Asymmetric Trends of Daily Maximum and Minimum Temperature: Empirical Evidence and Possible Causes

THOMAS R. KARL1, PHILIP D. JONES2, RICHARD W. KNIGHT1, GEORGE KUKLA3, NEIL PLUMMER4, VYACHESLAV RAZUVAYEV5, KEVIN P. GALLO1, JANETTE A. LINDESAY6, AND ROBERT J. CHARLSON7

ABSTRACT

An examination of monthly maximum and minimum temperatures indicates that the rise of minimum temperature (0.84°C) has occurred at a rate three times that of rise of maximum temperature (0.28°C) over the period 1951 to 1990. This conclusion is based on data from over 50 percent (10 percent) of the Northern (Southern) Hemisphere land mass, accounting for 37 percent of the global land mass. The decrease of the diurnal temperature range is approximately equal to the increase of mean temperature. The asymmetry is detectable in all seasons in most of the regions studied.

The decrease in the daily temperature range is at least partially related to an observed increase in cloudiness. However, an empirical analysis of nearly 50,000 daily observations across 14 stations throughout the United States indicates that the daily temperature range is also sensitive to relative humidity, global radiation, surface stability, thermal advection, and snow cover; earlier work has shown that the temperature range is also sensitive to surface boundary conditions such as soil moisture. Locally, the diurnal range can also respond to increasing urbanization, irrigation, and desertification, but this effect appears to be small in our analysis.

Both general circulation models (GCMs) and radiative-convective models (RCMs) indicate that a decrease in the daily temperature range is likely with increases of CO2. The magnitude

1  

NOAA National Climatic Data Center, Asheville, North Carolina

2  

Climatic Research Unit, School of Environmental Sciences, University of East Anglia, Norwich, Norfolk, United Kingdom

3  

Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York

4  

Bureau of Meteorology, Melbourne, Australia

5  

Research Institute of Hydrometeorological Information, Obninsk, Russia

6  

Climate Research Group, University of Witswatersrand, South Africa

7  

Department of Atmospheric Sciences and Institute for Environmental Studies. University of Washington, Seattle, Washington



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