Title: Mississippi basin averaged daily ECMWF reanalysis files: (1985-1993) Contact: Alan K. Betts Atmospheric Research, RR #3, Box 3125 Pittsford VT 05763 email: akbetts@aol.com 1.0 Abstract Key Reference Basin-scale surface water and energy budgets for the Mississippi from the ECMWF reanalysis Alan K. Betts and John H. Ball Atmospheric Research, Pittsford, Vermont Pedro Viterbo European Centre for Medium-Range Weather Forecasts, Reading, England [J. Geophys. Res., 104, 19293-19306.] This paper compares with observations the energy and water budgets for the subbasins of the Mississippi (the Arkansas-Red, the upper Missouri, the upper Mississippi, the Ohio, and the lower Mississippi and Tennessee Rivers), which were computed on-line with an hourly time scale from the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis from 1985 to 1993. The model has a significant precipitation spin-up between the analysis cycle and the 12-24 hour forecast, ranging from 24% to about 40% for the drier Missouri basin. The spin-up of the model "large-scale" precipitation ranges from 30 to 50%, roughly double that of the spin-up of the model "convective" precipitation. The model has an erroneous peak in convective precipitation near local noon, but on 2 day and monthly timescales, the 12-24 hour forecast precipitation is only 10 to 20% higher than the observed precipitation for most of the subbasins. The model runoff, which is all deep runoff from the base soil layer, is low on an annual basis, primarily because the model has very little Spring runoff. The nudging of soil water in the analysis cycle, based on 0-6 hour forecast errors in low-level humidity, plays a major role in the model liquid hydrology. The nudging term has a large annual cycle, positive in summer and negative in winter. Although nudging prevents the downward interannual drift of soil water, associated with a shortfall of precipitation in the analysis cycle, it also attempts to compensate for other errors in the model, such as errors in the seasonal cycle of evaporation and runoff, and may damp the variability of soil water. The model frozen hydrology in winter is not conservative and snowmelt is probably too small. Overall, the ECMWF reanalysis gives a valuable description of the surface energy and water balance of the Mississippi River subbasins on timescales longer than the diurnal, and at the same time, it is clear that improvements in the model physics are needed. 2.0 Detailed Data Description Files: ECMWF_1Day.txt : 8879220 bytes MissPrRo.txt : 253210 bytes Figure_1.gif : 65716 bytes The two text files are daily data from 1985 to 1993 for the energy and water budgets for the sub-basins of the Mississippi (the Arkansas-Red, the upper Missouri, the upper Mississippi, the Ohio, and the lower Mississippi and Tennessee Rivers) from the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis [ERA15], and from observations of precipitation and streamflow. The original ECMWF model data were computed on-line with an hourly time scale, but we have summed or averaged up to the daily timescale, because the model has significant precipitation errors in the diurnal timescale which largely disappear on the daily time-scale (Betts et al, 1998, 1999). This also reduces the data volume by a factor of 24. Roads and Betts (2000) compare the ECMWF and NCEP/NCAR reanalyses on a monthly timescale using these data. The basins are shown in Fig 1 (see Figure_1.gif), and Table A gives the drainage areas. These model areas were used for the basin "observed precipitation" averages, derived from the Higgins et al (1996) data. Table B gives the streamflow gauges and their drainage areas used to convert observed streamflow to mm day^-1 Description of Figure_1.gif: Five major Mississippi sub-basins, and their approximation in the ECMWF reanalysis model. Physics grid-points are shaded dots, and small squares are the data points for the Higgins et al (1996) gridded rainfall set. Table A. Mississippi sub-basin drainage areas and their model approximation. ____________________________________________________ Sub-Basin Drainage Area Model Area (km^2) (km^2) ____________________________________________________ 1 636400 677700 2 1320800 1285700 3 490200 567700 4 418000 351400 5 