University Scholar Series: Craig B. Clements

Groundbreaking Research on Wildfire Weather On November 28, 2012 Craig B. Clements spoke in the University Scholar Series hosted by Provost Ellen Junn at the Dr. Martin Luther King, Jr. Library. Craig Clements is an associate professor in the Department of Meteorology and Climate Science who received a $900,000 National Science Foundation CAREER grant for his work in tracking atmospheric conditions in and around wildfires. His work will better help predict wildfire behavior and conditions that could lead to increased wildfire danger.https://scholarworks.sjsu.edu/uss/1016/thumbnail.jp

The novel role of epidermal growth factor (EGF) in the regulation of ion channels in the calu-3 submucosal cell line

Cystic fibrosis transmembrane conductance regulator (CFTR) is a cell membrane bound chloride ion channel regulated by cyclic AMP-dependent phosphorylation and levels of intracellular ATP. Mutations in this channel, such as the common deletion of phenylalanine at residue 508 (CFTRΔF508), leads to a decrease in chloride transport seen in the disease condition cystic fibrosis (CF). The mutant CFTR is not processed in the normal way and consequently not delivered to the cell membrane. Currently, the effect of growth factors such as epidermal growth factor (EGF) on ion transport in the airway has not been previously researched and is consequently unknown. Therefore the aim of this thesis is to determine (i) if EGF has an effect on ion transport in the submucosal cell line Calu-3, (ii) what the mechanisms are behind this, and (iii) if the effect of EGF was due to induction of gelatinase activity or a transactivation process. Functional investigations looking at ion transport were carried out by using short circuit current. This technique was complemented by traditional molecular biology techniques such as RT-PCR, Western blotting, flow cytometry and gelatin zymography. The level of EGF, a potent inducer of gelatinases, is known to be elevated in the lungs during tissue repair in CF. Calu-3 cells preincubated with EGF on the basolateral membrane increased initial current at one hour via a EGFR-PI3K-PKC-δ-KCNN4/KCNQ1 signalling pathway. Similarly, preincubation with EGF also decreased forskolin induced short circuit current compared to untreated monolayers at 1 to 3 hours, with a recovery at 24 hours. The decreases were found to be dependent on the activation of KCNQ1 since chromanol 293B, a specific inhibitor for KCNQ1, restored the short circuit current back to untreated levels. Stimulation of the β2 adrenergic receptors with salbutamol were not reduced using metalloproteinase inhibitor, GM-6001 and EGFR inhibitor, AG1478. This suggested that stimulation of β2 adrenergic receptors does not lead to transactivation of EGFR via activation of sheddases and the release of EGF ligand. β3 adrenergic receptors are present in Calu-3, but produce negligible currents when stimulated. It was concluded that EGF induced potassium channel activation led to a change in chloride driving force. This activation of potassium channels has previously been linked to wound repair in the airway during disease. The implications of this study suggest that manipulation of the EGF signalling pathway and / or potassium channel activity in the lungs may be beneficial in disease conditions such as CF for increasing chloride transport

Extreme fire weather associated with nocturnal drying in elevated coastal Terrain of California

The second largest fire shelter deployment in U.S. history occurred in August 2003 during the Devil Fire, which was burning in a remote and rugged region of the San Francisco Bay Area, when relative humidity abruptly dropped in the middle of the night, causing rapid fire growth. Nocturnal drying events in the higher elevations along California\u27s central coast are a unique phenomenon that poses a great risk to wildland firefighters. Single-digit relative humidity with dewpoints below -25°C is not uncommon during summer nights in this region. To provide the fire management community with knowledge of these hazardous conditions, an event criterion was established to develop a climatology of nocturnal drying and to investigate the synoptic patterns associated with these events. A lower-tropospheric source region of dry air was found over the northeastern Pacific Ocean corresponding to an area of maximum low-level divergence and associated subsidence. This dry air forms above a marine inversion and advects inland overnight with the marine layer and immerses higher-elevation terrain with warm and dry air. An average of 15-20 nocturnal drying events per year occur in elevations greater than 700m in the San Francisco Bay Area, and their characteristics are highly variable, making them a challenge to forecast

