Overview of current atmospheric reanalyses

Last edited by schuster on Fri, 02/14/2014 - 15:16


Arctic System Reanalysis (ASR): 2000-2011

The Arctic System Reanalysis (ASR), which can be viewed as a blend of modeling and observations, will provide a high resolution description in space (10-30 km) and time (3 hourly) of the atmosphere-sea ice-land surface system of the Arctic.  There are two versions of ASR:

Arctic System Reanalysis-Interim (ASR-int)
Source: The Ohio State University, Byrd Polar Research Center, Polar Meteorology Group
Time Range: 2000-2010
Assimilation: WRFDA-3DVAR
Model Resolution: 30 km, 71 sigma levels
Model Output Resolution: 30 km
Publicly Available Dataset Resolution: 30 km
Dataset Output Times and Time Averaging: 3-hourly for surface and upper air fields
Monthly means of selected variables
Here is the dataset location: http://rda.ucar.edu/datasets/ds631.4/
A new version is expected late 2012.

Arctic System Reanalysis-Final (ASR-fnl)
Source: The Ohio State University, Byrd Polar Research Center, Polar Meteorology Group
Time Range: 2000-2011
Assimilation: WRFDA-3DVAR
Model Resolution: 10 km, 71 sigma levels
Model Output Resolution: 10 km
Publicly Available Dataset Resolution: 10 km
Dataset Output Times and Time Averaging: 3-hourly for surface and upper air fields
Monthly means of selected variables
Dataset location will also be: http://rda.ucar.edu/datasets/ds631.4/
Expected available by end of 2012.

Data Access: Polar Meteorology Group

References | ClimateDataGuide

ECMWF 40 Year Reanalysis (ERA-40): Sep 1957-Aug 2002

ERA-40 is a global atmospheric reanalysis of the 45-year period 1 September 1957 - 31 August 2002. It was produced using a June 2001 version of the ECMWF Integrated Forecast Model (IFS Cy28r3). The spectral resolution is T159 (about 125 km) and there are 60 vertical levels, with the model top at 0.1 hPa (about 64 km). Observations were assimilated using a 6-hourly 3D variational analysis (3D-Var). Satellite data used include Vertical Temperature Profile Radiometer radiances starting in 1972, followed by TOVS, SSM/I, ERS and ATOVS data. Cloud Motion Winds are used from 1979 onwards. Various data from past field experiments were used, such as the 1974 Atlantic Tropical Experiment of the Global Atmospheric Research Program, GATE, 1979 FGGE, 1982 Alpine Experiment, ALPEX and 1992-1993 TOGA-COARE.

Data Access: ECMWFNCAR

References | ClimateDataGuide

ECMWF Interim Reanalysis (ERA-Interim): 1979-present

ERA-Interim was originally planned as an 'interim' reanalysis in preparation for the next-generation extended reanalysis to replace ERA-40. It uses a December 2006 version of the ECMWF Integrated Forecast Model (IFS Cy31r2). It originally covered dates from 1 Jan 1989 but an additional decade, from 1 January 1979, was added later. ERA-Interim is being continued in real time. The spectral resolution is T255 (about 80 km) and there are 60 vertical levels, with the model top at 0.1 hPa (about 64 km). The data assimilation is based on a 12-hourly four-dimensional variational analysis (4D-Var) with adaptive estimation of biases in satellite radiance data (VarBC). With some exceptions, ERA-Interim uses input observations prepared for ERA-40 until 2002, and data from ECMWF's operational archive thereafter. See Dee et al. (2011) in the references below for a full description of the ERA-Interim system.

Data Access: ECMWF | NCAR

References | ClimateDataGuide

Japanese 25-year Reanalysis (JRA-25): 1979-2004, JCDAS: 2005-present

The Japanese 25-year Reanalysis (JRA-25) represents the first long-term global atmospheric reanalysis undertaken in Asia. Covering the period 1979-2004, it was completed using the Japan Meteorological Agency (JMA) numerical assimilation and forecast system and specially collected and prepared observational and satellite data from many sources including the European Center for Medium-Range Weather Forecasts (ECMWF), the National Climatic Data Center (NCDC), and the Meteorological Research Institute (MRI) of JMA. A primary goal of JRA-25 is to provide a consistent and high-quality reanalysis dataset for climate research, monitoring, and operational forecasts, especially by improving the coverage and quality of analysis in the Asian region.  JRA-25 was conducted by JMA and CRIEPI (Central Research Institute of Electric Power Industry).  It has been continued as JCDAS (JMA Climate Data Assimilation System) operated by JMA on real time basis. The data assimilation systems of JRA-25 and JCDAS are the same.  Users can use JRA-25 and JCDAS as one continuous reanalysis dataset.

