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1.
Drought forecasting is a critical component of drought risk management. Identification of effective predictors is a major component of forecasting models. Sea surface temperature (SST) and sea level pressure (SLP) are relevant predictors for short- to long-term drought forecasts. However, these datasets are captured globally within a cell-wise network. This paper describes an approach to locate the most effective cells of the SST and SLP datasets using data mining. They are then applied as input to an adaptive neurofuzzy inference system (ANFIS) model to forecast possible droughts 3, 6, and 9?months in advance. Tehran plain was selected as the study area, and drought events are designated using the effective drought index (EDI). In another treatment, past values of the EDI time series were introduced to the ANFIS and the results compared with the previous findings. It was shown that R 2 values were higher for all cases applying the SST/SLP datasets. Additionally, the performance of SST/SLP datasets and the ANFIS model was assessed according to ??drought?? or ??wet?? classification, and it was concluded that more than 90% of the time the ANFIS model detected the drought status correctly or with only a one class error.  相似文献   

2.
We use an early twentieth century (1908?C1958) atmospheric reanalysis, based on assimilation of surface and sea level pressure observations, to contrast atmospheric circulation during two periods of persistent drought in North America: 1932?C1939 (the ??Dust Bowl??) and 1948?C1957. Primary forcing for both droughts is believed to come from anomalous sea surface temperatures (SSTs): a warm Atlantic and a cool eastern tropical Pacific. For boreal winter (October?CMarch) in the 1950s, a stationary wave pattern originating from the tropical Pacific is present, with positive centers over the north Pacific and north Atlantic ocean basins and a negative center positioned over northwest North America and the tropical/subtropical Pacific. This wave train is largely absent for the 1930s drought; boreal winter height anomalies are organized much more zonally, with positive heights extending across northern North America. For boreal summer (April?CSeptember) during the 1930s, a strong upper level ridge is centered over the Great Plains; this feature is absent during the 1950s and appears to be linked to a weakening of the Great Plains low-level jet (GPLLJ). Subsidence anomalies are co-located over the centers of each drought: in the central Great Plains for the 1930s and in a band extending from the southwest to the southeastern United States for the 1950s. The location and intensity of this subsidence during the 1948?C1957 drought is a typical response to a cold eastern tropical Pacific, but for 1932?C1939 deviates in terms of the expected intensity, location, and spatial extent. Overall, circulation anomalies during the 1950s drought appear consistent with the expected response to the observed SST forcing. This is not the case for the 1930s, implying some other causal factor may be needed to explain the Dust Bowl drought anomalies. In addition to SST forcing, the 1930s were also characterized by massive alterations to the land surface, including regional-scale devegetation from crop failures and intensive wind erosion and dust storms. Incorporation of these land surface factors into a general circulation model greatly improves the simulation of precipitation and subsidence anomalies during this drought, relative to simulations with SST forcing alone. Even with additional forcing from the land surface, however, the model still has difficulty reproducing some of the other circulation anomalies, including weakening of the GPLLJ and strengthening of the upper level ridge during AMJJAS. This may be due to either weaknesses in the model or uncertainties in the boundary condition estimates. Still, analysis of the circulation anomalies supports the conclusion of an earlier paper (Cook et?al. in Proc Natl Acad Sci 106:4997, 2009), demonstrating that land degradation factors are consistent with the anomalous nature of the Dust Bowl drought.  相似文献   

3.
The Madden?CJulian oscillation (MJO) is the most prominent form of tropical intraseasonal variability. This study investigated the following questions. Do interannual-to-decadal variations in tropical sea surface temperature (SST) lead to substantial changes in MJO activity? Was there a change in the MJO in the 1970s? Can this change be associated to SST anomalies? What was the level of MJO activity in the pre-reanalysis era? These questions were investigated with a stochastic model of the MJO. Reanalysis data (1948?C2008) were used to develop a nine-state first order Markov model capable to simulate the non-stationarity of the MJO. The model is driven by observed SST anomalies and a large ensemble of simulations was performed to infer the activity of the MJO in the instrumental period (1880?C2008). The model is capable to reproduce the activity of the MJO during the reanalysis period. The simulations indicate that the MJO exhibited a regime of near normal activity in 1948?C1972 (3.4?events?year?1) and two regimes of high activity in 1973?C1989 (3.9 events) and 1990?C2008 (4.6 events). Stochastic simulations indicate decadal shifts with near normal levels in 1880?C1895 (3.4 events), low activity in 1896?C1917 (2.6 events) and a return to near normal levels during 1918?C1947 (3.3 events). The results also point out to significant decadal changes in probabilities of very active years (5 or more MJO events): 0.214 (1880?C1895), 0.076 (1896?C1917), 0.197 (1918?C1947) and 0.193 (1948?C1972). After a change in behavior in the 1970s, this probability has increased to 0.329 (1973?C1989) and 0.510 (1990?C2008). The observational and stochastic simulations presented here call attention to the need to further understand the variability of the MJO on a wide range of time scales.  相似文献   

