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Possible surprising change in minimum temperature in NorESM2-MM over Australia SSP126 #389

Closed oyvindseland closed 1 year ago

oyvindseland commented 1 year ago

From the noresm-ncc list.

We are undertaking dynamical downscaling the selected CMIP6 GCMs as part of the NSW and Australian Regional Climate Modelling (NARCliM) project. After a comprehensive evaluation and independence analysis, NorESM2-MM was selected as one of five best GCMs, which are being downscaled for the historical period from 1950 to 2014 and two SSPs (ssp126 and ssp370) from 1915 to 2100. For data QA purpose, we compare future projections derived from RCMs and the driving GCM.

The attached plot show the future changes in precipitation, maximum temperature, and minimum temperature for RCMs (WRF) and the driving GCM ( NorESM2-MM). The reference periods are 1981-2011 for the historical period and 2016-2039 for the future period.

Everything looks good except for the fourth row which is future changes in GCM simulated minimum temperature. The GCM projected decrease in minimum temperature for Australia in each season.

Could you please give us some suggestions on how to interpret the results?

Thanks

Fei

Dr Fei Ji (he/him) Senior Research Scientist, Atmospheric and Climate Science

oyvindseland commented 1 year ago

Forgot to added the relevant figure WRF_NorESM2-MM_R3_ssp126_d01_2016-2039_versus_1981-2011.pdf

oyvindseland commented 1 year ago

Hi

I did not have the tools to easily check the daily ESGF statistics but I checked the raw monthly mean output of the simulations.

While the change in Tmin was smaller than for Tmax I still found an increase in annual Tmin. I have attached similar plots of change in Tmin for annual mean, DJF and JJA. JJA is actually showing large areas of a slight decrease but not close to the results in the original values. Is it possible that any of the months either in the cmorized files or the analysis have been shifted? I also attached a time-series of the temperature development within the same area(5 year running mean) For simplicity I assumed 30 day months in the analysis but this should not change the results

Australiassp126difftempmin.pdf Australiassp126temp.pdf

Australiassp126difftempminJJA.pdf

Australiassp126difftempminDJF.pdf

tto061 commented 1 year ago

I suppose lower winter minima over Western Australia in particular could be caused by an increase in continental stratiform cloud, possibly linked with inversions and the particularly large SST contrast between Indian and Southern Ocean in NorESM during transient warming. Just a speculation but it can perhaps be checked for from the diagnostic output.

Thomas Toniazzo MISU Stockholms university SE-106 91 Stockholm Sverige

On 2022-11-29 15:48, oyvindseland wrote:

Hi

I did not have the tools to easily check the daily ESGF statistics but I checked the raw monthly mean output of the simulations.

While the change in Tmin was smaller than for Tmax I still found an increase in annual Tmin. I have attached similar plots of change in Tmin for annual mean, DJF and JJA. JJA is actually showing large areas of a slight decrease but not close to the results in the original values. Is it possible that any of the months either in the cmorized files or the analysis have been shifted? I also attached a time-series of the temperature development within the same area(5 year running mean) For simplicity I assumed 30 day months in the analysis but this should not change the results

Australiassp126difftempmin.pdf https://github.com/NorESMhub/NorESM/files/10114103/Australiassp126difftempmin.pdf Australiassp126temp.pdf https://github.com/NorESMhub/NorESM/files/10114108/Australiassp126temp.pdf

Australiassp126difftempminJJA.pdf https://github.com/NorESMhub/NorESM/files/10114106/Australiassp126difftempminJJA.pdf

Australiassp126difftempminDJF.pdf https://github.com/NorESMhub/NorESM/files/10114104/Australiassp126difftempminDJF.pdf

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lisesg commented 1 year ago

@oyvindseland, I'm not able to reproduce Fei's results using the cmor-ized files. Generally, tasmin is increasing over Australia for all seasons in my plots. There's regions where tasmin is slightly reduced, but these are largely situated south of Australia (except in JJA)

oyvindseland commented 1 year ago

Fei found an error in the scripts that were used. Their results align now with ours. Closing the issue