Data Access: JMA | NCAR

Homepage | Atlas | References | ClimateDataGuide

Japanese 55-year Reanalysis (JRA-55): 1958-2012,  to be extended to present

JMA has carried out the second reanalysis project named the Japanese 55-year Reanalysis (JRA-55) (nicknamed JRA Go! Go!) using a more sophisticated NWP system, which is based on the operational system as of December 2009, and newly prepared past observations. The analysis period is extended to 55 years starting from 1958, when the regular radiosonde observations became operational on the global basis. Many of deficiencies in JRA-25 have been diminished or reduced in JRA-55 because many improvements achieved after JRA-25 have been introduced. JRA-55 provides a consistent climate dataset over the last half century.

Data Access: JMA | DIAS | NCAR (Daily 3-Hourly and 6-Hourly Data) (Monthly Means and Variances) |

Homepage | References

NASA Modern Era Reanalysis for Research and Applications (MERRA): 1979-present

MERRA is a NASA reanalysis for the satellite era using a major new version of the Goddard Earth Observing System Data Assimilation System Version 5 (GEOS-5) produced by the NASA GSFC Global Modeling and Assimilation Office (GMAO). The Project focuses on historical analyses of the hydrological cycle on a broad range of weather and climate time scales and places the NASA EOS suite of observations in a climate context.

Data Access: GES MDISC | ESGF

Home Page | References | FAQ | AtlasBlog | ClimateDataGuide

NASA Modern Era Reanalysis for Research and Applications 2 (MERRA2): 1980-present

MERRA2 is a NASA reanalysis for the satellite era using a major new version of the Goddard Earth Observing System Data Assimilation System Version 5 (GEOS-5) produced by the NASA GSFC Global Modeling and Assimilation Office (GMAO). MERRA2 will assimilate observations not available to MERRA, and therefore, will provide the extension of MERRA into the future. Since there are numerous improvemnts and updates to teh data assimilaiton, model and observing system, it will be redone from the begining of wide satellite data availability and continue beyond MERRA's terminus. Production is anticipated to begin in Nov 2013 and continue for one year.

Data Access: TBD

Home Page | Blog |

NCEP Climate Forecast System Reanalysis (CFSR): 1979-present

The National Centers for Environmental Prediction (NCEP) Climate Forecast System Reanalysis (CFSR) spans 1979 to present. The CFSR was designed and executed as a global, high resolution, coupled atmosphere-ocean-land surface-sea ice system to provide the best estimate of the state of these coupled domains over this period. The T382 resolution atmospheric data spans 1979 to 2010. The current T574 analysis is an extension of the CFSR as an operational, real time CFSv2 product from 2011 into the future.

Data Access: NCEP | NCDC NOMADS | NCAR (includes real time CFSv2) | ESGF

References | ClimateDataGuide

NCEP/DOE Reanalysis II: 1979-near present

NCEP produced a second version of their first reanalysis starting from the beginning of the major satellite era. More observations were added, assimilation errors were corrected and a better version of the model was used.


References | ClimateDataGuide

NCEP/NCAR Reanalysis I: 1948-present

This reanalysis was the first of it's kind for NOAA. NCEP used the same climate model that were initialized with a wide variety of weather observations: ships, planes, RAOBS, station data, satellite observations and many more. By using the same model, scientists can examine climate/weather statistics and dynamic processes without the complication that model changes can cause. The dataset is kept current using near real-time observations.


References | FAQ | FGDC | ClimateDataGuide

NCEP North American Regional Reanalysis (NARR): 1979-near present

The NARR reanalysis was done to produce very high resolution output over the North American region. Observational inputs were similar to NCEP I with the addition of assimilated precipitation. The NARR model region was nested in a global, lower resolution model. Outputs are similar to the NCEP I and II models but with more snow, ice and precipitation related variables.