4.
Using the Objectively Analyzed air?Csea Fluxes dataset (and also the National Oceanography Centre Southampton Flux Dataset v2.0), we examined both the annual mean climatology and trend of net air?Csea surface heat flux (Q net) for 1984?C2004 over the North Pacific and North Atlantic oceans (10°N?C50°N). The annual mean Q net climatology shows that oceans obtain the positive Q net over much of the North Pacific and North Atlantic oceans. Exceptions are the regions of western boundary currents (WBCs) including the Kuroshio and its extension off Japan and the Gulf Stream off the USA and its extension, where oceans release lots of heat into the atmosphere, mainly ascribed to the large surface turbulent heat loss. The statistically significant negative Q net trends occurred in the WBCs, while the statistically significant positive Q net trends appeared in the central basins of Northern Subtropical Oceans (CNSOs) including the central basin of Northern Subtropical Pacific and the central basin of Northern Subtropical Atlantic. These indentified Q net trends, which are independent of both El Ni?o-Southern Oscillation (ENSO) and ENSO Modoki but closely related to global warming forcing, are predominately due to the statistically significant surface latent heat (LH) trends. Over the WBCs, the positive LH trends are mainly induced by the sea surface temperature increasing, indicating the ocean forcing upon overlying atmosphere. In contrast, over the CNSOs, the negative LH trends are mainly caused by the near-surface air specific humidity increasing, indicative of an oceanic response to overlying atmospheric forcing.  相似文献   

5.
The meteorological scenario of Ethiopian highlands floods is studied. Daily rainfall in the period 1997?C2007 reveals two peaks: 23?C28 July 2006 and 26?C31 July 2007. National Center for Environmental Prediction (NCEP) composites suggest that anomalous southerly monsoon flow over the West Indian Ocean is re-directed by an anomalous Arabian ridge westward across the Red Sea and Ethiopia. A tongue of moisture stretches from the Congo towards the highlands, but westerly equatorial wind anomalies are absent. Anomalous sinking motions and dry conditions are evident over the West Indian Ocean. Diurnal analysis reveals northwesterly flow over eastern Sudan during afternoon hours, whilst back-trajectory analysis highlights a Red Sea source and lifting over the eastern escarpment of Ethiopia. The upper level tropical easterly jet connects Indian and Ethiopian rainfall at intra-seasonal (~40?days) time scale; whilst low-level meridional flow convergence is evident during flood events. Hovmoller analysis on 10°N reveals cyclonic signals propagating westward from the Arabian Sea at 500?km?day?1 that produces a 10-day cycle in Ethiopian rainfall. The floods in 2006?C2007 occurred at the peak of the annual cycle, with diurnal controls inducing ? of rain in the late evening. Whilst cold surges from southern Africa played a role in the 2006 flood, bursts in the northern Hadley cell are a more general determinant. The convection associated with the 2007 flood went on to become a destructive Atlantic hurricane.  相似文献   

6.
Spatial information on climatic characteristics is beneficial in e.g. regional planning, building construction and urban ecology. The possibility to spatially predict urban?Crural temperatures with statistical techniques and small sample sizes was investigated in Turku, SW Finland. Temperature observations from 36 stationary weather stations over a period of 6?years were used in the analyses. Geographical information system (GIS) data on urban land use, hydrology and topography served as explanatory variables. The utilized statistical techniques were generalized linear model and boosted regression tree method. The results demonstrate that temperature variables can be robustly predicted with relatively small sample sizes (n????20?C40). The variability in the temperature data was explained satisfactorily with few accessible GIS variables. Statistically based spatial modelling provides a cost-efficient approach to predict temperature variables on a regional scale. Spatial modelling may aid also in gaining novel insights into the causes and impacts of temperature variability in extensive urbanized areas.  相似文献   

