Observation and Reanalysis Studies

Last edited by Chris.Kreutzer on Tue, 04/22/2014 - 10:39

 

Arctic Clouds : several reanalysis datasets are compared with satellite observations of Arctic clouds in Alexander Chernokulsky and Igor I. Mokhov, “Climatology of Total Cloudiness in the Arctic: An Intercomparison of Observations and Reanalyses,” Advances in Meteorology, vol. 2012, Article ID 542093, 15 pages, 2012. doi:10.1155/2012/542093.

Arctic Radiation and Clouds: the Arctic cloud fraction and radiative fluxes of MERRA, CFSR, 20CR, ERA-Interim, and NCEP-DOE R2  are compared with Baseline Surface Radiation Network observations in Zib, B.J., X. Dong, B. Xi, A. Kennedy, 2012: Evaluation and Intercomparison of Cloud Fraction and Radiative Fluxes in Recent Reanalyses over the Arctic Using BSRN Surface Observations. J. Climate, 25, 2291-2305. doi:10.1175/JCLI-D-11-00147.1

Arctic Temperature Trends: Seasonal arctic temperatures and trends over the 20th century in reanalyses, reconstructions, and upper-air observations are compared in Brönnimann, S., A.N. Grant, G.P. Compo,T. Ewen, T. Griesser, A.M. Fischer, M. Schraner, and A. Stickler, 2012: A multi-data set comparison of the vertical structure of temperature variability and change over the Arctic during the past 100 years. Cli. Dyn., 39, 1577-1598, doi:10.1007/s00382-012-1291-6.

Decadal-to-Interdecadal Variability and Trend in reanalyses: Paek, Houk, Huei-Ping Huang, 2012: A Comparison of Decadal-to-Interdecadal Variability and Trend in Reanalysis Datasets Using Atmospheric Angular Momentum. J. Climate, 25, 4750-4758. doi: 10.1175/JCLI-D-11-00358.1

Hadley Circulation: Trends in the Hadley Cell intensity as diagnosed in ERA40, ERA-Interim, CFSR, JRA25, NCEP-NCAR, NCEP-DOE R2, MERRA, 20CR are compared with each other and with climate model output in Stachnik, J. P., and C. Schumacher, 2011: A comparison of the Hadley circulation in modern reanalyses, J. Geophys. Res., 116, D22102, doi:10.1029/2011JD016677.

Global land temperature trends and variations in the independent 20CR and observational station temperature datasets are shown to be very similar since 1901 in Compo, G.P., P.D. Sardeshmukh, J.S. Whitaker, P. Brohan, P.D. Jones, and C. McColl, 2013: Independent confirmation of global land warming without the use of station temperatures. Geophys. Res. Letters, in press, doi:10.1002/grl.50425. Auxiliary Material.

Global land hourly temperature dataset is developed and compared to NCEP/NCAR, ERA-40, ERA-Interim, and MERRA reanalyses in Wang, A., X. Zeng, 2013: Development of globaly hourly 0.5-degree land surface air temperature datasets. J. Climate, in press, doi:10.1175/JCLI-D-12-00682.1.

Interannual Variability in reanalyses: Paek, Houk, Huei-Ping Huang, 2012: A Comparison of interannual variability in atmospheric angular momentum and length-of-day using multiple reanalysis datasets, J. Geophys. Res., 117, D20102, doi:10.1029/2012JD018105.

Ocean Atmosphere Feedbacks in NCEP/NCAR, NCEP-DOE, ERA-40, JRA-25, CFSR, and MERRA are compared with each other and observational estimates in Kumar, A., and Z.-Z. Hu, 2012: Uncertainty in the ocean-atmosphere feedbacks associated with ENSO in the reanalysis products. Clim. Dyn., 39 (3-4), 575-588. DOI: 10.1007/s00382-011-1104-3.

Southern African precipitation in ERA-40, ERA-interim, JRA-25, MERRA, CFSR, NCEP-R1, NCEP-R2 and 20CRv2 are compared in Zhang, Q., H. Körnich and K. Holmgren, 2012: How well do reanalyses represent the southern African precipitation? Clim. Dyn., DOI: 10.1007/s00382-012-1423-z.

Tropospheric Variability in CFSR and other reanalyses: Chelliah, M., W. Ebisuzaki, S. Weaver, and A. Kumar, 2011: Evaluating the tropospheric variability in National Centers for Environmental Prediction's climate forecast system reanalysis, J. Geophys. Res., 116, D17107, doi:10.1029/2011JD015707.

