Haines Index Research Articles

Haines Index를 이용한 동아시아 지역 산불 확산 위험도 변화와 지표-대기 상호관계와의 연관성 연구

Many studies have related the recent variations of wildfire regime such as the increasing number of occurrances, their patterns and timing changes, and the severity of their extreme cases with global warming. However, there are only a few numbers of wildfire studies to assess how the future wildfire regime will change in the interactions between land and atmosphere with climate change especially over East Asia. This study was performed to estimate the future changing aspect of wildfire danger with global warming, using Haines Index (HI). Calculated from atmospheric instability and dryness, HI is the potential of an existing fire to become a dangerous wildfire. Using the Weather Research and Forecasting (WRF) model, two separated 5-year simulations of current (1995~1999) and far future (2095~2099) were performed and analyzed. Community Climate System Model 3 (CCSM3) model outputs were utilized for the model inputs for the past and future over East Asia; future prediction was driven under the IPCC A1B scenario. The results indicate changes of the wildfire danger regime, showing overall decreasing the wildfire danger in the future but intensified regional deviations between north and south. The overall changes of the wildfire regime seems to stem from atmospheric dryness which is sensitive to soil moisture variation. In some locations, the future wildfire danger overall decreases in summer but increases in winter or fall when the actual fire occurrence are generally peaked especially in South China.

Climatic Variability of Near-Surface Turbulent Kinetic Energy over the United States: Implications for Fire-Weather Predictions

AbstractRecent research suggests that high levels of ambient near-surface atmospheric turbulence are often associated with rapid and sometimes erratic wildland fire spread that may eventually lead to large burn areas. Previous research has also examined the feasibility of using near-surface atmospheric turbulent kinetic energy (TKEs) alone or in combination with the Haines index (HI) as an additional indicator of anomalous atmospheric conditions conducive to erratic or extreme fire behavior. However, the application of TKEs-based indices for operational fire-weather predictions in the United States on a regional or national basis first requires a climatic assessment of the spatial and temporal patterns of the indices that can then be used for testing their operational effectiveness. This study provides an initial examination of some of the spatial and temporal variability patterns across the United States of TKEs and the product of HI and TKEs (HITKEs) using data from the North American Regional Reanalysis dataset covering the 1979–2008 period. The analyses suggest that there are regional differences in the behavior of these indices and that regionally dependent threshold values for TKEs and HITKEs may be needed for their potential use as operational indicators of anomalous atmospheric turbulence conditions conducive to erratic fire behavior. The analyses also indicate that broad areas within the northeastern, southeastern, and southwestern regions of the United States have experienced statistically significant positive trends in TKEs and HITKEs values over the 1979–2008 period, with the most substantial increases in values occurring over the 1994–2008 period.

ÍNDICES DE RISCO DE FOGO DE HAINES E SETZER EM DIFERENTES CONDIÇÕES CLIMÁTICAS (index of risk of HAINES and SETZER under differents climatics condition)

Vegetation Þ res are the second source of greenhouse gas emissions into the atmosphere. An important step to reduce the climate impact of these emissions is the investigation of the atmospheric susceptibility of a region for Þ re development (Þ re risk). This study aims to investigate the environmental susceptibility to Þ re development, based on Þ re risk model: the Haines Index (IH) and the Stezer (IS) index. The study was carried out with data from the ECHAM5/MPI-OM climate model and the NCEP reanalysis data, to calculate both indices during two periods: present day (1980-2000) and climate projections for the end of the 21st century (2080-2100). Based upon the results, we concluded that the Haines index could reproduced property the areas with the highest Þ re incidence under present conditions. Moreover, it has been found that below under greenhouse warming conditions there is an enlargement in the Þ re risk area, in particular for the Amazon region to the IS.

