The Long-Lived Plume of the Pacific Northwest PyroCb Event: Diabatic Lofting and Radiative Effects of Aerosol and Water Vapor
Abstract
A group of nearby pyroconvective events occurred on 12 August 2017 in the Pacific Northwest that injected an unprecedented smoke plume directly into the lower stratosphere. The size and duration of this plume allowed for continuous observations lasting longer 100 days using A-Train satellite instruments. During this time, many exceptional aspects of this plume were observed, including 1) its diabatic lofting over the course of several weeks, reaching an altitude approximately 10 km greater than the initial injection point (Δθ > 200 K), 2) its separation into multiple layers that circumnavigated the northern hemisphere at different latitudes, altitudes and travel directions, and 3) the large localized enhancements of biomass burning gases such as H2O, CO and HCN. The Microwave Limb Sounder (MLS) on-board NASA's Aura satellite observed these enhancements, and—together with aerosol observations by the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIOP) instrument—helped track the movement, allowing for estimates of trace gas anomalies and aerosol extinction. We have used these observations to characterize the lifetime of three separated parts of the plume, and to estimate radiative fluxes and heating rates. Diabatic lofting estimates were performed with a full spectrum 1-dimensional band model using CALIOP-derived aerosol extinction. Plume-centered heating rate anomalies ranged between +1.0 to +2.0 K day-1 over its lifetime, consistent with its observed rise. Additionally, we isolated the H2O mixing ratio anomalies to estimate the radiative forcing of this injection event using a longwave line-by-line model. Comparisons with a climatology of MLS H2O showed this plume's surface downward flux forcing was small with absolute values typically less than 0.1 W m-2, and TOA upward flux forcing was slightly larger with values ranging from -1.0 to +1.0 W m-2, depending on latitude. Localized stratospheric heating rates from this H2O were -0.4 K day-1 within the plume, and +0.1 K day-1 between the plume and tropopause.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.A23E..05K
- Keywords:
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- 0305 Aerosols and particles;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 0340 Middle atmosphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 3311 Clouds and aerosols;
- ATMOSPHERIC PROCESSES