Spatial and temporal variations of vegetation surface albedo caused by snow in north China

<span class="hit">Albedo</span> is a key physics parameter <span class="hit">in</span> earth <span class="hit">surface</span>. It determines the ratio <span class="hit">of</span> solar energy absorbed <span class="hit">by</span> earth, and restricts the climate change between atmosphere and land <span class="hit">surface</span>. However, the uncertainty <span class="hit">of</span> <span class="hit">albedo</span> was not been considered sufficiently <span class="hit">in</span> most climate models, <span class="hit">snow</span> may be the most important source <span class="hit">of</span> this uncertainty. Season changes obviously <span class="hit">in</span> <span class="hit">north</span> <span class="hit">China</span>, which has different kinds <span class="hit">vegetation</span> types. Here we use the Moderate Resolution Imaging Spectroradiometer(MODIS) data to analysis the <span class="hit">spatial</span> and <span class="hit">temporal</span> effect <span class="hit">of</span> <span class="hit">albedo</span> change <span class="hit">caused</span> <span class="hit">by</span> <span class="hit">snow</span>. The result indicates that general distribution <span class="hit">of</span> <span class="hit">albedo</span> fallow the pattern <span class="hit">of</span> the <span class="hit">vegetation</span> cover type, have more heterogeneous under <span class="hit">snow</span> conditions. <span class="hit">Albedo</span> also have dramatic <span class="hit">temporal</span> various not only during the season change period, but also <span class="hit">in</span> the middle <span class="hit">of</span> winter

Human-Induced Landcover Changes Drive a Diminution of Land Surface Albedo in the Loess Plateau (China)

A large decrease in the land surface albedo of the Loess Plateau was observed from 2000 to 2010, as measured using satellite imagery. In particular, ecological restoration program regions experienced a decrease in peak season land surface albedo exceeding 0.05. In this study, we examined the spatial and temporal patterns of variation during the peak season albedo in the Loess Plateau and analyzed its relationships with changes of anthropogenic and natural factors at the pixel level. Our analysis revealed that increasing grassland coverage due to returning rangeland to grassland could lead to a maximum albedo decrease of 0.030 in peak season. This result highlighted the human-induced land use change in driving the decreasing albedo on an annual scale. There was no significant correlation between precipitation change and albedo reduction. Precipitation could influence the spatial pattern of albedo in drought years by influencing the natural vegetation water requirement. However, the role of precipitation was not obvious in the ecological restoration program regions. This article demonstrates the substantial role that land use change could play in regional-scale albedo change and climate. Finally, some implications for the radiative forcing of land use change are discussed

Different Patterns in Daytime and Nighttime Thermal Effects of Urbanization in Beijing-Tianjin-Hebei Urban Agglomeration

Surface urban heat island (SUHI) in the context of urbanization has gained much attention in recent decades; however, the seasonal variations of SUHI and their drivers are still not well documented. In this study, the Beijing-Tianjin-Hebei (BTH) urban agglomeration, one of the most typical areas experiencing drastic urbanization in China, was selected to study the SUHI intensity (SUHII) based on remotely sensed land surface temperature (LST) data. Pure and unchanged urban and rural pixels from 2000 to 2010 were chosen to avoid non-concurrency between land cover data and LST data and to estimate daytime and nighttime thermal effects of urbanization. Different patterns of the seasonal variations were found in daytime and nighttime SUHIIs. Specifically, the daytime SUHII in summer (4 °C) was more evident than in other seasons while a cold island phenomenon was found in winter; the nighttime SUHII was always positive and higher than the daytime one in all the seasons except summer. Moreover, we found the highest daytime SUHII in August, which is the growing peak stage of summer maize, while nighttime SUHII showed a trough in the same month. Seasonal variations of daytime SUHII showed higher significant correlations with the seasonal variations of ∆LAI (leaf area index) (R2 = 0.81, r = −0.90) compared with ∆albedo (R2 = 0.61, r = −0.78) and background daytime LST (R2 = 0.69, r = 0.83); moreover, agricultural practices (double-cropping system) played an important role in the seasonal variations of daytime SUHII. Seasonal variations of the nighttime SUHII did not show significant correlations with either of seasonal variations of ∆LAI, ∆albedo, and background nighttime LST, which implies different mechanisms in nighttime SUHII variation needing future studies