Search Results

You are looking at 21 - 26 of 26 items for

  • Author or Editor: Christopher W. Fairall x
  • Refine by Access: Content accessible to me x
Clear All Modify Search
James B. Edson
,
Venkata Jampana
,
Robert A. Weller
,
Sebastien P. Bigorre
,
Albert J. Plueddemann
,
Christopher W. Fairall
,
Scott D. Miller
,
Larry Mahrt
,
Dean Vickers
, and
Hans Hersbach

Abstract

This study investigates the exchange of momentum between the atmosphere and ocean using data collected from four oceanic field experiments. Direct covariance estimates of momentum fluxes were collected in all four experiments and wind profiles were collected during three of them. The objective of the investigation is to improve parameterizations of the surface roughness and drag coefficient used to estimate the surface stress from bulk formulas. Specifically, the Coupled Ocean–Atmosphere Response Experiment (COARE) 3.0 bulk flux algorithm is refined to create COARE 3.5. Oversea measurements of dimensionless shear are used to investigate the stability function under stable and convective conditions. The behavior of surface roughness is then investigated over a wider range of wind speeds (up to 25 m s−1) and wave conditions than have been available from previous oversea field studies. The wind speed dependence of the Charnock coefficient α in the COARE algorithm is modified to , where m = 0.017 m−1 s and b = −0.005. When combined with a parameterization for smooth flow, this formulation gives better agreement with the stress estimates from all of the field programs at all winds speeds with significant improvement for wind speeds over 13 m s−1. Wave age– and wave slope–dependent parameterizations of the surface roughness are also investigated, but the COARE 3.5 wind speed–dependent formulation matches the observations well without any wave information. The available data provide a simple reason for why wind speed–, wave age–, and wave slope–dependent formulations give similar results—the inverse wave age varies nearly linearly with wind speed in long-fetch conditions for wind speeds up to 25 m s−1.

Full access
James B. Edson
,
Venkata Jampana
,
Robert A. Weller
,
Sebastien P. Bigorre
,
Albert J. Plueddemann
,
Christopher W. Fairall
,
Scott D. Miller
,
Larry Mahrt
,
Dean Vickers
, and
Hans Hersbach
Full access
Paul J. Neiman
,
Natalie Gaggini
,
Christopher W. Fairall
,
Joshua Aikins
,
J. Ryan Spackman
,
L. Ruby Leung
,
Jiwen Fan
,
Joseph Hardin
,
Nicholas R. Nalli
, and
Allen B. White

Abstract

To gain a more complete observational understanding of atmospheric rivers (ARs) over the data-sparse open ocean, a diverse suite of mobile observing platforms deployed on NOAA’s R/V Ronald H. Brown (RHB) and G-IV research aircraft during the CalWater-2015 field campaign was used to describe the structure and evolution of a long-lived AR modulated by six frontal waves over the northeastern Pacific during 20–25 January 2015. Satellite observations and reanalysis diagnostics provided synoptic-scale context, illustrating the warm, moist southwesterly airstream within the quasi-stationary AR situated between an upper-level trough and ridge. The AR remained offshore of the U.S. West Coast but made landfall across British Columbia where heavy precipitation fell. A total of 47 rawinsondes launched from the RHB provided a comprehensive thermodynamic and kinematic depiction of the AR, including uniquely documenting an upward intrusion of strong water vapor transport in the low-level moist southwesterly flow during the passage of frontal waves 2–6. A collocated 1290-MHz wind profiler showed an abrupt frontal transition from southwesterly to northerly flow below 1 km MSL coinciding with the tail end of AR conditions. Shipborne radar and disdrometer observations in the AR uniquely captured key microphysical characteristics of shallow warm rain, convection, and deep mixed-phase precipitation. Novel observations of sea surface fluxes in a midlatitude AR documented persistent ocean surface evaporation and sensible heat transfer into the ocean. The G-IV aircraft flew directly over the ship, with dropsonde and radar spatial analyses complementing the temporal depictions of the AR from the RHB. The AR characteristics varied, depending on the location of the cross section relative to the frontal waves.