References | FAQ | ClimateDataGuide

NOAA-CIRES 20th Century Reanalysis V2 (20CR): 1871-2011

The 20th Century Reanalysis version 2 (20CRv2) dataset contains global weather conditions and their uncertainty in six hour intervals from the year 1871 to 2011. Surface and sea level pressure observations are combined with a short-term forecast from an ensemble of integrations of an NCEP numerical weather prediction model using the Ensemble Kalman Filter technique to produce an estimate of the complete state of the atmosphere, and the uncertainty in that estimate. The uncertainty is approximately inversely proportional to the density of observations. Additional observations and a newer version of the NCEP model that includes time-varying CO2 concentrations, solar variability, and volcanic aerosols are used in version 2. The long time range of this dataset allows scientists to examine better long time scale climate processes such as the Pacific Decadal Oscillation and the Atlantic Multidecadal Oscillation as well as looking at the dynamics of historical climate and weather events. Verification tests have shown that using only pressure creates reasonable atmospheric fields up to the tropopause. Additional tests suggest some correspondence with observed variations in the lower stratosphere.


References | Related Publications | ClimateDataGuide

Comments (66)

Which is best for wind related issues

So which is the best analysis for wind related long term calculations.......NCEP/NCAR reanalysis or NOAA-CIRES 20th Century Reanalysis V2 (20CR): 1871-2008

Re: Which is best for wind related issues

It depends on your needs, and which winds you are referring to. Ocean/SHem will have diffs in N/N when satellite data becomes available. 20CR is an ensemble of surface pressure only assimilation, no wind assimilation. the pressure gradients where obs are available should help the low level winds, but there is no upper level wind assimilation.

bottom line is that the 20CR is so new, you will likely have to determine this for your self, and we hope that you can share that information back here, as others may have similar questions. Be sure to search for new papers coming out and conference papers, 20CR is getting a lot of attention!

Mike Bosilovich (NASA/GMAO)

Solar irradiances in 20th Century reanalysis

Some questions regarding the 20th century reanalysis Which reconstruction of solar irradiance is used to force the model? Is the model forced with total or spectral solar irradiances? Is there a 11-yr solar cycle? Was the stratospheric one kept constant? Thank you very much.

Re: Solar irradiances in 20th Century reanalysis

The reconstruction is described in http://www.cpc.ncep.noaa.gov/products/people/wd51hd/vddoolpubs/solar_reconstruction.doc The NCEP model is forced by a spectral distribution of solar radiation. We do include the abt 11 yr cycle, even with a forecast to 2020. Not sure what is meant by the stratosphere question. Huug van den Dool (no need for anonymity on my part)

Re: Solar irradiances in 20th Century reanalysis

Thank you very much for the quick reply.

The NCEP model is forced by spectral irradiances but, if i understood correctly, the solar cycle variation refers to total solar irradiance only. This means that every spectral band of the radiation code increases equally (~0.1%) from the minimum to the maximum phase of the 11-yr solar cycle.
The last question was referring to stratospheric ozone. There is a prognostic equation for ozone, right? So, i guess there is a weak ozone variation in the course of the 11-yr solar cycle.

Stergios Misios

Re: Overview of current reanalyses

Yes, you understand correctly. The solar constant varies, but by the same % irradiance variation for each freq band. Moorthi or Yu-Tai can answer as to whether ozone varies in that set-up. Huug

related to the use of two different data set

kindly suggest me that can we take two different parameters from two different grid data set of NCEP/NCAR reanalysis 2 to calculate a variable in which both the parameters have been involved? for example-can i take skin temperature from surface data grid and all other from pressure data grid to calculate latent heat flux ?

Re: related to the use of two different data set

If I understand correctly, you would like to use data from N/N surface files and pressure level files, together, to make a new calculation of Latent heat flux? Ultimately, I don't think there is a specific reason that would prevent it. You would need to be careful about time step an grid centers (if all not identical). However, the reanalysis should produce it's own latent heat flux. Is the LE not sufficient? Can you offer more details or clarification?

Re: related to the use of two different data set

Are all the parameters in reanalyses located in the center of a grid? For example, if u,v,rh,T are at 20E, 20N, 700hPa in 1-degree resolution, does that mean it is averaged of grid 19.5-20.5E, 19.5-20.5N and centered at 700hPa?

Re: related to the use of two different data set

The typical output would provide data centered on a grid box, and at the listed pressure level. However, for certain purposes, data offset to the edges are more accurate, but these should be easily identifiable. When in doubt, check the model or system documentation for a description of the grid and data format.

Monthly uncertainy estimates of 20th CR

Has anyone worked with the uncertainties of monthly values derived from the 20th Century Reanalysis product? I know there are monthly mean values of sub-daily ensemble spread available, but these are not the same as the spread of the monthly averages calculated using each ensemble. That sentence is confusing, because I am confused! Would be very grateful for any advice or ideas.

