Dependence of the agcm climatology on the method of prescribing surface boundary conditions and its climatological implication |
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Authors: | Lin Zhaohui Bi Xunqiang Wang Huijun Zeng Qingcun |
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Institution: | LASG, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029,LASG, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029,LASG, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029,LASG, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029 |
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Abstract: | By using IAP 9L AGCM, two sets of long-term climatological integration have been performed with the two different interpolation
procedures for generating the daily surface boundary conditions. One interpolation procedure is the so-called “traditional”
scheme, for which the daily surface boundary conditions are obtained by linearly interpolating between the observed monthly
mean values, however the observed monthly means cannot be preserved after interpolation. The other one is the “new” scheme,
for which the daily surface boundary conditions are obtained by linearly interpolating between the “artificial” monthly mean
values which are based on, but are different from the observed ones, after interpolating with this new scheme, not only the
observed monthly mean values are preserved, the time series of the new generated daily values is also more consistent with
the observation. Comparison of the model results shows that the differences of the globally or zonally averaged fields between
these two integrations are quite small, and this is due to the compensating effect between the different regions. However,
the differences of the two patterns (the global or regional geographical distributions), are quite significant, for example,
the magnitude of the difference in the JJA mean rainfall between these two integrations can exceed 2 mm/ day over Asian monsoon
regions, and the difference in DJF mean surface air temperature can also exceed 2‡C over this region.
The fact that the model climatology depends quite strongly on the method of prescribing the daily surface boundary conditions
suggests that in order to validate the climate model or to predict the short-term climate anomalies, either the “new≓ interpolation
scheme or the high frequency surface boundary conditions (e.g., daily or weekly data instead of the monthly data) should be
introduced. Meanwhile, as for the coupled model, the daily coupling scheme between the different component climate models
( e.g., atmospheric and oceanic general circulation models) is preferred in order to partly eliminate the “climate drift”
problem which may appear during the course of direct coupling.
This research was supported by the National Natural Science Foundation of China (No.49735160) and the National Key Programme
“Research on the formation mechanism and prediction theory of heavy climatic disasters in China”. |
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Keywords: | Linear interpolation Model climatology Atmospheric general circulation model (AGCM) Surface boundary condition |
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