7.
Changes of global land monsoon precipitation are assessed by using three sets of rain-gauge precipitation data for the period of 1901?C2002 compiled by GPCC, CRU and Dai-dataset, respectively. The three datasets show consistent long-term changes of precipitation over the monsoon region with slightly different amplitudes. During 1901?C2001, global land monsoon precipitation (GMI) exhibits multi-decadal variations, with an overall increasing trend from 1901 to 1955, followed by a decreasing trend up to 2001. The upward trends of global and Northern hemispheric land monsoon precipitation during 1901?C1955 are mainly resulted from the increased precipitation over the North African, Indian and East Asian monsoon domains. For the whole period of 1901?C2001, precipitation averaged over the Northern Hemisphere and global land monsoon areas both exhibit a decreasing trend although it is only statistically significant at the 5% level for the Northern Hemisphere. The robust decreasing trend of Northern hemispheric land monsoon precipitations during the twentieth century mainly comes from the downward trend of North African and eastern part of Indian monsoon precipitation and occurs mainly after the 1950s. The first leading mode of Empirical orthogonal function (EOF) analysis of precipitation annual range features a coherent change of North African, South Asian, Northeast China, southern South African, eastern Australian and western American monsoon, and a coherent change over the equatorial South African monsoon and eastern American monsoon. The corresponding principal component time series also indicate that the majority of global land monsoon precipitation has experienced an increasing tendency from 1901 to 1955 and a decreasing trend since the 1950s. Examination on the impact of station number change indicates a negligible influence on the results, especially after 1905.  相似文献   

8.
Gilles Bellon 《Climate Dynamics》2011,37(5-6):1081-1096
A simple coupled model is used in a zonally-symmetric configuration to investigate the effect of land?Catmosphere coupling on the Asian monsoon intraseasonal oscillation. The atmospheric model is a version of the Quasi-equilibrium Tropical Circulation Model with a prognostic atmospheric boundary layer, as well as two free-tropospheric modes in momentum, and one each in moisture and temperature. The land model is the simple one-layer model SLand. The complete nonlinear version and a linear version of the model are used to understand how land?Catmosphere interaction influences the northward-propagating intraseasonal oscillation that has been documented in the atmospheric model (Bellon and Sobel in J Geophys Res 113, 2008a, J Atmos Sci 65:470?C489, 2008b). Our results show that this interaction damps the intraseasonal variability in most cases. The small heat capacity of land surfaces is the main factor that intervenes directly in the dynamics of the intraseasonal oscillation and explains the damping of intraseasonal variability. But in a few peculiar cases, the small heat capacity of land can also cause a strong interaction between the intraseasonal oscillation and the mean state via the nonlinearity of precipitation, that enhances the monsoon intraseasonal variability. High land albedo indirectly influences the intraseasonal variability by setting the seasonal mean circulation to conditions unfavorable for the monsoon intraseasonal oscillation.  相似文献   

9.
Most of the annual rainfall over India occurs during the Southwest (June?CSeptember) and Northeast (October?CDecember) monsoon periods. In March 2008, however, Southern peninsular India and Sri Lanka received the largest rainfall anomaly on record since 1979, with amplitude comparable to summer-monsoon interannual anomalies. This anomalous rainfall appeared to be modulated at intraseasonal timescale by the Madden Julian Oscillation, and was synchronous with a decaying La Ni?a event in the Pacific Ocean. Was this a coincidence or indicative of a teleconnection pattern? In this paper, we explore factors controlling rainfall over southern India and Sri Lanka between January and April, i.e. outside of the southwest and northeast monsoons. This period accounts for 20% of annual precipitation over Sri Lanka and 10% over the southern Indian states of Kerala and Tamil Nadu. Interannual variability is strong (about 40% of the January?CApril climatology). Intraseasonal rainfall anomalies over southern India and Sri Lanka are significantly associated with equatorial eastward propagation, characteristic of the Madden Julian Oscillation. At the interannual timescale, we find a clear connection with El Ni?o-Southern Oscillation (ENSO); with El Ni?os being associated with decreased rainfall (correlation of ?0.46 significant at the 98% level). There is also a significant link with local SST anomalies over the Indian Ocean, and in particular with the inter-hemispheric sea surface temperature (SST) gradient over the Indian Ocean (with colder SST south of the equator being conducive to more rainfall, correlation of 0.55 significant at the 99% level). La Ni?as/cold SSTs south of the equator tend to have a larger impact than El Ni?os. We discuss two possible mechanisms that could explain these statistical relationships: (1) subsidence over southern India remotely forced by Pacific SST anomalies; (2) impact of ENSO-forced regional Indian Ocean SST anomalies on convection. However, the length of the observational record does not allow distinguishing between these two mechanisms in a statistically significant manner.  相似文献   

