Dendrochronological techniques were used to reconstruct a 433-yr fire his- tory, and to characterize the historical fire regime (frequency, size, season, severity) of the Teanaway River drainage in the eastern Cascade Mountains of Washington, USA. General Land Office section corner data were used to reconstruct aspects of the late-19th-century structure and composition of the forests in the study area. Systematic fire-scar surveys (;30 000 ha; 92 sites; 257 fire-scarred cross-sections; 1569 individual fire scars) revealed that fire frequency was quite variable spatially; Weibull median probability intervals ranged from seven to 43 years. Fire extent also varied widely; most fires were relatively small (,1000 ha), although several large fires (.4000 ha) were detected. Mean and median fire sizes were 1795 ha and 988 ha, respectively. Large fires occurred every 27 years, on average (every 11 years, on average, between 1708 and 1889), and coincided with periods of annual and seasonal drought (Palmer Drought Severity Index and winter Southern Oscillation Index). Intervals from 1 to 37 years occurred between fires of .4000 ha. Over 80% of fires occurred late in the growing season, or after the onset of cambial dormancy. Sampling locations in dry forest types (dominated by ponderosa pine) yielded fire-scarred cross- sections with numerous fire scars leading us to infer that most historical fires were of low intensity, leaving the overstory structure intact. This inference is corroborated by the com- position and structure of the historical forest, which was characterized by a preponderance of very large (.100-cm diameter) ponderosa pines. Mesic forest types (dominated by grand fir and Douglas-fir) likely exhibited a wider range of fire severities. Moderate and occasional high-severity understory fires or crown fires did occur within the study area, as indicated by the scarcity or lack of fire-scar evidence and the presence of relatively even-aged forests at several mesic forest sites. Historical section corner data indicate that small amounts of these forest types occurred in the study area. Fire frequency and size declined dramatically circa 1900, coincident with the advent of commercial timber harvesting, although most fires, despite their reduced number and size, continued to burn in the late summer or fall.

https://www.fs.fed.us/pnw/fera/publications/fulltext/wrightandagee2004.pdf

Fire and vegetation history in the eastern cascade mountains, washington

Daily rain gauge data over Europe for the period from 1950 to 2009 were used to analyze changes in the duration of wet and dry spells. The duration of wet spells exhibits a statistically significant growth over northern Europe and central European Russia, which is especially pronounced in winter when the mean duration of wet periods increased by 15%–20%. In summer wet spells become shorter over Scandinavia and northern Russia. The duration of dry spells decreases over Scandinavia and southern Europe in both winter and summer. For the discrimination between the roles of a changing number of wet days and of a regrouping of wet and dry days for the duration of the period, the authors suggest a fractional truncated geometric distribution. The changing numbers of wet days cannot explain the long-term variability in the duration of wet and dry periods. The observed changes are mainly due to the regrouping of wet and dry days. The tendencies in duration of wet and dry spells have been analyzed for a numb...

Changes in the Duration of European Wet and Dry Spells during the Last 60 Years

The high-frequency and low-frequency variabilities, which are often misreproduced by the daily weather generators, have a significant effect on modelling weather-dependent processes. Three modifications are suggested to improve the reproduction of the both variabilities in a four-variate daily weather generator Met&Roll: (i) inclusion of the annual cycle of lag-0 and lag-1 correlations among solar radiation, maximum temperature and minimum temperature, (ii) use of the 3rd order Markov chain to model precipitation occurrence, (iii) applying the monthly generator (based on a first-order autoregressive model) to fit the low-frequency variability. The tests are made to examine the effects of the three new features on (i) a stochastic structure of the synthetic series, and on (ii) outputs from CERES-Wheat crop model (crop yields) and SAC-SMA rainfall-runoff model (monthly streamflow characteristics, distribution of 5-day streamflow) fed by the synthetic weather series. The results are compared with those obtained with the observed weather series. Results: (i) The inclusion of the annual cycle of the correlations has rather ambiguous effect on the temporal structure of the weather characteristics simulated by the generator and only insignificant effect on the output from either simulation model. (ii) Increased order of the Markov chain improves modelling of precipitation occurrence series (especially long dry spells), and correspondingly improves reliability of the output from either simulation model. (iii) Conditioning the daily generator on monthly generator has the most positive effect, especially on the output from the hydrological model: Variability of the monthly streamflow characteristics and the frequency of extreme streamflows are better simulated. (iv) Of the two simulation models, the improvements related to the three modifications are more pronounced in the hydrological simulations. This may be also due to the fact that the crop growth simulations were less affected by the imperfections of the unmodified version of Met&Roll.

