In bias correction (Quantile Mapping), what should I do for climatic variables using R (qmap package)?
Dear reachers,
I am studying the "qmap" package in R language, to perform bias correction (Quantile Mapping). I have read the Help Documentation about "qmap" package, and all cases are based on precipitation data. These codes include common parameter——“wet.day”, which is intended for precipitation data.
What is the difference between specific R codes for different climatic variables, such as precipitation, temperature, solar, or wind speed?
I have read your article, and that's pretty good. As you mentioned, the qmap package provides many methods to explore the relationship between observed and molded values. The selected method is critical to bias correction and varied from previous studies. This might is due to differences in studied areas, global climate models (GCMs), and data scales (monthly or daily).
When I need to perform the bias correction for many climatic stations and GCMs, what should I do to find the suitable method in qmap.
Islamic Azad University Tehran Science and Research Branch
Hello.
You can use any kind of data in qmap. In fitQmap function, first choose the observed columns, second choose the forecasted columns, and then specify the method. Notice that the number of observed data columns must be equal to forecasted data columns.
In the next step, you can test the performance by using doQmap function where you choose the forecasted data and then the output from fitQmap. The output from doQmap is bias corrected data.
I recommend check the documentation of the qmap, there are many meths and different cumulate distribution function (CDF) to use, of course some CDF are better than other and depends of kind climatic data. For my experience, some distribution functions are much better when you use precipitation (for example, exponential, log-normal or the mix Bernoulli-Gamma, the last was that I used in the past). Finally, I would like to recommend my paper where I used this package in R (DOI: 10.1061/9780784480618.054), perhaps it could be of help to you. Best wishes.
Thank you for your detailed explanation of the fitQmap function.
In this function, how to set the parameter——“wet.day” for different variables? For precipitation data, the parameter should be "wet.day = TRUE". For other variables, is that "wet.day = FALSE"?
I have read your article, and that's pretty good. As you mentioned, the qmap package provides many methods to explore the relationship between observed and molded values. The selected method is critical to bias correction and varied from previous studies. This might is due to differences in studied areas, global climate models (GCMs), and data scales (monthly or daily).
When I need to perform the bias correction for many climatic stations and GCMs, what should I do to find the suitable method in qmap.
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