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Wildfires are a natural phenomenon that strongly impacts the environment. Many terrestrial ecosystems depend on fire to maintain their ecological equilibrium and biodiversity, but new destructive fire patterns, often associated with land management practices and rapid climate change, have been degrading soil and water resources, increasing erosion by wind, precipitation and floods, decreasing biodiversity and contributing to desertification. Furthermore, pyrogenic emissions from biomass burning are an important source of atmospheric pollution and they impact the radiative balance of the troposphere, strongly contributing to the greenhouse effect. The objective of this research was to investigate the impact of climate variability on geographic, ecological, seasonal and inter-annual distributions of fires and correspondent pyrogenic emissions, across a variety of ecosystems. With this purpose, 10 years of world, monthly, 1°x1° gridded data, from the Global Fire Emissions Database, were compared with land-cover data, from the Goddard Institute of Space Studies, and with weather data, from the European Centre for Medium Range Weather Forecasting, the Global Precipitation Climatology Centre and the Global Hydrology Resource Centre. Overall, the climate parameters significantly correlated with carbon emissions were air and soil temperature, air and soil humidity, rainfall, wind speed and lightning density during the fire season, and also precipitation and snow cover up to 6 months before the fire season. Good statistical quantitative models of carbon emissions (correlations above 70%, and up to 95%, between estimated and predicted values, with residuals normally distributed) using humidity, temperature or lagged rainfall as predictors, were found almost exclusively in tropical grasslands, shrublands and woodlands, especially in Africa, where fire behaviour was more regular. In boreal and temperate forests and woodlands, where fire patterns were irregular and fire returning periods were larger, there were not enough fires, in 10 years of data, to obtain useful predictive statistical models. The fire models presented here, together with the quantitative statistical relationships found between climate and fire patterns, in different land ecosystems, are apt to be used in predictive climate models, land management, fire risk assessment and mitigation of climate change.

Approved for Public Release; Distribution is Unlimited / The impact of non-conventional observations and increased horizontal resolution on the numerical weather prediction (NWP) system of the National Center for Aeronautic Meteorology and Climatology of the Italian Air Force (CNMCA) has been investigated. The present study is part of ongoing research activities whose goal is the improvement of CNMCA's operational numerical weather prediction capabilities through the assimilation of non-conventional observations. Additional data derived from satellite observations, such as 10 m wind retrieved from Quikscat polar-orbit satellite, atmospheric motion vectors (AMVs) from Meteosat geostationary satellites and manual and automated aircraft observations were used. The NWP system, which is in operational use, is based on an "observation space" version of the 3D-Var method for the objective analysis component (3D-PSAS), while the prognostic component is based on the High Resolution Regional Model (HRM) of the German Meteorological Service (DWD). The analysis and forecast fields derived from the NWP system were objectively evaluated through comparisons with radiosonde and conventional surface observations. Comparisons with parallel runs of the HRM model starting from the 3D-Var operational analysis have showed that each of those observations have a measurable positive impact on forecast skill. / Captain, Italian Air Force

We have developed, tested, and operationally implemented a web based system for collecting and analyzing in nearreal time weather forecast and observational data to assess: (a) the performance of forecasts; and (b) the operational impacts of forecasts. A major goal of the system is to quantify the impacts of weather forecasts on the planning, execution, and outcomes of military operations. Our tests and implementation were focused on the METOC support provided by Naval Pacific Meteorology and Oceanography Detachment (NPMOD) Fallon to Naval Strike and Air Warfare Center (NSAWC) operations at Naval Air Station Fallon. Data are collected by NPMOD Fallon and entered via a web interface into a database at the Naval Postgraduate School (NPS) where the data are analyzed and results are reported in near-real time. The results include quantitative assessments of: (1) forecasts used in planning NSAWC missions; (2) changes made during mission planning in response to forecasted weather; (3) deviations from mission plans that occurred in response to weather conditions actually encountered; (4) positive and negative impacts on missions due to forecasts; (5) METOC Tactical Decision Aid forecast accuracy and mission impacts; and (6) forecast performance and mission impacts with respect to specific weather factors.

Within the Pacific Air Forces (PACAF) area of responsibility, tropical deep convection that is not associated with tropical cyclones can cause significant impacts to operations. In this study, convective indices calculated from five sites in the central and western tropical North Pacific are examined with respect to their ability to predict the onset and intensity of deep convection. Two predictands are utilized: measures of convection derived from surface weather observations and the Naval Research Laboratory (NRL) Blended Rainrate estimates, which are derived from infrared and microwave satellite observations and interpolated to the five sites. Eighteen indices derived from rawinsondes are ranked by predictive skill for specific locations and seasons. Indices that exhibit significant skill are used in a discriminant analysis to define a multivariate experimental tropical convective index, which is then evaluated for each region and season. The multivariate index was not able to discriminate between convective and non-convective environments over the central North Pacific. Although the multivariate index exhibited skill for sites in the tropical western North Pacific during summer, it did not perform better than the highest-ranked single indices. For many of the locations and seasons evaluated, the Severe Weather Threat (SWEAT) Index exhibited the most skill.