High-Frequency and Low-Frequency Variability in Stochastic Daily Weather Generator and Its Effect on Agricultural and Hydrologic Modelling

Severe fire weather is a major determinant of fire size in coastal California; however, it is unclear to what extent antecedent climate also controls fire activity. This study investigates the relationship between fire activity and climate in central coastal and southern California. Climate variables included the Palmer Drought Severity Index (PDSI), total monthly precipitation, mean monthly maximum temperature and the autumn and winter Southern Oscillation Indices (SOI). For both the central coast and the south coast regions there was no significant relationship between growing season PDSI, precipitation or temperature and number of fires. When examined by season, summer temperatures were positively correlated with number of fires in the central coast and autumn PDSI and precipitation were negatively correlated with fire occurrence in the south coast region. Area burned was not correlated with any current year climate variables in southern California although, in the central coast, drought during spring and autumn were correlated, but explained less than 10% of the variation in the area burned. Although there was a modest relationship between the Southern Oscillation Index (SOI) and local climate parameters, there was only a relatively weak relationship with fire activity. The importance of autumn foehn winds is illustrated by the observation that large fires occur most commonly during the autumn, regardless of PDSI. Antecedent climate, however, does appear to play some role in determining the length of the fire season on these landscape as PDSI is consistently related to the occurrence of large fires that occur before or after the autumn months.

Impact of antecedent climate on fire regimes in coastal California

We examined the spatiotemporal patterns of fire in insular Southeast Asia from July 1996 to December 2001 using a set of consistent, nighttime fire observations provided by the Along Track Scanning Radiometer (ATSR) sensor. Monthly ATSR fire counts were analyzed relative to georeferenced climatic and land-cover data from a variety of sources. We found that fires were strongly correlated with Southern Oscillation Index (SOI) (r = −0.75) and Nino 3.4 index (r = 0.72) in forested land-cover types within the equatorial belt (5.5∘S–5.5∘N). Cross-correlation analysis revealed that detrended SOI was modestly correlated (r = 0.42) with detrended monthly fire count with a positive lag of four months. However, our analysis also revealed that fire counts reached their maximum 6 months before the absolute maximum of SOI. Annual sums of SOI (∑SOI) and fire counts revealed linearity for ∑SOI≤ 0. Overall, the results suggest that ENSO indices may have limited predictive utility at a monthly time scale, but that temporal aggregation and additional fire observations may enhance our capacity to forecast fires in different cover types based on ENSO data.

The Enso-Fire Dynamic in Insular Southeast Asia

Wildfires have long been an important environmental concern in Florida. Recent wildfires along the urban-rural interface of large cities in Florida have pointed to the need for an increased understanding of the physical and biological mechanisms that govern wildfire occurrence. Increased awareness of the relationships between global climate changes occurring in the tropics and their teleconnections outside the tropics dictate a reevaluation of the role of phenomena such as El Nino-Southern Oscillation on the risk of wildfire. One simple way of illustrating the relationship between ENSO and wildfire occurrence is the use of an Analysis of Variance (ANOVA) on wildfire data that has been categorized according to ENSO status (El Nino, La Nina, and neutral years). This research shows that a statistically significant relationship exists between ENSO conditions and annual wildfire occurrence in Florida when ENSO conditions are treated as a potential precursor to wildfire conditions. In particular, a statisticall...

A statistical relationship between the El Nino-Southern Oscillation and Florida wildfire occurrence.

