Assessing the Influence of Precipitation on Diurnal Temperature Range Changes: Implications for Climate Change Projection

Abstract:

In this study, we investigate up to what extent the spatial heterogeneity in the projected changes in DTR during the rest of the 21st century (under several emission scenarios) is explained by the regional variability in projected precipitation changes. DTR is indeed a suitable index of climate variability and change [1] and several studies have highlighted the existence of a negative correlation with both the cloud cover and the precipitation rate over land throughout last century [2]. Precipitation reduces DTR mainly by decreasing surface solar radiation through increased cloud cover and by increasing daytime surface evaporative cooling through increased soil moisture content. Whether or not these processes are captured in the current generation of global and regional models is matter of research.

To achieve our objective, we make use of the climate projections made available by the CMIP5 project as well as their historical runs, along with reanalysis and station data. At inter-annual timescale, the seasonal mean DTR simulated by an ensemble of CMIP5 models for the last decades shows a negative relationship over land with the simulated precipitation at zero lag. The correlation is globally very strong except during winter at higher latitudes. This corresponds well with the correlations observed in the re-analysis datasets. Some spatial variability in correlation strength is however noticeable between both datasets.

Concerning the projected changes, the negative correlation between DTR and precipitation does not hold globally; no correlation or even positive correlations are observed in different climate regions, including Northern South America and Central Europe. Within this study we will further investigate the physical process that could explain this change in correlation sign as well as the reason why positive correlations are rarely observed or simulated at inter-annual timescale under current climate during summer and at lower latitudes during winter.

[1] K. Braganza, D.J. Karoly, and J.M. Arblaster. Diurnal temperature range as an index of global climate change during the twentieth century. Geophysical Research Letters, 31:1-4, 2004.

[2] A. Dai, A.D. Del Genio, and I.Y. Fung. Clouds, precipitation and temperature range. Nature, 386:665-666, 1997.