10.
Monthly observed wind speed data at 597 weather stations and NCEP wind speed data at 10?m above surface were used to explore the temporal variations of the wind speed for 1961?C2007 in China. The results indicate that the temporal variation of annual wind speed in China has experienced four phases: two relatively steady periods from 1961 to 1968 and 1969 to 1974 with a sharp step change in 1969, a statistically significant decline stage from 1974 to 1990s, and another relatively steady period from 1990s to 2007. Except for the sharp step in 1969 being caused by the changes of observation instrument, other breakpoints correspond well with the positive and negative phases of the interdecadal Pacific oscillation. In addition, four different temporal variation patterns of annual wind speed in China have been identified by using cluster analysis and their spatial distributions were also explored.  相似文献   

11.
To improve the capability of numerical modeling of climate-groundwater interactions, a groundwater component and new surface/subsurface runoff schemes were incorporated into the regional climate model RegCM3, renamed RegCM3_Hydro. 20－year simulations from both models were used to investigate the effects of groundwater dynamics and surface/subsurface runoff parameterizations on regional climate over seven river basins in China. A comparison of results shows that RegCM3_Hydro reduced the positive biases of annual and summer (June, July, August) precipitation over six river basins, while it slightly increased the bias over the Huaihe River Basin in eastern China. RegCM3_Hydro also reduced the cold bias of surface air temperature from RegCM3 across years, especially for the Haihe and the Huaihe river basins, with significant bias reductions of 0.80C and 0.88C, respectively. The spatial distribution and seasonal variations of water table depth were also well captured. With the new surface and subsurface runoff schemes, RegCM3_Hydro increased annual surface runoff by 0.11－0.62 mm d－1 over the seven basins. Though previous studies found that incorporating a groundwater component tends to increase soil moisture due to the consideration of upward groundwater recharge, our present work shows that the modified runoff schemes cause less infiltration, which outweigh the recharge from groundwater and result in drier soil, and consequently cause less latent heat and more sensible heat over most of the basins.  相似文献   

12.
陆面过程模式中地下水位的参数化及初步应用   总被引：11，自引：2，他引：9  
谢正辉  梁旭  曾庆存 《大气科学》2004,28(3):374-384
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.  相似文献   

13.
In this study, a groundwater exploitation scheme is incorporated into the regional climate model, RegCM4, and the climatic responses to anthropogenic alteration of groundwater are then investigated over the Haihe River Basin in Northern China where groundwater resources are overexploited. The scheme models anthropogenic groundwater exploitation and water consumption, which are further divided into agricultural irrigation, industrial use and domestic use. Four 30-year on-line exploitation simulations and one control test without exploitation are conducted using the developed model with different water demands estimated from relevant socioeconomic data. The results reveal that the groundwater exploitation and water consumption cause increasing wetting and cooling effects on the local land surface and in the lower troposphere, along with a rapidly declining groundwater table in the basin. The cooling and wetting effects also extended outside the basin, especially in the regions downwind of the prevailing westerly wind, where increased precipitation occurs. The changes in the four exploitation simulations positively relate to their different water demands and are highly non-linear. The largest changes in climatic variables usually appear in spring and summer, the time of crop growth. To gain further insights into the direct changes in land-surface variables due to groundwater exploitation regardless of the atmospheric feedbacks, three off-line simulations using the land surface model Community Land Model version 3.5 are also conducted to distinguish these direct changes on the land surface of the basin. The results indicate that the direct changes of land-surface variables respond linearly to water demand if the climatic feedbacks are not considered, while non-linear climatic feedbacks enhance the differences in the on-line exploitation simulations.  相似文献   

