1. Brief  description:

The data values for U/V component parameters on the pressure levels are often clearly wrong (e.g. the maximum (global) value of U component is in one case -14.4178 m/s  which is not in the allowed interval [1,250] verified by the ECMWF's checking tool). That error was acknowledged by KMA and it was tried to fix it in some forecast outputs.

2. Recommendation:

Users should consider it when using KMA wind component fields on the pressure levels in both real-time and reforecast outputs.

1. Brief  description:

The data fields of geopotential on pressure levels 500 hPa and higher are wrong as per attached examples since the 29 March, 2017.

2. Recommendation:

Wait for fix in both real-time and reforecast outputs.

1. Brief  description:

Wrong soil initial data has been used in the real-time forecasts. Please refer to the below graphs and maps illustrating the issue (see soil initial fields and comparison of forecast anomalies).

2. Recommendation:

If KMA real-time data from the given runs was downloaded in the period 9-25.6.2019, it should be deleted and the correct version of the data downloaded again.

1. Brief  description:

See an illustration of the impact of the acknowledged issue in this document.

1. Brief  description:

Periods of bugs:

• Real-time forecasts data from JMA from 1st January 2015 to 15th March 2017
• Full re-forecasts data for the model version: 2014-03-04

See an illustration of the impact of the acknowledged issue in this document.

1. Brief  description:

All S2S parameters were affected in that period. The corrected data was re-archived on June 17 2016.

The problem on the provider's side was caused by a bug in the last versions of EMOS and MARS (issued in March) that was avoided by using the previous version of MARS.

2. Recommendation:

1. Brief  description:

10-meter wind fields (zonal and meridian) are effectively wrong.

2. Recommendation:

Update on  03-11-2017:

Our 'ssrd' field is actually correct. The issue described last month only concerns our seasonal forecast system, but not our S2S system.

1. Brief  description:

All ssrd data is affected  (values are much too high; it comes from a post-processing issue where the direct downward solar radiation has been mistakenly added to the total (i.e. direct + diffuse) downward solar radiation). The issue will be neither fixed in the past re-forecasts nor in the past forecasts as it would require excessive work. It has not been fixed in new forecasts either in order to avoid inconsistencies with the re-forecast and previous forecasts.

2. Recommendation:

1. Brief  description:

Some coastal grid points may display unrealistic Tmax values. All of  the spurious Tmax points are flagged as being ocean points based on the POAMA*'s land-sea mask.

2. Recommendation:

To eliminate the spurious values, use Tmax  over land points only,  based on POAMA's land-sea mask .

* POAMA stands for Predictive Ocean Atmosphere Model for Australia.

1. Brief  description:

The sea-ice cover data in the BoM re-forecasts is incorrect. The climatological evolution of sea ice in the BoM re-forecats is for 1 January through to early March (62 day re-forecasts) for all start dates. Therefore, the sea ice coverage is wrong in the S2S archive,  except for the forecasts that start on or near 1 January

2. Recommendation:

It is recommended to not download the BoM sea-ice cover re-forecast data until the correct data has been fully uploaded in the ECMWF S2S data server. There will be an announcement when the problem has been fixed.

1. Brief  description:

Due to technical problem related to data encoding, 3 parameters could have incorrect values (very high maximum):

• Convective precipitation (only step +24h)
• Total precipitation (only step +24h)
• Snow depth water equivalent (not only step +24h)

2. Recommendation:

Users should consider the issue when using affected parameters. The issue will be fixed only in the next planned model version ACCESS-S2 (implemented probably later in 2020)

1. Brief  description:

The sea-ice cover data in the CMA re-forecasts was incorrect in the ECMWF S2S database prior to 31st March 2016. CMA confirmed that there was a problem in their data processing procedure which main effect was to have sea-ice values equal to 0 or 1 instead of covering the range 0 to 1.

The correct data was replaced in the ECMWF S2S database on 31st March 2016.

2. Recommendation:

For users that have downloaded CMA's sea-ice cover reforecast prior to 31st March 2016, we recommend to download it again.

1. Brief  description:

CMA has informed us that the real-time forecast for 2nd to 5th January 2015 and 2016 had an issue with the initial fields used. They have corrected the initial conditions and re-run those dates. We have validated the dataset and we have replaced the data in the ECMWF S2S database.

2. Recommendation:

1. Brief  description:

The data values for snow density are very different to other models. According to CMA the reason is that their model produces very little amount of snow. The checked extremes of the snow density have to been relaxed because of that specifically for CMA data.

2. Recommendation:

Users should consider it when using CMA snow density data

1. Brief  description:

The CMA reforecast after model change in November 2019 were wrongly encoded as the fixed type. Since the run 2020-06-25 the encoding was fixed to the on-the-fly type. The period Nov 2019 - Jun 2020 will need to be fixed so that all reforecast data is encoded the same way (on-the-fly type, not fixed one)

2. Recommendation:

Users should be aware of that situation, when CMA reforecast encoding is mixed until the fix is completed for the  whole period. The affected reforecast data (2019-11-11....2020-06-22) can be re-downloaded if needed to have consistent encoding. A simple fix can be applied also on user's side on already downloaded affected data. Please contact us for more details if needed.

1. Brief  description:

The sea-ice values from two hindcast years 2016 and 2017 are not correct in all Thursday's ECCC hindcasts outputs in the period 20.9.-13.12. 2018. Other hindcast years were not affected.

2. Recommendation:

Users should not use the affected data.

1. Brief  description:

See an example of meridional wind at 200 hPa for the ECCC forecast initialized on 7 Nov. 2019 (incorrect contours  around 40E and 200E). This interpolation error affects both real-time and reforecast data.

2. Recommendation:

If you downloaded the affected data before 18 May 2020, get the fixed data available in the archive now instead.

1. Brief  description:

There is an issue in the "accumulated" fields at day 16 which occurs when the IFS model resolution changes. This creates a discontinuity in the data (it can be seen also in the data on the native model grid so it's not specifically a result of the regridding to the 1.5 degree S2S resolution) which manifests itself when one "deaccumulates" the data to create six hourly accumulations for example. Specifically, one will see discontinuities between the (T+360 - T+354) and (T+366 - T+360) accumulations (most people note large negative total precipitation values but it also affects the radiation parameters).

2. Recommendation:

Users should consider that issue when using the accumulated fields.

Regrettably, there is not much it can be do about this for the S2S data which has already been regridded from the native model grid to a 1.5 degree.  It would need the deaccumulation to be performed using two different values at T+360, one based on the higher resolution grid which is  used to compute  (T+360 - T+354) and one on the lower resolution grid which is used to compute  (T+366 - T+360).

Read more about the issue:

• MARS FAQ#HowcanIcomputetheaccumulationusingdatafromtheoverlapstream? (how to avoid it in standard IFS outputs, not in S2S ones)
• ECMWF Newsletter No. 108 - Summer 2006 (pp 14-20) (discussion of the problem in The ECMWF Variable Resolution Ensemble Prediction System (VAREPS))

1. Brief  description:

Four hindcast runs on 13., 17., 20. and 24.6. 2019  had to be re-computed and re-archived  after ECMWF model upgrade to the new cycle 46r1 on June 11 to have both types of forecasts for S2S archive, real-time and hindcast, produced by the new model version. This problem could happen because the hindcasts are computed well in advance before the actual real-time date. 

2. Recommendation:

If ECMWF hindcast data from the given runs was downloaded in the period 30.5.-25.6.2019, it should be deleted and the correct version of the data downloaded again.