Dear colleagues I wonder why when I compute the number of cold days using reanalysis data am getting higher percentage over areas where we know climatologically have warmer temperatures and lower in areas where is known climatologically has cold temperatures?
Please see the attached figure for clarification.
It may depend on the baseline selected for the climatological period.
the baseline is 1976-2005. I wonder maybe because the computation of extremes identifies a cold day if the maximum temperature is less than the 10percentile of the observed maximum temperature in the record. I trying to speculate that maximum temperatures that are less than 10 percentiles could be many over areas that are known climatologically to have higher temperatures compared to areas that are known to have lower temperatures. I am trying to guess may be due to temperature variability over the areas that are known climatologically to have higher temperatures and since areas are close to the ocean, I speculate the variability could be influenced by the ocean.
I noted that the computations of extreme climate indices using the eca_functions in CDO are subject to some errors. I repeated the computation using the function provided in the guidelines for computation of extreme climate indices provided by WMO am getting different results. These results can be explained that over the ocean we normally experience cold days due to the fact that the ocean warms slowly when compared to the ocean thus the higher number of cold days over the ocean. And the lower-laying areas such as coastal areas would experience more cold days compared to the high-ground areas as higher ground warm faster during the day compared to the lower altitude areas
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