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1.
金塔绿洲地表特征参数遥感反演研究   总被引：16，自引：9，他引：7  
TM影像是陆地资源卫星（Landsat）携带的专题绘图仪（Thematic Mapper,TM）扫描计获取的遥感图像,近年来,该数据得到了广泛的应用。本文使用Landsat-5TM数据推算了金塔地区的地表参数,包括标准化差值植被指数NDVI、修正的土壤调整植被指数MSAVI、植被覆盖度、地表反射率及地表温度。并将地表反射率、地表温度的反演值与观测值进行对比,结果表明：地表温度反演结果的相对误差在9％以内,地表反射率反演结果的相对误差在8％以内。  相似文献   

2.
Summary An approach is proposed to estimate the net radiation load at the surface in mountain areas. The components of the radiation balance are derived using a radiative transfer model combined with remotely sensed and digital terrain data. Integrated shortwave (0.28–6.00 µm) and longwave irradiances (3.00–100.00 µm) are computed using a modified version of the Practical Improved Flux Method (PIFM) of Zdunkowski et al. (1982) which makes use of digital topographic data in order to account for slope, aspect, and shading effects. Surface albedo and thermal exitance estimates are obtained using Landsat Thematic Mapper (TM) and digital terrain data combined with the LOWTRAN 7 atmospheric model (Kneizys et al., 1988). LOWTRAN 7 is utilized together with a set of terrain modeling programs to compute direct and diffuse sky irradiance for selected TM bands, and to remove atmospheric effects within the visible, near-infrared, mid-infrared, and thermal infrared bands of Landsat TM. Model testing in the Colorado alpine show a generally good correspondence between estimated values and field measurements obtained over comparable tundra surfaces during several field campaigns. The method is finally used to produce 1) maps of the components of the radiation balance at the time of Landsat TM overflight and 2) maps of daily totals of shortwave irradiance and net shortwave radiation on a typical summer day in the Colorado Rocky Mountains (i.e. including cloud cover effects). The results indicate that the proposed approach is particularly suitable for obtaining estimates of net radiation at the surface from the toposcale to the regional scale.With 6 Figures  相似文献   

3.
Along the international border separatingthe U.S. (Arizona) and Mexico (Sonora), differencesin the grazing intensity of domestic livestock arecommonly presumed to have created a large differencein vegetation cover between the two countries. Thisvegetation difference is reportedly responsible for anextensive albedo and temperature discontinuity thatmay be affecting regional climate. In this study, weused Landsat Thematic Mapper data to examinetrans-border differences in these two biophysicalparameters. Albedo and radiant temperature estimateswere computed for 25 km-long (east-west) transectsthrough semi-desert grassland on each side of theborder at two different times of year. Only smallaverage trans-border differences in these parameterswere found, and in some cases average albedo andtemperature data were essentially equal on each sideof the border. In addition, we found significantspatial heterogeneity in conditions on both sides ofthe border. These results suggest that, based on asmall sample, it may be difficult to assess whetherthere are significant differences in biophysicalproperties of semi-arid grassland between Arizona andMexico in the vicinity of the border. We concludethat more extensive spatial and temporal sampling iscritical in assessing any possible trans-borderdifferences in average terrain conditions that mightaffect climate, and that this data must be coupledwith more extensive meteorological data to assesswhether a difference in climate also exists.  相似文献   

