Search Results

You are looking at 51 - 60 of 3,518 items for :

  • Journal of the Atmospheric Sciences x
  • Refine by Access: All Content x
Clear All
Yi Ming, V. Ramaswamy, Leo J. Donner, Vaughan T. J. Phillips, Stephen A. Klein, Paul A. Ginoux, and Larry W. Horowitz

concentrations using BL95 ( Ming et al. 2005 ). The large-scale processes over the NH midlatitude land are generally weaker, producing N d less than 50 cm −3 . These are smaller than 100–150 cm −3 diagnosed using BL95 . Because the measurements presented in Leaitch et al. (1992) showed strong seasonal variations and were used as the only dataset in fitting the sulfate– N d relationship over land by BL95 , N d in January diagnosed using BL95 may have positive biases. In July, the convectively

Full access
Jingfeng Wang, Elfatih A. B. Eltahir, and Rafael L. Bras

mesoscale circulation under the conditions of idealized land surface heterogeneities. Mesoscale fluxes comparable to turbulent fluxes have been found using a linear model( Dalu and Pielke 1993 ). Nonlinear analysis of mesoscale circulations has been conducted with the help of numerical models. A good source of references on this topic can be found in a monograph by Pielke (1984) . The numerical simulations ( Pielke 1974 ; Mahrer and Pielke 1977 ; Segal et al. 1989 ; Huss and Feliks 1981 ; Ookouchi

Full access
Ning Zeng, J. David Neelin, and Chia Chou

; v s is the surface wind velocity; T s is the surface temperature (SST over ocean, ground temperature over land), q sat ( T s ) is the saturation humidity at T s ; T a and q a are the surface air temperature and humidity reconstructed using (2.1) and (2.2) , respectively; and C D and C H are a surface roughness–dependent drag coefficients and C D has a value of 1.0 × 10 −3 over ocean (see Table 3 for surface type–dependent parameter values). The current version of the model

Full access
Vince Agard and Kerry Emanuel

with a given storm. High CAPE is often associated with especially severe types of continental convection, such as supercells ( Emanuel 1994 ; Rasmussen and Blanchard 1998 ; Bluestein 2007 ). Recently, several authors have studied the behavior of continental CAPE in projected future climates using general circulation models. Trapp et al. (2007) and Del Genio et al. (2007) predict increases in CAPE in the eastern half of the United States and over land in general, respectively, under increased

Full access
Lawrence Greischar and Roland Stull

measurements from the Boundary Layer Field Experiment 1983 (BLX83) in Oklahoma (roughness length: 0.05 m; latitude: 35°N; vegetation: mixed pasture and crops; season: boreal spring). Data from another land-based experiment (Koorin) conducted under somewhat different conditions in Australia (roughness length: 0.4 m; latitude: 16°S; vegetation: uniform sparse trees; season: austral winter) were used to confirm the theory and the values of the coefficients. The objective of this paper is to test this theory

Full access
G. A. Dalu and R. A. Pielke

, using this or a similar theory.1. Introduction It has long been recognized that land and sea contrasts produce sea breezes (e.g., Pielke 1974). Morerecently, it has become evident that landscape variations that result in spatial gradients in surface heat fluxcan produce mesoscale circulations as strong as seabreezes (e.g., Ookouchi et al. 1984; Segal et al. 1988;Avissar and Pielke 1989); however, it remains to determine how small a horizontal variation in surfaceheating can still produce a

Full access
Robert G. Gallimore, Bette L. Otto-Bliesner, and John E. Kutzbach

resolution, spectral general circulation model (GCM) to specification of physicalprocesses is examined using a new version of the model with refined parameterizations. Specific refinements inparameterization include: 1) smoothing the original orography to greatly diminish undesirable topographic"ripples" occumng near high mountain ranges; 2) adding snowcover on the Tibetan plateau and representingwinter snowcover in middle latitudes more realistically; 3) decreasing the land ground wetness and

Full access
David C. Fritts, Robert C. Blanchard, and Lawrence Coy

date. The density fluctuations are interpreted interms of gravity wave motions and reveal significant density (and velocity) variance at horizontal scales rangingfrom ~ 10 to 1000 kin. Fluctuation amplitudes are used to infer corresponding velocity perturbations andcharacteristic vertical scales and frequencies of the wave spectrum. Results suggest that the mean velocityvariance is smaller over the Pacific ocean than observed over major land masses and that the variance increaseswith height in a

Full access
James E. Tillman, Lars Landberg, and Søren E. Larsen

November 1993) ABSTRACT Spectra of wind from high-frequency measurements in the Martian atmospheric surface layer, along with thediurnal variation of the height of the mixed surface layer, are calculated for the first time for Mars. Heat andmomentum fluxes, stability, and Zo are estimated for early spring from a surface temperature model and fromViking Lander 2 temperatures and winds at 44-N, using Monin-Obukhov similarity theory. Flow distortion bythe lander is also taken into

Full access
Ping Zhu, Bruce Albrecht, and Jon Gottschalck

1. Introduction Boundary layer clouds can form at the top of the mixed layer, and are frequently observed on the east side of the oceans, over polar regions, and over land in midlatitudes. Those over oceans, usually taking the form of stratus and stratocumulus, cover extensive areas, and can persist for a long time. Because of their high albedo and a cloud-top temperature similar to that of the underlying surface, these clouds have been widely recognized as an important factor in modulating the

Full access