VEMAP 1: U.S. CLIMATE CHANGE SCENARIOS BASED ON MODELS WITH INCREASED CO2

The Vegetation/Ecosystem Modeling and Analysis Project (VEMAP) is an ongoing multiinstitutional, international effort addressing the response of biogeography and biogeochemistry to environmental variability in climate and other drivers in both space and time domains. The objectives of VEMAP are the intercomparison of biogeochemistry models and vegetation type distribution models (biogeography models) and determination of their sensitivity to changing climate, elevated atmospheric carbon dioxide concentrations, and other sources of altered forcing. Climate scenarios from eight climate change experiments are included in the data set. Seven of these experiments are from atmospheric general circulation model (GCM) 1xCO2 and 2xCO2 equilibrium runs. These GCMs were implemented with a simple "mixed-layer" ocean representation that includes ocean heat storage and vertical exchange of heat and moisture with the atmosphere, but omits or specifies (rather than calculates) horizontal ocean heat transport. The eighth scenario is from a limited-area nested regional climate model (RegCM) experiment for the U.S. which was supported by the Model Evaluation Consortium for Climate Assessment (MECCA). The CCC and GFDL R30 runs are among the high resolution GCM experiments reported in IPCC (1990). Changes in monthly mean temperature and relative humidity were represented as differences (2xCO2 climate value - 1xCO2 climate value) and those for monthly precipitation, solar radiation, vapor pressure, and horizontal wind speed as change ratios (2xCO2 climate value/1xCO2 climate value). GCM grid point change values were derived from archives at the National Center for Atmospheric Research (NCAR; Jenne 1992) and spatially interpolated to the 0.5 degree VEMAP grid. Wind speed changes are for the lowest model level. For GISS runs, we calculated winds from vector components and then determined the change ratio. Values from the 60-km RegCM grid were reprojected to the 0.5 degree grid. Vapor pressure (and relative humidity) were not available for the CCC run; relative humidity changes were not determined for the RegCM experiment. A key issue in the generation of altered climates based on climate model output is the strong possibility of physical inconsistencies in the new climates. Change ratios from the NCAR archive have an imposed upper limit of 5.0, providing some constraint on these changes. An exception is that the GISS wind speed change ratios do not have this limit imposed (most GISS wind speed change ratios were less than 5). For a discussion of the utility and limitations of using climate model experiment outputs for exploring ecological sensitivity to climate change, see Sulzman et al. (1995). The 8 climate model experiments are: CCC - Canadian Climate Centre (Boer, McFarlane, and Lazare 1992) GISS - Goddard Institute for Space Studies (Hansen et al. 1984) GFDL - Geophysical Fluid Dynamics Laboratory. Three experiments: (1) GFDL R15: R15 (4.5 degree by 7.5 degree grid) runs without Q- flux corrections (Manabe and Wetherald, 1987). (2) GFDL R15 Q-flux: R15 resolution (4.5 degree by 7.5 degree grid) runs with Q-flux corrections (Manabe and Wetherald 1990, Wetherald and Manabe 1990). (3) GFDL R30: R30 (2.22 degree by 3.75 degree grid) run with Q-flux corrections (Manabe and Wetherald 1990, Wetherald and Manabe 1990). OSU - Oregon State University (Schlesinger and Zhao 1989) UKMO - United Kingdom Meteorological Office (Wilson and Mitchell 1987) RegCM (MM4) - National Center for Atmospheric Research (NCAR) nested regional climate model (climate version of the Pennsylvania State University/NCAR mesoscale model MM4; Giorgi, Brodeur and Bates 1994). Conterminous U.S. simulations were on a 60-km interval grid and were driven by 1x and 2xCO2 equilibrium GCM runs (Thompson and Pollard 1995a, 1995b). 1x and 2xCO2 RegCM runs were each 3 years in length. Climate changes were based on averages for these runs. A complete users guide to the VEMAP Phase I database which includes more information about this data set can be found at ftp://daac.ornl.gov/data/vemap-1/comp/Phase_1_User_Guide.pdf. ORNL DAAC maintains additional information associated with the VEMAP Project. Data Citation: This data set should be cited as follows: Kittel, T. G. F., N. A. Rosenbloom, T. H. Painter, D. S. Schimel, H. H. Fisher, A. Grimsdell, VEMAP Participants, C. Daly, and E. R. Hunt, Jr. 2002. VEMAP Phase I Database, revised. Available on-line from Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, U.S.A.

