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Phase 2 Transient Dynamics

VEMAP Phase 2 Transient Climate Dataset Documentation

User's Guide
Dataset Description:

Historical Climate
Climate Change Scenarios

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Data Portal
Data Use Policy
Dataset Citation



Model input datasets of historical climate and future climate scenarios were produced by the Vegetation/Ecosystem Modeling and Analysis Project (VEMAP) (Kittel et al. 1997).

Features of this database are:  

Component Climate Sets

- Canadian Centre for Climate Modeling and Analysis (model = CGCM1)
- Hadley Centre for Climate Prediction and Research, UK (model = HADCM2)



Time Step

Record Period

More Information


Transient Model Climate Input Data Development:
Historical Climate Series (TCLIMATE)

The first objective for VEMAP Phase 2 dataset development was the creation of a ~100-year gridded monthly and daily time series of climate for the conterminous United States that included realistic interannual variability. This effort was in collaboration with the NSF Geophysical Statistics Project at NCAR. Development of the dataset is reported in Kittel et al. (1997).

As in the VEMAP1 database, the historical dataset has: (1) daily and monthly versions, (2) physical consistency among variables on a daily basis, (3) consistency between climate and topography, and (4) needed input variables for VEMAP2 models (minimum and maximum temperature, precipitation, vapor pressure, and solar radiation).


Key steps in the development of the gridded, multivariate, monthly and daily historical dataset were:

(1) Input monthly datasets. Monthly mean minimum and maximum temperature (Tmo) and monthly precipitation (PPTmo) historical time series were derived from:

(a) NCDC's Historical Climate Network (HCN) monthly data from 1895 (~1200 stations)  

(b) Shorter period (e.g., 1951-1990) cooperative network monthly station data (for an additional ~6000-8000 stations)  

(c) SNOTEL site data

This merged input dataset provides a high density of stations and adequate-to-excellent spatial sampling of climate throughout most of the conterminous U.S., including at higher elevations (primarily from the SNOTEL sites).
(2) Serially-complete records. We created serially-complete 99-year monthly min/max Tmo and PPTmo records for climate stations from Step(1) using a local (moving-window) kriging model, following Haas (1990, 1995) (Kittel et al. 1997). The model imputes monthly climate anomalies where station records are discontinuous or limited in length.

(3) Spatial interpolation with topographic adjustment. The serially complete station data were then passed to Chris Daly (Oregon State University) for spatial interpolation with topographic adjustment. Min/max temperature and precipitation station data were spatially interpolated to the 0.5deg. lat/long VEMAP grid for each month in the 99-yr record using a newly expanded version of PRISM (Daly et al., in review; 2001; Daly and Johnson 1999). PRISM incorporates elevation, aspect, and other topographic information to grid temperature and precipitation data. Daly was funded for this task by USDA Forest Service Global Change Research Program.

(4) Daily temperature and precipitation generation. We generated daily min/max temperature and precipitation using a modified version of Richardson's (1981, Richardson and Wright 1984) stochastic weather generator WGEN. The version was provided by Sue Ferguson (USFS) and incorporated modifications from Rick Katz and Linda Mearns (NCAR). We further modified the code to permit separate parameterizations for wet vs. dry periods in the record (following the work of Dan Wilks).

We parameterized the model based on HCN and coop network daily station data and ran it for the VEMAP grid for the 99-yr record. The daily values were constrained by gridded monthly T and PPT data from step (3), so that the daily and monthly versions of the historical dataset represent the same climate.

As part of our quality checking process, we compared daily statistics from the gridded, generated product and station data. We found that daily frequency distributions and extremes match well for a range of climates across the domain.

(5) Estimation of solar radiation and humidity. We implemented a new version of MTCLIM (version 3; Thornton and Running 1999, Thornton et al. 2000) for VEMAP2 to create daily (and monthly) vapor pressure (VP), daytime relative humidity, total incident solar radiation (SR), and irradiance (IRR) from daily T and PPT. This version of MTCLIM includes improved estimation of radiation and humidity, as developed by Peter Thornton, Steve Running, John Kimball, and Rob Kremer (U. of Montana) (Kimball et al. 1997, Thornton and Running 1999, Thornton et al. 2000).

Generated vapor pressure fields compare well with the Marks (1990) VP climatology and simulated SR with NCDC/NREL SAMSON data.