Upper Tropospheric Humidity from reanalyses and satellite data are compared in Chung, E.-S., B. J. Soden, B. J. Sohn, and J. Schmetz (2013), An assessment of the diurnal variation of upper tropospheric humidity in reanalysis data sets, J. Geophys. Res. Atmos., 118, doi:10.1002/jgrd.50345.

U.S. Temperature Trends in USHCN and reanalyses (1979-2008): Temperature trends over the continental United States for the period 1979 to 2008 are diagnosed in the observations from the U.S. Historical Climate Network and compared to 20CR, ERA-Interim, CFSR, JRA25, MERRA, and NARR in Vose, R. S., S. Applequist, M. J. Menne, C. N. Williams Jr., and P. Thorne. 2012: An intercomparison of temperature trends in the U.S. Historical Climatology Network and recent atmospheric reanalyses. Geophys. Res. Lett., 39, L10703, doi:10.1029/2012GL051387.

Walker Circulation: Trends in sea level pressure are compared in ERA-Interim, ERA-40, CFSR, NCEP-NCAR, MERRA, 20CR in L'Heureux, M.L., S. Lee, and B. Lyon, 2013: Recent multidecadal strengthening of the Walker circulation across the tropical Pacific, Nature Clim Change, doi: 10.1038/nclimate1840.


Above alphabetical list by topic of papers and reanalyses.org pages that compare reanalysis and observational datasets. Use form

{Topic with link to reanalyses.org Discussion Page (or paper when page doesn't exist)}: {One sentence summary}, {citation}, digital object identifier linked to journal article or presentation.

Comments (2)

Re: Observational Studies

Dear Gil,

I hope your are doing well.

About your e-mail requesting 20CR results, we are currently working in reconstructing observational series back to the past using present observations, statistical downscaling techniques and the 20th century reanalysis.

This work is still very preliminary and before to submit any result there are many tests and checking that we need to make. For this reason we have obtained result that are raising some questions to us about the 20CR.

The encloses figure shows an example for the Mean Temperature at "Berlin-Dahlem", which is part of the ECA dataset (http://eca.knmi.nl/utils/stationdetail.php?stationid=41). For the downscaling process we have used the training period 1981-2010, and as test period from the 1881-1980. Only the test period is shown in the figure. In the upper part the means for the DJF period for each year (1880-1980) is plot. In the lower part the same for the JJA period.

In blue line corresponds to the observed values and three different downscaling techniques (green, red and light blue). These downscaling techniques are made day-by-day and using 2m temperature from the 20CR as predictor. The Pearson Correlation between the downscaled and observed monthly means are indicated in the legend.

As you can see the results turn out to be suspiciously good (especially in case of DJF) , therefore the questions that we are making is:

degree the reanalysis 2m temperatures are constrained to the observations used in the assimilation process?.
The observations from "Berlin-Dahlem" has been assimilated?
If yes, which variables have been used for this purpose?
We suppose that only MSLP has been assimilated in the 20CR this it's correct?
there is a list of observations assimilated by the 20CR specially over Europe?

These results are very promising, but before we want avoid to make wrong assumptions.

Thank you very much in advance and "Saludos desde Santander"

Antonio

Re: Observational Studies

Dear Antonio,
Great to hear from you!

The 2m air temperatures are generated by the integration of the ensemble from the analyzed states. The analyzed states are only constrained by the assimilated surface and sea level pressure observations and the boundary conditions of monthly sea surface temperatures and sea ice concentration (note the comments and issues about the sea ice in Compo et al. 2011). CO2, solar variability, and volcanic aerosols are also imposed.

Your results are consistent with others, see, e.g., http://www.esrl.noaa.gov/psd/data/20thC_Rean/pubs/
Parker, D. E., 2011: Recent land surface air temperature trends assessed using the 20th Century Reanalysis., J. Geophys. Res., doi:10.1029/2011JD016438, in press.

I'll need more information about this station than the name to find out if it was assimilated and for what period - lat, lon, elevation, WMO id. You can query the International Surface Pressure Databank version 2 at http://rda.ucar.edu/datasets/ds132.0/ to generate the list you are interested in.
You can also look at maps from https://reanalyses.org/observations/international-surface-pressure-databank (you want version 2).

Mean Sea Level Pressure and surface pressure observations are the only subdaily data assimilated.

You can also examine pre-generated maps of the SLP field and its uncertainty and the 500 hPa geopotential height field and its uncertainty, along with the station locations that were assimilated at http://www.esrl.noaa.gov/psd/data/20thC_Rean/ and go to Obtain plots of the ensemble means and spreads.

If you would, please consider posting your results to reanalyses.org (Even just put up this email and this dialogue can then preserved and expanded upon there).

Please let me know if you have additional questions. I'm happy to help.

best wishes,

gil

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