A climatology of freezing

precipitation over the Ukraine and

MoldovaKhomenko Inna,Khomenko Inna,Odessa State Environmental University, UkraineOdessa State Environmental University, Ukraine

12th EMS12th EMS Annual Meeting & 9th European Conference on Applied ClimatologyAnnual Meeting & 9th European Conference on Applied Climatology

10 – 14 September 201210 – 14 September 2012

Łódź, PolandŁódź, Poland

Location of the cites in the Ukraine and Moldova,for which freezing precipitation conditions are studied

Periods and number of surface observationsat the respective airports

Location of the cites in the Ukraine,for which radiosounding data are available

Months in which FP occurs at the respective airports

Maximum and minimummonthly mean occurrence frequency

0,21 Mar

1,03 Dec

0,23 Nov

1,60 Dec

0,05 Nov

1,45 Dec

0,39 Mar

1,83 Jan

0,01 Apr

1,00 Dec0,50 Mar

2,25 Dec

0,09 Mar

0,87 Dec

0,01 Apr

0,72 Jan

0,11 Mar

0,86 Feb

0,24 Mar

1,15 Jan

0,05 Apr

1,29 Jan

Spatial distribution of freezing drizzle cases (%)

Both types of precipitation – freezing rain and freezing drizzle – are geographically distributed:for the central part a predominant type is the freezing rain (from 49 to 74 for Moldova, Kishinev).This result may be explained by influence of cyclonic activity in winter.For the other stations a predominant type is freezing drizzle: from 58 (Lviv) to 90 % (Dnepropetrovsk).The predominant type of freezing drizzle was induced by air-mass mechanism of FP formation.

Frequency (%) of surface temperature associated with FP

Spatial distributions (%) of wind direction associated with FP

Classical mechanism ofClassical mechanism ofthe freezing precipitation the freezing precipitation

formationformation

Classification of the FP Classification of the FP casescases

Summary:

Freezing precipitation in the Ukraine represents a rare event, whose monthly maximum averaged occurrence frequency does not exceed a few percent.

The low clouds, which produce FP, are mainly cold. The classical stratification of “warm nose” type, with warm layer within the cloud, occurs, on average, in about 14% of FP cases, while “all cold” stratification – in about 54% of the cases. This result is important from a practical point of view. The existing schemes for FP forecasting are based on revealing the warm layers in or below the lower clouds. It is evident now that this notion cannot be efficient in the situations typical for the Ukraine. Other approaches, in particular, probabilistic ones should be found. Investigations of FP conditions, using all of the available data, can provide useful indications for detection of areas with increased probability of FP.