Re: Monthly uncertainy estimates of 20th CR

Dear Linden, You are right that monthly means of sub-daily ensemble spread are not the same as the ensemble spread of the monthly averages. The "correct" spread will always only results from doing all analyses for each member separately and then analyse the spread of the results (e.g., averages, trends, any other statistics). The monthly means of sub-daily ensemble spread can only tell you something about the ensemble spread of the monthly averages if you have a way to consider the autocorrrelation. In my view, it is still valuable as an upper-limit estimation. Maybe I am too simplistic, but some part of the spread will be close to random and thus its contribution is expected to decrease with the square root of n, so the true spread of the monthly means will be lower.


Hello all,

I have a question regarding the CFSV2. UCAR website states that it is a continuation of CFSR. But is it a reanalysis like CFSR or is it an analysis? Can we consider that the quality of CFSV2 data are the same than CFSR?



Re: Overview of current reanalyses

Hello all,
I am studying applicability of met parameter (P, T & Rh) derived from reanalysis products to GPS PWV estimation. I selected NCEP R1, NCEP FNL and ERA-Interim for a decade and use the values (P, T & Rh) derived from them for inter-comparison. R1 and ERA-Interim are reanalysis products whereas FNL is operational GDAS analysis. Is it feasible to use them for inter-comparison? Any help will be highly appreciated.


Re: Overview of current reanalyses

Hello, Which analyses data is best in using the troposphere humidity. Whether NCEP/ DOE or Era Interim

Re: Overview of current reanalyses

Dear anonymous, your question would make a good subject for a paper. It is probably too general for this forum. I can say that we are reasonably confident about lower-tropospheric humidity in ERA-Interim, especially over land areas, based on the quality of the precipitation estimates generated by the model - see Dee et al QJ 2011 (http://onlinelibrary.wiley.com/doi/10.1002/qj.828/abstract). ERA-Interim humidity near the surface compares very well with independent observations - see Simmons et al JGR 2010 (doi:10.1029/2009JD012442). We have also looked at the variability of upper-tropospheric humidity and temperature in the tropics which seems reasonably good - see my presentation at the WCRP Open Science Conference in Denver last year (http://conference2011.wcrp-climate.org/orals/B4/Dee_B4.pdf) Dick


Hi all, I am studying the surface energy balance problem and using the ERA-Interim solar radiation data, the fields are accumulated from the start of the forecast, so in order to get averaged values I divided the data by the length of the forecast step as the ERA-Interim website FAQs : ( FLD( STEP2)- FLD( STEP1))/(( STEP2-STEP1)*3600) while I get some negative values which I think is impossible,so can you tell me the right to handle the accumuliate field?Thanks. X.L

Re: ERA-Inerim

In order to obtain average values from accumulated values you need to divide by the number of seconds in the STEP ie STEP*3600 because the accumulation is from the beginning of the forecast to the STEP (in hours) in question. If you require the average value from STEP1 to STEP2 then the formula you quote is correct provided that STEP2 is larger than STEP1. If you obtained netCDF data from the ECMWF data server at http://data-portal.ecmwf.int/ then you need to be aware that the data are packed, see the data FAQ at http://www.ecmwf.int/products/data/archive/data_faq.html#netcdfintegers, and that the scale_factor and add_offset vary with date, time and STEP etc.

Which reanalysis most suitable for sat. product comparisons?


I would like to compare globally gridded monthly means of cloud products derived from satellite observations (AVHRR,MODIS) with reanalysis products. I am tending towards using ERA-Interim but would be interested in the general opinion on this question. I would also be very interested in any recommendations which products to look at. I am aiming for cloud fractional coverage, cloud liquid and ice water path and possibly cloud top height. Any comments on this also wrt common traps and problems, parameters to investigate etc. are highly appreciated.



Re: Which reanalysis most suitable for sat. product comparisons?

I can't say which you should compare, as it ultimately depends on your metrics and purpose. However, direct cloud data comparisons have been tricky, in my experience, since there are inherent differences in what is observed, and how the background models compute cloud quantities. Part of this is also the motivation for data simulators (e.g. ISSCP Simulator). I would encourage you to include radiation observations into the comparison, as those should be another variable where the feedback from clouds to the atmosphere manifests.

Mike Bosilovich (NASA/GMAO)

Re: Which reanalysis most suitable for sat. product comparisons?

Thanks for your answer. You are certainly raising an important point. We might include direct radiation comparisons but the current scope of the project will not allow us to do much. Therefore, we may have to stick with direct cloud data comparisons for the time being.



Re: Overview of current atmospheric reanalyses

I'm looking for high resolution surface wind (10 metres above ground) for 5 years (2008-2012) off Western Greenland. We'd prefer something less than 20 km in spatial resolution and at least 6 or 12 hourly time steps. Is that available from any reanalysis dataset?