Evolution of plume core structures and turbulence during a wildland fire experiment

Micrometeorological observations were made during a prescribed fire experiment conducted in a region of complex terrain with grass fuels and weak ambient winds of 3 m s-1. The experiment allowed for the analysis of plume and turbulence structures including individual plume core evolution during fire front passage. Observations were made using a suite of in situ and remote sensing instruments strategically placed at the base of a gully with a 24° slope angle. The fire did not spread upwards along the gully because the ambient wind was not in alignment with the slope, demonstrating that unexpected fire spread can occur under weak wind conditions. Our observational results show that plume overturning caused downward heat transport of-64 kW m-2 to occur and that this mixing of warmer plume air downward to the surface may result in increased preheating of fine fuels. Plume evolution was associated with the formation of two plume cores, caused by vigorous entrainment and mixing into the plume. Furthermore, the turbulence kinetic energy observed within the plume was dominated by horizontal velocity variances, likely caused by increased fire-induced circulations into the plume core. These observations highlight the nature of plume core separation and evolution and provide context for understanding the plume dynamics of larger and more intense wildfires

The 2018 Camp Fire: Meteorological analysis using in situ observations and numerical simulations

The November 2018 Camp Fire quickly became the deadliest and most destructive wildfire in California history. In this case study, we investigate the contribution of meteorological conditions and, in particular, a downslope windstorm that occurred during the 2018 Camp Fire. Dry seasonal conditions prior to ignition led to 100-h fuel moisture contents in the region to reach record low levels. Meteorological observations were primarily made from a number of remote automatic weather stations and a mobile scanning Doppler lidar deployed to the fire on 8 November 2018. Additionally, gridded operational forecast models and high-resolution meteorological simulations were synthesized in the analysis to provide context for the meteorological observations and structure of the downslope windstorm. Results show that this event was associated with mid-level anti-cyclonic Rossby wave breaking likely caused by cold air advection aloft. An inverted surface trough over central California created a pressure gradient which likely enhanced the downslope winds. Sustained surface winds between 3-6 m s1 were observed with gusts of over 25 m s-1 while winds above the surface were associated with an intermittent low-level jet. The meteorological conditions of the event were well forecasted, and the severity of the fire was not surprising given the fire danger potential for that day. However, use of surface networks alone do not provide adequate observations for understanding downslope windstorm events and their impact on fire spread. Fire management operations may benefit from the use of operational wind profilers to better understand the evolution of downslope windstorms and other fire weather phenomena that are poorly understood and observed

Mobile Ka-Band Polarimetric Doppler Radar Observations of Wildfire Smoke Plumes

Remote sensing techniques have been used to study and track wildfire smoke plume structure and evolution; however, knowledge gaps remain because of the limited availability of observational datasets aimed at understanding finescale fire-atmosphere interactions and plume microphysics. Meteorological radars have been used to investigate the evolution of plume rise in time and space, but highly resolved plume observations are limited. In this study, we present a new mobile millimeter-wave (Ka band) Doppler radar system acquired to sample the fine-scale kinematics and microphysical properties of active wildfire smoke plumes from both wildfires and large prescribed fires. Four field deployments were conducted in autumn of 2019 during two wildfires in California and one prescribed burn in Utah. Radar parameters investigated in this study include reflectivity, radial velocity, Doppler spectrum width, differential reflectivity ZDR, and copolarized correlation coefficient rHV. Observed radar reflectivity ranged between 215 and 20 dBZ in plume, and radial velocity ranged from 0 to 16ms21. Dual-polarimetric observations revealed that scattering sources within wildfire plumes are primarily nonspherical and oblate-shaped targets as indicated by ZDR values measuring above 0 and rHV values below 0.8 within the plume. Doppler spectrum width maxima were located near the updraft core region and were associated with radar reflectivity maxima