Full access
James N. Moum
,
Simon P. de Szoeke
,
William D. Smyth
,
James B. Edson
,
H. Langley DeWitt
,
Aurélie J. Moulin
,
Elizabeth J. Thompson
,
Christopher J. Zappa
,
Steven A. Rutledge
,
Richard H. Johnson
, and
Christopher W. Fairall

The life cycles of three Madden–Julian oscillation (MJO) events were observed over the Indian Ocean as part of the Dynamics of the MJO (DYNAMO) experiment. During November 2011 near 0°, 80°E, the site of the research vessel Roger Revelle, the authors observed intense multiscale interactions within an MJO convective envelope, including exchanges between synoptic, meso, convective, and turbulence scales in both atmosphere and ocean and complicated by a developing tropical cyclone. Embedded within the MJO event, two bursts of sustained westerly wind (>10 m s−1; 0–8-km height) and enhanced precipitation passed over the ship, each propagating eastward as convectively coupled Kelvin waves at an average speed of 8.6 m s−1. The ocean response was rapid, energetic, and complex. The Yoshida–Wyrtki jet at the equator accelerated from less than 0.5 m s−1 to more than 1.5 m s−1 in 2 days. This doubled the eastward transport along the ocean's equatorial waveguide. Oceanic (subsurface) turbulent heat fluxes were comparable to atmospheric surface fluxes, thus playing a comparable role in cooling the sea surface. The sustained eastward surface jet continued to energize shear-driven entrainment at its base (near 100-m depth) after the MJO wind bursts subsided, thereby further modifying sea surface temperature for a period of several weeks after the storms had passed.

Full access
Sue Chen
,
Maria Flatau
,
Tommy G. Jensen
,
Toshiaki Shinoda
,
Jerome Schmidt
,
Paul May
,
James Cummings
,
Ming Liu
,
Paul E. Ciesielski
,
Christopher W. Fairall
,
Ren-Chieh Lien
,
Dariusz B. Baranowski
,
Nan-Hsun Chi
,
Simon de Szoeke
, and
James Edson

Abstract

The diurnal variability and the environmental conditions that support the moisture resurgence of MJO events observed during the Cooperative Indian Ocean Experiment on Intraseasonal Variability (CINDY)/DYNAMO campaign in October–December 2011 are investigated using in situ observations and the cloud-resolving fully air–ocean–wave Coupled Ocean–Atmosphere Mesoscale Prediction System (COAMPS). Spectral density and wavelet analysis of the total precipitable water (TPW) constructed from the DYNAMO soundings and TRMM satellite precipitation reveal a deep layer of vapor resurgence during the observed Wheeler and Hendon real-time multivariate MJO index phases 5–8 (MJO suppressed phase), which include diurnal, quasi-2-, quasi-3–4-, quasi-6–8-, and quasi-16-day oscillations. A similar oscillatory pattern is found in the DYNAMO moorings sea surface temperature analysis, suggesting a tightly coupled atmosphere and ocean system during these periods. COAMPS hindcast focused on the 12–16 November 2011 event suggests that both the diurnal sea surface temperature (SST) pumping and horizontal and vertical moisture transport associated with the westward propagating mixed Rossby–Gravity (MRG) waves play an essential role in the moisture resurgence during this period. Idealized COAMPS simulations of MRG waves are used to estimate the MRG and diurnal SST contributions to the overall moisture increase. These idealized MRG sensitivity experiments showed the TPW increase varies from 9% to 13% with the largest changes occurring in the simulations that included a diurnal SST variation of 2.5°C as observed.

Full access
Madison J. Post
,
Christopher W. Fairall
,
Jack B. Snider
,
Yong Han
,
Allen B. White
,
Warner L. Ecklund
,
Klaus M. Weickmann
,
Patricia K. Quinn
,
Daniel I. Cooper
,
Steven M. Sekelsky
,
Robert E. McIntosh
,
Peter Minnett
, and
Robert O. Knuteson

Twelve national research organizations joined forces on a 30-day, 6800 n mi survey of the Central and Tropical Western Pacific on NOAA's Research Vessel Discoverer. The Combined Sensor Program (CSP), which began in American Samoa on 14 March 1996, visited Manus Island, Papua New Guinea, and ended in Hawaii on 13 April, used a unique combination of in situ, satellite, and remote sensors to better understand relationships between atmospheric and oceanic variables that affect radiative balance in this climatically important region. Besides continuously measuring both shortwave and longwave radiative fluxes, CSP instruments also measured most other factors affecting the radiative balance, including profiles of clouds (lidar and radar), aerosols (in situ and lidar), moisture (balloons, lidar, and radiometers), and sea surface temperature (thermometers and Fourier Transform Infrared Radiometers). Surface fluxes of heat, momentum, and moisture were also measured continuously. The Department of Energy's Atmospheric Radiation Measurement Program used the mission to validate similar measurements made at their CART site on Manus Island and to investigate the effect (if any) of large nearby landmasses on the island-based measurements.

Full access