Alan F. Hamlet

•JISAO/CSES Climate Impacts Group•Dept. of Civil and Environmental Engineering

University of Washington

Overview of VIC Meteorological Forcing Data Preparation

长江流域

黄河流域

淮河流域

2604 60km×60km grid cell

Distribution of meteorological station in China

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Preprocessing Regridding

Lapse Temperatures

Correction to RemoveTemporal

Inhomogeneities

HCN/HCCDMonthly Data

Topographic Correction forPrecipitation

Coop Daily Data

PRISM MonthlyPrecipitation

Maps

Schematic Diagram for Data Processing of VIC Meteorological Driving Data

Preprocessing Regridding

Lapse Temperatures

Correction to RemoveTemporal

Inhomogeneities

HCN/HCCDMonthly Data

Topographic Correction forPrecipitation

Coop Daily Data

PRISM MonthlyPrecipitation

Maps

Preprocessing Regridding

Lapse Temperatures

Correction to RemoveTemporal

Inhomogeneities

HCN/HCCDMonthly Data

Topographic Correction forPrecipitation

Coop Daily Data

PRISM MonthlyPrecipitation

Maps

Schematic Diagram for Data Processing of VIC Meteorological Driving Data

Result:Daily Precipitation, Tmax, Tmin

1915-2003

Overview of Data Processing Steps•Collect observed station data and preprocess wind data

•Reformat station data to an irregularly spaced gridded file.

•Regrid the raw station information to the VIC lat lon grid.

•Quality control to remove implausible values

•Adjust gridded raw station data to remove station inhomogeneities using HCN or HCDN data sets as a standard (optional)

•Topographic adjustment of precipitation data (using PRISM data as a standard).

•Reformatting to final file format needed by VIC.

Regridding Details

Symap regridding algorithm accounts for station proximity via an inverse square weighting, but also accounts for the independence of the stations from one another.

The interpolation scheme ensures that collectively these two nearly coincident stations are assigned about the same weight as each of the other two stations.

Removing Temporal Inhomogeneities

Raw station data although containing important local information is likely to contain substantial inconsistencies through time, due to changing station locations and instruments, and especially due to different station groupings through time. Trends in the uncorrected data sets (and hydrologic simulations derived from them) are highly suspect and are likely to be dominated by these artifacts of the raw data.

By using long continuous records from the quality controlled HCN and HCCD data sets, we can correct the trends to remove these inhomogeneities through time.

Regridded Raw Coop Precipitation (Annual Mean mm)

Regridded HCN/HCCD Precipitation (Annual Mean mm)

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From Daily Coop

Monthly Mean of Coop Data is adjusted by comparing the smoothed value from HCD/HCCD with the smoothed value from the Daily Coop product.

Time Series of January Precipitation Values at Each Grid Location Smoothed in Time

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Cell 100 in (British Columbia)

Cell 2000 (Middle of the US part of the domain)

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Trends are Largely Preserved

After PRISM Topographic Adjustments

After Temporal Corrections

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Problems with Temporal Inconsistencies in Meteorological Records(S. F. Flathead River at Hungry Horse Dam, MT)

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Root square error

Comparison of adjusted vs. unadjusted VIC simulations(S. F. Flathead River at Hungry Horse Dam, MT)

Simulated vs Observed

Evaluation of Streamflow Simulations of the Colorado River at Lee’s Ferry, AZ

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Global T as a Predictive Variable for TMAX Trends Over the West

R2 = 0.62

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regression global T onlyR2 = 0.81

TMIN

Global T as a Predictive Variable for TMIN Trends Over the West

Differences in cool and warm season precipitation trends suggest different mechanisms (large-scale advective storms vs. smaller scale convective storms) and differing sensitivity to regional warming. Trends in warm season precipitation in the CRB are very different than the other regions and may function more like cool season precipitation (e.g. related to circulation rather than locally generated storms)

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Regionally Averaged Cool Season Precipitation Anomalies

PRECIP

http://www.hydro.washington.edu/Lettenmaier/gridded_data/index.html

Maurer E.P., Wood A.W., Adam J.C., Lettenmaier D.P., and Nijssen B, 2002: A long-term hydrologically-based data set of land surface fluxes and states for the conterminous United States, J. Climate, 15 (22): 3237-3251

Hamlet A.F., Lettenmaier D.P., 2005: Production of temporally consistent gridded precipitation and temperature fields for the continental U.S., J. of Hydrometeorology, 6 (3): 330-336

Access to Previously Prepared Driving Data Sets