Re: Overview of current atmospheric reanalyses

I would say the Arctic System Reanalysis is precisely what you are looking for.
Check the status of it at the links at the top of this page. -Mike

Mike Bosilovich (NASA/GMAO)

Questions regarding ERA-Interim

I have a couple of quick questions about ERA-Interim. The documentation is a bit fuzzy on this, but as far as I can tell, the radiation scheme used in Interim is RRTM, is that correct? Also, am I reading correctly that SST and sea ice come from the NCEP analysis for years prior to June 2001, then the NOAA OISST from July 2001-December 2001, the NCEP RTG from January of 2002-January 2009 and finally OSTIA from February 2009 onwards? Thanks, Gijs de Boer

Re: Questions regarding ERA-Interim

Please take a look at http://www.ecmwf.int/research/era, specifically the links to the IFS documentation, which has all the details about the radiation scheme used in the model, and links to 'known quality issues' which include the inconsistent use of SST products.

Re: Questions regarding ERA-Interim

I did look at the documentation before posting my questions. However, I was not convinced that I had all of the answers to the questions I posed. For longwave radiation, the model documentation states: "Since cycle Cy22r3, two longwave radiation schemes are available in the ECMWF model, the pre-cycle Cy22r3 by Morcrette (1991), and the current longwave radiation transfer scheme, the Rapid Radiation Transfer Model (RRTM)." It is not stated (as far as I can tell), which version is used for the ERA-Interim runs, which is what I am trying to figure out... While those at ECMWF are likely versed in which model versions are used for the ERA-I production runs, unfortunately I'm not. If I am reading the documentation correctly, the shortwave portion of the radiative transfer scheme is described in Fouquart and Bonnel (1980), and RRTM is NOT used for shortwave radiation. As far as SST goes, the model documentation states: "For the operational ten-day forecasts, ECMWF uses the NCEP daily real-time global SST product (RTG_SST) at 0.5 degree resolution." In the Dee et al. paper, it states that ERA-Interim uses NCEP RTG between 01/02 and 01/09. I was just trying to confirm that this is the case, given the documentation's description. Thanks for providing the hint about searching under the "known quality issues" section, where what I describe above appears to be confirmed. Thanks again for any insight that folks may be able to provide on the longwave radiation scheme used for the ERA-I runs.

Re: Questions regarding ERA-Interim

Sorry about that - there is a lot of information available but unfortunately it is not all in one place, and not always clear, and it could certainly be much better organised. We tried to be thorough in Dee et al 2011, which is the basic reference for ERA-Interim. In fact it is just as you say - in ERA-Interim LW radiation is computed using RRTM while SW is still based on Fouquart and Bonnel with six spectral intervals.

Determining which observations are assimilated into reanalyes

Hello there, Does anyone know if the Greenland Climate Network (GC-Net) data from AWS stations have been incorporated into any of the reanalyses? Or does anyone know the best way I could find that out? Thanks so much!

Re: Determining which observations are assimilated into ...

I just took a quick look at the MERRA assimilated observations in Jan2000. I can see data near Summit in surface pressure, but not near Humbolt, GITS, Tunu-N or Petermann. I'm not so familiar with the stations data availability. If they were in the GTS, then they would be input. Note, that MERRA assimilates surface pressure from surface meteorology stations, not temperature, moisture or wind.

To look at this, I used MERRA's Gridded Innovations and Observations data, on openDAP at: http://opendap.nccs.nasa.gov/dods/MerraObs

It can also be downloaded from GES DISC: http://disc.sci.gsfc.nasa.gov/mdisc/data-holdings/merra-innov

These are not yet well documented.

Mike Bosilovich (NASA/GMAO)

Re: Determining which observations are assimilated into ...

Thanks for your help! I'm particularly interested in snow height, and I wanted to make sure I wasn't redundantly comparing the AWS data to a reanalysis dataset that includes the same AWS data.

Re: Determining which observations are assimilated into ...

We did not use these data in ERA-Interim - they are also not used by the ECMWF operational forecast system. Most of the Greenland station data that currently arrive at ECMWF are from coastal stations. Those inland stations could be very valuable for forecasting (and reanalysis, of course).

Re: Determining which observations are assimilated into ...

