engleski

Mapping wintertime 2-meter level temperature for days with surface inversions

Procedure for mapping monthly average 2-meter level temperatures consists of two steps: the first is the description of a deterministic (trend) component of a temperature field and the second is statistical interpolation of the residuals. Trend component includes terrain influence information mainly through the temperature lapse rate (negative vertical temperature gradient) and it describes large-scale temperature variation. Residuals are differences between measured temperatures and the deterministic component and they are interpolated by the Gandin optimal interpolation method to a regular grid. However, during the winter season, vertical temperature lapse rate is weak compared to the mean temperature lapse rate of 0.65 °C/100m. According to the measurements from 51 weather stations situated on altitudes from 83 to 988 meters in the continental part of Croatia, for the period 1971-1975, the lapse rate is 0.2 °C in January, 0.5 °C in February and only 0.1 °C in December with the coefficients of determination very small in January (0.42) and December (0.15). For the same period, average vertical temperature profile from the radiosonde measurements in 00 and 12 UTC reveals 200 meters deep surface inversion layer in January and February, and 400 meters in December, i.e. the vertical lapse rate is negative. Due to fact that 89% of the continental part of Croatia is on the altitudes lower then 400 m, thus being influenced with those wintertime inversions, it is concluded that positive lapse rates calculated from observations on stations are not very appropriate for the objective analysis of mean monthly temperatures during winter season. For that reason, an attempt was made to select only the days with pronounced inversions according to radiosonde measurements and to investigate the spatial temperature distribution in these wintertime specific situations. The classification of the inversion situations has been made according to the inversion strength defined as a difference between maximum temperature in a layer 1500 meters deep and surface temperature. The GIS tools were used for some calculations as well as for the visualization of results and producing the final maps.

temperature map; mean monthly temperature; winter; temperature lapse rate; surface inversion; optimal interpolation; GIS

nije evidentirano