Three sets of algorithms are formulated for use in a variety of models :- * Ship performance algorithms. * Optimisation algorithms. * Environmental data. Optimisation models are constructed for deterministic minima, with time, fuel and cost objective functions. Models are constructed for an actual ship, (M. V. DART ATLANTIC), and realistic working solutions are obtained based on real-time weather information, simulating an actual on-board, computer based system, using dynamic programming. Several combinations of algorithm types are used in the the models, enabling comparisons of effectiveness. Thus, the ship performance algorithms incorporate severally; simple ship speed loss curves, ship resistance, ship motions and ship motion criteria databases devised from a linear seakeeping model. Limitations of the models are discussed from the routeing examples given. State space restrictions and originally devised methods to aid convergence in the models are discussed. Extension of the forecasted environmental data is achieved by a variety of methods and comparisons sought. In particular ECMWF surface pressure files are interrogated to produce sea wave fields over the extended period, establishing main disturbance centres. The variety of algorithms formulated in this work has facilitated real-time comparisons, this is particularly effective in route-updating. The development of these models and the methods used to extend the forecast period, and the comparisons and associated results stemming from these models are viewed as an original contribution to real-time weather routeing of ships.

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During summertime Saharan heat low, a region of low pressure system, is formed as a result of large solar insolation superimposed with the convergence of west African South westerly monsoon flow and dry north easterly Harmattan flow along the intertropical discontinuity. This region plays significant role in the initiation and development of the West African Monsoon. The Saharan heat low is co-located with region of maximum load of dust aerosol which is known to have impact on the climate. Further the Saharan heat low plays key role in the global circulations including its role in formation of African Easterly Jets and African Easterly Waves. Despite its role in influencing the dynamic and thermodynamics of the region, the Saharan Heat low is not extensively studied partly due to lack of comprehensive data due to the harsh weather conditions of the region. Climate system of the Saharan heat low is a result of different complicated atmospheric and land surface processes most dominantly immense solar input at the surface, large convergence of sensible heat flux from the ground into the atmosphere, and low level cooling by horizontal advection of moisture from the surrounding area. These dynamical and thermodynamical processes take part in transport and redistribution of heat and transport of the moisture in the region. This thesis aims at providing a detailed analysis of the physical processes responsible for the development, maintenance, and decadal variability of the Saharan heat low region. I investigate three specific aspects of the Saharan heat low region. 1. Heat and Moisture Budget: Heat and moisture are drivers of dynamics and thermodynamics of a region. Previous studies presented heat and moisture budget of the Saharan heat Low without attributing to the detailed mechanisms by which heat and moisture is transported from the surrounding area to the Sahara heat low and vice versa. This thesis presents components of heat and moisture budget resulting from mean and transient flows that are responsible for heating/cooling and moistening/drying of the Sahara heat low region. Heat and moisture budget are derived using commonly used reanalyses simulations (ERA-I, NCEP, and MERRA) and comparison of the results between the three reanalyses are made. I investigate the mechanisms responsible for the decadal variability of intensity of the Sahara heat low and provide implications. This work has not been done previously to the best of knowledge. 2. Role of Dust and Water vapor in controlling the radiative flux: Recent studies show that water vapour greenhouse forcing is responsible for intensification of the Saharan heat low and as a consequence recovery of Sahel rainfall. Dust aerosol is known to have impact on the climate through its interaction with radiation. The large dust load in the Sahara heat low makes it important in controlling the variability in the radiative budget of the region. Previous studies have quantified the role of dust and water vapour in the region in controlling day to day variability in the radiative flux in the heat low. There is still uncertainty in the radiative forcing and associated variability partly due to lack of observational data. Furthermore separating the radiative effect of dust from that of water vapour is challenging due to the co-variability of dust and water vapour. This thesis quantifies separate and combined effect of dust and water vapour in controlling the radiative flux of the Saharan heat low using the recently made FENNEC observations of meteorological variables and dust loading. Theoretical experiments are made to study sensitivity of radiative flux to variations in dust and water vapour. 3. Characteristics of convective density currents: Convective down drafting density currents (cold pools) are ubiquitous features of the Saharan Heat low region which are shown to play important role in the transport of moisture and emission of dust in the region. Despite this, the characteristics of these atmospheric processes are not well studied in the Sahara Heat Low. Improving our knowledge of properties of convective density currents is imperative to better understand atmospheric processes within boundary layer of the Saharan heat low and thus improve model simulation performance. Here I provide magnitude, spatial distribution, and seasonal variability of cold pools using data from the Automatic weather Station (AWS) spread over the Sahara desert. I implement a unique identification method which is further verified by satellite observations of cold pool signatures. Once cold pools are identified at all stations, statistical description of the occurrence frequency and distribution are presented. Finally I asses reanalyses model simulation of convection triggered cold pool outflows through comparison with measurements.

Wong, Chun Yin. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 45-46). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Weather Risks and Weather Derivatives --- p.4 / Chapter 2.1 --- Weather Risk --- p.4 / Chapter 2.2 --- Weather Derivatives --- p.6 / Chapter 2.3 --- Importance of Long Term Forecasting --- p.7 / Chapter 3 --- Modeling the Temperature --- p.9 / Chapter 3.1 --- Stationary Long-Memory Time Series Model --- p.13 / Chapter 3.2 --- Use of Temporal Aggregation Model --- p.19 / Chapter 4 --- Weather Derivative Valuation Models --- p.26 / Chapter 4.1 --- List of Assumptions --- p.27 / Chapter 4.2 --- Valuation Formula --- p.30 / Chapter 4.3 --- Forecasting power of daily temperature model --- p.32 / Chapter 4.4 --- Empirical Result --- p.37 / Chapter 5 --- Summary and Conclusion --- p.43 / Bibliography --- p.45