Variables meaning

[jacopovr@tiscali_it]

Good day everyone, my name is Jacopo and i'm an archaeologist, for this reason i'm not very practical with climatologist workflow so i hope you will excuse me for my very noob questions. At the moment me and some of my other colleagues of the University of Bologna are working on a model about the relations betwen the institutions of the cityes/reings of the middle est betwen 6k and 4k years BP,  and the welfare of the common folks. For this reason we have decided also to include variables, such as the medium temperature and rainfall during this time spawn which would be very important to determinate also the political fluctuations in that kind of environment. For this purpose i'm trying to extract the data of the TraCe plaeoclimatic dataset on ArcGIS, with this kind of variables to choose from (image), but i'm not able to find the meaning of most of these. I have olso tried to look for the CESM tools, but looks like it's not that simple to handle too, at least for me.Do you think using ArcGIS for the data extraction it's ok? If it is, can someone please indicates me where can i find some informations about the variables in the image? Or do you know a better methos to procede with this part of the work?I would be very grateful for any kind of suggestion. Jacopo

 

[strandwg]

I know that people have used ArcGIS with the model data. As I understand it, there is software that allows ArcGIS to use netCDF data. Information about the fields available from the TraCE simulations is at http://www.cgd.ucar.edu/ccr/TraCE/fields.html The temperature field you want is called "TREFHT" (temperature at 2 meter elevation above the surface) and for precipitation, you can use the fields "PRECC" and "PRECL", added together, to get total precipitation. Let me know of any other questions you have. 

 

[jacopovr@tiscali_it]

Thank you so much strandwg, that was exactly what i was looking for. I will give you some more details as the work goes on.Thanks again.

 

[jacopovr@tiscali_it]

I have tried to extract PRECC and PRECL data for the precipitation as you said, but no matter the chainging in the coordinates of in the timeline, the amount remains the same = 0. For the extraction i have used ArcGIS and also Panoply (Image) and from the plot we can see some colour differences that doesn't correspond to a change of value. Am i doing something wrong?Also with the temperature 2 m from the ground it gives me unlikely resoults (betwen -39 amd -3° C for the middle eastern area).

 

[strandwg]

I suspect that the reason you're seeing zeroes for PRECC and PRECL is that they tend to be very small - order 10^-7 to 10^-8 range, because the units are meters/second.

You will probably want to scale them to something more appropriate for your purposes.

Also, the arrays are fully georeferenced - there are "lat" and "lon" arrays in the netCDF files, so check and make sure you're looking at the correct region.

I'm not an expert on how ArcGIS handles netCDF files, but I asked our GIS group here and this is the response:

I think your reasoning is correct about the data values.To test this theory ask them to right click on the field in the Attribute Table in ArcMap.  Select Field Properties.  Click the Number Format: Numeric button.  Now change the number of decimal places to 10 or something like this.Now they can convert to a shapefile or even better feature class in a geodatabase, add a new field and calculate a new value based on a scale value.  

 

[jacopovr@tiscali_it]

First of all thanks for the interest.I have tried changing the scale as you have suggested, but still the precipitation index remains 0 in all the fields.

 

[jacopovr@tiscali_it]

Thanks to Ms. Jennifer B. we have solved the precipitation issue and some other questions, but still the results about the temperatures doesn't feels right for the geographical area (Mesopotamia) ranging from 230 to 270 K, way too cold for the temperature 2 m elevation above the surface, as you previously said. Is it possible that i need a different variable, like TS?