Suscetibilidade do ambiente a ocorrências de queimadas sob condições climáticas atuais e de futuro aquecimento global

As queimadas, a nível global, são a segunda maior fonte de emissões de gases de efeito estufa. Um passo importante para a redução dos impactos das queimadas é por meio de investigação da suscetibilidade, que um determinado ambiente possui para a queima ou mesmo para o alastramento do fogo (risco de fogo). Diante da necessidade de se conhecer possíveis implicações das mudanças na circulação atmosférica em um futuro próximo, pretende-se neste trabalho investigar a suscetibilidade do ambiente à ocorrência de queimadas, baseado no índice de risco de queimadas, a saber: o Índice de Haines (IH). Para tanto, dados de modelagem numérica do modelo ECHAM5/MPI-OM, e dados das reanálises do NCEP são empregados para os cálculos do IH em dois períodos: atual (1980-2000) e projeções climáticas para o final do século (2080-2100). Com base nos resultados, concluiu-se que o modelo de risco de fogo reproduz bem as áreas com maior incidência de queimadas sob condições atuais, e que sob condições de aquecimento global detectou-se um aumento na área de risco em especial para a região Amazônica.

A North American regional reanalysis climatology of the Haines Index

A warm-season (May through October) Haines Index climatology is derived using 32-km regional reanalysis temperature and humidity data from 1980 to 2007. We compute lapse rates, dewpoint depressions, Haines Index factors A and B, and values for each of the low-, mid- and high-elevation variants of the Haines Index. Statistical techniques are used to investigate the spatial and temporal variability of the index across North America. The new climatology is compared with a previous climatology derived from 2.5° (~280 km) global reanalysis data. Maps from the two climatologies are found to be very similar for most of North America. The largest differences appear along the eastern coastline and in regions of large elevation gradients, where the orography in the 32-km climatology is better resolved than that of the 2.5° climatology. In coastal areas of eastern North America and where there is steeply sloping terrain, the new climatology can augment the information from the 2.5° climatology to help analyse the performance and interpret the results of the Haines Index in these regions. A linear trend analysis of the total number of high-Haines Index days occurring in each warm season reveals no significant linear trends over the 28-year data period.

Atmospheric susceptibility to wildfire occurrence during the Last Glacial Maximum and mid-Holocene

Based on coupled climate model simulations the impact of anomalous climate forcing on the environmental vulnerability to wildfire occurrence is analyzed. The investigation applies the Haines Index (HI), which indicates the potential for wildfire growth by measuring the stability and dryness of the air. Three simulations have been analyzed: for Last Glacial Maximum (LGM), the mid-Holocene (MH) and present day (MOD) conditions. The results indicate that for present day conditions, the HI is a useful tool to identify areas with high susceptibility for fire occurrence, such as the west coast of the United States and the central part of South America. Analyses for the glacial epoch demonstrated that in respect to MOD conditions, the HI is intensified in Africa and south Asia. It is reduced, however, in Australia, the west coast of North America, Europe and in northern Asia. During the mid-Holocene, the atmospheric conditions were likely more favorable for fire occurrence over North America, sub-Saharan Africa and a large part of Eurasia and South America. In the contrary, Australia, northern Africa and the northern part of South America seem to have been less susceptible to intense fire as compared to current conditions. These findings very closely match paleofire inferences based upon charcoal analyses.

Turbulent kinetic energy during wildfires in the north central and north-eastern US

The suite of operational fire-weather indices available for assessing the atmospheric potential for extreme fire behaviour typically does not include indices that account for atmospheric boundary-layer turbulence or wind gustiness that can increase the erratic behaviour of fires. As a first step in testing the feasibility of using a quantitative measure of turbulence as a stand-alone fire-weather index or as a component of a fire-weather index, simulations of the spatial and temporal patterns of turbulent kinetic energy during major recent wildfire events in the western Great Lakes and north-eastern US regions were performed. Simulation results indicate that the larger wildfires in these regions of the US were associated with episodes of significant boundary-layer ambient turbulence. Case studies of the largest recent wildfires to occur in these regions indicate that the periods of most rapid fire growth were generally coincident with occurrences of the product of the Haines Index and near-surface turbulent kinetic energy exceeding a value of 15 m2 s–2, a threshold indicative of a highly turbulent boundary layer beneath unstable and dry atmospheric layers, which is a condition that can be conducive to erratic fire behaviour.