4.
Palm oil production has boomed over the last decade, resulting in an expansion of the global oil palm planting area from 10 to 17 Million hectares between 2000 and 2012. Previous studies showed that a significant share of this expansion has come at the expense of tropical forests, notably in Indonesia and Malaysia, the current production centers. Governments of developing and emerging countries in all tropical regions increasingly promote oil palm cultivation as a major contributor to poverty alleviation, as well as food and energy independence. However, being under pressure from several non-governmental environmental organizations and consumers, the main palm oil traders have committed to sourcing sustainable palm oil. Against this backdrop we assess the area of suitable land and what are the limits to future oil palm expansion when several constraints are considered. We find that suitability is mainly determined by climatic conditions resulting in 1.37 billion hectares of suitable land for oil palm cultivation concentrated in twelve tropical countries. However, we estimate that half of the biophysically suitable area is already allocated to other uses, including protected areas which cover 30% of oil palm suitable area. Our results also highlight that the non-conversion of high carbon stock forest (>100 t AGB/ha) would be the most constraining factor for future oil palm expansion as it would exclude two-thirds of global oil palm suitable area. Combining eight criteria which might restrict future land availability for oil palm expansion, we find that 234 million hectares or 17% of worldwide suitable area are left. This might seem that the limits for oil palm expansion are far from being reached but one needs to take into account that some of this area might be hardly accessible currently with only 18% of this remaining area being under 2 h transportation to the closest city and that growing demand for other agricultural commodities which might also compete for this land has not been yet taken into account.  相似文献   

5.
Near-surface air temperature (NSAT) directly reflects the thermal conditions above the ground and has been considered as a relevant indicator of resident health in urban regions. The rapid retrieval of NSAT data is necessary to assess urban environments. In this paper, a method of NSAT retrieval is developed that employs Landsat Thematic Mapper images using an Energy Balance Bowen Ratio model. This model is established based on the energy balance over land and the Bowen ratio. The degree of retrieval error obtained when using this model is determined on the basis of a comparison with the observed values obtained from weather stations; the mean error is approximately 2.21 °C. Moreover, the spatial relationship between NSAT and urban wetlands is analyzed using Geographical Information System technology. The results show that wetlands have an obvious influence on atmospheric temperature and that this influence decreases as the distance from the wetland increases. When that distance is less than 300 m, its influence on the NSAT is significant.  相似文献   

6.
Tropical rainforests, naturally resistant to fire when intact, are increasingly vulnerable to burning due to ongoing forest perturbation and, possibly, climatic changes. Industrial-scale forest degradation and conversion are increasing fire occurrence, and interactions with climate anomalies such as El Niño induced droughts can magnify the extent and severity of fire activity. The influences of these factors on fire frequency in tropical forests has not been widely studied at large spatio-temporal scales at which feedbacks between fire reoccurrence and forest degradation may develop. Linkages between fire activity, industrial land use, and El Niño rainfall deficits are acute in Borneo, where the greatest tropical fire events in recorded history have apparently occurred in recent decades. Here we investigate how fire frequency in Borneo has been influenced by industrial-scale agricultural development and logging during El Niño periods by integrating long-term satellite observations between 1982 and 2010 – a period encompassing the onset, development, and consolidation of its Borneo’s industrial forestry and agricultural operations as well as the full diversity of El Niño events. We record changes in fire frequency over this period by deriving the longest and most comprehensive spatio-temporal record of fire activity across Borneo using AVHRR Global Area Coverage (GAC) satellite data. Monthly fire frequency was derived from these data and modelled at 0.04° resolution via a random-forest model, which explained 56% of the monthly variation as a function of oil palm and timber plantation extent and proximity, logging intensity and proximity, human settlement, climate, forest and peatland condition, and time, observed using Landsat and similar satellite data. Oil-palm extent increased fire frequency until covering 20% of a grid cell, signalling the significant influence of early stages of plantation establishment. Heighted fire frequency was particularly acute within 10 km of oil palm, where both expanding plantation and smallholder agriculture are believed to be contributing factors. Fire frequency increased abruptly and dramatically when rainfall fell below 200 mm month−1, especially as landscape perturbation increased (indicated by vegetation index data). Logging intensity had a negligible influence on fire frequency, including on peatlands, suggesting a more complex response of logged forest to burning than appreciated. Over time, the epicentres of high-frequency fires expanded from East Kalimantan (1980’s) to Central and West Kalimantan (1990’s), coincidentally but apparently slightly preceding oil-palm expansion, and high-frequency fires then waned in East Kalimantan and occurred only in Central and West Kalimantan (2000’s). After accounting for land-cover changes and climate, our model under-estimates observed fire frequency during ca. 1990–2002 and over-estimates it thereafter, suggesting that a multi-decadal shift to industrial forest conversion and forest landscapes may have diminished the propensity for high-frequency fires in much of this globally significant tropical region since ca. 2000.  相似文献   

