A Climatology of the Frequency and Duration of High Relative Humidity Events for the Lower Peninsula of Michigan

Authors: Kara Komoto*, Michigan State University, Logan Soldo, Michigan State University, Julie Winkler, Michigan State University, Martin Chilvers, Michigan State University, Kyla Dahlin, Michigan State University, Ying Tang, Michigan State University
Topics: Climatology and Meteorology
Keywords: climatology, relative humidity, atmospheric moisture, Michigan, crop, disease
Session Type: Poster
Day: 4/4/2019
Start / End Time: 8:00 AM / 9:40 AM
Room: Lincoln 2, Marriott, Exhibition Level
Presentation File: Download


Prolonged periods of high relative humidity have a broad range of impacts. This includes effects on human health, animal welfare and production, and susceptibility of crops to disease. Although relative humidity levels are particularly impactful for the Lower Peninsula of Michigan, which is both surrounded by lakes and heavily reliant on agriculture, a climatology of the frequency and duration of high relative humidity events in this area has not been conducted. Hourly observations from Automated Surface Observing System and Automated Weather Observing System stations for 2003-2017 were analyzed to examine, by biweekly periods, the probability of relative humidity ≥85% for durations of more than 9, 12, 15, 18, 24, and 36 hours. In addition, temporal trends for 1973-2017 were examined for a subset of stations. During the growing season, the probability is large (>75%) across the state of experiencing high relative humidity persisting for at least 6 hours, a threshold associated with the increased risk of some crop diseases. In general, the probability of longer duration high relative humidity events is smallest in the southeastern, and largest in the north central and northeastern portions of the Lower Peninsula, although within-season variations are substantial. For example, in the southeast the probability of relative humidity ≥85% persisting for at least 15 hours decreases from 60-80% in early June to less than 40% by mid-July. This climatology provides a baseline for assessing potential future changes in the frequency and duration of high humidity events and their impacts.

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