Interannual variations in fire weather, fire extent, and synoptic-scale circulation patterns in northern California and Oregon

The Mediterranean climate region on the west coast of the United States is characterized by wet winters and dry summers, and by high fire activity. The importance of synoptic-scale circulation patterns (ENSO, PDO, PNA) on fire-climate interactions is evident in contemporary fire data sets and in pre-Euroamerican tree-ring-based fire records. We investigated how interannual variability in two fire weather indices, the Haines index (HI) and the Energy Release Component (ERC), in the Mediterranean region of southern Oregon and northern California is related to atmospheric circulation and fire extent. Years with high and low fire weather index values corresponded to years with a high and low annual area burned, respectively. HI combines atmospheric moisture with atmospheric instability and variation in HI was more strongly associated with interannual variation in wildfire extent than ERC, which is based on moisture alone. The association between fire extent and HI was also higher for fires in southern Oregon than in northern California. In terms of synoptic-scale circulation patterns, years of high fire risk (i.e., increased potential for erratic fire behavior, represented by HI and ERC) were associated with positive winter PNA and PDO conditions, characterized by enhanced regional mid-tropospheric ridging and low atmospheric moisture. The time lag we found between fire risk potential and prior winter circulation patterns could contribute to the development of long-lead fire-climate forecasting.

Computing the Low-Elevation Variant of the Haines Index for Fire Weather Forecasts

Abstract The Haines index is used in wildfire forecasting and monitoring to evaluate the potential contributions of atmospheric stability and humidity to the behavior of plume-dominated wildfires. The index has three variants (“low,” “mid,” and “high”) that accommodate differences in surface elevation. As originally formulated, the low variant is calculated from temperature observations at the 950- and 850-hPa levels and humidity observations at 850 hPa. In the early 1990s the National Weather Service implemented a new mandatory level for radiosonde observations at 925 hPa. Following this change, measurements at 950 hPa became less frequent. An informal survey of several forecast offices found no formalized adjustment to the calculation of the low Haines index to take into account the nonavailability of 950-hPa measurements. Some sources continue to use 950-hPa temperature, usually interpolated from 925-hPa and surface temperatures, to calculate the low Haines index. Others directly substitute the 925-hPa temperature for the originally specified 950-hPa value. This study employs soundings from the central United States when both 950- and 925-hPa levels were available to investigate the impact of different calculation approaches on the resulting values of the low variant of the Haines index. Results show that direct substitution of 925-hPa temperature for the 950-hPa temperature can dramatically underestimate the potential wildfire severity compared with the original formulation of the Haines index. On the other hand, a low-elevation variant of the Haines index calculated from the interpolated 950-hPa temperature is usually in close agreement with the original formulation of the index.

Climatological and statistical characteristics of the Haines Index for North America

The Haines Index is an operational tool for evaluating the potential contribution of dry, unstable air to the development of large or erratic plume-dominated wildfires. The index has three variants related to surface elevation, and is calculated from temperature and humidity measurements at atmospheric pressure levels. To effectively use the Haines Index, fire forecasters and managers must be aware of the climatological and statistical characteristics of the index for their location. However, a detailed, long-term, and spatially extensive analysis of the index does not currently exist. To meet this need, a 40-year (1961–2000) climatology of the Haines Index was developed for North America. The climatology is based on gridded (2.5° latitude × 2.5° longitude) temperature and humidity fields from the NCEP/NCAR reanalysis. The climatology illustrates the large spatial variability in the Haines Index both within and between regions using the different index variants. These spatial variations point to the limitations of the index and must be taken into account when using the Haines Index operationally.