7.
Extreme temperatures are key drivers controlling both biotic and abiotic processes, and may be strongly modified by topography and land cover. We modelled mean and extreme temperatures in northern Fennoscandia by combining digital elevation and land cover data with climate observations from northern Finland, Norway and Sweden. Multivariate partitioning technique was utilized to investigate the relative importance of environmental variables for the variation of the three temperature parameters: mean annual absolute minima and maxima, and mean annual temperature. Generalized additive modeling showed good performance, explaining 84–95 % of the temperature variation. The inclusion of remotely sensed variables improved significantly the modelling of thermal extremes in this system. The water cover variables and topography were the most important drivers of minimum temperatures, whereas elevation was the most important factor controlling maximum temperatures. The spatial variability of mean temperatures was clearly driven by geographical location and the effects of topography. Partitioning technique gave novel insights into temperature-environment relationship at the meso-scale and thus proved to be useful tool for the study of the extreme temperatures in the high-latitude setting.  相似文献   

8.
Assessing the ecological status of different districts within a city undergoing urbanization is challenging given their complex surface types and fast pace of development.In this study,we utilized satellite data obtained from Landsat5/TM(Thematic Mapper)and Landsat 8/OLI(Operational Land Imager)images in conjunction with meteorological and socioeconomic data to construct a remote sensing ecological index(RSEI)for monitoring the ecological quality of Nanjing,Jiangsu Province.A higher RSEI value corresponded to better ecological quality.Five ratings were associated with RSEI values of city districts:very poor,poor,average,good,and excellent.In Nanjing,the percentage of areas evidencing good RSEI ratings decreased from 55.9%in 2000 to 48.0%in 2018,whereas there was a slight increase in areas with very poor RSEI ratings during this period.Of the 11 city districts,16.8%,21.8%,and 61.4%respectively evidenced the increasing,decreasing,and stable ecological quality relative to their quality in 2000.Of the11 administrative districts in Nanjing,the main urban districts evidenced increased RSEI values in 2018 compared with those in 2000,with the improved areas exceeding the ones that had deteriorated in these districts.However,the ecological quality of new urban and ed because of the urban expansion,with areas that had deteriorated exceeding the improved ones.Of the three protected ecological zones,the quality of Zijin Mountain National Forest Park was considerably better than that of Laoshan and Jiangxinzhou.Overall,the urbanization rate and RSEI evidenced a high negative correlation coefficient value(-0.76).The urbanization process of Nanjing induced a declining trend for the ecological quality,indicating the need of strong protection measures for the maintenance or improvement of its ecological environment.  相似文献   

9.
土壤-植被-大气系统水分散失机理的数值模拟   总被引：8，自引：0，他引：8  
以Eeardorff(1978)提出的陆面参数化方案和Noilhan等人(1989)土壤水分参数化方案为基础,对陆面物理过程参数化方案进行了改进,在模式中较详细地考虑了植被和地面的各种物理参量如地面和叶面的反射率和发射率,净叶面面积指数,植被的物理阻抗等,并与大气边界层模式耦合。应用该模式模拟了沙漠及绿洲地区不同植被覆盖率情况下的蒸散量、土壤含水量和表面温度的日变化和连续变化特征;对不同植被覆盖率的热量平衡特征进行了比较。结果表明该模式较好地反映了地表蒸散3阶段的变化趋势特征,揭示出下垫面热量平衡分量间的相互转换过程。该模式可以用于中尺度的气象和区域气候模式,模拟和预测不同植被覆盖情况下近地层的热量输送和水分散失情况。  相似文献   

10.
城市扩展影响下的气象观测和气温变化特征分析   总被引：2，自引：1，他引：1  
基于20世纪70年代的MSS(Multi-Spectral Sanner)影像、1990年前后的TM(Thematic Mapper)影像、2000年和2005年前后的ETM(Enhanced Thematic Mapper)影像,对全国700多个地面气象观测站的历史时期下垫面属性进行判别,得到中国自上世纪70年代以来...  相似文献   