The use of chain-dependent hydroclimatological models (sometimes referred to as ‘combined models’ or ‘two-part models’) in analysing daily precipitation requires that rainfall be modelled using both occurrence and intensity statistics. Markov processes in the context of precipitation climatology have been studied in such regions as monsoonal Asia, sub-Saharan Africa and South America. Many studies have indicated that the use of a first-order Markov model is often adequate when describing daily precipitation occurrences, particularly when working in temperate regions, but relatively little work has been done in the humid tropics regarding proper Markov model order, particularly in the western hemisphere. This research examines the occurrence characteristics of Costa Rican daily precipitation by comparing the Akaike and Bayesian information criteria (AIC and BIC) for three long-term meteorological stations. It is found that the most parsimonious models generally are those of first order (winter) or zero order (summer). Overall, the BIC yields less ambiguous results than the AIC, and thus, a higher level of model confidence is achieved when using the BIC as the model-order selection criteria. Copyright © 2000 Royal Meteorological Society

A note concerning the proper choice for Markov model order for daily precipitation in the humid tropics: a case study in Costa Rica

The use of chain-dependent hydroclimatological models (sometimes referred to as ‘combined models’ or ‘two-part models’) in analysing daily precipitation requires that rainfall be modelled using both occurrence and intensity statistics. Markov processes in the context of precipitation climatology have been studied in such regions as monsoonal Asia, sub-Saharan Africa and South America. Many studies have indicated that the use of a first-order Markov model is often adequate when describing daily precipitation occurrences, particularly when working in temperate regions, but relatively little work has been done in the humid tropics regarding proper Markov model order, particularly in the western hemisphere. This research examines the occurrence characteristics of Costa Rican daily precipitation by comparing the Akaike and Bayesian information criteria (AIC and BIC) for three long-term meteorological stations. It is found that the most parsimonious models generally are those of first order (winter) or zero order (summer). Overall, the BIC yields less ambiguous results than the AIC, and thus, a higher level of model confidence is achieved when using the BIC as the model-order selection criteria. Copyright © 2000 Royal Meteorological Society.

Short communication a note concerning the proper choice for markov model order for daily precipitation in the humid tropics: a case study in costa rica

The occurrence of tropical cyclones in the Caribbean and North Atlantic basins has been previously noted to have a significant effect both upon individual hydro-climatological events as well as on the quantity of annual precipitation experienced along the Pacific flank of Central America. A methodology for examining the so-called ‘indirect effects’ of tropical cyclones (i.e. those effects resulting from a tropical cyclone at a considerable distance from the area of interest) on a daily rainfall record is established, which uses a variant of contingency table analysis. The method is tested using a single station on the Pacific slope of Costa Rica. Employing daily precipitation records from Liberia, north-western Costa Rica (1964–1995), and historic storm tracks of tropical cyclones in the North Atlantic, it is determined that precipitation falling in coincidence with the passage of tropical depressions, tropical storms, and hurricanes accounts for approximately 15% of average annual precipitation. The greatest effects are associated with storms passing within 1300 km of the precipitation station, and are most apparent in the increased frequency of daily rainfall totals in the range of 40–60 mm, rather than in the largest daily totals. The complexity and nonstationarity of factors affecting precipitation in this region are reflected in the decline in the number of tropical cyclones and their significance to annual precipitation totals after 1980, simultaneous to an increase in annual precipitation totals. The methodology employed in this study is shown to be a useful tool in illuminating the indirect effects of tropical cyclones in the region, with the potential for application in other areas. Copyright  2005 Royal Meteorological Society.

The coincidence of daily rainfall events in Liberia, Costa Rica and tropical cyclones in the Caribbean basin

Targeting of stratigraphic traps is rapidly becoming a successful exploration strategy, especially in relatively mature basins where a high proportion of structural traps have been tested. The development of robust geological and trap models, integrated with the results of seismic inversion, are key steps in mitigating the larger uncertainty and risk associated with exploration for stratigraphic traps. This study demonstrates the benefit of a fully integrated workflow, involving the interpretation and analysis of geophysical and geological data, to ensure the development of a robust prospect model. In this case, a new stratigraphic trapping concept has been developed within the Upper Jurassic Hanifa Formation a unit which is generally considered to consist of low porosities based on existing well control.

Michael Harrison

Papers

A statistical relationship between the El Nino-Southern Oscillation and Florida wildfire occurrence.

A note concerning the proper choice for Markov model order for daily precipitation in the humid tropics: a case study in Costa Rica

Short communication a note concerning the proper choice for markov model order for daily precipitation in the humid tropics: a case study in costa rica

The coincidence of daily rainfall events in Liberia, Costa Rica and tropical cyclones in the Caribbean basin

An integrated approach to develop a self-sourcing, self-sealing stratigraphic prospect for the Hanifa Formation, offshore Bahrain