Fig 1.
Map of study area and station locations.
Conterminous US and border area monthly average (a) mean dew point (Tdmean) stations and (b) minimum and maximum vapor pressure deficit (VPDmin and VPDmax) stations.
Fig 2.
Work flow diagram for data processing and mapping of Tdmean.
Cross-hatched boxes represent gridded data. See text for abbreviation definitions.
Fig 3.
Work flow diagram for data processing and mapping of VPDmin and VPDmax.
VPD refers to either VPDmin or VPDmax. Cross-hatched boxes represent gridded data. See text for abbreviation definitions.
Table 1.
Source, averaging interval, and number of stations used in the mapping process.
Table 2.
Monthly averages of actual and estimated vapor pressure deficit.
2003–2012 January and July averages from 100 randomly-selected ASOS stations. Actual and estimated VPD values are expressed as 5th percentile / mean / 95th percentile.
Fig 4.
Scatterplots of relationships between predictor grid and interpolated variables.
1981–2010 mean monthly (a) dew point depression (DPD) vs. minimum temperature (Tmin) for January in western Wyoming; (b) minimum vapor pressure deficit (VPDmin) vs. first-guess VPDmin for June near Las Vegas; and (c) maximum vapor pressure deficit (VPDmax) vs. first-guess VPDmax for October in San Francisco.
Table 3.
PRISM weighting algorithms and associated physiographic climate forcing factors.
Inputs to the algorithms and references on their formulation and use are included. Methods used to prepare the gridded model inputs are summarized in [8], Tables 1 and 2.
Table 4.
Values of relevant PRISM interpolation parameters.
Regression slope bounds are sometimes different among regions; values separated by forward slashes are for west, central, and east regions, respectively. See [7] and [8] for details on PRISM parameters and Table 3 for citations to details on weighting function formulations.
Fig 5.
Maps of January minimum temperature and dew point.
Conterminous US 1981–2010 mean January (a) minimum temperature (Tmin) and (b) dew point temperature (Tdmean).
Fig 6.
Maps of July minimum temperature and dew point.
Conterminous US 1981–2010 mean July (a) minimum temperature (Tmin) and (b) dew point temperature (Tdmean).
Fig 7.
Maps of dew point depression (DPD).
Conterminous US difference between the 1981–2010 mean minimum temperature and the 1981–2010 mean dew point temperature (Tmin—Tdmean) for (a) January and (b) July.
Fig 8.
Maps of mean minimum vapor pressure deficit (VPDmin).
1981–2010 mean monthly VPDmin for (a) January and (b) July.
Fig 9.
Maps of January maximum temperature and vapor pressure deficit.
Conterminous US 1981–2010 mean January (a) maximum temperature (Tmax) and (b) maximum vapor pressure deficit (VPDmax).
Fig 10.
Maps of July maximum temperature and vapor pressure deficit.
Conterminous US 1981–2010 mean July (a) maximum temperature (Tmax) and (b) maximum vapor pressure deficit (VPDmax).
Table 5.
Results of temperature and vapor pressure deficit substitution in the derivation of minimum and maximum relative humidity.
2003–2012 January and July averages from 100 randomly-selected ASOS stations. Actual and estimated RH values are expressed as a distribution: 5th percentile / mean / 95th percentile.
Fig 11.
Maps of minimum relative humidity.
Conterminous US 1981–2010 mean minimum relative humidity (RHmin) estimated from mean maximum temperature (Tmax) and mean maximum vapor pressure deficit (VPDmax) for (a) January and (b) July.
Table 6.
PRISM monthly cross-validation mean absolute errors (MAEs).
Both interpolation-only MAEs, and MAEs accounting for uncertainties in the predictor grids (denoted by CAI or CAI2), are given below. See text for details.
Fig 12.
Maps of Tdmean absolute cross-validation errors.
Errors for 1981–2010 mean monthly Tdmean in (a) January and (b) July.
Fig 13.
Maps of VPDmin absolute cross-validation errors.
Errors for 1981–2010 mean monthly VPDmin in (a) January and (b) July.
Fig 14.
Maps of VPDmax absolute cross-validation errors.
Errors for 1981–2010 mean monthly VPDmax in (a) January and (b) July.
Fig 15.
Network cross-validation MAE and bias of mean dew point depression (DPD).
By month, station network, and region, when each network is entirely eliminated from the dataset at one time: (a) MAE for each network in the central region, except for AGRIMET, which is in the western region; (b), same as panel a, except showing bias; and (c) RAWS network bias for each region. The number of stations in each network is given in Table 1.