11.
 Snow cover fraction (SCF) has a significant influence on the surface albedo and thus on the radiation balance and surface climate. Long-term three dimensional simulations with general circulation models (GCMs) show that the SCF greatly affects the climate in the Northern Hemisphere. By means of both ground observations and remotely sensed data, several deficiencies in the SCF simulated by the current ECHAM4 GCM were identified: over mountainous areas a substantial overestimation in the SCF was found whereas flat areas showed a distinctly underestimated SCF. This work proposes a new parametrization of the SCF for use in GCMs. Evaluations illustrate that it is beneficial to distinguish between the following three terrains: (1) flat, non-forested areas, (2) mountainous regions and (3) forests. The modified SCF parametrization for flat, non-forested areas was derived by using global datasets of ground-based snow depth and remote sensing observations of snow cover data. A 3-dimensional ECHAM4 simulation showed that this modification raises the SCF by up to approximately 20%, mainly in areas with a relatively thin snow cover. The comparison between remotely sensed and simulated mean monthly surface albedo revealed a significant overestimation of the surface albedo in snow-covered mountainous areas. An extension of the current SCF parametrization in ECHAM4 to take into account mountain effects, based on the French climate model Arpège, yielded a close agreement with satellite-derived surface albedo. The adoption of the submodel for snow albedo, as used in the Canadian Land Surface Scheme (CLASS), combined with a newly developed simple snow interception model, demonstrated the ability to capture the main physical processes of snow-covered canopies, including the albedo. The validation of the new parametrization with Boreal Ecosystem-Atmosphere Study (BOREAS) field data showed that the modification is appropriate to capture the main features of the albedo over snow-covered forests during and after heavy snowfall events. Furthermore, the proposed modification has a beneficial impact on the delayed snow melt in spring, a well-known problem in many current GCMs: The simulated surface albedo over the boreal forests decreases by approximately 0.1 during winter and spring, which is in better agreement with ground-based observations. This induces a significant rise in the surface temperature over extended parts of Eurasia and North America in late spring, which subsequently yields a faster snowmelt and an accelerated retreat of the snow line. Received: 28 April 2000 / Accepted: 18 December 2000  相似文献   

12.
Assessing the ecological status of different districts within a city undergoing urbanization is challenging given their complex surface types and fast pace of development. In this study, we utilized satellite data obtained from Landsat 5/TM (Thematic Mapper) and Landsat 8/OLI (Operational Land Imager) images in conjunction with meteorological and socioeconomic data to construct a remote sensing ecological index (RSEI) for monitoring the ecological quality of Nanjing, Jiangsu Province. A higher RSEI value corresponded to better ecological quality. Five ratings were associated with RSEI values of city districts: very poor, poor, average, good, and excellent. In Nanjing, the percentage of areas evidencing good RSEI ratings decreased from 55.9% in 2000 to 48.0% in 2018, whereas there was a slight increase in areas with very poor RSEI ratings during this period. Of the 11 city districts, 16.8%, 21.8%, and 61.4% respectively evidenced the increasing, decreasing, and stable ecological quality relative to their quality in 2000. Of the 11 administrative districts in Nanjing, the main urban districts evidenced increased RSEI values in 2018 compared with those in 2000, with the improved areas exceeding the ones that had deteriorated in these districts. However, the ecological quality of new urban and ed because of the urban expansion, with areas that had deteriorated exceeding the improved ones. Of the three protected ecological zones, the quality of Zijin Mountain National Forest Park was considerably better than that of Laoshan and Jiangxinzhou. Overall, the urbanization rate and RSEI evidenced a high negative correlation coefficient value (−0.76). The urbanization process of Nanjing induced a declining trend for the ecological quality, indicating the need of strong protection measures for the maintenance or improvement of its ecological environment.  相似文献   

