New Approach for Surface n Factors

bstract: Air and surface freezing and thawing indexes and prediction of round temperatures from air temperatures were investigated. A new method for pplying n factors on a daily basis to capture localized temperature extremes is resented and compared to conventional seasonal n-factor analysis. Measured air emperatures from five locations and measured air and surface temperatures from ne location were used. Freezing and thawing indexes were determined using aily and monthly average temperatures, different time frames, and seasonal and aily applications of n factors. Air and surface freezing indexes �Iaf and Isf� varied ore than air and surface thawing indexes �Iat and Ist�. Significant variations were bserved in air and surface indexes due to the length of the time period used �1, 0, and 30 years� and frequency of temperature data used �daily and monthly�. he surface indexes from seasonal n factors �using daily average temperatures� nd daily n factors were similar �within 4%� and higher than the indexes from easonal n factors �using monthly average temperatures�. The average surface emperatures were within 2°C, whereas the maximum and minimum surface emperatures were significantly different �up to 26°C� between the seasonal and aily n factors. Maximum variations between consecutive daily maximum and inimum temperatures were significantly higher using daily n factors �up to 2°C� than seasonal n factors �less than 1°C�. Surface indexes from seasonal using daily average temperatures� and daily n factors can be used interchange­ bly. Daily n factors are recommended to obtain representative surface and near­