Atmosphere

Hi, Sir,

From previous comments, I konw Brightness temperature is the SST, but I'd like to know if the SST over Arctic and Antarctica are the water temperature or sea ice temperature, the trend is so different when I compare the monthly time series of SST for ERA5 and JRA55 over Arctic and Antarctica, as I understand the SST in EAR5 is for water temperature. Would you mind provide some references? Thank you for your help, I really appreciate.

best,

nenghan

Dear All:

Are there any papers that evaluate upper tropospheric wind field (~200hPa wind) for ERA-Interim, ERA5, and JRA55?

Many Thanks.

Regards,

Aaron

Dear All:

Sorry, I made a mistake in the previous post.

I don't understand why JRA55's resolution is ~55km. If it uses T319 spectral model, isn't the horizontal resolution=[earth circumference]/[320*2]=40000km/640=62.5km.

Thanks,

Aaron

Brightness temperature is actually SST. This SST comes from the COBE daily data, but is not exactly the same because it includes a parameterized diurnal cycle. So it differs from the COBE data in terms of the temporal variability as well as the resolution.

This brightness temperature is computed from surface upward longwave radiation assuming that the surface is a black body. As long as this assumption is valid, the brightness temperature can be used as skin temperature as well.

Hi, I need to know what variables (T, UV winds, surface pressure, etc.) JRA55 assimilates from land met stations and moored buoy arrays such as TAO, TRITON and RAMA. I saw on this forum that it doesn't assimilate winds from land met stations, if I understood correctly.

Also, does JRA55 assimilates any variables measured by moored buoys offshore the Spanish Atlantic coast, operated by the Spanish Agency Puertos del Estado?

Any help would be much appreciated, thanks!

Users should be aware that for 2mT, 2mq, 10m u and v and some others, that they should use the "forecast" variable and not the "analysis" variable. The WRIT pages now have both.

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Table 5 and section 3.2a "screen level analysis" of

Kobayashi, S., Y. Ota, Y. Harada, A. Ebita, M. Moriya, H. Onoda, K. Onogi, H. Kamahori, C. Kobayashi, H. Endo, K. Miyaoka, and K. Takahashi , 2015: The JRA-55 Reanalysis: General Specifications and Basic Characteristics. J. Meteorol. Soc. Japan, 93, 5-48, doi: 10.2151/jmsj.2015-001

describes the details of this "separate" analysis:

The analysis of screen-level variables (2-m temperatures, 2-m relative humidities and 10-m winds) is performed separately from the atmospheric analysis component. These variables are analyzed with a univariate 2-dimensional optimal interpolation (2D-OI). In JRA-25, departures were estimated by comparing observations with the first guess at the analysis time. In JRA-55, observations are compared with the first guess at the actual observation time and the departures are applied at the analysis time (the so-called first guess at the appropriate time (FGAT) approach). Temperature and wind observations from islands are not used because they are not necessarily representative at the grid scale of JRA-55. Determining whether an observation is from an island is based on the 0.25-degree resolution land cover data; consequently, observations from the coast are also excluded. Screen-level analysis fields are not used as initial conditions for forecasts.

Greetings

I read a recent reply to Yiyi's question (10/2017 comment #5401) regarding ERA-20C by Paul Berrisford, "For most applications you would use the monthly means of daily means. You would only use the synoptic means if you wanted to restrict your attention to a particular point in, or portion of, the diurnal cycle."

Can a month of monthly means (forecasts) and a month of synoptic means (forecasts) can be used interchangeably? Are there applications where one might be preferred? I assume that the comparison must be MODA forecast to SYN forecast, and AN to AN, if the forecasts contain only model output and the analysis contains assimilation?

-thanks in advance

Good moring!

We are working with 20CR and ERA20C on Shclimate dynamics. We observe some important differences prior to 1950 between both reanalysis. We would like to know when and where ship log data  is included in ERA20C between 1905 and 1950 south of 30S.

Thanks!

Dear, Sir/Madam

I have question about the surface downward UV radiation data (i.e., UV-B).

I found that the range of UV values extracted from ERA-INT and ERA5 is different, even though their units are the same (W/m2).

For example, in Jan 1979, global UV-B derived from ERA5 ranges from 0 to 45, but that derived from ERA-INT ranges from 20 to 130.

What is the exact difference between ERA-INT and ERA5 data on the value of the UVB?

Best

YW 

Dear All:

Are there any papers that evaluate upper tropospheric wind field (~200hPa wind) for ERA-Interim, ERA5, and JRA55?

Many Thanks.