Meteorological profiling in the fire environment using UAS

With the increase in commercially available small unmanned aircraft systems (UAS), new observations in extreme environments are becoming more obtainable. One such application is the fire environment, wherein measuring both fire and atmospheric properties are challenging. The Fire and Smoke Model Evaluation Experiment offered the unique opportunity of a large controlled wildfire, which allowed measurements that cannot generally be taken during an active wildfire. Fire–atmosphere interactions have typically been measured from stationary instrumented towers and by remote sensing systems such as lidar. Advances in UAS and compact meteorological instrumentation have allowed for small moving weather stations that can move with the fire front while sampling. This study highlights the use of DJI Matrice 200, which was equipped with a TriSonica Mini Wind and Weather station sonic anemometer weather station in order to sample the fire environment in an experimental and controlled setting. The weather station was mounted on to a carbon fiber pole extending off the side of the platform. The system was tested against an RM-Young 81,000 sonic anemometer, mounted at 6 and 2 m above ground levelto assess any bias in the UAS platform. Preliminary data show that this system can be useful for taking vertical profiles of atmospheric variables, in addition to being used in place of meteorological tower measurements when suitable

Evaluation of WRF-Sfire Performance with Field Observations from the FireFlux experiment

This study uses in-situ measurements collected during the FireFlux field experiment to evaluate and improve the performance of coupled atmosphere-fire model WRF-Sfire. The simulation by WRF-Sfire of the experimental burn shows that WRF-Sfire is capable of providing realistic head fire rate-of-spread and the vertical temperature structure of the fire plume, and, up to 10 m above ground level, fire-induced surface flow and vertical velocities within the plume. The model captured the changes in wind speed and direction before, during, and after fire front passage, along with arrival times of wind speed, temperature, and updraft maximae, at the two instrumented flux towers used in FireFlux. The model overestimated vertical velocities and underestimated horizontal wind speeds measured at tower heights above the 10 m, and it is hypothesized that the limited model resolution over estimated the fire front depth, leading to too high a heat release and, subsequently, too strong an updraft. However, on the whole, WRF-Sfire fire plume behavior is consistent with the interpretation of FireFlux observations. The study suggests optimal experimental pre-planning, design, and execution of future field campaigns that are needed for further coupled atmosphere-fire model development and evaluation

Remote characterization of fire behavior during the FireFlux II experiment

The FireFlux II field experiment was conducted on January 30th, 2013 in south-east Texas, USA, under high fire danger conditions. The experiment was designed to study the behavior of a head fire progressing through a flat, tall grass prairie, and it was informed by the use of a coupled fire-atmosphere model. Vegetation properties and fuel moisture were measured shortly before the experiment. Near-surface atmospheric conditions were monitored during the experiment using an elaborate meteorological instrumentation array. Fire behavior was observed through a combination of remote and in-situ sensors. Clements et al. (2019) presented the analysis of the experiment micrometeorology and in-situ fire behavior observations acquired using a thermocouple array. In this paper, we extend the study of fire behavior during the FireFlux II experiment with the analysis of remote sensing observations. Two thermal infrared and two visible cameras were deployed during the experiment. One thermal and one visible camera were mounted on a helicopter, whereas the other two cameras were installed on a 40-m-height tower next to the burn unit. The tower infrared camera covered a reduced area of interest coincident with the thermocouple array and it allowed monitoring the fire spread as well as measuring the spatially-resolved evolution of brightness temperature. Imagery collected from the helicopter allowed extending fire behavior measurements to the complete burn unit. While airborne IR footage was saturated and did not allow estimation of emitted radiant heat, its analysis allowed tracking fire progression through the plot and therefore estimating rate of spread and fire time of arrival. The existence of in-situ temperature observations provides an outstanding opportunity to validate remote sensing methodologies. In addition, the combination of remote observations with in-situ fire and fuel measurements allows a comprehensive characterization of fire behavior, including spatially-resolved fire rate of spread and fire time of arrival, fire radiative power, Byram’s fire line intensity, and air temperature during fire front passage. This paper presents preliminary results from this analysis. Such results demonstrate the usefulness of the selected datasets and the potential of the proposed methodology, encouraging further work. Possible applications of the resulting dataset include (i) the validation of existing fire behavior models that are able to predict any of the measured variables, (ii) the development of data-driven fire behavior models, and (iii) the investigation of the relative contribution of radiative and convective heat transfer mechanisms to fire spreadPostprint (published version