13.
Wind speed is an important meteorological variable for various scientific communities. In this study, numerical mesoscale simulations were performed over the Republic of Korea in 2006, to produce wind information distributed homogeneously with space. Then, an attempt was made to statistically correct the simulated nearsurface wind speed using remotely sensed surface observations. The weak wind season (WWS, from May to October) and strong wind season (SWS, from November to April) were classified on the basis of the annual mean wind speed. Although the spatial features and monthly variation pattern of the near-surface wind speed were reasonably simulated in the Weather Research and Forecasting (WRF) model, the simulations overestimated the observed values. To correct the simulated wind speeds, a regression-based statistical algorithm with different constants and coefficients for WWS and SWS was developed using match-up datasets of wind observations and satellitederived variables (land surface temperature and normalized difference water index). The corrected wind speeds showed reasonable performance for both WWS and SWS with respect to observed values. The monthly variation in the corrected wind speeds over the Republic of Korea also matched better with observations throughout the year, within a monthly bias range of approximately ± 0.2 m s?1. The proposed algorithm using remotely sensed surface observations may be useful for correcting simulated near-surface wind speeds and improving the accuracy of wind assessments over the Republic of Korea.  相似文献   

14.
Fire disturbance in many tropical forests, including peat swamps, has become more frequent and extensive in recent decades. These fires compromise a variety of ecosystem services, among which mitigating global climate change through carbon storage is particularly important for peat swamps. Indonesia holds the largest amount of tropical peat carbon globally, and mean annual CO2 emissions from decomposition of deforested and drained peatlands and associated fires in Southeast Asia have been estimated at ∼2000 Mt y-1. A key component to understanding and therefore managing fire in the region is identifying the land use/land cover classes associated with fire ignitions. We assess the oft-asserted claim that escaped fires from oil palm concessions and smallholder farms near settlements are the primary sources of fire in a peat-swamp forest area in Central Kalimantan, Indonesia, equivalent to around a third of Kalimantan's total peat area. We use the MODIS Active Fire product from 2000 to 2010 to evaluate the fire origin and spread on the land use/land cover classes of legal, industrial oil palm concessions (the only type of legal concession in the study area), non-forest, and forest, as well as in relation to settlement proximity. We find that most fires (68–71%) originate in non-forest, compared to oil palm concessions (17%–19%), and relatively few (6–9%) are within 5 km of settlements. Moreover, most fires started within oil palm concessions and in close proximity to settlements stay within those boundaries (90% and 88%, respectively), and fires that do escape constitute only a small proportion of all fires on the landscape (2% and 1%, respectively). Similarly, a small proportion of fire detections in forest originate from oil palm concessions (2%) and within close proximity to settlements (2%). However, fire ignition density in oil palm (0.055 ignitions km−2) is comparable to that in non-forest (0.060 km-2 ignitions km-2), which is approximately ten times that in forest (0.006 ignitions km−2). Ignition density within 5 km of settlements is the highest at 0.125 ignitions km−2. Furthermore, increased anthropogenic activity in close proximity to oil palm concessions and settlements produces a detectable pattern of fire activity. The number of ignitions decreases exponentially with distance from concessions; the number of ignitions initially increases with distance from settlements, and, around from 7.2 km, then decreases with distance from settlements. These results refute the claim that most fires originate in oil palm concessions, and that fires escaping from oil palm concessions and settlements constitute a major proportion of fires in this study region. However, there is a potential for these land use types to contribute substantially to the fire landscape if their area expands. Effective fire management in this area should therefore target not just oil palm concessions, but also non-forested, degraded areas where ignitions and fires escaping into forest are most likely to occur.  相似文献   