Transient Climate Change Scenarios (TSCENARIOS)

For VEMAP2, our second major objective is to develop transient climate change scenarios based on coupled atmosphere-ocean general circulation model (AOGCM) transient climate experiments. The purpose of these scenarios is to reflect time-dependent changes in surface climate from AOGCMs in terms of both (1) long-term trends and (2) changes in multiyear (3-5 yr) to decadal variability patterns, such as ENSO.

We have processed scenarios from transient greenhouse gas experiments with sulfate aerosols from the Canadian Climate Center (CCC) and the Hadley Centre (HADCM2; Mitchell et al. 1995, Johns et al. 1997); accessed via the Climate Impacts LINK Project, Climatic Research Unit, University of East Anglia.



Daly, C., and G.L. Johnson. 1999. PRISM spatial climate layers: their development and use. Short Course on Topics in Applied Climatology, 79th Annual Meeting of the American Meteorological Society, 10-15 January, Dallas, TX. 49 pp.

Daly, C., W.P. Gibson, G.H. Taylor, GL Johnson, and P. Pasteris. In review. Towards a knowledge-based approach to the statistical mapping of climate. Climate Research.

Daly, C., G.H. Taylor, W. P. Gibson, T.W. Parzybok, G. L. Johnson, P. Pasteris. 2001. High-quality spatial climate data sets for the United States and beyond. Transactions of the American Society of Agricultural Engineers 43: 1957-1962.

Haas, T.C. 1990. Lognormal and moving window methods of estimating acid deposition. J. Amer. Stat. Assoc. 85:643-652.

Haas, T.C. 1995. Local prediction of a spatio-temporal process with an application to wet sulfate deposition. J. Amer. Stat. Assoc. 90:1189-1199.

Johns, T.C., R.E. Carnell, J.F. Crossley, J.M. Gregory, J.F.B. Mitchell, C.A. Senior, S.F.B. Tett, and R.A. Wood. 1997. The second Hadley Centre coupled ocean-atmosphere GCM: Model description, spinup and validation. Climate Dynamics 13:103-134.

Kimball, J.S., S.W. Running, and R. Nemani. 1997. An improved method for estimating surface humidity from daily minimum temperature. Agricultural and Forest Meteorology. 85:87-98.

Kittel, T.G.F., J.A. Royle, C. Daly, N.A. Rosenbloom, W.P. Gibson, H.H. Fisher, D.S. Schimel, L.M. Berliner, and VEMAP2 Participants. 1997. A gridded historical (1895-1993) bioclimate dataset for the conterminous United States. Pages 219-222, in: Proceedings of the 10th Conference on Applied Climatology, 20-24 October 1997, Reno, NV. American Meteorological Society, Boston.

Marks, D. 1990. The sensitivity of potential evapotranspiration to climate change over the continental United States. Pages IV-1 - IV-31 in: Biospheric feedbacks to climate change: The sensitivity of regional trace gas emissions, evapotranspiration, and energy balance to vegetation redistribution. Gucinski, H., D. Marks, and D.P. Turner, (eds.) EPA/600/3-90/078. U.S. Environmental Protection Agency, Corvallis, OR.

Mitchell J.F.B., T.C. Johns, J.M. Gregory, and S. Tett. 1995. Climate response to increasing levels of greenhouse gases and sulphate aerosols. Nature. 376:501-504.

Richardson, C.W. 1981. Stochastic simulation of daily precipitation, temperature and solar radiation. Water Resources Research 17:182-190.

Richardson, C.W., and D.A. Wright. 1984. WGEN: A Model for Generating Daily Weather Variables. U.S. Department of Agriculture, Agricultural Research Service, ARS-8, p 83.

Thornton, P.E., and S.W. Running. 1999. An improved algorithm for estimating incident daily solar radiation from measurements of temperature, humidity, and precipitation. Agricultural and Forest Meteorology, 93:211-228.

Thornton, P.E., H. Hasenauer, and M.A. White. 2000. Simultaneous estimation of daily solar radiation and humidity from observed temperature and precipitation: an application over complex terrain in Austria. Agricultural and Forest Meteorology, 104:255-271.

Page authors: T. Kittel, D.S. Schimel, N. Rosenbloom, H. Fisher, A. Royle, C. Daly, P. Thornton and C. Kaufman.
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