Search Results

You are looking at 31 - 40 of 21,017 items for :

  • All content x
Clear All
Kaushik Gopalan, Nai-Yu Wang, Ralph Ferraro, and Chuntao Liu

1. Introduction The Tropical Rainfall Measurement Mission (TRMM) Microwave Imager (TMI), a nine-channel (10–85 GHz) dual-polarized microwave radiometer, is one of five instruments aboard the TRMM spacecraft and is used to provide rainfall estimates over the tropics. The TRMM 2A12 data product, which contains instantaneous rainfall estimates from TMI, uses separate algorithms for land, ocean, and coastal regions. Separate algorithms are required for these three cases because of the major

Full access
Richard L. Bankert and Michael Hadjimichael

( Bocchieri and Glahn 1972 ; Bocchieri et al. 1974 ). MOS schemes are still applied to many of today’s numerical models. Along with NWP model data, observations are also used to develop MOS regression equations for ceiling and visibility, temperature and dewpoint, wind speed and direction, probability of precipitation, precipitation amount, and cloud cover. MOS techniques, applied to various NWP models, have also been used to develop specific algorithms to forecast the occurrence of Levante wind regimes

Full access
Srdjan Dobricic

removed in the “weak-constraint” 4DVAR algorithm. If the state vector is defined on the model space, the size of the parameter space with the imperfect model may increase significantly (e.g., Bennett 1992 ; Courtier 1997 ), although the computational effort can be made equal to that of the 4DVAR with the perfect model assumption ( Tremolet 2006 ). The problem of the size of the parameter space may be a minor problem in operational meteorology and oceanography, because in that case the assimilation

Full access
Lei Han, Shengxue Fu, Lifeng Zhao, Yongguang Zheng, Hongqing Wang, and Yinjing Lin

-based severe weather detection algorithms, such as hail detection algorithms ( Joe et al. 2004 ; Wilson et al. 2004 ). In addition to providing useful short-term forecasting, or nowcasting, capabilities, storm identification, tracking, and forecasting algorithms can also provide storm data suitable for the study of the physical mechanisms of storm evolution ( Dixon and Wiener 1993 ). Many nowcasting algorithms using radar data have been developed over the past decades. These algorithms can be classified

Full access
Arthur T. DeGaetano, Brian N. Belcher, and Pamela L. Spier

accretion fields can also be generated using the hybrid approach. When coupled with the electric distribution system models, such data, which are currently lacking, will enable utilities to assess the economic value of management practices such as tree trimming and distribution system maintenance. 2. Precipitation-type models Cortinas and Baldwin (1999) describe and compare the performance of six precipitation-type forecast algorithms. Collectively, the methods were better able to forecast the

Full access
Lance O’Steen and David Werth

needed that can optimize an extremely complex model with a large number of adjustable parameters. Evolutionary methods provide such an optimization procedure ( Fogel 2000 ). We use “evolutionary” here instead of “genetic” because only mutation operators are employed in the computational algorithm (genetic methods typically allow mating or recombination processes). In addition, real-valued parameters are being perturbed as opposed to the binary string sequences typically employed in genetic algorithms

Full access
Tijana Janjić, Lars Nerger, Alberta Albertella, Jens Schröter, and Sergey Skachko

1. Introduction The ensemble-based Kalman filter approach has been widely used for data assimilation in both meteorology and oceanography (see, e.g., Houtekamer and Mitchell 1998 , 2001 ; Brankart et al. 2003 ). In the ensemble Kalman filter algorithms, the forecast error covariance matrix is approximated by a covariance matrix whose rank is 1 less than the number of ensemble members. For computational tractability, the number of ensemble members, and therefore the rank of the covariance

Full access
E. Yoshizawa, K. Shimada, and K. H. Cho

Ocean. Sea ice thickness can also be estimated using brightness temperature data measured by satellite passive microwave radiometers, such as the Advanced Microwave Scanning Radiometer-2 (AMSR2), based on an empirical relation between emissivity and sea ice thickness. Unlike the altimetry method, this microwave method enables us to monitor sea ice thickness in near–real time. To date, the thickness algorithm has been well established for thin ice using a polarization ratio (PR) of brightness

Full access
James Holte and Lynne Talley

Southern Ocean did not produce realistic MLDs. This paper introduces a new algorithm for finding the MLD of individual profiles. The algorithm builds on traditional threshold and gradient methods by tying its estimate of the MLD to physical features in the profile. It accomplishes this by first modeling the profile’s general shape; it approximates the seasonal thermocline and the mixed layer with best-fit lines. It then assembles a suite of possible MLD values by calculating the threshold and gradient

Full access
James M. Kurdzo and Robert D. Palmer

sufficient; optimization algorithms [specifically genetic algorithms (GAs)] are capable of handling these problems ( Lieska et al. 1998 ). Lieska et al. (1998) argued that genetic algorithms process the computer’s representation of potential solutions directly, leading to a more rapid convergence to a solution. A fixed number of base stations (possible siting locations) in a gridded format were used, further limiting the computational complexity. Genetic algorithms have also been used by Du and Bigham

Full access