature, relative humidity, and wind speed within the PBL and accounted for the influence of topography and sea breezes. Horizontal heat advection dominates the upwelling of air masses when sea breezes are active. The onshore wind direction starts to change from east to northwest, implying a decay in the land breeze regime. All schemes overestimate the mixing height and tend to underestimate surface air temperature values at night. All show wetter conditions and underestimate wind speed. Although the non-local Yonsei University (YSU) scheme shows the best performance, it also shows the largest sources of errors when determining the behavior of the surface layer during stable conditions. Relative humidity and wind speed estimates provided by the local Mellor‐Yamada‐Nakanishi‐Niino (MYNN) scheme were closer to those recorded at the meteorological stations. 相似文献
16.
17.
Martina Weiss Bart van den Hurk Reindert Haarsma Wilco Hazeleger 《Climate Dynamics》2012,39(11):2733-2746
Climate models often use a simplified and static representation of vegetation characteristics to determine fluxes of energy, momentum and water vapour between surface and lower atmosphere. In order to analyse the impact of short term variability in vegetation phenology, we use remotely-sensed leaf area index and albedo products to examine the role of vegetation in the coupled land–atmosphere system. Perfect model experiments are carried out to determine the impact of realistic temporal variability of vegetation on potential predictability of evaporation and temperature, as well as model skill of EC-Earth simulations. The length of the simulation period is hereby limited by the availability of satellite products to 2000–2010. While a realistic representation of vegetation positively influences the simulation of evaporation and its potential predictability, a positive impact on 2?m temperature is of smaller magnitude, regionally confined and more pronounced in climatically extreme years. 相似文献
18.
利用NCEP每6 h一次的1°×1°格点资料和中尺度模式WRF(V3.2),选用不同的陆面参数化方案,对2010年8月7—8日发生在甘肃舟曲的一次西北地区特大暴雨天气过程进行数值模拟试验。结果表明,此次暴雨过程数值模拟的准确率对陆面参数化方案的选择比较敏感。在WRF模式中,耦合陆面方案比不耦合陆面方案对暴雨的模拟效果更好,耦合陆面方案所模拟的降水分布、地表通量以及地面气象要素都与实况更加接近。耦合不同的陆面方案模拟的降水以及感热通量、潜热通量都存在较大的差别,但是采用不同的陆面方案模拟的地表温度和水汽差别并不大。总体而言,采用PX陆面方案对降水的模拟效果比采用其他方案都合理,与实况最接近。 相似文献
19.
A land data assimilation system using the MODIS-derived land data and its application to numerical weather prediction in East Asia 总被引：1，自引：0，他引：1
Yoon-Jin Lim Kun-Young Byun Tae-Young Lee Hyojung Kwon Jinkyu Hong Joon Kim 《Asia-Pacific Journal of Atmospheric Sciences》2012,48(1):83-95
Land Data Assimilation Systems have been developed to generate the surface initial conditions such as soil moisture and temperature for better prediction of weather and climate. We have constructed Korea Land Data Assimilation System (KLDAS) based on an uncoupled land surface modeling framework that integrates high-resolution in-situ observation, satellite data, land surface information from the WRF Preprocessing System (WPS) and the MODIS land products over the East Asia. To present better surface conditions, the KLDAS is driven by atmospheric forcing data from the in-situ rainfall gauges and satellite. In this study, we 1) briefly introduce the KLDAS, 2) evaluate the meteorological states near the surface and the surface fluxes reproduced by the KLDAS against the in-situ observation, and then 3) examine the performance of the mesoscale model initialized by the KLDAS. We have generated a 5-year, 10 km, hourly atmospheric forcing dataset for use in KLDAS operating across East Asia. The KLDAS has effectively reproduced the observed patterns of soil moisture, soil temperature, and surface fluxes. Further scrutiny reveals that the numerical simulations incorporating the KLDAS outputs show better agreement in both the simulated near-surface conditions and rainfall distribution over the Korean Peninsula, compared to those without the KLDAS. 相似文献
20.
6种地表热通量资料在伊朗—青藏高原地区的对比分析 总被引：1，自引：1，他引：1
基于JRA25、ERA40、ERA-Interim、NCEP1、NCEP2和20CR,对比了不同资料中气候平均(1979—2008年)伊朗—青藏高原感热通量和波文比的季节演变,以及夏季高原感热的年际变率和线性趋势。6套资料均表明,由春到夏亚洲大地形区域地表热状况的季节演变存在明显差异,青藏高原东南部低空气旋生成,一方面增多了局地降水,减弱了地表西风,造成潜热加强,感热减弱,波文比减小;另一方面加强了伊朗高原的东北风,抑制了当地降水,令感热加强,波文比增加,构成了青藏—伊朗高原感热通量季节演变的纬向非对称分布。虽然近30 a来伊朗高原(青藏高原)夏季感热线性增加(减小)的趋势一致,但不同资料所反映的伊朗—青藏高原夏季感热通量的年际变化差别明显。 相似文献