植被/生态系统建模与分析项目（Vegetation/Ecosystem Modeling and Analysis Project, VEMAP）是一项持续开展的多机构、国际性研究工作，旨在解析生物地理学与生物地球化学在时空维度上对气候及其他驱动因子环境变化的响应。

该项目的目标是开展生物地球化学模型与植被类型分布模型（生物地理学模型）的相互比对，并确定它们对气候变化、大气二氧化碳浓度升高及其他强迫因子改变的敏感性。本数据集包含8个气候变化试验的气候情景。其中7个试验来自大气环流模式（Atmospheric General Circulation Model, GCM）的1×CO₂与2×CO₂平衡运行结果。这些GCM采用了简单的“混合层”海洋表征方式，包含海洋热存储以及海洋与大气间的热量和水分垂直交换，但省略或指定（而非计算）海洋水平热输送。第8个情景来自美国的有限区域嵌套区域气候模型（Regional Climate Model, RegCM）试验，该试验由气候评估模型评估联盟（Model Evaluation Consortium for Climate Assessment, MECCA）支持。

CCC与GFDL R30试验属于IPCC（1990）报告中的高分辨率GCM试验。月均温度和相对湿度的变化以差值（2×CO₂气候值 - 1×CO₂气候值）表示，月降水量、太阳辐射、水汽压和水平风速的变化以变化比率（2×CO₂气候值 / 1×CO₂气候值）表示。GCM格点的变化值源自美国国家大气研究中心（National Center for Atmospheric Research, NCAR; Jenne 1992）的档案数据，并通过空间插值得到0.5°分辨率的VEMAP格点数据。风速变化对应模式最低层的结果。对于GISS试验，研究人员先从矢量分量计算风速，再确定其变化比率。60km分辨率的RegCM格点数据被重投影至0.5°分辨率格点。CCC试验未提供水汽压（及相对湿度）数据；RegCM试验未计算相对湿度变化。

基于气候模式输出构建改变后的气候场景时，一个关键问题是新气候场景极有可能存在物理不一致性。来自NCAR档案的变化比率被施加了5.0的上限，以对这些变化施加一定约束。唯一的例外是GISS风速变化比率未施加该限制（多数GISS风速变化比率小于5）。关于利用气候模式试验输出探究生态系统对气候变化敏感性的效用与局限的讨论，可参见Sulzman等（1995）的研究。

8个气候模式试验分别为：
- CCC：加拿大气候中心（Canadian Climate Centre, Boer、McFarlane与Lazare 1992）
- GISS：戈达德空间研究所（Goddard Institute for Space Studies, Hansen等1984）
- GFDL：地球物理流体动力学实验室（Geophysical Fluid Dynamics Laboratory），包含3个子试验：
1. GFDL R15：采用R15分辨率（4.5°×7.5°格点）且未进行Q通量校正的试验（Manabe与Wetherald, 1987）
2. GFDL R15 Q-flux：采用R15分辨率（4.5°×7.5°格点）且进行Q通量校正的试验（Manabe与Wetherald 1990, Wetherald与Manabe 1990）
3. GFDL R30：采用R30分辨率（2.22°×3.75°格点）且进行Q通量校正的试验（Manabe与Wetherald 1990, Wetherald与Manabe 1990）
- OSU：俄勒冈州立大学（Oregon State University, Schlesinger与Zhao 1989）
- UKMO：英国气象局（United Kingdom Meteorological Office, Wilson与Mitchell 1987）
- RegCM (MM4)：美国国家大气研究中心（NCAR）嵌套式区域气候模式（宾夕法尼亚州立大学/NCAR中尺度模式MM4的气候版本; Giorgi、Brodeur与Bates 1994）。美国本土的模拟采用60km间隔格点，驱动数据为1×和2×CO₂平衡GCM运行结果（Thompson与Pollard 1995a, 1995b）。1×与2×CO₂的RegCM试验时长均为3年，气候变化基于这两次试验的平均值。

如需获取包含本数据集更多信息的完整VEMAP第一阶段数据库用户指南，可访问ftp://daac.ornl.gov/data/vemap-1/comp/Phase_1_User_Guide.pdf。橡树岭国家实验室分布式主动存档中心（Oak Ridge National Laboratory Distributed Active Archive Center, ORNL DAAC）维护着与VEMAP项目相关的更多信息。

数据引用：本数据集的引用格式如下：
Kittel, T. G. F., N. A. Rosenbloom, T. H. Painter, D. S. Schimel, H. H. Fisher, A. Grimsdell, VEMAP Participants, C. Daly, and E. R. Hunt, Jr. 2002. VEMAP Phase I Database, revised. 可从美国田纳西州橡树岭的橡树岭国家实验室分布式主动存档中心在线获取。