Search Results

You are looking at 1 - 4 of 4 items for

  • Author or Editor: B. A. Ridley x
  • Refine by Access: All Content x
Clear All Modify Search
B. A. Ridley
and
F. E. Grahek

Abstract

Details of a reaction vessel suitable for atmospheric measurements of nitric oxide at parts per trillion mixing ratios using the chemiluminescent reaction with ozone are provided. It is designed to operate at an ambient air flow of 1 standard liter per minute, much lower than most current high performance instruments. The savings in weight, space and power for a complete instrument allow obvious advantages for multispecies measurements using smaller aircraft.

Full access
B. A. Ridley
,
F. E. Grahek
, and
J. G. Walega

Abstract

An instrument for tropospheric O3 measurements based on the chemiluminescent reaction between nitric oxide and ozone is described. It was designed as part of a larger instrument package for simultaneous measurements of NO, NO2, NO y and O3 using smaller aircraft. The sensitivity of the O3 instrument is 2000 counts per second per ppbv O3, giving very high signal-to-noise ratios and a detection limit well below 0.1 ppbv. The instrument has been used in several research programs using the NCAR Sabreliner jet aircraft, and some results from these flights are presented. As configured for these flights, the instrument is operated with a 2-s integration time. However, suitable and readily made changes in operating conditions should allow sufficiently fast response for eddy correlation flux measurements from an aircraft or in ground-based programs.

Full access
D. S. Wratt
,
R. N. Ridley
,
M. R. Sinclair
,
H. Larsen
,
S. M. Thompson
,
R. Henderson
,
G. L. Austin
,
S. G. Bradley
,
A. Auer
,
A. P. Sturman
,
I. Owens
,
B. Fitzharris
,
B. F. Ryan
, and
J.-F. Gayet

The Southern Alps Experiment is being mounted to study the influence of New Zealand's Southern Alps on local weather and climate. This paper describes these alpine influences and outlines proposed field and modeling experiments. Experiment goals include understanding and quantifying factors that govern the intensity and spatial distribution of heavy rainfall, the west to east distribution of precipitation across the mountains, and the intensity of lee wind storms and warming. Linked research will explore the use of deterministic rainfall models to predict river flows from mountain watersheds.

Full access
T. C. Johns
,
C. F. Durman
,
H. T. Banks
,
M. J. Roberts
,
A. J. McLaren
,
J. K. Ridley
,
C. A. Senior
,
K. D. Williams
,
A. Jones
,
G. J. Rickard
,
S. Cusack
,
W. J. Ingram
,
M. Crucifix
,
D. M. H. Sexton
,
M. M. Joshi
,
B.-W. Dong
,
H. Spencer
,
R. S. R. Hill
,
J. M. Gregory
,
A. B. Keen
,
A. K. Pardaens
,
J. A. Lowe
,
A. Bodas-Salcedo
,
S. Stark
, and
Y. Searl

Abstract

A new coupled general circulation climate model developed at the Met Office's Hadley Centre is presented, and aspects of its performance in climate simulations run for the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4) documented with reference to previous models. The Hadley Centre Global Environmental Model version 1 (HadGEM1) is built around a new atmospheric dynamical core; uses higher resolution than the previous Hadley Centre model, HadCM3; and contains several improvements in its formulation including interactive atmospheric aerosols (sulphate, black carbon, biomass burning, and sea salt) plus their direct and indirect effects. The ocean component also has higher resolution and incorporates a sea ice component more advanced than HadCM3 in terms of both dynamics and thermodynamics. HadGEM1 thus permits experiments including some interactive processes not feasible with HadCM3. The simulation of present-day mean climate in HadGEM1 is significantly better overall in comparison to HadCM3, although some deficiencies exist in the simulation of tropical climate and El Niño variability. We quantify the overall improvement using a quasi-objective climate index encompassing a range of atmospheric, oceanic, and sea ice variables. It arises partly from higher resolution but also from greater fidelity in modeling dynamical and physical processes, for example, in the representation of clouds and sea ice. HadGEM1 has a similar effective climate sensitivity (2.8 K) to a CO2 doubling as HadCM3 (3.1 K), although there are significant regional differences in their response patterns, especially in the Tropics. HadGEM1 is anticipated to be used as the basis both for higher-resolution and higher-complexity Earth System studies in the near future.

Full access