For the 20th Century Reanalysis (20CR, http://reanalyses.org/atmosphere/overview-current-reanalyses#TWENT ), you can obtain all of the observations used from the International Surface Pressure Databank version 2 ( http://reanalyses.org/observations/international-surface-pressure-databank ) for the entire global domain and time period (1871-2010) or for a subset period or region using the tools
courtesy of the Data Support Section of the Computational and Information Systems Laboratory at the National Center for Atmospheric Research from http://rda.ucar.edu/datasets/ds132.0/.

Maps of the stations available to the 20CR can be viewed at http://www.esrl.noaa.gov/psd/data/ISPD/v2.0/.
A text file with the stations available is at http://reanalyses.org/sites/default/files/groups/users/gilbert.p.compo/i... .
See the ISPD home page http://reanalyses.org/observations/international-surface-pressure-databank for more information.

Please let me know if I can of more help.

best wishes,
gil compo

Re: Determining which observations are assimilated into ...

Thank you so much! This is incredibly helpful!

Re: Overview of current atmospheric reanalyses

Hi Dears, Where can I find the list of surface station observations used in ERA-Interim? Where can I find the list of radiosonde station observations used in ERA-Interim? Thanks, Celeste

Re: High resolution reanalyses data for watershed modeling

hello there, I'm wondering if anyone out there could provide and /or confirm on the availability of ERA interim reanalysis at 0.25 degree spatial resolution and sub daily or daily temporal resolution for public access. Apparently, I read from ECMWF portal that ERA interim reanalysis data has approximately 80 km resolution. I'm interested to use a global reanalysis data to force hydrological models such as SWAT for a meso watershed with sparse hydrometeorological stations. I would appreciate if you drop me any piece of information on the availability of global reanalysis data with resolution in the order of 20 -30km at daily scale or shorter. So far I saw CFSR with 38 km which has a potential use but I'm hoping if there is more resoluted one. Many thanks, Tade

Re: High resolution reanalyses data for watershed modeling

Tade, To date, there is no global reanalysis dataset at the resolution you are requesting. See the overview table at http://reanalyses.org/atmosphere/comparison-table There are regional reanalyses that come close to your desired resolution. Again, see the table. best wishes, gil compo (University of Colorado/CIRES and NOAA/Earth System Research Laboratory/Physical Sciences Division)

Re: Overview of current atmospheric reanalyses

Has anyone worked with the uncertainties of monthly values derived from the 20th Century Reanalysis product? I know there are monthly mean values of sub-daily ensemble spread available, but these are not the same as the spread of the monthly averages calculated using each ensemble. That sentence is confusing, because I am confused! Would be very grateful for any advice or ideas.

Re: Overview of current atmospheric reanalyses

Dear Asimnicol, Your comment had spam lines, which have been deleted. At portal.nersc.gov, you can find each member of selected variables averaged to a daily mean and to a monthly mean. From this, you can construct your own ensemble spread or other statistic. Please let me know of any additional questions. best wishes, gil compo (University of Colorado/CIRES and NOAA/Earth System Research Laboratory/Physical Sciences Division)

Land veg mask

Hello, I am looking for the PFT maps used in NCEP I (and other reanalysis, but NCEP I is the first one I'd like to use)? So, the underlying classification of land grid cells according to vegetation or similar used in the reanalysis. I have had no luck finding these online so wanted to ask here? Thanks, Christopher

Re: Land veg mask

I think the files are here (monthly) ftp://ftp.emc.ncep.noaa.gov/mmb/gcp/sfcflds/test/fixed/README_albedo_gfrac.txt NCAR has ncep R1 files and lists vegetation (grib 225). I'm not sure which set of products it is in. http://rda.ucar.edu/datasets/ds090.0/#description Cathy

Re: Land veg mask

It looks like NCAR has the variable Vegetation Species for the NCEP/NCAR Reanalysis at http://rda.ucar.edu/datasets/ds090.0/#description The University of Maryland table describing the land cover for 1 degree data from which the NCEP/NCAR vegetation species is presumably derived is at http://glcf.umd.edu/data/landcover/ (after consulting with Mike Ek of NOAA). best wishes, gil compo

Re: Overview of current atmospheric reanalyses

In R1, the land model component was the OSU land model with the UMD 13-class land-use (vegetation type) data set.

Re: Overview of current atmospheric reanalyses

The main ECMWF reanalysis webpage (www.ecmwf.int/research/era) has some information about observations used in ERA-Interim, including a timeline (http://www.ecmwf.int/research/era/do/get/index/29/29?showfile=true) and a complete inventory of radiosonde observations (http://www.ecmwf.int/research/era/do/get/index/29/28). We are working on a system that will allow users to view and download all observations used in our reanalyses - stay tuned.

