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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 />
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Geophys. Res. Lett., 34, L18709, doi:doi:<br />
10.1029/2007GL031270, 2007<br />
Kanamitsu , M., A. Kumar, H. M. H. Juang, J. K.<br />
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