Katarina Borne

A METHOD FOR FINDING SEA BREEZE DAYS UNDER STABLE SYNOPTIC CONDITIONS AND ITS APPLICATION TO THE SWEDISH WEST COAST

A method for selecting sea breeze days in an archipelago was developed with special application to the West Coast of Sweden. The primary criterion for identifying a sea breeze was the occurrence of a distinct change in surface wind direction within a 24 h period. The data used in the study were gathered using hourly meteorological records from field stations situated on the West Coast. Six different filters were included in the method; each of them developed from empirical knowledge of the physical processes responsible for the occurrence of a sea breeze system. Using this method it is possible to create a data set of sea breeze days, which does not use distance to the shoreline as a necessary condition for classification.

Evaluation and Comparison of Noah and Pleim–Xiu Land Surface Models in MM5 Using GÖTE2001 Data: Spatial and Temporal Variations in Near-Surface Air Temperature

In this study, the performance of two advanced land surface models (LSMs; Noah LSM and Pleim–Xiu LSM) coupled with the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5), version 3.7.2, in simulating the near-surface air temperature in the greater Goteborg area in Sweden is evaluated and compared using the GOTE2001 field campaign data. Further, the effects of different planetary boundary layer schemes [Eta and Medium-Range Forecast (MRF) PBLs] for Noah LSM and soil moisture initialization approaches for Pleim–Xiu LSM are investigated. The investigation focuses on the evaluation and comparison of diurnal cycle intensity and maximum and minimum temperatures, as well as the urban heat island during the daytime and nighttime under the clear-sky and cloudy/rainy weather conditions for different experimental schemes. The results indicate that 1) there is an evident difference between Noah LSM and Pleim–Xiu LSM in simulating the near-surface air temperature, especially in the modeled urban heat island; 2) there is no evident difference in the model performance between the Eta PBL and MRF PBL coupled with the Noah LSM; and 3) soil moisture initialization is of crucial importance for model performance in the Pleim–Xiu LSM. In addition, owing to the recent release of MM5, version 3.7.3, some experiments done with version 3.7.2 were repeated to reveal the effects of the modifications in the Noah LSM and Pleim–Xiu LSM. The modification to longwave radiation parameterizations in Noah LSM significantly improves model performance while the adjustment of emissivity, one of the vegetation properties, affects Pleim–Xiu LSM performance to a larger extent. The study suggests that improvements both in Noah LSM physics and in Pleim–Xiu LSM initialization of soil moisture and parameterization of vegetation properties are important.