NARR "transports" vs. "fluxes"

I didn't quite formulate my question earlier. Let me retry. The general question is what the kg/m2 means in NARR in monthly files? My assumption is that for these "transports" that the value is an accumulation over 3hr. So, to get to a daily value of, say, ssrun, one would simply multiply by 8. And to a monthly integral just days per month. Could someone confirm this? Regards, David

Re: NARR "transports" vs. "fluxes"

David, Would you send the path to the source of the NARR data you are using? thanks, gil compo

Re: Overview of current atmospheric reanalyses

While working for estimation of IWV using GPS, I learned that the diurnal variations in GPS-IWV can be obtained if we use high resolution (better than 6 hours i.e. 3 hourly) surface temperature and pressure values. These values, in turn are required to obtain the hydrostatic delay over the GPS site for estimation of wet delay. I would really appreciate if somebody can provide information about a reanalysis product that has temporal resolution of 3 hours and spatial resolution about 100 km or better. I downloaded MERRA 3-hour product, but observations from our AWS do not match with this data for shorter scales (like diurnal variations and range of variations of parameters).

Re: Overview of current atmospheric reanalyses

Dear ndashora, It would be very helpful if you would make a Page on the site and post a figure illustrating the issue. If you do not have an account, go to https://reanalyses.org/user/register to make one. A listing of the spatial and temporal resolution of the atmospheric reanalysis datasets is given at https://reanalyses.org/atmosphere/comparison-table see the Model Output Resolution column and Publicly Available Dataset Resolution column. Links to Data Access can be found under the descriptions at https://reanalyses.org/atmosphere/overview-current-reanalyses Oh, you may want to spell out the acronym IWV. Other users refer to is as Water Vapor Path or other names.

Re: Overview of current atmospheric reanalyses

You may also be interested in the recent paper discussing diurnal variations of upper tropospheric humidity, summarized with links at https://reanalyses.org/atmosphere/assessment-diurnal-variation-upper-tropospheric-humidity-reanalysis-data-sets

Re: Overview of current atmospheric reanalyses

MERRA and CFSR have 1 hourly surface temperature and pressure. Both, I believe assimilate surface pressure, but not surface temperature. In MERRA sea surface temperature is prescribed, and in CFSR sst is analyzed. Both have horizontal resolution better than 100km.

Mike Bosilovich (NASA/GMAO)

Re: Overview of current atmospheric reanalyses

The CFSRR outputs hourly data on a 38Km (T382) grid. The user can download the data at NOAA's NCDC. Please refer to the CFSR website at: http://cfs.ncep.noaa.gov/cfsr (courtesy of Suranjana Saha, Ph.D. Physical Scientist, Global Climate and Weather Modeling Branch EMC/NCEP/NWS/NOAA)

Re: Overview of current atmospheric reanalyses

Thanks a lot to all of you who responded to my query regarding GPS based water vapor estimation and high res. data. I, indeed, am thankful to you all and at the moment feeling overwhelmed to receive four replies and all are supporting and relevant. So now, let see how all comments work-out. I would like to come back with my findings again to this forum. It has been useful to post a comment here.

Re: Overview of current atmospheric reanalyses

Is the NARR going to be run back to 1900 with 20th Century Reanalysis being used for its boundary coniditions? This would be very useful for studying regional climate and hydrologic within the early portion of the 20th Century. Thanks Paul

Re: Overview of current atmospheric reanalyses

Dear Paul, There are no plans that I know of do anything like this specifically. You may be interested in the dynamically downscaled data described in DiNapoli, S. M. and V. Misra, 2012: Reconstructing the 20th century high-resolution climate of the southeastern United States, J. Geophys. Res., 117, D19113, doi:10.1029/2012JD018303. best wishes, gil compo

Accuracy of NCEP reanalysis in summer and winter

Is NCEP reanalysis more accurate (lower bias and RMS) in summer (JJA) than in winter (DJF) in the stratosphere and troposphere of the northern hemisphere? If so, why? How about in the southern hemisphere? Thanks!

