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212<br />

3. Results<br />

I. Meinke, J. Roads, and M. Kanamitsu (2007) compared<br />

gridded observations of the Global Precipitation<br />

Climatology Project (GPCP) and the Global Precipitation<br />

Climatology Center (GPCC), as well as CEOP reference site<br />

precipitation observations with the RSM simulated<br />

precipitation for the first half of the CEOP Enhanced<br />

Observation Period (EOP) III (October 2002 to March<br />

2003). After estimating the uncertainty ranges of both the<br />

model and the observations, model deficiencies were<br />

obtained for almost all model domains in terms of the<br />

amount of simulated precipitation. Although the RSM is<br />

able to accurately simulate the seasonal evolution and spatial<br />

distribution of precipitation, the RSM has an almost uniform<br />

positive bias (i.e., RSM values are greater than observed<br />

values) over almost all the domains. Most of the positive<br />

bias is associated with convection in the Intertropical<br />

Convergence Zone (ITCZ) or monsoonal convection in<br />

Southeast Asia. Predicted stratiform precipitation is also<br />

excessive over areas of elevated topography. As the control<br />

simulations used a Relaxed Arakawa-Schubert scheme<br />

(RAS), sensitivity tests with three additional convection<br />

schemes were then carried out to assess whether the<br />

simulations could be improved. The additional convection<br />

schemes were: 1) the Simplified Arakawa-Schubert scheme<br />

(SAS); 2) the Kain-Fritsch scheme (KF); and 3) the National<br />

Centers for Atmospheric Research (NCAR) Community<br />

Climate Model (CCM) scheme. The precipitation simulation<br />

was significantly improved for almost all domains when<br />

using either the KF scheme or the SAS scheme. The best<br />

simulations of ITCZ convective precipitation and Southeast<br />

Asian monsoon convective precipitation were achieved<br />

using the SAS convection scheme.<br />

B. Rockel and B. Geyer (2008) perfomed similar<br />

comparison as I. Meinke et al. but with the regional climate<br />

model CLM. As expected, the quality of the simulations for<br />

temperate and continental climates is similar to those over<br />

Europe. Tropical climates, however, display systematic<br />

differences with a land-sea contrast. Here, precipitation is<br />

overestimated over warm oceans and underestimated over<br />

land. Another similarity in all regions is the positive bias in<br />

precipitation occurring over high and narrow mountain<br />

ranges which stand perpendicular to the main wind<br />

direction. In these cases, the CLM produces higher<br />

precipitation values than those given in the Global<br />

Precipitation Climatology Project (GPCP) data set. A<br />

comparison to three other regional climate models indicates<br />

that the findings are not CLM-specific. It also stresses the<br />

major role of the convection scheme in tropical regions. The<br />

study confirms the assumption that in order to gain optimal<br />

results, one standard model setup is not appropriate for all<br />

climate zones.<br />

Dominique Paquin (Ouranos) has looked at a mini-ensemble<br />

of ICTS runs for the large Asia/Himalaya domain. In<br />

addition to the requested simulations over 7 domains,<br />

supplementary simulations with the CRCM over the GAME<br />

domain (Asia) were generated with the aim of estimating the<br />

internal variability of the model. This estimation is needed<br />

to assess how much of the inter-model variance observed in<br />

this domain can be explained simply by model internal<br />

variability (sensitivity to initial conditions), rather than<br />

model configuration differences.<br />

Two different configurations were used: a) the standard<br />

configuration of the model that includes spectral nudging of<br />

the horizontal wind in the higher levels of the atmosphere,<br />

and b) a configuration without spectral nudging. Each<br />

configuration was run twice with different initial dates (twin<br />

simulations).<br />

The internal variability responses of the two<br />

configurations are evaluated for temperature and<br />

precipitation over observation points. Time series and<br />

diurnal cycle are studied. Results show that at some<br />

locations internal variability for simulations without<br />

spectral nudging can be as large as are the differences<br />

between different model configurations or other models.<br />

Z. Kodhavala (University of Quebec) and others compared<br />

MOLTS data of ICTS regional model results with CEOP<br />

reference sites observations with respect to frequency<br />

distributions and diurnal cycle.<br />

B. Gutowski (Iowa State University) and others performed<br />

studies on the diurnal cycle.<br />

References<br />

Christensen , , J. H., T. R. Carter, M. Rummukainen, and<br />

G. Amanatidis, Evaluating the performance and utility<br />

of climate models: the PRUDENCE pro ject, Climatic<br />

Change, 81, 1–6, doi:10.1007/s10584-006-9211-6,<br />

2007<br />

Druyan , L., M. Fulakeza, and P. Lonergan, Spatial<br />

variability of regional model simulated June-<br />

September mean precipitation over West Africa,<br />

Geophys. Res. Lett., 34, L18709, doi:doi:<br />

10.1029/2007GL031270, 2007<br />

Kanamitsu , M., A. Kumar, H. M. H. Juang, J. K.<br />

Schemm, W. Q. Wang, F. L. Yang, S. Y. Hong, P. T.<br />

Peng, W. Chen, S. Moorthi, and M. Ji, NCEP<br />

dynamical seasonal forecast system 2000, Bulletin of<br />

the American Meteorological Society, 83 (7), 1019–<br />

1037, 2002.<br />

Koike, T., The coordinated enhanced observing period –<br />

an initial step for integrated global water cycle<br />

observation, WMO Bulletin, 53, 9, 2004<br />

Meinke, I., J. Roads, and M. Kanamitsu, Evaluation of the<br />

RSM Simulated Precipitation During CEOP, Vol.<br />

85A, pp.145-166, 2007.<br />

Paeth , H., K. Born, R. Podzun, and D. Jacob, Regional<br />

dynamical downscaling over West Africa: Model<br />

evaluation and comparison of wet and dry years,<br />

Meteorol. Z., 14, 349–367 2005<br />

Rockel , B., I. Meinke, J. Roads, W. J. Gutowski, Jr., R.<br />

W. Arrit, E. S. Takle, and C. Jones, The Inter-CSE<br />

Transferability Study, CEOP Newsletter, 8, 4–5, 2005<br />

Rockel, B. and B. Geyer, 2008: The performance of the<br />

regional climate model CLM in dierent climate<br />

regions, based on the example of precipitation,<br />

Meteorol. Z., Volume 12, Number 4, 487-49<br />

Takle, , E. S., K. Roads, B. Rockel, W. J. Gutowski, Jr., R.<br />

W. Arrit, I. Meinke, C. G. Jones, and A. Zadra,<br />

Transferability intercomparison: An opportunity for<br />

new insight on the global water cycle and energy<br />

budget, Bul l. Amer. Soc, 88, 375–384, 2005<br />

Vizy E. K., and K. H. Cook (2002), Development and<br />

application of a mesoscale climate model for the<br />

tropics: Influence of sea surface temperature<br />

anomalies on the West African monsoon, J. Geophys.<br />

Res., 107(D3), 4023, doi:doi:<br />

10.1029/2001JD000686., 2002

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