Validation of the Haines Index predicted from real-time high-resolution MM5 forecasts using rawinsonde observations over the eastern half of the USA

The accuracy of the predicted Haines Index using the MM5 model is evaluated using rawinsonde observations. The evaluation compared predicted and observed Haines Indices during a 5-month period from 1 June to 31 October 2003 at 29 upper-air sounding sites within the modeling domain over much of the eastern half of the USA. Despite a consistent cold bias of 1–3°C in the lower to mid troposphere and a dry bias at the 850-mb and 700-mb levels in the MM5 results, little bias is found in the predicted Haines Index. This is because the temperature bias is largely cancelled in the calculation of the vertical temperature gradients used to derive the Haines Index and the dry bias is compensated by the slightly weaker instability in the model predictions. The predicted Haines Index captured the observed spatial and temporal variations of the observed index values resulting from changes in synoptic conditions. Of the 4184 total available soundings for the comparison, 45% had an exact match between the predicted and observed Haines Index categories and another 43% had a good match with the predicted and observed index differing by only one category. The rest of the 12% were cases where the predicted index fell under a category that was substantially different from the observed category, significantly raising or lowering the risk level for potentially dangerous fire behavior. Despite the general success, serious limitations exist when using the Haines Index derived from MM5 results for predicting high-risk conditions. This is because the prediction failed more than 50% of the time to capture the observed extreme cases when the observed index reached its highest possible value of 6. Although such extreme cases are rare, they represent conditions that are most conducive to dangerous and erratic fire behaviors and failure to predict these conditions may lead to serious consequences.

Investigating the Haines Index using parcel model theory

By using parcel model theory to construct a two-dimensional parameter space formed by low-level atmospheric stability and moisture, a simple framework on which to examine certain fire parcel properties associated with vertical column development is established. This framework is used to investigate if the Haines Index has some skill at predicting wildfire severity, where wildfire severity is assumed to be directly connected to vertical column development and the result of significant fire parcel ascent. By modeling the ascent of a moist, entraining fire parcel in four different background states—a 3 km deep boundary layer, a 2 km deep boundary layer, a 3 km deep boundary layer topped by an inversion layer, and a 2 km deep boundary layer topped by an inversion layer—the study shows that parcel properties that describe ascent and vertical column development are most significant when the boundary layer temperature lapse rate is near adiabatic and lower-level atmospheric humidity is relatively high. A shallower instead of a deeper boundary layer lowers parcel ascent, and an upper-level inversion lowers parcel ascent even further. This study shows that entraining fire parcel properties and magnitudes associated with significant ascent do not necessarily correspond to a Haines Index for a potential for high fire severity. The results suggest that the Haines Index may need to be refined or reformed depending on the stability and humidity in the boundary layer and vertical structure of the atmosphere. This study is a start to understanding the influence of the background state on fire parcel convection and an attempt to explain how the Haines Index works from an elementary but physical point of view.

An examination of the sensitivity of numerically simulated wildfires to low-level atmospheric stability and moisture, and the consequences for the Haines Index

The Haines Index, an operational fire–weather index introduced in 1988 and based on the observed stability and moisture content of the near-surface atmosphere, has been a useful indicator of the potential for high-risk fires in low wind conditions and flat terrain. The Haines Index is of limited use, however, as a predictor of actual fire behavior. To develop a fire–weather index to predict severe or erratic wildfire behavior, an understanding of how the ambient lower-level atmospheric stability and moisture affects the growth of a wildfire is needed. This study is a first step in this process. This study investigates, through four comparative numerical simulations with a coupled wildfire–atmosphere model, the sensitivity of wildland fires to atmospheric stability and moisture, and in the process explores the correspondence between atmospheric stability and moisture, wildfire behavior, and the Haines Index. In the first three fire simulations, the model atmosphere was initially set to identical moisture but different instability conditions that correspond to Haines Indexes for low, moderate, and high potential for severe fire development. In the fourth fire simulation, the initial atmospheric and moisture conditions were for a high-risk fire Haines Index rating, but different from the initial conditions of dryness and stability of the previous experiments. The study indicates that high-risk fire development is sensitive to near-surface atmospheric stability and moisture, and that there is a range of atmospheric stability and moisture conditions that is important to the development of severe or erratic fire behavior, and that this range is within the atmospheric stability and moisture conditions represented by a Haines Index for high potential for severe fire. The analyses also suggest that there is a substantial latitude of fire behavior for fires rated as this Index, indicating that this Index should be further divided, or refined.