15.
A variational data assimilation scheme is used to infer two key parameters ofthe surface energy balance that control the partitioning of available energy intolatent, sensible, and ground heat fluxes (LE, H, and G). Remotely sensedland surface temperature (LST) is the principal data source. Maps ofdiurnal energy balance components are presented for a basin with varied landcover (Arno Basin, Italy) for a 18-day period in July 1996.Given available energy, the major unknown (dimensionless) parameters requiredfor partitioning among fluxes are: (1) Landscape effects on near-surfaceturbulence as captured by the bulk heat transfer coefficient CBN underneutral conditions and (2) surface control of the relative magnitudes of LEand H as represented by the evaporative fraction EF. The data assimilationscheme merges 1.1-km resolution remotely sensed LST images (based onoptical, thermal and microwave measurements from two different satelliteplatforms) into a parsimonious model of heat diffusion. Both the measurementsand the model predictions are considered uncertain. Posterior error statisticsthat represent uncertainty of the estimated parameters are also derived.Maps of CBN show spatial patterns consistent with the dominant land useand basin physiography. Daily maps of EF exhibit spatial variationscorresponding to land cover and land use – the day-to-day variations inEF show fluctuations consistent with rain events and drydowns experiencedduring the period. Based on these parameters and available environmentalvariables, maps of diurnal LE and H may be produced (in this paper daytimeLE maps are reported).The application demonstrates that remotely sensed land surface temperaturesequences contain significant amount of information of the partitioning ofavailable energy among the fluxes. The variational data assimilation frameworkis shown to be an efficient and parsimonious approach without reliance onempirical relationships such as those based on vegetation indices.  相似文献   

16.
The urban heat island (UHI) effect changes heat and water cycles in urban areas, and has been accused of elevating energy consumption, deteriorating living environment, and increasing mortality rates. Understanding various UHI effects necessitates a systematic modeling approach. A major problem in UHI simulations is that urban areas were either considered to have only one category of land use/cover or outdated in land use/cover patterns due to the lack of high resolution data. Therefore, this study aims at integrating up-to-date remotely sensed land use/cover data with the Weather Research and Forecasting (WRF/UCM)/Urban Canopy Model modeling systems to simulate surface temperature patterns in Atlanta, Georgia. In addition, three land-use scenarios, i.e., spontaneous scenario (SS), concentrated scenario (CS), and local policy scenario (LPS), were designed and incorporated into the modeling. Five numerical experiments were conducted by using the Weather Research and Forecasting (WRF) model to explore the impact of urbanization-induced land-cover changes on temperature patterns. Land use and land-cover patterns under all three scenarios suggested that urban growth would continue through in-filling development and outward expansion. Compared to temperature simulations in 2011, temperature maps corresponding to the three urban growth scenarios showed warmer and cooler temperature patterns outside and inside the urban core, respectively. Analysis of the mean diurnal temperature cycle suggested that the highest temperature difference of 3.9 K was observed between 2011 and the LPS, and occurred around 22:00 local time. Overall, the simulations showed different UHI effects respond to the land-use scenarios in the summer. It is recommended for urban managers and policy makers to reflect on the potential impacts of alternative urban growth policies on thermal environment.  相似文献   

17.
南京市夏季热岛特征及其与土地利用覆盖关系研究   总被引：4，自引：0，他引：4  
裴欢  房世峰 《干旱气象》2008,26(1):23-27
利用南京市7月的Landsat TM热红外波段数据,根据单窗算法反演得到南京市地表温度,讨论了南京市热岛特征,并分析了产生这种现象的原因。通过遥感和地理信息系统相结合,运用Landsat TM数据,提取出南京市下垫面类型,分析了不同地表覆盖类型的热辐射特征并定量地分析了土地利用及植被对地表温度的影响。结果显示,南京市夏季主要存在3个热岛中心,分别是建成区、大厂区和八卦洲。南京城区地表温度明显比郊区地表温度高,通过地表温度对比分析发现,城区平均地表温度比城市边缘和远郊区地表温度分别高出3.5℃和5.7℃,城市热岛效应明显。不同地表覆盖类型的地表温度也有显著差异,从高到低依次为：城镇建设用地、耕地、草地、林地、水体。城镇建设用地与水体的表面温度最大相差14℃。城市地表温度与植被覆盖度具有明显的负相关关系,城市地表植被覆盖度低是城市热岛出现的主要原因,今后应当更加注重城市绿地建设,提高植被覆盖率。  相似文献   

