Probability and Severity of Spring and Fall Frosts based on 116 Grid Points

This study investigates the probability data associated with frost temperature occurrences across 116 grid points with a horizontal resolution of 10 x 9 x 10 km. The primary objective is to summarize the probability of three frost severity classes (mild, moderate, and severe) for all grid points, focusing on later dates in spring and earlier dates in fall, and to determine the probable length of the frost-free period (FFP).

Table 5 presents the dates of the last spring frost (LSF) and the first fall frost (FFF) for various probabilities and the three frost severity classes, derived using the Pearson Type III distribution. The probability of LSF occurrence decreases as intensity increases.

Key findings include:

• Last Spring Frost (LSF): At a 50% probability level, the end dates for mild, moderate, and severe spring frosts are on or earlier than April 22nd (day 112), April 13th (day 103), and April 8th (day 98), respectively. A 96% probability level indicates that in the Elbe River lowland, the last mild spring frost occurs on or before May 20th, moderate frost on or before May 13th, and severe frost on or before May 6th. While a 10% chance exists for mild spring frost after May 12th, there is a 90% probability of frost occurrence on or before this date.* First Fall Frost (FFF): Table 5 reveals a low probability of FFF occurrence in September. The first mild, moderate, and severe fall frosts are expected on or after September 22nd, September 29th, and October 4th with a 96% probability, respectively. This translates to only a 4% chance of the first frost occurring before these dates. The frequency of mild fall frosts increases in the latter half of October, with a 67% probability of occurrence on or after October 13th for mild frosts, October 21st for moderate frosts, and October 25th for severe frosts.

This analysis highlights the potential risk of frost damage to agricultural production, particularly emphasizing the vulnerability of crops planted after May 5th to late spring frosts. The data underscores the importance of considering these probabilities in agricultural planning and implementing appropriate frost mitigation strategies.