Analysis of daily mean synoptic situation in a late frosts period in Alto Valle of Río Negro, Argentina

Late frosts mainly affect fruit production in Alto Valle of Río Negro region, Argentina, during September and October every year.

Data from weather elements were obtained in a field experiment during several periods of time in September and October 1993. Automated weather stations were located in several points along the valley to describe temperature and wind patterns in the valley. Surface data was obtained in farm area with extensive vegetation and in some places over Patagonian plateau

Soundings of temperature and wind speed and direction were performed in central part of valley. These measurements were done to characterize boundary layer nocturnal inversion in the valley.

This paper presents an analysis of surface data in some points along the valley and daily mean fields of total cloud coverage, 2 m temperature, and 10 m wind components relationships. The variation of these elements with time was studied related to boundary layer behavior.

The daily mean synoptic data was studied to analyze boundary layer conditions and situations with adequate conditions of frost occurrence. The results shows that temperature and wind patterns over the plain were well correlated with regional situation, but flow behavior within the valley was highly correlated with topography and local flows development. The different fields were compared with 1982-1994 mean fields.