Regards,

Aaron

How do we process ERA-Interim data in Matlab and obtain the plot for any of the parameters. Have downloaded the NetCDF file and was cable of reading the file but unable to plot the data. I am a Research Student working on Trend analysis of Total column Water Vapor.

Dear all

I am a fresh researcher and I need your help on how to retrive (extract) precipitable water vapour from ERA-interim data using matlab code

Hello,

Somebody could help me with this?

I downloaded data from the Interim ERA and forgot to rename it.
Now I know the data years, but I do not know which months each data represents.

Thank's

Laís

I used to get the last date of the monthly ERA-Interim reanalysis by going to a ERAInterim monthly webpage and noting the last month listed. Now I don't see a last month. How can I find the last month available? Is there a page that has it? Tx.

Hello,

I have a question and a quick note to those looking at the diurnal cycle of accumulated forecast parameters in general.

Let's use total precipitation as the example. I seem to be getting a few negative values for 3-hourly precipitation rate when subtracting the 3-hourly accumulated steps and dividing by the interval. It turns out that it's relatively rare and the non-negative values appear to match other results and to be of sufficient accuracy. Applying this same methodology to other accumulated parameters e.g. radiative fluxes appears to be fine. My theory is that bilinearly interpolating the accumulated precipitation (before subtraction of steps) to 1 degree by 1 degree (done by the WebAPI server) is the core of my issue. So, what would be the proper resolution and order of computation to ensure the 3-hourly precipitation rate is being calculated as intended?

My note to others looking at the diurnal cycle of ERA forecast parameters is to consider using the WebAPI so you can concatenate later forecast steps 6-18 hours from 00 and 12 UTC instead of using the first few steps 3-12, which can be affected by model spinup errors. Additionally, using forecast steps 6-18 hours provides a full diurnal cycle of model CAPE without erroneous values of zero in forecast step 3. This took me a while to figure out, and it turns out that the diurnal cycle of some parameters (e.g. OLR) appears to be less biased using the later steps.

Thanks in advance for any insight,

Kyle

Hi, I need to know what variables (T, UV winds, surface pressure, etc.) ERA-Interim assimilates from land met stations and moored buoy arrays such as TAO, TRITON and RAMA.

Also, does ERA-Interim assimilates any variables measured by moored buoys offshore the Spanish Atlantic coast, operated by the Spanish Agency Puertos del Estado?

Any help would be much appreciated, thanks!

Dear Andrew,

From the data, you could calculate the geopotential height on the model levels and interpolate the winds to 100gpm. This would give you the most accurate answer. For calculating geopotential, see equation 2.21 in Part III "Dynamics and numerical procedures" of the ERA-Interim model documentation:

https://www.ecmwf.int/sites/default/files/elibrary/2007/9220-part-iii-dynamics-and-numerical-procedures.pdf

To a first approximation the near surface model levels in ERA-Interim are at a constant height above the surface. However, that approximate height is proportional to temperature (in K), so the standard atmosphere gives slightly different results to those assuming a uniform scale height, see:

https://www.ecmwf.int/en/forecasts/documentation-and-support/60-model-levels

With the standard atmosphere, 100m is located between levels 58 and 57, though slightly closer to 57. So you could assume the standard atmosphere and interpolate between these two levels.

If you're happy with the discrepancy due to temperature, you could just use the winds at level 57, following the result from a 7km scale height.

Regards,

Paul

Hello,

I am currently doing research using ERA-Interim on hub-height winds (100 meters). ERA-Interim outputs data at model levels, one of these being model level 57 (1000 mb, or 100 m agl). This assumes a surface pressure of 1013.25 mb and scale height of the atmosphere of 7 km. Would this be an appropriate level to use to assess 100 meter winds over a large geographic area, or should alternative levels be used? The wind power law can be used to calculate 100 meter winds using winds at a lower heights as well. Or should I use geopotential heights to account for changes in pressure at 100 m agl? I assume changes in geopotential at 100 m would be fairly negligible over long periods of time.

Thanks,

Andrew

Dear Cathy,

as Paul said, there is no automatic way of checking the latest available date. The ERA-Interim release cycle is described here: https://software.ecmwf.int/wiki/display/CKB/Why+can%27t+I+download+ERA-Interim+data+for+recent+months

Regards

Karl

How can I automatically find the last date of the ERA-inerim? If I request a date past the last date, the ecmwf perl module  fails with many errors. I can look at the webpage but then I can't update automatically.

Dear Sir/Madam,

I am wondering how the CAPE in ERA-Interim data be calculated? Because I want to compared the results with other reanalysis data but most of them need us to calculate CAPE individually. Some important information such as: what level should be treated us the beginning point (1000mb? 1017mb? or the surface pressure?) Thank you for your replying.