Re: Accuracy of NCEP reanalysis in summer and winter

What variables are referring to? In general, your question is a research question that depends on your interests. More broadly, the paper Kalnay, E., M. Kanamitsu, R. Kistler, W. Collins, D. Deaven, L. Gandin, M. Iredell, S. Saha, G. White, J. Woollen, Y. Zhu, A. Leetmaa, R. Reynolds, M. Chelliah, W. Ebisuzaki, W. Higgins, J. Janowiak, K. C. Mo, C. Ropelewski, J. Wang, R. Jenne, D. Joseph, 1996: The NCEP/NCAR 40-year reanalysis project, Bull. Amer. Meteor. Soc., 77, 437-470, doi: 10.1175/1520-0477(1996)077<0437:TNYRP>2.0.CO;2. describes the expected level of reliability of the various variables. With more than 10,000 papers having used the dataset, it is possible that someone has already looked into your question, but without more detail, it is difficult to provide any additional direction. Links to additional information (FAQ, ClimateDataGuide) can be found at http://reanalyses.org/atmosphere/overview-current-reanalyses#NCEP1 best wishes, gil compo U. of Colorado CIRES & NOAA Earth System Research Laboratory

Elevation of 20CR-grid points

Hi everyone, Is there a mask of the elevation of the topography of every grid point in 20CR? If yes, where can I access it? Thanks in advance for any help or suggestions!

Re: Elevation of 20CR-grid points

Dear Remo, One source is to see the files listed at http://www.esrl.noaa.gov/psd/data/gridded/data.20thC_ReanV2.monolevel.html You want the file from the table for Time-Invariant Either Geopotential Height Surface 2x2 ftp://ftp.cdc.noaa.gov/Datasets/20thC_ReanV2/time_invariant/hgt.sfc.nc or Geopotential Height Surface (gaussian grid) ftp://ftp.cdc.noaa.gov/Datasets/20thC_ReanV2/gaussian/time_invariant/hgt.sfc.nc best wishes, gil compo

Re: Elevation of 20CR-grid points

Hi Remo, The 20CR surface geometric height is contained in the file sflxgrbfg_orography.t62.grib, which can be downloaded at the following URL: http://rda.ucar.edu/datasets/ds131.1/index.html#sfol-wl-/data/ds131.1?g=309 You will need to sign in at the NCAR RDA website before downloading the file. Additionally, the ISPDv2, which was assimilated into the 20CR, contains the station elevation data and modified elevation for all stations in the ISPDv2. These data may be accessed from the NCAR RDA website at the following URL: http://rda.ucar.edu/datasets/ds132.0/ - Tom Cram

Re: Overview of current atmospheric reanalyses

Dear Tom and Gilbert, Thanks for your suggestions, that helped a lot.

Land/Sea Mask

Hi everyone, I am looking for the land sea mask for 288*145, please let me know where I can have access it. Thanks in advance

Re: Land/Sea Mask

Dear Alima, Is there a particular dataset whose land/sea mask you are trying to get? Depending on the dataset, the mask could be different. NCL could possibly be used to make a general conversion from the built-in mask http://www.ncl.ucar.edu/ but I have not test this. best wishes, gil

Vertical velocities in the ERA Interim model levels data

Hi everyone, I'm trying to understand the vertical wind velocities in the ERA Interim data set in model levels ("eta" hybrid coordinates). According to the netCDF metadata, the provided vertical velocity is in Pa.s-1 which corresponds to a vertical velocity in pressure coordinates. Hence the following question : do we have d(p)/dt instead of d(eta)/dt in the data in model levels ? Thanks for any piece of advice.

Re: Vertical velocities in the ERA Interim model levels data

Hello, the vertical velocity is indeed in Pa.s-1 (=dP/dt), regardless of the type of level (model levels, or pressure levels).

Rainfall analysis

Hi everyone, I am analyzing hourly rainfall records in many regions of the world. However, I would like to know which reanalysis data is suitable to make some comparison. Thanks in advance for any suggestions :D

Re: Rainfall analysis

Dear SA, What you are asking turns out to be a research question. Several papers have looked into this. See a list at http://reanalyses.org/atmosphere/observational-studies and http://reanalyses.org/atmosphere/inter-reanalysis-studies-0#Precipitation Please report back with what you find. best wishes, gil compo

Re: Rainfall analysis

I can't say anything specific, since your comment has very little detail about where and when you are working. One thing that will be universal when considering reanalysis precipitation is that the quantity is derived from the background model forecast of the assimilation process. So, while the environment that produces precipitation is affected by the observational analysis, precipitation relies on the model physics, and has significant uncertainty. If observations of precipitation are available, you'll want to use those, at the least, in a comparison with the reanalysis data. Some reanalyses produce 1 hourly data, and some assimilate rainfall (see the North American Regional Reanalysis). Biases and uncertainty in reanalysis precipitation depends greatly on where and when you are looking. The papers listed in the pages Gil provided are a start, but be sure to follow those that they cite as well.

Mike Bosilovich (NASA/GMAO)

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