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Jean Fitzmaurice
and
Rafael L. Bras

forecast), can then be computed. The analysis increment is relevant where there are sufficient observations. In regions of few observations, the analysis increment will be small because unless the observations are very accurate, there will not be much difference between the model first guess and the analysis. The data assimilation (DA) system itself has been used to monitor observations and data quality control ( Hollingsworth et al. 1986 ) by computing statistics involving observations, such as

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S. Vannitsem
and
C. Nicolis

1. Introduction Operational numerical weather (or climate) predictions deteriorate as a function of lead time because of the presence of modeling and initial condition errors. To partly correct this decrease of skill postprocessors are commonly used based on (linear or nonlinear) statistical methods (see, e.g., Casaioli et al. 2003 ; Kalnay 2003 ; Marzban 2003 ; Wilks 2006 ). These are usually referred to as model output statistics (MOS) techniques. One of the most popular approaches

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Prashant D. Sardeshmukh
and
Philip Sura

et al. 2001 ; Newman and Sardeshmukh 2008 ), and the competitiveness of week-2 and week-3 linear forecast models with comprehensive numerical weather prediction (NWP) models ( Winkler et al. 2001 ; Newman et al. 2003 ). Even on the time scales of daily weather, linear stochastically forced (LSF) models of the form (1) , although not as accurate as NWP models for daily predictions, are realistic enough to capture many features of the second-order statistics of observed synoptic variability

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Maxime Perron
and
Philip Sura

(likely owing to the scarcity of moisture near the troposphere), so we cannot analyze the range between 300 and 100 hPa for this variable. Petoukhov et al. (2008) looked at this variable. b. Methodology: Non-Gaussian statistics 1) Higher statistical moments In statistics, distributions can be described quantitatively by the central moments, or moments about the mean. The central moments are calculated using the anomalies from a mean state of a time series. Therefore, the first central moment

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R. W. Higgins
,
V. B. S. Silva
,
V. E. Kousky
, and
W. Shi

1. Introduction A major challenge for the climate community is to provide information that decision makers can directly apply to reduce vulnerability to climate risk. While probabilistic forecasts of seasonal mean quantities (such as precipitation and surface temperature over the conterminous United States) have proven utility, they do not address questions relating to the specific character of the daily weather statistics within the season. User requests for products that expand beyond

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Francesco Fedele
and
Felice Arena

equivalent to a succession of random triangle storms. This type of equivalence defines the probabilistic structure of the ETS model, which depends on wave data only via the observed significant wave height exceedance P ( h ) = Pr( H s > h ) and the conditional average duration b ( a ) = B | A = a , both estimated via regression. Then, the estimates of wave extremes and their associated statistics simply follow from the density p A with no need for data fitting. In particular, Boccotti (2000

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Pavlos Kollias
and
Bruce Albrecht

and energy transport processes relative to the total cloud amount and basic statistics on the vertical velocities in these clouds are lacking. The representation of fair-weather cumuli clouds in numerical models is challenging because of the scale of these clouds and their intimate involvement with small-scale processes in the boundary layer, which are also difficult to parameterize. The vertical transport due to cumulus clouds in large-scale models is often parameterized using a mass

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R. S. Gibson
,
C. Swan
, and
P. S. Tromans

1. Introduction The statistics of wave crest elevation are fundamental to the design of both deep-water offshore structures and shallow-water coastal structures. In the case of fixed structures, deck elevations are typically set to maintain an effective air gap, thereby preventing the impact of the largest wave crests on the underside of the structure. In addition, individual members must be designed to support the applied loads, with the maximum drag forces arising beneath the largest wave

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Nina Schuhen
,
Thordis L. Thorarinsdottir
, and
Tilmann Gneiting

statistics (EMOS) or nonhomogeneous Gaussian regression ( Gneiting et al. 2005 ; Thorarinsdottir and Gneiting 2010 ). The EMOS technique transforms a raw ensemble forecast into a predictive probability density function, and simultaneously corrects for biases and dispersion errors. EMOS methods have been developed for temperature and surface pressure ( Gneiting et al. 2005 ; Hagedorn et al. 2008 ; Kann et al. 2009 ), where the predictive density is normal and the method is often referred to as

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Jung-Hoon Kim
and
Hye-Yeong Chun

annual report of the National Transportation Safety Board ( NTSB 2009 ), from 1996 to 2005 turbulence was the leading cause of weather-related aircraft accidents in the United States. Over South Korea, from 1957 to the present turbulence has accounted for about 24% of the aircraft accidents caused by weather, making it the largest contributor to weather-related accidents [statistics from the Aviation and Railway Accident Investigation Board (ARAIB), information online at http

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