Numerical Climatic Estimations of Precipitation and Surface Air Temperature for the Black Sea Region

Abstract

Numerical schemes for precipitation calculation used in RegCM regional model are adapted to the Black Sea region. The discrepancies between the results of the RegCM modeling and the ERA-Interim reanalysis data are considered in detail on the example of the monthly average fields of precipitation and surface air temperature. It is revealed that the discrepancies between the results of modeling according to RegCM and ERA-Interim reanalysis data are quite small due to the fact that the amount of convective precipitation is underestimated in RegCM model and the one of non-convective precipitation is overestimated. Therefore, the changes were introduced in the model in such a way as to reduce the amount of precipitation falling over the land only. It is shown that the discrepancies between the monthly average fields of surface air temperature in RegCM and ERA-Interim are due to the differences in a relief height, errors in RegCM (which overestimates the amount of precipitation over the flat land) and errors of the model input data.
The numerical experiments aimed to reduce overestimation of the precipitation amount over the flat land to the north of the Black Sea are performed. It is found that the results of precipitation modeling according to RegCM are the most sensitive to the variation of that threshold value which determines specific cloud water content at which the clouds begin to form and to variation of minimum and maximum possible threshold values of “precipitation efficiency”. Characteristic rate of raindrop evaporation and a method for calculation of updraft mass in the cloud have little effect on the results of non-convective precipitation modeling.
Using the data on annual average precipitation amount and evaporation from the Black Sea surface an estimation of water discharge through the Bosporus, Kerch Strait and river runoffs (which makes up ~370 mm in both models) was refined.

Keywords

the Black Sea region, climate regional modeling, parameterization of precipitation, reanalysis.

DOI: 10.22449/1573-160X-2016-3-57-69

Download the article