14.
在耦合模式WRF/Noah-MP中加入考虑地下水过程的动态灌溉方案,设计两组试验（分别为考虑和不考虑地下水灌溉）,连续模拟10 a（2001—2010年）,来研究华北平原地下水灌溉的区域气候效应。结果表明,地下水灌溉导致华北平原地下水位下降,在少雨的季节灌溉量大,水位下降较快。在灌溉期（3—9月）,灌溉引起的土壤湿度升高影响了地表能量的分配（潜热增加,感热减少）,导致2 m气温显著降低0.6—1.0℃,同时也降低了灌溉区夏季模拟偏高的气温。灌溉对灌溉区边界层大气有升高湿度和冷却降温的作用,对春季的影响局限在边界层内,而夏季的影响持续到5000 m以上。夏季灌溉对降水的影响远强于春季,灌溉的升高湿度和冷却效应分别对夏季降水产生正反馈和负反馈,共同影响灌溉区的降水变化。灌溉通过对水汽输送的影响,引起非灌溉区降水的变化,而长江中下游流域夏季降水的增多可能与高空西风急流轴位置南移有关。   相似文献   

15.
葛骏  余晔  解晋  昝蓓蕾 《大气科学》2017,41(5):918-932
利用青藏高原北麓河观测站（退化高寒草甸）和玛曲观测站（高寒草原）2014年地面观测资料,通过组合分类法,对比分析了两类下垫面生长季土壤含水量、水汽压差和净辐射对地表能量分配的直接影响和间接影响,并且利用路径分析法研究了影响地表能量分配的关键气候因子。结果表明:北麓河站和玛曲站潜热占比（潜热通量与地表可利用能量的比值）对土壤含水量的响应分别处于土壤水分抑制阶段和能量抑制阶段。其中,北麓河站潜热占比在水汽压差较大时随土壤含水量增长较快,受净辐射的影响较小;而玛曲站潜热占比随土壤含水量的变化趋势受水汽压差和净辐射的影响均较小。北麓河站潜热占比随水汽压差的增大先减小后趋于不变,并且潜热占比对水汽压差的敏感性随土壤含水量的增大而减小;而玛曲站潜热占比随水汽压差的增大先增大后趋于不变,几乎不受土壤含水量和净辐射的影响。北麓河站和玛曲站潜热占比均随净辐射的增大趋于稳定,其稳定值分别与土壤含水量和水汽压差有关。路径分析结果显示,降水是影响北麓河站潜热占比的主要气候因子,而气温是影响玛曲站潜热占比的主要气候因子。  相似文献   

16.
Processes acting at the interface between the land surface and the atmosphere have a strong impact on the European summer climate, particularly during extreme years. These processes are to a large extent associated with soil moisture (SM). This study investigates the role of soil moisture?Catmosphere coupling for the European summer climate over the period 1959?C2006 using simulations with a regional climate model. The focus of this study is set on temperature and precipitation extremes and trends. The analysis is based on simulations performed with the regional climate model CLM, driven with ECMWF reanalysis and operational analysis data. The set of experiments consists of a control simulation (CTL) with interactive SM, and sensitivity experiments with prescribed SM: a dry and a wet run to determine the impact of extreme values of SM, as well as experiments with lowpass-filtered SM from CTL to quantify the impact of the temporal variability of SM on different time scales. Soil moisture?Cclimate interactions are found to have significant effects on temperature extremes in the experiments, and impacts on precipitation extremes are also identified. Case studies of selected major summer heat waves reveal that the intraseasonal and interannual variability of SM account for 5?C30% and 10?C40% of the simulated heat wave anomaly, respectively. For extreme precipitation events on the other hand, only the wet-day frequency is impacted in the experiments with prescribed soil moisture. Simulated trends for the past decades, which appear consistent with projected changes for the 21st century, are identified to be at least partly linked to SM-atmosphere feedbacks.  相似文献   