Hi. I would like to know which type of cartographic projection does CFSR use?

Hi, I need to know what variables (T, UV winds, surface pressure, etc.) CFSR assimilates from land met stations and moored buoy arrays such as TAO, TRITON and RAMA.

Also, does CFSR assimilates any variables measured by moored buoys offshore the Spanish Atlantic coast, operated by the Spanish Agency Puertos del Estado?

Any help would be much appreciated, thanks!

Hi,

I'm George Victor, a student at Uppsala University, Sweden. I'm interested in using the arctic system reanalysis (15km) dataset for wave model simulations.

For my study, I expect to have a regular rectangular grid data. However, since ASR data is not based on regular rectangular projection, I'd like to know what projection is it based on. I'd also be grateful if you could suggest me some tools to convert the  data to rectrangular  projection. Thank you

Hello!

I would like to know if PIRATA buoy data are assimilated in NCEP and ERA5 reanalysis winds and if so which specific buoys (locations) and which parameters from the buoys are utilized. Can I also have some references to these.

Thank you.

I tried to estimate the 2m horizontal wind using the log wind profile with 10 m horizontal wind, and found it is quite different to the 2m horizontal wind provided in MERRA2 output. So, I am wondering how did you calculate the horizontal wind at 2m? Thanks.

I am unable to plot the ERA interim data in matlab can anyone guide me on how to do so.

Hi,

Recently I'd like to use MERRA2 data to do some analysis. I read some papers and knew that most output variables were calculated by

parameterizations in the GEOS-5 AGCM model it used and assimilated observations. 

May I ask how they made the output variables physically consistent? there are so many parameterizations that seem not related together.

Best,

Orrin

Hello... we are attempting to simulate the coastal flooding in Great Britain from the 1953 North Sea flood, and we are having trouble finding an atmospheric reanalysis product that provides reasonably accurate surface wind and pressure forcing for our simulations.  Our time period of interest is January 30, 1953 to February 2, 1953.  Any advice on which reanalysis product(s) would be most appropriate for our purposes would be much appreciated.

The WRIT page is a good start.

For specific countries, The World Bank has data by country but not to 2015. You might contact them and see if they have it available.

http://data.worldbank.org/data-catalog/cckp_historical_data

They use CRU data.

You could also look at the URL below  (they have different years/months available). NCEI has many datasets and could have it lesehwre. You can look/ask them.

https://www.ncdc.noaa.gov/sotc/global/201513

good luck!

Cathy

Hi

I work for a leading development NGO.  I'm writing a paper on the East Africa drought and I'm trying to get the following information, or close to it based on what's available.  I'm not up to speed with the data sets or how to use them and hence this message is a call to see if anyone would be able to lend me a hand.  I'm hoping this is a quick job for someone who has the data to hand and knows what they are doing??

[Mean annual temperatures increased from 1960-2016 by X in Kenya, X in Ethiopia and X in Somalia][would also be interested for 2015 and first few months of 2017 if available]

FYI - I've also emailed merra-questions@lists.nasa.gov to see if anyone can help with this.

Best wishes,

Tracy

Does anyone have any code samples that are newer than this one - http://www.esrl.noaa.gov/psd/data/gridded/readgeneral.F ?

I want to be able to read a reanalysis 2 file using fortran and netcdf .

hi 

i need to your data for research 

thanks 

Hello

  I'm trying to find some web-based reanalysis tools that I used to use. I need to look at average 500 mb GPH for a few months and do some correlation plots. There used to be a webtool here that I used but there has been a big reorganization.

Thanks

Jeannine

The NASA Climate Model Data Service (CDS) and the NASA Center for Climate Simulation (NCCS) has initiated a new project is called the Collaborative REAnalysis Technical Environment – Intercomparison Project (CREATE-IP). The primary object of this project is to convert the existing reanalyses to a format consistent with the CMIP5 directives which includes standardized variable names, attributes, file names and time format. The data is distributed though the Earth System Grid Federation (ESGF) in netCDF CF compliant format at: https://www.earthsystemcog.org/projects/create-ip/. Each variable is stored separately and contains all time values. The horizontal resolution of each reanalysis is unchanged from the way it was produced but guidance is provided to assist with modification and all available model levels are included. Currently, the monthly variables provided are those with a one-to-one correspondence to the CMIP5 archive. High frequency output is now being processed to provide 1 hour, 3 hour and 6 hour data for a select set of 2D and 3D variables. In addition, plans are underway to publish the O-A, O-F terms and selected observations using the same formatting.