Over the last few decades, some areas of Eurasia have experienced slight cooling or damped warming while other areas have seen substantial summer warming. The patterns of cooling and warming bear a marked resemblance to the spatial distribution of cloud cover change in this region. This finding, published in Environmental Research Letters (ERL) is based on a recent analysis of temperature, precipitation and satellite-derived cloud cover data.

Little is known about the physical processes responsible for the lack of significant summer warming in some regions of Eurasia but two immediate influencing factors – cloud cover and precipitation – may contribute to these surface temperature anomalies.

Clouds can cool the surface by decreasing the amount of solar radiation that reaches Earth, while precipitation can reduce temperatures by boosting daytime surface evaporative cooling. However, it is unclear whether these relatively immediate processes can affect more long-term trends. What's more, there is a strong correlation between precipitation and cloud cover and it is difficult to distinguish between the individual influence of these two parameters.

Satellites can provide uniformly sampled information about variations in cloud cover; data from these sources now span about 30 years. They provide a unique way to investigate the long-term relationship between cloud cover and temperature.

We used a partial least-squares regression approach to separate out the effects of cloud cover and precipitation. The analysis revealed that cloud cover may be the most important local factor influencing the summer temperature variation in Eurasia. Between 1982–2009, the extended western Siberia region experienced summer cooling or damped warming. Satellite data show that daytime cloud cover increased in western Siberia during the same period. Pronounced warming was observed in Europe and Mongolia while the data indicated that cloud cover decreased over these regions. We conclude that the interaction between daytime cloud cover and surface air temperature seems strong enough to influence decadal summer temperature trends.

Areas with strong cloud–temperature links span most of the continent, suggesting that cloud cover change may have an important influence on summer temperatures in other northern mid- to high latitudes. It will now be interesting to examine the role that cloud cover plays in North America.

About the author

Qiuhong Tang is a professor in the Land Surface Processes and Global Change Research Group at the Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences. Guoyong Leng is a PhD student working as a research assistant.

Source from: http://environmentalresearchweb.org/cws/article/news/49174