17.
Land surface hydrology (LSH) is a potential source of long-range atmospheric predictability that has received less attention than sea surface temperature (SST). In this study, we carry out ensemble atmospheric simulations driven by observed or climatological SST in which the LSH is either interactive or nudged towards a global monthly re-analysis. The main objective is to evaluate the impact of soil moisture or snow mass anomalies on seasonal climate variability and predictability over the 1986–1995 period. We first analyse the annual cycle of zonal mean potential (perfect model approach) and effective (simulated vs. observed climate) predictability in order to identify the seasons and latitudes where land surface initialization is potentially relevant. Results highlight the influence of soil moisture boundary conditions in the summer mid-latitudes and the role of snow boundary conditions in the northern high latitudes. Then, we focus on the Eurasian continent and we contrast seasons with opposite land surface anomalies. In addition to the nudged experiments, we conduct ensembles of seasonal hindcasts in which the relaxation is switched off at the end of spring or winter in order to evaluate the impact of soil moisture or snow mass initialization. LSH appears as an effective source of surface air temperature and precipitation predictability over Eurasia (as well as North America), at least as important as SST in spring and summer. Cloud feedbacks and large-scale dynamics contribute to amplify the regional temperature response, which is however, mainly found at the lowest model levels and only represents a small fraction of the observed variability in the upper troposphere.  相似文献   

18.
Water stored as part of the land surface is lost to evapotranspiration and runoff on different time scales,and the partitioning between these time scales is important for modeling soil water in a climate model.Different time scales are imposed on evapotranspiration primarily because it is derived from different reservoirs with different storage capacities, from the very rapid evaporation of canopy stores to the slow removal by transpiration of rooting zone soil moisture. Runoff likewise ranges in time scale from rapid surface terms to the slower base-flow. The longest time scale losses of water determine the slow variation of soil moisture and hence the longer time scale effects of soil moisture on precipitation. This paper shows with a simple analysis how shifting the partitioning of evapotranspiration between the different reservoirs affects the variability of soil moisture and precipitation. In particular, it is concluded that a shift to shorter time scale reservoirs shifts the variance of precipitation from that which is potentially predictable to unpredictable.  相似文献   

19.
具有Horton及Dunne机制的径流模型在VIC模型中的应用(英)   总被引：20，自引：0，他引：20  
地表径流主要由蓄满(Dunne)和超渗产流(Horton)机制产生;土壤性质的空间变异性、前期土壤水、地形及降水的空间变异性导致不同的径流机制。在研究区域或模型网格内,蓄满产流及超渗产流可能同时出现,缺乏考虑任何一种机制以及土壤性质的次网格空间变率可能导致地表径流的过高或过低估计,从而影响土壤水的计算。利用Philip入渗公式用于时间压缩逼近(TCA)给出了一种径流参数化方法,该方法可以动态实现模型网格中的Horton及Dunne产流机理,它考虑了土壤空间变异性对Horton和Dunne径流的影响。该径流模型应用到基于水文原理的陆面过程模型VIC,在淮河流域及美国宾西法尼亚州的一个流域进行了测试,结果表明:新的参数化方法对地表径流和土壤水分含量的分配起着重要作用,对于改进径流和土壤水的模拟有重要意义。  相似文献   

20.
Wetlands are ecosystems of important functions in the earth??s climate system. Through relatively high evapotranspiration, they affect surface water and energy exchange with the atmosphere directly influencing the physical climate. Through CH4, CO2 and N2O fluxes, they regulate the biogeochemical cycles, indirectly influencing the physical climate. However, current models do not explicitly include the water table, present under all large and stable wetlands; model wetlands are identified as flat land with wet soil resulting from precipitation events. That is, the wetlands are only ??wetted?? from above but not from below by the high water table. Furthermore, without the knowledge of the water table position, estimates of CH4 and other gases (e.g., CO2 and N2O) are poorly constrained. We present a simple hydrologic framework for simulating wetlands based on water table depth. A synthesis of hydrologic controls on wetlands highlights the key role that groundwater plays. It directly feeds wetlands, supports surface-water fed wetlands by maintaining a saturated substrate, and links land drainage to sea level by impeding drainage in lowlands. Forced by routine climate model output (precipitation?Cevapotranspiration-surface runoff), land topography, and sea level, we simulate the present-day water table in North America at the 1?km scale. We validate the simulation with water table observations and compare regions of shallow water table to mapped wetlands. Our results show that the framework captures the salient features of wetland distribution and extent at regional and continental scales, a direct result of large-scale groundwater convergence that nourishes the lowlands even in arid climates. The low requirement of forcing and computation make the framework easy to adopt in climate and earth system models for simulating wetland responses to climate and sea level change for the present, paleo reconstructions, and future projections.  相似文献   

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