Geoinformatika 2018; 4(68) : 93-101

УДК 551.583.16:551.509.33-19/20-477

THE SKILL OF «NON-METHODOLOGICAL» LONG-TERM AIR TEMPERATURE AND PRECIPITATION FORECASTS IN UKRAINE

O.A. Shchehlov

krainian Hydrometeorological Institute of State Service of Emergencies and National Academy of Sciences of Ukraine,
Nayki ave. 37, Kyiv, 03028, Ukraine, e-mail: aleshcheglov@gmail.com

Purpose.  The purpose of the article is to estimate the forecast skill of «non-methodological» (persistence, random and climatological) forecasts of monthly mean air temperature and monthly precipitation over the territory of Ukraine according to the official methodology adopted in Ukraine. The aim is also to assess whether the methodology equally estimates the climatological forecast skill over a much larger area with the presence of different types of climate (within Eastern Europe).

Design/ methodology/ approach. The official methodology adopted in Ukraine was used for assessing the forecast skill. The forecast skill was estimated only on a monthly time scale.

Findings. The research has shown that random and persistence forecasts for the territory of Ukraine are much worse than climatological. The climatological forecast is the best alternative in case of absence of a methodological long-term forecast of both air temperature and precipitation. The average annual forecast skill according to the official methodology is 60,9 % for the air temperature climatological forecast. The mean absolute error of the climatological forecasts is 1,88 °C. The forecast skill of monthly precipitation is also the highest for the climatological forecast (63,4 %). The official methodology has a drawback, which is in the usage of fixed temperature gradations in a calculation. As a result, the failure to take into account the regional climate features (namely different standard deviation) leads to a different estimation of the forecasts skill. Using the NCEP/NCAR reanalysis data, it has been shown that the official methodology indicates the superiority of forecast skill over the seas and coastal areas. With an exception of points above the seas, the mean absolute error for the territory of Eastern Europe is 3,01 °C, and the forecast skill is 45,2 %. In case of inclusion the grid points over the seas — 2,78 °C and 48,6 % respectively.

Practical value/implications.  The obtained forecast skills of «non-methodological» forecasts are needed for estimation of the relative effectiveness of monthly forecasts based on a certain methodology (model). The ratio of the certain model forecast skill to the climatological forecast skill >1,0 will indicate the practical usefulness of the model, while
the ratio of <1,0 will indicate the need for an adjustment of the model or the refusal to use such a model.

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