299100 395000 ____________________________________________________ Table B. Stream flow basins used for comparison. -------------------------------------------------------------------------------- River Basin Gauging Station Basin Area Model Area (km^2) (km^2) [basin] -------------------------------------------------------------------------------- Arkansas Van Buren, AR 389913 Red Index, AR 124397 Arkansas+Red [Sum] 514210 677700 [1] Missouri Kansas City, MO 1256656 1285700 [2] Upper Mississippi+Missouri St. Louis, MO 1805213 Upper Mississippi [Difference] 548557 567700 [3] Ohio Metropolis, IL 525765 351400 [4] Mississippi basin Vicksburg, MS 2953996 3273000 [1,2,3,4,5] 2.1 Detailed Format Description Fields in ECMWF_1Day.txt. These are all ERA15 model data. Field Name Description ---------- ----------- Basin Mississippi sub-basin identifier Year Year (-1900) Day Julian Day Month Month Swnet Net Short Wave Radiation (Wm-2) Lwnet Net Long Wave Radiation (Wm-2) LH Latent Heat of Evaporation of water (Wm-2) Lhsnow Latent Heat of Evaporation of snow (Wm-2) SH Sensible Heat (Wm-2) Tmlt Melt Energy (Wm-2) Wmlt Melt Water (Kg m-2 s-1) Lsr Large scale rain (Kg m-2 s-1) Cvr Convective scale rain (Kg m-2 s-1) Lssnow Large scale snow (Kg m-2 s-1) Cvsnow Convective scale snow (Kg m-2 s-1) Sw1few Evaporation of liquid water (Kg m-2 s-1) Sw1fen Evaporation of snow (Kg m-2 s-1) Sw1fro Surface RunOff (Kg m-2 s-1) Swdfro Deep RunOff (Kg m-2 s-1) Lsr12 12-24 hour forecast Large Scale rain (Kg m-2 s-1) Cvr12 12-24 hour forecast Convective scale rain (Kg m-2 s-1) Lssnow12 12-24 hour forecast Large scale snow (Kg m-2 s-1) Cvsnow12 12-24 hour forecast Convective scale snow (Kg m-2 s-1) Sw1few12 12-24 hour forecast Evaporation of liquid water St1 Soil Temperature(1) (K) (1, 0-7 cm) Sw1 Soil Water(1) (1, 0-7cm) Std Soil Temperature(Deep) (K) (Deep, 7-289 cm) Swd Soil Water(Deep) (Deep, 7-289 cm) Ssn Snow Depth (mm) P Surface Pressure (h Pa) DelSwd Calculated nudging term deep layer DelSw1 Calculated nudging term shallow layer P31 Level 31 Pressure (h Pa) U 2m U-Component Wind (m s-1) V 2m V-Component Wind (m s-1) T 2m Surface Temperature (K) Q 2m Specific Humidity (Kg Kg-1) Nudging 0.4 * (0.07 * DelSw1 + 2.82 * DelSwd) RNet Swnet + Lwnet (Wm-2) RAIN 3600 * 24 * (Cvr + Lsr) (mm day-1) SNOWFALL 3600 * 24 * (Cvsnow + Lssnow) (mm day-1) PRECIP RAIN + SNOWFALL (mm day-1) RAIN12 3600 * 24 * (Cvr12 + Lsr12) (mm day-1) SNOWFALL1 3600 * 24 * (Cvsnow12 + Lssnow12) (mm day-1) PRECIP12 RAIN12 + SNOWFALL12 (mm day-1) EVAP 3600 * 24 * (Sw1few) (mm day-1) MELT 3600 * 24 * (Wmlt) (mm day-1) RUNOFF 3600 * 24 * (Swdfro) (mm day-1) SOILWATER 1000 * (0.07 * Sw1 + 2.82 * Swd) (mm) Fields in MissPrRo.txt. These are basin averaged observed precipitation from Higgins et al. (1996) for all five basins in Table A, and streamflow, derived from gauges in Table B for basins 1-4 and the Mississippi at Vickburg. Year Year (-1900) Month Month Day Julian Day Precip1 basin 1 (mm day-1) Precip2 basin 2 (mm day-1) Precip3 basin 3 (mm day-1) Precip4 basin 4 (mm day-1) Precip5 basin 5 (mm day-1) Streamflow1B basin 1, Table B (mm day-1) Streamflow2B basin 2, Table B (mm day-1) Streamflow3B basin 3, Table B (mm day-1) Streamflow4B basin 4, Table B (mm day-1) StreamflowMiss Mississippi at Vicksburg, Table B (mm day-1) 3.0 Quality Control Processing No additional Quality Control (QC) was performed on this dataset by the University Corporation for Atmospheric Research/Joint Office for Science Support (UCAR/JOSS). 4.0 References. Betts, A. K., P. Viterbo and E. Wood, 1998: Surface Energy and water balance for the Arkansas-Red river basin from the ECMWF reanalysis. J. Climate, 11, 2881-2897. Betts, A. K., J.H. Ball and P. Viterbo, 1999: Basin-scale Surface Water and Energy Budgets for the Mississippi from the ECMWF Reanalysis. J. Geophys. Res., 104, 19293-19306. Higgins, R. W., J. E. Janowiak, and Y.-P. Yao, 1996: A gridded precipitation database for the United States (1963-1993), NCEP/ Clim. Predict. Cent. ATLAS 1, 47 pp.. Natl. Cent. for Environ. Predict., (Available from Clim. Predict. Cent., NCEP, Camp Springs, Maryland). Roads, J. and A. Betts, 2000: NCEP/NCAR and ECMWF Reanalysis Surface Water and Energy Budgets for the GCIP Region. J. Hydrometeorol. , 1, (Jan).