As I shared in a previous post, Vapor Pressure Deficit (VPD) is an index that translates into plant stress. The darker the color in these images, the more stressed the dry environment is putting on vegetation. The more stressed, the more potential to burn. While these levels vary from day to day, overall VPD levels have been on the rise in recent years.
Utilizing VPD to better characterize the fire environment is new to many of us. It describes fuel conditions in ways similar to fuel moisture and ERCs. Because it is an absolute value, it will better reflect the impacts from climate change. I am updating this again fairly regularly during August and September 2023 to help build reference points and improve an understanding of trends relative to this metric and the fire behavior we see.
Vapor Pressure Deficit values from 5pm PDT on 9/7/2020, Labor Day of that year, compared to the same time for 8/26/2023. The darker the color, the higher the VPD value, which means more stressed vegetation. 8.24.2023, 5pm PDT 8/25/2023, 5pm PDT 8/26/2023, 5pm PDT Vapor Pressure Deficit (VPD) progression for the last 3 days, from just before a series of thunderstorms ignited fires across the area in the very early hours of 8/25. Fire behavior and growth was more challenging on 8/26 than on 8/25 in most areas. Looking at VPD and fuel availability is one theme for ongoing research.9/6/2020, 5pm PDT 9/7/2020, 5pm PDT 9/26/2020, 5pm PDT Vapor Pressure Deficit (VPD) progression in September 2020, a period of historic fire activity along the Pacific coast. Here you see progression from the Labor Day 2020 period to several weeks later with cooling, occasional cloud cover and increased humidities across the region.
*Map times are UTC, 7 hrs ahead of Pacific Time in the US. These maps are showing 5pm on the date prior to the image heading.