18.
A number of remotely sensed land cover datasets with spatial resolutions ~〈 1 km have recently become available or are in the process of being mapped. The application of these higher resolution and more up-to-date land cover datasets in chemical transport models （CTMs） is expected to improve the simulation of dry deposition and biogenic emissions of non-methane volatile organic compounds （NMVOCs）, which affect ozone and other secondary air pollutants. In the present study, we updated the land cover dataset in the nested-grid GEOS-Chem CTM with the 1 km resolution GLC2000 land cover map and examined the resulting changes in the simulation of surface ozone and sulfate over China in July 2007. Through affecting the dry deposition velocities of ozone and its precursors, using GLC2000 in the dry deposition module can decrease the simulated surface ozone by 3% （up to 6 ppb） over China. Simulated surface sulfate shows an increase of 3% in northwestern China and a decrease of 1% in northern China. Applying GLC2000 in the biogenic emissions of the NMVOC module can lead to a 0.5--4.5 ppb increase in simulated surface ozone over East China, mainly driven by the larger cove~：age of broadleaf trees in East China in the GLC2000 dataset. Our study quantifies the large sensitivity to land cover dataset~ with different spatial resolutions and time periods of simulated secondary air pollutants over China, supporting ongoing research efforts to produce high resolution and dynamically updated land cover datasets over China, as well as for the globe.  相似文献   

19.
Tropical rainforest plays an important role in the global carbon cycle, accounting for a large part of global net primary productivity and contributing to CO2 sequestration. The objective of this work is to simulate potential changes in the rainforest biome in Central America subject to anthropogenic climate change under two emissions scenarios, RCP4.5 and RCP8.5. The use of a dynamic vegetation model and climate change scenarios is an approach to investigate, assess or anticipate how biomes respond to climate change. In this work, the Inland dynamic vegetation model was driven by the Eta regional climate model simulations. These simulations accept boundary conditions from HadGEM2-ES runs in the two emissions scenarios. The possible consequences of regional climate change on vegetation properties, such as biomass, net primary production and changes in forest extent and distribution, were investigated. The Inland model projections show reductions in tropical forest cover in both scenarios. The reduction of tropical forest cover is greater in RCP8.5. The Inland model projects biomass increases where tropical forest remains due to the CO2 fertilization effect. The future distribution of predominant vegetation shows that some areas of tropical rainforest in Central America are replaced by savannah and grassland in RCP4.5. Inland projections under both RCP4.5 and RCP8.5 show a net primary productivity reduction trend due to significant tropical forest reduction, temperature increase, precipitation reduction and dry spell increments, despite the biomass increases in some areas of Costa Rica and Panama. This study may provide guidance to adaptation studies of climate change impacts on the tropical rainforests in Central America.  相似文献   

20.
Optical remote sensing data collected during the Monsoon '90 experiment in the Walnut Gulch Experimental Watershed in southern Arizona were used to estimate basin-scale surface temperature, net radiation (R n) and soil heat flux (G). These were combined with several atmospheric boundary-layer (ABL) models to allow computation of basin-scale surface fluxes of sensible (H) and latent heat (LE). The calculated fluxes were compared to averages from a network of surface flux stations. One ABL model calculatedH using a bulk similarity approach for wind and temperature with remotely sensed surface temperature as the lower boundary condition. With basin-scale estimates ofR n andG, LE was solved as a residual. The other ABL model applied atmospheric profiles from a series of soundings in the conservation equations of temperature and humidity in the mixed layer to computeH andLE directly. By combining theseH values withR n andG, calculation ofLE by residual also was performed. The ABL-derivedH values differed from the averages from the surface network by roughly 20 and 30% for the bulk similarity and conservation approaches, respectively. ForLE, these same differences were around 10 and 70%. The disparity was reduced to nearly 30% for the conservation approach whenLE was solved as a residual. Days with significant spatial variation in surface soil moisture and/or cloud cover were associated with most of the disagreement between the ABL-derived and surface-based values. This was particularly true for conservation estimates ofLE. The bulk similarity method appeared less sensitive non-ideal environmental conditions. This may in part be due to the use of remotely sensed information, which provided a lower boundary value of surface temperature and estimates ofR n andG over the study area, thereby allowing for residual calculations ofLE. Such information clearly has utility for assessing the surface energy and water balance at basin scale.  相似文献   

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