Wikipedia:Sandbox

DEFINITION
The CMEMS BLKSEA_OMI_seastate_extreme_var_swh_mean_and_anomaly OMI indicator is based on the computation of the annual 99th percentile of Significant Wave Height (SWH) from hourly mean model data. Two different CMEMS products are used to compute the indicator: The Multi Year Product (MYP) and the Analysis product (NRT).

• Black Sea MYP product: BLKSEA_REANALYSIS_WAV_007_006
  
• Black Sea NRT product: BLKSEA_ANALYSIS_FORECAST_WAV_007_003
  

Two different indicators constitute the product:

• Map of the 99th mean percentile: It is obtained from the MYP product, the annual 99th percentile is computed for each year of the product. The percentiles are temporally averaged in the whole period (2002-2017).
  
• Anomaly of the 99th percentile in 2018: The 99th percentile of the year 2018 is computed from the NRT product. The anomaly is obtained by subtracting the percentile in 2018 and the mean percentile.
  

CONTEXT
The SEASTATE SWH extreme variability indicator is based on the computation of the 99th percentile (that represent approximately the 1% highest values of SWH) from model results, following the same approach applied by Woodworth and Blackman (2004) to extreme sea levels. This method determines changes in the frequency distribution of the measured variables.
The indicator is defined following the steps of other indicators oriented to monitor the variability of extreme events (Pérez Gómez et al., 2016; Pérez Gómez et al., 2018, Staneva et al., 2014). More details and full scientific evaluation can be found in the CMEMS Ocean State Report 3 (OSR3, Alvarez Fanjul et al., 2019).

CMEMS KEY FINDINGS
In the Black Sea, the 99th mean percentile for 2002-2017 shows a well-known pattern demonstrating that the highest values of the mean annual 99th percentile are in the areas where high winds and long fetch are simultaneously present. The mean extreme values in the region tend to be largest in the western Black Sea, with values as high as 3.5 meters. Values in the eastern part of the basin are around 2.5 m (Staneva et al. 2019a, and 2019b).
The anomaly of the 99th percentile in 2018 is mostly negative with values down to ~-45 cm. The highest negative anomalies for 2018 are observed in the southeastern area where the multi-year mean 99th percentile is the lowest. The highest positive anomaly of the 99th percentile in 2018 are located in the southwestern Black Sea. In consequence, the anomaly values for 2018 show latitudinal gradients with higher positive values along the southwestern and southeastern Black sea coast and negative ones in the north-western and eastern Black Sea. The map of anomalies for 2018, presenting alternate bands of positive and negative values depending on latitude, is consistent with the yearly west-east displacement of the tracks of the largest storms.

REFERENCES

• Álvarez Fanjul E, Pascual Collar A, Pérez Gómez B, De Alfonso M, García Sotillo M, Staneva J, Clementi E, Grandi A, Zacharioudaki A, Korres G, Ravdas M, Renshaw R, Tinker J, Raudsepp U, Lagemaa P, Maljutenko I, Geyer G, Müller M, Çağlar Yumruktepe V. Sea level, sea surface temperature and SWH extreme percentiles: combined analysis from model results and in situ observations, Section 2.7, p:31. In: Schuckmann K, Le Traon P-Y, Smith N, Pascual A, Djavidnia S, Gattuso J-P, Grégoire M, Nolan G, et al. 2019. Copernicus Marine Service Ocean State Report, Issue 3, Journal of Operational Oceanography, 12:sup1, S1-S123, DOI: 10.1080/1755876X.2019.1633075
  

• Pérez-Gómez B, Álvarez-Fanjul E, She J, Pérez-González I, Manzano F. 2016. Extreme sea level events, Section 4.4, p:300. In: Von Schuckmann K, Le Traon PY, Alvarez-Fanjul E, Axell L, Balmaseda M, Breivik LA, Brewin RJW, Bricaud C, Drevillon M, Drillet Y, Dubois C , Embury O, Etienne H, García-Sotillo M, Garric G, Gasparin F, Gutknecht E, Guinehut S, Hernandez F, Juza M, Karlson B, Korres G, Legeais JF, Levier B, Lien VS, Morrow R, Notarstefano G, Parent L, Pascual A, Pérez-Gómez B, Perruche C, Pinardi N, Pisano A, Poulain PM , Pujol IM, Raj RP, Raudsepp U, Roquet H, Samuelsen A, Sathyendranath S, She J, Simoncelli S, Solidoro C, Tinker J, Tintoré J, Viktorsson L, Ablain M, Almroth-Rosell E, Bonaduce A, Clementi E, Cossarini G, Dagneaux Q, Desportes C, Dye S, Fratianni C, Good S, Greiner E, Gourrion J, Hamon M, Holt J, Hyder P, Kennedy J, Manzano-Muñoz F, Melet A, Meyssignac B, Mulet S, Nardelli BB, O’Dea E, Olason E, Paulmier A, Pérez-González I, Reid R, Racault MF, Raitsos DE, Ramos A, Sykes P, Szekely T, Verbrugge N. 2016. The Copernicus Marine Environment Monitoring Service Ocean State Report, Journal of Operational Oceanography. 9 (sup2): 235-320. http://dx.doi.org/10.1080/1755876X.2016.1273446
  

• Pérez Gómez B., De Alfonso M., Zacharioudaki A., Pérez González I., Álvarez Fanjul E., Müller M., Marcos M., Manzano F., Korres G., Ravdas M., Tamm S. 2018. Sea level, SST and waves: extremes variability. In: Copernicus Marine Service Ocean State Report, Issue 2, Journal of Operational Oceanography, 11:sup1, Chap. 3.1, s79–s88, DOI: https://doi.org/10.1080/1755876X.2018.1489208
  

• Staneva J, Wahle K, Koch W, Behrens A, Fenoglio-Marc L, Stanev E (2016) Coastal flooding: impact of waves on storm surge during extremes – a case study for the German Bight, Nat. Hazards Earth Syst. Sci., 16, 2373-2389, doi:10.5194/nhess-16-2373-2016Staneva
  

• Staneva, J., Behrens, A. and Groll, N. (2014) Recent Advances in Wave Modelling, Die Küste 81/2014, 233 – 254
  

• Staneva, J. Behrens, A., Gayer G, Ricker M. (2019a) Black sea CMEMS MYP QUID Report
  

• Staneva J, Behrens A., Gayer G, Aouf A., (2019b). Synergy between CMEMS products and newly available data from SENTINEL, Section 3.3, In: Schuckmann K,et al. 2019. Copernicus Marine Service Ocean State Report, Issue 3, Journal of Operational Oceanography, DOI: 10.1080/1755876X.2019.1633075
  

• Woodworth PL, Blackman DL. 2004. Evidence for systematic changes in extreme high waters since the mid-1970s. Journal of Climate: 1190–1197