2011-09-21 06:58:43ERA-Interim Extended. Comparison with UAH and NCDC
Robert Way

robert_way19@hotmail...
134.153.162.53

Hi all, ERA-Interim has been extended back to 1979 (h/t Albatross).

Here is a comparison with a satellite and instrumental dataset. Of note, ERA-Interim shows a slower warming rate than both UAH and NCDC.



Also worth noting how absurd the temperature response is from UAH to El Nino's. Any thoughts on why it occurs during El Nino's and not La Nina's to the same degree. Could it be that where the radiance of oxygen molecules is being measured then it is impacted during El Nino's by the amount of water vapor that is in the air due to evaporation?

2011-09-21 08:24:27
dana1981
Dana Nuccitelli
dana1981@yahoo...
64.129.227.4

Can you give a little background about exactly what ERA-Interim is?

2011-09-21 09:15:38
Albatross
Julian Brimelow
stomatalaperture@gmail...
199.126.232.206

Thanks Robert!!

2011-09-21 17:54:05
MarkR
Mark Richardson
m.t.richardson2@gmail...
134.225.187.197

dana: ERA-Interim is a reanalysis product, there are quite a few about. It's published by the European Centre for Medium Range Weather Forecasting (ECMWF, might have got the exact name a bit wrong :p ) and in simple terms it's using a numerical weather prediction model (the forecasting type) to 'fill in the gaps' between observations.

 

Let's say that you want to model snow at a point where there isn't a weather station, or total atmospheric radiation when you don't have an infinite number of weather stations, how do you 'fill in' the missing data?

Weather forecasters use a physics based forecasting model (the same stuff that provides the 'guts' to GCMs) combined with 'data assimilation' (a fancy word for initial conditions from observations followed by weighting of the observations versus the model using Bayesian statistics).

This is an 'analysis' used in forecasting. Models keep getting better with time though, so a 'reanalysis' is where they do all of that assimilating the met data (and sometimes other stuff iirc) for loads of years in the past all over again using a consistent, single model.

ERA-40 was the old version, ERA-Interim uses a more up to date model and should be 'better'. And is probably more high resolution?

 

So you run the model for climate-model lengths of time, but only in tiny steps of 6-24 hours at a time, 'resetting' it to the reality at every step. This should work because the models are very good out to that sort of time span.

 

 

 

They provide the complete data that scientists often need to work with.

2011-09-21 22:31:09
MarkR
Mark Richardson
m.t.richardson2@gmail...
192.171.166.133

Another thing: the model that does well in the Trenberth rebuttal to Spencer is ECHAM5, which is the ECMWF one. It's based on the ECMWF weather prediction models, not sure if it's used in ERA-Interim or not...

2011-09-22 02:45:54
dana1981
Dana Nuccitelli
dana1981@yahoo...
64.129.227.4

Cool, thanks Mark.  So the ECMWF model is good at simulating ENSO then?

2011-09-22 20:39:38
MarkR
Mark Richardson
m.t.richardson2@gmail...
192.171.166.133

I just asked my office mate who's tracking extratropical storms in reanalyses and the CMIP5 runs. He's generally clued up on this so I'd trust him (although if you're gonna write anything do check the references :P ).

 

ECHAM5 is one of the best GCMs and does simulate ENSO pretty well (that's what Trenberth says at RC and in the paper too). He thinks it's based on the same core as the ECMWF Forecasting model, but the forecast model's updated every 6 months because a full ECMWF team works on it. ERA-Interim uses a single version of the forecast model, I'm not sure which.

I'd expect there to be not too much difference between the versions used in the latest reanalysis, the latest ECHAM and the ECF models. I should know more soon because I'm going to take my first plunge into ERA-Interim data next week!