Search Results

You are looking at 11 - 14 of 14 items for

  • Author or Editor: Jonathan D. Kahl x
  • Refine by Access: All Content x
Clear All Modify Search
Wessam Z. Daoud, Jonathan D. W. Kahl, and Jugal K. Ghorai

Abstract

A large set of 10-day, quasi-two-dimensional atmospheric trajectory model data is used to compute Lagrangian autocorrelation functions for horizontal velocity components and to determine their integral timescale T L. The objectives of the study are to investigate the seasonal, interannual, and altitudinal behavior of T L and to present the Lagrangian autocorrelation functions corresponding to synoptic-scale flow. Results indicate that the integral timescale T L ranges from 15 to 24 h, with values for the meridional velocity component that are 10%–25% less than values for the zonal velocity component. The Lagrangian autocorrelation functions are modeled using Gaussian and second-order autoregressive autocorrelation models. The model fits to the observed autocorrelation functions were found to be of similar form to those determined for a 1-yr set of three-dimensional trajectory data, suggesting that these functions are robust with respect to synoptic-scale, tropospheric flow.

Full access
Jonathan D. W. Kahl, Brandon R. Selbig, and Austin R. Harris

ABSTRACT

Wind gusts are common to everyday life and affect a wide range of interests including wind energy, structural design, forestry, and fire danger. Strong gusts are a common environmental hazard that can damage buildings, bridges, aircraft, and trains, and interrupt electric power distribution, air traffic, waterways transport, and port operations. Despite representing the component of wind most likely to be associated with serious and costly hazards, reliable forecasts of peak wind gusts have remained elusive. A project at the University of Wisconsin–Milwaukee is addressing the need for improved peak gust forecasts with the development of the meteorologically stratified gust factor (MSGF) model. The MSGF model combines gust factors (the ratio of peak wind gust to average wind speed) with wind speed and direction forecasts to predict hourly peak wind gusts. The MSGF method thus represents a simple, viable option for the operational prediction of peak wind gusts. Here we describe the results of a project designed to provide the site-specific gust factors necessary for operational use of the MSGF model at a large number of locations across the United States. Gust web diagrams depicting the wind speed– and wind direction–stratified gust factors, as well as peak gust climatologies, are presented for all sites analyzed.

Full access
Jonathan D. Kahl, Mark C. Serreze, Spencer Shiotani, Suzanne M. Skony, and Russell C. Schnell

Two new databases containing Arctic in situ meteorological soundings have been constructed and are now available for distribution to interested researchers. The Historical Arctic Rawinsonde Archive is a comprehensive collection of over 1.2 million rawinsonde soundings north of 65°N. For most stations the record begins in 1958 and extends to 1987; however, for some stations the record begins as early as 1948. The Ptarmigan Dropsonde Archive contains more than 10 000 lower-tropospheric soundings over the Beaufort Sea and western Arctic Ocean during the period 1950–1961.

Full access
Jonathan D. W. Kahl, Nina A. Zaitseva, V. Khattatov, R. C. Schnell, Dina M. Bacon, Jason Bacon, V. Radionov, and M. C. Serreze

An historical archive of over 25 000 radiosonde observations from the former Soviet “North Pole” series of drifting ice stations has been compiled and made available to interested researchers. This archive is the only long-term set of meteorological sounding data over the Arctic Ocean. The digital archive is a result of the multiyear, collaborative efforts of a group of United States and Russian scientists and keypunch operators working under the auspices of Working Group VIII, an area of study within the United States–Russian Federation Agreement for Protection of the Environment and Natural Resources. The archive contains soundings from 21 drifting stations over the period 1954–90 and is being distributed by the National Snow and Ice Data Center in Boulder, Colorado.

Full access