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Uri Dayan
and
Jean Koch

Abstract

This paper analyzes some measurements of the Southern California Air Quality Study, which collected a comprehensive air quality, meteorological, and emissions database in the Los Angeles Basin. This analysis emphasizes the interaction of the enriched ozone layer existing aloft with the top of the convective boundary layer (CBL) in the early afternoon of warm summer days, leading to downward mixing (fumigation) of the ozone cloud toward the ground. This process was shown to contribute to the high ozone concentrations measured at inland elevated sites. It is suggested that this mechanism also exists in Israel and contributes to the elevated concentrations observed in the summer on the slopes of the Judean Hills. This analogy is based on the similarity between the Los Angeles Basin and central Israel regarding the climate, the local circulation (sea breeze), the orientation of the coast, and the upwind location of ozone precursor sources. The temporal fluctuations of the synoptic configuration persisting over Israel during the summer cause rapid variations in the depth of the CBL inland and its subsequent interaction with an ozone layer aloft.

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Gavin A. Schmidt
,
Reto Ruedy
,
James E. Hansen
,
Igor Aleinov
,
Nadine Bell
,
Mike Bauer
,
Susanne Bauer
,
Brian Cairns
,
Vittorio Canuto
,
Ye Cheng
,
Anthony Del Genio
,
Greg Faluvegi
,
Andrew D. Friend
,
Tim M. Hall
,
Yongyun Hu
,
Max Kelley
,
Nancy Y. Kiang
,
Dorothy Koch
,
Andy A. Lacis
,
Jean Lerner
,
Ken K. Lo
,
Ron L. Miller
,
Larissa Nazarenko
,
Valdar Oinas
,
Jan Perlwitz
,
Judith Perlwitz
,
David Rind
,
Anastasia Romanou
,
Gary L. Russell
,
Makiko Sato
,
Drew T. Shindell
,
Peter H. Stone
,
Shan Sun
,
Nick Tausnev
,
Duane Thresher
, and
Mao-Sung Yao

Abstract

A full description of the ModelE version of the Goddard Institute for Space Studies (GISS) atmospheric general circulation model (GCM) and results are presented for present-day climate simulations (ca. 1979). This version is a complete rewrite of previous models incorporating numerous improvements in basic physics, the stratospheric circulation, and forcing fields. Notable changes include the following: the model top is now above the stratopause, the number of vertical layers has increased, a new cloud microphysical scheme is used, vegetation biophysics now incorporates a sensitivity to humidity, atmospheric turbulence is calculated over the whole column, and new land snow and lake schemes are introduced. The performance of the model using three configurations with different horizontal and vertical resolutions is compared to quality-controlled in situ data, remotely sensed and reanalysis products. Overall, significant improvements over previous models are seen, particularly in upper-atmosphere temperatures and winds, cloud heights, precipitation, and sea level pressure. Data–model comparisons continue, however, to highlight persistent problems in the marine stratocumulus regions.

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